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National Boards => General Highway Talk => Topic started by: tradephoric on May 18, 2015, 02:51:37 PM

Title: Crash prone 'modern roundabouts'
Post by: tradephoric on May 18, 2015, 02:51:37 PM
In 2013, a modern roundabout was constructed at the intersection of Ellsworth & State in Ann Arbor, Michigan.  Three years prior to the roundabout construction, the intersection averaged 16 crashes per year.  The first year after the roundabout was completed, Ellsworth & State experienced the highest number of accidents in the entire state of Michigan (168 total crashes). 

Ann Arbor roundabout has most crashes in Michigan
http://www.mlive.com/news/ann-arbor/index.ssf/2015/03/roundabout_on_ann_arbors_south.html
http://www.semcog.org/Data-and-Maps/Crash-and-Road-Data/Point_Id/81016689/view/RoadIntersectionCrashDetail

Are there other crash prone modern roundabouts that you are aware of? 
Title: Re: Crash prone 'modern roundabouts'
Post by: froggie on May 18, 2015, 03:57:00 PM
Speaks more to the (in)flexibility of Michigan drivers than it does any inherent safety risk with roundabouts.  New roundabouts elsewhere have seen major drops in the number of crashes.
Title: Re: Crash prone 'modern roundabouts'
Post by: NE2 on May 18, 2015, 04:20:09 PM
PARCLO B4
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on May 18, 2015, 04:26:03 PM
Here it is: https://goo.gl/maps/NGJmj .  Is that a 'standard' roundabout?  You almost drive straight out of the roundabout, rather than curve out.  Plus that right turn only bypass comes out very close to the actual roundabout. 

I think there's a legit design issue here.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 18, 2015, 06:27:21 PM
Speaks more to the (in)flexibility of Michigan drivers than it does any inherent safety risk with roundabouts.  New roundabouts elsewhere have seen major drops in the number of crashes.

The safety statistics most often cited to the public are based on a 2000 study done by the Insurance Institute for Highway Safety.  A few points should be considered.  Of the 24 roundabouts analyzed, only 3 were previously signalized intersections (21 intersections were non-signalized).  Also, no roundabout had an AADT of greater than 31,000 vehicles.  The study observed that modern roundabouts have the following safety benefits:
-   38% reduction in total crashes
-   76% reduction in injury crashes
-   90% reduction in fatal and incapacitating-injury crashes

In 2011, the Wisconsin Department of Transportation funded a study that analyzed 24 roundabouts in their state.  In the Wisconsin study, a roundabout with an AADT of 70,000 was analyzed (over twice the traffic volumes of any roundabout included in the 2000 study).  Of the 24 roundabouts analyzed, 11 saw crashes increase after the roundabout was completed and 6 saw crashes increase by over 40%.   Overall, they observed the following safety benefits:
-   9% reduction in total crashes
-   52% reduction in injury crashes

Here is a summary of the roundabouts analyzed in the Wisconsin study:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Wisconsin_zpsgjcbnfpd.png)


Title: Re: Crash prone 'modern roundabouts'
Post by: Big John on May 18, 2015, 06:36:15 PM
^^ #7 STH 141?
WisDOT should know better than that. :pan:
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 18, 2015, 09:42:33 PM
^^ #7 STH 141?
WisDOT should know better than that. :pan:

Does traffic back up through the roundabout when a train goes by?

https://www.google.com/maps/@44.4588082,-87.950588,141m/data=!3m1!1e3
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 19, 2015, 02:38:26 AM
First year stats are such horse shit. Driver familiarity is a major preventer of collisions at intersections (drivers know what to expect; driver behavior, what each lane does, signal phases, etc). Changing literally anything will throw people off and you're probably gonna have a few additional collisions. I'll admit, that's a big jump, but I guarantee you tradephoric, the collisions will fall. Let's revisit this intersection in a couple years.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 19, 2015, 10:44:09 AM
First year stats are such horse shit. Driver familiarity is a major preventer of collisions at intersections (drivers know what to expect; driver behavior, what each lane does, signal phases, etc). Changing literally anything will throw people off and you're probably gonna have a few additional collisions. I'll admit, that's a big jump, but I guarantee you tradephoric, the collisions will fall. Let's revisit this intersection in a couple years.

Seeing a spike in crashes at SE Michigan roundabouts is not uncommon.  I touched on this in a previous thread.

The chart below looks at crash data of 16 major roundabouts built throughout SE Michigan between 2006-2009.  While PDO accidents spike the first year after roundabout construction, injury accidents drop from day one.  By year two people seem to get use to them and the PDO steadily declines from the initial spike.  This has at least been the trend for SE Michigan.
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBuntitled_zps758a2437.png)

If the crashes at Ellsworth & State jumped from 16 to 32, that would be par for the course.  However, it jumped from 16 to 168 crashes.  There’s a problem here.  To put this in perspective, the intersection with the 2nd most crashes in Michigan for 2014 had 87 crashes (12 Mile & Orchard Lake). 
Title: Re: Crash prone 'modern roundabouts'
Post by: Bickendan on May 19, 2015, 01:08:08 PM
Having glanced at the roundabout in question in Streetview, I don't see anything inherently wrong with the design. My gut says it's driver inflexibility and impatience, which will eventually largely evaporate as drivers get familiar with the design.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 19, 2015, 02:05:13 PM
Here are a list of roundabouts where total crashes have doubled since the completion of the roundabout (when averaging the 3 years before to 3 years after crash data).   To view the most up to date aerials you may have to input the coordinates into GE.  Do these roundabouts share any attributes that could explain the increase in crashes? 

(950%) Ellsworth Rd & State Rd (Ann Arbor, Michigan):
https://www.google.com/maps/@42.22941,-83.73873,17z/data=!3m1!1e3?dg=brw

(335%) Livernois Rd & Hamlin Rd (Rochester Hills, Michigan):
https://www.google.com/maps/@42.6518911,-83.1526542,137m/data=!3m1!1e3

(297%) Canal & 25th Street (Milwaulkee, Wicsonsin):
https://www.google.com/maps/@43.0311071,-87.9434376,92m/data=!3m1!1e3

(266%) SB US23 & Lee Road (Brighton, Michigan):
https://www.google.com/maps/@42.5059638,-83.759329,117m/data=!3m1!1e3

(135%) Cass Ave & Romeo Plank (Clinton, Michigan):
https://www.google.com/maps/@42.6113704,-82.9322543,117m/data=!3m1!1e3

(127%) STH 32/STH57 & Broadway (De Pere, Wisconsin):
https://www.google.com/maps/@44.4474383,-88.0602622,117m/data=!3m1!1e3
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on May 19, 2015, 02:06:38 PM
Having glanced at the roundabout in question in Streetview, I don't see anything inherently wrong with the design. My gut says it's driver inflexibility and impatience, which will eventually largely evaporate as drivers get familiar with the design.

But 3 years?   Usually familiarity takes a week for most drivers; maybe a month for more infrequent drivers.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 19, 2015, 02:27:06 PM
To jeffandnicole's point, in these studies no crash data is analyzed from the year the roundabout was constructed.  If a roundabout was completed in October, drivers have at least a few months to get use to before any crashes are included in the analysis.

For anyone interested, here's a link to the Wisconsin study:
http://www.topslab.wisc.edu/programs/safety/projects/roundabouts/WI%20Roundabout%20Evaluation%20Volume%202%20Safety.pdf


Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 19, 2015, 03:51:46 PM
For anyone interested, here's a link to the Wisconsin study:
http://www.topslab.wisc.edu/programs/safety/projects/roundabouts/WI%20Roundabout%20Evaluation%20Volume%202%20Safety.pdf

I'm sure it's in there, but I can't find it. Any idea what the common collisions were? (Like sideswipes, T-bone, etc).

Even if collisions are higher with roundabouts, I'm tempted to say that's preferable to, say, *consistent* fatal collisions. Have these roundabouts had fatal collisions? And were they contributed to driver error or a design fault? I ask that, because, roundabouts should work well -- their design is not the inherent cause of these collisions.
Title: Crash prone 'modern roundabouts'
Post by: 6a on May 19, 2015, 04:16:01 PM
Angle and sideswipe both had gigantic increases (at the Ann Arbor intersection). Like, those two accounted for almost all of the increase. I wonder if jeffandnicole is on to something regarding that right turn bypass bit. Looking at the crash increases it really does make me wonder if it's just people not staying in the correct lane. I'm not terribly familiar with the area - is this intersection near the university?

Closer to home here, I'm really curious to see what happens to this one, currently under construction:

(http://images.tapatalk-cdn.com/15/05/19/1bb12405f7a9e8b0cf49d995ebc3400d.jpg)

Traffic count sits at 50,000 currently, and even with left turns banned on the E-W route (SR 161) it's the third worst intersection for crashes in the city of Dublin. I believe it will be the first in the area to have a three lane section, but Dublin is the king of roundabouts locally, so like I said, I'm really curious to see the results.

Edit: oh wow, on that Ann Arbor one, you can see right across it. Could that be a cause for distraction?

(http://images.tapatalk-cdn.com/15/05/19/6e56d11a07db1e448e4e6bbf467d84b0.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 19, 2015, 04:30:23 PM
Edit: oh wow, on that Ann Arbor one, you can see right across it. Could that be a cause for distraction?

That's a very good point. One of the reasons the Carmel, Indiana roundabouts are so successful is because of their decoration.
Title: Re: Crash prone 'modern roundabouts'
Post by: johndoe on May 19, 2015, 07:40:29 PM
Cool thread, good info.  I wonder if this roundabout has tangents on entry and what the fastest path speeds are. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 19, 2015, 10:11:22 PM
For anyone interested, here's a link to the Wisconsin study:
http://www.topslab.wisc.edu/programs/safety/projects/roundabouts/WI%20Roundabout%20Evaluation%20Volume%202%20Safety.pdf

I'm sure it's in there, but I can't find it. Any idea what the common collisions were? (Like sideswipes, T-bone, etc).

Even if collisions are higher with roundabouts, I'm tempted to say that's preferable to, say, *consistent* fatal collisions. Have these roundabouts had fatal collisions? And were they contributed to driver error or a design fault?  I ask that, because, roundabouts should work well -- their design is not the inherent cause of these collisions.
 

Check out Table 4 on page 20.  There was big increases in sideswipe-same direction (SSS) crashes in the Wisconsin study (increasing from 10 in the before condition to 75 in the after).   



Title: Re: Crash prone 'modern roundabouts'
Post by: Brian556 on May 19, 2015, 10:35:24 PM
I said it before, I do not like multi-lane roundabouts. They are just too complicated, and can confuse drivers.  Only single-lane roundabouts should be allowed. Even single lane roundabouts can have issues, especially if drivers enter them too fast. Also, if there is too high of a volume of traffic entering from one direction, the other directions can have a hard time even getting a chance to enter the roundabout. The ones in Windermere, FL have this problem, particularly the southern one.
https://www.google.com/maps/place/Windermere,+FL/@28.4949864,-81.5342674,398m/data=!3m1!1e3!4m2!3m1!1s0x88e7635aece2fef1:0xfac6dfbac566065e (https://www.google.com/maps/place/Windermere,+FL/@28.4949864,-81.5342674,398m/data=!3m1!1e3!4m2!3m1!1s0x88e7635aece2fef1:0xfac6dfbac566065e)

There is a new one in Flower Mound, TX that I don't care for due to the rather high traffic volume. To me it's a pain in the ass having to deal with the high traffic volume, and trying to figure out when it is safe to enter the roundabout, especially from a stopped position. I'd personally rather have a signal at this particular location:
https://www.google.com/maps/@33.0664592,-97.0879309,95m/data=!3m1!1e3 (https://www.google.com/maps/@33.0664592,-97.0879309,95m/data=!3m1!1e3)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 19, 2015, 11:53:34 PM
I do not like multi-lane roundabouts. They are just too complicated, and can confuse drivers.

That is a gross over-generalization. There are plenty of multi-lane roundabouts (near me) that have zero issues.

In your defence, however, there are certainly areas in this country where the "courtesy" behaviour (necessary for a successful roundabout) doesn't exist. Texas springs to mind, along with much of the south and perhaps Midwest. Places like rural New England, the Pacific Northwest, and perhaps pockets of the Southwest are the best candidates for roundabouts, since they have the most courteous (and thus the most observant) drivers (at least in my experience).
Title: Re: Crash prone 'modern roundabouts'
Post by: renegade on May 20, 2015, 01:36:15 AM
Re:  State and Ellsworth in Ann Arbor:  It's a well-thought-out roundabout  Part of the problem is, northbound on State, there's a traffic signal which favors the side road about 150 yards north of the roundabout.  All the traffic-flow in the world is rendered useless if there's no place for it to go.  The other problem is that no one wants to learn to maneuver properly.  Some enter the roundabout without yielding to traffic already within, while others will gladly stop in the middle to let others in.  Hell, I personally witnessed on driver who said, "Fuck this" and turned left instead of going around.

Title: Re: Crash prone 'modern roundabouts'
Post by: KEK Inc. on May 20, 2015, 02:45:08 AM
I do not like multi-lane roundabouts. They are just too complicated, and can confuse drivers.

That is a gross over-generalization. There are plenty of multi-lane roundabouts (near me) that have zero issues.

In your defence, however, there are certainly areas in this country where the "courtesy" behaviour (necessary for a successful roundabout) doesn't exist. Texas springs to mind, along with much of the south and perhaps Midwest. Places like rural New England, the Pacific Northwest, and perhaps pockets of the Southwest are the best candidates for roundabouts, since they have the most courteous (and thus the most observant) drivers (at least in my experience).

I've run into dangerous congestion at these roundabouts when I went kayaking in Olympia last.

https://www.google.com/maps/place/Olympia,+WA/@47.0449015,-122.9119405,18z/data=!4m2!3m1!1s0x5491c9c1ae285569:0x4f146197e2881b83
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 20, 2015, 03:25:47 AM
I do not like multi-lane roundabouts. They are just too complicated, and can confuse drivers.

That is a gross over-generalization. There are plenty of multi-lane roundabouts (near me) that have zero issues.

In your defence, however, there are certainly areas in this country where the "courtesy" behaviour (necessary for a successful roundabout) doesn't exist. Texas springs to mind, along with much of the south and perhaps Midwest. Places like rural New England, the Pacific Northwest, and perhaps pockets of the Southwest are the best candidates for roundabouts, since they have the most courteous (and thus the most observant) drivers (at least in my experience).

I've run into dangerous congestion at these roundabouts when I went kayaking in Olympia last.

https://www.google.com/maps/place/Olympia,+WA/@47.0449015,-122.9119405,18z/data=!4m2!3m1!1s0x5491c9c1ae285569:0x4f146197e2881b83

I've gone through those a couple of times. Never had any issues, but the odd manner in which they facilitate through traffic would more than likely exacerbate traffic flow.

Any idea if Olympia publishes any stats on these roundabouts? The only documents I can find on the so-called "Gateway Project" (as it was called in 2003 -- how original) only seem to be promoting it, if you know what I mean.
Title: Re: Crash prone 'modern roundabouts'
Post by: KEK Inc. on May 20, 2015, 03:26:57 AM
I think they're a bit too close to each other.  I also went during rush hour.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 20, 2015, 03:38:09 AM
I think they're a bit too close to each other.  I also went during rush hour.

I'd rather have two closely spaced roundabouts than two closely spaced signals. Then again, they don't seem that close?
Title: Re: Crash prone 'modern roundabouts'
Post by: cpzilliacus on May 20, 2015, 03:34:14 PM
A roundabout in the municipality of Mount Rainier, Prince George's County, Maryland on U.S. 1 (Rhode Island Avenue) just north of the District of Columbia border at 34th Street. 

This roundabout (https://www.google.com/maps/place/Mt+Rainier,+MD/@38.936294,-76.960984,3a,26.4y,47.29h,81.51t/data=!3m4!1e1!3m2!1s469xw_VJTQOCuZtYSmrG7A!2e0!4m2!3m1!1s0x89b7c7a0d961e31f:0x38df1d15661676d1!6m1!1e1) features a rather massive concrete "planter" inside, which gets crashed into somewhat often by drunk/impaired drivers headed out of D.C.

I don't think it is poorly designed, and it improves Maryland traffic safety by "intercepting" some of those impaired motorists before they crash into something else, or a pedestrian or bicyclist.
Title: Re: Crash prone 'modern roundabouts'
Post by: Brian556 on May 20, 2015, 03:46:12 PM
Quote from cpzilliacus:
Quote
I don't think it is poorly designed, and it improves Maryland traffic safety by "intercepting" some of those impaired motorists before they crash into something else, or a pedestrian or bicyclist.

Now that gives me an idea. Create "drunk driver traps" by creating "hazards" that you would have to be drunk to drive into, to protect the general public.
I'm not necessarily advocating concrete planters, but something like a runway truck ramp with mud, and sign it "mud pit". Since drunk drivers can't even read DO NOT ENTER or WRONG WAY signs, they wouldn't read the "MUD PIT" sign either, and would drive right into it.
Title: Re: Crash prone 'modern roundabouts'
Post by: 6a on May 20, 2015, 03:52:13 PM

I think they're a bit too close to each other.  I also went during rush hour.

I'd rather have two closely spaced roundabouts than two closely spaced signals. Then again, they don't seem that close?

These work just fine. A bit slow at rush hour but compared to the old signals it's a big improvement.

(http://images.tapatalk-cdn.com/15/05/20/434e6b90f4e62f7968f4416834fa3ba0.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: froggie on May 20, 2015, 04:07:32 PM
The Wisconsin and Michigan experiences that tradephoric commented on are the general opposite of Minnesota's experience, at least anecdotally as I don't think MnDOT has done a comprehensive study yet.  They have studied a few roundabouts, including a rural roundabout in particular (on MN 13 in Scott County), built in response to multiple fatal crashes, where there were HUGE declines in overall crashes after the roundabout was completed.  There's also a study documenting a multilane roundabout in Richfield that did see a high number of crashes (there wasn't really anything to compare it to pre-construction), but after tweaking with signage and striping saw crashes and "illegal turns" (i.e. turning left from the outer lane) decrease by about half.  This Richfield study/research may hold the key to getting better results out of multilane roundabouts.

Title: Re: Crash prone 'modern roundabouts'
Post by: Sykotyk on May 20, 2015, 08:47:05 PM
I think there's two culprits: unfamiliarity of, and lack of obedience to the laws of traffic circles/roundabouts. So many drivers see the "Yield" sign as 'hurry up before the other guy gets there" rather than what it truly means, which is basically a stop sign that allows you to roll through if there's no side traffic. Not high speed. And it's not a race. And when traffic builds incredibly deep on more than one approach, the general rule of stop-signs take over and you take turns, rather than one road releasing everyone at once because tailgating through the yield and that stops everyone else from entering the traffic circle.

I've seen it in the northeast in the new smaller 'modern' ones. Funny the old ones up in Boston are handled fine. But make one about 100' diameter island in the middle, and suddenly it's a race to claim your spot in the middle.
Title: Re: Crash prone 'modern roundabouts'
Post by: roadfro on May 20, 2015, 10:15:02 PM
Here it is: https://goo.gl/maps/NGJmj .  Is that a 'standard' roundabout?  You almost drive straight out of the roundabout, rather than curve out.  Plus that right turn only bypass comes out very close to the actual roundabout. 

I think there's a legit design issue here.

I would agree with you. While it is designed to be a standard roundabout (as opposed to other traffic circles), it is lacking with some design features that can lead to issues.

The lack of deflection angles on the exits encourages circulating drivers to speed up while exiting, which I imagine contributes to collisions. In particular, the southbound exit point has no deflection at all.

The right turns also appear to be an issue. It looks like it easy to just turn right, without having to stop/yield, enter the circulatory area, then exit...instead sort of just not slowing and turning right since it looks like it's wide enough to just sneak by.

The southbound right turn bypass really just doesn't make sense. A right turn bypass lane in a roundabout only makes sense if it is free flowing. That seems like it might be a source of issues, and looks like it could be more angle accidents at that point instead of sideswipes. It also looks like that right turn would have visibly issues if there is also a car stopped in the lane adjacent to the "bypass" lane.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 20, 2015, 10:22:00 PM
I do not like multi-lane roundabouts. They are just too complicated, and can confuse drivers.

That is a gross over-generalization. There are plenty of multi-lane roundabouts (near me) that have zero issues.

Early findings of 5 multi-lane roundabouts in Washington State show that there has been a 56% increase in total crashes.  It’s not uncommon to see an increase in crashes at multi-lane roundabouts because drivers are exposed to a lot more sideswipe crashes.  The Washington State crash data is linked in this article below (click 'Early findings in Washington state'):

http://www.seattletimes.com/seattle-news/new-roundabout-aims-to-make-hwy-9-safer-in-growing-marysville/

Multi-lane roundabouts do a great job at reducing injury crashes but there is growing evidence that they don't reduce total crashes.  Single-lane roundabouts, OTOH, do a better job at reducing total crashes, but have less of an impact in reducing injury crashes.  This chart in the Wisconsin study illustrates these points.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/singlevsdouble_zps1r60v17i.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on May 20, 2015, 10:29:30 PM
As I've mentioned on other threads, Oregon's multi-lane roundabouts are absolutely terrible.  The one at US-101/OR-202 in Astoria has, over the long term, resulted in a 150% increase in crashes, without any reduction in accident severity, and even pro-roundabout traffic engineers I've talked to concur with the notion of that roundabout being terrible.  Given the wacky mess that was there before the roundabout, screwing things up that bad is quite a feat.  Of course, given that it was built by ODOT, I can't say I'm surprised, sadly.

Even worse is the one at MLK Pkwy, Pioneer Parkway, and Hayden Bridge Way in Springfield.  It cost almost $10 million to build, and it had almost 200 accidents between 2009 and 2013, with volumes only running 15,000-20,000 ADT.  The city's own transportation study showed it having an accident rate nearly 3 times that of the second-place intersection on a per MEV basis, but because it cost so much to build, they aren't rushing to fix it.

I think single-lane roundabouts do have a place--situations involving weird intersection geometry on mid-speed collectors and arterials (30-40mph range, and especially if people actually use their turn indicators)--but multi-lane roundabouts have had a very mixed record nationwide, and they're prohibitively expensive.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on May 20, 2015, 10:38:23 PM
I don't think anyone ever argued that roundabouts reduce collisions overall. What they argued was that, by reducing conflict points and angle of incidence (particularly head-on and T-bone collisions), they reduce the severity of the collisions that do occur, particularly compared to all-way stop and signalized intersections.

I also think some of the first-year collision issues are the result of insufficient public education efforts, particularly in areas with few existing roundabouts. Putting in place a temporary VMS on each leg 500 yards or so upstream that says "YIELD TO CIRCULATING TRAFFIC" for the first three months or so would do wonders.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 20, 2015, 11:15:39 PM
I don't think anyone ever argued that roundabouts reduce collisions overall. What they argued was that, by reducing conflict points and angle of incidence (particularly head-on and T-bone collisions), they reduce the severity of the collisions that do occur, particularly compared to all-way stop and signalized intersections.

That's exactly what's being argued though.  Listen to what Jeannie Willis has to say about the expected safety benefits of a 3-lane roundabout currently under construction in Dublin, Ohio (6A touched on this roundabout previously in this thread).  What are the residents of Dublin to think if her predictions don't come to pass?  At that point, who cares right?  It will already be constructed.

Not a valid vimeo URL
Quote
“They improve safety.  We will reduce crashes.  It won’t eliminate crashes.  The frequency of the crashes will be reduced and the severity will be reduced, of the crashes, meaning the number of injury related type crashes will be substantially reduced.”

-Jeannie Willis, Engineering Manager, City of Dublin
Title: Re: Crash prone 'modern roundabouts'
Post by: Bickendan on May 21, 2015, 12:35:51 AM
I don't think anyone ever argued that roundabouts reduce collisions overall. What they argued was that, by reducing conflict points and angle of incidence (particularly head-on and T-bone collisions), they reduce the severity of the collisions that do occur, particularly compared to all-way stop and signalized intersections.

That's exactly what's being argued though.  Listen to what Jeannie Willis has to say about the expected safety benefits of a 3-lane roundabout currently under construction in Dublin, Ohio (6A touched on this roundabout previously in this thread).  What are the residents of Dublin to think if her predictions don't come to pass?  At that point, who cares right?  It will already be constructed.
Uh... is this supposed to be a disagreement to what lordsutch said?
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on May 21, 2015, 12:47:34 AM
That's exactly what's being argued though.  Listen to what Jeannie Willis has to say about the expected safety benefits of a 3-lane roundabout currently under construction in Dublin, Ohio (6A touched on this roundabout previously in this thread).  What are the residents of Dublin to think if her predictions don't come to pass?  At that point, who cares right?  It will already be constructed.

Well, I can't speak for the specific roundabout being built; it's entirely possible that the existing intersection is so dangerous that it will reduce both the absolute frequency and severity of crashes (the data suggest some roundabouts do lead to less crashes than the intersections they replaced, and without systematically distinguishing between what the previous intersection type was it's hard to predict which will reduce crashes and which will lead to more crashes).

Assuming this is the intersection in question (https://www.google.com/maps/place/Dublin,+OH/@40.0995925,-83.1097332,250m/data=!3m1!1e3!4m2!3m1!1s0x8838ecc4d450a11f:0xc2176815689028!6m1!1e1), given the weird angle of the existing intersection I suspect the multilane roundabout will be an improvement on both scores.
Title: Re: Crash prone 'modern roundabouts'
Post by: Bickendan on May 21, 2015, 12:56:41 AM
That looks like the intersection in question. I didn't know Tim Horton's was on this side of the 48 though.
Title: Re: Crash prone 'modern roundabouts'
Post by: KEK Inc. on May 21, 2015, 02:31:15 AM
Speaking of bypass lanes, this sort of defeated the purpose of one.

https://www.google.com/maps/place/Sammamish,+WA/@47.56748,-122.054552,3a,88.7y,306.83h,90.46t/data=!3m4!1e1!3m2!1sZJeqqwehPIZI-Jr77sbkZg!2e0!4m2!3m1!1s0x549071edd8f91263:0xcd921b1280bf0b3a!6m1!1e1

Sometimes it's faster just to go in the roundabout.

---
The big danger of multi-lane roundabouts are that drivers not familiar with the area might notice they're in the wrong lane while in the circle and decide to make an illegal maneuver that may result in a collision.  Proper signage would be better.  I think WisDOT has an overhead mast arm with information on which lane to go to for their multi-lane roundabouts. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 21, 2015, 02:46:43 AM
I do not like multi-lane roundabouts. They are just too complicated, and can confuse drivers.

That is a gross over-generalization. There are plenty of multi-lane roundabouts (near me) that have zero issues.

Early findings of 5 multi-lane roundabouts in Washington State show that there has been a 56% increase in total crashes.  It’s not uncommon to see an increase in crashes at multi-lane roundabouts because drivers are exposed to a lot more sideswipe crashes.  The Washington State crash data is linked in this article below (click 'Early findings in Washington state'):

I wish that study included newer roundabouts. They stopped gathering data at two-thirds of those intersections ten years ago. That's hardly meaningful data.

Speaking of bypass lanes, this sort of defeated the purpose of one.
...
Sometimes it's faster just to go in the roundabout.

That one has always confused me. First, trucks aren't allowed through it (perhaps they should straighten the slip lane?) and now the slip-lane merge following the roundabout has had its merge area removed. I guess too many people failed to yield.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 21, 2015, 07:14:56 AM
I don't think anyone ever argued that roundabouts reduce collisions overall. What they argued was that, by reducing conflict points and angle of incidence (particularly head-on and T-bone collisions), they reduce the severity of the collisions that do occur, particularly compared to all-way stop and signalized intersections.

That's exactly what's being argued though.  Listen to what Jeannie Willis has to say about the expected safety benefits of a 3-lane roundabout currently under construction in Dublin, Ohio (6A touched on this roundabout previously in this thread).  What are the residents of Dublin to think if her predictions don't come to pass?  At that point, who cares right?  It will already be constructed.
Uh... is this supposed to be a disagreement to what lordsutch said?

Uh... Yes. 

Lordsutch said "I don't think anyone ever argued that roundabouts reduce collisions overall."  Jeannie Willis, the engineering manager for the City of Dublin, argued that "the frequency of the crashes will be reduced".
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on May 21, 2015, 08:13:00 AM
I'm pretty sure any road design that's created to increase accidents is, um, how should I put it...fucked up.

I'm pretty sure the design & intent of a roundabout is to reduce congestion.  They are also supposed to reduce accidents, and when accidents occur, they are less severe.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 21, 2015, 01:23:11 PM
Here are a list of roundabouts where total crashes have doubled since the completion of the roundabout (when averaging the 3 years before to 3 years after crash data).   To view the most up to date aerials you may have to input the coordinates into GE.  Do these roundabouts share any attributes that could explain the increase in crashes? 

(950%) Ellsworth Rd & State Rd (Ann Arbor, Michigan):
https://www.google.com/maps/@42.22941,-83.73873,17z/data=!3m1!1e3?dg=brw

(335%) Livernois Rd & Hamlin Rd (Rochester Hills, Michigan):
https://www.google.com/maps/@42.6518911,-83.1526542,137m/data=!3m1!1e3

(297%) Canal & 25th Street (Milwaulkee, Wicsonsin):
https://www.google.com/maps/@43.0311071,-87.9434376,92m/data=!3m1!1e3

(266%) SB US23 & Lee Road (Brighton, Michigan):
https://www.google.com/maps/@42.5059638,-83.759329,117m/data=!3m1!1e3

(135%) Cass Ave & Romeo Plank (Clinton, Michigan):
https://www.google.com/maps/@42.6113704,-82.9322543,117m/data=!3m1!1e3

(127%) STH 32/STH57 & Broadway (De Pere, Wisconsin):
https://www.google.com/maps/@44.4474383,-88.0602622,117m/data=!3m1!1e3


The central island diameter for all these roundabouts is 115 feet or less.  Are the increase in crashes due to the fact that the roundabouts are just too small?  I understand the whole idea of modern roundabouts is to slow down the speed of traffic, but if they are too tight drivers seem to have more difficulty with the following tasks....

A). judging gaps in traffic to enter the roundabout (leading to angle crashes).
B). physically staying in their lane while navigating through the roundabout (leading to sideswipe same crashes).

There are plenty of multi-lane roundabouts with central island diameters of over 150 feet (with entry and exit deflection angles to keep the speed of traffic down).  Could larger multi-lane roundabouts be more effective at reducing total crashes?  I'm thinking of a roundabout like this...

https://www.google.com/maps/@45.7550012,-108.6169408,162m/data=!3m1!1e3
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on May 21, 2015, 02:34:38 PM
This (https://www.google.com/maps/@51.602441,-0.631994,3a,70.4y,164.82h,69.89t/data=!3m4!1e1!3m2!1s-yrhCch_NuWYODXdEKPSiA!2e0) 10ft island diameter multi-lane roundabout doesn't see accidents. It does have traffic issues, but that is because of other factors (like not having a N-S bypass of the town, not enough space there) than because it is a roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on May 21, 2015, 02:45:51 PM
Here are a list of roundabouts where total crashes have doubled since the completion of the roundabout (when averaging the 3 years before to 3 years after crash data).   To view the most up to date aerials you may have to input the coordinates into GE.  Do these roundabouts share any attributes that could explain the increase in crashes? 

(950%) Ellsworth Rd & State Rd (Ann Arbor, Michigan):
https://www.google.com/maps/@42.22941,-83.73873,17z/data=!3m1!1e3?dg=brw

(335%) Livernois Rd & Hamlin Rd (Rochester Hills, Michigan):
https://www.google.com/maps/@42.6518911,-83.1526542,137m/data=!3m1!1e3

(297%) Canal & 25th Street (Milwaulkee, Wicsonsin):
https://www.google.com/maps/@43.0311071,-87.9434376,92m/data=!3m1!1e3

(266%) SB US23 & Lee Road (Brighton, Michigan):
https://www.google.com/maps/@42.5059638,-83.759329,117m/data=!3m1!1e3

(135%) Cass Ave & Romeo Plank (Clinton, Michigan):
https://www.google.com/maps/@42.6113704,-82.9322543,117m/data=!3m1!1e3

(127%) STH 32/STH57 & Broadway (De Pere, Wisconsin):
https://www.google.com/maps/@44.4474383,-88.0602622,117m/data=!3m1!1e3


The central island diameter for all these roundabouts is 115 feet or less.  Are the increase in crashes due to the fact that the roundabouts are just too small?  I understand the whole idea of modern roundabouts is to slow down the speed of traffic, but if they are too tight drivers seem to have more difficulty with the following tasks....

A). judging gaps in traffic to enter the roundabout (leading to angle crashes).
B). physically staying in their lane while navigating through the roundabout (leading to sideswipe same crashes).

There are plenty of multi-lane roundabouts with central island diameters of over 150 feet (with entry and exit deflection angles to keep the speed of traffic down).  Could larger multi-lane roundabouts be more effective at reducing total crashes?  I'm thinking of a roundabout like this...

https://www.google.com/maps/@45.7550012,-108.6169408,162m/data=!3m1!1e3

Many modern roundabouts have small diameter medians; with a slightly raised inner ring apron for large vehicles.  Most don't seem to have any issues with accidents.
Title: Re: Crash prone 'modern roundabouts'
Post by: Brandon on May 21, 2015, 04:03:46 PM
That looks like the intersection in question. I didn't know Tim Horton's was on this side of the 48 though.

48?  I think you mean 49th, and yes, they are on both side of the border.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 21, 2015, 09:29:52 PM
Another crash prone roundabout is at 14th Street & Superior in Lincoln, Nebraska.  This triple-lane roundabout was completed in November 2012.  In the first 11 months of operations, crashes quadrupled from 27.3 to 119.8.  In October 2013, the roundabout was converted to a two-lane roundabout.  Since the conversion, annualized crashes have dropped to 40.4 (which is still 47% higher than it was before the roundabout was constructed).  Here’s an article discussing the roundabout in greater detail:

https://lincoln.ne.gov/city/mayor/media/2014/050114.htm

I have my doubts that the triple-lane roundabout currently under construction in Dublin, Ohio will see a reduction in total crashes (even though this is what the engineering manager of Dublin is predicting). Instead of learning from others mistakes, the City will forge ahead and construct it as a triple-lane roundabout.  A year later, the City will be perplexed why there are so many crashes at the roundabouts and hire a consultant to perform a safety audit.  The consultant, after being handed a big bag of money, will come to the conclusion that the roundabout should be reconfigured to a two-lane roundabout to reduce the total number of crashes.

Here are other examples of triple-lane roundabouts that have recently been reconfigured to two-lane roundabouts (look at historical imagery to see the changes):
https://www.google.com/maps/@42.5417215,-83.4000249,139m/data=!3m1!1e3
https://www.google.com/maps/@42.5422709,-83.3803509,139m/data=!3m1!1e3
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 22, 2015, 12:43:36 AM
Another crash prone roundabout is at 14th Street & Superior in Lincoln, Nebraska.  This triple-lane roundabout was completed in November 2012.  In the first 11 months of operations, crashes quadrupled from 27.3 to 119.8.  In October 2013, the roundabout was converted to a two-lane roundabout.  Since the conversion, annualized crashes have dropped to 40.4 (which is still 47% higher than it was before the roundabout was constructed).

They only gave it 11 months? Jesus. So immediate top-tier performance or bust? I think crashes would drop over time, no need to act so hastily.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 22, 2015, 10:27:01 AM
Another crash prone roundabout is at 14th Street & Superior in Lincoln, Nebraska.  This triple-lane roundabout was completed in November 2012.  In the first 11 months of operations, crashes quadrupled from 27.3 to 119.8.  In October 2013, the roundabout was converted to a two-lane roundabout.  Since the conversion, annualized crashes have dropped to 40.4 (which is still 47% higher than it was before the roundabout was constructed).

They only gave it 11 months? Jesus. So immediate top-tier performance or bust? I think crashes would drop over time, no need to act so hastily.

I think roundabouts with three entry lanes are growing out of favor.  Roundabouts with three entry lanes were constructed as part of the US41 project in Wisconsin.  From my understanding, Wisconsin has no plans to design new roundabouts with three entry lanes moving forward.  DaBigE might have more information regarding this based on some posts I've read of his.

Here are some videos of crashes that occurred at Maple & Drake (before the roundabout was converted to two entry lanes).  This roundabout had three entry lanes for several years before it was converted to two entry lanes: 

Title: Re: Crash prone 'modern roundabouts'
Post by: triplemultiplex on May 22, 2015, 11:27:30 AM
(297%) Canal & 25th Street (Milwaulkee, Wicsonsin):
https://www.google.com/maps/@43.0311071,-87.9434376,92m/data=!3m1!1e3

I have to wonder if the number of collisions at this intersection where one or more operator was intoxicated is significantly higher.  It's an exit route for fans leaving Brewer games and for patrons dumping off money at the Potowatomi Casino.  Two situations where drinking is encouraged.
It is said that drunks are more prone to side-swipe collisions and roundabouts are purposefully designed so if there is a crash, it will be low-angle and hopefully non-injurious.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 22, 2015, 01:27:05 PM
(297%) Canal & 25th Street (Milwaulkee, Wicsonsin):
https://www.google.com/maps/@43.0311071,-87.9434376,92m/data=!3m1!1e3

I have to wonder if the number of collisions at this intersection where one or more operator was intoxicated is significantly higher.  It's an exit route for fans leaving Brewer games and for patrons dumping off money at the Potowatomi Casino.  Two situations where drinking is encouraged.
It is said that drunks are more prone to side-swipe collisions and roundabouts are purposefully designed so if there is a crash, it will be low-angle and hopefully non-injurious.

Maybe, maybe not.  Livernois & Hamlin looks pretty innocuous yet that multi-lane roundabout saw over a 300% increase in total crashes. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 22, 2015, 02:50:18 PM
Another crash prone roundabout is at 14th Street & Superior in Lincoln, Nebraska.  This triple-lane roundabout was completed in November 2012.  In the first 11 months of operations, crashes quadrupled from 27.3 to 119.8.  In October 2013, the roundabout was converted to a two-lane roundabout.  Since the conversion, annualized crashes have dropped to 40.4 (which is still 47% higher than it was before the roundabout was constructed).

They only gave it 11 months? Jesus. So immediate top-tier performance or bust? I think crashes would drop over time, no need to act so hastily.

I think roundabouts with three entry lanes are growing out of favor.  Roundabouts with three entry lanes were constructed as part of the US41 project in Wisconsin.  From my understanding, Wisconsin has no plans to design new roundabouts with three entry lanes moving forward.  DaBigE might have more information regarding this based on some posts I've read of his.

Here are some videos of crashes that occurred at Maple & Drake (before the roundabout was converted to two entry lanes).  This roundabout had three entry lanes for several years before it was converted to two entry lanes: 

I'm fine with reducing the amount of lanes at roundabouts, but only if it's related to "too much capacity" instead of uneducated drivers (Bloomington Hills for example). Basic math suggests that more collisions occur at three lane roundabouts because three lane roundabouts can process more cars.
Title: Re: Crash prone 'modern roundabouts'
Post by: Quillz on May 22, 2015, 03:04:24 PM
Speaks more to the (in)flexibility of Michigan drivers than it does any inherent safety risk with roundabouts.  New roundabouts elsewhere have seen major drops in the number of crashes.
Yup, I'm actually writing a paper on roundabouts right now and this has largely been my conclusion, too. Driver behavior (i.e. being unfamiliar with how roundabouts work) is the main cause of accidents within a roundabout. The design in of itself has been consistently shown to be safer than most traditional signalized or stop controlled intersections.
Title: Crash prone 'modern roundabouts'
Post by: 6a on May 22, 2015, 05:44:28 PM
That's exactly what's being argued though.  Listen to what Jeannie Willis has to say about the expected safety benefits of a 3-lane roundabout currently under construction in Dublin, Ohio (6A touched on this roundabout previously in this thread).  What are the residents of Dublin to think if her predictions don't come to pass?  At that point, who cares right?  It will already be constructed.

Well, I can't speak for the specific roundabout being built; it's entirely possible that the existing intersection is so dangerous that it will reduce both the absolute frequency and severity of crashes (the data suggest some roundabouts do lead to less crashes than the intersections they replaced, and without systematically distinguishing between what the previous intersection type was it's hard to predict which will reduce crashes and which will lead to more crashes).

Assuming this is the intersection in question (https://www.google.com/maps/place/Dublin,+OH/@40.0995925,-83.1097332,250m/data=!3m1!1e3!4m2!3m1!1s0x8838ecc4d450a11f:0xc2176815689028!6m1!1e1), given the weird angle of the existing intersection I suspect the multilane roundabout will be an improvement on both scores.

That is indeed the intersection. It's hard to tell from that view obviously, but SB traffic goes up a somewhat sharp incline immediately before the light. I've mentioned that left turns are banned on the E-W route, and even with that and the SB bypass road it's the third worst crash intersection in the city. That's why I said...


Uh... Yes. 

Lordsutch said "I don't think anyone ever argued that roundabouts reduce collisions overall."  Jeannie Willis, the engineering manager for the City of Dublin, argued that "the frequency of the crashes will be reduced".


Here are some videos of crashes that occurred at Maple & Drake (before the roundabout was converted to two entry lanes).  This roundabout had three entry lanes for several years before it was converted to two entry lanes.

...I really do wonder if that will be the case in this instance. Call me an eternal optimist on this one. However, with the area already being quite well educated in roundabouts and I can only assume the quirky hill at the intersection being addressed, can it really get worse than #3 in the city? (As I type this my curiosity is piqued as to what the others are and how that one relates. Off to the bowels of the Internet...)

In those videos it appears the problem in that layout is three *through* lanes. The Dublin one is only three lanes in a quarter of the design (the SB bypass is being retained.) but only two of those are through lanes. The innermost lane will be restricted to left-turning traffic. If the mockup I posted is correct as to striping, it would appear the problem of a driver in the inner lane trying to go straight is addressed. Of course we all know lines don't keep cars in their place, as Mr. FedEx learned in your last video.

So, time will tell I suppose. I do admit to a raised eyebrow when I first saw the design and, if anything, it should have enough traffic (and our eyes) from the beginning to judge whether this design is genius or garbage.

Edit: here is the current view SB (speed limit 45)
(http://images.tapatalk-cdn.com/15/05/22/d8bfe789db5b2d53ed14437bbd8a83d2.jpg)

And NB. Note each direction gets an exclusive green phase.
(http://images.tapatalk-cdn.com/15/05/22/8dc28705647388d26b246f122bc65bf9.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 22, 2015, 07:19:12 PM
I'm fine with reducing the amount of lanes at roundabouts, but only if it's related to "too much capacity" instead of uneducated drivers (Bloomington Hills for example). Basic math suggests that more collisions occur at three lane roundabouts because three lane roundabouts can process more cars.

Traffic volumes at 14th Street and Superior is down from the 2008 peak.  The 4 fold increase in crashes at this roundabout was not because more vehicles were navigating through the intersection.  Similarly, traffic volumes didn't drop overnight when the roundabout was converted from three lanes to two.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 22, 2015, 09:42:46 PM
I'm fine with reducing the amount of lanes at roundabouts, but only if it's related to "too much capacity" instead of uneducated drivers (Bloomington Hills for example). Basic math suggests that more collisions occur at three lane roundabouts because three lane roundabouts can process more cars.

Traffic volumes at 14th Street and Superior is down from the 2008 peak.  The 4 fold increase in crashes at this roundabout was not because more vehicles were navigating through the intersection.  Similarly, traffic volumes didn't drop overnight when the roundabout was converted from three lanes to two.

It's not pure volume. It's throughput. The intersection is pushing a whole bunch more cars through every second compared to a smaller roundabout. There's basically a higher likelihood of a collision because there's more cars that can collide. You can avoid this by making the roundabout smaller, but the intersection capacity is likewise reduced.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 22, 2015, 10:33:01 PM
It's not pure volume. It's throughput. The intersection is pushing a whole bunch more cars through every second compared to a smaller roundabout. There's basically a higher likelihood of a collision because there's more cars that can collide. You can avoid this by making the roundabout smaller, but the intersection capacity is likewise reduced.

I got what you're saying now Jake.  You make a good point.
Title: Re: Crash prone 'modern roundabouts'
Post by: colinstu on May 23, 2015, 10:02:50 AM
(297%) Canal & 25th Street (Milwaulkee, Wicsonsin):
https://www.google.com/maps/@43.0311071,-87.9434376,92m/data=!3m1!1e3

I have to wonder if the number of collisions at this intersection where one or more operator was intoxicated is significantly higher.  It's an exit route for fans leaving Brewer games and for patrons dumping off money at the Potowatomi Casino.  Two situations where drinking is encouraged.
It is said that drunks are more prone to side-swipe collisions and roundabouts are purposefully designed so if there is a crash, it will be low-angle and hopefully non-injurious.

Umm... guys? I don't know where that 297% number is coming from but check out historical aerial imagery in Google Earth.

An intersection didn't even EXIST in that location before the roundabout, it was a a curved thru-road with a dirt road going over train tracks coming off the middle of it for the heavy industry that was present in the valley.
Canal St didn't even exist between the Brewers Parking lots and 25th St.

It was that way up until 2005 when Canal St between those two locations began as well as the roundabout taking shape. It wasn't completed until 2006, and more people probably didn't figure out that completed road existed until even later.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 23, 2015, 11:05:47 AM
Umm... guys? I don't know where that 297% number is coming from but check out historical aerial imagery in Google Earth.

The number came from a study funded by the Wisconsin Department of Transportation.  Looking at the historical aerials, I wouldn’t have included 25th Street & Canal in the analysis since the geometry of the before and after conditions is quite a bit different.  Recently, a three entry leg roundabout was constructed in Michigan that has seen a significant increase in total crashes.  I haven’t mentioned the location of the roundabout in this thread since it added another leg to the intersection that wasn’t previously there (and analyzing the before and after crash data wouldn’t be fair IMO).

Am I surprised that the Wisconsin Department of Transportation funded a report that analyzed a roundabout with dissimilar before and after conditions?  No.  This is the same agency who designed these crash prone multi-lane roundabouts to begin with.  To be fair, several of the roundabouts included in the report have similar before and after conditions.  If you take out the results of the 25th Street & Canal roundabout, the remaining multi-lane roundabouts saw an overall increase in crashes. 
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on May 25, 2015, 01:52:02 AM
I think roundabouts with three entry lanes are growing out of favor.  Roundabouts with three entry lanes were constructed as part of the US41 project in Wisconsin.  From my understanding, Wisconsin has no plans to design new roundabouts with three entry lanes moving forward.  DaBigE might have more information regarding this based on some posts I've read of his.

As far as I know, we're designing the last roundabout in Wisconsin that will have 2, three-lane entries. Yes, Wisconsin does now have a phobia/moratorium of any additional roundabouts with three-lane entries (with the exception of one region). Other states seem to be sharing the trepidation as well. We've worked on a few three-lane designs for other states, but many have ended up being scaled back. In many cases, three lane entries aren't needed for a long time, and depending on the analysis software/skill of the analyst, may never be needed. Attempting to design for 20-year forecasts can be very tricky/dangerous, especially for new developments.

There is a growing belief that many roundabouts are being over-designed, which leads to larger than necessary designs. The problem in the US is lack of reliable data (number of years of available of data), and correction factors that vary depending on what portion of the country you're in. If you read the WisDOT FDM section on roundabout design (FDM 11-26 (http://roadwaystandards.dot.wi.gov/standards/fdm/11-26.pdf) if you're interested), Wisconsin uses it's own critical headways and follow-up headway values for capacity analysis.

There's also big debate over how to handle trucks (semis - WB-62s, WB-67s): should they stay in-lane, and if so, where? Just on the entry (aka Case II)? Throughout the roundabout movement (Case III)? Neither (Case I)? That can also lead to larger than necessary designs > faster operating speeds > more crashes.

Am I surprised that the Wisconsin Department of Transportation funded a report that analyzed a roundabout with dissimilar before and after conditions?  No.  This is the same agency who designed these crash prone multi-lane roundabouts to begin with.  To be fair, several of the roundabouts included in the report have similar before and after conditions.  If you take out the results of the 25th Street & Canal roundabout, the remaining multi-lane roundabouts saw an overall increase in crashes.

All I am going to say on this is there's a lot of flaws that can be found in WisDOT's roundabout crash studies (Phase III is set to be released later this summer).

The take-home message has been severe injury/fatal crashes have seen significant decreases. Fender-benders (aka PDO crashes) have gone up significantly in multilane roundabouts. Having read through many crash narratives, the majority have been attributed to failure to yield or improper lane usage). The stupid maneuvers people try to pull...it's almost so common it ceases to amaze me any more.
Title: Re: Crash prone 'modern roundabouts'
Post by: froggie on May 25, 2015, 12:18:13 PM
DaBigE (and tradephoric too for that matter), have you looked into the research MnDOT completed last year on signage and striping with multilane roundabouts?  This is just one study of one multilane roundabout, but they found tweaking signage and striping led to significant decreases in the number of crashes caused by yield failures and improper lane usage:

http://www.dot.state.mn.us/research/TS/2014/201404TS.pdf (summary)

http://www.dot.state.mn.us/research/TS/2014/201404.pdf (study)
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on May 25, 2015, 11:48:50 PM
DaBigE (and tradephoric too for that matter), have you looked into the research MnDOT completed last year on signage and striping with multilane roundabouts?  This is just one study of one multilane roundabout, but they found tweaking signage and striping led to significant decreases in the number of crashes caused by yield failures and improper lane usage:

http://www.dot.state.mn.us/research/TS/2014/201404TS.pdf (summary)

http://www.dot.state.mn.us/research/TS/2014/201404.pdf (study)

Yes, I am fairly familiar with that study. My biggest issue with the study is that it's impossible to tell what had the most effect on driver behavior since they implemented two relatively significant changes at the same time. My gut says it was the change in signing, based driver observations on obeying markings as well as changes Madison, WI made to this roundabout (https://www.google.com/maps/@43.1212745,-89.2990561,191m/data=!3m1!1e3), after it was in the top 5 worst intersections in the city for crashes for several years. It has since dropped off the radar/top ten. Several signs were added; no pavement markings were changed. Unfortunately Google StreetView doesn't show them, but the city added a few lane reminder signs in the outside corners (one significant problem was crossing crashes at the exits), as well as a standard NO RIGHT TURN with a LEFT LANE plaque on the eastbound approach. Similar to my roundabout size comment, many [designers] think this roundabout is sized a bit too large, as speeds are quite high.

What's interesting about that MnDOT study is many of the changes they implemented closely mimic WisDOT standards for roundabout signing/marking (although we tend to favor overhead signing when possible, rather than ground-mount). I've worked on a couple Minnesota roundabouts and trying to implement overhead signs is a PITA.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 26, 2015, 01:26:22 AM
Not sure what kind of signing might be helpful, but two additions that I think we could adopt from the UK:

1) Pavers indicating movement direction:

(http://www.mss-concrete.co.uk/mm/concrete-stone-cutting.jpg)

2) larger chevrons indicating movement direction:

(http://www.sabre-roads.org.uk/wiki/images/2/23/A9_Tore_Roundabout_-_Chevrons.jpg)

While I'm not entirely certain how relevant left turns are at roundabouts these days (most studies, which I'm sure cover the stats, confuse me to no end), I would think these practices would put a stop to it. I know number 1 has been used before (couldn't quote any examples, I'm just certain I've seen it) but number 2, while we use chevrons, I don't think we've ever used it to such an extent. Perhaps while we're at it, we ought to bring back the circular one-way sign.

DaBigE, despite my suggestions above, do you think there is such a thing as signage overload? If so, do you think it holds some relevance to this here conversation?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 26, 2015, 11:56:11 AM
There's also big debate over how to handle trucks (semis - WB-62s, WB-67s): should they stay in-lane, and if so, where? Just on the entry (aka Case II)? Throughout the roundabout movement (Case III)? Neither (Case I)? That can also lead to larger than necessary designs > faster operating speeds > more crashes.

I’m very interested in this comment DaBigE.  Assuming there is an adequate entry deflection angle to slow the speed of traffic, wouldn’t larger roundabouts potentially result in fewer crashes and not more crashes?  With larger roundabouts, it’s easier to physically stay in your lane (likely resulting in fewer side-swipe crashes).  In addition, drivers might be able to judge available gaps in traffic better, since there is greater distance between legs.  With smaller roundabouts, entering drivers seem to be guessing what circulating vehicles intent is (since there isn’t as much distance between legs).   

The multi-lane roundabouts in SE Michigan that have seen significant increase in total crashes all seem to have smaller footprints (IE. central island diameters of 100 feet or less).  The roundabout at Ellsworth & State (that saw nearly a 10x increase in crashes) has a central island diameter of 100 feet.  Conversely, there are several examples of larger roundabouts in SE Michigan with central island diameters of greater than 150 feet that haven’t seen significant increases in crashes (with some seeing significant crash reductions).
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on May 26, 2015, 07:05:03 PM
There's also big debate over how to handle trucks (semis - WB-62s, WB-67s): should they stay in-lane, and if so, where? Just on the entry (aka Case II)? Throughout the roundabout movement (Case III)? Neither (Case I)? That can also lead to larger than necessary designs > faster operating speeds > more crashes.

I’m very interested in this comment DaBigE.  Assuming there is an adequate entry deflection angle to slow the speed of traffic, wouldn’t larger roundabouts potentially result in fewer crashes and not more crashes?  With larger roundabouts, it’s easier to physically stay in your lane (likely resulting in fewer side-swipe crashes).  In addition, drivers might be able to judge available gaps in traffic better, since there is greater distance between legs.  With smaller roundabouts, entering drivers seem to be guessing what circulating vehicles intent is (since there isn’t as much distance between legs).

While the amount of deflection is important, where and how the deflection ties into the circulatory is just as/more important. Many of the designs I've seen implemented lately are what we refer to as "hockey stick" designs... where the R1 entry curve that is too far upstream which results in a very flat entry at the circulatory (long tangent). These long tangents allow drivers to accelerate as they approach the yield point where they instead should be slowing down. Combine that with a larger roundabout diameter (ICD*), the faster the vehicle speeds though the roundabout (R1 & R2 speeds). The larger roundabouts may work safer when circulating volumes are higher or when the roundabout is operating closer to its capacity. However, the majority of crash reports I've seen occur during the off-peak times. During off-peak times, you might as well not paint any lines, as drivers tend to follow the fast-path though the roundabout. The faster the roundabout operates, the more willing drivers are to take smaller gaps, and crash doing so because they misjudged the speed of the circulating vehicle.

This is not to say that small roundabouts are the best. Like Goldilocks, there is a "just right" size. The general consensus regarding ICD is an inverse relationship between size and safety due to the direct relationship between size and speed.

The multi-lane roundabouts in SE Michigan that have seen significant increase in total crashes all seem to have smaller footprints (IE. central island diameters of 100 feet or less).  The roundabout at Ellsworth & State (that saw nearly a 10x increase in crashes) has a central island diameter of 100 feet.  Conversely, there are several examples of larger roundabouts in SE Michigan with central island diameters of greater than 150 feet that haven’t seen significant increases in crashes (with some seeing significant crash reductions).

A central island diameter of 100-feet is way to small even for a single lane roundabout. A typical minimum ICD for a multilane roundabout is approximately 160-feet. Assuming approximately 28-feet of pavement for the circulatory, that would net you a central island of 132-feet 104-feet (truck apron inclusive).

*NOTE: designers generally refer to the size of the roundabout based on the diameter to the face of the outside curb of the circulatory, or the inscribed circle diameter

**Edited to correct math error
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on May 26, 2015, 07:30:38 PM
DaBigE, despite my suggestions above, do you think there is such a thing as signage overload? If so, do you think it holds some relevance to this here conversation?

YES. That is precisely why there is minimum recommended spacing between signs in general and maximum recommended amounts of legend in a guide sign. I cringe a little every time I have to deal with an intersection of more than two or three routes. Post too many signs, and drivers will ignore them. This is why I don't like the Ped Xing sign being posted at every. single. crosswalk. For every sign you post, there is a perception-reaction time associated with it. Despite what some think, posting another sign will not correct an overall design flaw or lack of education.

I am a firm believer in less is more - to a point. The key is getting the important information to the driver at the right time. That is why I personally prefer overhead lane signage to post-mounted, especially in urban areas. Getting drivers into the appropriate lane early when approaching a roundabout is critical.

Not sure what kind of signing might be helpful, but two additions that I think we could adopt from the UK:

1) Pavers indicating movement direction:

(http://www.mss-concrete.co.uk/mm/concrete-stone-cutting.jpg)

This has been tried once or twice before, and the end result was a PITA to install and maintain. It's too subtle for many US drivers to comprehend. With so many central islands being used for public artwork, many think it's just part of the design. IMO, it's a waste of money.

Quote
2) larger chevrons indicating movement direction:

(http://www.sabre-roads.org.uk/wiki/images/2/23/A9_Tore_Roundabout_-_Chevrons.jpg)

In my experiences, wrong-way movements with regards to a roundabout appears to be a shrinking problem. Referencing the discussion with tradephoric, properly executed deflection should render these signs virtually useless. Improper yielding is the biggest concern, which is why WisDOT uses the plaque TO TRAFFIC FROM LEFT, with other states and municipalities using variants of that.

Perhaps while we're at it, we ought to bring back the circular one-way sign.

Testing may prove me wrong, but I don't think another style of sign is going to gain compliance. Only a vehicle with lights and siren seem to work.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 26, 2015, 10:05:53 PM
A central island diameter of 100-feet is way to small even for a single lane roundabout. A typical minimum ICD for a multilane roundabout is approximately 160-feet. Assuming approximately 28-feet of pavement for the circulatory, that would net you a central island of 132-feet (truck apron inclusive).

The top 5 highest crash frequency intersections in Oshkosh, Wisconsin are at multi-lane roundabouts with central island diameters of 100 feet or less.  Here is a table of the Oshkosh roundabouts with the construction year highlighted in yellow:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Oshkosh%20rank_zps1dessqqv.png)
http://www2.ci.oshkosh.wi.us/WebLink8/0/doc/711055/Electronic.aspx

I’m starting to see a theme...  multi-lane roundabouts with central island diameters of 100 feet or less have high crash frequencies (especially at roundabouts with high AADT).  Nearly every roundabout cited in this thread (apart from the triple lane roundabout from Lincoln, Nebreska) has had a central island diameter of roughly 100 feet.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on May 26, 2015, 10:35:31 PM
A central island diameter of 100-feet is way to small even for a single lane roundabout. A typical minimum ICD for a multilane roundabout is approximately 160-feet. Assuming approximately 28-feet of pavement for the circulatory, that would net you a central island of 132-feet (truck apron inclusive).

The top 5 highest crash frequency intersections in Oshkosh, Wisconsin are at multi-lane roundabouts with central island diameters of 100 feet or less.  Here is a table of the Oshkosh roundabouts with the construction year highlighted in yellow:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Oshkosh%20rank_zps1dessqqv.png)
http://www2.ci.oshkosh.wi.us/WebLink8/0/doc/711055/Electronic.aspx

I’m starting to see a theme...  multi-lane roundabouts with central island diameters of 100 feet or less have high crash frequencies (especially at roundabouts with high AADT).

It would probably be fair to see a longer list, which will show both 100' diameter roundabouts that don't have high crash frequencies, and roundabouts with larger diameters and how they rank. 
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on May 26, 2015, 11:28:07 PM
A central island diameter of 100-feet is way to small even for a single lane roundabout. A typical minimum ICD for a multilane roundabout is approximately 160-feet. Assuming approximately 28-feet of pavement for the circulatory, that would net you a central island of 132-feet (truck apron inclusive).

The top 5 highest crash frequency intersections in Oshkosh, Wisconsin are at multi-lane roundabouts with central island diameters of 100 feet or less.  Here is a table of the Oshkosh roundabouts with the construction year highlighted in yellow:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Oshkosh%20rank_zps1dessqqv.png)
http://www2.ci.oshkosh.wi.us/WebLink8/0/doc/711055/Electronic.aspx

I’m starting to see a theme...  multi-lane roundabouts with central island diameters of 100 feet or less have high crash frequencies (especially at roundabouts with high AADT).  Nearly every roundabout cited in this thread (apart from the triple lane roundabout from Lincoln, Nebreska) has had a central island diameter of roughly 100 feet.

And after correcting my math error (forgot I was working with a diameter, not a radius :pan:), the 100-foot central island falls right at the prescribed minimum for a multilane roundabout size - at least according to WisDOT and NCHRP Report 679. In fact, Report 679 suggests a minimum ICD as low as 150-feet. IIRC, Europe has even more compact roundabouts, yet not nearly the crash problem.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on May 26, 2015, 11:45:23 PM
A central island diameter of 100-feet is way to small even for a single lane roundabout. A typical minimum ICD for a multilane roundabout is approximately 160-feet. Assuming approximately 28-feet of pavement for the circulatory, that would net you a central island of 132-feet (truck apron inclusive).

The top 5 highest crash frequency intersections in Oshkosh, Wisconsin are at multi-lane roundabouts with central island diameters of 100 feet or less.  Here is a table of the Oshkosh roundabouts with the construction year highlighted in yellow:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Oshkosh%20rank_zps1dessqqv.png)
http://www2.ci.oshkosh.wi.us/WebLink8/0/doc/711055/Electronic.aspx

I’m starting to see a theme...  multi-lane roundabouts with central island diameters of 100 feet or less have high crash frequencies (especially at roundabouts with high AADT).

It would probably be fair to see a longer list, which will show both 100' diameter roundabouts that don't have high crash frequencies, and roundabouts with larger diameters and how they rank.

It would also be valuable to note that Washburn & 9th, Koeller & 9th are part of a corridor of 4 closely-spaced roundabouts. Frankly, I'm surprised to not see the roundabouts at Wis 21/I-41/Washburn/Koeller appear high on the list, as those are also similarly designed roundabouts, a few with 3-lane entries. Maybe they show up further down on the list...can't tell right now because I get a server error when attempting to use the link tradephoric provided. However, IIRC, Wis 21 wasn't opened until 2012 or early 2013.

Does anyone have crash data for Carmel, Indiana?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 27, 2015, 03:05:59 PM
It would probably be fair to see a longer list, which will show both 100' diameter roundabouts that don't have high crash frequencies, and roundabouts with larger diameters and how they rank. 

Here is a list of 40 multi-lane roundabouts that I think could be meaningful to this conversation.  This was queried from a database of over 5,100 modern roundabouts.  This was the criteria used to query out the list:

-roundabouts constructed within the last 10 years
-all approaches have 2 entry lanes
-roundabouts have 4-legs
-main & side streets are major state or county routes (ie. likely high AADT roundabouts)
-interchange roundabouts (and frontage road roundabouts) not included

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBtest_zpsbkjmf4ri.png)

Now the hard part is finding accurate before/after crash data to make any type of analysis.  Here is a google KMZ file that includes the 40 roundabouts in the chart above:

http://www.mediafire.com/download/cd570rarros2c3g/Multi-Lane+Roundabouts+%28with+high+AADT%29.kmz

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 27, 2015, 04:49:38 PM
Crashes up at multi-lane roundabout in Cheyenne, Wyoming:

http://www.wyomingnews.com/articles/2014/08/15/news/19local_08-15-14.txt#.VWYsqEYmlBI
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 27, 2015, 04:50:41 PM
Three of Madison's most crash prone intersections are roundabouts:

http://www.channel3000.com/news/Three-of-Madison-s-most-crash-prone-intersections-are-roundabouts/16170598
Title: Re: Crash prone 'modern roundabouts'
Post by: colinstu on May 27, 2015, 05:08:07 PM
I think one important factor that needs to be considered is the severity of the crashes, not the number of them. Assigning weights to different kinds of crashes to how commonly they occur to more accurately compare them. What also needs to be considered are traffic counts. If traffic at the intersection doubles... Well no doubt there will be more collisions. All these variables need to be leveled out to make any kind of meaningful comparison.

Roundabouts (properly designed) vs 4-way intersection aren't going to have head-on or t-bone collisions. While they may have more fender benders (and thus more "crashes") ... The severity of those (and risk of injury / death) is much lower. I'd rather have more safe accidents then less deadly accidents.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on May 27, 2015, 05:26:35 PM
Three of Madison's most crash prone intersections are roundabouts:

http://www.channel3000.com/news/Three-of-Madison-s-most-crash-prone-intersections-are-roundabouts/16170598

That article is from 3 years ago. Virtually all of Madison's roundabouts are out of the top ten list in the report from last year.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on May 27, 2015, 05:32:36 PM
I'd rather have more safe accidents then less deadly accidents.
Stannis the mannis isn't happy! (sorry, images are small)
(https://s-media-cache-ak0.pinimg.com/236x/17/e1/8b/17e18b76f82272bc6d5d78bcec056a84.jpg)
(https://scontent.cdninstagram.com/hphotos-xaf1/t51.2885-15/s320x320/e15/11226885_818816364855265_1929643643_n.jpg)
"more safe" is "less deadly".

I think you meant that you'd rather have more, but safer, accidents than fewer, but deadlier, accidents.
Title: Re: Crash prone 'modern roundabouts'
Post by: colinstu on May 27, 2015, 05:35:24 PM
Yup that's what I mean. Phrasing. Figure it out. :P
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 27, 2015, 05:58:39 PM
Three of Madison's most crash prone intersections are roundabouts:

http://www.channel3000.com/news/Three-of-Madison-s-most-crash-prone-intersections-are-roundabouts/16170598

That article is from 3 years ago. Virtually all of Madison's roundabouts are out of the top ten list in the report from last year.

According to the article, none of the intersections were in the top 25 list before they were converted to roundabouts though.  I think the crash results are meaningful.  Keep in mind, this is around the time Rep. Craig introduced a bi-partison bill that would give more control to local communities to what roundabouts get built and less control to Madison bureaucrats.  Did the early crash results from Madison and Oshkosh play a part in that?  I think the public takes notice (and voice concerns to their elected officials) when they read articles stating that crashes have spiked after the completion of a roundabout. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 27, 2015, 07:49:36 PM
Excerpts from an article discussing New Berlin interchange roundabouts (http://www.newberlinnow.com/news/56607067.html):

Quote
In fact, new figures from the city show that drivers were more likely to have a crash in the Moorland Road/Rock Ridge roundabout last year than at any other major intersection in New Berlin.  There were 2.08 crashes per 1 million vehicles through the intersection, the highest crash rate among the top 25 New Berlin intersections in 2008.

^This double-lane roundabout has a central island diameter of 120 feet.

Quote
New Berlin's other roundabout, at Moorland Road and Interstate 43, had the third highest crash rate with 1.43 crashes per 1 million vehicles.

^This triple-lane roundabout has a central island diameter of 190 feet

The roundabout with the larger central island diameter has a lower crash frequency (1.43 crashes per 1 million vehicles vs. 2.08 crashes per 1 million vehicles).  Are bigger roundabouts better at lowering crash frequency?
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on May 28, 2015, 05:30:32 AM
The roundabout with the larger central island diameter has a lower crash frequency (1.43 crashes per 1 million vehicles vs. 2.08 crashes per 1 million vehicles).  Are bigger roundabouts better at lowering crash frequency?
Depends - there comes a point where circulating traffic is going too fast and needs to be slowed down for safety and capacity's sake.

And of course, crashes are more likely to be severe on bigger islands due to the faster speeds. Still better than a signalised crossroads for that though.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on May 28, 2015, 09:45:56 AM
Three of Madison's most crash prone intersections are roundabouts:

http://www.channel3000.com/news/Three-of-Madison-s-most-crash-prone-intersections-are-roundabouts/16170598

That article is from 3 years ago. Virtually all of Madison's roundabouts are out of the top ten list in the report from last year.

According to the article, none of the intersections were in the top 25 list before they were converted to roundabouts though.  I think the crash results are meaningful.  Keep in mind, this is around the time Rep. Craig introduced a bi-partison bill that would give more control to local communities to what roundabouts get built and less control to Madison bureaucrats.  Did the early crash results from Madison and Oshkosh play a part in that?  I think the public takes notice (and voice concerns to their elected officials) when they read articles stating that crashes have spiked after the completion of a roundabout.

Yes, the crash results are meaningful, all crash results are meaningful...especially more recent ones showing roundabouts are becoming safer (two roundabouts remained on the top-ten list for Madison, at least as of the 2013 data, but dropped in position): 2013 Madison Police Report (https://www.cityofmadison.com/police/documents/10MostDangerousIntersections2013.pdf), Madison.com 2014 News Story (http://host.madison.com/news/local/crime_and_courts/madison-s-worst-intersections-east-washington-and-stoughton-road-tops/article_c0acda33-4112-5cce-9eeb-1ed2d8edb19e.html). As both suggest, failure to yield and improper turn/lane usage top the list of reasons - two items that are not directly correlated with the size of the roundabout, but rather driver behavior. Two of the biggest prior offenders - the pair on Thompson Dr, dropped off the list after residing there for several years.

As for the failed legislation, when did adding more bureaucracy ever solve anything? Intersection projects are approved by the DOT, not by the legislators, however, they can persuade the DOT to increase the priority of a project. Many of the roundabouts that have been constructed (albeit mostly of the single-lane variety) have been for serious crash injury issues, which the roundabouts have largely cured. Locals already get a say and I know of at least a dozen projects that were changed because of local input. It doesn't help when people don't follow the process and decide to complain after the comment periods have passed. While I'm sure the crash records had some impact, the bigger reason is there still is a large hatred of all roundabouts, many times without logical reasoning. The funny thing is, survey after survey continues to show the tables completely turning after a roundabout has been opened to traffic, with the number of those not liking the roundabouts shrinking dramatically.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 28, 2015, 11:30:46 AM
Thank you for the links to the Madison crash reports DaBigE.  Unfortunately, the reports only include the top 30 crash prone intersections and neither Lien & Thompson, County Rd M & Valley View Rd, or Mineral Point & Valley View Rd were in the top 30 in the 2009 or 2010 reports.  Since they weren’t in the top 30, let’s assume then that intersections averaged 8 crashes per year before the roundabouts were constructed (which was how many crashes the #30 most crash prone intersection experienced in both the 2009 & 2010 crash reports).  What happened since the multi-lane roundabouts were constructed in Madison?

Lien Rd & Thomson Dr: constructed in 2010.  In 2011, it was the #1 most crash prone intersection in the region with 23 crashes.   Couldn’t find crash data from 2012 or 2013. 

County Rd M & Valley View Rd: constructed in 2010.  In 2011, it was the #3 most crash prone intersection in the region with 18 crashes.  In 2012 the crashes rose to 22 and in 2013 crashes rose to 25. 

Mineral Point & Pleasant View Rd: constructed in 2011.  In 2012, it was the #1 most crash prone intersection in the region with 46 crashes.  In 2013 crashes dropped to 30.

DaBigE, do you know where County Rd M & Valley View Rd currently stands in the ranking of most crash prone intersections in Madison?  The total number of crashes seem to be increasing year over year at this roundabout. 
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on May 28, 2015, 11:59:09 AM
Thank you for the links to the Madison crash reports DaBigE.  Unfortunately, the reports only include the top 30 crash prone intersections and neither Lien & Thompson, County Rd M & Valley View Rd, and Mineral Point & Valley View Rd were in the top 30 in the 2009 or 2010 reports.  Since they weren’t in the top 30, let’s assume then that intersections averaged 8 crashes per year before the roundabouts were constructed (which was how many crashes the #30 most crash prone intersection experienced in both the 2009 & 2010 crash reports).  What happened since the multi-lane roundabouts were constructed in Madison?

Lien Rd & Thomson Dr: constructed in 2010.  In 2011, it was the #1 most crash prone intersection in the region with 23 crashes.   Couldn’t find crash data from 2012 or 2013. 

County Rd M & Valley View Rd: constructed in 2010.  In 2011, it was the #3 most crash prone intersection in the region with 18 crashes.  In 2012 the crashes rose to 22 and in 2013 crashes rose to 25. 

Mineral Point & Pleasant View Rd: constructed in 2011.  In 2012, it was the #1 most crash prone intersection in the region with 46 crashes.  In 2013 crashes dropped to 30.

DaBigE, do you know where County Rd M & Valley View Rd currently stands in the ranking of most crash prone intersections in Madison?  The total number of crashes seem to be increasing year over year at this roundabout.

As far as I know, the 2014 data/report is not available yet. They were implementing some landscaping changes to try to get drivers to slow down further by selectively restrict their sight. I'm curious to find out how that has impacted driver behavior. Note that both of those west-side roundabouts have central islands 145-150-feet in diameter.

One must also keep in mind that got it's first modern roundabouts in 2004 (Thompson & Wis 30/Commercial Ave). Being on the far side of town, overall driver exposure to roundabouts was limited. The roundabouts at Mineral Point & CTH M were the first large roundabouts that drivers on the west side were exposed to. I'm curious to see the crash pattern for the newly-finished jug-handle intersection on the west side will reveal.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 28, 2015, 09:04:43 PM
As far as I know, the 2014 data/report is not available yet. They were implementing some landscaping changes to try to get drivers to slow down further by selectively restrict their sight. I'm curious to find out how that has impacted driver behavior. Note that both of those west-side roundabouts have central islands 145-150-feet in diameter.

It's not a fair comparison to begin with.  Pleasant View Road was constructed as part of the roundabout project so comparing the before/after crash data for these roundabouts is somewhat irrelevant.  I shouldn't have included it in the list of 40 (i didn't do a detailed before/after geometric comparison when compiling the list... it's a lot of data to go through!).    The fact that there was a big increase in crashes at these roundabouts isn't an indication that large central island diameters are more crash prone than smaller ones.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 28, 2015, 09:14:50 PM
A 5-leg roundabout in Valparaiso had 98 crashes in 2014.

(https://www.ci.valparaiso.in.us/images/pages/N1243/5%20Points%20Roundabout%20Rendering.jpg)

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 29, 2015, 11:22:05 AM
The Insurance Institute for Highway Safety released a report in 2000 evaluating the safety of 24 intersections that were converted to roundabouts.  The report found the following:

Quote
The present study evaluated changes in motor vehicle crashes following conversion of 24 intersections from stop sign and traffic signal control to modern roundabouts. The settings, located in 8 states, were a mix of urban, suburban, and rural environments. A before-after study was conducted using the empirical Bayes approach, which accounts for regression to the mean. Overall, the empirical Bayes procedure estimated highly significant reductions of 39 percent for all crash severities combined and 76 percent for all injury crashes. Reductions in the numbers of fatal and incapacitating injury crashes were estimated to be about 90 percent.

http://safety.fhwa.dot.gov/intersection/resources/fhwasa09027/resources/Crash%20Reductions%20Following%20Installation%20of%20Roundabouts.pdf

The study was skewed towards evaluating single-lane roundabouts as only 9 of the 24 intersections evaluated were multi-lane roundabouts.  The 9 multi-lane roundabouts evaluated were all from Colorado and 6 of the 9 serviced interchanges along I-70.  The 3 non-interchange multi-lane roundabouts evaluated in the study were all along Avon Road in Avon, Colorado. When looking at aerials, there appears to be limited traffic generated along the side-street for 2 of the 3 roundabouts (IE. the side-street isn’t a major route).  Here is a list of all the roundabouts evaluated in the Insurance Institute study:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/2000study_zpsvmsggp6l.png)

In the press release for the proposed multi-lane roundabout at State & Ellsworth, the Washtenaw County Road Commission cited a study with familiar looking safety numbers:

Quote
As stated by a 2011 report from the Insurance Institute of Highway Safety, 23 intersections that were converted into roundabouts experienced significant declines in accidents. Total crash frequency fell by approximately 40 percent; injury crash frequency fell by approximately 80 percent; and fatal crash frequency fell by approximately 90 percent.

http://www.wcroads.org/node/529

Citing a study that is skewed towards single-lane roundabouts when a major multi-lane roundabout is being proposed seems disingenuous.  Even the multi-lane roundabouts evaluated in the 2000 study are dissimilar to the roundabout that was being proposed for State & Ellsworth.  In the first year of operation, State & Ellsworth experienced roughly a 10x increase in crashes (not a 40% reduction).  Agencies shouldn't be implying that large multi-lane roundabouts will see a reduction in total crashes (and by citing studies that are skewed towards single-lane roundabouts, that's exactly what they are doing).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 29, 2015, 03:46:03 PM
Here’s a traffic simulation of a roundabout currently under construction in Farmington Hills, Michigan at 14 Mile & Orchard Lake.  Over the last 5 years, the intersection has averaged 46 crashes per year.  This roundabout could experience a significant number of crashes once completed.  Does anybody want to wager how many crashes this roundabout will experience in FY2016?  The over/under is 180 crashes (I’ll bet the over). 

Title: Re: Crash prone 'modern roundabouts'
Post by: NE2 on May 29, 2015, 05:23:31 PM
PARCLO B4
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 29, 2015, 05:40:35 PM
Does anybody want to wager how many crashes this roundabout will experience in FY2016?  The over/under is 180 crashes (I’ll bet the over).

I'm going to guess 110 collisions in the first year, followed by 95 the second year, 83 the third year, 72 the fourth year, 63 the fifth year, and from then on, consistently dropping, just at an increasingly slower rate.

Again though, this isn't all about the number of collisions. It's about severity. As many have noted prior, it's better to have additional, safer collisions than fewer deadly collisions
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 29, 2015, 06:01:37 PM
Does anybody want to wager how many crashes this roundabout will experience in FY2016?  The over/under is 180 crashes (I’ll bet the over).

I'm going to guess 110 collisions in the first year, followed by 95 the second year, 83 the third year, 72 the fourth year, 63 the fifth year, and from then on, consistently dropping, just at an increasingly slower rate.

Again though, this isn't all about the number of collisions. It's about severity. As many have noted prior, it's better to have additional, safer collisions than fewer deadly collisions

If your prediction holds true, 14 Mile & Orchard Lake would go from the 64th most crash prone intersection in SE Michigan to #1 or #2 (fighting for the top spot with the roundabout at Ellsworth & State in Ann Arbor).  That's not good PR anyway you slice it.

http://semcog.org/Data-and-Maps/High-Frequency-Crash-Locations
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 29, 2015, 06:11:34 PM
Does anybody want to wager how many crashes this roundabout will experience in FY2016?  The over/under is 180 crashes (I’ll bet the over).

I'm going to guess 110 collisions in the first year, followed by 95 the second year, 83 the third year, 72 the fourth year, 63 the fifth year, and from then on, consistently dropping, just at an increasingly slower rate.

Again though, this isn't all about the number of collisions. It's about severity. As many have noted prior, it's better to have additional, safer collisions than fewer deadly collisions

If your prediction holds true, 14 Mile & Orchard Lake would go from the 64th most crash prone intersection in SE Michigan to #1 or #2 (fighting for the top spot with the roundabout at Ellsworth & State in Ann Arbor).  That's not good PR anyway you slice it.

http://semcog.org/Data-and-Maps/High-Frequency-Crash-Locations

If people aren't dying, that's good PR. Besides, what's the bad PR? "Collisions on the rise because people can't follow basic rules of the road"?
Title: Re: Crash prone 'modern roundabouts'
Post by: Mergingtraffic on May 29, 2015, 06:22:22 PM
The reason I dislike roundabouts or traffic circles is b/c of the YIELD.  Most drivers think YIELD means they don't have to stop even when traffic is in the circle.  It's only one reason, but a big reason. 

I notice that also on on-ramps to limited access highways with no merge time; there will be a YIELD sign and drivers just merge on causing accidents or forcing vehicles in the right of way to swerve.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 30, 2015, 10:49:16 AM
DaBigE (and tradephoric too for that matter), have you looked into the research MnDOT completed last year on signage and striping with multilane roundabouts?  This is just one study of one multilane roundabout, but they found tweaking signage and striping led to significant decreases in the number of crashes caused by yield failures and improper lane usage:

http://www.dot.state.mn.us/research/TS/2014/201404TS.pdf (summary)

http://www.dot.state.mn.us/research/TS/2014/201404.pdf (study)


I’ll echo what DaBigE said about the study.  There were too many variables at play to determine which changes had the biggest effect on driver behavior (sign and pavement marking type was changed, added additional signs, sign height was lowered, solid line extending from the yield line was lengthened).  This was readily acknowledged in the study:

Quote
Due to the nature of this study, implementing many changes at once, it is difficult to draw direct connections between individual sign and lane marking changes and the observed reductions in traffic violations. In addition, at the moment this represents a solidary experiment in one roundabout.

That said, the study suggests that the standard arrows may be less confusing to drivers and reduce the rate of turning violations when compared to fishhook arrows.  Why then did they revert back to fishhook pavement markings at 66th & Portland when looking at the most recent 2014 aerial?  Would having standard arrow pavement markings several hundred feet before the roundabout and fishhook pavement directly before entering the roundabout be less confusing to drivers?  I think it would add more confusion having a hodgepodge of arrow types like that.  It's hard to know what their thought process is with all the changes they are throwing at this roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 01, 2015, 07:13:13 PM
Another roundabout that has seen a significant increase in crashes is Homer Watson Boulevard and Block Line Road in Kitchener, Ontario.  Countermeasures including reducing the roundabout from 3-lanes to 2-lanes have been tried, but accidents keep going up.  The roundabout sees a significant amount of pedestrian traffic generated by St. Mary’s High school, as seen in the video below:


http://www.therecord.com/news-story/4960212-homer-watson-roundabout-continues-to-perplex-waterloo-region-politicians/
http://www.therecord.com/news-story/5648519-drivers-still-confused-by-homer-watson-roundabout-review-shows/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 01, 2015, 08:43:11 PM
^Another roundabout is scheduled to be constructed in 2016 at Homer Watson & Ottawa Street.  This signalized intersection is one of the busiest in the Waterloo region and has averaged 44.8 crashes over the past 5 years (224 collisions total). 

Every high capacity roundabout cited in this thread has seen an increase in the total number of crashes upon completion, not a decrease.  The article below implies that Bob Henderson - manager of transportation engineering with the Region of Waterloo - believes there will be a reduction in total crashes once the roundabout at Homer Watson & Ottawa Street is completed in 2016.  Is Bob being too optimistic?

Quote
Henderson figures a roundabout will help cut crashes and reduce the severity of injuries since speeds in roundabouts are lower than at intersections with traffic lights.

http://metronews.ca/news/kitchener/1202881/waterloo-regions-most-dangerous-intersection-wont-see-improvements-until-2016/
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 02, 2015, 02:28:07 AM
Is Bob being too optimistic?

"Hi, my name is Bob, and I want everyone to know that there will be a massive increase in collisions once we are finished with this intersection".

That's not really engineer-speak. Truth is, collisions will go up but fatal or severe collisions will drop. Engineers should stop talking about the number of collisions. Instead, they should promote a new roundabout by promoting the large drop in fatal and/or serious collisions that roundabouts have repeatedly been shown to cut down on.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 02, 2015, 07:59:50 AM
Is Bob being too optimistic?

"Hi, my name is Bob, and I want everyone to know that there will be a massive increase in collisions once we are finished with this intersection".

That's not really engineer-speak. Truth is, collisions will go up but fatal or severe collisions will drop. Engineers should stop talking about the number of collisions. Instead, they should promote a new roundabout by promoting the large drop in fatal and/or serious collisions that roundabouts have repeatedly been shown to cut down on.

Here is an article that compares the safety of 17 roundabouts to 395 traffic signals in the Waterloo region.   It came to the following conclusion:

Quote
-At mid-sized intersections, the average traffic light and roundabout each saw one injury-causing collision. The roundabout saw 10 total collisions. The traffic light saw four. A mid-sized intersection sees between 10,000 and 25,000 vehicles per day.

-At busier intersections, the average traffic light and roundabout each saw three injury-causing collisions. The roundabout saw 26 total collisions. The traffic light saw 12. A busier intersection sees more than 25,000 vehicles per day.

-Traffic lights saw one person killed in 2013 (a pedestrian) while roundabouts had no deaths.

http://www.therecord.com/news-story/5217030-roundabouts-crashes-injuries-double-in-5-years-in-waterloo-region/

Roundabouts saw roughly the same amount of injury crashes as the traffic signals yet double the number of total crashes.  Other individual roundabouts cited in this thread have seen an increase in injury crashes.  The roundabout at State & Ellsworth in Ann Arbor (constructed in 2013) averaged 1.66 injury crashes the 3 years prior to the roundabout and saw 6 injury crashes the 1st year after the roundabout.  If you see a dramatic rise in total crashes there’s no guarantee you are going to see a drop in injury crashes.

http://semcog.org/Data-and-Maps/High-Frequency-Crash-Locations/Point_Id/81016689/view/RoadIntersectionCrashDetail
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on June 02, 2015, 08:37:24 AM
Is Bob being too optimistic?

"Hi, my name is Bob, and I want everyone to know that there will be a massive increase in collisions once we are finished with this intersection".

That's not really engineer-speak. Truth is, collisions will go up but fatal or severe collisions will drop. Engineers should stop talking about the number of collisions. Instead, they should promote a new roundabout by promoting the large drop in fatal and/or serious collisions that roundabouts have repeatedly been shown to cut down on.

A *large* drop in fatals/serious conditions? Maybe a drop, but if there's only a few of these accidents a year, how can there be a large drop?

However, there shoudn't be an increase in any type of accident.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 02, 2015, 12:26:57 PM
A *large* drop in fatals/serious conditions? Maybe a drop, but if there's only a few of these accidents a year, how can there be a large drop?

Size is relative. If there were two fatal collisions, and 5 serious collisions in one year, followed by none of either after a roundabout is constructed, that's a significant drop. Perhaps not large, I'll give you that, but certainly notable.

However, there shoudn't be an increase in any type of accident.

That's what I thought prior to this thread, but at least in some areas of the country, that doesn't seem to be the case.

With that said, I still believe that driver familiarity is key for roundabouts to be successful. So, I'm holding back the angst against them for at least 20 years. Or so.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 02, 2015, 08:28:03 PM
A multi-lane roundabout in Rockford, Illinois has seen accidents jump from 3 crashes to 42 crashes when comparing the 6 month before/after crash data.  The roundabout has a central island diameter of 100 feet (roundabouts with the highest increases in crashes seem to have central island diameters of 100 feet or less…. larger diameter roundabouts are seeing increases in total crashes as well, but not the same extent as the smaller diameter ones). 

(http://www.mtjengineering.com/wp-content/uploads/2013/10/Rockfordfeat.jpg)

Quote
In the first six months of 2012 - before the roundabout was built -- just three accidents were reported at Auburn and Main. But in the first six months of 2014, that number shot up to 42 at the new roundabout, 14 times the number of accidents in the intersection compared to the same time period two years earlier.

And it's getting worse. Forty nine crashes were reported in the second six months of 2014, according to police, a more than 15% increase over the previous six months. But since the roundabout is not going anywhere, police are urging drivers to use extra caution when entering the circle. "If you pull up to the roundabout to make your own entry, you have to yield to cars that are already coming in there. Even though they are coming from the left, you have to yield to cars that are already in there and allow them to proceed through."

http://www.mystateline.com/fulltext-news/d/story/accident-rate-at-rockfords-wreck-it-roundabout-get/39721/pqAHhMWENES63uy-ujKlgg
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 02, 2015, 09:00:05 PM
Accident increases at roundabouts have DOT re-thinking

http://www.keprtv.com/news/local/Accident-increases-at-roundabouts-have-DOT-re-thinking-286719871.html
Title: Re: Crash prone 'modern roundabouts'
Post by: Brian556 on June 02, 2015, 09:14:24 PM
Wonder if they will turn out to be a fad like clearview?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 02, 2015, 09:28:14 PM
Accident increases at roundabouts have DOT re-thinking

http://www.keprtv.com/news/local/Accident-increases-at-roundabouts-have-DOT-re-thinking-286719871.html

That might be the first example I've seen of WSDOT redesigning a roundabout. Usually they don't touch them, and instead spend money on educational campaigns. All told, I'm disappointed that WSDOT feels the need to change anything. I say, leave the roundabout alone for another ten years and come back. If anything, the total number of vehicles filtering through the intersection has been steadily increasing since they rebuilt the junction 8 years ago (between 2000 and 2014, the population of the area increased about 45%), which wouldn't correlate to a decrease in collisions.

Wonder if they will turn out to be a fad like clearview?

The number of roundabouts that see an increase in collisions are greatly overshadowed by the number that do not. So no, definitely not.
Title: Re: Crash prone 'modern roundabouts'
Post by: froggie on June 02, 2015, 11:09:56 PM
Multi-lane roundabouts might be reconsidered, but I highly doubt single-lane roundabouts will "turn out to be a fad".  The safety benefits are very well documented, even within the literature and numbers that tradephoric has been posting in recent weeks.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 03, 2015, 10:11:45 AM
In a previous post, I queried out 40 multi-lane roundabouts that have 2-entry lanes for all 4-legs (ie. the roundabouts in America that likely have the highest traffic volumes).  I’ve tracked down before/after crash data for 14 of them.  The excel file includes data links to articles/publications where the data was obtained.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBDATASummary_zpsg7upbybr.png)
http://www.mediafire.com/view/p0u5ovrupr0175m/Multi-lane_roundabout_crashes.xlsx

The takeaway is that smaller roundabouts seem to be more accident prone than larger roundabouts.  Would there have been 171 crashes at State & Ellsworth if the roundabout was constructed with a central island diameter of 140’ as opposed to 100’?  This thread wasn't meant to bash roundabouts but to discuss ways to reduce the crash frequency at the highest AADT roundabouts.  My thought is make them just a little bit bigger.

Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on June 03, 2015, 10:58:02 AM
I held back on saying anything, and while I don't have any actual documentation, I want to know why these dual-lane roundabouts are having so many accidents when accidents at Jersey traffic circles, many of which are at least 2 lanes wide with no lane markings and little if any signed traffic control have fewer problems. 

The main reason Jersey circles have been removed wasn't because of accidents, but more so due to the congestion with so much traffic trying to use them.  Heck, many of these circles not only have the normal roads entering/exiting them, but business driveways enter and exit directly from them too.

Title: Re: Crash prone 'modern roundabouts'
Post by: Bickendan on June 03, 2015, 12:08:56 PM
Maybe all the Yield signs should be swapped out with full on Stop signs.
Seems to be drivers don't know what 'yield' means.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on June 03, 2015, 12:55:53 PM
Maybe all the Yield signs should be swapped out with full on Stop signs.
Seems to be drivers don't know what 'yield' means.

Their first collision or near-miss will educate them nicely.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on June 03, 2015, 01:09:32 PM
Maybe all the Yield signs should be swapped out with full on Stop signs.
Seems to be drivers don't know what 'yield' means.

Their first collision or near-miss will educate them nicely.

That doesn't help the guy that had the right of way that is now involved in an accident, delaying or missing whatever activity they were trying to get to, and now have to deal with insurance, car issues, medical issues, job related issues, etc, etc, etc.

How was he educated? 
Title: Re: Crash prone 'modern roundabouts'
Post by: Bickendan on June 03, 2015, 02:22:06 PM
Maybe all the Yield signs should be swapped out with full on Stop signs.
Seems to be drivers don't know what 'yield' means.

Their first collision or near-miss will educate them nicely.

That doesn't help the guy that had the right of way that is now involved in an accident, delaying or missing whatever activity they were trying to get to, and now have to deal with insurance, car issues, medical issues, job related issues, etc, etc, etc.

How was he educated? 
He gets an unfortunate and unneeded education in the intricacies of insurance claims.

Seriously though, stop signs at roundabouts. Coe Circle (NE 39th AveCésar Chavez Blvd and Glisan St in Portland) has been there since before the 1920s and I don't recall any incidents there since I moved to Portland in 94. While not the conventional multi-lane setup (right lane in all directions is right turn only so buses can stop at the gore islands), it does use stop signs to control traffic.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on June 03, 2015, 02:25:38 PM
Seriously though, stop signs at roundabouts. Coe Circle (NE 39th AveCésar Chavez Blvd and Glisan St in Portland) has been there since before the 1920s and I don't recall any incidents there since I moved to Portland in 94. While not the conventional multi-lane setup (right lane in all directions is right turn only so buses can stop at the gore islands), it does use stop signs to control traffic.

In practice, are they treated as typical American "sure, roll through the stop sign at 5 mph as long as you tap your brakes" stops (i.e. what "yield/give way" actually means in the rest of the world), or are they real stops like European stop signs?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 03, 2015, 02:34:53 PM
I held back on saying anything, and while I don't have any actual documentation, I want to know why these dual-lane roundabouts are having so many accidents when accidents at Jersey traffic circles, many of which are at least 2 lanes wide with no lane markings and little if any signed traffic control have fewer problems. 

The main reason Jersey circles have been removed wasn't because of accidents, but more so due to the congestion with so much traffic trying to use them.  Heck, many of these circles not only have the normal roads entering/exiting them, but business driveways enter and exit directly from them too.

New Jersey's rotaries probably work well because drivers are familiar with the intersections, and the legal maneuvers that can be performed at them. That's why I am personally not ready to give up on multi-lane roundabouts anytime soon. I think, given enough time, the overall number of collisions will drop off.

Many of the new modern roundabouts have been placed where there was no intersection before, so through traffic is probably not used to having to yield to other traffic, so they just keep on trucking (maybe).
Title: Re: Crash prone 'modern roundabouts'
Post by: Bickendan on June 03, 2015, 02:44:38 PM
Seriously though, stop signs at roundabouts. Coe Circle (NE 39th AveCésar Chavez Blvd and Glisan St in Portland) has been there since before the 1920s and I don't recall any incidents there since I moved to Portland in 94. While not the conventional multi-lane setup (right lane in all directions is right turn only so buses can stop at the gore islands), it does use stop signs to control traffic.

In practice, are they treated as typical American "sure, roll through the stop sign at 5 mph as long as you tap your brakes" stops (i.e. what "yield/give way" actually means in the rest of the world), or are they real stops like European stop signs?
It's dependent how heavy traffic in the circle is. As mentioned up thread, the advertising panels TriMet uses on their bus shelters in the gore points annoyingly obstruct line of sight, so drivers will cautiously creep past the stop sign to check for traffic on their left and wait there for a break. Bikers have the hardest time in the circle because it's built onto a hill (northbound 39th is uphill through the circle).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 05, 2015, 11:01:36 AM
The Phase 2 roundabout study funded by the Wisconsin Department of Transportation analyzed 30 roundabouts built in 2008 or before (15 single-lane, 11 multi-lane, 4 spiral).  This was the main finding of the study:

Quote
Wisconsin roundabouts had an estimated 12 percent increase in total crashes and a 38 percent decrease in injury crashes.

Below is a KMZ file of the 30 Wisconsin roundabouts analyzed and a link to the study.

KMZ FILE:  http://www.mediafire.com/download/9oyt92teh4ee09y/Wisconsin+Roundabout+Study+%28Phase+2%29.kmz
STUDY:  http://www.topslab.wisc.edu/programs/safety/projects/roundabouts/WI%20Roundabout%20Evaluation%20FINAL%20REPORT%20-%20Phase%202.pdf


A few potential trends that can be seen when analyzing the KMZ/Study:

1.  Bigger is better.  Roundabouts with larger central island diameters perform better, on average, than roundabouts with smaller central island diameters.  Of the 4 roundabouts with a central island diameter of 120’ or greater, all saw a reduction in total crashes.

2.  Crashes are lower at interchange roundabouts.  The majority of the multi-lane roundabouts that saw a reduction in total crashes were at interchanges.

3.  Spiral roundabouts seem to perform better, on average, than non-spiral roundabouts. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 05, 2015, 01:28:08 PM
All I am going to say on this is there's a lot of flaws that can be found in WisDOT's roundabout crash studies (Phase III is set to be released later this summer).

DaBigE, do you know if Phase III is going to include more recent roundabouts constructed since 2008?  Wisconsin has aggressively been constructing higher capacity roundabouts more recently.  Today, there are at least 7 roundabouts in Wisconsin that have 3-circulating lanes (in 2008 there were none).  It would be interesting to see a study that analyzed the higher capacity roundabouts in Wisconsin that have been constructed recently.  Hopefully they can include roundabouts constructed in 2009, 2010, and 2011 in their next study.

Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on June 06, 2015, 04:20:34 PM
All I am going to say on this is there's a lot of flaws that can be found in WisDOT's roundabout crash studies (Phase III is set to be released later this summer).

DaBigE, do you know if Phase III is going to include more recent roundabouts constructed since 2008?  Wisconsin has aggressively been constructing higher capacity roundabouts more recently.  Today, there are at least 7 roundabouts in Wisconsin that have 3-circulating lanes (in 2008 there were none).  It would be interesting to see a study that analyzed the higher capacity roundabouts in Wisconsin that have been constructed recently.  Hopefully they can include roundabouts constructed in 2009, 2010, and 2011 in their next study.

Yes, it will, according to the ITE presentation I attended back in April, it will cover roundabouts built thru 2009.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 09, 2015, 12:37:20 PM
I held back on saying anything, and while I don't have any actual documentation, I want to know why these dual-lane roundabouts are having so many accidents when accidents at Jersey traffic circles, many of which are at least 2 lanes wide with no lane markings and little if any signed traffic control have fewer problems. 

The main reason Jersey circles have been removed wasn't because of accidents, but more so due to the congestion with so much traffic trying to use them.  Heck, many of these circles not only have the normal roads entering/exiting them, but business driveways enter and exit directly from them too.



There's little evidence to suggest that traffic circles perform better than modern roundabouts.  According to the article below, when a traffic circle in Augusta, Maine was converted to a modern roundabout the intersection saw a 60% reduction in total crashes. 

http://www.pressherald.com/2013/04/17/terms-for-traffic-circles-cause-confusion_2013-04-18/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 24, 2015, 10:07:37 AM
The Wisconsin and Michigan experiences that tradephoric commented on are the general opposite of Minnesota's experience, at least anecdotally as I don't think MnDOT has done a comprehensive study yet.  They have studied a few roundabouts, including a rural roundabout in particular (on MN 13 in Scott County), built in response to multiple fatal crashes, where there were HUGE declines in overall crashes after the roundabout was completed.  There's also a study documenting a multilane roundabout in Richfield that did see a high number of crashes (there wasn't really anything to compare it to pre-construction), but after tweaking with signage and striping saw crashes and "illegal turns" (i.e. turning left from the outer lane) decrease by about half.  This Richfield study/research may hold the key to getting better results out of multilane roundabouts.

In 2014, Andrew Plowman presented a presentation during the 4th Annual International Conference on Roundabouts detailing crash rates of 12 multi-lane roundabouts in Minnesota:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/MNRBdata_zpsvkjdst9f.png)
http://teachamerica.com/RAB14/RAB1410APlowman/index.htm

*They found that 2x2 roundabouts have higher crash rates than 2x1 roundabouts.  Interestingly, the roundabouts at Bailey/Radio & Broadway/Lake have since been converted from 2x2 roundabouts to 2x1 roundabouts. 

*The 2x1 roundabout with the highest crash rate was at Diffley & Rahn.  This roundabout has the smallest central island diameter of any roundabout analyzed in the study (only 83 feet).  I’ve been hammering on that roundabouts with small diameters seem to be more accident prone than roundabouts with larger diameters and Diffley & Rahn seems to support that point.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on June 24, 2015, 12:02:26 PM
All I know is that the 2 x 2 roundabouts around here are prone to senile old people in the right lane of the roundabout continuing around the roundabout (ignoring the striping) and smashing into people following the striping from the left lane (i.e., exiting the roundabout).

See here for an example (https://goo.gl/maps/bX1wR).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 24, 2015, 02:54:01 PM
All I know is that the 2 x 2 roundabouts around here are prone to senile old people in the right lane of the roundabout continuing around the roundabout (ignoring the striping) and smashing into people following the striping from the left lane (i.e., exiting the roundabout).

See here for an example (https://goo.gl/maps/bX1wR).

The roundabout is striped as a spiral roundabout yet the central island is circular (the central island isn’t designed to be a spiral roundabout).   The red path driver is following the path of least resistance to make a left turn through the roundabout.  The green path driver is doing everything right yet is liable to get sideswiped by the red path driver. 

Bethlehem, NY (New Scotland Road and Route 140)
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/NYRB_zpsmnpyxdmi.png)

Here’s an almost identical design of a 2x2 roundabout in Malta, NY.  Notice how the spiral dashes are faded in the aerial.  Even if they spiral dashes aren’t faded, the red path driver is going to cheat (as seen in the streetview image…the blue SUV is debating where the silver Honda is heading).

Malta, NY (Route 9, Route 67 and Dunning Street)
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/NYRBMalta_zpsifwwmbgh.png)
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/SVMalta_zpspdoii1ub.png)

Quote
In Malta, the roundabout at Route 9, Route 67 and Dunning Street went from an average of 7.8 crashes a year before the rotary to 45.7 a year afterward. In Bethlehem, the number of accidents at New Scotland Road and Route 140 jumped from an average of 9.6 a year to 38.3.
http://www.insurancejournal.com/news/east/2011/06/28/204259.htm

Moral of the story... spiral roundabouts should have properly designed central islands (and shouldn't rely on pavement markings to do the job). 

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 25, 2015, 07:51:33 AM
The New York roundabouts in Bethlehem and Malta have nearly identical designs.  The biggest difference is size.

103 ft roundabout (Malta) = 445% increase in crashes
130 ft roundabout (Bethlehem) = 299% increase in crashes

IMO, both of these roundabouts have similar design flaws but the Bethlehem roundabout still performed better (even as traffic volume likely increased more at the Bethlehem roundabout since a lot of development took place as part of that roundabout project). 

Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on June 25, 2015, 01:04:27 PM
Oh, don't get me wrong: The Slingerlands roundabouts are much much much much much much better than the traffic signals that they replaced.  I just wish our drivers were trained well enough to read the signs and pavement markings!

Fun fact about the Malta roundabouts:  I was at ITSNY one year long ago where the Chief Operations Officer of NYSDOT spoke.  He brought up the Malta roundabouts and said, "You've got five roundabouts within a half mile!  We'll see how that works out for you!"  To this day, I have no idea who exactly he was talking to (Region 1?  Well, didn't he approve of the project himself, being the COO? Whaaaat? :D), but he had a tendency to sort of get lost in his sermons. :D
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 25, 2015, 03:19:53 PM
Oh, don't get me wrong: The Slingerlands roundabouts are much much much much much much better than the traffic signals that they replaced. I just wish our drivers were trained well enough to read the signs and pavement markings!

The problem is the pavement markings are so faded in that Malta roundabout aerial that an unfamiliar driver would have no idea that they are suppose to divert to the outside lane during the left turn maneuver.  With those faded spiral markings, I can absolutely see myself being that "red path" driver. 

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 25, 2015, 05:39:58 PM
Oh, don't get me wrong: The Slingerlands roundabouts are much much much much much much better than the traffic signals that they replaced. I just wish our drivers were trained well enough to read the signs and pavement markings!

The problem is the pavement markings are so faded in that Malta roundabout aerial that an unfamiliar driver would have no idea that they are suppose to divert to the outside lane during the left turn maneuver.  With those faded spiral markings, I can absolutely see myself being that "red path" driver.

Perhaps if they opened up the closed lanes, it wouldn't be a big deal.
Title: Re: Crash prone 'modern roundabouts'
Post by: iBallasticwolf2 on June 25, 2015, 06:46:47 PM
I think these crash prone factors in modern roundabouts can be mostly fixed if:
1. Lane markings were kept easily seeable.
2. The right type of island is used. (Ex. Not using a circular island on a spiral roundabout.)
3. Island widths are higher. It seems that roundabouts with higher island widths have a smaller increase of accidents then roundabouts with lower island widths.
4. Drivers are taught you to drive these roundabouts better. We all know driver's driving skills deteriorate alot and half of them were taught before roundabouts were common.
Title: Re: Crash prone 'modern roundabouts'
Post by: Sykotyk on June 25, 2015, 10:49:06 PM
Early signage is key. You don't want sensory overload for people just as they enter the roundabout. You want them to know which lane they need to be in for which direction they plan on continuing. Generally, I think roundabouts should only be used for low-volume roads meeting eachother where a four-way stop or simple traffic light was the optimal former solution. The problem is in heavy traffic uses, roundabouts lose their 'flow' and it becomes a race to get into the traffic circle first so you don't have to stop, even if it's a bit dangerous or acceleration takes place.

I've never dealt with a three-lane entry that I can recall, and I don't want to. Enough people fail to use the two-lane ones properly. Which is sad, because misusing a roundabout should carry with it the same general emphasis as running a red light, or turning left before oncoming traffic. Yet, to many, that 'YIELD' sign means they get to go if they take the road first.

Going back on it, that's part of the problem. The Yield signs aren't being properly followed. If there's a four-entry roundabout with four yield signs, the second car in line does not get to go because the car in front of them went. When traffic builds to that point, it basically assumes the role of a four-way stop with the entry-points cycling in a (vehicle to the right goes first) and each car at the yield sign going one at a time. Instead it's "there's 5 cars in line at this yield sign, so all 5 get to go at once".
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 29, 2015, 08:40:06 PM
An example of a how a dominant leg at a roundabout can make it difficult for traffic at other legs to enter the roundabout (especially for semi's).

Title: Re: Crash prone 'modern roundabouts'
Post by: Brian556 on June 29, 2015, 09:04:26 PM
Quotew from        :
Quote
An example of a how a dominant leg at a roundabout can make it difficult for traffic at other legs to enter the roundabout (especially for semi's).

This is very true. When one leg has a very high volume, traffic on other legs does not get fair opportunity to enter the roundabout.
The southern one in Windermere FL defiantly has this problem. It seems pretty ridiculous, and unfair, to have to sit and wait a long time just to enter the roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 29, 2015, 11:06:57 PM
An example of a how a dominant leg at a roundabout can make it difficult for traffic at other legs to enter the roundabout (especially for semi's).

This is very true. When one leg has a very high volume, traffic on other legs does not get fair opportunity to enter the roundabout.
The southern one in Windermere FL defiantly has this problem. It seems pretty ridiculous, and unfair, to have to sit and wait a long time just to enter the roundabout.

But this is kind of how roundabouts work...?

In regards to the video, at no point do any of the legs get unreasonably congested. This is not a very good example, tradephoric, if you're looking for a roundabout with "unfair" entry volumes.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on June 29, 2015, 11:27:05 PM
The experience in the UK (where very high AADT is tolerated before improvements are made, particularly in rural and suburban areas, compared to the US) is that you can end up with situations like that even in a single-lane roundabout, particularly when there isn't enough traffic looping around to break up entry from one direction. The UK solution is almost always signalization, and when that doesn't work, adding some sort of flyover while keeping the signalized roundabout to continue to annoy everyone else. But this tends to happen at intersections that, by US standards, would be something like LOS G or H if the scale went that high.

Notorious example: A1-A421 Black Cat (https://en.wikipedia.org/wiki/Black_Cat_Roundabout) (see also: here (http://www.cbrd.co.uk/badjunctions/1-421/); in most of the US, it'd have been rebuilt as a Y-split or trumpet in the 1960s or 70s. Hell, the A1 would have been rebuilt properly as a freeway on a new alignment with a full interchange with the cheapo-freeway A421.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 30, 2015, 09:28:47 AM
An example of a how a dominant leg at a roundabout can make it difficult for traffic at other legs to enter the roundabout (especially for semi's).

This is very true. When one leg has a very high volume, traffic on other legs does not get fair opportunity to enter the roundabout.
The southern one in Windermere FL defiantly has this problem. It seems pretty ridiculous, and unfair, to have to sit and wait a long time just to enter the roundabout.
In regards to the video, at no point do any of the legs get unreasonably congested. This is not a very good example, tradephoric, if you're looking for a roundabout with "unfair" entry volumes.

The video shows some sweet 4k drone video of a spiral roundabout in action, if nothing else.  It probably wasn't the best example of a roundabout with uneven volumes but the point is still valid.  There is a roundabout by me where traffic on the heaviest leg experiences 20 second delays during the peak rush while adjacent legs experience 20 minute delays.  Traffic on the heaviest leg just overtakes the roundabout making it difficult for traffic on other legs to enter (especially tractor trailers).

Here's the roundabout in question.  The NB leg is the dominant movement, causing large backups on the WB leg during peak rush. 

https://www.google.com/maps/@42.5544792,-83.4485635,303m/data=!3m1!1e3
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on June 30, 2015, 09:34:47 AM
An example of a how a dominant leg at a roundabout can make it difficult for traffic at other legs to enter the roundabout (especially for semi's).

This is very true. When one leg has a very high volume, traffic on other legs does not get fair opportunity to enter the roundabout.
The southern one in Windermere FL defiantly has this problem. It seems pretty ridiculous, and unfair, to have to sit and wait a long time just to enter the roundabout.
In regards to the video, at no point do any of the legs get unreasonably congested. This is not a very good example, tradephoric, if you're looking for a roundabout with "unfair" entry volumes.

The video shows some sweet 4k drone video of a spiral roundabout in action, if nothing else.  It probably wasn't the best example of a roundabout with uneven volumes but the point is still valid.  There is a roundabout by me where traffic on the heaviest leg experiences 20 second delays during the peak rush while adjacent legs experience 20 minute delays.  Traffic on the heaviest leg just overtakes the roundabout making it difficult for traffic on other legs to enter (especially tractor trailers).


20 minute delays?  That's kinda doubtful there.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on June 30, 2015, 10:48:15 AM
An example of a how a dominant leg at a roundabout can make it difficult for traffic at other legs to enter the roundabout (especially for semi's).


Looks like the recently reconfigured DePere roundabout (https://www.google.com/maps/@44.4475215,-88.060417,110m/data=!3m1!1e3)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 30, 2015, 11:35:42 AM
Looks like the recently reconfigured DePere roundabout (https://www.google.com/maps/@44.4475215,-88.060417,110m/data=!3m1!1e3)

Thanks DaBigE.  I was wondering what roundabout that was.  Here is a list of roundabouts that have been reconfigured to reduce the number of circulating lanes inside the roundabout.  In every case, reducing the number of circulating lanes was meant to counteract the high crash rates that were occurring at these roundabouts. 

-14th Street & Superior in Lincoln, Nebraska
-Maple & Drake in Farmington Hills, Michigan
-Maple & Farmington in Farmington Hills, Michigan
-Homer Watson Boulevard and Block Line Road in Kitchener, Ontario
-Bailey & Radio in Woodbury, Minnesota
-Broadway Avenue & Lake Street in Forrest Lake, Minnesota
-Main Ave & Broadway in De Pere, Wisconsin
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on June 30, 2015, 12:11:13 PM
Looks like the recently reconfigured DePere roundabout (https://www.google.com/maps/@44.4475215,-88.060417,110m/data=!3m1!1e3)

Thanks DaBigE.  I was wondering what roundabout that was.  Here is a list of roundabouts that have been reconfigured to reduce the number of circulating lanes inside the roundabout.  In every case, reducing the number of circulating lanes was meant to counteract the high crash rates that were occurring at these roundabouts. 

-14th Street & Superior in Lincoln, Nebraska
-Maple & Drake in Farmington Hills, Michigan
-Maple & Farmington in Farmington Hills, Michigan
-Homer Watson Boulevard and Block Line Road in Kitchener, Ontario
-Bailey & Radio in Woodbury, Minnesota
-Broadway Avenue & Lake Street in Forrest Lake, Minnesota
-Main Ave & Broadway in De Pere, Wisconsin

In the case of the DePere roundabout, it wasn't just reducing the circulating lanes. Some of the approach lane assignments were changed as well. WisDOT used to have a nice press release depicting the lane reconfiguration, but since their site was redesigned, I cannot seem to locate it anymore. According to the original plans I found, when the roundabout was first built, the configuration was a symmetrical 2-lane approach for all legs.
Title: Re: Crash prone 'modern roundabouts'
Post by: UCFKnights on June 30, 2015, 10:30:47 PM
I feel multilane roundabout turn indicators seem to not be understood by people for some reason. I was just traveling through Melbourne and had to stop short this weekend for a person turning left from the right lane at this one: https://www.google.com/maps/place/Melbourne,+FL/@28.2298461,-80.725248,126m/data=!3m1!1e3!4m2!3m1!1s0x88de0e2c4771994d:0x8bcdb254a90cd2a8!6m1!1e1

The roundabout seemed to have standard lane markings and then was switched to roundabout turn markings. Actually, on the history street view, it looks like it originally was operating with no road markings or signs of what the lanes do. I am curious which performed better.

The markings in these multilane roundabouts need massive improvement. Our other intersections usually have the lane markings repeated at least 3 times coming up the intersection (where without them, I doubt there would be confusion on most normal intersections). Why not do the same on roundabouts? If a lane only permits one movement, it should have ONLY.  If its a spiral where you're supposed to switch lanes within the roundabout after an exit, we should have extended arrow showing both lanes you can switch to like I've recently seen on Orlando's highways: https://www.google.com/maps/@28.547379,-81.229906,3a,17.4y,271.83h,89.06t/data=!3m6!1e1!3m4!1so_4q0MjltIChCOxVRShxsg!2e0!7i13312!8i6656!6m1!1e1
Title: Re: Crash prone 'modern roundabouts'
Post by: roadfro on June 30, 2015, 11:04:28 PM
If its a spiral where you're supposed to switch lanes within the roundabout after an exit, we should have extended arrow showing both lanes you can switch to like I've recently seen on Orlando's highways: https://www.google.com/maps/@28.547379,-81.229906,3a,17.4y,271.83h,89.06t/data=!3m6!1e1!3m4!1so_4q0MjltIChCOxVRShxsg!2e0!7i13312!8i6656!6m1!1e1

If it's a spiral, you wouldn't be changing lanes. Rather, the lane markings should naturally guide you to the outside at a specified point. (Of course, this assumes that the markings and roundabout features are properly designed to do this.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on July 01, 2015, 03:43:15 AM
20 minute delays?  That's kinda doubtful there.
Indeed, but don't get in the way of someone and their pet hate.

Of course the reason this thread exists doesn't seem to be the increased crash rate (mostly caused by diastavrosophobia and people's refusal to yield on entry for a couple of years after installation) but rather the OP's hatred of anything that mucks up his signal procession diagrams - non signallised interchanges, and parclos that aren't type B4.

I used to live in a city that replaced roundabouts with signals at almost every location (having the most in Europe). It had the most state of the art systems controlling them. Some junctions would have 20min delays most peak ones - and oddly not ones between major roads, and there were times when there was total gridlock. My last house move within the city would have been better done with a pack mule than a car, as it occurred on a gridlock day. Speeds were roughly 0.5mph on all the roads - each of the 6 times I travelled from my new house to the city centre or back, it took about 80 or 90 minutes - it's walk-able in 40.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 01, 2015, 04:05:34 AM
If its a spiral where you're supposed to switch lanes within the roundabout after an exit, we should have extended arrow showing both lanes you can switch to like I've recently seen on Orlando's highways: https://www.google.com/maps/@28.547379,-81.229906,3a,17.4y,271.83h,89.06t/data=!3m6!1e1!3m4!1so_4q0MjltIChCOxVRShxsg!2e0!7i13312!8i6656!6m1!1e1

That style of arrow is very British. I've never seen such an arrow in the US before.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on July 01, 2015, 09:27:14 AM
If its a spiral where you're supposed to switch lanes within the roundabout after an exit, we should have extended arrow showing both lanes you can switch to like I've recently seen on Orlando's highways: https://www.google.com/maps/@28.547379,-81.229906,3a,17.4y,271.83h,89.06t/data=!3m6!1e1!3m4!1so_4q0MjltIChCOxVRShxsg!2e0!7i13312!8i6656!6m1!1e1

That style of arrow is very British. I've never seen such an arrow in the US before.

In the aerial view, it's a shame there's a truck driving over the arrow at the time. But you can see the advanced painted arrows are the traditional MUTCD arrows, then the very elongated British-looking arrow.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 01, 2015, 10:57:53 AM
20 minute delays?  That's kinda doubtful there.
Indeed, but don't get in the way of someone and their pet hate.

Of course the reason this thread exists doesn't seem to be the increased crash rate (mostly caused by diastavrosophobia and people's refusal to yield on entry for a couple of years after installation) but rather the OP's hatred of anything that mucks up his signal procession diagrams - non signallised interchanges, and parclos that aren't type B4.

I used to live in a city that replaced roundabouts with signals at almost every location (having the most in Europe). It had the most state of the art systems controlling them. Some junctions would have 20min delays most peak ones - and oddly not ones between major roads, and there were times when there was total gridlock. My last house move within the city would have been better done with a pack mule than a car, as it occurred on a gridlock day. Speeds were roughly 0.5mph on all the roads - each of the 6 times I travelled from my new house to the city centre or back, it took about 80 or 90 minutes - it's walk-able in 40.

I'm in favor of roundabouts.  This thread highlights 2x2 and 3x2 roundabouts have seen an increase in total crashes AND suggests solutions to reduce the crash rates at these high volume roundabouts.  If i had such a hatred for roundabouts, why would i be so interested in how central island diameters impact crash rates?

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 01, 2015, 03:38:49 PM
Here are back-to-back-to-back 3-lane roundabouts in Green Bay Wisconsin (all spirals  :clap:).  Looking at the crash data from Shawano Avenue & Taylor Street it seems to be performing pretty well (only 30 crashes from 2010-2012... roundabout was constructed in 2011).

https://www.google.com/maps/@44.5369,-88.07445,1247m/data=!3m1!1e3

2010-2012 Green Bay Metropolitan Area Intersection Crash Study
http://www.co.brown.wi.us/i/f/Metro%20area%20crash%20study%20for%202010-2012%20%28final%29%20-%20February%202015.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: UCFKnights on July 01, 2015, 06:08:43 PM
If its a spiral where you're supposed to switch lanes within the roundabout after an exit, we should have extended arrow showing both lanes you can switch to like I've recently seen on Orlando's highways: https://www.google.com/maps/@28.547379,-81.229906,3a,17.4y,271.83h,89.06t/data=!3m6!1e1!3m4!1so_4q0MjltIChCOxVRShxsg!2e0!7i13312!8i6656!6m1!1e1

That style of arrow is very British. I've never seen such an arrow in the US before.

In the aerial view, it's a shame there's a truck driving over the arrow at the time. But you can see the advanced painted arrows are the traditional MUTCD arrows, then the very elongated British-looking arrow.
They are all over Orlando's highways now wherever they have the lanes with 2 choices. However, they were added relatively recently, post-satellite view updates.
Title: Re: Crash prone 'modern roundabouts'
Post by: johndoe on July 02, 2015, 02:06:56 PM
The roundabout seemed to have standard lane markings and then was switched to roundabout turn markings. Actually, on the history street view, it looks like it originally was operating with no road markings or signs of what the lanes do. I am curious which performed better.

If memory serves some agencies are going AWAY from "fishhook" (roundabout specific) arrow markings because they are believed to be more complicated than necessary.  They're going back to the traditional arrows.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 06, 2015, 12:50:04 PM
The roundabout seemed to have standard lane markings and then was switched to roundabout turn markings. Actually, on the history street view, it looks like it originally was operating with no road markings or signs of what the lanes do. I am curious which performed better.

If memory serves some agencies are going AWAY from "fishhook" (roundabout specific) arrow markings because they are believed to be more complicated than necessary.  They're going back to the traditional arrows.

The study done on the Richfield, Minnesota roundabout at 66th & Portland (previously discussed in this thread) did suggest that the standard arrows are less confusing to drivers than the fishhooks.  That said the roundabout was recently repainted with fishhook pavement markings (well after the release of the study).

The Richfield roundabout is a 2x2 non-spiral roundabout with a central island diameter of 95 feet and an AADT of 29,000 vehicles.  The Richfield roundabout has the characteristics of other accident prone roundabouts cited on this thread.  Tweaking pavement markings and signage isn’t going to increase the central island diameter of the roundabout from 95 feet to 150 feet.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 06, 2015, 06:08:55 PM
Tweaking pavement markings and signage isn’t going to increase the central island diameter of the roundabout from 95 feet to 150 feet.

So the only way to make a roundabout safer is to make it larger? I find that very hard to believe. Despite all these stats, I haven't seen any studies on turbo roundabouts (Dutch-style), which are relatively tiny but seem to have characteristics of what I would think a safe roundabout would at least look like.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 07, 2015, 02:42:11 AM
So the only way to make a roundabout safer is to make it larger? I find that very hard to believe.

The point I was making is there may be a fundamental problem with these crash prone roundabouts that can’t be fixed with pavement marking tweaks.  This thread has compared the safety of spiral vs. non-spiral roundabouts, interchange vs. non-interchange roundabouts, the effects of reducing the number of circulating lanes (converting 2x2 roundabouts to 2x1 roundabouts), and discussed how faded pavement markings can lead to driver error (specifically faded spiral markings).  Other topics in regards to safety include entry angles, overhead signage, fishhook vs standard markings, etc, etc.   You are basically ignoring the entire thread when you make that implication.

Despite all these stats, I haven't seen any studies on turbo roundabouts (Dutch-style),

Literature exists in regards to the safety performance of turbo-roundabouts:
http://trrjournalonline.trb.org/doi/10.3141/2096-03

which are relatively tiny

This turbo roundabout isn’t tiny:
https://www.google.com/maps/@51.9680282,4.4556574,121m/data=!3m1!1e3

but seem to have characteristics of what I would think a safe roundabout would at least look like.

Actual crash data is useful in verifying that preconceived notion.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 07, 2015, 01:31:05 PM
...a fundamental problem with these crash prone roundabouts that can’t be fixed...

In many cases, that problem is the self-centered driver. The ones in a hurry, distracted, and like to make their own traffic rules. You can't just look at the sheer number of crashes alone. You have to look at the type/cause of crash, and the majority of the time it's been due to failure to yield or improper lane usage. If there was a way to accurately track near-misses, I bet the larger roundabouts aren't any better.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 07, 2015, 03:49:49 PM
...a fundamental problem with these crash prone roundabouts that can’t be fixed...

In many cases, that problem is the self-centered driver. The ones in a hurry, distracted, and like to make their own traffic rules. You can't just look at the sheer number of crashes alone. You have to look at the type/cause of crash, and the majority of the time it's been due to failure to yield or improper lane usage. If there was a way to accurately track near-misses, I bet the larger roundabouts aren't any better.

The majority of crashes at signalized intersections are due to driver error.
The majority of crashes at modern roundabouts are due to driver error. 

The very first post in this thread has a link to SEMCOG crash data for the roundabout at State & Ellsworth in Ann Arbor.  Most of the crashes were due to failure to yield (angle) and improper lane usage (sideswipe same).  The 3 years before the roundabout, the intersection averaged 18 crashes a year.  The first year after the roundabout, there were 170 crashes.  Can the roundabout at State & Ellsworth be considered a success because the majority of the 170 crashes was due to driver error?  I don't think so.

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 07, 2015, 05:29:08 PM
Larger roundabouts may be safer assuming the entry angles of the roundabout are designed properly and circulating speeds remain low.  Consider the following scenario.  CAR A enters the roundabout mistakenly believing CAR B is about to exit.  Would u want CAR B to take 1.7 seconds or 3.4 seconds to travel the blue path?  More reaction time is a good thing!

95 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test4_zpshnyyiesp.jpg)

160 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test3_zpscdfdzp4h.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 07, 2015, 05:31:47 PM
Consider the following scenario.  CAR A enters the roundabout mistakenly believing CAR B is about to exit.  Would u want CAR B to take 1.7 seconds or 3.4 seconds to travel the blue path?  More reaction time is a good thing!

This is probably the best reasoning I've heard in a long time. That actually makes quite a lot of sense.
Title: Re: Crash prone 'modern roundabouts'
Post by: iBallasticwolf2 on July 07, 2015, 05:34:06 PM
Consider the following scenario.  CAR A enters the roundabout mistakenly believing CAR B is about to exit.  Would u want CAR B to take 1.7 seconds or 3.4 seconds to travel the blue path?  More reaction time is a good thing!

This is probably the best reasoning I've heard in a long time. That actually makes quite a lot of sense.

This determines that a larger diameter in a roundabout might be a good thing.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 07, 2015, 05:59:22 PM
Larger roundabouts may be safer assuming the entry angles of the roundabout are designed properly and circulating speeds remain low.  Consider the following scenario.  CAR A enters the roundabout mistakenly believing CAR B is about to exit.  Would u want CAR B to take 1.7 seconds or 3.4 seconds to travel the blue path?  More reaction time is a good thing!

95 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test4_zpshnyyiesp.jpg)

160 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test3_zpscdfdzp4h.jpg)

You make the assumption that vehicle B will be traveling the same speed in both scenarios. The larger the circle, the faster vehicle B can comfortably travel. The faster vehicle B is traveling, the harder it is for vehicle A to judge the gap.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 07, 2015, 06:25:10 PM
...a fundamental problem with these crash prone roundabouts that can’t be fixed...

In many cases, that problem is the self-centered driver. The ones in a hurry, distracted, and like to make their own traffic rules. You can't just look at the sheer number of crashes alone. You have to look at the type/cause of crash, and the majority of the time it's been due to failure to yield or improper lane usage. If there was a way to accurately track near-misses, I bet the larger roundabouts aren't any better.

The majority of crashes at signalized intersections are due to driver error.
The majority of crashes at modern roundabouts are due to driver error. 

The very first post in this thread has a link to SEMCOG crash data for the roundabout at State & Ellsworth in Ann Arbor.  Most of the crashes were due to failure to yield (angle) and improper lane usage (sideswipe same).  The 3 years before the roundabout, the intersection averaged 18 crashes a year.  The first year after the roundabout, there were 170 crashes.  Can the roundabout at State & Ellsworth be considered a success because the majority of the 170 crashes was due to driver error?  I don't think so.

You missed the point entirely. Where is there claim that either was a success? In reducing/eliminating fatalities, maybe. Back to the point I was trying to make...Increases in education and enforcement may be the better solution in many modern roundabout cases. You seem to hang your hat solely on the size hypothesis. Size of the roundabout will not solve the overly aggressive driver nor the ill-informed. All it does is give them more room to screw up and potentially at a higher speed.

Secondly, design philosophies are continually evolving with modern roundabouts. As you have even noted, spiral designs have changed in the past 5-10 years, as have theories on radial vs. offset approach design and limiting sight on the approach. Subtle geometric modifications can have a big impact on how a roundabout operates, without necessarily changing the ICD. Am I saying all roundabouts have an appropriate ICD? No. Some are undersized, others are oversized. Some are victim to poor initial design (fast-path speeds, entry radii, etc.), others are victim to not having the design knowledge we have today. Many are victim to the site's constraints. There is no one-size-fits-all solution. Bigger/smaller isn't always better.
Title: Re: Crash prone 'modern roundabouts'
Post by: iBallasticwolf2 on July 07, 2015, 06:39:11 PM
Larger roundabouts may be safer assuming the entry angles of the roundabout are designed properly and circulating speeds remain low.  Consider the following scenario.  CAR A enters the roundabout mistakenly believing CAR B is about to exit.  Would u want CAR B to take 1.7 seconds or 3.4 seconds to travel the blue path?  More reaction time is a good thing!

95 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test4_zpshnyyiesp.jpg)

160 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test3_zpscdfdzp4h.jpg)

You make the assumption that vehicle B will be traveling the same speed in both scenarios. The larger the circle, the faster vehicle B can comfortably travel. The faster vehicle B is traveling, the harder it is for vehicle A to judge the gap.

In that case the speed limit on the roundabout would have to be strictly enforced to make sure the drivers don't go faster. So post speed limit signs all over the roundabout.
Also inform drivers better. Alot of drivers are aggressive or ill-informed. There should be very good guidance for what drivers are supposed to do in a roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 08, 2015, 10:40:53 AM
You make the assumption that vehicle B will be traveling the same speed in both scenarios. The larger the circle, the faster vehicle B can comfortably travel. The faster vehicle B is traveling, the harder it is for vehicle A to judge the gap.
The circulating speed of the 160 ft diameter roundabout would have to be twice as fast as the circulating speed of the 95 ft diameter roundabout before the gap time would be equal.  The reality is drivers aren’t traveling twice as fast in the 160 ft diameter roundabout.  Don’t ignore the benefits larger diameters may have just because the circulating speeds might be 2-3 mph faster.

Back to the point I was trying to make...Increases in education and enforcement may be the better solution in many modern roundabout cases. You seem to hang your hat solely on the size hypothesis. Size of the roundabout will not solve the overly aggressive driver nor the ill-informed. All it does is give them more room to screw up and potentially at a higher speed.
Aggressive, ill-informed drivers are present at both large and small diameter roundabouts.  Improved driver education is great, but it doesn’t change the fact that smaller diameter roundabouts, based on the crash data, are more accident prone than larger ones.

Secondly, design philosophies are continually evolving with modern roundabouts. As you have even noted, spiral designs have changed in the past 5-10 years, as have theories on radial vs. offset approach design and limiting sight on the approach. Subtle geometric modifications can have a big impact on how a roundabout operates, without necessarily changing the ICD. Am I saying all roundabouts have an appropriate ICD? No. Some are undersized, others are oversized. Some are victim to poor initial design (fast-path speeds, entry radii, etc.), others are victim to not having the design knowledge we have today. Many are victim to the site's constraints. There is no one-size-fits-all solution. Bigger/smaller isn't always better.
Crash data is a good indicator to what design elements are working and which ones could be improved.  I’m sure there are ways to improve the crash rate of roundabouts with small ICD’s and designers have had two decades to tweak them.  Ultimately, the lessons learned at these crash prone roundabouts with small ICDs can be applied to the larger roundabouts to make them as safe as possible.  Size isn’t the only factor to look at, but it does appear to be a key factor.

The fact is State & Ellsworth is a roundabout with a 100 ft central island diameter and had 170 crashes the first year of operation.  What’s the fix?  Other larger diameter roundabouts in SE Michigan didn't see anywhere close to that number of crashes the first year of operation.  Can you really just put the bulk of the blame on ill-informed drivers?  Maybe, just maybe, it's too small.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 08, 2015, 11:08:56 AM
You make the assumption that vehicle B will be traveling the same speed in both scenarios. The larger the circle, the faster vehicle B can comfortably travel. The faster vehicle B is traveling, the harder it is for vehicle A to judge the gap.
The circulating speed of the 160 ft diameter roundabout would have to be twice as fast as the circulating speed of the 95 ft diameter roundabout before the gap time would be equal.  The reality is drivers aren’t traveling twice as fast in the 160 ft diameter roundabout.  Don’t ignore the benefits larger diameters may have just because the circulating speeds might be 2-3 mph faster.
I'm not ignoring the possible benefits; I am trying to look at this issue objectively from all sides.

Size isn’t the only factor to look at, but it does appear to be a key factor.
Something I can agree with, although being a key factor is a matter of semantics. Until the sight to the left on entry, circulating sight, entry radii, and fastest-paths (among other design considerations) are also compared and analyzed for the problematic roundabouts, the ICD is still just a plausible theory. There are many small ICD multilane roundabouts that have not had the PDO-crash growth that some of the ones mentioned in this thread have.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 08, 2015, 12:01:36 PM
There are many small ICD multilane roundabouts that have not had the PDO-crash growth that some of the ones mentioned in this thread have.
There really aren’t that many 2x2 roundabouts that haven’t been mentioned in this thread.  I attempted to query out the major 2x2 roundabouts in America and looked up crash data for as many as I could (found crash data for 14 of 40).  The best performing roundabout with a central island diameter of 100 feet or less still had a 300% increase in crashes.

There was a 300%-1400% increase in crashes at roundabouts with central island diameters of 100 feet or less.  There was a 36%-318% increase in crashes at roundabouts with central island diameters between 120 and 170 feet.  The worst performing large diameter roundabout was almost as good as the best performing small diameter roundabout.

Sure, you may be able to find an aesthetic 2x2 roundabout in a subdivision that hasn't seen an increase in crashes, but that really isn't the focus.  If you have crash data on major 2x2 roundabouts that I don’t, by all means share it with the rest of us. 

Here is a list of 40 multi-lane roundabouts that I think could be meaningful to this conversation.  This was queried from a database of over 5,100 modern roundabouts.  This was the criteria used to query out the list:

-roundabouts constructed within the last 10 years
-all approaches have 2 entry lanes
-roundabouts have 4-legs
-main & side streets are major state or county routes (ie. likely high AADT roundabouts)
-interchange roundabouts (and frontage road roundabouts) not included

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBtest_zpsbkjmf4ri.png)

Now the hard part is finding accurate before/after crash data to make any type of analysis.  Here is a google KMZ file that includes the 40 roundabouts in the chart above:

http://www.mediafire.com/download/cd570rarros2c3g/Multi-Lane+Roundabouts+%28with+high+AADT%29.kmz

In a previous post, I queried out 40 multi-lane roundabouts that have 2-entry lanes for all 4-legs (ie. the roundabouts in America that likely have the highest traffic volumes).  I’ve tracked down before/after crash data for 14 of them.  The excel file includes data links to articles/publications where the data was obtained.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBDATASummary_zpsg7upbybr.png)
http://www.mediafire.com/view/p0u5ovrupr0175m/Multi-lane_roundabout_crashes.xlsx

The takeaway is that smaller roundabouts seem to be more accident prone than larger roundabouts.  Would there have been 171 crashes at State & Ellsworth if the roundabout was constructed with a central island diameter of 140’ as opposed to 100’?  This thread wasn't meant to bash roundabouts but to discuss ways to reduce the crash frequency at the highest AADT roundabouts.  My thought is make them just a little bit bigger.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on July 08, 2015, 12:13:40 PM
Are the 3-2-1, 1-2-3 columns years before and after?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 08, 2015, 12:35:08 PM
Are the 3-2-1, 1-2-3 columns years before and after?

Yes.  3-2-1 represents 3 years before, 2 years before, 1 year before.  1-2-3 represents 1 year after, 2 years after, 3 years after.  The year of construction is not included.  The cells highlighted in grey are average crashes over multiple years.  If you open the excel file it provides links where the crash data was obtained.

http://www.mediafire.com/view/p0u5ovrupr0175m/Multi-lane_roundabout_crashes.xlsx
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on July 08, 2015, 01:10:58 PM
Interesting that the crashes for the New Scotland/NY 85/NY 140 roundabout are only one year before and after.  As I've said before, the most mindboggling thing for me going through there are the people that think they can continue to go around the roundabout in the right lane and don't look when they essentially turn left to do so.  I'd bet that kind of thing accounts for a lot of the crashes in the year after the roundabout was built.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 08, 2015, 01:56:55 PM
Interesting that the crashes for the New Scotland/NY 85/NY 140 roundabout are only one year before and after.  As I've said before, the most mindboggling thing more me going through there are the people that think they can continue to go around the roundabout in the right lane and don't look when they essentially turn left to do so.  I'd bet that kind of thing accounts for a lot of the crashes in the year after the roundabout was built.

The roundabout at New Scotland/NY 85/NY 140 is one of the worst performing roundabouts that has a central island diameter between 120-170 feet.  The faded spiral markings could definitely be a contributing factor to the high crash rate seen at this roundabout and has been discussed previously in this thread (the smaller diameter roundabout in Malta, NY also has painted spiral markings).  By the way, I believe the crash data is average crashes over multiple years but the article (linked in the excel file) misrepresented the data to be from only one year before and after. 

Bethlehem, NY (New Scotland Road and Route 140)
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/NYRB_zpsmnpyxdmi.png)

Malta, NY (Route 9, Route 67 and Dunning Street)
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/NYRBMalta_zpsifwwmbgh.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 08, 2015, 02:18:43 PM
There are many small ICD multilane roundabouts that have not had the PDO-crash growth that some of the ones mentioned in this thread have.
There really aren’t that many 2x2 roundabouts that haven’t been mentioned in this thread.  I attempted to query out the major 2x2 roundabouts in America and looked up crash data for as many as I could (found crash data for 14 of 40).
Forty? That's it? You're being to limited in your search and you indirectly admit that you don't have enough accurate crash data for all the ones you do list.

Sure, you may be able to find an aesthetic 2x2 roundabout in a subdivision that hasn't seen an increase in crashes.
There is no such thing. You don't build a multilane roundabout just because it looks pretty.

Here is a list of 40 multi-lane roundabouts that I think could be meaningful to this conversation.  This was queried from a database of over 5,100 modern roundabouts.  This was the criteria used to query out the list:

-roundabouts constructed within the last 10 years    Reasonable
-all approaches have 2 entry lanes    Why exclude roundabouts that may have one or two legs with a single lane entry?
-roundabouts have 4-legs    Exactly 4 or >=4? Why exclude 3-leg 2x2 roundabouts?
-main & side streets are major state or county routes (ie. likely high AADT roundabouts)    Not an accurate assumption...while likely, there still are a number that are solely local arterial roads, and not numbered/lettered routes. Ex: Thompson/Lein/Zeier, Madison (https://www.google.com/maps/@43.121535,-89.299519,18z), Thompson/Main, Sun Prairie (https://www.google.com/maps/@43.1764051,-89.254479,19z)
-interchange roundabouts (and frontage road roundabouts) not included    Why? Just because interchange roundabouts don't have 4 complete approaches?
As I said above, you're being too limiting in your search. Some might say you're cherry-picking data. The lack of complete crash data skews the whole process. I could list many multilane roundabouts that you haven't mentioned, but they would/should get thrown-out because the intersection did not exist before the roundabout, thus there is no before period to compare to.

This is going in nothing but circles (pun not intended). I tried to find common ground in your reasonable query on roundabout size, but you are blinded into focusing solely on size. Is size a factor? Yes. Does it deserve more scientifically-acceptable research? Most certainly. Is it the only factor where crashes are a problem? No. Roundabout design isn't that simplistic. You started a discussion on "crash-prone 'modern roundabouts'", when a more accurate subject would be 'why modern roundabouts are too small'.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on July 08, 2015, 02:27:53 PM
I drive through that roundabout a couple of times a week and can say with certainty that crashes are not due to faded pavement markings.  The thing is still well-marked and even signed.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 08, 2015, 03:04:27 PM
I drive through that roundabout a couple of times a week and can say with certainty that crashes are not due to faded pavement markings.  The thing is still well-marked and even signed.

Even with perfectly visible pavement markings, drivers are going to cheat.  The driver in the blue SUV is asking themselves "is the silver Honda in the outside or inside lane?"  Let's hope they don't guess wrong. 

Hell, i'd encourage you to take video of the Bethlehem roundabout and post it online so we can see for ourselves if improper lane use is a problem at this roundabout.  It wouldn't be that hard to do.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/SVMalta_zpspdoii1ub.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on July 08, 2015, 03:07:38 PM
Heh.  Like I said, the crashes in the 1st year afterwards are probably due to people turning left from the right lane and I'd bet the frequency of lane misuse has dropped -- although I still witness it from time-to-time.

Might make that video when I get a chance.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 08, 2015, 03:29:03 PM
Heh.  Like I said, the crashes in the 1st year afterwards are probably due to people turning left from the right lane and I'd bet the frequency of lane misuse has dropped -- although I still witness it from time-to-time.

Might make that video when I get a chance.

Here’s the next best thing to a video.  Here are streetview images tracking a vehicle through the roundabout in Malta, NY (which has an identical spiral design to the roundabout in Bethlehem NY).  At some point the blue SUV may think it’s safe to enter the roundabout (since the silver Honda is in the inside left turn only lane).
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test1_zps4crezouf.jpg)
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test2_zpszpwpcomn.jpg)
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test3_zps2kf2y7bb.jpg)
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test4_zpsmeqbau38.jpg)
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/test5_zpsifja6ucx.jpg)
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/test6_zpslnjnyuzg.jpg)

The silver Honda is cheating their way through the roundabout.

Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on July 08, 2015, 04:22:46 PM
Most of the crashes were in year one... the year the pavement markings almost certainly weren't faded. Hence faded lines don't, and can't, explain jack.

As for the silver Honda... dude is like 1 foot across the line for maybe 20 feet without endangering any other traffic. People drift across lane lines all the time. Give it a rest.

Free advice from one data scientist: stop torturing the data to fit an agenda.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 08, 2015, 06:02:15 PM
Most of the crashes were in year one... the year the pavement markings almost certainly weren't faded. Hence faded lines don't, and can't, explain jack.

I don't have year by year crash data for the NY roundabout.  How do u know that the majority of crashes happened in year one?

As for the silver Honda... dude is like 1 foot across the line for maybe 20 feet without endangering any other traffic. People drift across lane lines all the time. Give it a rest.

Dude is entirely in the inner lane in the 3rd picture.  I only had streetview (not many examples to pick from) so sorry if i couldn't find a better example of the scenario

Free advice from one data scientist: stop torturing the data to fit an agenda.

I'm just looking for trends.  The crash data shows that there are fewer crashes at larger diameter roundabouts.  Therefore, I'm in favor of larger roundabouts.  If the data had shown that there are fewer crashes at smaller diameter roundabouts, then i would be in favor of smaller diameter roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on July 08, 2015, 07:24:27 PM
Most of the crashes were in year one... the year the pavement markings almost certainly weren't faded. Hence faded lines don't, and can't, explain jack.

I don't have year by year crash data for the NY roundabout.  How do u know that the majority of crashes happened in year one?


Eh...your percentage increases treats them as if you did have year-to-year.  Can't have it both ways.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 08, 2015, 07:26:16 PM
The crash data shows that there are fewer crashes at larger diameter roundabouts.  Therefore, I'm in favor of larger roundabouts.  If the data had shown that there are fewer crashes at smaller diameter roundabouts, then i would be in favor of smaller diameter roundabouts.

But the data is only representative of the few roundabouts you can find data for. I don't think making such large generalizations is a good idea without a significant amount of data.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 08, 2015, 07:53:01 PM
Most of the crashes were in year one... the year the pavement markings almost certainly weren't faded. Hence faded lines don't, and can't, explain jack.

I don't have year by year crash data for the NY roundabout.  How do u know that the majority of crashes happened in year one?


Eh...your percentage increases treats them as if you did have year-to-year.  Can't have it both ways.

Cells highlighted in grey are average crashes over multiple years.  The before and after crash data cells for the Bethlehem, NY and Malta, NY roundabouts are highlighted in grey.  I'm not trying to fool anyone.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 08, 2015, 08:25:47 PM
The crash data shows that there are fewer crashes at larger diameter roundabouts.  Therefore, I'm in favor of larger roundabouts.  If the data had shown that there are fewer crashes at smaller diameter roundabouts, then i would be in favor of smaller diameter roundabouts.

But the data is only representative of the few roundabouts you can find data for. I don't think making such large generalizations is a good idea without a significant amount of data.

The Insurance Institute for Highway Safety study only evaluated 9 multi-lane roundabouts.  This 15 year old study is routinely cited in roundabout articles and is the go to source when it comes to roundabout safety statistics.  I’m evaluating the safety performance of 14 multi-lane roundabouts.  The amount of data being evaluated is not insignificant.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on July 08, 2015, 09:08:15 PM
Most of the crashes were in year one... the year the pavement markings almost certainly weren't faded. Hence faded lines don't, and can't, explain jack.

I don't have year by year crash data for the NY roundabout.  How do u know that the majority of crashes happened in year one?


Eh...your percentage increases treats them as if you did have year-to-year.  Can't have it both ways.

Cells highlighted in grey are average crashes over multiple years.

I'm going to have call baloney on this repeated assertion as well regarding the New Scotland roundabout.  You're saying that the average in the first three years was 9.6 per year and then the average in the three years afterwards was 38.3. per year.

That's total baloney.  In essence, you're saying that there was at least one incident in the roundabout every 10 days for three years after it was built. I highly suspect that you have warped the data into something for which it was not intended.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 08, 2015, 09:40:36 PM
I'm going to have call baloney on this repeated assertion as well regarding the New Scotland roundabout.  You're saying that the average in the first three years was 9.6 per year and then the average in the three years afterwards was 38.3. per year.

That's total baloney.  In essence, you're saying that there was at least one incident in the roundabout every 10 days for three years after it was built. I highly suspect that you have warped the data into something for which it was not intended.


I don't understand what is so hard to believe.  Does 38 crashes a year sound too high to you?  To put it into perspective, there are over 50 intersections in SE Michigan that have averaged at least 38 crashes a year.

http://semcog.org/Data-and-Maps/High-Frequency-Crash-Locations

Title: Re: Crash prone 'modern roundabouts'
Post by: roadfro on July 08, 2015, 10:22:16 PM
Here is a list of 40 multi-lane roundabouts that I think could be meaningful to this conversation.  This was queried from a database of over 5,100 modern roundabouts.  This was the criteria used to query out the list:

-roundabouts constructed within the last 10 years    Reasonable
-all approaches have 2 entry lanes    Why exclude roundabouts that may have one or two legs with a single lane entry?
-roundabouts have 4-legs    Exactly 4 or >=4? Why exclude 3-leg 2x2 roundabouts?
-main & side streets are major state or county routes (ie. likely high AADT roundabouts)    Not an accurate assumption...while likely, there still are a number that are solely local arterial roads, and not numbered/lettered routes. Ex: Thompson/Lein/Zeier, Madison (https://www.google.com/maps/@43.121535,-89.299519,18z), Thompson/Main, Sun Prairie (https://www.google.com/maps/@43.1764051,-89.254479,19z)
-interchange roundabouts (and frontage road roundabouts) not included    Why? Just because interchange roundabouts don't have 4 complete approaches?
As I said above, you're being too limiting in your search. Some might say you're cherry-picking data. The lack of complete crash data skews the whole process. I could list many multilane roundabouts that you haven't mentioned, but they would/should get thrown-out because the intersection did not exist before the roundabout, thus there is no before period to compare to.

This is going in nothing but circles (pun not intended). I tried to find common ground in your reasonable query on roundabout size, but you are blinded into focusing solely on size. Is size a factor? Yes. Does it deserve more scientifically-acceptable research? Most certainly. Is it the only factor where crashes are a problem? No. Roundabout design isn't that simplistic. You started a discussion on "crash-prone 'modern roundabouts'", when a more accurate subject would be 'why modern roundabouts are too small'.

DaBigE, I think some of your assumptions about tradephoric's data and filtering criteria are a little unreasonable.

In order to effectively analyze roundabouts from various locations to draw some general conclusions, you have to limit the data in some way in order to have the analysis make sense and reduce effects from other variables. One way to do that is looking for substantially similar conditions at various sites. Limiting the sample to 4-leg roundabouts with double lane approaches on all sides makes valid sense in this data analysis–otherwise, you're not making an "apples to apples" comparison and can not make the same generalizations because other design factors can influence the data. (Although I would agree that the limitation to include just state/county routes isn't necessarily a good one, but I understand the rationale in trying to find roundabouts with similar AADTs. Finding that data in relation to crash data for specific sites might not be an easy endeavor for armchair/hobbyist analysis purposes.)

When you have raw data like this in a tabular format, with similar site characteristics, any good data analysis would attempt to find patterns in said data. Tradephoric found one possible trend between a possible variable (inscribed circle diameter) and accident rates, and has commented on this specifically. I don't think we could say with any reasonable certainty that there is a direct correlation without more analysis, but it is a plausible theory worth further examination (possibly worthy of a civil/traffic engineering journal article). And by no means is ICD the only possible factor influencing the accident rates at these sites–but to examine multiple possible factors independent of others would require much more research and site visits.; however, it is one that is easy to examine without making a detailed site visit.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on July 09, 2015, 12:24:04 AM
I'm going to have call baloney on this repeated assertion as well regarding the New Scotland roundabout.  You're saying that the average in the first three years was 9.6 per year and then the average in the three years afterwards was 38.3. per year.

That's total baloney.  In essence, you're saying that there was at least one incident in the roundabout every 10 days for three years after it was built. I highly suspect that you have warped the data into something for which it was not intended.


I don't understand what is so hard to believe.  Does 38 crashes a year sound too high to you?  To put it into perspective, there are over 50 intersections in SE Michigan that have averaged at least 38 crashes a year.

http://semcog.org/Data-and-Maps/High-Frequency-Crash-Locations



Yep.  38 crashes a year at that roundabout in the three years since it was built does sound far too high.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 09, 2015, 12:29:57 AM
DaBigE, I think some of your assumptions about tradephoric's data and filtering criteria are a little unreasonable.
And I respectfully disagree. The initial discussion was based on multilane roundabouts in general, not specifically 2x2 roundabouts. In the end, we've mainly been discussing entering and exiting crashes, which don't tend to discriminate very much between a 2x2 or a 1x2 roundabout; as long as there is some multilane component, similar vehicular conflicts can and will exist.

I don't think there is anyone here that disagrees that ICD may play a role or that there is a pattern at many multilane roundabouts; what many of us disagree with is making a broad generalization on very limited data. That said, it is definitely worth looking into further, but from a more detailed approach. I think the size discussion has gone about as far as it can on an enthusiast level. The discussion may even be completely moot, as the recommended range of multilane roundabout size is already greater than the 100-ft threshold of this discussion (Exhibit 6-9, NCHRP Report 672). Many of the roundabouts being discussed likely made smaller because of design concessions/site constraints (e.g., costly right-of-way acquisition, some unmovable feature, etc.).

For similar reasons, I also disagree with the IIHS study being promoted any further because, as tradephoric also pointed out, it was done on fewer roundabouts and over 15 years ago. A lot has changed within the past 5 years, let alone 15. Similarly, as I've said earlier, many of us (professional colleagues included), have fundamental issues with the studies WisDOT has carried out as well.

Analyzing roundabouts is not an easy task, whether it's crash data or capacity. There is a lot of disagreement in the design world. This is one reason why I have been harping on the danger of some of the comparisons of older roundabouts that have not been touched since they were first constructed a decade ago. Design philosophies are still evolving, from a forecasting perspective as well. From that point alone, it will be very hard to ever get an apples-to-apples comparison. Throw in different driving characteristics in the various areas of the country and the similarities disappear even faster.

Looking into the future of multilane roundabouts, some new experiments are gaining traction in a few locations in Texas and a couple in Minnesota: non-striped or limited-striping circulatory roadways. This will blur the analysis picture even more.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 09, 2015, 01:11:17 AM
Looking into the future of multilane roundabouts, some new experiments are gaining traction in a few locations in Texas and a couple in Minnesota: non-striped or limited-striping circulatory roadways. This will blur the analysis picture even more.

I quite like this idea. I've always thought that we go overboard with signage and pavement markings. Do you have any links to these roundabouts?
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 09, 2015, 01:18:37 AM
Looking into the future of multilane roundabouts, some new experiments are gaining traction in a few locations in Texas and a couple in Minnesota: non-striped or limited-striping circulatory roadways. This will blur the analysis picture even more.

I quite like this idea. I've always thought that we go overboard with signage and pavement markings. Do you have any links to these roundabouts?

Not yet. Most are either still in final planning phases or are just going to construction.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on July 09, 2015, 10:30:02 AM
Non-striped circulatory roadways are standard in the UK for unsignalized, multilane roundabouts. For what it's worth...
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on July 09, 2015, 10:58:22 AM
Looking into the future of multilane roundabouts, some new experiments are gaining traction in a few locations in Texas and a couple in Minnesota: non-striped or limited-striping circulatory roadways. This will blur the analysis picture even more.

I quite like this idea. I've always thought that we go overboard with signage and pavement markings. Do you have any links to these roundabouts?

Look up nearly any traditional NJ Traffic Circle, and this is what they are.

Yes, people that should stay left drift to the right, and those that should stay further to the right drift left.  Occasionally, someone from the left exits the circle.  Horns honk.  Words are uttered (mostly behind closed windows).  But overall, very few accidents.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 09, 2015, 11:13:26 AM
Looking into the future of multilane roundabouts, some new experiments are gaining traction in a few locations in Texas and a couple in Minnesota: non-striped or limited-striping circulatory roadways. This will blur the analysis picture even more.

I quite like this idea. I've always thought that we go overboard with signage and pavement markings. Do you have any links to these roundabouts?

Look up nearly any traditional NJ Traffic Circle, and this is what they are.

Yes, people that should stay left drift to the right, and those that should stay further to the right drift left.  Occasionally, someone from the left exits the circle.  Horns honk.  Words are uttered (mostly behind closed windows).  But overall, very few accidents.

When a non-striped traffic circle in Augusta, Maine was converted to a modern roundabout, it saw a 60% drop in crashes (the size of the circle remained the same).  I don't think there is any consensus that non-striped roundabouts would be more effective then striped roundabouts.

http://www.pressherald.com/2013/04/17/terms-for-traffic-circles-cause-confusion_2013-04-18/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 09, 2015, 11:37:08 AM
The initial discussion was based on multilane roundabouts in general, not specifically 2x2 roundabouts.

The initial discussion was regarding crash prone modern roundabouts.  DaBigE, you questioned why I didn’t include interchange roundabouts.  Based on the WisDOT studies it became clear that interchange roundabouts perform better than non-interchange roundabouts.  Nearly every interchange roundabout in the WisDOT studies saw a drop in crash rate.  You’ve made it known that you have fundamental issues with the WisDOT studies, but I doubt the studies were based on fabricated crash data.  The best performing multi-lane roundabouts in SE Michigan also happen to be at interchange roundabouts.  Logically, it makes sense why interchange roundabouts may have a lower crash rate then other multi-lane roundabouts.  Some legs only service entry or exiting traffic and it could be argued the turning movements are more predictable (certain turning movements won’t be that heavy).  In general, interchange roundabouts just don’t appear to be that accident prone.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 09, 2015, 12:20:00 PM
The initial discussion was based on multilane roundabouts in general, not specifically 2x2 roundabouts.

The initial discussion was regarding crash prone modern roundabouts.  DaBigE, you questioned why I didn’t include interchange roundabouts.  Based on the WisDOT studies it became clear that interchange roundabouts perform better than non-interchange roundabouts.  Nearly every interchange roundabout in the WisDOT studies saw a drop in crash rate.  You’ve made it known that you have fundamental issues with the WisDOT studies, but I doubt the studies were based on fabricated crash data.  The best performing multi-lane roundabouts in SE Michigan also happen to be at interchange roundabouts.  Logically, it makes sense why interchange roundabouts may have a lower crash rate then other multi-lane roundabouts.  Some legs only service entry or exiting traffic and it could be argued the turning movements are more predictable (certain turning movements won’t be that heavy).  In general, interchange roundabouts just don’t appear to be that accident prone.

First, no one is claiming that the studies are coming from "fabricated crash data". The studies' flaws had more to do with site selection. Secondly, if you're trying to prove whether size has a significant contributing factor, why throw out roundabouts with lower crash rates? In order to make a generalization such as size being a "key factor", you need to look at all the data, not just the ones that have the best chance of proving your point. Maybe the ones you chose not to include also help prove a larger size theory.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 09, 2015, 12:23:44 PM
Non-striped circulatory roadways are standard in the UK for unsignalized, multilane roundabouts. For what it's worth...

That is one of the reasons why it is being tried in the US, in addition to less striping maintenance. There is a design theory that stripes should be applied to increase capacity rather than to keep people in-lane. Lack of circulatory striping also removes the confusion when a large vehicle is moving through, as there are no lane lines to have to straddle.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 09, 2015, 02:11:06 PM
First, no one is claiming that the studies are coming from "fabricated crash data". The studies' flaws had more to do with site selection.

I was curious what you took issue with regarding the WisDOT studies.  Some roundabout proponents may attempt to discredit any study that shows roundabouts in a negative light.  It feels like there's a little bit of “let’s shoot the messenger”  with these WisDOT studies.

Secondly, if you're trying to prove whether size has a significant contributing factor, why throw out roundabouts with lower crash rates? In order to make a generalization such as size being a "key factor", you need to look at all the data, not just the ones that have the best chance of proving your point. Maybe the ones you chose not to include also help prove a larger size theory.

More data is not always useful.  Here are some low volume 2x2 roundabouts that services subdivisions, commercial office complexes, schools, etc.  Would crash data at these roundabouts (which might average 0.6 crashes/year) be useful in this discussion?  It would become an apples to bananas comparison.   
 
https://www.google.com/maps/@39.22989,-77.2528,18z/data=!3m1!1e3
https://www.google.com/maps/@35.84866,-86.35948,365m/data=!3m1!1e3
https://www.google.com/maps/@30.10538,-81.4157,19z/data=!3m1!1e3
https://www.google.com/maps/@38.9684442,-76.9233194,117m/data=!3m1!1e3
https://www.google.com/maps/@38.9383773,-104.734292,98m/data=!3m1!1e3
Title: Re: Crash prone 'modern roundabouts'
Post by: johndoe on July 09, 2015, 08:08:27 PM
... increase the central island diameter of the roundabout from 95 feet to 150 feet.
Sorry if this has been covered...but is there a reason you don't do your analysis based upon the inscribed diameter?  I ask since that's usually how they're usually laid out (in my experience).

Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 09, 2015, 08:21:11 PM
First, no one is claiming that the studies are coming from "fabricated crash data". The studies' flaws had more to do with site selection.

I was curious what you took issue with regarding the WisDOT studies.  Some roundabout proponents may attempt to discredit any study that shows roundabouts in a negative light.  It feels like there's a little bit of “let’s shoot the messenger” with these WisDOT studies.
And I'm not sensing that same vibe. Sure, there's a few hell-bent on 'roundabouts everywhere' just like there's similar chest-beaters for traffic signals or DDIs. Most in the design community are taking these studies and trying to find why are these crashes happening, not why are these studies wrong. However, we want to work with the most accurate and complete data we can. Most of us don't get paid based on the number of 'xyz' intersection type are constructed.

In the interest of preventing future false assumptions, I am not one of those roundabout proponents, rather I am a proponent of using the proper tool for the proper location. Roundabouts won't work everywhere, nor will traffic signals or cloverleaf interchanges. I'm just as interested in finding out why crashes are higher in some places and not others. That's not to say there aren't earmarked projects, like many HSIP-funded intersection projects.

More data is not always useful.
The only time more data is not useful is if the data is flawed, incorrect, or objectively erroneous data. In any case, bad data should be objectively removed before attempting any formal conclusions. You don't establish reliable trend lines based on only a little data. That is one of the reasons why LOS analysis equations for roundabout capacity prediction are continually being adjusted.

Here are some low volume 2x2 roundabouts that services subdivisions, commercial office complexes, schools, etc.  Would crash data at these roundabouts (which might average 0.6 crashes/year) be useful in this discussion?  It would become an apples to bananas comparison.   
 
https://www.google.com/maps/@39.22989,-77.2528,18z/data=!3m1!1e3
https://www.google.com/maps/@35.84866,-86.35948,365m/data=!3m1!1e3
https://www.google.com/maps/@30.10538,-81.4157,19z/data=!3m1!1e3
https://www.google.com/maps/@38.9684442,-76.9233194,117m/data=!3m1!1e3
https://www.google.com/maps/@38.9383773,-104.734292,98m/data=!3m1!1e3
You answered your own question by saying they are low-volume. Only if an adjustment is made to correct for volume disparities would this data be useful for anything but analyzing low-volume roundabouts. Your original list of qualifications was looking for multilane roundabouts of a certain AADT. All I am saying is that intersections of similar AADTs shouldn't be omitted in this case just because they have a low crash rate (referring to the afore-mentioned interchange or frontage road roundabouts). Maybe their size helps prove a size/crash relationship.

On a somewhat unrelated topic, I do see some poor yield line placement in a few of your latest examples.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 09, 2015, 08:27:32 PM
... increase the central island diameter of the roundabout from 95 feet to 150 feet.
Sorry if this has been covered...but is there a reason you don't do your analysis based upon the inscribed diameter?  I ask since that's usually how they're usually laid out (in my experience).
That is correct. Central island size is generally a byproduct from the ICD and circulatory lane width(s), in addition to possibly allowing for future staged capacity enhancements.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on July 10, 2015, 12:33:30 AM
All I am saying is that intersections of similar AADTs shouldn't be omitted in this case just because they have a low crash rate (referring to the afore-mentioned interchange or frontage road roundabouts). Maybe their size helps prove a size/crash relationship.

Indeed. This is what is referred to as "selecting on the dependent variable." You can't (validly) conclude that roundabouts of a certain type with a certain AADT or above have a high crash rate if you omit all the roundabouts of the same type and AADT that have zero or low crash rates.

What you could validly do is compare the characteristics of roundabouts that have high crash rates with those with low crash rates (but similar AADT and lane counts) to identify if there are meaningful patterns that distinguish the high-crash ones from low-crash ones (for example, entry angle, striping design, signage, use of traffic calming treatments like rumble stripes, signed speed limits, advisory speed plaques, lighting, landscaping...).
Title: Re: Crash prone 'modern roundabouts'
Post by: ScottRAB on July 10, 2015, 03:50:18 PM
Look up nearly any traditional NJ Traffic Circle, and this is what they are.

not sure if I got the right attribution:
Modern roundabouts are traffic circles, but traffic circles are not modern roundabouts.
   Many people confuse other and older styles of circular intersections with modern roundabouts.  East coast rotaries, large multi-lane traffic circles (Arc D’Triomphe, Dupont Circle), and small neighborhood traffic circles are not modern roundabouts.   If you want to see the difference between a traffic circle, a rotary (UK roundabout) and a modern roundabout (UK continental roundabout), go to http://tinyurl.com/kstate-RAB  to see pictures.   And here’s another site that shows the difference between an older rotary and a modern roundabout: http://tinyurl.com/bzf7qmg
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 14, 2015, 11:35:41 AM
Larger roundabouts may be safer assuming the entry angles of the roundabout are designed properly and circulating speeds remain low.  Consider the following scenario.  CAR A enters the roundabout mistakenly believing CAR B is about to exit.  Would u want CAR B to take 1.7 seconds or 3.4 seconds to travel the blue path?  More reaction time is a good thing!

95 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test4_zpshnyyiesp.jpg)

160 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test3_zpscdfdzp4h.jpg)

You make the assumption that vehicle B will be traveling the same speed in both scenarios. The larger the circle, the faster vehicle B can comfortably travel. The faster vehicle B is traveling, the harder it is for vehicle A to judge the gap.

Your general assumption that drivers feel more comfortable driving faster in larger circles is wrong.  The red min-van may feel comfortable traveling through this circle at 90 mph (in a straight line). 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/B93174221541-0_zpsega85sti.jpg)

Relating specifically to modern-roundabouts, the same type of straight line fastest path can occur.  Here’s an example of a small diameter modern-roundabout in Oconomowoc, Wisconsin where the fastest path through the roundabout is approaching a straight line.  I know it sounds counter-intuitive, but larger diameter roundabout can actually slow down the speeds of circulating traffic.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/fastestpath_zpskfw1ywq5.jpg)

The 160 ft diameter roundabout had a 48% increase in crashes whereas the 95 ft diameter roundabout had a 335% increase in crashes.  Is it possible that drivers at the 160 ft diameter roundabout can judge gaps in traffic better than the 95 diameter one and that is reflected in the crash data?
Title: Re: Crash prone 'modern roundabouts'
Post by: iBallasticwolf2 on July 14, 2015, 11:40:53 AM
Larger roundabouts may be safer assuming the entry angles of the roundabout are designed properly and circulating speeds remain low.  Consider the following scenario.  CAR A enters the roundabout mistakenly believing CAR B is about to exit.  Would u want CAR B to take 1.7 seconds or 3.4 seconds to travel the blue path?  More reaction time is a good thing!

95 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test4_zpshnyyiesp.jpg)

160 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test3_zpscdfdzp4h.jpg)

You make the assumption that vehicle B will be traveling the same speed in both scenarios. The larger the circle, the faster vehicle B can comfortably travel. The faster vehicle B is traveling, the harder it is for vehicle A to judge the gap.

Your general assumption that drivers feel more comfortable driving faster in larger circles is wrong.  The red min-van may feel comfortable traveling through this circle at 90 mph (in a straight line). 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/B93174221541-0_zpsega85sti.jpg)

Relating specifically to modern-roundabouts, the same type of straight line fastest path can occur.  Here’s an example of a small diameter modern-roundabout in Oconomowoc, Wisconsin where the fastest path through the roundabout is approaching a straight line.  I know it sounds counter-intuitive, but larger diameter roundabout can actually slow down the speeds of circulating traffic.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/fastestpath_zpskfw1ywq5.jpg)

The 160 ft diameter roundabout had a 48% increase in crashes whereas the 95 ft diameter roundabout had a 335% increase in crashes.  Is it possible that drivers at the 160 ft diameter roundabout can judge gaps in traffic better than the 95 diameter one and that is reflected in the crash data?

Assuming the vehicle decides to go the same speed in both roundabouts then there would be more time to judge a gap. I would assume the speed would be 15 mph.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 14, 2015, 02:00:06 PM
Larger roundabouts may be safer assuming the entry angles of the roundabout are designed properly and circulating speeds remain low.  Consider the following scenario.  CAR A enters the roundabout mistakenly believing CAR B is about to exit.  Would u want CAR B to take 1.7 seconds or 3.4 seconds to travel the blue path?  More reaction time is a good thing!

95 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test4_zpshnyyiesp.jpg)

160 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test3_zpscdfdzp4h.jpg)

You make the assumption that vehicle B will be traveling the same speed in both scenarios. The larger the circle, the faster vehicle B can comfortably travel. The faster vehicle B is traveling, the harder it is for vehicle A to judge the gap.

Your general assumption that drivers feel more comfortable driving faster in larger circles is wrong.  The red min-van may feel comfortable traveling through this circle at 90 mph (in a straight line). 
There was no assumption. Can doesn't mean they necessarily will, but the probability increases.



Relating specifically to modern-roundabouts, the same type of straight line fastest path can occur.  Here’s an example of a small diameter modern-roundabout in Oconomowoc, Wisconsin where the fastest path through the roundabout is approaching a straight line.  I know it sounds counter-intuitive, but larger diameter roundabout can actually slow down the speeds of circulating traffic.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/fastestpath_zpskfw1ywq5.jpg)

Thanks for helping prove my point by attempting to look at the fast path. Circle size is only part of the equation. The Oconomowoc roundabout also has some path overlap which typically leads to entering crashes as well. This example also shows what tight urban constraints can place on the desirable roundabout size. IIRC, they had to buy out the property in the NW corner. Any larger of a circle, and one or both of the gas stations would have to go as well.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 14, 2015, 07:59:21 PM
Thanks for helping prove my point by attempting to look at the fast path. Circle size is only part of the equation. The Oconomowoc roundabout also has some path overlap which typically leads to entering crashes as well. This example also shows what tight urban constraints can place on the desirable roundabout size. IIRC, they had to buy out the property in the NW corner. Any larger of a circle, and one or both of the gas stations would have to go as well.

If ROW constraints prevent the desired roundabout size from being constructed, maybe it shouldn’t be constructed to begin with.  A traffic signal at Ellsworth & State in Ann Arbor, Michigan that averages 16 crashes a year is a better alternative than a roundabout that experiences 170 crashes in a year.  A similar argument can be made for the roundabout at Auburn & Main in Rockford, Illinois (crashes increased 14X and had nearly 100 crashes in one year). 

Do you have a compelling reason why there has been a significant crash rate at these two roundabouts?  Can you cite a large diameter modern-roundabout that has had 100 crashes in one year?  The fact is the worst performing modern roundabouts have small central island diameters.  Nothing you say will change that fact.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 14, 2015, 09:40:28 PM
If ROW constraints prevent the desired roundabout size from being constructed, maybe it shouldn’t be constructed to begin with.  A traffic signal at Ellsworth & State in Ann Arbor, Michigan that averages 16 crashes a year is a better alternative than a roundabout that experiences 170 crashes in a year.  A similar argument can be made for the roundabout at Auburn & Main in Rockford, Illinois (crashes increased 14X and had nearly 100 crashes in one year).
And no signalized intersection, no interchange ramp design has ever had design compromises? Ever driven a curve that has an advisory speed lower than the speed limit? Design compromises were made in those cases, building a curve smaller than what the laws of physics dictate are safe. Years ago, this ramp (https://www.google.com/maps/dir/43.1346498,-89.2938965/43.1389994,-89.2933386/@43.1377673,-89.2931577,18z/data=!4m2!4m1!3e0) saw several overturns per year (IIRC, there were three that happened in the period of just a few months in one year). Should this interchange not have been constructed because the curves are tighter than desirable? ROW was a big consideration in that case as well. FWIW, the other similar ramps at the same interchange have had near-zero similar overturn incidents.   

Do you have a compelling reason why there has been a significant crash rate at these two roundabouts?  Can you cite a large diameter modern-roundabout that has had 100 crashes in one year?  The fact is the worst performing modern roundabouts have small central island diameters.  Nothing you say will change that fact.
And nothing I have said has disputed that fact. Please stop distorting my comments to fit your agenda. Have you investigated anything other than the size of the central island? What about lane width? As it's been pointed out, ICD is the proper way of classifying a roundabout's size, since the central island is a byproduct of the width of circulatory roadway and the number of circulating lanes. The Oconomowoc example you provided has many other deficiencies besides size (path overlap, fast path, entry deflection, using a mandatory right-turn lane within the regular approach when it should be a partial bypass at the very least...). Looking solely at size is lazy at best, foolish at worst. How many ways do I need to say it before it sinks in (the last time I'm going to say it)...
A roundabout's size MAY indeed be a factor in crashes, but needs additional in-depth study*, in addition to investigating other possible deficiencies.

* More detailed and scientific than can be achieved on this forum and are suitable for publishing in a venue such as a TRB or NCHRP paper.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 14, 2015, 11:30:17 PM
Have you investigated anything other than the size of the central island?

Fastest path:  The fastest path at small central island diameters approaches a straight line.  The Oconomowoc roundabout has a small central island diameter that exemplifies this concept.

Entry deflection angle: Small central island diameters have less pronounced entry deflection angles than larger central island diameter roundabouts.  Just imagine a small neighborhood traffic circle; the entry deflection angle is nearly non-existent. 

Painted spiral markings:  The New York roundabouts cited in this thread have painted spiral markings as opposed to the spiral being designed into the truck apron.  Interestingly, the larger 130’ diameter spiral roundabout in Bethlehem outperformed the smaller 103’ diameter spiral roundabout in Malta (299% vs. 445% increase in crashes respectively). 

Non-interchange vs. interchange roundabouts:  Interchange roundabouts appear to be less accident prone than non-interchange roundabouts.  Some legs at an interchange roundabout only service entry or exiting traffic and it could be argued the turning movements are more predictable (certain turning movements won’t be as heavy).  A pretty strong trend can be seen when looking through the Wisconsin Phase 1 & Phase 2 studies. 

Reducing circulating lanes:  The following crash prone roundabouts have reduced the number of circulating lanes in an attempt to improve safety. 
-14th Street & Superior in Lincoln, Nebraska (3x2 reduced to 2x2)
-Maple & Drake in Farmington Hills, Michigan (3x2 reduced to 2x2)
-Maple & Farmington in Farmington Hills, Michigan (3x2 reduced to 2x2)
-Homer Watson Boulevard and Block Line Road in Kitchener, Ontario (3x2 reduced to 2x2)
-Bailey & Radio in Woodbury, Minnesota (2x2 reduced to 2x1)
-Broadway Avenue & Lake Street in Forrest Lake, Minnesota (2x2 reduced to 1x1)
-Main Ave & Broadway in De Pere, Wisconsin (2x2 reduced to 2x1)

Pavement markings and signage: The study done on the Richfield, Minnesota roundabout at 66th &  Portland has been discussed on this thread multiple times.  The study suggests that standard arrows are less confusing to drivers than fishhooks (the most recent repaving at this intersection includes fishhook arrows though :? ).   

Reaction time: Larger roundabouts may be safer assuming the entry angles of the roundabout are designed properly and circulating speeds remain low.  Consider the following scenario.  CAR A enters the roundabout mistakenly believing CAR B is about to exit.  Would u want CAR B to take 1.7 seconds or 3.4 seconds to travel the blue path?  More reaction time is a good thing!

95 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test4_zpshnyyiesp.jpg)

160 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test3_zpscdfdzp4h.jpg)

YES.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 14, 2015, 11:55:02 PM
Have you investigated anything other than the size of the central island?
...
YES.
No, you have not. What you have reiterated are more generalities for a small sample of intersections. When I say investigate, I mean take all of the crash-prone roundabouts and investigate each roundabouts features: fast path speeds, deflection, path overlap, lane configuration, signing, pavement marking, PHI-angles, in addition to size. See how each of those characteristics compare to roundabouts with low/"acceptable" crash rates as well as what the current desirable metrics are for each. Size alone may or may not be the presiding factor in these cases. Making the circle arbitrarily larger will do you no good if you have poor speed control on the approach and/or bad path overlap.

Until then, or some new information comes to light that has not been beaten to death in the last 8 pages, I am done. We're going in circles. As I and roadfro have said, we've taken this size discussion as far as one can in an enthusiast setting.
Title: Re: Crash prone 'modern roundabouts'
Post by: iBallasticwolf2 on July 15, 2015, 09:07:32 AM

We're going in circles.

OH the irony!
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on July 15, 2015, 09:24:17 AM

We're going in circles.

OH the irony humanity!

FTFY.
Title: Re: Crash prone 'modern roundabouts'
Post by: iBallasticwolf2 on July 15, 2015, 09:29:01 AM

We're going in circles.

OH the irony humanity!

FTFY.

Well done.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 15, 2015, 09:33:25 AM

We're going in circles.

OH the irony humanity!

FTFY.

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 15, 2015, 10:36:13 AM
No, you have not. What you have reiterated are more generalities for a small sample of intersections. When I say investigate, I mean take all of the crash-prone roundabouts and investigate each roundabouts features: fast path speeds, deflection, path overlap, lane configuration, signing, pavement marking, PHI-angles, in addition to size.

The study done by the IIHS in 2000 analyzed a small sample of intersections as well.  That study has been embraced by the engineering community and is routinely cited in DOT websites and a link to the study can be found on the FHWA website.  The study looked at the before/after crash data of 24 total roundabouts (15 single lane, and 9 multi-lane) using the empirical Bayes approach.  It didn’t consider fast path speeds, deflection angles, path overlap, signing, pavement marking, PHI-angles, or size.  The conclusion of the study is that total crashes reduce by 39%, injury crashes reduce by 76%, and fatal crashes reduce by 90%. 

http://safety.fhwa.dot.gov/intersection/resources/fhwasa09027/resources/Crash%20Reductions%20Following%20Installation%20of%20Roundabouts.pdf

This thread, more than anything, highlights the fact that the IIHS study in 2000 is too limited in their analysis (and is heavily skewed towards single-lane roundabouts).  It should be painfully obvious that it is unlikely the high capacity 2x2 roundabouts being built today will see a 39% reduction in total crashes.  It should also be obvious that bigger roundabouts appear to perform better than smaller roundabouts.  Ultimately, the worst performing roundabouts in America have small central island diameters.  This is a simple fact that is difficult to dispute.


Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 16, 2015, 12:42:53 PM
Based on MnDot’s “critical crash rate index” , the 3rd most dangerous intersection in the Twin Cities metro for 2013 was at a double-lane roundabout at U.S. 61 & Broadway Avenue in Forest Lake.

http://kstp.com/article/stories/s3699209.shtml

The roundabout has a central island diameter of only 94 feet.  The fix?  They converted it to a single lane roundabout.  At least half-a-dozen examples have been cited of high crash rate roundabouts that have had circulating lanes removed.  Keep in mind, there are only about 40 high capacity 2x2 or 3x2 non-interchange roundabouts in America.  That means roughly 10% of the high capacity non-interchange roundabouts have had circulating lanes removed.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 21, 2015, 11:45:04 AM
Here's an analysis of some multi-lane roundabouts in Oregon.  A multi-lane roundabout in Astoria, Oregon saw a 125% increase in injury crashes.  Another multi-lane roundabout in Springfield, Oregon had a crash rate of 2.91 MEV.  As a comparison, here is a list of major Springfield intersections with their corresponding crash rates.

(http://alexforfg.com/wp-content/uploads/2014/12/springfieldtsp.jpg)
http://alexforfg.com/more-troubling-statistics-on-oregons-dual-lane-roundabouts/
Title: Re: Crash prone 'modern roundabouts'
Post by: Bickendan on July 21, 2015, 01:05:10 PM
Coe Circle doesn't even make the list. I wonder why that is...

Edit: So this is at the top of Oregon's list:
(http://alexforfg.com/wp-content/uploads/2014/12/SpringfieldRoundabout.jpg)

One thing that would greatly help: swapping out the yield signs with stop signs.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 21, 2015, 01:39:26 PM
Coe Circle doesn't even make the list. I wonder why that is...

Edit: So this is at the top of Oregon's list:
(http://alexforfg.com/wp-content/uploads/2014/12/SpringfieldRoundabout.jpg)

One thing that would greatly help: swapping out the yield signs with stop signs.

A few other potential ways to improve safety at this roundabout. 

#1.  Convert it to a 4-leg roundabout and remove access from Wayside Ln. (traffic can divert to Manor Drive to enter onto Hayden Bridge Way). 

#2.  Redesign the central island to be a true spiral roundabout (don't just rely on pavement markings to do the job).
Title: Re: Crash prone 'modern roundabouts'
Post by: Bickendan on July 21, 2015, 02:20:36 PM
Agreed, but I think the number one improvement is stop signs. Yield signs in these situations just promotes drivers risking their chances and trying to beat a car already in the roundabout. Coe Circle uses stop signs, and while drivers do 'California stops' if there aren't any cars already in the roundabout, they do keep an eye out and wait their turn. It also makes it more bicycle friendly.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on July 21, 2015, 02:30:41 PM
It helps to know where/how most of the accidents are happening.  If there's one entry point that's causing the vast majority of crashes, then they should try to deal with the problem rather than masking a solution.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on July 21, 2015, 02:55:20 PM
It helps to know where/how most of the accidents are happening.  If there's one entry point that's causing the vast majority of crashes, then they should try to deal with the problem rather than masking a solution.
Indeed, and without knowing the severity of the crashes, and the statistics now, they are meaningless. We're looking at 05-09 data there - modern roundabouts were very rare in the US around that period - could the answer be found in education failures rather than the engineering ones that Tradephoric thinks exist?

Junctions like this work all the time in the UK with near-zero levels of crashes - the existence of a round central island, or Wayside Lane probably are red herrings.
It also makes it more bicycle friendly.
STOP signs make nothing more bicycle friendly unless they don't have to - starting from a stop is not only tiring, but leaves the rider more erratic and vunerable as they build up the inertia that they lost by stopping (a yield isn't so bad if they just have to slow down to a slow speed, rather than come to a complete stop). The issue isn't the type of signs used anyway, it's drivers ignoring them...

It doesn't help matters that the US uses STOP like the boy who cried wolf - so YIELD is basically ignored because conflicts that should be simple yields demand you stop, therefore if it's a yield, there won't be any danger.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 21, 2015, 05:33:10 PM
It doesn't help matters that the US uses STOP like the boy who cried wolf - so YIELD is basically ignored because conflicts that should be simple yields demand you stop, therefore if it's a yield, there won't be any danger.

I can't help but think that wider use of the yield sign might help with roundabout education. I don't think enough drivers encounter "yield" situations enough on their daily drive enough for them to comprehend them at roundabouts.



Of course, does anything really need to be done? If we keep tackling intersections on top of "the list", we'll eventually go through every intersection in the city. I've said this before, and I'll say it again: roundabouts have more crashes because drivers aren't as familiar with them as typical four-way junctions (Coe Circle is a four way junction in my book). The two ways to tackle increased collisions at roundabouts is to do;

A) nothing, and drivers will eventually figure out what to do (this could take 10 to 20 years); and/or
B) build more roundabouts so drivers become more familiar with them.
Title: Re: Crash prone 'modern roundabouts'
Post by: Bickendan on July 21, 2015, 05:58:36 PM
Junctions like this work all the time in the UK with near-zero levels of crashes - the existence of a round central island, or Wayside Lane probably are red herrings.The issue isn't the type of signs used anyway, it's drivers ignoring them...

It doesn't help matters that the US uses STOP like the boy who cried wolf - so YIELD is basically ignored because conflicts that should be simple yields demand you stop, therefore if it's a yield, there won't be any danger.

These hit the nail on the head. As a biker myself, I don't regard having to come to a complete stop at a red light or stop sign an issue. Bikers that complain about it are the ones that will blow through a red light anyway, and I don't have much sympathy for them when something happens.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 23, 2015, 11:13:33 AM
Indeed, and without knowing the severity of the crashes, and the statistics now, they are meaningless.

The link broke down the roundabouts by crash severity (K, A, B, C, O).  The detailed crash severity data isn't ”˜meaningless’.

We're looking at 05-09 data there - modern roundabouts were very rare in the US around that period —

There were over 2,000 modern roundabouts in America by the end of 2005.  Of course ”˜very rare’ is a vague term that makes your statement difficult to dispute.

could the answer be found in education failures rather than the engineering ones that Tradephoric thinks exist?  Junctions like this work all the time in the UK with near-zero levels of crashes - the existence of a round central island, or Wayside Lane probably are red herrings.

A roundabout outside Farndon, UK has seen 150 crashes since it was redesigned in June, 2012.  This is on par with some of the worst performing roundabouts cited on this thread.  The British people have had 50+ years to perfect yield-at-entry roundabouts and should be well educated in their use.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Fardon_zpsyiyqhpfa.png)
http://newarkadvertiser.co.uk/articles/news/A46-Farndon-roundabout-layout-will-be-changed
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on July 23, 2015, 01:01:41 PM
The link broke down the roundabouts by crash severity (K, A, B, C, O).
But doesn't have current data? What use is 5-year data from years ago good for unless you also have current data to see whether figures have decreased or not? Even if there's not a downward trend as more people understand how the junction works, then you are still arguing for rebuilding the junction because 6 years ago there were a lot of crashes.
Quote
The detailed crash severity data isn't ”˜meaningless’.
You are interpreting words worse than you interpret statistics: I explicitly said that without severity data, the figures are meaningless - not that severity data is meaningless.
Quote
There were over 2,000 modern roundabouts in America by the end of 2005.  Of course ”˜very rare’ is a vague term that makes your statement difficult to dispute.
Keep in mind, there are only about 40 high capacity 2x2 or 3x2 non-interchange roundabouts in America.
I am keeping that mind, and then you attack me for doing so! You harp on about multi-lane (and specifically those ones) roundabouts being dangerous death traps, but as well as the (inevitable) small samples, you aren't accounting for unfamiliarity.

A figure of 40 today suggests 'very rare' is highly unlikely to be false 10 years ago.

Of course it's not precise - I couldn't be bothered to do a detailed and time-consuming analysis of how many junctions in the US there were, what proportion of them were roundabouts and factor in regional data - if there was 20000 of them in Florida, then a handful in Oregon will still mean that they aren't commonly occurred by drivers in the area. However, 'very rare' is a qualitative phrase not a quantitative one and therefore more meaningful - your figure of over 2000 roundabouts is a fairly precise quantitative one, but it is meaningless without knowing whether in this context 2000 is big or small.
Quote
A roundabout outside Farndon, UK has seen 150 crashes since it was redesigned in June, 2012.  This is on par with some of the worst performing roundabouts cited on this thread.
I'm a roadgeek, and I went "where the fuck is that" (it's a tiny hamlet): about as descriptive as 'Bob's Farm, USA'. Thankfully you gave an article, so I could know that it is the Farndon Roundabout near Newark, Notts.

That roundabout sees 29900 Vehicles/average weekday on the new A46 leg with high levels of trucks (26200 a year after opening on the A46 north of the roundabout, 13200 on the B6166, 2950 on the old route), making this junction 13.2MEV in that first year and roughly 3 crashes/MEV. That is truly awful (though this, like the Oregon example above seems to be, is a clear outlier).

Looking, the most obvious safety improvement would be to put in the yellow rumble strips that exist almost every time a long (and many not-very long) grade-separated route ends at a roundabout. I can't help but think that 70mph+ traffic on a well-aligned freeway-quality trunk road coming arriving at the roundabout without realising it was that close is going to be a factor in why there is a high level of crashes there.

There's narrow lanes on, and an atypical (I think - it might be common to spiral unsignalised roundabouts in that neck of the woods, but I cannot think of any around here) design of, the circulatory carriageway.

There's also the merging issue just north of the roundabout, where two lanes of trunk road traffic (there was only one before, save for at the roundabout) are forced into one lane. And the article says that the surface was poorly done and anti-skid lost.

So lots of possible factors here as to why this roundabout has become a lot more dangerous - some of which you recommend as safety features, others of which you totally and completely ignore.

If you look at it on google's satellite imagery then you'll see that the old roundabout had a much smaller circulatory carriageway and 3 lanes on it - both of which have been your go-to "these are problems for safety".

And, of course, it really needed to be a GSJ (and was certainly seen in the planning as a fairly temporary junction, though no plans have been sorted on finishing the corridor)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 23, 2015, 02:50:19 PM

A reoccurring argument in this thread is that crashes at American roundabouts are due to driver unfamiliarity.   It’s the “dumb American”  argument.  Yet when a roundabout with a high crash rate is cited from the UK, the focus shifts entirely to design:

Looking, the most obvious safety improvement would be to put in the yellow rumble strips that exist almost every time a long (and many not-very long) grade-separated route ends at a roundabout. I can't help but think that 70mph+ traffic on a well-aligned freeway-quality trunk road coming arriving at the roundabout without realising it was that close is going to be a factor in why there is a high level of crashes there.

There's narrow lanes on, and an atypical (I think - it might be common to spiral unsignalised roundabouts in that neck of the woods, but I cannot think of any around here) design of, the circulatory carriageway.

There's also the merging issue just north of the roundabout, where two lanes of trunk road traffic (there was only one before, save for at the roundabout) are forced into one lane. And the article says that the surface was poorly done and anti-skid lost.

So lots of possible factors here as to why this roundabout has become a lot more dangerous - some of which you recommend as safety features, others of which you totally and completely ignore.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 23, 2015, 02:51:02 PM
If you look at it on google's satellite imagery then you'll see that the old roundabout had a much smaller circulatory carriageway and 3 lanes on it - both of which have been your go-to "these are problems for safety".

Just to be clear, this is the roundabout in question right? 
https://www.google.com/maps/@53.06409,-0.83613,131m/data=!3m1!1e3

The old roundabout did not have 3-cirulating lanes of traffic.  In addition, the central island diameter of the old roundabout was 135 feet (much larger diameter than 100 feet).  IMO, the size of this roundabout looks pretty decent.
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on July 23, 2015, 03:30:16 PM
The link broke down the roundabouts by crash severity (K, A, B, C, O).
But doesn't have current data? What use is 5-year data from years ago good for unless you also have current data to see whether figures have decreased or not? Even if there's not a downward trend as more people understand how the junction works, then you are still arguing for rebuilding the junction because 6 years ago there were a lot of crashes.ugh no plans have been sorted on finishing the corridor)

The bit tradephoric showed in the post was the initial stats from when the roundabout first opened, from the City of Springfield's Transportation System Plan.  If you follow the link, you'll find that there's further stats from the period of 1/1/2009 to 12/31/2013 (the most recent that were available then).  The actual PDFs from the ODOT Crash Reporting system are also linked for the various legs.  The KABCO stats in the main post are an aggregate of all the legs during that latter reporting period.  Pioneer Pkwy W/Hayden Bridge had 46 total (http://alexforfg.com/wp-content/uploads/2014/12/Pioneer-Pkwy-W-and-Hayden-Bridge-KABCO.pdf), Pioneer Pkwy E/Hayden Bridge had 78 total (http://alexforfg.com/wp-content/uploads/2014/12/Pioneer-Pkwy-E-and-Hayden-Bridge-KABCO.pdf), and there's 57 more crashes (http://alexforfg.com/wp-content/uploads/2014/12/MLK-and-Hayden-Bridge-KABCO.pdf) associated with MLK/Hayden Bridge (whether this is at the NW corner or NE corner is unclear, due to how ODOT compiled things).
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 23, 2015, 05:57:25 PM
A reoccurring argument in this thread is that crashes at American roundabouts are due to driver unfamiliarity.   It’s the “dumb American”  argument.  Yet when a roundabout with a high crash rate is cited from the UK, the focus shifts entirely to design:

Are you suggesting that UK drivers are unfamiliar with roundabouts? Or that US drivers understand them perfectly and that design is entirely to blame?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 24, 2015, 11:02:53 AM
Are you suggesting that UK drivers are unfamiliar with roundabouts? Or that US drivers understand them perfectly and that design is entirely to blame?

I’m suggesting that the ”˜driver unfamiliarity’ argument is masking poor design.  Take another look at the aerial footage of the DePere roundabout.  At 4 seconds in the video, a yellow semi pulls up and waits for a gap in traffic to enter the roundabout.  The semi enters the roundabout at the 12 second mark and forces circulating vehicles to nearly come to a complete stop.  If one of the circulating drivers couldn’t stop in time and struck the semi, the semi driver would be cited for ”˜failure to yield.  Did the yellow semi really do anything wrong here?  During rush hours, do we expect the yellow semi to wait 15 minutes for traffic to clear all legs of the roundabout before pulling out?   It’s a design that forces some drivers (IE. larger vehicles during rush hour) to play Russian Roulette (the bullet being a circulating driver not paying attention).


The theory is if the roundabout was bigger (and there was greater distance between legs), circulating traffic will have more time to react when a semi tries to squeeze into the roundabout (and if properly designed, a larger roundabout doesn’t mean circulating speeds are faster… they could actually be slower since entry deflection angles can be more pronounced at large diameter roundabouts).  Sure, some drivers will still enter the roundabout without even looking and run straight into a circulating vehicle, but some of the failure to yield crashes might be prevented with a larger central island diameter.  There has to be reasons why so many multi-lane roundabouts with central-island diameters of 100 feet or less have performed so poorly.  The idea that we just ignore failure to yield crashes and chalk it up to ”˜driver unfamiliarity’ doesn’t sit well with me. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on July 24, 2015, 11:19:35 AM
Are you suggesting that UK drivers are unfamiliar with roundabouts? Or that US drivers understand them perfectly and that design is entirely to blame?

I’m suggesting that the ‘driver unfamiliarity’ argument is masking poor design.  Take another look at the aerial footage of the DePere roundabout.  At 4 seconds in the video, a yellow semi pulls up and waits for a gap in traffic to enter the roundabout.  The semi enters the roundabout at the 12 second mark and forces circulating vehicles to nearly come to a complete stop.  If one of the circulating drivers couldn’t stop in time and struck the semi, the semi driver would be cited for ‘failure to yield.  Did the yellow semi really do anything wrong here?  During rush hours, do we expect the yellow semi to wait 15 minutes for traffic to clear all legs of the roundabout before pulling out?   It’s a design that forces some drivers (IE. larger vehicles during rush hour) to play Russian Roulette (the bullet being a circulating driver not paying attention).


The theory is if the roundabout was bigger (and there was greater distance between legs), circulating traffic will have more time to react when a semi tries to squeeze into the roundabout (and if properly designed, a larger roundabout doesn’t mean circulating speeds are faster… they could actually be slower since entry deflection angles can be more pronounced at large diameter roundabouts).  Sure, some drivers will still enter the roundabout without even looking and run straight into a circulating vehicle, but some of the failure to yield crashes might be prevented with a larger central island diameter.  There has to be reasons why so many multi-lane roundabouts with central-island diameters of 100 feet or less have performed so poorly.  The idea that we just ignore failure to yield crashes and chalk it up to ‘driver unfamiliarity’ doesn’t sit well with me. 


Looking at this video, the "circulating" vehicles were just coming out of a yield at the same time.  They paused for a few seconds, and everyone went on their merry way.  It's really not a huge deal.

You are always going to have examples where certain vehicles - such as trucks - are going to have it a little hard.  At a traditional 4 way intersection, trucks occasionally have to swing out from the right lane in order to make their right turn without going up and hitting anything on the curb.  If they hit something on the curb, or a vehicle in another lane, they'll be in the wrong then also.  Yes, intersections are designed when possible so that trucks don't have to do this.  But in tight street environments such as cities, there's no way around this happening.

You simply can't compensate for every possible scenario out there.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 24, 2015, 01:15:10 PM
Looking at this video, the "circulating" vehicles were just coming out of a yield at the same time.  They paused for a few seconds, and everyone went on their merry way.  It's really not a huge deal.

It’s not a huge deal to stop in the middle of a roundabout to let in a semi, but it’s an annoyance that increases the likelihood of a crash.  Consider the following scenario. The car and semi pull into the roundabout at the same time.  Would u want the car to take 3.3 seconds or 5.8 seconds to travel the blue path?  The additional 2.5 seconds of reaction time at the larger diameter roundabout may allow the car to simply let off the gas to let the semi in (as opposed to coming to a stop in the middle of the roundabout). 

Would an additional 2.5 seconds of reaction time potentially prevent a crash?  I think so.

115 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/smalldia_zpsgcepbzkj.jpg)

160 FT central island diameter:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/largedia_zpslxkme5do.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on July 24, 2015, 01:19:28 PM
Looking at this video, the "circulating" vehicles were just coming out of a yield at the same time.  They paused for a few seconds, and everyone went on their merry way.  It's really not a huge deal.

It’s not a huge deal to stop in the middle of a roundabout to let in a semi, but it’s an annoyance that increases the likelihood of a crash.  Consider the following scenario. The car and semi pull into the roundabout at the same time.  Would u want the car to take 3.3 seconds or 5.8 seconds to travel the blue path?  The additional 2.5 seconds of reaction time at the larger diameter roundabout may allow the car to simply let off the gas to let the semi in (as opposed to coming to a stop in the middle of the roundabout). 

Would an additional 2.5 seconds of reaction time potentially prevent a crash?  I think so.

The f'ing cars didn't crash into the f'ing truck.  There was no potential crash that could've potentially been avoided.  What's your point?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 24, 2015, 02:01:54 PM
I don't think roundabouts are the only place where trucks tend to try and squeeze into gaps that aren't big enough for them. But they are much larger than cars so they'll win. That, and sometimes with roundabouts, the throughput rate is so high that a reasonable gap for a truck may never form, even with a large roundabout (though perhaps a roundabout the size of the UK one above may permit gaps large enough...not sure).

Basically, I don't think this is a problem that needs solving.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 27, 2015, 11:40:09 AM
The f'ing cars didn't crash into the f'ing truck.  There was no potential crash that could've potentially been avoided.  What's your point?

I’m trying to lay out an explanation why small diameter roundabouts have performed so poorly.  The truck pulling out into the roundabout forced circulating vehicles to take evasive action to avoid a crash (IE. applying the brakes and nearly coming to a complete stop in the roundabout).  If the roundabout had a larger diameter (and it took an additional 2.5 seconds for circulating vehicles to encounter the semi), evasive action could be avoided.  Relying on vehicles to take evasive action to avoid a crash isn’t a great scenario and increases the potential of a crash.  In the end, 2x2 roundabouts with central island diameters of 100 feet or less have seen crashes increase by 500%, 800%, up to 1400%.  That’s not a good track record.  The fact that the cars didn’t hit the truck in the video doesn’t invalidate the point. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 31, 2015, 11:56:46 AM
Crashes are up at a new 2x2 roundabout at Highway 22 & Madison Ave. in Mankato, Minnesota.  One thing to note is this roundabout has standard pavement markings (as opposed to the fishhook pavement markings).  This is likely a direct result of the study done on the Richfield, Minnesota roundabout that studied the effects of standard vs. fishhook pavement markings. 

The lessons learned from the Richfield, Minnesota roundabout were applied to the Mankato roundabout yet crashes are still up.  What's concerning is officials seem resigned to the fact that accidents will go up at these high volume roundabouts.  Of course, there is something else in common between the Richfield & Mankato roundabouts.... small central island diameters.  Perhaps officials should focus on the size of the roundabouts before resigning themselves to the fact that accidents will increase at these roundabouts.  Don't accept mediocre performance.

Quote
The tradeoffs were discussed in the planning stages of the roundabouts. In exchange for more accidents, the roundabout would make said crashes much safer. And improve traffic flow.
http://www.keyc.com/story/28328544/crashes-at-mn-hwy-22-more-frequent-but-much-safer

Sure, it's great that roundabouts reduce injury crashes, but which would you prefer?

A.)  A roundabout with a central island diameter of 150 feet that has 20 crashes and 1 injury crash.
B.)  A roundabout with a central island diameter of 100 feet that has 60 crashes and 1 injury crash. 

I'll pick Option A.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 03, 2015, 11:07:19 AM
The lowest crash rate roundabouts on this thread have had central island diameters between 130 and 200 feet.  This equates to Inscribed Circle Diameters of roughly 200 to 300 feet (60 to 90 meters).   Take a look at the graph below that looks at the crash rate of Czech Republic roundabouts in relation to their inscribed diameter.  The multi-lane roundabouts with ICD’s between 60 to 90 meters perform well.  Smaller than 60 meters and the crash rate goes up; larger than 90 meters and the crash rate goes up. 
 
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Czech_zpsze2irpjn.png)
http://www.degruyter.com/view/j/tvsb.2010.x.issue-1/v10160-010-0009-0/v10160-010-0009-0.xml

The ”˜goldilocks’ inscribed circle diameter appears to be between 200 and 300 feet (60 to 90 meters) for multi-lane roundabouts. 
Title: Re: Crash prone 'modern roundabouts'
Post by: Sykotyk on August 03, 2015, 07:18:38 PM
Rotaries in the northeast work very well. I like them, such as this one I drove on US44 just east of I-495. I drove it east and west, and though traffic seemed to be endless from it, it cleared out well because of the spacing between entry points (though I really think that Friendly's entrance should be closed and only access it from the side road).

https://www.google.com/maps/place/Plympton,+MA/@41.9027404,-70.9590075,19z/data=!3m1!1e3!4m2!3m1!1s0x89e497d5f44178cb:0x3d50f1892f6c5149

The smaller modern roundabouts aren't safe because drivers treat a yield sign as nothing. Just as an on-ramp has a yield sign, the mindset is if you can get in front of that car, you can speed up and get in front of them. This is tolerated on freeway on-ramps, but dangerous in roundabouts.

The idea you must 'yield' to traffic in the circle only makes it worse. The goal then, is to get in that circle at all costs, so everyone else has to yield to you. Small traffic circles, though with a yield sign, should be treated just the same as a four-way stop. Each entry point taking turns letting one car into the circle (regardless which exit point the cars take). You can have more in the circle than one car, but traffic to your right gets to go first (i.e., you yield to the next entry point).

But, our signage laws AND the way our drivers use those signs is not possible. Yield doesn't mean yield to most drivers. I've seen roundabouts where a line of 5-10-15-20 cars all breeze into a roundabout from one entrypoint, choking the entire thing because nobody else can go until every last car gets through from that one point. Meanwhile, traffic backed up the other entry points, and as soon as they got their shot, they floored it. Only for two entry points to clog the center, not allowing any new traffic in as that initial burst had to disperse.

A four-way stop with each entrypoint alternating N/S to E/W with left turn traffic yielding to through and right turn traffic first would been the most efficient means to clear our a huddled intersection.

Title: Re: Crash prone 'modern roundabouts'
Post by: realjd on August 03, 2015, 08:08:21 PM
Rotaries in the northeast work very well. I like them, such as this one I drove on US44 just east of I-495. I drove it east and west, and though traffic seemed to be endless from it, it cleared out well because of the spacing between entry points (though I really think that Friendly's entrance should be closed and only access it from the side road).

https://www.google.com/maps/place/Plympton,+MA/@41.9027404,-70.9590075,19z/data=!3m1!1e3!4m2!3m1!1s0x89e497d5f44178cb:0x3d50f1892f6c5149

The smaller modern roundabouts aren't safe because drivers treat a yield sign as nothing. Just as an on-ramp has a yield sign, the mindset is if you can get in front of that car, you can speed up and get in front of them. This is tolerated on freeway on-ramps, but dangerous in roundabouts.

The idea you must 'yield' to traffic in the circle only makes it worse. The goal then, is to get in that circle at all costs, so everyone else has to yield to you. Small traffic circles, though with a yield sign, should be treated just the same as a four-way stop. Each entry point taking turns letting one car into the circle (regardless which exit point the cars take). You can have more in the circle than one car, but traffic to your right gets to go first (i.e., you yield to the next entry point).

But, our signage laws AND the way our drivers use those signs is not possible. Yield doesn't mean yield to most drivers. I've seen roundabouts where a line of 5-10-15-20 cars all breeze into a roundabout from one entrypoint, choking the entire thing because nobody else can go until every last car gets through from that one point. Meanwhile, traffic backed up the other entry points, and as soon as they got their shot, they floored it. Only for two entry points to clog the center, not allowing any new traffic in as that initial burst had to disperse.

A four-way stop with each entrypoint alternating N/S to E/W with left turn traffic yielding to through and right turn traffic first would been the most efficient means to clear our a huddled intersection.



On small roundabouts, you don't treat them as a 4 way stop. You treat them as a roundabout. If two cars arrive at exactly the same time, it's still treated as a roundabout, i.e. yield to the car on the left.

Where do they put yield signs at the top of on ramps? That's dumb. It's a merge, not a yield.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 03, 2015, 09:41:51 PM
Rotaries in the northeast work very well. I like them, such as this one I drove on US44 just east of I-495. I drove it east and west, and though traffic seemed to be endless from it, it cleared out well because of the spacing between entry points (though I really think that Friendly's entrance should be closed and only access it from the side road).

https://www.google.com/maps/place/Plympton,+MA/@41.9027404,-70.9590075,19z/data=!3m1!1e3!4m2!3m1!1s0x89e497d5f44178cb:0x3d50f1892f6c5149

The US44 rotary has an abysmal crash record though.  From 2009 to 2011, the rotary averaged 123 crashes a year.  The rotary has a inscribed circle diameter of 400 feet which leads to high circulating speeds. 

Quote
According to the Department of Transportation, approximately 40,000 cars use the rotary each day and there were 58 accidents there a year on average between 2007 and 2009 before the numbers jumped to about 123 a year between 2009 and 2011. Built around 1932, the rotary encircles a green lawn used as an American Legion memorial where flags are periodically flown as a way to honor deceased servicemen and women.

https://www.bostonglobe.com/metro/regionals/south/2014/03/12/after-decades-gridlock-revamped-rotary-middleborough-will-open-region-some-say/6CoApiCZds5HWcPyTyhl2I/story.html

Title: Re: Crash prone 'modern roundabouts'
Post by: johndoe on August 03, 2015, 10:37:37 PM
Here's an interesting article: http://journalstar.com/news/local/govt-and-politics/mayor-picks-elevated-roundabout-for-warlick-intersection/article_064e9de0-f6b5-5bd0-9c6d-8eba655c3c4f.html

It alludes to previous changes at another local roundabout: http://journalstar.com/news/local/fixes-aimed-at-simplifying-superior-street-roundabout/article_088eec03-c54d-5f34-9808-36ffa4ead11c.html
Title: Re: Crash prone 'modern roundabouts'
Post by: Sykotyk on August 04, 2015, 05:17:16 PM
The US44 rotary has an abysmal crash record though.  From 2009 to 2011, the rotary averaged 123 crashes a year.  The rotary has a inscribed circle diameter of 400 feet which leads to high circulating speeds. 

123 crashes may sound impressive... but what's that to traffic volume compared to other rotaries with similar volume?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 04, 2015, 05:48:00 PM
123 crashes may sound impressive... but what's that to traffic volume compared to other rotaries with similar volume?

Assuming the 40,000 volume cited in the article, that equates to 8.4 accidents / million vehicles.  As a general rule, anything over 2 accidents / million vehicles at an intersection is considered high.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 12, 2015, 10:26:24 AM
There have been 13 crashes in 1 week at a new multi-lane roundabout in Lakeville Minnesota.   It’s on track to have 676 crashes the first year of operations!  That won’t happen, but it’s still bad PR when you have 13 crashes in a week.

http://kstp.com/article/stories/s3898071.shtml


Many of the design recommendations that are found in the Richfield, MN study (which studied a crash prone 2x2 roundabout) have been implemented in the new roundabout in Lakeville (standard pavement markings are being used as opposed to fishhook markings).  It will be interesting to see if the lessons learned at the 2x2 roundabout in Richfield will be able to reduce the crash rate at the 2x2 roundabout in Lakeville (based on the first week of crash data though, it's not looking good).
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 12, 2015, 02:32:26 PM
(based on the first week of crash data though, it's not looking good).

I think it's far too early to be predicting long-term crash data. Hell if I know the stats, but I'm willing to bet that most roundabouts, when they first open, have a spat of collisions as people figure things out. Give them a chance.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 14, 2015, 03:01:06 PM
(based on the first week of crash data though, it's not looking good).

I think it's far too early to be predicting long-term crash data. Hell if I know the stats, but I'm willing to bet that most roundabouts, when they first open, have a spat of collisions as people figure things out. Give them a chance.

Every multi-lane (2x2) roundabout cited on this thread where crash data is available has seen an increase in total crashes.  Can you give me a compelling reason why the multi-lane roundabout in Lakeville will be any different?  It’s not too early to predict a trend. 

Driving through a multi-lane roundabout shouldn’t be a foreign experience for most Minneapolis drivers.  There is a multi-lane roundabout 2 miles down the road from the new roundabout in Lakeville.  In addition, there are roughly 30 multi-lane roundabouts in the Minneapolis region. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on September 14, 2015, 03:19:30 PM
Every multi-lane (2x2) roundabout cited on this thread where crash data is available has seen an increase in total crashes.  Can you give me a compelling reason why the multi-lane roundabout in Lakeville will be any different?  It’s not too early to predict a trend. 

LOL  :rofl:

Why would someone post about non-accident prone roundabouts on a thread titled "Crash Prone Modern Roundabouts"?  Of course most roundabouts cited on this thread have seen an increase in total crashes.  That's the whole fricken point of this thread.

Should we start up a thread "Non-Accident prone roundabouts"?  Can't wait for the exciting dialogue on that thread.

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 14, 2015, 04:37:13 PM
Previously in this thread, a comprehensive list of 2x2 roundabouts in America was queried out from a database of over 5,100 modern roundabouts.  This was in direct response to a request you had made jeffandNicole.  I attempted to find before/after crash data for each one.  I could only track down crash data for 14 out of the 40, but of those 14, all had an increase in total crashes.

It would probably be fair to see a longer list, which will show both 100' diameter roundabouts that don't have high crash frequencies, and roundabouts with larger diameters and how they rank. 

Here is a list of 40 multi-lane roundabouts that I think could be meaningful to this conversation.  This was queried from a database of over 5,100 modern roundabouts.  This was the criteria used to query out the list:

-roundabouts constructed within the last 10 years
-all approaches have 2 entry lanes
-roundabouts have 4-legs
-main & side streets are major state or county routes (ie. likely high AADT roundabouts)
-interchange roundabouts (and frontage road roundabouts) not included

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBtest_zpsbkjmf4ri.png)

Now the hard part is finding accurate before/after crash data to make any type of analysis.  Here is a google KMZ file that includes the 40 roundabouts in the chart above:

http://www.mediafire.com/download/cd570rarros2c3g/Multi-Lane+Roundabouts+%28with+high+AADT%29.kmz


Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 14, 2015, 04:44:53 PM
Here's the 14 roundabouts i eventually found crash data for.  Increases in total crashes ranged from 36% to 1400%. 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBDATASummary_zpsg7upbybr.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: johndoe on September 14, 2015, 09:39:42 PM
Interesting data, some of those are shocking!  171 crashes in one year? ! That's hard to believe! (Not doubting you)   Can I ask why you exempted interchanges ?
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on September 15, 2015, 01:57:45 PM
Yeah, I questioned the data because I travel through roundabouts on that list frequently (more than once weekly).  If the data was true, I'd come across more accidents than I do, even from just an anecdotal sense.
Title: Re: Crash prone 'modern roundabouts'
Post by: NJRoadfan on September 15, 2015, 03:38:35 PM
After braving this roundabout, I'd have to think there are plenty of accidents: https://goo.gl/maps/7sKaT

Compared to others in the area, it has a small diameter island. Its pretty difficult to "jump in" during rush hour.
Title: Re: Crash prone 'modern roundabouts'
Post by: Mrt90 on September 15, 2015, 04:09:44 PM
This is a two lane roundabout in Pleasant Prairie, Wisconsin.  The problem that I have with this roundabout is that there is an inconsistency regarding which lane(s) can exit the roundabout.  If you exit onto 39th Avenue going north or south or if you exit onto Hwy165 going west you can be in either lane to exit. However, if you are exiting on Hwy165 going east then you must be in the outside lane in order to exit and the inside lane is only to continue in the roundabout.  Why is that one exit different that the other 3?  What usually happens to me is that I'm trying to continue east on Hwy165 so I know that I have to be in the right lane the way the lanes are drawn, but someone will pass me in the inside lane and continue east on Hwy165, cutting me off. If there is another car on the inside I'm basically forced to stop because everyone thinks they can exit from the inside lane, and because of the other roads in the area almost everyone that enters the roundabout from the west is exiting south or east, not north. I'm not sure why the inside lane isn't always a "continue in the roundabout" lane and the outside lane is the only exit lane, but only 1 of the 4 exits in this roundabout is drawn this way.  Is this typical?


https://www.google.com/maps/@42.5225151,-87.8537268,138m/data=!3m1!1e3?hl=en
Title: Re: Crash prone 'modern roundabouts'
Post by: johndoe on September 15, 2015, 05:24:20 PM
Mrt90, it's because of the dual EBL.  (You could argue dual lefts probably aren't necessary because look what happens to those two lanes a whole 50' north of the intersection...)  To me it looks like there are lots of signs and markings; it's unwise for drivers to assume a 2 lane approach always means two through lanes.  If people would drive roundabouts like signals many problems would be minimized.
Title: Re: Crash prone 'modern roundabouts'
Post by: Mrt90 on September 15, 2015, 05:41:18 PM
johndoe I see what you mean, but it probably would have been better if the road going east had two lanes merge into one after the roundabout like the other roads do, so that the exiting lanes were consistent.  The other problem is that if you look at the map the I linked and go a little bit west, there is another roundabout (the link below show both).  So someone going east on Hwy 165 through both roundabouts can use either lane to continue east through the first roundabout, but then is supposed to use only the outside lane to continue east on the 2nd roundabout.  And my experience is that almost everyone gets that 2nd roundabout east exit wrong.  It's probably safer for me to do it incorrectly just like everyone else.

https://www.google.com/maps/@42.5256339,-87.8568222,1106m/data=!3m1!1e3?hl=en
Title: Re: Crash prone 'modern roundabouts'
Post by: UCFKnights on September 16, 2015, 07:42:54 PM
That is among the best signed roundabout I have seen. Hard to believe people are getting that wrong... crazy
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 12, 2015, 01:18:01 AM
Found crash data for the multi-lane roundabout at Venice Ave & Jacaranda Blvd.  It has a crash rate of 4.16 (the highest crash rate intersection in Sarasota County).  The county considers any intersection with a crash rate of over 2 as "critical".   

http://www.heraldtribune.com/article/20150815/ARTICLE/150819785

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 12, 2015, 01:36:19 AM
Are there any multi-lane (2x2) roundabout in America where there was a reduction in total crashes?  I'm starting to wonder.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 12, 2015, 02:01:27 AM
Also in the article;

Quote
Oddly, as Bennett noted, a by-product of the roundabout is more lives have been saved even though crash rates skyrocketed. People drive slower in roundabouts — the posted speed limit is 15 mph in Venice – lessening the chance of serious injuries, but the lack of knowledge of how to maneuver them causes plenty of sideswipes and insurance claims in Venice.

Yes, there does seem to be an increase in collisions at 2x2 roundabouts. Fine. But if the overall number of critical-injury collisions is falling, that's good, yes?

Do you have some data for 2x2 roundabouts over time? I seem to remember some previous data that you provided showing overall collisions falling over time. I know this roundabout had 52, 57, and 50 over the last three years (overall # of collisions). So this most recent year was its best ever (despite the previous year being the worst ever). I think we need to give this intersection a few more...uhh, decades, before we declare it a loss.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 12, 2015, 11:29:31 AM
Do you have some data for 2x2 roundabouts over time? I seem to remember some previous data that you provided showing overall collisions falling over time. I know this roundabout had 52, 57, and 50 over the last three years (overall # of collisions). So this most recent year was its best ever (despite the previous year being the worst ever). I think we need to give this intersection a few more...uhh, decades, before we declare it a loss.

If an agency is aware that the roundabout has a crash rate of 4.16 (over 2x what they deem "critical") and does nothing to address the problem, they could potentially be found negligent.  “The roundabout will work well in 20 years”  is not a strong defense.  The roundabouts best performing year had total crashes 350% higher than when the intersection was signalized.  That’s a bad result.  When total crashes increase by 350%, there is no guarantee that injury crashes will drop (several roundabouts have been cited in this thread where injury crashes have gone up).
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on October 12, 2015, 02:34:23 PM
From jakeroot: "Oddly, as Bennett noted, a by-product of the roundabout is more lives have been saved even though crash rates skyrocketed."

Put that in your negligence and smoke it.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 12, 2015, 02:55:57 PM
Do you have some data for 2x2 roundabouts over time? I seem to remember some previous data that you provided showing overall collisions falling over time. I know this roundabout had 52, 57, and 50 over the last three years (overall # of collisions). So this most recent year was its best ever (despite the previous year being the worst ever). I think we need to give this intersection a few more...uhh, decades, before we declare it a loss.

If an agency is aware that the roundabout has a crash rate of 4.16 (over 2x what they deem "critical") and does nothing to address the problem, they could potentially be found negligent.  “The roundabout will work well in 20 years”  is not a strong defense.  The roundabouts best performing year had total crashes 350% higher than when the intersection was signalized.  That’s a bad result.  When total crashes increase by 350%, there is no guarantee that injury crashes will drop (several roundabouts have been cited in this thread where injury crashes have gone up).

But wouldn't an agency be found just as negligent, if not more, for installing an intersection that has been proven to be far deadlier? As an agency, an intersection where more minor injuries occur should be preferable to one where people have been proven to be killed (especially if you consider these Target:Zero campaigns which aim to end traffic fatalities at some point).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 12, 2015, 08:33:41 PM
Sarasota County stated they would review intersections with a crash rate equal to or greater than 2.0 MVE and recommend potential corrective measures for improvements.  This is from page 2 of the 2013-2014 Sarasota Crash Summary Report:

Quote
Crash rates for signalized intersections within the County typically range from a minimum of zero (i.e., no crashes) to approximately 3.5 MVE. Also, past records show that the top 10 intersections generally have crash rates greater than 2.0 MVE. Thus the County considers  a crash rate equal to or greater than 2.0 MVE as a critical rate.  Intersections that exceed this threshold are selected for further study and reviewed to recommend potential corrective measures for improvements.

https://www.scgov.net/PublicWorks/Traffic%20County%20Data/2013%20-%202014%20Summary%20Crash%20Report.pdf

If it can be proven that Sarasota County failed to review an intersection that had a crash rate equal to or greater than 2.0 MVE, then they could be found to be negligent.  It has nothing to do with the ”˜injury crash rate’ since that wasn’t the metric selected by Sarasota County.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on October 13, 2015, 06:55:21 PM
http://wishtv.com/2015/10/08/roundabouts-may-confuse-but-stats-back-up-their-safety/
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 13, 2015, 09:36:13 PM
http://wishtv.com/2015/10/08/roundabouts-may-confuse-but-stats-back-up-their-safety/

My favorite quote(s):

Quote
And even if you make a mistake, because speeds are so slow, most wrecks don’t involve serious injuries....[Carmel Mayor Jim Brainard] points out that because accidents and injuries are down in Carmel, insurance rates have dropped. He says the city doesn’t have a full “jaws of life”  crew in its fire department anymore because they don’t have the high speed impacts that they used to have and don’t need them very often.
Title: Re: Crash prone 'modern roundabouts'
Post by: cl94 on October 13, 2015, 10:59:33 PM
http://wishtv.com/2015/10/08/roundabouts-may-confuse-but-stats-back-up-their-safety/

My favorite quote(s):

Quote
And even if you make a mistake, because speeds are so slow, most wrecks don’t involve serious injuries....[Carmel Mayor Jim Brainard] points out that because accidents and injuries are down in Carmel, insurance rates have dropped. He says the city doesn’t have a full “jaws of life”  crew in its fire department anymore because they don’t have the high speed impacts that they used to have and don’t need them very often.

What's funny is that many places critical about the introduction of roundabouts think they're great 10-15 years later. I'll give an example from my hometown in Warren County, NY. About 10 years ago, NYSDOT put in a roundabout to replace the 5 way signalized intersection between US 9, NY 9L, and NY 32 at the center of Glens Falls. At first, everyone hated it. Then people realized that the once-common traffic issues were no more, it was easier to walk around downtown, and it put a nice centerpiece in a traditional New England-style town square. Last year, a new roundabout was installed in the town of Queensbury on Aviation Road about 1/2 mile west of I-87 Exit 19, replacing a dangerous acute angle intersection. Now, local media and residents are pushing to have more roundabouts installed in the area, notably in the vicinity of I-87 Exit 20.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 14, 2015, 12:17:43 AM
What's funny is that many places critical about the introduction of roundabouts think they're great 10-15 years later. I'll give an example from my hometown in Warren County, NY. About 10 years ago, NYSDOT put in a roundabout to replace the 5 way signalized intersection between US 9, NY 9L, and NY 32 at the center of Glens Falls. At first, everyone hated it. Then people realized that the once-common traffic issues were no more, it was easier to walk around downtown, and it put a nice centerpiece in a traditional New England-style town square. Last year, a new roundabout was installed in the town of Queensbury on Aviation Road about 1/2 mile west of I-87 Exit 19, replacing a dangerous acute angle intersection. Now, local media and residents are pushing to have more roundabouts installed in the area, notably in the vicinity of I-87 Exit 20.

The roundabouts you are referencing are single-lane roundabouts.  Driver's don't have too much trouble with those.  When the region constructs a complex multi-lane roundabout, that's when you might run into problems. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 14, 2015, 01:09:45 AM
Carmel is the roundabout capital of America and the mayor has been a staunch supporter of roundabouts for years.  The mayor cites safety statistics in this story, but keep in mind the stats are based on studies skewed towards evaluating single-lane roundabouts.   


Carmel roundabouts sound great after watching that story.  The reality is 3 of the top 4 highest crash intersections in Carmel occurred at roundabouts in 2014.  Here’s a list of the worst offenders:

33 crashes - 116th St & Illinois St
36 crashes - Carmel Drive & Keystone Pkwy
49 crashes - Old Meridian St & Pennsylvania
51 crashes - 116th St & Springmill Rd
68 crashes - 116th St & Keystone Pkwy

Carmel Police Department 2014 Annual report (refer to page 23)
http://carmel.in.gov/Modules/ShowDocument.aspx?documentID=5712
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 14, 2015, 01:21:31 AM
Carmel roundabouts sound great after watching that story.  The reality is 3 of the top 4 highest crash intersections in Carmel occurred at roundabouts in 2014.  Here’s a list of the worst offenders:

And if you compare those roundabouts to the signals they replaced, the roundabouts are (more than likely) safer. There is nothing wrong with the occasional fender-bender. You can't eliminate those. What you can do, is mitigate severe collisions by removing the possibility of high-speed impacts altogether. Carmel is, according to Brainard (based on my quoted text above), safer as a result of these roundabouts. There may be more collisions, but they are nowhere near as severe as the ones before.

My point being, safety is measured by more than just the number of collisions at an intersection.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on October 14, 2015, 09:05:56 AM
What's funny is that many places critical about the introduction of roundabouts think they're great 10-15 years later. I'll give an example from my hometown in Warren County, NY. About 10 years ago, NYSDOT put in a roundabout to replace the 5 way signalized intersection between US 9, NY 9L, and NY 32 at the center of Glens Falls. At first, everyone hated it. Then people realized that the once-common traffic issues were no more, it was easier to walk around downtown, and it put a nice centerpiece in a traditional New England-style town square. Last year, a new roundabout was installed in the town of Queensbury on Aviation Road about 1/2 mile west of I-87 Exit 19, replacing a dangerous acute angle intersection. Now, local media and residents are pushing to have more roundabouts installed in the area, notably in the vicinity of I-87 Exit 20.

The roundabouts you are referencing are single-lane roundabouts.  Driver's don't have too much trouble with those.  When the region constructs a complex multi-lane roundabout, that's when you might run into problems. 


At least in New York, anything larger than a two-lane roundabout gets scoffed at.  Not sure if we have anything larger than a two-lane roundabout here, but I know they've been outright avoided at significant cost (Washington Ave/Fuller Rd in Albany was considered for a three-lane roundabout before going with a smaller roundabouts and an overpass).
Title: Re: Crash prone 'modern roundabouts'
Post by: cl94 on October 14, 2015, 09:31:35 AM
What's funny is that many places critical about the introduction of roundabouts think they're great 10-15 years later. I'll give an example from my hometown in Warren County, NY. About 10 years ago, NYSDOT put in a roundabout to replace the 5 way signalized intersection between US 9, NY 9L, and NY 32 at the center of Glens Falls. At first, everyone hated it. Then people realized that the once-common traffic issues were no more, it was easier to walk around downtown, and it put a nice centerpiece in a traditional New England-style town square. Last year, a new roundabout was installed in the town of Queensbury on Aviation Road about 1/2 mile west of I-87 Exit 19, replacing a dangerous acute angle intersection. Now, local media and residents are pushing to have more roundabouts installed in the area, notably in the vicinity of I-87 Exit 20.

The roundabouts you are referencing are single-lane roundabouts.  Driver's don't have too much trouble with those.  When the region constructs a complex multi-lane roundabout, that's when you might run into problems. 


At least in New York, anything larger than a two-lane roundabout gets scoffed at.  Not sure if we have anything larger than a two-lane roundabout here, but I know they've been outright avoided at significant cost (Washington Ave/Fuller Rd in Albany was considered for a three-lane roundabout before going with a smaller roundabouts and an overpass).

Jones Beach. Traffic circle was restriped to a 3-lane roundabout.

I can't think of many places in the states off the top of my head with a 3+ lane roundabout. If there's enough traffic to require three lanes, I'd think that some of the benefits would be reduced.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on October 14, 2015, 09:35:34 AM
What's funny is that many places critical about the introduction of roundabouts think they're great 10-15 years later. I'll give an example from my hometown in Warren County, NY. About 10 years ago, NYSDOT put in a roundabout to replace the 5 way signalized intersection between US 9, NY 9L, and NY 32 at the center of Glens Falls. At first, everyone hated it. Then people realized that the once-common traffic issues were no more, it was easier to walk around downtown, and it put a nice centerpiece in a traditional New England-style town square. Last year, a new roundabout was installed in the town of Queensbury on Aviation Road about 1/2 mile west of I-87 Exit 19, replacing a dangerous acute angle intersection. Now, local media and residents are pushing to have more roundabouts installed in the area, notably in the vicinity of I-87 Exit 20.

The roundabouts you are referencing are single-lane roundabouts.  Driver's don't have too much trouble with those.  When the region constructs a complex multi-lane roundabout, that's when you might run into problems. 


At least in New York, anything larger than a two-lane roundabout gets scoffed at.  Not sure if we have anything larger than a two-lane roundabout here, but I know they've been outright avoided at significant cost (Washington Ave/Fuller Rd in Albany was considered for a three-lane roundabout before going with a smaller roundabouts and an overpass).

Jones Beach. Traffic circle was restriped to a 3-lane roundabout.


Go figure.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 14, 2015, 11:46:17 AM

And if you compare those roundabouts to the signals they replaced, the roundabouts are (more than likely) safer. There is nothing wrong with the occasional fender-bender. You can't eliminate those. What you can do, is mitigate severe collisions by removing the possibility of high-speed impacts altogether. Carmel is, according to Brainard (based on my quoted text above), safer as a result of these roundabouts. There may be more collisions, but they are nowhere near as severe as the ones before.

My point being, safety is measured by more than just the number of collisions at an intersection.

Listing intersections with the highest crash rate is common when agencies perform annual safety audits.  In many cases, agencies are required to investigate further any intersection that exceeds a predefined critical crash rate.  In the case of WisDOT this critical rate is 2.0 MVE (the same as Sarasota County).  When this threshold is met at a roundabout, agencies may attempt to restripe/resign the roundabout or remove circulating lanes to simplify the operation.  Several examples of removing circulating lanes have already been cited in this thread:

-14th Street & Superior in Lincoln, Nebraska (3x2 reduced to 2x2)
-Maple & Drake in Farmington Hills, Michigan (3x2 reduced to 2x2)
-Maple & Farmington in Farmington Hills, Michigan (3x2 reduced to 2x2)
-Homer Watson Boulevard and Block Line Road in Kitchener, Ontario (3x2 reduced to 2x2)
-Bailey & Radio in Woodbury, Minnesota (2x2 reduced to 2x1)
-Broadway Avenue & Lake Street in Forrest Lake, Minnesota (2x2 reduced to 1x1)
-Main Ave & Broadway in De Pere, Wisconsin (2x2 reduced to 2x1)

Agencies are just following the rules that have been put into place.  If there is a roundabout that exceeds the critical crash rate and nothing is done about it, they are liable to get sued.  I know you believe crash severity is important Jake, and it is, but there are other factors at play here. 
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on October 14, 2015, 03:20:37 PM
http://www.wthr.com/story/30254415/round-and-round-carmel-man-sets-out-to-set-roundabout-driving-record
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 17, 2015, 02:45:06 PM
The roundabout at Livernois & Hamlin in Rochester Hills, Michigan was constructed in 2010.  Since its completion, there has been an increase in both injury and Property Damage Only (PDO) crashes.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/HamlinampLivernois_zps3b3hh65o.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 19, 2015, 05:29:53 PM
A multi-lane roundabout was constructed at Hillsborough Street and Pullen Road near North Carolina State University in 2010.  After 132 fender-benders in two years, they converted it to a single-lane roundabout in 2012.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/roundabout-intersection-crashes_zpsbj1ugdeu.jpg)

http://www.wral.com/traffic/story/11369528/
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 19, 2015, 05:56:42 PM
What are the traffic flow numbers along Hillsborough Street?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 19, 2015, 07:48:19 PM
What are the traffic flow numbers along Hillsborough Street?

According to the 2013 Annual Average Daily Traffic Map, Hillsborough Street corridor had an AADT of 15,000.  The Hillsborough St./Pullen Rd. roundabout averaged 66 crashes per year when it was a multi-lane roundabout. 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Random/TrafficVolumeRaleigh_zpsfvl908uz.png)
www.ncdot.gov/travel/statemapping/trafficvolumemaps/default.html
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 19, 2015, 07:52:35 PM
In addition to the increase in total crashes, the Hillsborough Street roundabout had a 29% increase in injury crashes:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Random/untitledHillsboroughRoundabout_zpswhhjpl2z.png)
https://connect.ncdot.gov/resources/safety/Safety%20Evaluation%20Projects/Roundabout%20Presentation%20with%20Notes.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 19, 2015, 08:17:09 PM
In addition to the increase in total crashes, the Hillsborough Street roundabout had a 29% increase in injury crashes:

Well, at least the severity dropped. Any fatalities before or after?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 19, 2015, 10:54:50 PM
Well, at least the severity dropped. Any fatalities before or after?

There's no mention of fatal crashes occurring in the study.  The severity index is a weighted average of fatal, injury, and PDO crashes.  An intersection with a low severity index can have more injury accidents than an intersection with a high severity index; assuming the total crashes are disproportionately high at the low severity index intersection.  I believe this is the equation used in the Hillsborough roundabout study:

Severity Index = (76 * F + 8.2 * I + 1* PDO) / N

Where,
F = total number of fatal crashes
I = total number of injury crashes
PDO = total number of personal damage only crashes
N = total number of crashes
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 21, 2015, 09:32:59 PM
The roundabout at SC 46 and Bluffton Parkway in Bluffton, SC was converted to a 2x2 roundabout in 2011 (previously 2x1).  After the conversion, the roundabout experienced a higher than expected crash rate.  As a result of the high crash rate, roundabout experts were asked by the FHWA Offices of Safety Peer-to-Peer program to review and provide low-cost modifications to improve safety.  Per the review, pavement marking changes were made in December, 2012.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/SCroundabout_zpslgjjevwy.png)

http://static1.squarespace.com/static/51cc8d46e4b0b242fc8d0f33/t/55c4febce4b03a1fdb5cadfc/1438973628373/24.+Roundabout+Design+Optimization+for+Safety+and+Operations.pdf

It initially appeared the pavement marking changes were successful at reducing crashes.  There were only 2 crashes at the roundabout the first 6 months after modifications (12/13/12 through 6/1/13).  In 2014, however, there were 30 total crashes including 7 injury collisions.  Ultimately, the Bluffton Parkway roundabout still has a high crash rate and an alarming number of injury collisions in 2014.  The expert modifications done in 2012 hasn't solved the problem.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/SCroundaboutcrashdata_zpsmsfjddtn.png)

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/SCroundabout2015crashdata_zps39uwro3y.png)

http://www.islandpacket.com/news/local/traffic/article33716778.html
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 22, 2015, 05:36:37 PM
After reading through this thread from start to finish, I will agree that there does seem to be discrepancies from what the engineers say to what reality says. But, I'm not sure what the fix is. I'm still convinced that roundabouts get safer with time (which is hard to measure though, since AADT numbers almost always rise with time, so naturally the number of collisions will rise), but do you think we are building too many roundabouts? Would you prefer more signals? Honest question, no premeditation here. I just want to hear what you think the solution to this problem is.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on October 22, 2015, 06:16:40 PM
After reading through this thread from start to finish, I will agree that there does seem to be discrepancies from what the engineers say to what reality says. But, I'm not sure what the fix is. I'm still convinced that roundabouts get safer with time (which is hard to measure though, since AADT numbers almost always rise with time, so naturally the number of collisions will rise), but do you think we are building too many roundabouts? Would you prefer more signals? Honest question, no premeditation here. I just want to hear what you think the solution to this problem is.

I'd say build more roundabouts, and educate people how to use them, I guarantee most accidents are because people have no idea what they're doing in them.  Signals are annoying.  Moving from the stop light obsessed Indianapolis to Carmel, I finally see why Brainard is obsessed with them, traffic is so much better.  However, I do admit that roundabouts do not work everywhere though.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 23, 2015, 05:40:13 PM
There are 94 roundabouts and counting in Carmel, Indiana.  Of these 94 roundabouts, there are only four multi-lane roundabouts that have two-circulating lanes throughout the entire circle.  Here is crash data for Carmel’s 2x2 multi-lane roundabouts:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Carmel116thKeystone_zpsmcrormht.png)

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/CarmeCarmel_zpsqeit3r6w.png)

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/CarmelSpringMill_zpsszypdosv.png)

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/CarmelIllinois_zps5lalomr0.png)

Drivers are having trouble navigating the higher capacity multi-lane roundabouts in Carmel.   The roundabout at 116th & Keystone Pkwy averaged 64.3 crashes a year since 2011.  The AADT of 116th Street at Keystone was 20,463 according to Hamilton County’s 2011 traffic count data.  This equates to a crash rate of 8.7 which is off the charts (an intersection crash rate over 2.0 is often considered ”˜critical’ and warrants further investigation).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 23, 2015, 05:41:31 PM
After reading through this thread from start to finish, I will agree that there does seem to be discrepancies from what the engineers say to what reality says. But, I'm not sure what the fix is. I'm still convinced that roundabouts get safer with time (which is hard to measure though, since AADT numbers almost always rise with time, so naturally the number of collisions will rise), but do you think we are building too many roundabouts? Would you prefer more signals? Honest question, no premeditation here. I just want to hear what you think the solution to this problem is.

I don’t believe America is building too many roundabouts.  The majority of single-lane and 2x1 multi-lane roundabouts function well and don't have high crash rates.  What has happened is more complex multi-lane (2x2) roundabouts have been constructed in recent years, and these are the roundabouts that are seeing high crash rates.  The good thing is these roundabouts are being monitored closely.  Agencies are addressing these high crash rate roundabouts by eliminating circulating lanes and experimenting with signage/pavement marking changes (many examples of this have already been mentioned on this thread).   
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 23, 2015, 05:58:24 PM
Drivers are having trouble navigating the higher capacity multi-lane roundabouts in Carmel.   The roundabout at 116th & Keystone Pkwy averaged 64.3 crashes a year since 2011.  The AADT of 116th Street at Keystone was 20,463 according to Hamilton County’s 2011 traffic count data.  This equates to a crash rate of 8.7 which is off the charts (an intersection crash rate over 2.0 is often considered ”˜critical’ and warrants further investigation).

I'm sorry trade, but I just don't think anyone cares. Carmel has basically reduced their traffic fatalities to zero (so far as I know), and they don't have any traffic congestion. If the trade-off is a slight increase in collisions, by all means, most people will take the increase in collisions. But you'll be hard-pressed to find anyone in Carmel who would prefer a traffic signal, with its backups and t-bone collisions. I mean, of course traffic signals have less collisions. They're really fucking easy to navigate (red means stop, green means go), but that doesn't automatically mean it's the preferred choice for multi-lane intersections, just because there's fewer collisions.

It should be noted that Carmel's population has increased by 62% since 2000. Perhaps traffic engineers take a different approach, but personally, I've always viewed the number of collisions at an intersection as a factor of the amount of cars going through it. It should be well established that there are many gaffe-prone drivers out there, so intersections with more people are likely to have to more of these gaffe-prone drivers going through them at any given moment. Given this, it should be no surprise that the busier intersections have more collisions -- there's just more cars.

I don’t believe America is building too many roundabouts.  The majority of single-lane and 2x1 multi-lane roundabouts function well and don't have high crash rates.  What has happened is more complex multi-lane (2x2) roundabouts have been constructed in recent years, and these are the roundabouts that are seeing high crash rates.  The good thing is these roundabouts are being monitored closely.  Agencies are addressing these high crash rate roundabouts by eliminating circulating lanes and experimenting with signage/pavement marking changes (many examples of this have already been mentioned on this thread).

If you take into account my point above, there are more cars in a two or three lane roundabout at any given time than a single lane roundabout. It should be no surprise that there are more collisions -- there's more cars!
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 24, 2015, 02:40:33 AM
The crash rate measures the number of crashes at an intersection per million entering vehicles.  Engineers like to see crash rates below 2.0 MEV.  What are the crash rates for the following intersections Jake?

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/BBcrash7_zpsxolkyssw.png)

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/BBcrashdata_zpsdswiwuqc.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 26, 2015, 05:02:54 AM
The crash rate measures the number of crashes at an intersection per million entering vehicles.  Engineers like to see crash rates below 2.0 MEV.  What are the crash rates for the following intersections Jake?

Fuck if I know. I'm horrible at math. But I do know that the Troy junction does not permit left or U-turns, so comparing the two is like comparing apples to oranges. The bottom intersection is not necessarily a full-fledged four-way junction like the roundabout.

Then again, my theory from my previous post is just that: a theory. I didn't attempt to back it up with evidence. It's just a hunch. I can't imagine it's always true (that is, busier intersections have more collisions).

But, still, I maintain that the crash rate is far less important than the death rate. Very few of your stats ever show fatalities (and if they do, it's usually zero for both before and after the roundabout). At that point, it should come down to A) when possible, avoiding the intersection design which has the likelihood of creating the greatest potential for death, and B) which intersection design has the best vehicle through-put.

Now, I've basically created my own criteria by which I judge safety (which may or may not be a straw-man). But, I do more than likely represent the majority of people, who would take an uptick in collisions if it meant basically eliminating traffic fatalities.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 26, 2015, 05:50:00 AM
Can you please analyze some of Washington's roundabouts? As usual, I have no idea where to find those AADT numbers, nor the crash rates. I know back on the first or second page, you pulled some numbers for some roundabouts in Washingotn, but the numbers were over a decade old, and I'm interested to see whether or not any new developments have occurred since then.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 26, 2015, 12:16:03 PM
The Bluffton roundabout has a crash rate of 3.41 which is 4X the average crash rate of signalized intersections.  This is more than just a ”˜slight increase in collisions'.  The injury crash rate at the Bluffton roundabout is 0.54 which is approaching the total crash rate of signalized intersections.  It’s not a good result.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/avgcrashrate_zpsttjvtneh.png)
https://www.massdot.state.ma.us/highway/Departments/TrafficandSafetyEngineering/CrashData/CrashRates/Intersection.aspx

I'm sorry trade, but I just don't think anyone cares. Carmel has basically reduced their traffic fatalities to zero (so far as I know), and they don't have any traffic congestion. If the trade-off is a slight increase in collisions, by all means, most people will take the increase in collisions. But you'll be hard-pressed to find anyone in Carmel who would prefer a traffic signal, with its backups and t-bone collisions. I mean, of course traffic signals have less collisions. They're really fucking easy to navigate (red means stop, green means go), but that doesn't automatically mean it's the preferred choice for multi-lane intersections, just because there's fewer collisions.

Carmel has seen a drop in injury accidents and city officials attribute the drop in to its roundabout-building initiative.  I’m not surprised as the vast majority of Carmel roundabouts function well.  However, there are a handful of Carmel roundabouts with high crash rates.  These problematic roundabouts are the 2x2 multi-lane ones that have been cited so prevalently throughout this thread.  Should we ignore the Carmel roundabouts with high crash rates just because most of the roundabouts in the city work well?    There are lessons to be learned from these high crash rate roundabouts.

The generic roundabout safety statistics should maybe read like this…

-40% reduction in total crashes….
-80% reduction in injury crashes…
-90% reduction in fatal crashes…..
 
*except for 2x2 multi-lane roundabouts.  These will see a significant increase in total crashes and the reduction in injury crashes will be questionable at best.  Signage and pavement marking tweaks will be made to the roundabout in a vain attempt to reduce the high crash rate.  Engineers, perplexed with why there are so many crashes, will eventually say “screw it”  and eliminate circulating lanes inside the roundabout as a last ditch effort to reduce the high crash rate.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 26, 2015, 03:17:49 PM
Can you please analyze some of Washington's roundabouts? As usual, I have no idea where to find those AADT numbers, nor the crash rates. I know back on the first or second page, you pulled some numbers for some roundabouts in Washingotn, but the numbers were over a decade old, and I'm interested to see whether or not any new developments have occurred since then.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/BellinghamRB_zps3pdtzhyx.png)

Here’s one that hasn’t been discussed yet.  In 2002, the City of Bellingham constructed a roundabout at the intersection of Cordata Parkway & Kellogg Road near Whatcom Community College.  In 2008, after 6 years of operation, the roundabout had the highest accident rate in Bellingham with 17 total crashes.  In 2009 there were 18 crashes.  According to the Whatcom County traffic counts, the roundabout has an AADT of 15,200.  This equates to a crash rate of 3.15.

http://wcog.org/wp-content/uploads/documents/2012TrafficCountManual.pdf
http://www.whatcomhorizon.com/2010/04/roundabout-confusion/
Title: Re: Crash prone 'modern roundabouts'
Post by: ScottRAB on October 26, 2015, 03:43:49 PM
The one at US-101/OR-202 in Astoria has, over the long term, resulted in a 150% increase in crashes, without any reduction in accident severity

Even worse is the one at MLK Pkwy, Pioneer Parkway, and Hayden Bridge Way in Springfield.  It cost almost $10 million to build, and it had almost 200 accidents between 2009 and 2013, with volumes only running 15,000-20,000 ADT. 

Can you provide us a reference for your data?  One we can independently verify?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 28, 2015, 01:12:56 PM
The one at US-101/OR-202 in Astoria has, over the long term, resulted in a 150% increase in crashes, without any reduction in accident severity

Even worse is the one at MLK Pkwy, Pioneer Parkway, and Hayden Bridge Way in Springfield.  It cost almost $10 million to build, and it had almost 200 accidents between 2009 and 2013, with volumes only running 15,000-20,000 ADT. 

Can you provide us a reference for your data?  One we can independently verify?

According to a City of Springfield report, the multi-lane roundabout at MLK Parkway & Hayden Bridge Way had a crash rate of 2.91; nearly 3x higher than the next crash rate intersection in the city.  Refer to pages 30-32:

(http://alexforfg.com/wp-content/uploads/2014/12/springfieldtsp.jpg)
http://www.centrallanertsp.org/sites/default/files/Volume%203,%20Appendix%20B,%2001.09.14-web_0.pdf

Oregon's crash data system can be found in the link below if you want to independently verify the crashes that are occurring. 
https://zigzag.odot.state.or.us/uniquesig08615cf883bed667d26bcec3a7dc5c6b/uniquesig0/SecurezigzagPortalHomePage/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 30, 2015, 02:10:55 AM
Here’s a list of multi-lane roundabouts sorted by crash rate.  Most of the roundabouts on this list have already been discussed and the data can be verified digging through the links in this thread.  Rows highlighted in yellow have had circulating lanes removed in an attempt to address the high crash rate.  The average crash rate at signalized intersections is about 0.8 MEV.  The crash rate at these multi-lane roundabouts exceeds the average crash rate at signalized intersections by a big margin.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/crashrate_zpsglb8qh4x.png)

Not all multi-lane roundabouts have high crash rates.  In the graph below, the 2x1 roundabouts have low crash rates while the 2x2 roundabouts have high crash rates. The exception is the 2x1 roundabout at Diffley & Rahn.  This roundabout has a central island diameter of 80’ which is the smallest CID of any of the Minnesota roundabouts analyzed.  It’s my belief that if a roundabout is too small, drivers have difficulty judging gaps to safely enter the roundabout.  The small CID may be a plausible reason why the 2x1 roundabout at Diffley & Rahn has a high crash rate.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/MNrbs_zpsx3wr39yq.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 30, 2015, 12:11:01 PM
The one at US-101/OR-202 in Astoria has, over the long term, resulted in a 150% increase in crashes, without any reduction in accident severity

Even worse is the one at MLK Pkwy, Pioneer Parkway, and Hayden Bridge Way in Springfield.  It cost almost $10 million to build, and it had almost 200 accidents between 2009 and 2013, with volumes only running 15,000-20,000 ADT. 

Can you provide us a reference for your data?  One we can independently verify?

ScottRAB, what's your take on these 2x2 multi-lane roundabouts?  The generic safety stats say there will be a 40% drop in total crashes but that's not what we are seeing with these multi-lane roundabouts.  More concerning, several of the 2x2 multi-lane roundabouts have seen injury accidents increase. 
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on November 02, 2015, 08:50:00 PM
The one at US-101/OR-202 in Astoria has, over the long term, resulted in a 150% increase in crashes, without any reduction in accident severity

Even worse is the one at MLK Pkwy, Pioneer Parkway, and Hayden Bridge Way in Springfield.  It cost almost $10 million to build, and it had almost 200 accidents between 2009 and 2013, with volumes only running 15,000-20,000 ADT. 

Can you provide us a reference for your data?  One we can independently verify?

These are taken directly from ODOT's crash reporting system.  Plugging in the same dates, the data is replicable.

Here's all the source data from US-101/OR-202 Astoria.  The Pre-Roundabout Period runs from 10/1/1993 to 09/30/2002, while the Post-Roundabout Period runs 10/1/2002 to 09/30/2011.

Astoria Pre-Roundabout KABCO (http://alexforfg.com/wp-content/uploads/2014/10/Astoria-PreRoundabout-KABCO.pdf)
Astoria Pre-Roundabout Comprehensive (http://alexforfg.com/wp-content/uploads/2014/10/Astoria-PreRoundabout-Comp.pdf)
Astoria Pre-Roundabout Truck Included (http://alexforfg.com/wp-content/uploads/2014/10/Astoria-Roundabout-TruckIncluded.pdf)
Astoria Post-Roundabout KABCO (http://alexforfg.com/wp-content/uploads/2014/10/Astoria-Roundabout-KABCO.pdf)
Astoria Post-Roundabout Comprehensive (http://alexforfg.com/wp-content/uploads/2014/10/Astoria-Roundabout-Comp.pdf)
Astoria Post-Roundabout Truck Included (http://alexforfg.com/wp-content/uploads/2014/10/Astoria-PreRoundabout-TruckIncluded.pdf)

The data showing over 180 crashes between 2009 and 2013 at the Springfield Pioneer/MLK/Hayden Bridge roundabout is below.  Because there's multiple road names involved, ODOT has the data divided by approach, requiring one to add everything up to get the full picture.

Pioneer Pkwy W and Hayden Bridge KABCO (http://alexforfg.com/wp-content/uploads/2014/12/Pioneer-Pkwy-W-and-Hayden-Bridge-KABCO.pdf)
Pioneer Pkwy E and Hayden Bridge KABCO (http://alexforfg.com/wp-content/uploads/2014/12/Pioneer-Pkwy-E-and-Hayden-Bridge-KABCO.pdf)
MLK and Hayden Bridge KABCO (http://alexforfg.com/wp-content/uploads/2014/12/MLK-and-Hayden-Bridge-KABCO.pdf)

Neither Springfield nor Lane County has good volume data on the intersection beyond the earlier Springfield TSP figures.  The most recent Springfield data is from 2008 (http://www.ci.springfield.or.us/pubworks/transportation/Images/Maps/ADT_MAP_2008%2011%20x%2017%20%281%29.pdf) and only shows the approaches.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 03, 2015, 11:28:45 AM
Some 2x2 multi-lane roundabouts were constructed along Shiloh Rd in Billings, Montana in 2010.  According to the Billings Police Department, the roundabout at Shiloh & Grand is currently the 8th most dangerous intersection in the city and the roundabout at Shiloh & King is the 4th most dangerous intersection in the city. 

http://billingsgazette.com/news/local/crime-and-courts/crime-stats-billings-most-dangerous-intersections/collection_97fee293-e4d2-5dac-8854-ceb50a22f030.html


Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 03, 2015, 12:48:02 PM
Here’s an interesting case study.  Pre-2008 Cony Circle in Augusta, Maine averaged over 100 crashes per year and was the highest crash rate intersection in the state.  In 2008, the circle was reconfigured with modern roundabout standards.  After the conversion accidents dropped by 50%.  That may sound impressive, but as of 2014 the roundabout has a crash rate of 11.87 and is still the 3rd highest crash location in Maine.  Is that really a victory?  It’s similar to an 800 pound person losing 50% of their body weight.  They are still morbidly obese. 

http://www.centralmaine.com/2011/08/11/cony-circle-accidents-down_2011-08-10/
http://www.wgme.com/images/DANGEROUS%20ROADWAY%20INTERSECTIONS.pdf

Cony Circle:  Pre-2008
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/08-Untitled_zpshnpikktf.png)

Cony Circle:  Post-2008
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/15Untitled_zpsl7d1abyq.png)

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 03, 2015, 02:25:05 PM
Some 2x2 multi-lane roundabouts were constructed along Shiloh Rd in Billings, Montana in 2010.  According to the Billings Police Department, the roundabout at Shiloh & Grand is currently the 8th most dangerous intersection in the city and the roundabout at Shiloh & King is the 4th most dangerous intersection in the city. 

http://billingsgazette.com/news/local/crime-and-courts/crime-stats-billings-most-dangerous-intersections/collection_97fee293-e4d2-5dac-8854-ceb50a22f030.html

Any idea why the most dangerous intersections are signals?

Here’s an interesting case study.  Pre-2008 Cony Circle in Augusta, Maine averaged over 100 crashes per year and was the highest crash rate intersection in the state.  In 2008, the circle was reconfigured with modern roundabout standards.  After the conversion accidents dropped by 50%.  That may sound impressive, but as of 2014 the roundabout has a crash rate of 11.87 and is still the 3rd highest crash location in Maine.  Is that really a victory?  It’s similar to an 800 pound person losing 50% of their body weight.  They are still morbidly obese.

I'm not sure there are any other effective ways to intersect five roads that wouldn't cause outrageous congestion.

What are the top two intersections?

Here’s one that hasn’t been discussed yet.  In 2002, the City of Bellingham constructed a roundabout at the intersection of Cordata Parkway & Kellogg Road near Whatcom Community College.  In 2008, after 6 years of operation, the roundabout had the highest accident rate in Bellingham with 17 total crashes.  In 2009 there were 18 crashes.  According to the Whatcom County traffic counts, the roundabout has an AADT of 15,200.  This equates to a crash rate of 3.15.
http://www.whatcomhorizon.com/2010/04/roundabout-confusion/

This got me thinking:

Is the crash rate an effective means of studying intersection safety? By your measure, the roundabout featured here would be considered dangerous, but that's only because of the "3.15" number. In real life, 17 or 18 collisions just isn't that many (that's one every three weeks, give or take, and there's no telling how severe the collisions were). An intersection with an AADT of 50,000 with a crash rate of 3.15 would have fewer collisions per number of cars entering, but still way more collisions than 17 or 18 a year.

Now, if that's okay simply because more cars = more collisions, that's been my point all along. Multi-lane roundabouts are, obviously, capable of handling far more cars than single-lane roundabouts, simply because there are more circulating lanes, thus more cars in the intersection at any given point capable of whacking into each other. Considering that, I propose that three lane roundabouts are no more dangerous than two or one lane roundabouts. They just handle an enormous amount of cars relative to the smaller roundabouts, so they appear to be much more dangerous. If a traffic engineers' only method of making an intersection safer is by reducing the theoretical through-put of an intersection, simply to lessen the chances of a collision by decreasing the amount of cars in the intersection that could theoretically collide, you're not solving any problems. That's just a trade-off.

Now, I could be looking at this all wrong. I am, after all, not a traffic engineer, nor an expert in analyzing data.

As well (perhaps unrelated), please don't compare roundabouts with Michigan Lefts, as you have before. I love Michigan Lefts just as much as the next person, but the ROW required to install them is usually far more than most agencies can provide. I don't find see them in the same category as roundabouts or traditional signals (they're more like freeways -- a series of intersections working in tandem to filter traffic along a central artery).
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on November 03, 2015, 03:16:02 PM
I'm not sure there are any other effective ways to intersect five roads that wouldn't cause outrageous congestion.

I'll be upfront and say I'm typically not a fan of roundabouts, for various reasons, but one of the places they do make sense is situations with unusual geometry, that would be messy with a more "conventional" treatment.  There's one caveat to the particular Maine intersection being mentioned, however, that I'll note later.

Here’s one that hasn’t been discussed yet.  In 2002, the City of Bellingham constructed a roundabout at the intersection of Cordata Parkway & Kellogg Road near Whatcom Community College.  In 2008, after 6 years of operation, the roundabout had the highest accident rate in Bellingham with 17 total crashes.  In 2009 there were 18 crashes.  According to the Whatcom County traffic counts, the roundabout has an AADT of 15,200.  This equates to a crash rate of 3.15.
http://www.whatcomhorizon.com/2010/04/roundabout-confusion/

Now, if that's okay simply because more cars = more collisions, that's been my point all along. Multi-lane roundabouts are, obviously, capable of handling far more cars than single-lane roundabouts, simply because there are more circulating lanes, thus more cars in the intersection at any given point capable of whacking into each other. Considering that, I propose that three lane roundabouts are no more dangerous than two or one lane roundabouts. They just handle an enormous amount of cars relative to the smaller roundabouts, so they appear to be much more dangerous. If a traffic engineers' only method of making an intersection safer is by reducing the theoretical through-put of an intersection, simply to lessen the chances of a collision by decreasing the amount of cars in the intersection that could theoretically collide, you're not solving any problems. That's just a trade-off.

Now, I could be looking at this all wrong. I am, after all, not a traffic engineer, nor an expert in analyzing data.

The MEV abbreviation that tradephoric and others have used in this thread stands for "per million entering vehicles".  In short It's actually a way of getting a crash rate that is not dependent on the actual traffic volume, and allows engineers to better compare intersections.  An intersection with a crash rate of 3.15 per MEV need not necessarily have a higher volume of traffic than one with a rate of 0.90 per MEV, but it does mean statistically that the 3.15 per MEV intersection is going to be a bit more than three times as crash prone.

All these high MEV ratings for multi-lane roundabouts are essentially showing that once you get beyond 1x1 or 2x1 roundabouts, into roundabout treatments for higher-volume situations, the safety benefits quickly become null and void.  Cost also becomes a factor--the MLK/Hayden Bridge roundabout in Springfield cost over $9 million to construct.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 03, 2015, 03:24:18 PM
The MEV abbreviation that tradephoric and others have used in this thread stands for "per million entering vehicles".  In short It's actually a way of getting a crash rate that is not dependent on the actual traffic volume, and allows engineers to better compare intersections.  An intersection with a crash rate of 3.15 per MEV need not necessarily have a higher volume of traffic than one with a rate of 0.90 per MEV, but it does mean statistically that the 3.15 per MEV intersection is going to be a bit more than three times as crash prone.

Thank you for clarifying that. I had a feeling I was missing a piece of the puzzle.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on November 03, 2015, 03:39:13 PM
All these high MEV ratings for multi-lane roundabouts are essentially showing that once you get beyond 1x1 or 2x1 roundabouts, into roundabout treatments for higher-volume situations, the safety benefits quickly become null and void.  Cost also becomes a factor--the MLK/Hayden Bridge roundabout in Springfield cost over $9 million to construct.

The overall crash rate benefits may be "null and void," but these high volume intersections that require a multilane solution are the ones that lead to the vast majority of fatality crashes when they're signalized or have multi-way stop conditions. Without getting into the weeds of cost-benefit analysis,* a few more (or even many more) fender benders and whiplash accidents are massively preferable to a few more deaths from people being T-boned by red-light runners and the like.

* If we take the value of a human life at somewhere between $8-10 million (https://www.transportation.gov/sites/dot.gov/files/docs/VSL_Guidance_2014.pdf), even several hundred more accidents at $5-10k a pop would be "worth" it.
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on November 03, 2015, 06:29:35 PM
Without getting into the weeds of cost-benefit analysis,* a few more (or even many more) fender benders and whiplash accidents are massively preferable to a few more deaths from people being T-boned by red-light runners and the like.

In theory, yes--signalized intersections aren't "childproofed" with all those rounded edges, allowing the potential for those types of angle crashes--though theory and the actual real-world results don't always correlate, and that's one of the main arguments being discussed in this thread.  Many of the cases cited in this thread, where multi-lane roundabouts have replaced signals, have shown increases in injury accidents as well as total accidents, even over the longer term.  Curiously, I've yet to see a comparison involving a fatality on either side (pre- or post-multi-lane roundabout), however.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 03, 2015, 07:06:14 PM
Without getting into the weeds of cost-benefit analysis,* a few more (or even many more) fender benders and whiplash accidents are massively preferable to a few more deaths from people being T-boned by red-light runners and the like.

In theory, yes--signalized intersections aren't "childproofed" with all those rounded edges, allowing the potential for those types of angle crashes--though theory and the actual real-world results don't always correlate, and that's one of the main arguments being discussed in this thread.  Many of the cases cited in this thread, where multi-lane roundabouts have replaced signals, have shown increases in injury accidents as well as total accidents, even over the longer term.  Curiously, I've yet to see a comparison involving a fatality on either side (pre- or post-multi-lane roundabout), however.

It's a matter of high-speed impacts vs low-speed impacts. There can be injuries in both, of course, but it's more like whiplash vs broken back, or bump on the head vs broken legs. Unfortunately for us, both injuries get lumped together, even though 100% of people would prefer the former two over the latter two.

Carmel, Indiana, according to their mayor Jim Brainard, does not have a full Jaws of Life in their city because they don't really have severe collisions anymore (this was on the last page):

http://wishtv.com/2015/10/08/roundabouts-may-confuse-but-stats-back-up-their-safety/

Quote
And even if you make a mistake, because speeds are so slow, most wrecks don’t involve serious injuries....[Carmel Mayor Jim Brainard] points out that because accidents and injuries are down in Carmel, insurance rates have dropped. He says the city doesn’t have a full “jaws of life”  crew in its fire department anymore because they don’t have the high speed impacts that they used to have and don’t need them very often.

The issue that tradephoric likes to bring up is negligence. He states repeatedly that cities can be found negligent if they knowingly do nothing about intersections that have high crash rates. I would agree that there could be a negligence issue. The problem is that A) no one political body has power over a city's engineering department, thus there's no one that could single-handily bar any further roundabout construction, or more importantly B) while a citizen could privately sue the city for negligence after receiving a minor injury in the roundabout, any city which has invested millions of dollars into roundabouts would go to huge lengths to protect their investments in court, by providing evidence to a judge and jury, demonstrating that while there may be more collisions, the roundabouts are actually safer (in terms of both fatalities and severe injuries).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 03, 2015, 10:47:31 PM
It's a matter of high-speed impacts vs low-speed impacts. There can be injuries in both, of course, but it's more like whiplash vs broken back, or bump on the head vs broken legs. Unfortunately for us, both injuries get lumped together, even though 100% of people would prefer the former two over the latter two.

There is a rating system known as FARS (Fatality Analysis Reporting System) that is used to code injury accidents by severity.  Here’s a breakdown of the rating system:

Quote
0 No Injury (O)
1 Possible Injury (C)
2 Non-incapacitating Evident Injury (B)
3 Incapacitating Injury (A)
4 Fatal Injury (K)
5 Injured, Severity Unknown
6 Died Prior to Accident*
9 Unknown

Code 1 (Possible Injury). A possible injury is any injury reported or claimed which is not a fatal injury, incapacitating injury or non-incapacitating evident injury. This includes: momentary unconsciousness, claim of injuries not evident, limping, complaint of pain, nausea and hysteria.

Code 2 (Non-incapacitating Evident Injury). A non-incapacitating evident injury is any injury, other than a fatal injury or an incapacitating injury, which is evident to observers at the scene of the accident in which the injury occurred. This includes: lump on head, abrasions, bruises and minor lacerations. This does not include limping (the injury cannot be seen). (See code “1” ).

Code 3 (Incapacitating Injury). An incapacitating injury is any injury, other than a fatal injury, which prevents the injured person from walking, driving or normally continuing the activities the person was capable of performing before the injury occurred. This includes: severe lacerations, broken or distorted limbs, skull or chest injuries, abdominal injuries, unconsciousness at or when taken from the accident scene, and unable to leave the accident scene without assistance. This does not include momentary unconsciousness. (See code “1” ).

Code 4 (Fatal Injury), must only be used if the death occurred within thirty 24-hour time periods from the time of the accident. Every effort should be made to determine that the Death Date was within thirty 24-hour time periods from the Accident Time.

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 03, 2015, 11:14:31 PM
It's a matter of high-speed impacts vs low-speed impacts. There can be injuries in both, of course, but it's more like whiplash vs broken back, or bump on the head vs broken legs. Unfortunately for us, both injuries get lumped together, even though 100% of people would prefer the former two over the latter two.

There is a rating system known as FARS (Fatality Analysis Reporting System) that is used to code injury accidents by severity.  Here’s a breakdown of the rating system:

Thank you for posting that. I figured there might be something, but I hadn't heard of anything until now. How often is crash data compiled with FARS' numbers?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 04, 2015, 12:13:22 AM
Thank you for posting that. I figured there might be something, but I hadn't heard of anything until now. How often is crash data compiled with FARS' numbers?

In Michigan, the FARS code is compiled for every reported traffic crash in the state.  Law enforcement agencies are required to complete a UD-10 which includes the FARS code.  Below is a link to a sample UD-10 which shows injury severity ranging from no injury (Unit 1 driver) to A-level injury (Unit 1 passenger):

http://semcog.org/Data-and-Maps/Crash-and-Road-Data/Crash_Id/8338533/view/UD10CrashReport

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 04, 2015, 12:15:37 PM
The overall crash rate benefits may be "null and void," but these high volume intersections that require a multilane solution are the ones that lead to the vast majority of fatality crashes when they're signalized or have multi-way stop conditions. Without getting into the weeds of cost-benefit analysis,* a few more (or even many more) fender benders and whiplash accidents are massively preferable to a few more deaths from people being T-boned by red-light runners and the like.

* If we take the value of a human life at somewhere between $8-10 million (https://www.transportation.gov/sites/dot.gov/files/docs/VSL_Guidance_2014.pdf), even several hundred more accidents at $5-10k a pop would be "worth" it.

Compare the 2014 traffic fatalities that occurred in Sterling Heights, MI and Carmel, IN.  Sterling Heights has a population of 130,410 and Carmel has a population of 85,927.  Both communities experienced 2 fatal crashes in 2014 (based on google searches and UD-10 forms).  Ironically, the two fatal crashes that occurred in Carmel happened inside roundabouts.  Neither fatality in Sterling Heights occurred at an intersection (according to the UD-10 forms).  Keep in mind, Sterling Heights has a population nearly 45k higher than Carmel.   I thought roundabouts reduce fatal crashes by 90%.  How then did Sterling Heights, a city full of traffic signals, have zero fatal intersection crashes while Carmel, a city full of roundabouts,  have 2 fatal roundabout crashes?

Fatal crashes in Carmel:
http://fox59.com/2014/08/06/one-dead-in-carmel-accident-passenger-taken-to-hospital/
http://fox59.com/2014/09/26/person-dead-after-motorcycle-accident-in-carmel/

Fatal crashes in Sterling Heights:
http://semcog.org/Data-and-Maps/Crash-and-Road-Data/Crash_Id/8939474/view/UD10CrashReport
http://semcog.org/Data-and-Maps/Crash-and-Road-Data/Crash_Id/8986238/view/UD10CrashReport
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 04, 2015, 08:19:46 PM
The overall crash rate benefits may be "null and void," but these high volume intersections that require a multilane solution are the ones that lead to the vast majority of fatality crashes when they're signalized or have multi-way stop conditions. Without getting into the weeds of cost-benefit analysis,* a few more (or even many more) fender benders and whiplash accidents are massively preferable to a few more deaths from people being T-boned by red-light runners and the like.

* If we take the value of a human life at somewhere between $8-10 million (https://www.transportation.gov/sites/dot.gov/files/docs/VSL_Guidance_2014.pdf), even several hundred more accidents at $5-10k a pop would be "worth" it.

Compare the 2014 traffic fatalities that occurred in Sterling Heights, MI and Carmel, IN.  Sterling Heights has a population of 130,410 and Carmel has a population of 85,927.  Both communities experienced 2 fatal crashes in 2014 (based on google searches and UD-10 forms).  Ironically, the two fatal crashes that occurred in Carmel happened inside roundabouts.  Neither fatality in Sterling Heights occurred at an intersection (according to the UD-10 forms).  Keep in mind, Sterling Heights has a population nearly 45k higher than Carmel.   I thought roundabouts reduce fatal crashes by 90%.  How then did Sterling Heights, a city full of traffic signals, have zero fatal intersection crashes while Carmel, a city full of roundabouts,  have 2 fatal roundabout crashes?

Fatal crashes in Carmel:
http://fox59.com/2014/08/06/one-dead-in-carmel-accident-passenger-taken-to-hospital/
http://fox59.com/2014/09/26/person-dead-after-motorcycle-accident-in-carmel/

Fatal crashes in Sterling Heights:
http://semcog.org/Data-and-Maps/Crash-and-Road-Data/Crash_Id/8939474/view/UD10CrashReport
http://semcog.org/Data-and-Maps/Crash-and-Road-Data/Crash_Id/8986238/view/UD10CrashReport

Because stats vary between cities? Aren't you a traffic engineer? Anomalies are perfectly common. This is obviously the 10% (though, keep reading...)

The whole point of this thread was to compile data for hundreds of roundabouts to prove a point that multi-lane roundabouts have more collisions. You have done a great job illustrating this, and I am definitely a believer at this point. There is no doubt that multi-lane roundabouts have more collisions (at this point, it's just a matter of whether or not that's a big deal).

You do lose me, however, when you attempt to prove that roundabouts are deadlier than signals by grabbing random data from two random cities, over random time frames. You're one step away from generalizing roundabouts as being deadlier than signals. And that's obviously nuts...right? It doesn't take a genius to figure out that roundabouts, just by the very nature of their design, are safer than signals (taking into account FARS data).

Intersections should be designed to minimize risk. Stats show that, in almost all cases, roundabouts may have more collisions, but are far safer for the driver. There are going to be isolated incidents of drivers not paying attention to the circle ahead, and lose control. It's just a fact. The place where roundabouts succeed is by reducing the potential for dangerous two-party collisions like you might see at signals. Drivers can lose control anywhere along a road (including at signals) and kill themselves. That shouldn't be a strike against the roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on November 05, 2015, 12:23:40 AM
The fundamental issue in this thread as I see it is that there is a wealth of scientific studies completed and in-process on the safety impacts of roundabouts, in the United States and elsewhere. I found dozens with a cursory Google Scholar search.

At this point I'd say either you need to do a systematic study of publishable caliber to demonstrate that the existing studies are wrong and that multilane roundabouts are really deathtraps, despite the accumulating mountain of evidence to the contrary produced by transportation research professionals around the world, or this thread has run its course.

And by "systematic study," I don't mean cherry-picked data from one year from a couple of cities. I mean a statistical analysis of a large volume of data, using a proper sample and appropriate control variables.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on November 05, 2015, 08:57:04 AM
The fundamental issue in this thread as I see it is that there is a wealth of scientific studies completed and in-process on the safety impacts of roundabouts, in the United States and elsewhere. I found dozens with a cursory Google Scholar search.

At this point I'd say either you need to do a systematic study of publishable caliber to demonstrate that the existing studies are wrong and that multilane roundabouts are really deathtraps, despite the accumulating mountain of evidence to the contrary produced by transportation research professionals around the world, or this thread has run its course.

And by "systematic study," I don't mean cherry-picked data from one year from a couple of cities. I mean a statistical analysis of a large volume of data, using a proper sample and appropriate control variables.

 :clap: :clap: :clap:
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on November 05, 2015, 09:06:43 AM
The fundamental issue in this thread as I see it is that there is a wealth of scientific studies completed and in-process on the safety impacts of roundabouts, in the United States and elsewhere. I found dozens with a cursory Google Scholar search.

At this point I'd say either you need to do a systematic study of publishable caliber to demonstrate that the existing studies are wrong and that multilane roundabouts are really deathtraps, despite the accumulating mountain of evidence to the contrary produced by transportation research professionals around the world, or this thread has run its course.

And by "systematic study," I don't mean cherry-picked data from one year from a couple of cities. I mean a statistical analysis of a large volume of data, using a proper sample and appropriate control variables.

I said nearly the same thing several pages/months ago. Interesting to see this thread still going in circles (pun intended).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 05, 2015, 10:44:40 AM
This thread has been focused on 2x2 multi-lane roundabouts.  These 2x2 roundabouts are the ones experiencing high crash rates.  Citing studies skewed towards single-lane and 2x1 multi-lane roundabouts don’t reveal the safety performance of 2x2 multi-lane roundabouts.  Find a study that focuses on the safety benefits of 2x2 multi-lane roundabouts and then we can talk.  Of course this point has already been made but some fail to recognize it:

The Insurance Institute for Highway Safety released a report in 2000 evaluating the safety of 24 intersections that were converted to roundabouts.  The report found the following:

Quote
The present study evaluated changes in motor vehicle crashes following conversion of 24 intersections from stop sign and traffic signal control to modern roundabouts. The settings, located in 8 states, were a mix of urban, suburban, and rural environments. A before-after study was conducted using the empirical Bayes approach, which accounts for regression to the mean. Overall, the empirical Bayes procedure estimated highly significant reductions of 39 percent for all crash severities combined and 76 percent for all injury crashes. Reductions in the numbers of fatal and incapacitating injury crashes were estimated to be about 90 percent.

http://safety.fhwa.dot.gov/intersection/resources/fhwasa09027/resources/Crash%20Reductions%20Following%20Installation%20of%20Roundabouts.pdf

The study was skewed towards evaluating single-lane roundabouts as only 9 of the 24 intersections evaluated were multi-lane roundabouts.  The 9 multi-lane roundabouts evaluated were all from Colorado and 6 of the 9 serviced interchanges along I-70.  The 3 non-interchange multi-lane roundabouts evaluated in the study were all along Avon Road in Avon, Colorado. When looking at aerials, there appears to be limited traffic generated along the side-street for 2 of the 3 roundabouts (IE. the side-street isn’t a major route).  Here is a list of all the roundabouts evaluated in the Insurance Institute study:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/2000study_zpsvmsggp6l.png)

In the press release for the proposed multi-lane roundabout at State & Ellsworth, the Washtenaw County Road Commission cited a study with familiar looking safety numbers:

Quote
As stated by a 2011 report from the Insurance Institute of Highway Safety, 23 intersections that were converted into roundabouts experienced significant declines in accidents. Total crash frequency fell by approximately 40 percent; injury crash frequency fell by approximately 80 percent; and fatal crash frequency fell by approximately 90 percent.

http://www.wcroads.org/node/529

Citing a study that is skewed towards single-lane roundabouts when a major multi-lane roundabout is being proposed seems disingenuous.  Even the multi-lane roundabouts evaluated in the 2000 study are dissimilar to the roundabout that was being proposed for State & Ellsworth.  In the first year of operation, State & Ellsworth experienced roughly a 10x increase in crashes (not a 40% reduction).  Agencies shouldn't be implying that large multi-lane roundabouts will see a reduction in total crashes (and by citing studies that are skewed towards single-lane roundabouts, that's exactly what they are doing).


Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on November 05, 2015, 01:12:22 PM
This thread has been focused on 2x2 multi-lane roundabouts.  These 2x2 roundabouts are the ones experiencing high crash rates.  Citing studies skewed towards single-lane and 2x1 multi-lane roundabouts don’t reveal the safety performance of 2x2 multi-lane roundabouts.  Find a study that focuses on the safety benefits of 2x2 multi-lane roundabouts and then we can talk.  Of course this point has already been made but some fail to recognize it:

No, the point is that the burden of proof that 2x2 multi-lane roundabouts are inherently unsafe is on you. You have not demonstrated this using evidence that would be accepted by the transportation research community, using a systematic study (not "I found another 2x2 roundabout with a few crashes").

Not to mention you keep moving the goalposts on this thread. First it was all modern roundabouts were deathtraps (which was demonstrated to be false). Then it was all multi-lane roundabouts are deathtraps, regardless of the lanes on each leg (ditto). Now it's all multi-lane roundabouts that have 2 or more lanes on each entering leg are deathtraps (where it's apparently "Carmel had 2 fatality accidents in roundabouts in 2014, so nyeh!").
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 05, 2015, 03:00:54 PM
No, the point is that the burden of proof that 2x2 multi-lane roundabouts are inherently unsafe is on you. You have not demonstrated this using evidence that would be accepted by the transportation research community, using a systematic study (not "I found another 2x2 roundabout with a few crashes").

Take a look at the 2x2 roundabouts that have been included in these published studies and see how they have performed.  A 2011 roundabout study funded by the Wisconsin Department of Transportation was cited previously on this thread.  Of the 24 roundabouts analyzed, there was only one 2x2 multi-lane roundabout (STH 32/ STH 57 Broadway in De Pere).   According to the study, 11 of the roundabouts had increases in crashes.  Here’s an excerpt from the study found on page 23:

Quote
Among the 11 locations with increased crash record, STH 32/STH 57 Broadway, Canal St/25th Ave, Thompson and Commercial, contribute 38 percent, 15 percent and 18 percent of all increases in the total number of crashes, respectively. All combined, the three locations contribute 71 percent of the crash increases.
http://www.topslab.wisc.edu/programs/safety/projects/roundabouts/WI%20Roundabout%20Evaluation%20Volume%202%20Safety.pdf

The 2x2 multi-lane roundabout analyzed in the Wisconsin study (Sth 32/STH 57 Broadway) accounted for 38% of the crash increases in the study.  Put another way, if this 2x2 roundabout hadn't been included in the study, the Wisconsin safety numbers would have looked a lot better.  Shortly after the release of the study, a circulating lane inside the 32/57 roundabout was removed.  They waved the white flag and converted it to a 2x1 roundabout to address the high crash rate.

Not to mention you keep moving the goalposts on this thread. First it was all modern roundabouts were deathtraps (which was demonstrated to be false). Then it was all multi-lane roundabouts are deathtraps, regardless of the lanes on each leg (ditto). Now it's all multi-lane roundabouts that have 2 or more lanes on each entering leg are deathtraps (where it's apparently "Carmel had 2 fatality accidents in roundabouts in 2014, so nyeh!").

Quote where i said this.  Fair enough? 
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on November 05, 2015, 04:22:44 PM
Quote
Among the 11 locations with increased crash record, STH 32/STH 57 Broadway, Canal St/25th Ave, Thompson and Commercial, contribute 38 percent, 15 percent and 18 percent of all increases in the total number of crashes, respectively. All combined, the three locations contribute 71 percent of the crash increases.
http://www.topslab.wisc.edu/programs/safety/projects/roundabouts/WI%20Roundabout%20Evaluation%20Volume%202%20Safety.pdf

The 2x2 multi-lane roundabout analyzed in the Wisconsin study (Sth 32/STH 57 Broadway) accounted for 38% of the crash increases in the study.  Put another way, if this 2x2 roundabout hadn't been included in the study, the Wisconsin safety numbers would have looked a lot better.  Shortly after the release of the study, a circulating lane inside the 32/57 roundabout was removed.  They waved the white flag and converted it to a 2x1 roundabout to address the high crash rate.

To be fair, it wasn't just the crash rate they were addressing. They were also addressing queuing and delays that developed counter to the pre-construction forecasts. It could also be said that the queuing had a part in the increase in crashes...the longer you're waiting, the more risks/smaller gaps you'll try and take.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 06, 2015, 12:31:47 AM
After two months of operation, a double-lane roundabout in Lakeville, Minnesota has tallied up 44 crashes.  Traffic counts at the roundabout are about 30,000 vehicles per day.  This equates to a crash rate of 24.1 MEV.  The crash rate should drop as drivers become more familiar with the roundabout - but even still - this is a horrible initial result.  It will be interesting to track the crashes over time at this roundabout. 

(http://sunthisweek.com/wp-content/uploads/sites/23/2015/08/image.jpg)
http://sunthisweek.com/2015/11/05/number-of-lakeville-roundabout-accidents-drop/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+Thisweeklivecom+%28ThisweekLive.com%29
Title: Re: Crash prone 'modern roundabouts'
Post by: Tom958 on November 06, 2015, 07:22:55 AM
...produced by transportation research professionals around the world...

That's what I want to know: is this questionable accident experience inherent to roundabouts in general, or is it an American thing? As I understand it, roundabouts were invented and first built in the UK, then spread to other places after their advantages had been proven through years of experience. They didn't make it over here until the third or fourth wave, at which point the accumulated evidence made it increasingly indefensible not to adopt them. If said evidence was a hoax (!), then we've got a concrete (and asphalt) problem. But if it's a matter of somehow inducing Americans to drive like other people... it's just a software issue.  :D

Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on November 06, 2015, 01:02:26 PM
New story regarding the Lakeville, MN roundabout: http://bringmethenews.com/2015/11/05/lakeville-drivers-are-starting-to-get-used-to-the-roundabout/ (http://bringmethenews.com/2015/11/05/lakeville-drivers-are-starting-to-get-used-to-the-roundabout/)

Quote
The newspaper says following its opening, there were 28 accidents on the roundabout in September, according to Lakeville Police Chief Jeff Long. However, this number dropped to 16 in October.

Quote
After it opened, the Minnesota Department of Transportation said most of the accidents occur on roundabouts because people don’t yield to other vehicles when they should. And that is still a problem in Lakeville, with local Steve Bakke telling the Sun he sees drivers sometimes accelerate rather than slow down as they approach the roundabout. Nonetheless, he admitted: “Every day it’s getting better.”

Quote
It is the first multi-lane roundabout to open in Dakota County
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 06, 2015, 02:43:23 PM
The newspaper says following its opening, there were 28 accidents on the roundabout in September, according to Lakeville Police Chief Jeff Long. However, this number dropped to 16 in October.
If the roundabout averages 16 crashes a month, that equates to 192 crashes per year.  It’s premature to write an article with the headline “drivers are starting to get use to the roundabout”  when the roundabout is on track to experience nearly 200 crashes in the first year of operation. 

After it opened, the Minnesota Department of Transportation said most of the accidents occur on roundabouts because people don’t yield to other vehicles when they should. And that is still a problem in Lakeville, with local Steve Bakke telling the Sun he sees drivers sometimes accelerate rather than slow down as they approach the roundabout. Nonetheless, he admitted: “Every day it’s getting better.”
Let’s hope it gets better every day.  It needs to get a lot better for multiple days.

It is the first multi-lane roundabout to open in Dakota County
That inaccurate.   There are several multi-lane roundabouts in Dakota County.  In fact, there is a multi-lane roundabout just two miles down the road from the new Lakeville roundabout.

https://www.google.com/maps/@44.6904743,-93.2376639,140m/data=!3m1!1e3
https://www.google.com/maps?ll=44.80465,-93.20761&z=18&t=h
https://www.google.com/maps/@44.8373943,-93.0853549,140m/data=!3m1!1e3
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on November 06, 2015, 03:09:18 PM
The newspaper says following its opening, there were 28 accidents on the roundabout in September, according to Lakeville Police Chief Jeff Long. However, this number dropped to 16 in October.
If the roundabout averages 16 crashes a month, that equates to 192 crashes per year.  It’s premature to write an article with the headline “drivers are starting to get use to the roundabout”  when the roundabout is on track to experience nearly 200 crashes in the first year of operation.

It's also premature to make yearly crash predictions based on two months of operation, especially when a decreasing trend is beginning to appear. Given the timeframe the article was referencing, their assumption is accurate.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 06, 2015, 03:26:55 PM
The newspaper says following its opening, there were 28 accidents on the roundabout in September, according to Lakeville Police Chief Jeff Long. However, this number dropped to 16 in October.
If the roundabout averages 16 crashes a month, that equates to 192 crashes per year.  It’s premature to write an article with the headline “drivers are starting to get use to the roundabout”  when the roundabout is on track to experience nearly 200 crashes in the first year of operation.

It's also premature to make yearly crash predictions based on two months of operation, especially when a decreasing trend is beginning to appear. Given the timeframe the article was referencing, their assumption is accurate.

Let's just wait to see if monthly crashes drop to 2 per month at this roundabout.  Even then, the roundabout would have a crash rate above 2.0 MEV. 
Title: Re: Crash prone 'modern roundabouts'
Post by: Tom958 on November 07, 2015, 10:45:39 AM
...produced by transportation research professionals around the world...

That's what I want to know: is this questionable accident experience inherent to roundabouts in general, or is it an American thing?

I found this study (https://www.scribd.com/doc/174870895/ITE-A-Comparative-Evaluation-of-the-Safety-Performance-of-Roundabouts-and-Traditional-Intersection-Controls), which compares intersections in the city of Las Vegas, and which breaks the results down by ADT into minor, medium and major intersections. In the major intersections category there are three roundabouts and three signalized intersections, with ADT ranging from 21k to 28k (which really isn't that much, is it?). It says, among other things:

"However, the roundabouts that fall into the major intersections category have more crashes than the signalized intersections. Even though the total number of crashes was more for the roundabouts, the number of injury crashes was in the same range for both roundabouts and intersections with traditional controls."

And, later in the report:

"A higher number of crashes at the roundabouts creates an impression that the signalized intersections are safer compared to roundabouts at the candidate major intersections. This contradicts the findings from Europe that the roundabouts are safer than the signals even when the daily traffic entering the roundabouts is high.." (my italics)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 08, 2015, 11:59:26 AM
Thanks for the link to that Las Vegas study Tom.  Of the 3 roundabouts classified as major, only Town Center Dr. and Hualapai Way would be considered a 2x2 multi-lane roundabout.  Interestingly, this 2x2 roundabout had the worst crash rate and the worst injury crash rate of any intersection analyzed in the study (excluding stop-controlled intersections):

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/roundaboutsafetyuntitled_zpsjwq2w2rt.png)

This published study further questions the safety benefits of 2x2 multi-lane roundabouts.  There were significantly more crashes at the Town Center Dr and Hualapai Way roundabout with no reductions in injury crashes when compared to similar ADT signalized intersections in Las Vegas.  To put things into perspective, there were nearly as many injury crashes at the Town Center / Hualapai Way roundabout than total crashes at the Tenaya St / Vegas Dr. signalized intersection (3 injury crashes vs. 4.6 total crashes). 
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on November 08, 2015, 06:18:50 PM
Pretty funny when tradeph is very quick to note a high volume of accidents within a few weeks of a roundabout's opening and details how unsafe they are, but very quick to dispute someone's report of a reduction in accidents, noting that more time is needed to see the big picture.

Btw, you are still cherry-picking data.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 08, 2015, 06:55:45 PM
Pretty funny when tradeph is very quick to note a high volume of accidents within a few weeks of a roundabout's opening and details how unsafe they are, but very quick to dispute someone's report of a reduction in accidents, noting that more time is needed to see the big picture.

Btw, you are still cherry-picking data.

If I’m cherry picking data, then there must be plenty of 2x2 modern roundabouts that have low crash rates.  Cite these 2x2 roundabouts with low crash rates or your accusation rings hollow.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 09, 2015, 05:20:15 PM
This would be an eye opening study if it were published:

“The Safety Performance of Roundabouts with Average Daily Traffic exceeding 30,000”


The 30,000 ADT condition would weed out single-lane roundabouts and most 2x1 multi-lane roundabouts.  The focus would be nearly entirely on the safety performance of 2x2 (or higher) roundabouts in America. Ideally, the study would analyze interchange and non-interchange roundabouts separately and come up with two different sets of safety numbers.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 10, 2015, 05:03:04 PM
According to a 2014 article, the OPP have responded to 52 collisions at the Herb Gray Parkway multi-lane roundabout in Windsor, Ontario.  All the accidents were referred to as “minor accidents” .  Does this mean only minor injury accidents occurred or no injury accidents occurred at all?  The article doesn’t clarify. 
http://blackburnnews.com/chatham/chatham-news/2014/12/22/two-lane-roundabout-yields-accidents/

In addition, in April 2015 there were two separate tractor trailer rollovers inside the roundabout about a week apart. 
http://www.cbc.ca/news/canada/windsor/all-lanes-open-after-another-roundabout-rollover-at-highway-3-1.3043578


Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 14, 2015, 11:03:46 AM
The overall crash rate benefits may be "null and void," but these high volume intersections that require a multilane solution are the ones that lead to the vast majority of fatality crashes when they're signalized or have multi-way stop conditions. Without getting into the weeds of cost-benefit analysis,* a few more (or even many more) fender benders and whiplash accidents are massively preferable to a few more deaths from people being T-boned by red-light runners and the like.

* If we take the value of a human life at somewhere between $8-10 million (https://www.transportation.gov/sites/dot.gov/files/docs/VSL_Guidance_2014.pdf), even several hundred more accidents at $5-10k a pop would be "worth" it.

In a recent study, MDOT evaluated the performance and safety effectiveness of roundabouts in Michigan.  According to the cost-benefit crash analysis included in the study, triple-lane roundabouts saw a negative average benefit of -$122,778 annually.  The double-lane roundabout at 68th Ave & Randall St was the only 2x2 roundabout analyzed in the study; it too had a negative benefit.   

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/MDOTrb_zpsfygteugy.png)
https://www.michigan.gov/documents/mdot/MDOT_Research_Report_RC1566_379286_7.pdf

The safety improvements of roundabouts are mitigated as you get into high capacity double-lane (specifically 2x2) and triple-lane roundabouts.  The triple-lane roundabouts analyzed in the Michigan study saw a 19.9% reduction in injury crashes while total crashes increased by 97.5%.  The reduction in injury crashes wasn’t enough to offset the large increases in total crashes in the cost-benefit analysis.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 16, 2015, 10:16:58 AM
Here's a link to a presentation given by the FHWA at the 4th Annual International Conference on Roundabouts.  It is titled "The Mutli-Lane Roundabout  PDO Dilemma" and summarizes a lot of the points made on this thread. 

http://teachamerica.com/RAB14/RAB1410AIsebrands/index.htm

A few comments...
In the first slide, the speaker states that "they [multi-lane roundabouts] are showing great improvement in terms of the injury and fatal crashes".  However, she doesn't cite any evidence to support this and it's up to the listener to take her claim at face value. 

The Bluffton, SC roundabout is highlighted in this presentation and favorable crash statistics are shown.  However, the presenter questions whether crashes will go back up as drivers get use to the new markings.  In 2014, the roundabout experienced 30 total crashes including 7 injury crashes.  This equates to 2.5 crashes per month (much higher than the 0.4/month cited in the presentation).  Unfortunately, crashes have gone back up.

http://www.islandpacket.com/news/local/traffic/article33716778.html
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 21, 2015, 09:19:39 AM
This roundabout is going to be a doozy (scheduled for 2017):
(http://www.gannett-cdn.com/-mm-/5535823b363befef22d5776f449f2b0cc382d3de/c=21-0-513-655&r=537&c=0-0-534-712/local/-/media/Appleton/2014/07/24/-roundabout.jpg20140723.jpg)
http://www.postcrescent.com/story/news/local/2014/07/24/roundabout-coming-richmond-northland/13119107/

Is there any evidence that triple-lane roundabouts have reduced injury crashes in Wisconsin?
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on December 22, 2015, 11:54:32 AM
Alright...triple-laners make me twitch.  I'll agree with your concern here, tradey.
Title: Re: Crash prone 'modern roundabouts'
Post by: AlexandriaVA on December 22, 2015, 12:18:10 PM
Egads. That's no roundabout. That's a corn-fed abomination!
Title: Re: Crash prone 'modern roundabouts'
Post by: cl94 on December 22, 2015, 02:36:10 PM
Alright...triple-laners make me twitch.  I'll agree with your concern here, tradey.

Um...yeah. There are very few places where a triple-lane roundabout makes sense. Basically only where it replaces a triple-lane traffic circle.
Title: Re: Crash prone 'modern roundabouts'
Post by: Zeffy on December 22, 2015, 06:23:21 PM
Two lanes should be the maximum for any circular intersection. Three lanes is just too much.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 22, 2015, 06:29:50 PM
Alright...triple-laners make me twitch.  I'll agree with your concern here, tradey.

Um...yeah. There are very few places where a triple-lane roundabout makes sense. Basically only where it replaces a triple-lane traffic circle.
Two lanes should be the maximum for any circular intersection. Three lanes is just too much.

I can see triple-lane roundabouts at heavily-used junctions, but only as an upgrade from a two-lane roundabout. (I think the roundabout above (on the last page) will work function well as a traffic control device first, as a safety net second, but I think the roundabout would be better off as two lanes until traffic demands the third).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 22, 2016, 05:55:41 PM
Route 62 and Morse Road roundabout in Gahanna, Ohio had the second most crashes in the mid-Ohio region from 2009 to 2011 (98 total crashes).   It also had the 5th highest number of injury crashes.  To combat this poor safety record, a circulating lane was removed and crashes have since gone down (a common theme in this thread).  They can always restripe it to a 2x2 roundabout if traffic conditions warrant it, but it should have been striped as a 2x1 roundabout to begin with.

http://www.morpc.org/trans/Safety_Top_intersections.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: Jovet on January 23, 2016, 02:00:17 AM
I said it before, I do not like multi-lane roundabouts. They are just too complicated, and can confuse drivers. 
I agree.  I think they're just inviting trouble!

Same for multi-lane four-way stops. Those drive me UP THE WALL!
Title: Re: Crash prone 'modern roundabouts'
Post by: Quillz on January 23, 2016, 11:53:09 PM
So, during my research, I came across this proposed roundabout design for the UK:

(http://i.imgur.com/mCg3nlw.png)

I mentioned this design in another thread. The idea is that it allows a motorist to get to their desired direction (left, straight, or right) without having to change any lanes, as each quarter-turn automatically shuffles off the proper lane. For usage in America, the turning would be reversed.
Title: Re: Crash prone 'modern roundabouts'
Post by: cl94 on January 24, 2016, 12:10:55 AM
So, during my research, I came across this proposed roundabout design for the UK:

(http://i.imgur.com/mCg3nlw.png)

I mentioned this design in another thread. The idea is that it allows a motorist to get to their desired direction (left, straight, or right) without having to change any lanes, as each quarter-turn automatically shuffles off the proper lane. For usage in America, the turning would be reversed.

That's roughly the design specified in the MUTCD. The Dutch call it a "turbo roundabout".
Title: Re: Crash prone 'modern roundabouts'
Post by: Quillz on January 24, 2016, 12:12:49 AM
So, during my research, I came across this proposed roundabout design for the UK:

(http://i.imgur.com/mCg3nlw.png)

I mentioned this design in another thread. The idea is that it allows a motorist to get to their desired direction (left, straight, or right) without having to change any lanes, as each quarter-turn automatically shuffles off the proper lane. For usage in America, the turning would be reversed.

That's roughly the design specified in the MUTCD. The Dutch call it a "turbo roundabout".
Interesting to see it's in the MUTCD. I've never driven on one, but it seems to make a great deal of sense, especially since one of the biggest issues with roundabouts is people attempting to lane change. This design would seemingly solve that problem. Of course, most of the roundabouts I've been on are single-lane to begin with, making this design unnecessary.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 24, 2016, 12:36:50 AM
So, during my research, I came across this proposed roundabout design for the UK:

http://i.imgur.com/mCg3nlw.png

I mentioned this design in another thread. The idea is that it allows a motorist to get to their desired direction (left, straight, or right) without having to change any lanes, as each quarter-turn automatically shuffles off the proper lane. For usage in America, the turning would be reversed.

That's roughly the design specified in the MUTCD. The Dutch call it a "turbo roundabout".

Interesting to see it's in the MUTCD. I've never driven on one, but it seems to make a great deal of sense, especially since one of the biggest issues with roundabouts is people attempting to lane change. This design would seemingly solve that problem. Of course, most of the roundabouts I've been on are single-lane to begin with, making this design unnecessary.

Are you sure you've never driven on a turbo roundabout (or at least the American interpretation)? If you come to one, there's a very good chance it has spiral markings.

In my area, the first multi-lane roundabouts were striped with spiral markings. They were built in the early 2000s.
Title: Re: Crash prone 'modern roundabouts'
Post by: Quillz on January 24, 2016, 12:39:45 AM
I don't believe I've been on one. Every roundabout I've driven one had effectively an off-ramp, if you will, that didn't force you to take it if you didn't want to. But it was single-lane, so it couldn't do that.
Title: Re: Crash prone 'modern roundabouts'
Post by: roadfro on January 24, 2016, 01:20:06 AM
So, during my research, I came across this proposed roundabout design for the UK:

(http://i.imgur.com/mCg3nlw.png)

I mentioned this design in another thread. The idea is that it allows a motorist to get to their desired direction (left, straight, or right) without having to change any lanes, as each quarter-turn automatically shuffles off the proper lane. For usage in America, the turning would be reversed.

That's roughly the design specified in the MUTCD. The Dutch call it a "turbo roundabout".

Note that the MUTCD does not "specify" any roundabout designs, or govern any roadway designs in general. The MUTCD only regulates the signs, striping, etc. used in roadway design.

A "turbo roundabout" is two of several roundabout pavement marking examples depicted in the MUTCD. (Figure 3C-5 is a two-lane roundabout with one-lane exits; Figure 3C-12 is a three-lane roundabout with two-lane exits. Other examples show partial turbos for unique situations.)
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on January 24, 2016, 05:09:38 AM
So, during my research, I came across this proposed roundabout design for the UK:

(http://i.imgur.com/mCg3nlw.png)
Spiral roundabouts like that are, in the UK, only used when the conflict points are fully signalised.

This is the most blatent one https://www.google.co.uk/maps/@53.5498467,-2.260033,347m/data=!3m1!1e3 with certain routes colour-coded on the pavement.
Title: Re: Crash prone 'modern roundabouts'
Post by: Kacie Jane on January 24, 2016, 01:21:38 PM
So, during my research, I came across this proposed roundabout design for the UK:

http://i.imgur.com/mCg3nlw.png

I mentioned this design in another thread. The idea is that it allows a motorist to get to their desired direction (left, straight, or right) without having to change any lanes, as each quarter-turn automatically shuffles off the proper lane. For usage in America, the turning would be reversed.

That's roughly the design specified in the MUTCD. The Dutch call it a "turbo roundabout".

Interesting to see it's in the MUTCD. I've never driven on one, but it seems to make a great deal of sense, especially since one of the biggest issues with roundabouts is people attempting to lane change. This design would seemingly solve that problem. Of course, most of the roundabouts I've been on are single-lane to begin with, making this design unnecessary.

Are you sure you've never driven on a turbo roundabout (or at least the American interpretation)? If you come to one, there's a very good chance it has spiral markings.

In my area, the first multi-lane roundabouts were striped with spiral markings. They were built in the early 2000s.

Note that in the drawing, there are three lanes entering at each approach, one for each direction.  Every roundabout I've come across around Puget Sound has at least straight and right-turning traffic approach in the same lane.

Now that I've written that second sentence, I'm not 100% confident in its accuracy.  There may in fact be some where right turning traffic is alone and straight through traffic is paired with left turning traffic instead.  But that's not the important part.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 24, 2016, 03:16:28 PM
So, during my research, I came across this proposed roundabout design for the UK:

http://i.imgur.com/mCg3nlw.png

I mentioned this design in another thread. The idea is that it allows a motorist to get to their desired direction (left, straight, or right) without having to change any lanes, as each quarter-turn automatically shuffles off the proper lane. For usage in America, the turning would be reversed.

That's roughly the design specified in the MUTCD. The Dutch call it a "turbo roundabout".

Interesting to see it's in the MUTCD. I've never driven on one, but it seems to make a great deal of sense, especially since one of the biggest issues with roundabouts is people attempting to lane change. This design would seemingly solve that problem. Of course, most of the roundabouts I've been on are single-lane to begin with, making this design unnecessary.

Are you sure you've never driven on a turbo roundabout (or at least the American interpretation)? If you come to one, there's a very good chance it has spiral markings.

In my area, the first multi-lane roundabouts were striped with spiral markings. They were built in the early 2000s.

Note that in the drawing, there are three lanes entering at each approach, one for each direction.  Every roundabout I've come across around Puget Sound has at least straight and right-turning traffic approach in the same lane.

Sorry, I wasn't being specific enough. My point was that it boggled my mind that Quillz has never seen a multi-lane roundabout with spiral markings, since our first roundabouts have had spiral markings for 10 or 11 years now (although, the markings have changed over the years to become slightly less ambiguous).
Title: Re: Crash prone 'modern roundabouts'
Post by: Quillz on January 25, 2016, 12:05:24 PM
I don't know what is so mind boggling. The only roundabouts I've ever personally driven on have been single laned.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 25, 2016, 12:29:19 PM
Here’s a recent article by mlive spinning the safety performance of the State and Ellsworth roundabout.  The writer of the article just can’t admit that this roundabout has been a failure from a safety perspective:

Quote
There are some instances of total crash rates increasing after the addition of a roundabout. A good example of this is the State Street and Ellsworth Road intersection, but even in those cases, the numbers of serious injury and fatal crashes have dropped sharply. At the State and Ellsworth intersection, there were 97 crashes between 2008 and 2012 and 12 of them–12 percent–were injury crashes. In 2014 alone there were 171 crashes, but just 6–3.5 percent–involved injuries.
http://www.mlive.com/news/ann-arbor/index.ssf/2016/01/roundabouts_spreading_as_count.html

Before the roundabout the signalized intersection averaged 2.4 injury crashes per year (12 injury crashes / 5 years of data).  After the roundabout, it has averaged 6 injury crashes per year (6 injury crashes / 1 year of data).   Based on the facts presented in the article, the roundabout has seen a significant increase in injury crashes, not a decrease.   
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on January 25, 2016, 12:41:39 PM
I don't know what is so mind boggling. The only roundabouts I've ever personally driven on have been single laned.

Then try driving a 2 or 3 lane roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: PurdueBill on January 25, 2016, 01:23:05 PM
Here’s a recent article by mlive spinning the safety performance of the State and Ellsworth roundabout.  The writer of the article just can’t admit that this roundabout has been a failure from a safety perspective:

Quote
There are some instances of total crash rates increasing after the addition of a roundabout. A good example of this is the State Street and Ellsworth Road intersection, but even in those cases, the numbers of serious injury and fatal crashes have dropped sharply. At the State and Ellsworth intersection, there were 97 crashes between 2008 and 2012 and 12 of them–12 percent–were injury crashes. In 2014 alone there were 171 crashes, but just 6–3.5 percent–involved injuries.
http://www.mlive.com/news/ann-arbor/index.ssf/2016/01/roundabouts_spreading_as_count.html

Before the roundabout the signalized intersection averaged 2.4 injury crashes per year (12 injury crashes / 5 years of data).  After the roundabout, it has averaged 6 injury crashes per year (6 injury crashes / 1 year of data).   Based on the facts presented in the article, the roundabout has seen a significant increase in injury crashes, not a decrease.   

So this particular intersection went from having a crash every 2-3 weeks in 2008-12 to having one every other day and they are calling that progress?  How can the writer of that article write what they did with a straight face?  Sure the percent of injury crashes is lower...the number of total accidents per year is up 780 percent!!  The crash numbers seem to indicate that something is very wrong with that roundabout, not very right as they paint it.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on January 25, 2016, 02:33:34 PM
I see lane confusion happening in the posted roundabout design.  Take the top quarter where lane 3 of the roundabout goes left and then you're left with lanes 4 and 1 that split into three lanes.  Which lane do I go in?  Looks like a recipe for disaster.
Title: Re: Crash prone 'modern roundabouts'
Post by: Quillz on January 25, 2016, 02:38:31 PM
I don't know what is so mind boggling. The only roundabouts I've ever personally driven on have been single laned.

Then try driving a 2 or 3 lane roundabout.
If there were any around here, I probably would. Most of the roundabouts in California right now are either built by Caltrans at state highways junctions with high traffic incidents, or locally built and maintained by neighborhoods. Neither of those are close to me, the closest on for me would be the CA-154/CA-246 junction near Solvang, which consists of a single lane that lets you stay on CA-154, turn west onto CA-246, or east onto a local road.
Title: Re: Crash prone 'modern roundabouts'
Post by: roadfro on January 27, 2016, 10:17:00 AM
I see lane confusion happening in the posted roundabout design.  Take the top quarter where lane 3 of the roundabout goes left and then you're left with lanes 4 and 1 that split into three lanes.  Which lane do I go in?  Looks like a recipe for disaster.

You stay in your same lane, the one directly ahead of you. You're not supposed to change lanes in a roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 04, 2016, 02:36:40 PM
The Homer Watson roundabout saw over 100 crashes in 2014.  Add it to the 100+ roundabout crash club.  The crash problem at this roundabout has gotten worse each year since its construction in 2011.

Quote
Homer Watson roundabout remains a trouble spot
...the roundabout was installed in 2011. That year there were 51 collisions. The number grew to 53 in 2012, 72 in 2013 and 107 in 2014.  Bob Henderson, manager of transportation engineering, presented the 2014 collision report for regional roads at a meeting Tuesday.  He said the problem at the roundabout is human behaviour, according to a review completed earlier this year. Traffic volume has also increased.  "The design's good at the intersection," he said.

http://m.kitchenerpost.ca/news-story/6122856-regional-road-collision-report-homer-watson-roundabout-remains-a-trouble-spot

Title: Re: Crash prone 'modern roundabouts'
Post by: Brian556 on March 04, 2016, 11:26:58 PM
Quote
Same for multi-lane four-way stops. Those drive me UP THE WALL!

Never thought of it like this but good point.

Multi-lane all way stops create issues if they are on a heavily traveled roadway cause if you are in the right lane, and another vehicle is in the left lane, that vehicle blocks your view and you can't see if anybody is in the oncoming left turn lane that you need to wait for.

Dixon Ln in Flower Mound Texas is like that. Three all-way stops in a row on a four lane divided street. One intersection needs signals, the others need two way stops. Vehicles often back up to 8 deep at the first all way stop because the previous intersection is signalized. In this case the first all way stop is at a busy high school driveway, and the other two are at residential street intersections that do not need them.

This situation is utterly ridiculous. It's weird cause the town of Flower Mound is very good at sign and signal maintenance, but shitty at engineering and application of traffic control.

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 07, 2016, 11:22:08 AM
The woman being interviewed in that video works at the Tim Hortons next to the roundabout.  According to her, everyday there is “some type of fender bender, some type of accident” .  You can look at the numbers and say there were only 107 crashes in 2014… she must be exaggerating.  But really, a lot of the crashes that occur at a roundabout don’t get reported because many of them are minor fender benders.  It's the roundabout crashes that result in significant vehicle damage where the cops are more likely to get called out. 

It would be interesting to compare the reported vs. non-reported crashes at roundabouts vs. signalized intersections.  At the State & Ellsworth roundabout in Ann Arbor there were over 170 crashes in a year.  But how many accidents involving broken tail-lights and cracked bumpers didn’t get reported?   I wouldn't be at all surprised if that Ann Arbor roundabout averages a crash a day (be it reported or unreported). 
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on March 07, 2016, 12:09:42 PM
The woman being interviewed in that video works at the Tim Hortons next to the roundabout.  According to her, everyday there is “some type of fender bender, some type of accident”.  You can look at the numbers and say there were only 107 crashes in 2014… she must be exaggerating.  But really, a lot of the crashes that occur at a roundabout don’t get reported because many of them are minor fender benders.  It's the roundabout crashes that result in significant vehicle damage where the cops are more likely to get called out. 

It would be interesting to compare the reported vs. non-reported crashes at roundabouts vs. signalized intersections.  At the State & Ellsworth roundabout in Ann Arbor there were over 170 crashes in a year.  But how many accidents involving broken tail-lights and cracked bumpers didn’t get reported?   I wouldn't be at all surprised if that Ann Arbor roundabout averages a crash a day (be it reported or unreported). 


No doubt the same type bumps occur at regular intersections as well.  Accidents usually leave broken parts behind, so I'm sure there would be a lot of plastic lying around the roundabout if there were accidents everyday.

If there's significant damage, they're supposed to be reported to the police anyway, even after the fact.  I would think most insurance companies would want such a police report.  Thus, I'm sure some of the 107 accidents at the intersection include some where the police didn't actually respond to it.

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 07, 2016, 01:29:32 PM
Is the percentage of unreported crashes higher at roundabouts or higher at signalized intersections?  That’s the question I’m interested in.  The only way to figure that out is to actually record them and cross reference the crashes that were observed in the video to the police reports that were filed.  It’s not scientific enough to say “well, I don’t see any plastic pieces laying around the roundabout today… I guess there’s not a crash problem” . 

A lot of people won’t report a fender bender because they don’t want their insurance to go up.  Sure, a $120,000 dollar Maserati gets rear-ended and the cops will probably be called.   But for every Maserati there are thousands of Chevy Malibu’s on the road.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 08, 2016, 12:11:59 PM
It’s not just total crashes that are a problem at the Homer Watson roundabout.  According to the record, injuries have more than doubled since the roundabout opened in 2011.  This is another example of a large multi-lane roundabout seeing a spike in total crashes with no reduction in injury crashes (a lose-lose).   The argument has been that crashes that occur at a roundabout are low impact “fender benders” .  If that is true, how did 40 people get injured at the Homer Watson roundabout in just the first 3 years of operation?   

Quote
Its safety performance is not as poor as the dangerous roundabout it overtook, Homer Watson Boulevard at Block Line Road. After opening in 2011, the Kitchener intersection saw its collisions soar to 282 from 44, while injuries more than doubled to 40 people hurt from 16 hurt. This compares its first three-plus years as a roundabout to its last three-plus years as a traffic light. The second-busiest roundabout shed seven per cent of its traffic in 2014 to fall to second place.

http://m.therecord.com/news-story/6218115-86-crashes-in-first-17-months-collisions-soar-at-new-cambridge-roundabout
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 08, 2016, 07:30:09 PM

I think they're a bit too close to each other.  I also went during rush hour.

I'd rather have two closely spaced roundabouts than two closely spaced signals. Then again, they don't seem that close?

These work just fine. A bit slow at rush hour but compared to the old signals it's a big improvement.

(http://images.tapatalk-cdn.com/15/05/20/434e6b90f4e62f7968f4416834fa3ba0.jpg)

These two roundabouts in Hilliard were the #1 & #3 most crash prone intersections in the entire state of Ohio for the years 2013-2015.  There were 218 crashes at the Cemetery/Main roundabout and 119 crashes at the Main/Scioto Darby roundabout.  Hell, even the Google streetview car captured a crash at the roundabout:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/untitledtest2_zpsincgcpjj.png)

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Ohiotop10_zps3csyc94q.png)

http://branlawfirm.com/most-dangerous-intersections-in-ohio/
Title: Re: Crash prone 'modern roundabouts'
Post by: johndoe on March 08, 2016, 07:53:48 PM
https://www.google.com/maps/@43.4183801,-80.470737,110m/data=!3m1!1e3 (https://www.google.com/maps/@43.4183801,-80.470737,110m/data=!3m1!1e3)

The Homer Watson roundabout appears to have an ICD of about 200', so it's not undersized.  Do you see any patterns in the crash reports?  You can see they striped out the third circulating lane for the SB approach, I wonder if crashes were reduced after they made that change.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on March 08, 2016, 08:36:01 PM
It’s not just total crashes that are a problem at the Homer Watson roundabout.  According to the record, injuries have more than doubled since the roundabout opened in 2011.  This is another example of a large multi-lane roundabout seeing a spike in total crashes with no reduction in injury crashes (a lose-lose).   The argument has been that crashes that occur at a roundabout are low impact “fender benders” .  If that is true, how did 40 people get injured at the Homer Watson roundabout in just the first 3 years of operation?

What constitutes an injury? Technically, both breaking your neck and straining your neck are injuries. A t-bone collision could result in several broken bones, but no deaths, and would be labelled an "injury collision". Equally, being rear-ended and bumping your head on the steering wheel is also an "injury collision" (presuming one sought medical attention, reporting the injury to insurance).

As we've previously discussed, there are multiple levels of injuries. Injuries may have increased, but it's the severity that matters. It's ridiculous to support an intersection design that (perhaps) puts people in hospital for months, but oppose an intersection design that results in several visits to a chiropractor, simply because there's fewer injuries overall.

If one were to put a price tag on "emotional distress" caused by collisions (as many lawyers do, in order to offset the loss of income from being in hospital), my guess is that 6 or 7 really bad injury crashes is still much pricier than 40 or 50 head-bumps and neck-strains.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 09, 2016, 08:40:54 AM
The Homer Watson roundabout appears to have an ICD of about 200', so it's not undersized.  Do you see any patterns in the crash reports?  You can see they striped out the third circulating lane for the SB approach, I wonder if crashes were reduced after they made that change.

To be honest I’m not sure when the third lane was striped out at the Homer Watson roundabout.  Here’s a youtube video posted April 2013 where the SB approach was still 3-lanes. 

In my opinion this is a properly sized roundabout.  It is large enough where there is separation between legs of traffic yet small enough where drivers aren’t circulating around at high speeds.  Yet there were 40 injuries in the first 3 years of operations.  One thing you notice in the video is that a pedestrian crossing the roundabout can lead to ”˜gridlock’.  Perhaps the large number of crashes and injuries can be attributed to the high pedestrian volumes at this roundabout.  This is just a guess though since I haven’t gone through the crash reports.  Before this roundabout was built, residents voiced concerns that a busy roundabout shouldn’t be constructed next to a high school with heavy pedestrian traffic.    In October 20011, shortly after the roundabout opened, a 16-year old St. Mary’s High School student was struck by a bus while she was walking in the crosswalk.   She experienced significant injuries.  In the news reports you could see the indentation her head made with the buses windshield.   This accident placed a negative light on the roundabout in the community and the city has been trying to make the roundabout safer ever since (ie. reducing a circulating lane at one of the legs, placing stopping guards during school times, etc).
   
As we've previously discussed, there are multiple levels of injuries. Injuries may have increased, but it's the severity that matters. It's ridiculous to support an intersection design that (perhaps) puts people in hospital for months, but oppose an intersection design that results in several visits to a chiropractor, simply because there's fewer injuries overall.

Roundabouts can be the site of serious, life altering accidents.  Just ask Cassi Lam who was the 16-year old girl struck at the Homer Watson roundabout.  The article I cited touches on another roundabout in the Waterloo region.  The roundabout at Hespeler Road and Queen Street “…went from 15 total collisions that hurt nine people to 86 total collisions that hurt six people. This compares its last 17 months as a traffic light to its first 17 months as a roundabout. The average severity of injury did not change and the roundabout had one more injury-causing collision than the traffic signal, although fewer people were hurt.”  
Title: Re: Crash prone 'modern roundabouts'
Post by: PurdueBill on March 09, 2016, 08:38:38 PM
Things like the above are what has me wondering about the wisdom of the push for a roundabout at State Street and River Road (former IN 26 and US 231) in West Lafayette.  The push is to make State Street so much more pedestrian and bike friendly, increasing foot traffic from Chauncey Hill down to the Levee, but through a roundabout? With tipsy students heading to and from bars at night? Between multilane streets that carry significant commuter traffic to and from campus from and to Lafayette? Seems like asking for trouble.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 10, 2016, 12:54:57 PM
It sounds like they are axing their plans to build a roundabout at State Street and River Road.   The roundabout footprint would encroach onto private property making it cost prohibitive.  Even if it wasn’t cost prohibitive they shouldn’t build it because it’s just not the right location for a roundabout (for the reasons mentioned by PurdueBill).

http://www.purdueexponent.org/city/article_e57dcfac-825e-5df8-9ae8-08b2c8a4f343.html#comments

Title: Re: Crash prone 'modern roundabouts'
Post by: PurdueBill on March 10, 2016, 01:15:16 PM
It sounds like they are axing their plans to build a roundabout at State Street and River Road.   The roundabout footprint would encroach onto private property making it cost prohibitive.  Even if it wasn’t cost prohibitive they shouldn’t build it because it’s just not the right location for a roundabout (for the reasons mentioned by PurdueBill).

http://www.purdueexponent.org/city/article_e57dcfac-825e-5df8-9ae8-08b2c8a4f343.html#comments



That hopefully will stick.  Can you imagine asking McDonald's to close again after the old one was shut down and demolished for the River Road work that rerouted US 231?  There is too much pedestrian and bicycle traffic for the roundabout to work there.  It seems that West Lafayette has been going kinda wild with stuff on roads that INDOT left to them; the signals at Northwestern and Stadium were in fine working order and not that old but needed to be replaced because they weren't pretty enough--same for Northwestern and Grant.  The roundabouts at Northwestern and Yeager and at new and old SR 25 have their issues without adding pedestrians and bicycles to the mix in large quantity.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on March 10, 2016, 04:03:15 PM
Why not signalize the pedestrian crossings at roundabouts? Some sort of pole-mounted HAWK setup might work well.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 11, 2016, 01:42:39 PM

The non-compliance rate at the HAWK is high especially for drivers exiting the roundabout.   A driver exiting the roundabout may not see that the HAWK signal is activated in time or they may be worried about being rear ended if they come to a stop so close to the roundabout exit.  And a lot of the drivers that do come to a stop are stopping for too long.  They treat the alternating flashing red signals like a railroad crossing (wait until the lights stop flashing).  This just leads to more gridlock and drivers backing up through the roundabout.  I find it curious that the HAWK video only demonstrates pedestrians crossing the entry leg of the roundabout.  Why not show what it looks like crossing the exit leg?  That’s when you see drivers backing up through the roundabout and causing gridlock.

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on March 11, 2016, 02:44:21 PM
The non-compliance rate at the HAWK is high especially for drivers exiting the roundabout.

How high is the compliance rate for a normal crosswalk? We're discussing the lesser of two evils here.

A driver exiting the roundabout may not see that the HAWK signal is activated in time or they may be worried about being rear ended if they come to a stop so close to the roundabout exit.  And a lot of the drivers that do come to a stop are stopping for too long.  They treat the alternating flashing red signals like a railroad crossing (wait until the lights stop flashing).  This just leads to more gridlock and drivers backing up through the roundabout.  I find it curious that the HAWK video only demonstrates pedestrians crossing the entry leg of the roundabout.  Why not show what it looks like crossing the exit leg?  That’s when you see drivers backing up through the roundabout and causing gridlock.

All of those things could be said about a normal crosswalk at a roundabout (backing up through the circle, not stopping because of a fear of being rear-ended, etc). I'm simply saying that, legally, crosswalks have to be provided somewhere at every intersection (or at least I'm pretty sure they are) The HAWK may have compliance issues now, but in several years, as drivers come to understand their meaning, I suspect that they'll provide a superior crossing option for roundabouts, especially those with two or more lanes. They force drivers to stop for 8-10 seconds to let pedestrians cross, and then go to a flash mode so drivers can continue, should there not be any more pedestrians.

Pedestrian safety at roundabouts seem to be related to drivers stopping right at the crosswalk, making the pedestrian invisible to subsequent lanes. The pedestrian assumes right-of-way because one car stopped, but the car in the next lane cannot see the pedestrian, and the two collide. HAWK signals force traffic to stop farther back, so visibility isn't hindered as much.

There's also an operational advantage. Rather than having traffic stop every 10-15 seconds to let one person cross, traffic stops every 60-80 seconds to let three or four people cross. Perhaps the parallel leg could also be timed so that the pedestrians can cross both the ingress and egress leg of the roundabout at the same time.
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on March 12, 2016, 04:16:03 AM
Both the conventional and HAWK situations with pedestrians in roundabouts are problematic, because of that exit point issue, which could potentially lock up the entire circular roadway in the right (wrong) traffic load and travel patterns.  If you're going to get into a situation where the traffic is going to have to stop within the circular roadway, you might as well have the crosswalk go across the circular roadway instead of across the approach.

Or better yet, don't build a roundabout in a spot with high pedestrian volumes, especially a multi-lane one where motorists seem to have enough difficulty processing the information to enter the circular roadway safely, without having to worry about another mode of transportation coming from yet another angle.  With the phased approach of signalized intersections, you don't have pedestrians going one direction locking up an entire intersection.

Theoretically, if you were going through all the trouble of installing a HAWK at a multi-lane roundabout like Homer Watson/Block Line, for the cost, I almost wonder if it may make as much as sense to meter the roundabout approaches like freeway onramps.  After all, the circular roadway in a roundabout is just a really miniature beltway.  It'll eliminate the decision-making of determining when it's safe to enter the multi-lane fray (the decision becomes objective rather than subjective), the red phases could be prolonged as needed when there's pedestrians without the nasty lockup issue, and the conflict points would become less . . .conflicting. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 12, 2016, 10:16:49 AM
The HAWK may have compliance issues now, but in several years, as drivers come to understand their meaning, I suspect that they'll provide a superior crossing option for roundabouts, especially those with two or more lanes.

A 2011 study analyzed the performance of a Pedestrian Hybrid Beacon (PHB, also known as HAWK) at a three-lane roundabout in Oakland County, Michigan.  A link to the 115 page report is below.  The chart on page 49 lists the driver behavior at the HAWK during different signal intervals along the three-lane approach.  During the steady red / walk phase, 94.4% of drivers came to a stop at the entry leg.  However, only 68.9% of drivers came to a stop at the exit leg.  Nearly 1 in 3 drivers exiting the roundabout disregarded the solid red and drove through the crosswalk when a WALK indication was being displayed to the pedestrian.  Drivers appear to be less aware of the HAWK signal on the exit leg.  It’s not necessarily that drivers don’t know what to do; they just aren’t reacting in time. 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Compliance_zpsmkhnlbef.png)
http://www.rcocweb.org/Lists/Publications/Attachments/126/HAWK%20Final%20Report%202011.pdf

Ok, but would the HAWK be safer than a roundabout with no signalized crosswalks?  I would argue NO.  Pedestrians get a false sense of security when a “WALK”  indication is displayed.  Personally, my head is on a swivel when crossing the road, but I see so many pedestrians barely paying attention, just assuming it’s safe to step into the crosswalk because their “WALK”  came up.  That pedestrian behavior can be dangerous when 31.1% of drivers are disregarding the solid red indication.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on March 12, 2016, 02:52:24 PM
Ok, but would the HAWK be safer than a roundabout with no signalized crosswalks?  I would argue NO.  Pedestrians get a false sense of security when a “WALK”  indication is displayed.  Personally, my head is on a swivel when crossing the road, but I see so many pedestrians barely paying attention, just assuming it’s safe to step into the crosswalk because their “WALK”  came up.  That pedestrian behavior can be dangerous when 31.1% of drivers are disregarding the solid red indication.

That's for sure. I saw the RRFB in that study you linked above. That looks like a promising alternative, though the HAWK looks promising for entry legs, and I suspect exit-leg compliance may increase over time as HAWKs become more commonplace; my suspicion is that driver's have about the same reaction time to the HAWK as they do to the pedestrians themselves. So, I don't think there's any harm in installing HAWK signals. After all, the alternative is signalized junction with the same WALK/DON'T WALK signals, and about the same number of people who are either swiveling their heads around, or not looking at all.

We really ought to consider Pelican phasing, like in the UK. They use the standard R/Y/G signal setup, with solid red during the WALK phase, and flashing amber during the DON'T WALK phase. If the iffy compliance with HAWK signals has anything to do with failure to understand the signals themselves, perhaps compliance would go up when people meet a standard traffic light.


Though I will agree that roundabouts are not a particularly good idea in urban areas (though one-lane roundabouts likely work fine in both urban and rural areas alike), we still have to consider the safety of pedestrians even in the most remote of roundabouts. Unless we plan on dumping them altogether (a bad idea), we need to find a way to make the pedestrian crossings at roundabouts safer.

In terms of the ADA, they may prefer signalized crossings at roundabouts. Those who are blind have trouble telling when it's safe to cross. The Pelican crossing above has a chirping noise for the WALK phase, and may be helpful for those individuals.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on March 12, 2016, 07:17:31 PM
^^ there's also a spinning cone under the box with the button as an added feature for sensory impaired people.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on March 13, 2016, 03:12:44 AM
^^ there's also a spinning cone under the box with the button as an added feature for sensory impaired people.

Tom Scott demonstrated that feature in one of his videos. Genius idea..

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 21, 2016, 02:34:43 PM
Another driver was killed at a roundabout in Carmel.   Of the roughly 100 roundabouts in Carmel, three have been the site of a fatal crash since 2014.  Here are news reports of the fatal crashes that have occurred:

Fatal crashes at Carmel roundabouts:
http://fox59.com/2014/08/06/one-dead-in-carmel-accident-passenger-taken-to-hospital/
http://fox59.com/2014/09/26/person-dead-after-motorcycle-accident-in-carmel/
http://www.indystar.com/story/news/crime/2016/03/18/driver-killed-carmel-roundabout-crash/81967984/
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on March 21, 2016, 03:52:13 PM
Another driver was killed at a roundabout in Carmel....http://www.indystar.com/story/news/crime/2016/03/18/driver-killed-carmel-roundabout-crash/81967984/

If distraction is at play here, he could have just as easily run a stop sign or signal. At least he hit the central concrete decorations instead of another car.
Title: Re: Crash prone 'modern roundabouts'
Post by: paulthemapguy on March 21, 2016, 04:31:30 PM
I was at that pair of Hilliard roundabouts just last month!  People in Ohio have no idea how to use them, apparently.  It was chaos!  I thought a yield sign at each and every approach would make them pretty self-explanatory...nope!  And if this is kind of like a big 6-way intersection, why not install one big roundabout to accommodate all 3 through-roads.

(sidenote:  there's a really sweet comic/games shop called Packrat Comics right near these roundabouts.  That's why I ended up in that area XD)
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on March 22, 2016, 05:33:08 AM
Another driver was killed at a roundabout in Carmel.   Of the roughly 100 roundabouts in Carmel, three have been the site of a fatal crash since 2014.  Here are news reports of the fatal crashes that have occurred:

Fatal crashes at Carmel roundabouts:
http://fox59.com/2014/08/06/one-dead-in-carmel-accident-passenger-taken-to-hospital/
http://fox59.com/2014/09/26/person-dead-after-motorcycle-accident-in-carmel/
http://www.indystar.com/story/news/crime/2016/03/18/driver-killed-carmel-roundabout-crash/81967984/

The interesting thing to note about that latest Carmel crash is that it occurred at the Westfield Blvd and E 96th St roundabout (https://www.google.com/maps/@39.9271462,-86.1267491,213m/data=!3m1!1e3), which is a three-leg single-lane roundabout with one right turn bypass from Westfield NB to 96th EB.  Based on a quickie measurement on Google Maps, the center island is about 120 ft. in diameter.  The crash did occur on St. Patrick's Day at night, so one can't rule out impairment, but there's no indication of that yet in the news reports.

If distraction is at play here, he could have just as easily run a stop sign or signal. At least he hit the central concrete decorations instead of another car.

Considering that he got all the way to the middle of the roundabout, I'd say the type of intersection is moot.  If the impact with the central island was severe enough to kill him, reason stands that had there been another car in the roundabout there, it could have been just as ugly as a wreck at a stop or signal-controlled intersection.  There's not much deflection at the Westfield/96th roundabout--this also appears to be the case with the 106th/Pennsylvania and 126th/Hazel Dell roundabouts, which were the sites of the previous accidents.

It's also worth noting that in every case, we're looking at single-vehicle fatal fixed object collisions caused by hitting curbing, and resulting in particularly violent impacts.  I'd be curious to see the stats for these three roundabouts in question.

Edit: Doing a little research (typed in 96th and Westfield accident Carmel), and found there was another fatal accident at this same roundabout in 2007, which killed two (http://www.theindychannel.com/news/2-men-killed-in-carmel-crash).  The car was found in the center island.  Another news story (http://www.wthr.com/story/7201916/police-driver-was-drunk-in-carmel-roundabout-crash) has police saying that the driver was drunk and entered the roundabout going "at least 62mph".
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 22, 2016, 10:57:29 AM
There are roughly 100 modern roundabouts in Carmel, Indiana with 4 known fatal roundabout crashes occurring since their inception.  So how does that compare to other parts of the country?  I decided to look at the fatalities that have occurred at the 100 most crash prone intersections in SE Michigan.  I chose SE Michigan because it has publically accessible data for every intersection in the region dating back a decade.  Of the 100 most crash prone intersections in SE Michigan, there have been 29 fatal crashes (23% of the intersections were the site of a fatal crash and 4% had multiple fatal crashes).

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/top100Rbs_zpsxv15qfla.png)
http://semcog.org/data-and-maps/high-frequency-crash-locations

The numbers initially look pretty good for the roundabouts.  There were only 4 fatal crashes at the 100 Carmel roundabouts compared to 29 fatal crashes at the 100 most crash prone intersections in SE Michigan.  This equates to an 86% reduction in fatal crashes.  However, there are some important factors to consider:

#1.  There are roughly 100 roundabouts in Carmel, but back in 2005 - the first year crash data was analyzed for the intersections in SE Michigan - there were only about a half dozen roundabouts in Carmel.  The roundabout craze hadn’t taken off yet.   This doesn’t make it a fair comparison and underestimates the fatal crashes that may have occurred in Carmel had there been 100 roundabouts back in 2005. 

#2.   Carmel has a population of roughly 85,000 people whereas SE Michigan has a population of 4.7 million people.  Analyzing the top 100 crash prone intersections in a region of 4.7 million people is going to be weighted towards high volume intersections whereas many of the Carmel roundabouts are single-lane with relatively low traffic volumes.  Obviously, intersections with 70,000 vehicles per day (ie. major SE Michigan intersections) are more likely to see a fatal crash than an intersection with 15,000 vehicles per day (ie. single-lane Carmel roundabouts). 

#3.  I don’t have an accurate database of the Carmel crashes and am relying on news articles to estimate how many fatal roundabout crashes have actually occurred over the past 10 years.  Potentially, the fatal crashes that have occurred inside Carmel roundabouts are being underestimated.

Based on these 3 factors, the 86% reduction in fatal crashes isn’t as good as it sounds.  There is one more caveat though.  This is looking at fatal crashes and not total fatalities.  When looking at total fatalities, the numbers might look better for the Carmel roundabouts (since a fatal crash at an intersection may be more prone to multiple fatalities).  I just didn’t take the time to parse through the crash forms to see how many fatalities occurred in each of the 29 fatal crashes.  This can be easily done though.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 22, 2016, 12:14:10 PM
Let’s look at it this way… Over the past 27 months, the 100 roundabouts in Carmel has been the site of 3 fatal crashes.  That equates to an average of 1.33 fatal crashes per year.  The top 100 crash prone SE Michigan intersections have seen on average 2.9 fatal crashes per year. 

(1.33/2.9) -1 = -54%   

Factor #1 is dealt with in this shorter 27 month analysis since we are comparing crash data from roughly 100 roundabouts to 100 SE Michigan intersections.  But we are getting farther and farther away from the 90% reduction in fatal crashes.  The Carmel roundabouts are now only seeing a 54% reduction in fatal crashes.  And we still haven’t dealt with Factor #2.  The traffic volumes at Carmel roundabouts aren’t as high as the intersections in SE Michigan.  Many of the SE Michigan intersections have traffic volumes double and triple that of the single-lane roundabouts found in Carmel.  If you factor in the traffic volumes, the reduction in fatalities at Carmel roundabouts just hasn't been that impressive.

It’s been alluded to that the majority of people dying at roundabouts are drunk.  The safety numbers stated in the literature is that roundabouts reduce fatalities by 90%.  That is the number I’m focusing on and it includes alcohol related fatal crashes.  You can’t just ignore a fatality because somebody was drunk.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on March 22, 2016, 10:08:58 PM
Heck, if *only* half as many people are dying instead of a tenth as many people, let's just tear all the roundabouts out and let the carnage recommence.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 23, 2016, 07:30:58 AM
Heck, if *only* half as many people are dying instead of a tenth as many people, let's just tear all the roundabouts out and let the carnage recommence.

Having 50% less fatalities in Carmel isn't that impressive when the typical Carmel roundabout has 50% less traffic though.  Over the past 27 months, the fatality rate at Carmel roundabouts has been similar to the fatality rate at non-roundabout communities.  Carmel has had a bad run over the past 27 months when it comes to fatalities at roundabouts. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on March 23, 2016, 01:16:08 PM
Heck, if *only* half as many people are dying instead of a tenth as many people, let's just tear all the roundabouts out and let the carnage recommence.

Having 50% less fatalities in Carmel isn't that impressive when the typical Carmel roundabout has 50% less traffic though.  Over the past 27 months, the fatality rate at Carmel roundabouts has been similar to the fatality rate at non-roundabout communities.  Carmel has had a bad run over the past 27 months when it comes to fatalities at roundabouts.

Have you compared Carmel's crash stats to other cities of the same population?
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on March 23, 2016, 03:25:19 PM
Having 50% less fatalities in Carmel isn't that impressive when the typical Carmel roundabout has 50% less traffic though.

Exactly.  It's about the per MEV rate.

I'm still looking around to see if the crash data is easily accessible for Carmel.  As much as I love to bag on ODOT, at least they have a publicly-searchable crash statistics database.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 23, 2016, 03:26:47 PM
Have you compared Carmel's crash stats to other cities of the same population?

Dearborn, Michigan has a population of 98,153 compared to Carmel’s population of 85,927.  Over the past 3 years there have been 3 fatal crashes at Dearborn’s top 100 most crash prone intersections.  There have also been 3 fatal crashes at Carmel’s roughly 100 roundabouts during the same time period.  Maybe Carmel has been on the wrong side of the bell curve lately, but for whatever reason there has been a string of roundabout fatalities in the city of Carmel.

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on March 23, 2016, 03:40:05 PM
Have you compared Carmel's crash stats to other cities of the same population?

Dearborn, Michigan has a population of 98,153 compared to Carmel’s population of 85,927.  Over the past 3 years there have been 3 fatal crashes at Dearborn’s top 100 most crash prone intersections.  There have also been 3 fatal crashes at Carmel’s roughly 100 roundabouts during the same time period.  Maybe Carmel has been on the wrong side of the bell curve lately, but for whatever reason there has been a string of roundabout fatalities in the city of Carmel.

Why not expand the year measure to 10 years? 20 years? That's solid data. You seem hard-set on the last three years, which are clearly Carmel's worst.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 23, 2016, 04:44:11 PM
Why not expand the year measure to 10 years? 20 years? That's solid data. You seem hard-set on the last three years, which are clearly Carmel's worst.

Roundabouts didn’t exist in Carmel 20 years ago.  Even 10 years ago there were maybe only a half-dozen to a dozen roundabouts in the city.  It’s hard to analyze data that doesn’t exist.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on March 23, 2016, 04:58:49 PM
He's well known to cherry pick data. And because an accident occured near a roundabout and had nothing to do with the functionality of a roundabout (such as a drunk driving straight into the center) doesn't change his opinion that the roundabout itself is defective.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on March 23, 2016, 05:14:13 PM
Why not expand the year measure to 10 years? 20 years? That's solid data. You seem hard-set on the last three years, which are clearly Carmel's worst.

Roundabouts didn’t exist in Carmel 20 years ago.  Even 10 years ago there were maybe only a half-dozen to a dozen roundabouts in the city.  It’s hard to analyze data that doesn’t exist.

You'd be analyzing before/after data.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 23, 2016, 05:53:12 PM
Carmel, the self-proclaimed roundabout capital of America, had the same number of fatal crashes as Dearborn, Michigan (a city with ZERO roundabouts).  That's a fact everybody can excuse away all they want.  Have fun with that. 
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on March 23, 2016, 10:59:09 PM
Carmel, the self-proclaimed roundabout capital of America, had the same number of fatal crashes as Dearborn, Michigan (a city with ZERO roundabouts).  That's a fact everybody can excuse away all they want.  Have fun with that. 

What you call "excus[ing] away," statisticians call "controlling for other variables." But sure, we'll play your game. Compare the number of fatal accidents in Dearborn to fatal accidents in Carmel, not over your cherry-picked last 27 months, but the last 10 years - a nice, even, round number, nothing up my sleeve.

Until you do at least that, as far as I'm concerned you're not engaging in honest research, you're just engaging in a vendetta against a type of intersection you seem to personally and irrationally dislike.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 24, 2016, 12:10:34 AM
^Carmel currently has 95 roundabouts.  I'm comparing the fatal crashes of 100 Dearborn intersections to the fatal crashes of 95 Carmel roundabouts.  Each year you go back there are fewer and fewer Carmel roundabouts to analyze.  It wouldn't be fair to compare the number of fatal crashes at Dearborn's 100 most dangerous intersections over the past decade to the number of fatal crashes at Carmel's roundabouts (since 10 years ago, there were only about a dozen roundabouts in Carmel).  That's apples to bananas.  Admittedly this is a back of the napkin analysis, but your suggestion totally throws off the numbers.  While we are at it, you might as well compare the fatal crashes in Chicago to Billings, Montana. 

I just believe the safety benefits of roundabouts are being over estimated.  Keep in mind, the national safety numbers so often cited in literature is based on a study that is over 15 years old.  Roundabouts have evolved at lot since 2000 when the Insurance Institute for Highway Safety released their report.  The more recent safety studies on roundabouts have found that in many cases total crashes are going up (ie. Wisconsin study found a 12% increase in total crashes, not a 39% decrease as cited in the 2000 IIHS study).  You mention "honest research", yet there are so many DOTs that cite the 2000 IIHS study like it is gospel to push for a roundabout.  That to me isn't honest either.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on March 24, 2016, 01:11:56 AM
^Carmel currently has 95 roundabouts.  I'm comparing the fatal crashes of 100 Dearborn intersections to the fatal crashes of 95 Carmel roundabouts.  Each year you go back there are fewer and fewer Carmel roundabouts to analyze.  It wouldn't be fair to compare the number of fatal crashes at Dearborn's 100 most dangerous intersections over the past decade to the number of fatal crashes at Carmel's roundabouts (since 10 years ago, there were only about a dozen roundabouts in Carmel).  That's apples to bananas.  Admittedly this is a back of the napkin analysis, but your suggestion totally throws off the numbers.  While we are at it, you might as well compare the fatal crashes in Chicago to Billings, Montana.

Deerborn has 100 conventional signals. 10 years ago, Carmel had mostly signals, so 10 years ago, the cities had much more in common. Now that Carmel has more roundabouts, the comparison would be whether or not fatal collisions in Carmel have dropped over time with the new roundabouts, and whether or not the not number of fatal collisions in Deerborn has dropped or stayed constant since they didn't change anything.

The comparison is Carmel, who changed over to roundabouts, to Deerborn, who changed nothing.
Title: Re: Crash prone 'modern roundabouts'
Post by: Landshark on March 26, 2016, 02:52:07 PM
Carmel, the self-proclaimed roundabout capital of America, had the same number of fatal crashes as Dearborn, Michigan (a city with ZERO roundabouts).  That's a fact everybody can excuse away all they want.  Have fun with that.

Carmel & Dearborn are apples to oranges.   One is older dense innercity, the other sprawly modern suburbia.   Not only do the physical designs greatly differ, but so do the demographics.  I am sure Carmel has lower % of transit ridership, longer average auto trips, etc.   I also wouldn't be surprised if the average speed limit was also higher in Carmel vs. Dearborn. 



Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 27, 2016, 01:08:40 PM
Carmel & Dearborn are apples to oranges.   One is older dense innercity, the other sprawly modern suburbia.   Not only do the physical designs greatly differ, but so do the demographics.  I am sure Carmel has lower % of transit ridership, longer average auto trips, etc.   I also wouldn't be surprised if the average speed limit was also higher in Carmel vs. Dearborn. 

Take Troy, Michigan as the comparison.  Troy has roughly the same population as Carmel and is the poster child for “suburban sprawl” .  Over the past 4 years the 100 most crash prone intersections in Troy has been the site of 3 fatal crashes.  This is the same number of fatal crashes as Carmel’s roundabouts over the same time period.  All things being equal, Carmel should have had fewer fatal crashes:

#1.  This analysis is comparing the fatal crashes of 100 Troy intersections to only 95 Carmel roundabouts.  And back in 2013, there was only about 60-70 roundabouts in Carmel.  Even though fewer intersections were analyzed, Carmel had the same number of fatal crashes as Troy. 

#2.  Average traffic volumes at Troy intersections are likely much higher than the Carmel roundabouts.  Some of the intersections in Troy experience 70,000 vehicles per day.  I don’t know of a single roundabout in the entire country with traffic counts approaching that.  Even though the Carmel roundabouts have lower traffic volumes, they had the same number of fatal crashes.   

The fact is over the past 4 years Carmel roundabouts have been the site of 3 fatal crashes.  Other similarly sized communities in the United States have had the same number of fatalities as Carmel has had.  Where is the 90% reduction in fatal crashes?
Title: Re: Crash prone 'modern roundabouts'
Post by: roadfro on March 27, 2016, 07:16:02 PM
We really ought to consider Pelican phasing, like in the UK. They use the standard R/Y/G signal setup, with solid red during the WALK phase, and flashing amber during the DON'T WALK phase. If the iffy compliance with HAWK signals has anything to do with failure to understand the signals themselves, perhaps compliance would go up when people meet a standard traffic light.


Just catching up on this thread after several weeks. I know it's a bit off topic, but I had to chime in to agree with this statement.

I have not been a fan of the HAWK signal style since I saw it proposed for the 2009 MUTCD. The Pelican crossing signal demonstrated here makes much more sense intuitively, in the context of existing signal indications, and addresses two things I don't like with a HAWK (signal is dark until ped activation, and the wig-wag red). The only downside is that you couldn't use the Pelican signal at the entrance to a roundabout, as was mentioned earlier in the thread–although really, a signal at the entrance to a roundabout is counter-intuitive to the roundabout controls anyway...
Title: Re: Crash prone 'modern roundabouts'
Post by: renegade on April 05, 2016, 08:21:53 AM
I think I'll leave this here ...

http://www.mlive.com/news/ann-arbor/index.ssf/2016/04/road_commission_improves_state.html#incart_river_home

Number of crashes at State and Ellsworth roundabout drops following initial spike

It's getting better.  The idiots are beginning to learn how to navigate it.  And it's not nearly as bad as someone who does not live here makes it out to be.  I have to deal with it every day, and have yet to see an accident.  I don't think anyone has died there, either.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 05, 2016, 08:34:57 PM
I think I'll leave this here ...

http://www.mlive.com/news/ann-arbor/index.ssf/2016/04/road_commission_improves_state.html#incart_river_home

Number of crashes at State and Ellsworth roundabout drops following initial spike

It's getting better.  The idiots are beginning to learn how to navigate it.  And it's not nearly as bad as someone who does not live here makes it out to be.  I have to deal with it every day, and have yet to see an accident.  I don't think anyone has died there, either.

Here is ten years of crash data for State and Ellsworth (green = pre-roundabout; yellow=roundabout construction year; red = post-roundabout).  You can spin it however you like, but the fact is there has been a spike in total crashes without a reduction in injury crashes.  I didn't see 2015 injury accidents listed in the article renegade cited so that was not included in the chart.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/untitled11ystats_zpse5i7jcwm.png)
http://semcog.org/Data-and-Maps/High-Frequency-Crash-Locations/Point_Id/81016689/view/RoadIntersectionCrashDetail
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 07, 2016, 02:01:08 PM
#2.  Average traffic volumes at Troy intersections are likely much higher than the Carmel roundabouts.  Some of the intersections in Troy experience 70,000 vehicles per day.  I don’t know of a single roundabout in the entire country with traffic counts approaching that.  Even though the Carmel roundabouts have lower traffic volumes, they had the same number of fatal crashes. 

Then what we need is a comparison between signalized intersections and roundabouts where traffic volumes are comparable as well as city sizes.  This would yield apples-to-apples data to review:  similar city sizes make for a meaningful comparison of total crashes and fatalities, while similar traffic volumes made for a meaningful comparison of intersection designs.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 08, 2016, 10:14:37 AM
I just find it ironic that Carmel Indiana, the roundabout capital of America, has had the same number of fatal crashes as similarly sized communities with zero roundabouts.  Articles will keep regurgitating the IIHS safety stat that says modern roundabouts reduce fatal crashes by 90%.  If you say it enough times it must be true.  A lot of people on this thread believe it.
Title: Re: Crash prone 'modern roundabouts'
Post by: paulthemapguy on April 08, 2016, 12:29:10 PM
I can't see roundabouts reducing the number of fatal crashes if they occur in low-speed areas...But then again you shouldn't be putting roundabouts on highways with high speeds in the first place!  If someone proposed a roundabout on a high speed roadway, I'd say, "you're gonna put a big circle in the middle of a road where the speed is 45-55mph?  Are you serious?"  Doesn't stop some agencies though.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on April 08, 2016, 12:40:15 PM
I can't see roundabouts reducing the number of fatal crashes if they occur in low-speed areas...But then again you shouldn't be putting roundabouts on highways with high speeds in the first place!  If someone proposed a roundabout on a high speed roadway, I'd say, "you're gonna put a big circle in the middle of a road where the speed is 45-55mph?  Are you serious?"  Doesn't stop some agencies though.

See NJ 70/72. https://goo.gl/maps/c6XhdHMXcVn  Although it's a Jersey traffic circle, it does have roundabout features (everyone yields prior to entering).  Speed limits on 3 of the spokes are 55 mph; on the other 2 spokes, limits are 50 mph.

No issues here.  You wouldn't think it by looking at the aerial photos, but it can jam up during rush hours!
Title: Re: Crash prone 'modern roundabouts'
Post by: JMAN_WiS&S on April 08, 2016, 12:47:00 PM
The multi lane roundabout at US 53 and Town Hall Rd south of the US 53/I94 interchange in Eau Claire Wisconsin has been subject to quite a few crashes recently and now the DOT is proposing changes such as building the mound up in the center, and replacing the current advanced warning signs with fluorescent ones, even though the ones on US 53 have flashers on them. The major issue is the speed limit right in the area is 55 mph and the roundabout limit is 15.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 08, 2016, 12:48:57 PM
I can't see roundabouts reducing the number of fatal crashes if they occur in low-speed areas...But then again you shouldn't be putting roundabouts on highways with high speeds in the first place!  If someone proposed a roundabout on a high speed roadway, I'd say, "you're gonna put a big circle in the middle of a road where the speed is 45-55mph?  Are you serious?"  Doesn't stop some agencies though.

See NJ 70/72. https://goo.gl/maps/c6XhdHMXcVn  Although it's a Jersey traffic circle, it does have roundabout features (everyone yields prior to entering).  Speed limits on 3 of the spokes are 55 mph; on the other 2 spokes, limits are 50 mph.

No issues here.  You wouldn't think it by looking at the aerial photos, but it can jam up during rush hours!


Just a single one? Not a big deal!  How about a real chain?
https://www.google.com/maps/place/Albany,+NY/@42.6428116,-73.8497982,16z/data=!3m1!1e3!4m2!3m1!1s0x89de0a34cc4ffb4b:0xe1a16312a0e728c4
55 MPH posted throughout.

I often compare roundabout construction with prescribing insulin: in the right situation is a life saver, but insulin doesn't help broken bones or pneumonia...
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 08, 2016, 01:04:27 PM
Just a single one? Not a big deal!  How about a real chain?
https://www.google.com/maps/place/Albany,+NY/@42.6428116,-73.8497982,16z/data=!3m1!1e3!4m2!3m1!1s0x89de0a34cc4ffb4b:0xe1a16312a0e728c4
55 MPH posted throughout.

That doesn't even make sense to be signed at 55 mph.  Looks like 45 might be more appropriate.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 08, 2016, 01:25:27 PM
^On streetview it appears Slingerlands Bypass is posted at 45 mph through the roundabouts.  It only increases to 55 mph once you get past the string of roundabouts.   Kalvado, is it possible the speed limit was just recently reduced?  The streetview images are from September 2015. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 08, 2016, 01:34:36 PM
^On streetview it appears Slingerlands Bypass is posted at 45 mph through the roundabouts.  It only increases to 55 mph once you get past the string of roundabouts.   Kalvado, is it possible the speed limit was just recently reduced?  The streetview images are from September 2015.
I wish I remember. I drive there once every few months. I am usually on a slower side of things going 60. But I never been there during rush hour.
Before roundabouts that used to be posted 55.
Title: Re: Crash prone 'modern roundabouts'
Post by: Sykotyk on April 08, 2016, 10:26:47 PM
Just one clarification for those discussing the Carmel/SE Michigan statistics.... In Carmel you're counting ONLY the 100 roundabouts, while in SE Michigan you're counting the top 100 most crash prone intersections, rather than ALL intersections.

Let's say there's 10,000 intersections covered under the data used for SE Michigan.

Now the data is 4/100 to 29/10,000.

These are supposed to be safer. In a lot of instances, they are not. And the main culprit, to me, is that many people do not know what the YIELD sign truly means. They're used to STOP, and in the absence of STOP their thought is to go. We see it on on-ramps all the time where the YIELD sign on the ramp is never heeded. They weave into traffic, cut off cars in the right lane, flip you off for not letting them over, etc. They don't consider it an actionable sign.

This has been ingrained for decades for some of these people and now suddenly throwing a 'new' type of interchange at them will not get them to stop their bad habits. It just amplifies them.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 08, 2016, 10:45:08 PM
I've never seen the problem at roundabouts to be a failure to yield. No, I've seen much more confusion arise when a driver can't STOP yielding. At some point, you have to grow some balls and GO already.
Title: Re: Crash prone 'modern roundabouts'
Post by: Sykotyk on April 09, 2016, 12:56:13 AM
I've never seen the problem at roundabouts to be a failure to yield. No, I've seen much more confusion arise when a driver can't STOP yielding. At some point, you have to grow some balls and GO already.

But that has nothing to do with an accident. A car doesn't get hit in the roundabout because a driver is timid to enter.

An accident occurs because a car enters when they're not supposed to.

The problem is, a roundabout should be treated in the same manner as a four-way stop. If it's just one car from one approach, you get to go unimpeded. If it's two cars, then the same process as a stop sign (vehicle to the right goes, if it's on-coming traffic, they can both go). if it's W and S that arrive, S gets to go first because they're on the right.

That's generally understood by the populus (though, there are many I've seen that don't understand when you get to go at a jammed four-way stop sign). The issue is when a roundabout is jammed with traffic stalled at 2, 3, or 4 approaches. The first car into the roundabout gives the impression to those behind them that they can 'tag along' and suddenly that entire approach clears the roundabout while the other approaches all have to wait. And that's when you get cars slightly behind the line racing to get up into the roundabout before another approach can start. And then the next approach begins to clear out in the same manner.

It should be one-at-a-time in a counter-clockwise fashion, just as a stop sign. This isn't the big traffic circles found in New England. These are much smaller and REPLACE stop-signed or signalized intersections. The circle is not a road in the manner of how a large traffic circle, generally found in the New England states, is basically entering an entirely new road, one that is one-way and forms a loop.

That's the problem I've come across. And it's especially true during rush hour when a roundabout is placed on a major thoroughfare at an intersection with a less used crossroad. The thoroughfare treats it like they get constant stream of traffic and the side roads have to wait. Rather than the car behind the car at a yield sign realizing they must wait until the first car at each other approach also clears the roundabout. And THEN they get to go. Same as a stop sign.

Instead, it's treated as "since the car in front of me is the only one in the roundabout, I can enter because I don't have to yield to anyone on my left". Which is true, but it makes entering the roundabout an aggressive act, rather than a defensive/regulated act.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on April 09, 2016, 07:19:57 AM
That doesn't even make sense to be signed at 55 mph.  Looks like 45 might be more appropriate.
Surely US drivers are capable of not driving at the speed limit if it is unsafe to do so there. Oh wait...

These are on a 70mph Dual Carriageway trunk road (https://www.google.co.uk/maps/@52.0124053,-1.1233869,13.58z). (BTW, the UK doesn't allow reduced limit for one thing like a junction, preferring ample warning signs, rumble strips, and drivers to not be slaves to driving to the posted limit. Nor does it allow traffic signals on 70mph roads). AADT on the A43 is around 37000 in this area (between 36200 north of Brackley and 37800 south of the A421). Looking, it seems that each roundabout on the A43 (with the exception of the ones at the M40, where there was a terrible 'improvement' scheme that has now been reversed) seems to get about 8 collisions every 5 years, with perhaps 1 of them fatal. There's room for improvement, but the only way to do it is grade-separation (which, as well as expensive and gaining little in journey time savings, will increase the number of idiots driving 100mph along the road, undermining all the safety benefits as more people crash off, killing themselves).
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on April 09, 2016, 07:39:13 AM
But that has nothing to do with an accident. A car doesn't get hit in the roundabout because a driver is timid to enter.
Do accident stats only include those on the circulatory carriageway, or also at approaches? A timid driver is likely to get driven into the back of. And they also create accidents around them - you even give an example of how: a not very assertive driver creates a queue, and when they go, the queue thinks its clear for them.

Better driver education would go a long way to improving US roundabout safety.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 09, 2016, 10:23:05 AM
But that has nothing to do with an accident. A car doesn't get hit in the roundabout because a driver is timid to enter.
Do accident stats only include those on the circulatory carriageway, or also at approaches? A timid driver is likely to get driven into the back of. And they also create accidents around them - you even give an example of how: a not very assertive driver creates a queue, and when they go, the queue thinks its clear for them.

Better driver education would go a long way to improving US roundabout safety.

Also...  A driver too timid to go from the entering left lane makes for an obstruction the right-lane driver might not be able to see around; said right-lane driver might take an unwarranted chance at entering the roundabout out of impatience.

Also...  What I've seen more often is drivers who become timid within the circulating roadway, sometimes coming to a full stop inside the roundabout.  This most certainly does increase the risk of accident.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 09, 2016, 01:36:27 PM
Also...  What I've seen more often is drivers who become timid within the circulating roadway, sometimes coming to a full stop inside the roundabout.  This most certainly does increase the risk of accident.

We have a roundabout with a crosswalk 10' from the outer circle. I've been there in both capacities - and as pedestrian, I am really scared since you are not seen until last second. You better wait until traffic gap.. and then someone hits their brakes and stops in the middle of the circle...  Hopefully they will not hit me when rear-ended...
As a driver, I am really scared of pedestrians in that crosswalk - whatever I do would be wrong, both stopping in the circle and  not yielding to crosswalker..
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on April 09, 2016, 01:56:19 PM
We have a roundabout with a crosswalk 10' from the outer circle.
That's too close. Needs to be more like 30' - especially on the exit side of the roundabout.

When we have crossings next to roundabouts (normally one, maybe two, car lengths from it) in the UK, they aren't ones that give priority to pedestrians (though obviously road vehicles don't have the right to hit them), but we will have signalised crossings or zebras (where cars are meant to yield to pedestrians waiting to cross) if they are a bit further down the road and the visibility and stacking issues are sorted.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on April 09, 2016, 04:06:58 PM
Also...  What I've seen more often is drivers who become timid within the circulating roadway, sometimes coming to a full stop inside the roundabout.  This most certainly does increase the risk of accident.

We have a roundabout with a crosswalk 10' from the outer circle. I've been there in both capacities - and as pedestrian, I am really scared since you are not seen until last second. You better wait until traffic gap.. and then someone hits their brakes and stops in the middle of the circle...  Hopefully they will not hit me when rear-ended...
As a driver, I am really scared of pedestrians in that crosswalk - whatever I do would be wrong, both stopping in the circle and  not yielding to crosswalker..

Have a link for that roundabout?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 09, 2016, 07:57:41 PM

We have a roundabout with a crosswalk 10' from the outer circle. I've been there in both capacities - and as pedestrian, I am really scared since you are not seen until last second. You better wait until traffic gap.. and then someone hits their brakes and stops in the middle of the circle...  Hopefully they will not hit me when rear-ended...
As a driver, I am really scared of pedestrians in that crosswalk - whatever I do would be wrong, both stopping in the circle and  not yielding to crosswalker..

Have a link for that roundabout?
https://www.google.com/maps/@42.689025,-73.8315784,71m/data=!3m1!1e3
southwestern leg crossing mostly - it is used by students walking between dorms and campus.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on April 09, 2016, 08:44:08 PM
That's a standard design but it's way too close. College near me has one like that as well.  Moving it about 100 feet from the roundabout allows for a little storage room.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 09, 2016, 10:02:21 PM
That's a standard design but it's way too close. College near me has one like that as well.  Moving it about 100 feet from the roundabout allows for a little storage room.
If you look carefully, there is a foot path which cut across roundabout approach curve, saving maybe 10 feet. You really think that same people would walk 100 feet just because that is where crosswalk is marked?  Then you may be interested in buying that bridge on the interstate!
It is just the case when roundabout was built  for the sake of building a roundabout.  There were a lot of other improvements within that project, but they could be implemented without a circle - and probably at a lower cost.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on April 09, 2016, 10:26:43 PM
What's preventing less from just crossing into the center right now?

There are methods to keep people using the crosswalks. Decorative fencing, for example.

(ugh...less should have been "peds"!!!
Title: Re: Crash prone 'modern roundabouts'
Post by: Sykotyk on April 10, 2016, 02:05:36 AM
What's preventing less from just crossing into the center right now?

There are methods to keep people using the crosswalks. Decorative fencing, for example.

Considering people have to extol energy to walk, making them walk further just makes the find a shortcut. Have you ever seen a grassy area near a building with a well worn foot path because people were too lazy to walk the extra 10-15-20 feet to stay on pavement? Same issue. Only way to stop them would be to line the entire thing with fencing, and that would last as long as the first tractor trailer that goes up and over the curb or drunk at night sideswipes it. And since it's decorative only, it won't stand up to the abuse. And unless its repaired/replaced quickly, it will look like a guady eyesore.

Title: Re: Crash prone 'modern roundabouts'
Post by: johndoe on April 10, 2016, 09:41:31 AM
The problem is, a roundabout should be treated in the same manner as a four-way stop.

if it's W and S that arrive, S gets to go first because they're on the right.

It should be one-at-a-time in a counter-clockwise fashion, just as a stop sign.

The thoroughfare treats it like they get constant stream of traffic and the side roads have to wait.

they must wait until the first car at each other approach also clears the roundabout. And THEN they get to go. Same as a stop sign.

"I can enter because I don't have to yield to anyone on my left". Which is true

Forgive me if this is harsh, but I don't think you understand roundabouts.  Everything I've quoted is wrong.  A roundabout is not a four-way stop.  Entering drivers yield to conflicting vehicles in the circulating roadway; it has nothing to do with the other approaches. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on April 10, 2016, 09:51:49 AM
The problem is, a roundabout should be treated in the same manner as a four-way stop.

if it's W and S that arrive, S gets to go first because they're on the right.

It should be one-at-a-time in a counter-clockwise fashion, just as a stop sign.

The thoroughfare treats it like they get constant stream of traffic and the side roads have to wait.

they must wait until the first car at each other approach also clears the roundabout. And THEN they get to go. Same as a stop sign.

"I can enter because I don't have to yield to anyone on my left". Which is true

Forgive me if this is harsh, but I don't think you understand roundabouts.  Everything I've quoted is wrong.  A roundabout is not a four-way stop.  Entering drivers yield to conflicting vehicles in the circulating roadway; it has nothing to do with the other approaches. 

His one-car-at-a-time idea would hopelessly jam up the roundabout approaches. It take a car a second or two to go thru an intersection. It would take a car several seconds to go thru a roundabout, especially if making a left or u-turn.
Title: Re: Crash prone 'modern roundabouts'
Post by: Sykotyk on April 10, 2016, 12:19:14 PM
The problem is, a roundabout should be treated in the same manner as a four-way stop.

if it's W and S that arrive, S gets to go first because they're on the right.

It should be one-at-a-time in a counter-clockwise fashion, just as a stop sign.

The thoroughfare treats it like they get constant stream of traffic and the side roads have to wait.

they must wait until the first car at each other approach also clears the roundabout. And THEN they get to go. Same as a stop sign.

"I can enter because I don't have to yield to anyone on my left". Which is true

Forgive me if this is harsh, but I don't think you understand roundabouts.  Everything I've quoted is wrong.  A roundabout is not a four-way stop.  Entering drivers yield to conflicting vehicles in the circulating roadway; it has nothing to do with the other approaches. 

How can anything you quoted be 'incorrect' when I specifically stated "should" in the very first line. It was my opinion.

The problem with roundabouts is people race to be the next one in, rather than following a set pattern on how to enter the roundabout. Wouldn't a four-way stop be just as dangerous if there were no set manner to enter other than 'whoever gets into the intersection first?'
Title: Re: Crash prone 'modern roundabouts'
Post by: Sykotyk on April 10, 2016, 12:27:54 PM
The problem is, a roundabout should be treated in the same manner as a four-way stop.

if it's W and S that arrive, S gets to go first because they're on the right.

It should be one-at-a-time in a counter-clockwise fashion, just as a stop sign.

The thoroughfare treats it like they get constant stream of traffic and the side roads have to wait.

they must wait until the first car at each other approach also clears the roundabout. And THEN they get to go. Same as a stop sign.

"I can enter because I don't have to yield to anyone on my left". Which is true

Forgive me if this is harsh, but I don't think you understand roundabouts.  Everything I've quoted is wrong.  A roundabout is not a four-way stop.  Entering drivers yield to conflicting vehicles in the circulating roadway; it has nothing to do with the other approaches. 

His one-car-at-a-time idea would hopelessly jam up the roundabout approaches. It take a car a second or two to go thru an intersection. It would take a car several seconds to go thru a roundabout, especially if making a left or u-turn.

How would it jam up the approaches anymore than they already are? More than one can be in a roundabout at the same time. But, only one approach at a time in rotation should get to go.

In a roundabout, there is no pattern. It's 'every man, woman, and child for themselves' and what I see at roundabouts is vehicles driving dangerously fast and cutting into the roundabout so they can get through it without waiting.  As for 'yielding' even that is onerous simply because how much space to yield is left up to the one at the yield sign. Yield to traffic in the roundabout would mean the entire roundabout. Or, 10 feet. Whichever doesn't damage their bumper.

And that's not even getting into two-lane or more roundabouts, where now you have merging traffic and lane-changing traffic to deal with, where the worst of it is on your right, the blindside of your vehicle.

Then we're not even discussing the elephant in the room, and that's just inattentive and ignorant drivers who don't know or are unable to handle a particular situation. A stop sign or traffic light has order and structure. A roundabout doesn't. Primarily because they weren't really taught to those who started driving 10-15 or more years ago. Where a yield sign generated delineated financial responsibility for an accident, rather than a steadfast traffic rule. Highway onramps a testament to that.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on April 10, 2016, 01:54:50 PM
How would it jam up the approaches anymore than they already are? More than one can be in a roundabout at the same time. But, only one approach at a time in rotation should get to go.

Quote
they must wait until the first car at each other approach also clears the roundabout. And THEN they get to go. Same as a stop sign.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 10, 2016, 03:00:00 PM
Wouldn't a four-way stop be just as dangerous if there were no set manner to enter other than 'whoever gets into the intersection first?'

But that IS the only set manner to enter a four-way-stop. The only time yielding to the right comes in to play at all is when two cars get there at exactly the same time, which is NOT most of the time. And there are some jurisdictions where yielding to the right isn't even codified, but rather a common courtesy.

In other words, there is a set pattern on how to enter a four-way stop intersection, and that pattern is this: Whoever gets there first goes first; if you and the car to your right get there at the same time, then yield to the other driver (that last part may or may not be codified). Similarly, there is a set pattern on how to enter a roundabout: if nobody is imminently approaching on your left, then go on through; if someone is imminently approaching on your left, then yield.

If all four vehicles approach a roundabout at exactly the same time, then nobody has to wait at all: each can safely enter the roundabout because no other car is yet imminently approaching on the left. If all four vehicles approach a four-way stop at exactly the same time, then nobody quite knows who should go first, and then everyone has to wait one by one.
Title: Re: Crash prone 'modern roundabouts'
Post by: Sykotyk on April 10, 2016, 09:19:58 PM
Wouldn't a four-way stop be just as dangerous if there were no set manner to enter other than 'whoever gets into the intersection first?'

But that IS the only set manner to enter a four-way-stop. The only time yielding to the right comes in to play at all is when two cars get there at exactly the same time, which is NOT most of the time. And there are some jurisdictions where yielding to the right isn't even codified, but rather a common courtesy.

In other words, there is a set pattern on how to enter a four-way stop intersection, and that pattern is this: Whoever gets there first goes first; if you and the car to your right get there at the same time, then yield to the other driver (that last part may or may not be codified). Similarly, there is a set pattern on how to enter a roundabout: if nobody is imminently approaching on your left, then go on through; if someone is imminently approaching on your left, then yield.

If all four vehicles approach a roundabout at exactly the same time, then nobody has to wait at all: each can safely enter the roundabout because no other car is yet imminently approaching on the left. If all four vehicles approach a four-way stop at exactly the same time, then nobody quite knows who should go first, and then everyone has to wait one by one.

When there's already traffic at the intersection, that last line is exactly how it's done. If there's already two cars ahead of you and a line at the other three approaches, you simply wait your turn. Not trying to remember whether you got to the intersection before someone else and go in that order. You go in the sequential order that's already been started. Counter-clockwise, around and around until eventually the traffic is clear.

At a round-about, there is no traffic pattern or rule other than 'yield to traffic in circle' which leaves a wide breadth as to how much space to yield. You get people gunning it to be the next one in the circle, regardless which 'turn' would've been there's at a stop sign. And then you get followers, who continue with the person in front of them. Which effectively becomes a four-phase traffic light with random phases.

And technically, if you're to yield to traffic in the circle, you have to yield to all traffic in the circle, not just whether you can floor it and get out in time before getting T-boned. Including oncoming traffic. Again, if a roundabout is that congested, it should be cleared out similar to a four-way stop: traffic on the right goes first, counter-clockwise, until all the approaches are clear.

Modern roundabouts that are replacing intersections (small medians, not the large 100-200ft behemoths that I consider traffic circles or rotaries like in the northeast), work best on roads that handle intermittent traffic from all directions when traffic volumes generally don't clog up an intersection.

US 59 & US 169 in Garnett, Kansas is a decent example. Two roads with intermittent traffic. It's not steady from any one approach. It's better than signalized, and a lot better than a stop-sign. It works because the intersection never saw a pressing need for other action (four-lane with a median and at-grade ramp system with stop-signs to break up traffic). Most of the time, you'll approach that traffic circle and be the first to go through without impeding traffic from another direction.

You put that roundabout in a downtown, urban, or suburban setting, and suddenly you get traffic. The roundabout doesn't relieve traffic, it only relieves wait times for a signal. But, enough traffic forces its wait time back to a signalized intersection. One thing roundabouts do, though, is create 'steady flow' for business and sidestreet traffic.

Imagine you're pulling out of a business that's just down the road from a traffic circle in a congested area. You constantly have traffic to deal with. Where, before, in a signalized intersection, you have a light that will temporarily block the flow of traffic before the turn phase begins for the perpendicular approaches.

https://goo.gl/maps/AVixtAFGkg32

Brattleboro, VT exit from I-89 to VT/NH-9 & US5. Don't make the mistake of stopping at the second gas station south (the one not at the roundabout). You will have a bear of a time pulling out as you have, essentially, free-flowing freeway traffic exiting to either US5 or NH-9. Or, the through traffic on US-5. If there were a light, you would have occassional pauses to pull out to make the left back to either the highway, north on US-5 or east on NH-9.

Roundabouts/traffic circles have their place. But, a lot of them are being shoehorned into congested areas where they don't serve the need well.

And a lot of that has to do with how drivers handle them. It's a free-for-all, rather than a traffic-control-device. We've seen it for decades with the YIELD sign at the end of on-ramps. Drivers do not heed them. Hell, there's many drivers you'll come across absolutely irate if you don't yield to the on-ramp traffic. That lack of respect and legality to a yield sign has carried over to the roundabout. That yield sign might as well not exist with how little people respect it.

What they need is to remove the YIELD sign and replace it with a STOP sign and a white regulatory sign underneath that states something along the lines of, "For Traffic In Circle Only" similar in manner to how "Except Right Turn" gets placed under many stop signs where the through line turns right at an intersection.

People, overwhelmingly, respect stop signs compared to yield signs. The lack of enforcement for "Failure To Yield" at a yield sign, anywhere, is astounding. At a stop sign, it's much more enforced. Which leads to compliance.

We can have a million and one 'Don't Text and Drive' or 'Don't Drink and Drive' but not one 'Yield means Yield' campaigns.
Title: Re: Crash prone 'modern roundabouts'
Post by: Sykotyk on April 10, 2016, 09:29:15 PM
How would it jam up the approaches anymore than they already are? More than one can be in a roundabout at the same time. But, only one approach at a time in rotation should get to go.

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they must wait until the first car at each other approach also clears the roundabout. And THEN they get to go. Same as a stop sign.

I'm glad you can operate the quote function. Again, 'How would it jam up the approaches anymore than they already are?' If a roundabout were so crowded to have traffic lined up at all four approaches, wouldn't you want traffic to be orderly, or are you content with 'every man for themselves'?
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on April 10, 2016, 10:43:27 PM
How would it jam up the approaches anymore than they already are? More than one can be in a roundabout at the same time. But, only one approach at a time in rotation should get to go.

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they must wait until the first car at each other approach also clears the roundabout. And THEN they get to go. Same as a stop sign.

I'm glad you can operate the quote function. Again, 'How would it jam up the approaches anymore than they already are?' If a roundabout were so crowded to have traffic lined up at all four approaches, wouldn't you want traffic to be orderly, or are you content with 'every man for themselves'?

I would have them operate the way they operate now, which is generally fine.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 11, 2016, 08:09:16 AM
[ Again, 'How would it jam up the approaches anymore than they already are?' If a roundabout were so crowded to have traffic lined up at all four approaches, wouldn't you want traffic to be orderly, or are you content with 'every man for themselves'?
If you have all 4 - or, worse, just 1 leg of roundabout flooded with traffic - you are outside design parameters, and things no longer work. Roundabouts are designed to be a somewhat ordered anarchy, when resources (time in the circle) are not managed, but shared. If one leg grabs 100% of time...
My personal record is sitting 15 minutes waiting for a gap in traffic. After some event was over, circle was flooded with south-to-north bumper to bumper traffic, and I was sitting on the eastern approach without a chance to do anything. Traffic light downstream ensured entire line moved at, or below, 15 MPH, so no gaps at all. I still have to see something like that for general commute, but that is  a probable failure mode for the concept.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 11, 2016, 01:55:28 PM
If there's already two cars ahead of you and a line at the other three approaches, you simply wait your turn. Not trying to remember whether you got to the intersection before someone else and go in that order.

Of course not.  But reaching the tail of the line of cars is not the same thing as getting to the intersection.  At a four-way stop, the only thing influencing your decision to go or wait is what's happening at the other three stop signs at that time.  Likewise, the only thing influencing your decision to go or wait is what's happening on your immediate left at that time.  That's what a stop sign means, and that's what a yield sign means.

And special circumstances require special decision-making.  An eighteen-wheeler, for example, can either make for more people going ahead of their turn (because he's very slow and waves you on, or because traffic needs to clear the intersection for his wide turn) or more people having to wait longer (because their line through the intersection has cleared while the truck is still turning, even though they got to the intersection after the cars that are still blocked).  The even traffic mentioned just up-thread by @kalvado should have paused every so often, even within the circulating roadway, to let him in; that's how polite drivers operate at a similar situation at a four-way stop, and that's how they should operate at a roundabout.

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Counter-clockwise, around and around until eventually the traffic is clear. * * * Again, if a roundabout is that congested, it should be cleared out similar to a four-way stop: traffic on the right goes first, counter-clockwise, until all the approaches are clear.

Actually, it's not that simple.  It's more efficient for each pair of opposing traffic to proceed at the same time, meaning NB and SB cars proceed through simultaneously, then EB and WB cars proceed through simultaneously, and so on.  In this scenario, four cars get through the intersection in only two "cycles" instead of four cycles.  However, this progression only works until, for example, SB is turning left and NB is turning right, then the sequence gets messed up.  There is no simple, perfect, optimal way of ordering the movements at a four-way stop, because different turning movements create different environments.

At a roundabout, it concerns me not one bit when the driver on the opposite side of the intersection got there or which direction he's going.  All that concerns me is what the driver immediately on my left is doing.

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At a round-about, there is no traffic pattern or rule other than 'yield to traffic in circle' which leaves a wide breadth as to how much space to yield. * * * And technically, if you're to yield to traffic in the circle, you have to yield to all traffic in the circle, not just whether you can floor it and get out in time before getting T-boned. Including oncoming traffic.

No more breadth than a yield sign at a simple four-way intersection.  All a yield sign indicates is that you give way to approaching traffic presenting an imminent danger; anything less than imminent is not your concern, because your paths do not conflict.  "Yield to traffic in circle" signage is simply the agency's way of explaining to drivers how a roundabout works, not that they have to wait for the entire circle to clear or some such nonsense.

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You get people gunning it to be the next one in the circle, regardless which 'turn' would've been there's at a stop sign. And then you get followers, who continue with the person in front of them. Which effectively becomes a four-phase traffic light with random phases.

These things happen at four-way stops too.  In neither intersection type, though, do followers make it "effectively become a four-phase traffic light with random phases", because those drivers are outliers and do not have any meaningful effect on the performance of the intersection.

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Modern roundabouts that are replacing intersections (small medians, not the large 100-200ft behemoths that I consider traffic circles or rotaries like in the northeast), work best on roads that handle intermittent traffic from all directions when traffic volumes generally don't clog up an intersection.

I agree.  I should point out that there are some roundabouts in areas of steady traffic that perform quite well, such as the Skaggs roundabout in Branson, Missouri.  That one is a five-leg roundabout that sees much more traffic on three of its approaches than on the other two, and both local and tourist traffic is a steady flow.  It performs great, and was a welcome replacement of what was there previously.

What I think seriously does a roundabout in is heavy traffic volumes, especially when there are traffic signals nearby.  Traffic tailbacks extending through a roundabout are like death to the intersection. 

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US 59 & US 169 in Garnett, Kansas is a decent example. Two roads with intermittent traffic. It's not steady from any one approach. It's better than signalized, and a lot better than a stop-sign. It works because the intersection never saw a pressing need for other action (four-lane with a median and at-grade ramp system with stop-signs to break up traffic). Most of the time, you'll approach that traffic circle and be the first to go through without impeding traffic from another direction.

Excellent example.  A similar four-way roundabout that functions great is the one on US-400 at Fredonia.  Pulling out onto 400 from the side road used to be a dangerous proposition, but now it's much safer without stoplights or stop signs.

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You put that roundabout in a downtown, urban, or suburban setting, and suddenly you get traffic. The roundabout doesn't relieve traffic, it only relieves wait times for a signal. But, enough traffic forces its wait time back to a signalized intersection.

Without nearby traffic signals, it should still be no problem.  Again, I think the killer in urban settings is nearby traffic signals.  Red-light tailbacks reaching the circulating roadway render the roundabout inoperable.  I hadn't much considered roundabout tailbacks reaching the stoplight, but that sort of thing happens with two stoplights anyway.  It's easier to get traffic to not block a signalized intersection than it is to get traffic to not block a whole roundabout.

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One thing roundabouts do, though, is create 'steady flow' for business and sidestreet traffic.

Imagine you're pulling out of a business that's just down the road from a traffic circle in a congested area. You constantly have traffic to deal with. Where, before, in a signalized intersection, you have a light that will temporarily block the flow of traffic before the turn phase begins for the perpendicular approaches.

This is true.  While it is risky business to plan on a break in heavy traffic due to signal timing (sometimes traffic is heavy enough that you never end up getting that gap you were hoping for), no such large gaps can be planned for with roundabouts.  This isn't a problem if traffic is light enough that small gaps emerge, but it does become a problem if traffic is heavy.  There's no easy way around this.

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Roundabouts/traffic circles have their place. But, a lot of them are being shoehorned into congested areas where they don't serve the need well.

This is true.  But it's also true of stop signs and traffic signals, added to locations where a roundabout would serve the need nicely.

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And a lot of that has to do with how drivers handle them. It's a free-for-all, rather than a traffic-control-device. We've seen it for decades with the YIELD sign at the end of on-ramps. Drivers do not heed them. Hell, there's many drivers you'll come across absolutely irate if you don't yield to the on-ramp traffic. That lack of respect and legality to a yield sign has carried over to the roundabout. That yield sign might as well not exist with how little people respect it.

As for yielding at an on-ramp merge...  Many jurisdictions don't even put yield signs at then end of the ramps.  Also, it is common courtesy to slow down or move over for merging traffic.  Basically, on-ramps are widely taken as more of a "form one lane" situation than a true yield situation, despite what signage might be present.  And, actually, this is a good thing:  having to come to a full stop upon merging onto a 65-mph highway is a recipe for disaster.

As for heeding yield signs in general, I agree that they are widely ignored, not just at on-ramps as discussed, but more dangerously at simple four-way intersections; drivers slow down so little for a simple yield intersection that, by the time a crossing vehicle comes into view, there's precious little time to actually stop.  But this is not what I've seen at roundabouts.  People approaching roundabouts are already slowing down due to additional signage and curve geometry, which makes them more ready to truly yield.  I honestly hardly ever see drivers blatantly ignoring yield signs at roundabout approaches the way I see them blatantly ignore them at simple four-way intersections.

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What they need is to remove the YIELD sign and replace it with a STOP sign and a white regulatory sign underneath that states something along the lines of, "For Traffic In Circle Only" similar in manner to how "Except Right Turn" gets placed under many stop signs where the through line turns right at an intersection.

Disagree.  Trying to fix a few bad drivers' behavior through more imperative signs is not going to solve anything.  What would likely result is a great number of drivers stopping for no reason:  by the time they're read the little white placard, they've already come to a full stop.  And then you'd still be left with your stated dilemma of what "in circle" means.  Will they remain stopped till the whole thing clears?  Etc.

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People, overwhelmingly, respect stop signs compared to yield signs. The lack of enforcement for "Failure To Yield" at a yield sign, anywhere, is astounding. At a stop sign, it's much more enforced. Which leads to compliance.

We can have a million and one 'Don't Text and Drive' or 'Don't Drink and Drive' but not one 'Yield means Yield' campaigns.

I'm not sure I've witnessed enough people running a yield sign with a police officer nearby to come to any conclusion about how often it's enforced.  And I'm pretty amazed that you have.  Generally, yield signs are used at low-volume intersections where running one doesn't usually put anyone in jeopardy and, in the case there is actual jeopardy, the chances of a cop being nearby are slim to none.  But whatever.
Title: Re: Crash prone 'modern roundabouts'
Post by: Sykotyk on April 12, 2016, 12:27:52 AM
I've seen it enough in a few places. And I've seen it cropping up at roundabouts. The definition of 'imminent' is the problem. Some drivers are a lot more brazen with their travel into the roundabout than others.

Yes, a STOP w/regulatory sign may cause some to stop without reason. But, there's enough scaredycats that do that as now with yield signs. But, it will slow down the people rolling through unsafely.

The uptick in accidents at these roundabouts is proving that drivers aren't driving properly through them. The issue whether the agencies responsible want to have their heads in the sand, or accept that some drivers simply bugger up the system. Both the timid and the brave.

The thing with signalized or 4-way, was that if you got a green light, your odds of not facing cross-traffic were next-to-nil. Sure, some ran lights. Either inattentive during the phase or the bastards who ran it just as their phase had ended, but it wasn't likely. In a 4-way, the traffic around you at least had to stop (unless, of course, inattentiveness at any point or trying to 'beat' someone through it). But, you had a better understanding of "if car from my left is cruising at 35mph up to a stop sign, and I just stopped at the stop sign, I may pause momentarily to make sure they, too, are stopping. At a yield situation, you're doing that while driving, and that other car may be thinking they can 'time' the roundabout to get through without stopping, or rather slowing down much, if at all.

Which comes down to the yield sign. It doesn't hold the weight in drivers' eyes as the stop sign does. It's the weak little brother to the stop sign.

Part of the allure of roundabouts is no more signals and the associated costs. But, flashing yellows at all approaches that can be turned to metered during heavy-volume situations would work best in major areas with sensors on the exits to show that the vehicle (or vehicles if a 4-way operating in tandem n/s e/w each) have cleared the roundabout.

But, then we'd be better off with a 4-way stop sign with a smaller geographic footprint.

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 12, 2016, 10:40:27 AM
The uptick in accidents at these roundabouts is proving that drivers aren't driving properly through them. The issue whether the agencies responsible want to have their heads in the sand, or accept that some drivers simply bugger up the system. Both the timid and the brave.

I'm afraid you are putting things up side down: roundabouts are, by design, using controlled aggression to allow traffic to use smaller gaps and so increase throughput. So somewhat aggressive driving should be encouraged, not suppressed - otherwise capacity of roundabout would be reduced below meaningful threshold.
Title: Re: Crash prone 'modern roundabouts'
Post by: Sykotyk on April 13, 2016, 07:14:05 PM
The uptick in accidents at these roundabouts is proving that drivers aren't driving properly through them. The issue whether the agencies responsible want to have their heads in the sand, or accept that some drivers simply bugger up the system. Both the timid and the brave.

I'm afraid you are putting things up side down: roundabouts are, by design, using controlled aggression to allow traffic to use smaller gaps and so increase throughput. So somewhat aggressive driving should be encouraged, not suppressed - otherwise capacity of roundabout would be reduced below meaningful threshold.

I see roundabout as a traffic calming device. Sitting at a light or stop sign can be aggravating. Allowing a vehicle to proceed after only slowing down when there's inconsistent or little side traffic is the positive result of a roundabout.

Putting one in a heavily used intersection does what you say and what I had been pointing to for a while, that it takes away safety in exchange for the 'me first' attitude of drivers trying to be the next one into the circle or to avoid having to come to a full stop.

You've made my point.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on April 14, 2016, 04:16:14 AM
So somewhat aggressive driving should be encouraged, not suppressed - otherwise capacity of roundabout would be reduced below meaningful threshold.
Assertive, not aggressive. There's a big difference.

"the 'me first' attitude of drivers trying to be the next one into the circle or to avoid having to come to a full stop." - oddly we don't see that here: perhaps a cultural difference? But even in France (without the Germanic respect for rules, or the British love of queuing), Spain, etc they do it fine.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 14, 2016, 06:44:19 AM
So somewhat aggressive driving should be encouraged, not suppressed - otherwise capacity of roundabout would be reduced below meaningful threshold.
Assertive, not aggressive. There's a big difference.
Well, big question is what criteria should be used, and what kind of traffic that roundabout gets.
You want to be an assertive person who is going to wait until a gap big enough to keep 2 second intervals both before and after your car? Remember to take a tent and a grill, you will be camping there for a while.
I still think that being able to put a razor between two bumpers is not safe enough? I am with you... But I am evolving....

Once again, problem is with understanding the role of roundabouts. As I say, it's a problem- specific medication, Insulin should not be prescribed for every pneumonia.  Over here roundabouts are positioned as a replacement for heaviest load intersections. You plainly have no choice once you have a roundabout with 20-30k daily traffic count - you need to lower you threshold.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on April 14, 2016, 08:29:29 AM
You want to be an assertive person who is going to wait until a gap big enough to keep 2 second intervals both before and after your car? Remember to take a tent and a grill, you will be camping there for a while.
No I don't. Aggressive is "Poop, poop, out my way!", jumping onto a roundabout and expecting else everyone to make it safe, whereas assertive is "Hello, I'm here!". You don't need to slot into a 4 second gap as
1) The car in front of you won't hit you if you are a couple of yards behind it - you simply move slowly enough to make the gap bigger.
2) The car behind you can also slow down to make the gap bigger
3) Cars are turning off anyway and roundabouts are small enough that the person you are slotting in behind will have left the roundabout not long after you joined (unless turning right).
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Over here roundabouts are positioned as a replacement for heaviest load intersections.
I take it you've never been to the UK! We use them for far busier junctions than the the US. The 3 trunk road dual carriageway arms at the Black Cat Roundabout in Bedfordshire (the 4th arm is the old route of one of the trunk roads) have volumes of 53267 (north), 27784 (west) and 24977 (south), giving total figures of over 53k using that roundabout! OK, that's an outlying excessive case, but 20k-30k is very much par for the course.
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You plainly have no choice once you have a roundabout with 20-30k daily traffic count - you need to lower you threshold.
My nearest roundabout (a mini roundabout) has that sort of volume (and is far from a busy one for Blighty).* The gaps seem to be fine. I can't be bothered to time them, but they are about every two seconds. People just navigate the junction slowly, but assertively.


*3 arms with conservative (count would increase if the points were closer to the roundabout) 2014 figures of 14164, 16818 and 9610, divided by 2 (as each car through the roundabout would be counted twice) = 20296. There's roundabouts in my town with figures of 41899, 31830 (three arms) and 31610, and even they are rather ordinary for the UK. The 3-arm one between the A355 and A40 just north of M40 J2 has more than 43k vehicles per day and never seems to have any problems.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 14, 2016, 10:06:12 AM
English_si, are any of those UK roundabouts that you referenced signalized?  I have heard that at some of the bigger UK roundabouts have signals that are dark for most of the day but cycle during peak times. 
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on April 14, 2016, 01:22:35 PM
The Black Cat was recently, but wasn't when the traffic figures were taken in 2014. I gather the signalisation merely extended the queues.

None of the others are signalised.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 14, 2016, 09:17:43 PM
No I don't. Aggressive is "Poop, poop, out my way!", jumping onto a roundabout and expecting else everyone to make it safe, whereas assertive is "Hello, I'm here!". You don't need to slot into a 4 second gap as
1) The car in front of you won't hit you if you are a couple of yards behind it - you simply move slowly enough to make the gap bigger.
2) The car behind you can also slow down to make the gap bigger
3) Cars are turning off anyway and roundabouts are small enough that the person you are slotting in behind will have left the roundabout not long after you joined (unless turning right).

OK, looks like we have a different definition of "aggressive".
I wouldn't call "Poop, poop, out my way!" aggressive, I would call that "idiot" at best (I am not sure if moderators would tolerate full comment).
Your assumption that the car behind you may slow down a bit _is_ the definition of "somewhat aggressive" for me, as "yield" assumes other driver should not have to touch brake pedal at all.
With that in mind, looks like we're on the same page here, but you're a more seasoned roundabouter...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 15, 2016, 05:34:29 PM
Top 5 Crash-Prone Intersections In Oakland County Include 2 Roundabouts
http://detroit.cbslocal.com/2016/01/05/top-5-dangerous-intersections-in-oakland-county-include-2-roundabouts/

With 116 total crashes, the roundabout at M-5 & Pontiac Trail was the highest crash prone intersection in Oakland County in 2015.  The roundabout was constructed in 2011 and Oakland County drivers have had 4 years to get use to the operation of the roundabout.  Here is 10 years of crash data for this intersection based on SEMCOG crash data:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/M5rb_zpsg1k4muyb.png)

Accidents at M-5 & Pontiac Trail jumped from 54 in 2014 to 116 in 2015.  Haggerty Road which runs parallel to M-5 was reconstructed in 2015 and the roundabout was part of the detour route.  This could help explain the large spike in accidents.
Title: Re: Crash prone 'modern roundabouts'
Post by: Sykotyk on April 17, 2016, 02:00:32 AM
The data should also be based on a percentage of total average daily vehicles that use that intersection. If a big development was built nearby or the roads around it were improved to make it a more preferable route, could see an uptick in traffic and then a corresponding uptick in accidents.

Detour traffic could easily explain the spike for 2015, though, as you have people unfamiliar with a road trying to follow orange blazers back to their original route or destination leaving them less observant at a roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 17, 2016, 08:10:05 AM
It also makes me wonder about the spike between 2011 and 2012.

I remember when I-57 northbound was closed in southern Illinois one, and all traffic was routed through the uncontrolled town square in Benton. Utter misery. A modern roundabout in that case would have helped not one bit; what was needed was traffic cops directing traffic.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 18, 2016, 10:54:33 AM
The data should also be based on a percentage of total average daily vehicles that use that intersection.

I previously listed crash rates for 3x2 and 2x2 multi-lane roundabouts I could find data on.  It’s important to note that many agencies consider a crash rate above 2.0 MEV as “critical”  that warrants further investigation. 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/crashrate_zpsglb8qh4x.png)

The average crash rate for these multi-lane roundabouts was 3.69 MEV.  As a comparison, the average crash rate of Minnesota’s high speed signalized intersections was just 0.8 MEV.  The multi-lane roundabouts have a crash rate over 4X higher than Minnesota’s high speed signalized intersections.
 
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/MNUntitled_zpsnrgwvaog.png)
http://www.dot.state.mn.us/trafficeng/publ/fundamentals/MnDOT_Safety_Handbook_FINAL.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 20, 2016, 02:23:08 PM
I think I'll leave this here ...

http://www.mlive.com/news/ann-arbor/index.ssf/2016/04/road_commission_improves_state.html#incart_river_home

Number of crashes at State and Ellsworth roundabout drops following initial spike

It's getting better.  The idiots are beginning to learn how to navigate it.  And it's not nearly as bad as someone who does not live here makes it out to be.  I have to deal with it every day, and have yet to see an accident.  I don't think anyone has died there, either.

It’s like bragging your favorite baseball team lost 9-2 when the day before they got shut out 14-0.   YAY… good job… only 114 crashes this year. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 21, 2016, 11:38:27 PM
Find out which Livingston County intersections rank highest for number of injuries
http://www.livingstondaily.com/story/news/local/community/livingston-county/2015/11/23/livingston-countys-worst-intersections-crashes/75170418/

Instead of ranking intersections by total crashes, the above article ranks them by the number of injuries.  Lee Road roundabout (pictured below) was No. 2 on the list with 23 injury crashes and 264 total crashes over the past 5 years.  There are literally hundreds of intersections in Livingston County.  If roundabouts are so much safer, how is it that the Lee Road roundabout had the 2nd highest number of injury crashes over the past 5 years? 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/roundabout_double_zps5g1j0uxh.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 22, 2016, 08:00:07 AM
Find out which Livingston County intersections rank highest for number of injuries
http://www.livingstondaily.com/story/news/local/community/livingston-county/2015/11/23/livingston-countys-worst-intersections-crashes/75170418/
You know, it makes some sense to include exact location with a post like this one... here you go:
https://www.google.com/maps/place/Lee+Rd,+Brighton,+MI+48116/@42.5061734,-83.7604905,1154m/data=!3m1!1e3!4m2!3m1!1s0x88234fcef7c20dfb:0x53f7c294fdc4524a

I really wonder if traffic volumes warranted such a complex interchange set to begin with...
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on April 23, 2016, 01:12:12 AM
The engineer who designed that Lee Road dual-roundabout has to be some sort of sadist.  Honestly, it makes the Swindon Magic Roundabout look sensible. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 23, 2016, 09:06:55 AM
Look at how worn the pavement markings are in the below aerial compared to when Lee Road roundabout was freshly painted.  A lot of the safety improvements done to these crash prone roundabouts involve pavement marking tweaks.  All this research is done regarding pavement markings at roundabouts but then we allow the pavement markings to fade to nothing.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/LeeoldUntitled_zpsv14pqthy.png)
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/roundabout_double_zps5g1j0uxh.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 23, 2016, 11:03:33 AM
Look at how worn the pavement markings are in the below aerial compared to when Lee Road roundabout was freshly painted.  A lot of the safety improvements done to these crash prone roundabouts involve pavement marking tweaks.  All this research is done regarding pavement markings at roundabouts but then we allow the pavement markings to fade to nothing.
One thing I heard about roundabouts is that they are oh, so much cheaper to maintain, unlike  traffic lights which consume power and need bulbs change!
Given new LED traffic controls, sounds like we have a $100 solution for an $1 problem..

As for the intersection in question, with total of 5 roundabouts... I only wonder how much was the kickback.
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on April 23, 2016, 04:34:56 PM
One thing I heard about roundabouts is that they are oh, so much cheaper to maintain, unlike  traffic lights which consume power and need bulbs change!
Given new LED traffic controls, sounds like we have a $100 solution for an $1 problem..

The whole "maintenance cost" claim with signals vs. roundabouts was a load of hooey even before LEDs became commonplace in signals.  The usually cited savings figure is $5000/year, which means that for a $250,000 signal vs. a $2,500,000 roundabout, you're looking at 450 years before one reaches the break even point, and I doubt the roundabout is going to have a design life of 450 years.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 23, 2016, 06:37:48 PM
One thing I heard about roundabouts is that they are oh, so much cheaper to maintain, unlike  traffic lights which consume power and need bulbs change!
Given new LED traffic controls, sounds like we have a $100 solution for an $1 problem..

The whole "maintenance cost" claim with signals vs. roundabouts was a load of hooey even before LEDs became commonplace in signals.  The usually cited savings figure is $5000/year, which means that for a $250,000 signal vs. a $2,500,000 roundabout, you're looking at 450 years before one reaches the break even point, and I doubt the roundabout is going to have a design life of 450 years.

The price of intersection modification is highly subjective. Not all roundabouts cost $2.5mil, and not all signals cost $250k.

The best example might be freeway/service road interchanges. The cost of widening a bridge over a freeway costs a lot more than installing roundabouts at the ramp termini.

FWIW, WSDOT cites an average annual signal maintenance cost of $8k: http://goo.gl/q3Q6Kh
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 25, 2016, 05:27:25 PM
DOT eyes crash-heavy roundabout on Eau Claire's south side

http://www.leadertelegram.com/News/Front-Page/2016/03/30/Crash-heavy-roundabout-eyed.html

The article states there has been 26 crashes at the roundabout between 2011 and 2015.  That equates to about 5 crashes a year.  That to me is not "crash heavy" especially considering the amount of traffic volume US 53 carries.  This is a multi-lane roundabout but it's a simpler 2x1 variety.  I guess they plan on adding rumble strips before the roundabout to slow traffic down and also mound the center island to make it more visible to approaching motorists.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 27, 2016, 01:18:24 PM
A 2016 report by the UMD National Transportation Center analyzed the safety of Arizona roundabouts.   Of the double-lane roundabouts analyzed there was a 68% increase in the average rate of accidents per million vehicles.  Also, there was an 8% decrease in the average rate of injuries per year per million vehicles.  The report came to the following conclusion:

Quote
In conclusion, single-lane roundabouts improved the safety of intersections. However, double-lane roundabouts reduced the safety of intersections. A decision needs to be made as to either remove double-lane roundabouts or find solutions on how to make these roundabouts safe, such as making geometric improvements or educating the public on how to use them.

http://ntc.umd.edu/sites/default/files/documents/Publications/NTC2015-SU-R-3_Mamlouk.pdf

Many multi-lane roundabouts in this thread (specifically 2x2 and higher) have seen large increases in total accidents with a lackluster reduction in injury accidents.  This 2016 study of multi-lane roundabouts in Arizona match this performance.
Title: Re: Crash prone 'modern roundabouts'
Post by: JMAN_WiS&S on May 02, 2016, 12:36:31 PM
DOT eyes crash-heavy roundabout on Eau Claire's south side

http://www.leadertelegram.com/News/Front-Page/2016/03/30/Crash-heavy-roundabout-eyed.html

The article states there has been 26 crashes at the roundabout between 2011 and 2015.  That equates to about 5 crashes a year.  That to me is not "crash heavy" especially considering the amount of traffic volume US 53 carries.  This is a multi-lane roundabout but it's a simpler 2x1 variety.  I guess they plan on adding rumble strips before the roundabout to slow traffic down and also mound the center island to make it more visible to approaching motorists.
I mentioned this a few pages back and it seems people ignored it as nobody replied and continued other replies.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 02, 2016, 02:09:55 PM
DOT eyes crash-heavy roundabout on Eau Claire's south side

http://www.leadertelegram.com/News/Front-Page/2016/03/30/Crash-heavy-roundabout-eyed.html

The article states there has been 26 crashes at the roundabout between 2011 and 2015.  That equates to about 5 crashes a year.  That to me is not "crash heavy" especially considering the amount of traffic volume US 53 carries.  This is a multi-lane roundabout but it's a simpler 2x1 variety.  I guess they plan on adding rumble strips before the roundabout to slow traffic down and also mound the center island to make it more visible to approaching motorists.
I mentioned this a few pages back and it seems people ignored it as nobody replied and continued other replies.

I vaguely remember someone bringing up the US 53 Eau Claire roundabout but I didn’t see your earlier post until now.  My point is I don’t believe there is much of a crash problem at that Eau Claire roundabout (despite what the headline of the article leads you to believe).  I’ve been criticized for pointing out high crash rate roundabouts throughout this thread but I’ll be the first to defend a roundabout that is working well.  The multi-lane roundabout in Eau Claire averages about 5 crashes a year.  That doesn't sound bad at all.
Title: Re: Crash prone 'modern roundabouts'
Post by: JMAN_WiS&S on May 04, 2016, 12:12:18 PM
DOT eyes crash-heavy roundabout on Eau Claire's south side

http://www.leadertelegram.com/News/Front-Page/2016/03/30/Crash-heavy-roundabout-eyed.html

The article states there has been 26 crashes at the roundabout between 2011 and 2015.  That equates to about 5 crashes a year.  That to me is not "crash heavy" especially considering the amount of traffic volume US 53 carries.  This is a multi-lane roundabout but it's a simpler 2x1 variety.  I guess they plan on adding rumble strips before the roundabout to slow traffic down and also mound the center island to make it more visible to approaching motorists.
I mentioned this a few pages back and it seems people ignored it as nobody replied and continued other replies.

I vaguely remember someone bringing up the US 53 Eau Claire roundabout but I didn’t see your earlier post until now.  My point is I don’t believe there is much of a crash problem at that Eau Claire roundabout (despite what the headline of the article leads you to believe).  I’ve been criticized for pointing out high crash rate roundabouts throughout this thread but I’ll be the first to defend a roundabout that is working well.  The multi-lane roundabout in Eau Claire averages about 5 crashes a year.  That doesn't sound bad at all.
The only issue is people going into it too quickly going SB. I'm quite suprised eau claire only has a couple roundabouts and not more, as it seems they are popular elsewhere in the state.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 04, 2016, 01:26:40 PM
Looking at an aerial of the US 53 Eau Claire roundabout it’s not surprising there aren’t many crashes.  Scully Drive services a Gander Mountain (a big store, but that’s the only traffic being generated) and Old Town Hall Road has some small businesses along it.  There just isn’t much conflict at this roundabout as the majority of traffic is continuing straight on US 53.

https://www.google.com/maps/@44.7643843,-91.4200398,787m/data=!3m1!1e3
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 04, 2016, 01:49:30 PM
JMAN, do you have any word on how many crashes there have been at the roundabout at Highway 124 and Business 29 outside Chippewa Falls?  It was constructed around 2009 and replaced a full-blown interchange.  There are slip lanes for all legs which should reduce the conflicts inside the roundabout itself.  Any experience with this roundabout?

https://www.google.com/maps/@44.9210902,-91.3808932,259m/data=!3m1!1e3
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on May 04, 2016, 01:50:43 PM
Looking at an aerial of the US 53 Eau Claire roundabout it’s not surprising there aren’t many crashes.  Scully Drive services a Gander Mountain (a big store, but that’s the only traffic being generated) and Old Town Hall Road has some small businesses along it.  There just isn’t much conflict at this roundabout as the majority of traffic is continuing straight on US 53.

https://www.google.com/maps/@44.7643843,-91.4200398,787m/data=!3m1!1e3


On a side note, interesting stripping for the off ramp there, even though there's no left turn movement.  Usually those lanes would be stripped to 'guide' people into a right turn.  Looking back on the GSV I can understand it during construction...7 years ago.   But no reason not to have revised it since.

The on-ramp isn't much better, as if it was meant for traffic to turn left onto it.

https://goo.gl/maps/qybfKukfA992

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 04, 2016, 02:08:09 PM
Looking at an aerial of the US 53 Eau Claire roundabout it’s not surprising there aren’t many crashes.  Scully Drive services a Gander Mountain (a big store, but that’s the only traffic being generated) and Old Town Hall Road has some small businesses along it.  There just isn’t much conflict at this roundabout as the majority of traffic is continuing straight on US 53.

https://www.google.com/maps/@44.7643843,-91.4200398,787m/data=!3m1!1e3


On a side note, interesting stripping for the off ramp there, even though there's no left turn movement.  Usually those lanes would be stripped to 'guide' people into a right turn.  Looking back on the GSV I can understand it during construction...7 years ago.   But no reason not to have revised it since.

The on-ramp isn't much better, as if it was meant for traffic to turn left onto it.

https://goo.gl/maps/qybfKukfA992

I can understand the off-ramp. Sometimes, if there isn't sufficient merge area, it's better to have a right-angle "yield" (though I don't agree with the stop sign seen here -- something like this is what I prefer: https://goo.gl/UTjZjj).

The on-ramp though...it's not something I haven't seen before, but it's certainly not something I prefer.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on May 04, 2016, 02:55:08 PM
Looking at an aerial of the US 53 Eau Claire roundabout it’s not surprising there aren’t many crashes.  Scully Drive services a Gander Mountain (a big store, but that’s the only traffic being generated) and Old Town Hall Road has some small businesses along it.  There just isn’t much conflict at this roundabout as the majority of traffic is continuing straight on US 53.

https://www.google.com/maps/@44.7643843,-91.4200398,787m/data=!3m1!1e3


On a side note, interesting stripping for the off ramp there, even though there's no left turn movement.  Usually those lanes would be stripped to 'guide' people into a right turn.  Looking back on the GSV I can understand it during construction...7 years ago.   But no reason not to have revised it since.

The on-ramp isn't much better, as if it was meant for traffic to turn left onto it.

https://goo.gl/maps/qybfKukfA992

I can understand the off-ramp. Sometimes, if there isn't sufficient merge area, it's better to have a right-angle "yield" (though I don't agree with the stop sign seen here -- something like this is what I prefer: https://goo.gl/UTjZjj).

The on-ramp though...it's not something I haven't seen before, but it's certainly not something I prefer.

I was referring to the fact the left yellow line goes straight into the intersection, with a straight stop bar to boot.  At least the stop bar is angled towards the right of the lane, but in reality the whole stop bar should be angled, with the yellow line curving to the right as well.
Title: Re: Crash prone 'modern roundabouts'
Post by: JMAN_WiS&S on May 05, 2016, 12:21:32 PM
JMAN, do you have any word on how many crashes there have been at the roundabout at Highway 124 and Business 29 outside Chippewa Falls?  It was constructed around 2009 and replaced a full-blown interchange.  There are slip lanes for all legs which should reduce the conflicts inside the roundabout itself.  Any experience with this roundabout?

https://www.google.com/maps/@44.9210902,-91.3808932,259m/data=!3m1!1e3
I have driven and ridden through that one before, not sure on crash stats, the intersection is fairly self explanatory. I find it cool how you can still see row grading where the old sb-> eb flyover ramp used to be.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 26, 2016, 03:05:42 PM
The infamous 50/60 Lakeville roundabout has had another crash recently.  This time a women and 3 of her kids had to be extricated from an Escalade after it flipped over on it's side.  This is the same roundabout that saw 44 crashes in the first two months of operation back in 2015:

http://sunthisweek.com/2016/04/15/woman-children-pulled-from-lakeville-rollover-crash/
Title: Re: Crash prone 'modern roundabouts'
Post by: dvferyance on May 27, 2016, 02:13:39 PM
Simple answer the roundabouts on Moorland Rd in New Berlin by I-43. They could be the worst in the country.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 27, 2016, 03:34:26 PM
^Here is a dated article discussing the Moorland Road roundabouts at I-43.  At that time (2008 data) the Moorland Road/Rock Ridge roundabout had the highest crash rate of any other major intersection in New Berlin.  The article goes on to state that the number of injury accidents is way down.  This is a total fabrication.  What the article is looking at is the severity of accidents at the roundabout and not total injury accidents…. 

Quote
While there are more accidents at the roundabout, the number of injury accidents is way down… Of the 44 reportable and nonreportable accidents at Rock Ridge/Moorland in a 15-month period from the end of 2007 through January 2009, only three were injury accidents, he said. That is far lower than the seven out of 13 accidents that were injury accidents at the Rock Ridge and Moorland intersection with traffic lights, Rieder said. Those 13 accidents happened over a period of seven years.
http://www.newberlinnow.com/news/56607067.html

Just look at the data the article cites:
Before roundabout (7 years of crash data):   13 total crashes; 7 injury crashes 
After roundabout (15-months of crash data):  44 total crashes; 3 injury crashes

How can this article claim that the number of injury accidents is way down?  We are comparing 15-months of post-roundabout crash data to 7 years of pre-roundabout crash data.  If you actually average it out by injury crashes per year, injury crashes have more than doubled (going from 1 injury crashes/year before the roundabout to 2.4 injury crashes/year after the roundabout).
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 27, 2016, 04:07:02 PM
^^

Not sure why any of that matters today. No doubt they may be stretching the numbers a little, but the numbers are still old and irrelevant.. I'd love to see some new data on those roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 27, 2016, 04:54:34 PM
For the record, I don’t believe the Moorland Road roundabouts are performing that badly.  A crash rate of 2.0 MEV (which is cited in the article) is right on the cusp of being considered a satisfactory crash rate.  There are roundabouts with crash rates much higher than the Moorland Road roundabouts that would concern me more.  Interchange roundabouts, for whatever reason, seem to have lower crash rates than non-interchange roundabouts and that could explain why Moorland Road roundabouts are performing OK.  I definitely wouldn’t consider it the worst in the country. 

All that said, that New Berlin article is a powder puff propaganda piece by trying to claim that injury accidents are WAY down at the roundabout. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 27, 2016, 08:15:17 PM
For the record, I don’t believe the Moorland Road roundabouts are performing that badly.  A crash rate of 2.0 MEV (which is cited in the article) is right on the cusp of being considered a satisfactory crash rate.  There are roundabouts with crash rates much higher than the Moorland Road roundabouts that would concern me more.  Interchange roundabouts, for whatever reason, seem to have lower crash rates than non-interchange roundabouts and that could explain why Moorland Road roundabouts are performing OK.  I definitely wouldn’t consider it the worst in the country.

There's also the point that the northern roundabout is exceptionally large, much larger than any modern roundabout I've seen before. I'm sure that has something to do with it as well (visibility being one of them).

All that said, that New Berlin article is a powder puff propaganda piece by trying to claim that injury accidents are WAY down at the roundabout.

I would guess that the author didn't quite understand the topic.
Title: Re: Crash prone 'modern roundabouts'
Post by: dvferyance on May 28, 2016, 09:44:52 AM
For the record, I don’t believe the Moorland Road roundabouts are performing that badly.  A crash rate of 2.0 MEV (which is cited in the article) is right on the cusp of being considered a satisfactory crash rate.  There are roundabouts with crash rates much higher than the Moorland Road roundabouts that would concern me more.  Interchange roundabouts, for whatever reason, seem to have lower crash rates than non-interchange roundabouts and that could explain why Moorland Road roundabouts are performing OK.  I definitely wouldn’t consider it the worst in the country. 

All that said, that New Berlin article is a powder puff propaganda piece by trying to claim that injury accidents are WAY down at the roundabout.
There are still problems no doubt. Some mornings traffic backs up on to I-43 I have seen this not once but several times. The SB Moorland turn to Rock Ridge is a nightmare and very confusing. I had a very close call there not too long ago. What bothers me the most is nobody in New Berlin wanted it the DOT should have respected the wishes of the people. After all it's us the residents of New Berlin that have to deal with it not the DOT engineers that were pushing for it. While I am unaware of the crash rates now there I can say there is getting to be more traffic than what they can handle. And when more development kicks in to the south watch out.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 07, 2016, 10:59:59 PM
A local morning show spent a half hour today talking about the crash prone roundabouts in metro Detroit. 

http://www.mediafire.com/download/w2h1dd0n8xey7de/06072016podcastpart1_cutted2.mp3
Title: Re: Crash prone 'modern roundabouts'
Post by: AlexandriaVA on June 07, 2016, 11:23:23 PM
But were they modern? I was going to chalk the accidents up to Midwestern simpletons, but if the fine folks of Indiana can figure out roundabouts, what's holding back Michiganers?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 08, 2016, 07:59:54 AM
^A similar naïve comment was made early on in this thread:
Speaks more to the (in)flexibility of Michigan drivers than it does any inherent safety risk with roundabouts.  New roundabouts elsewhere have seen major drops in the number of crashes.

Crash prone roundabouts throughout the country have been discussed on this thread.  The roundabout at 116th Street & Keystone in Carmel, Indiana has a very high crash rate.  Keep in mind the majority of Carmel roundabouts are either single lane or the simplified 1x2 variety.  The few complex 2x2 roundabouts Carmel do have high crash rates.
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/crashrate_zpsglb8qh4x.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: nhoward45 on June 09, 2016, 10:23:07 AM
The term "roundabout" is merely rebranding for the older term, traffic circle.   These were nuisances and traffic hazards in the 1940s and 1950s, and in many areas were replaced with grade separated interchanges or bypassed with freeways.  Traffic circles may be OK in a low speed residential environment, but are dangerous in any heavily trafficked area.  Traffic signals may slow down vehicle flow, but are less risky than traffic circles.  Rebranding changes nothing.  A garbage man is a garbage man, even if rebranded a sanitary engineer.

This is not a regional issue either.  The list of high risk traffic circles includes Southern, Western, Northeastern, and Canadian locations as well as Midwestern ones.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 09, 2016, 11:20:48 AM
The term "roundabout" is merely rebranding for the older term, traffic circle.   These were nuisances and traffic hazards in the 1940s and 1950s, and in many areas were replaced with grade separated interchanges or bypassed with freeways.  Traffic circles may be OK in a low speed residential environment, but are dangerous in any heavily trafficked area.  Traffic signals may slow down vehicle flow, but are less risky than traffic circles.  Rebranding changes nothing.  A garbage man is a garbage man, even if rebranded a sanitary engineer.

This is not a regional issue either.  The list of high risk traffic circles includes Southern, Western, Northeastern, and Canadian locations as well as Midwestern ones.

Let me know when you're done spouting nonsense. Not a single thing you just wrote is even remotely accurate.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 09, 2016, 01:30:31 PM
The term "roundabout" is merely rebranding for the older term, traffic circle.   These were nuisances and traffic hazards in the 1940s and 1950s, and in many areas were replaced with grade separated interchanges or bypassed with freeways.  Traffic circles may be OK in a low speed residential environment, but are dangerous in any heavily trafficked area.  Traffic signals may slow down vehicle flow, but are less risky than traffic circles.  Rebranding changes nothing.  A garbage man is a garbage man, even if rebranded a sanitary engineer.

This is not a regional issue either.  The list of high risk traffic circles includes Southern, Western, Northeastern, and Canadian locations as well as Midwestern ones.

Let me know when you're done spouting nonsense. Not a single thing you just wrote is even remotely accurate.

Since you, nhoward45, appear to be a new member, let's make this clearer for you.  A modern roundabout must meet specific design criteria, the most important two being flared approaches and yield upon entry.  These two criteria were certainly not universally implemented in the 1940s and 1950s.

And risk can be analyzed in two ways:  total crashes or severity of crashes.  Roundabouts tend to increase the number of total crashes but diminish the severity of those crashes.  This topic is actually sort of about how good of a job they do at this.  What it looks like, offhand, is that you just jumped into page 19 of a discussion without reading the rest of it.
Title: Re: Crash prone 'modern roundabouts'
Post by: nhoward45 on June 09, 2016, 01:31:26 PM
Please explain the difference between traffic circles or roundabouts.

If traffic circles/roundabouts were such a great idea, please explain why highway engineers in last four decades of the 20th Century replaced or bypassed them. 

In Texas, the Harry Hines traffic circle in Dallas was replaced by grade separation at the intersection.  Traffic circles in Fort Worth and Lubbock were bypassed through the construction of Interstate highways. 
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on June 09, 2016, 01:48:53 PM
Somebody forgot to do their homework.

http://safety.fhwa.dot.gov/intersection/innovative/roundabouts/
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 09, 2016, 02:27:48 PM
Please explain the difference between traffic circles or roundabouts.
There's a Google for that. (http://bfy.tw/6Bm5)

Quote
If traffic circles/roundabouts were such a great idea, please explain why highway engineers in last four decades of the 20th Century replaced or bypassed them.
Because older-style traffic circles had safety issues.  As traffic counts increased, these problems increased in significance.

Quote
Traffic circles in Fort Worth and Lubbock were bypassed through the construction of Interstate highways.
Bypassed or replaced?  If they were bypassed, then that would mean the traffic circles are still there.  If they were replaced, then...well, obviously, since Interstates are freeways, and freeways don't have cross-traffic.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 09, 2016, 02:51:39 PM
Somebody forgot to do their homework.

http://safety.fhwa.dot.gov/intersection/innovative/roundabouts/

I love to compare roundabouts to an insulin: can be a lifesaver, but needs to be used properly - and definitely not an omnicure.
But unlike insulin, roundabouts are advertised as such...
Title: Re: Crash prone 'modern roundabouts'
Post by: US 81 on June 10, 2016, 05:14:19 PM

...
Quote
Traffic circles in Fort Worth and Lubbock were bypassed through the construction of Interstate highways.
Bypassed or replaced?  If they were bypassed, then that would mean the traffic circles are still there.  If they were replaced, then...well, obviously, since Interstates are freeways, and freeways don't have cross-traffic.

"Bypassed" is correct for Ft. Worth. Lubbock's was replaced during construction of I-27.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 13, 2016, 09:20:51 PM
Bo and Luke Duke were driving around Romania. 

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 14, 2016, 10:44:26 PM
I'm not sure whether or not this study has been linked here, or not (I don't believe it has); for the sake of the following comment, let's presume it has not been.

Back in 2002, several FHWA employees visited Sweden, Germany, the Netherlands, and the UK to study different traffic signal/control schemes practised in each of those countries. One of the biggest takeaways from this visit was the roundabout. Though roundabouts had already been built in the US, there hadn't been much official documentation on them (hence why it took until 2009 to develop marking and design standards). Throughout the document, the FHWA employees note that roundabouts are effective at reducing the severity of collisions, but not the number of collisions:

Quote from: Chapter 9, summary
4. Promote roundabouts as alternatives to signalized intersections as a way to manage the consequences of collisions (severity versus frequency).
Quote from: Chapter 2, Sweden
...The primary focus is on crash severity, not frequency....On the basis of this principle, SNRA has converted signalized intersections to roundabouts, recognizing that the frequency of total accidents may increase, but the severity of those accidents may be greatly reduced.
Quote from: Chapter 3, Sweden
When high-accident locations have been identified, progressive solutions are developed...In some cases, where accident severity is high, Sweden has removed traffic signals and replaced them with roundabouts, recognizing that overall accident rates may increase and line-of-sight may be degraded, but the rate of severe (fatal and injurious) accidents will decrease...In urban areas, unsignalized roundabouts can have a negative systemwide effect because it is difficult to control and manage platooning and traffic progression.

And, on severity alone:

Quote from: Chapter 5, the Netherlands
The turbo roundabout...is used in the Netherlands to eliminate weaving conflicts found in standard multilane roundabouts...This low-speed configuration also has been found to allow a higher capacity than the standard two-lane roundabout. While a standard roundabout has 16 potential conflict points, the turbo roundabout has 10. In either case, the conflict points are low speed, and the resulting accidents are typically less severe than those at signalized intersections (Figure 5-5).

There are additional comments -- you can read the study here: http://goo.gl/6MQq2Z

I do wonder why initial studies were so focused on demonstrating the reduction of collisions, versus the severity. I know both were part of the studies, but at least as far as I can tell, the biggest plus of roundabouts is the reduction in severity, not any sort of reduction of overall collisions.

I don't doubt the benefits of the roundabout. It's pretty obvious that roundabouts reduce the severity of collisions, but, the sheer number of collisions at a given intersection doesn't seem to have any connection to the geometric design of said intersection. There are some signals with a lot of collisions, and some roundabouts with a lot of collisions. Equally, there are some signals with very few collisions, and some roundabouts with very few collisions.

tl;dr: the primary benefit of the roundabout is reduced severity.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 14, 2016, 11:01:08 PM

I do wonder why initial studies were so focused on demonstrating the reduction of collisions, versus the severity. I know both were part of the studies, but at least as far as I can tell, the biggest plus of roundabouts is the reduction in severity, not any sort of reduction of overall collisions.
[...]
tl;dr: the primary benefit of the roundabout is reduced severity.

My strong impression is that primary advantage of roundabouts in US is ability to get more money into construction contracts, and who cares what bullshit is used to justify that to the crowd.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 14, 2016, 11:23:40 PM

I do wonder why initial studies were so focused on demonstrating the reduction of collisions, versus the severity. I know both were part of the studies, but at least as far as I can tell, the biggest plus of roundabouts is the reduction in severity, not any sort of reduction of overall collisions.
[...]
tl;dr: the primary benefit of the roundabout is reduced severity.

My strong impression is that primary advantage of roundabouts in US is ability to get more money into construction contracts, and who cares what bullshit is used to justify that to the crowd.

I'm not usually convinced by conspiracies....this is not an exception.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 14, 2016, 11:47:39 PM

I do wonder why initial studies were so focused on demonstrating the reduction of collisions, versus the severity. I know both were part of the studies, but at least as far as I can tell, the biggest plus of roundabouts is the reduction in severity, not any sort of reduction of overall collisions.
[...]
tl;dr: the primary benefit of the roundabout is reduced severity.

My strong impression is that primary advantage of roundabouts in US is ability to get more money into construction contracts, and who cares what bullshit is used to justify that to the crowd.

I'm not usually convinced by conspiracies....this is not an exception.

Not a conspiracy, just plain old corruption. Which is just business as usual.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 15, 2016, 12:23:04 AM

I do wonder why initial studies were so focused on demonstrating the reduction of collisions, versus the severity. I know both were part of the studies, but at least as far as I can tell, the biggest plus of roundabouts is the reduction in severity, not any sort of reduction of overall collisions.
[...]
tl;dr: the primary benefit of the roundabout is reduced severity.

My strong impression is that primary advantage of roundabouts in US is ability to get more money into construction contracts, and who cares what bullshit is used to justify that to the crowd.

I'm not usually convinced by conspiracies....this is not an exception.

Not a conspiracy, just plain old corruption. Which is just business as usual.

Right...corruption. Got it m8.

Anyone here interested in discussing roundabouts?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 15, 2016, 12:26:41 AM

Right...corruption. Got it m8.

Anyone here interested in discussing roundabouts?
Sure. Are there any estimates on demolition costs for those?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 15, 2016, 12:38:25 AM

Right...corruption. Got it m8.

Anyone here interested in discussing roundabouts?

Sure. Are there any estimates on demolition costs for those?

Never heard of such a thing. Maybe tradephoric has some idea.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 15, 2016, 12:54:26 AM

Right...corruption. Got it m8.

Anyone here interested in discussing roundabouts?

Sure. Are there any estimates on demolition costs for those?

Never heard of such a thing. Maybe tradephoric has some idea.

Which is actually a big problem of those roundabouts. There is no clear understanding why they should be built; once studies showing how great those are turn out irrelevant, there is a different argument. There is no understanding of when roundabouts actually work best; I didn't see realistic estimates of throughput. There is no understanding of future costs - such as demolition. 
Two things are known for sure: that they must be built, and how much they cost. I can see two reasons for that:  corruption in financing construction and old good stupidity.
If I have to choose which one is more realistic, I definitely choose both.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 15, 2016, 02:08:54 AM

Right...corruption. Got it m8.

Anyone here interested in discussing roundabouts?

Sure. Are there any estimates on demolition costs for those?

Never heard of such a thing. Maybe tradephoric has some idea.

Which is actually a big problem of those roundabouts. There is no clear understanding why they should be built; once studies showing how great those are turn out irrelevant, there is a different argument. There is no understanding of when roundabouts actually work best; I didn't see realistic estimates of throughput. There is no understanding of future costs - such as demolition. 
Two things are known for sure: that they must be built, and how much they cost. I can see two reasons for that:  corruption in financing construction and old good stupidity.
If I have to choose which one is more realistic, I definitely choose both.

Whoa whoa whoa, slow down partner. You asked me about demolition costs ... I told you I didn't know ... then you respond with some rambling, incoherent paragraph, darting from point to point, apparently at random, only to arrive at an indecipherable conclusion ("If I have to choose which one...I definitely choose both.").

I've never had to ask someone to do this before, but...please re-write your post. I want to be able to reply with a decent response, but I simply don't understand what you're saying.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on June 15, 2016, 04:27:16 AM
I've never had to ask someone to do this before, but...please re-write your post. I want to be able to reply with a decent response, but I simply don't understand what you're saying.
Seems to be saying that the crab people thrust roundabouts on us, without telling us the costs of demolishing them when we inevitably (and kalvado does think it's inevitable for some reason) see through the crab people's arguments that we need them and so that's a hidden cost of building them - the cost of demolishing the blighters when we find them shite.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 15, 2016, 08:07:46 AM

Whoa whoa whoa, slow down partner. You asked me about demolition costs ... I told you I didn't know ... then you respond with some rambling, incoherent paragraph, darting from point to point, apparently at random, only to arrive at an indecipherable conclusion ("If I have to choose which one...I definitely choose both.").

I've never had to ask someone to do this before, but...please re-write your post. I want to be able to reply with a decent response, but I simply don't understand what you're saying.
[/quote]

OK, same thing in a more formalized basis.

1. Current altitude to roundabouts (RA) among traffic engineers is based on faith, not on fact.
1a. When initial research on how great RA are proved wrong, a new set of "they are still great!" texts emerged.
1b. There are still no serious research regarding applicability of RA in terms of handleable traffic volumes, types of roads where RA can work best (2x2 lane discussion in this thread)  etc.
1c. Some official recommendation pushing RA as first choice are reinforcing religious altitude
1d. No understanding of full lifecycle costs; despite declared low-maintenance, things like re-training snow plow drivers and improvising and relocating pedestrian crosswalks after construction "because we're on learning curve", as well as costs of demolition of messy structure are not taken into account on decision making stage.
1e. I really doubt that organization, which is extremely busy with defining types of fonts to be used on signs, has enough technical expertise to develop understanding such complex system.

2. Cost of building roundabout is significant and mostly out of public control since there is little basis for comparison.
2a. That attracts construction companies, since MONEY. Visibly same structure can cost $0.5M and $2M within 20 miles radius (local example)
2b. That attracts politicians, since that allows to flow money in a non-transparent way.

Harsh? definitely. True? At least partially.   
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on June 15, 2016, 08:17:34 AM

2. Cost of building roundabout is significant and mostly out of public control since there is little basis for comparison.
2a. That attracts construction companies, since MONEY. Visibly same structure can cost $0.5M and $2M within 20 miles radius (local example)
2b. That attracts politicians, since that allows to flow money in a non-transparent way.

None of this is unique to roundabouts.  An intersection replacement costs can vary widely, depending on what needs to be done.  And there's a ton of basis of comparison...they know how much land they need, they know the various costs.  They can do an analysis of the cost of an intersection vs. the cost of a roundabout, along with ongoing maintenance and electricity costs.  All of this is pretty typical stuff.

Many states puts these projects out to bid, and there's plenty of contractors out there willing to bid on the projects.  Again, much of this can be found online. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 15, 2016, 08:36:25 AM

2. Cost of building roundabout is significant and mostly out of public control since there is little basis for comparison.
2a. That attracts construction companies, since MONEY. Visibly same structure can cost $0.5M and $2M within 20 miles radius (local example)
2b. That attracts politicians, since that allows to flow money in a non-transparent way.

None of this is unique to roundabouts.  An intersection replacement costs can vary widely, depending on what needs to be done.  And there's a ton of basis of comparison...they know how much land they need, they know the various costs.  They can do an analysis of the cost of an intersection vs. the cost of a roundabout, along with ongoing maintenance and electricity costs.  All of this is pretty typical stuff.

Many states puts these projects out to bid, and there's plenty of contractors out there willing to bid on the projects.  Again, much of this can be found online.

NYSDOT tend to publish lump sum costs and nothing more than that. As for bidding... This is something what is likely to lend our governor either in jail or in the White house in near future. You just have to do it right!
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on June 15, 2016, 09:20:31 AM

2. Cost of building roundabout is significant and mostly out of public control since there is little basis for comparison.
2a. That attracts construction companies, since MONEY. Visibly same structure can cost $0.5M and $2M within 20 miles radius (local example)
2b. That attracts politicians, since that allows to flow money in a non-transparent way.

None of this is unique to roundabouts.  An intersection replacement costs can vary widely, depending on what needs to be done.  And there's a ton of basis of comparison...they know how much land they need, they know the various costs.  They can do an analysis of the cost of an intersection vs. the cost of a roundabout, along with ongoing maintenance and electricity costs.  All of this is pretty typical stuff.

Many states puts these projects out to bid, and there's plenty of contractors out there willing to bid on the projects.  Again, much of this can be found online.

NYSDOT tend to publish lump sum costs and nothing more than that. As for bidding... This is something what is likely to lend our governor either in jail or in the White house in near future. You just have to do it right!


BidX is your friend when it comes to all things bidded on about roads.  If you're maintain a thought process that includes everything the state does is evil and corrupt though, it's not going to be of any help.  There are rules that are generally followed, with few exceptions.

For NY: https://www.bidx.com/ny/main
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 15, 2016, 10:14:55 AM
It's pretty obvious that roundabouts reduce the severity of collisions
The severity index is simply a weighted average of fatal, injury, and PDO crashes.   Here is the formula from the FHWA:

Severity Index = (12 * F + 3 * I + 1 * PDO) / N
Where: 
F=total number of fatal crashes
I =total number of injury crashes
N = total number of crashes

Let’s figure out the severity index of a multi-lane roundabout with the following stats:
AADT=40,000
Fatal crashes = 0
Injury crashes = 10
PDO crashes = 90
Total crashes = 100
Severity Index = (12 * 0 + 3 * 10 + 1 * 90) / 100  =  1.2

Now what is the severity index of a signalized intersection with the following stats:
AADT=40,000
Fatal crashes = 0
Injury crashes = 10
PDO crashes = 30
Total crashes = 40
Severity Index = (12 * 0 + 3 * 10 + 1 * 30) / 40 = 1.5

Sure, the roundabout had a lower severity of crashes but does that make it safer?  You have to consider the frequency of crashes to determine if the reduction in severity is actually leading to fewer injury crashes.  Stating that “roundabouts reduce the severity of crashes”  is just a clever way to mask the fact that roundabouts aren’t always safer (IE. some 2x2 multi-lane roundabouts). 
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 15, 2016, 10:43:08 AM

BidX is your friend when it comes to all things bidded on about roads.  If you're maintain a thought process that includes everything the state does is evil and corrupt though, it's not going to be of any help.  There are rules that are generally followed, with few exceptions.

For NY: https://www.bidx.com/ny/main
Thank you for the reference, will look at it later...
As about  state=evil.. not difficult in a state which lost couple of top leaders to federal prisons in a past year and governor shedding all his friends in attempt not to join the gang. But if you will, the root cause is unclear technical justification strongly supported at political level. I don't remember that level of support for SPUI, for example - probably because advantages become clear after single-digit drives through one of those.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 15, 2016, 06:32:31 PM
Stating that “roundabouts reduce the severity of crashes”  is just a clever way to mask the fact that roundabouts aren’t always safer (IE. some 2x2 multi-lane roundabouts).

There is no perfect, winner-take-all design. There are examples of every type of intersection with both a lot, and very few collisions. I specified this in my original post:

I don't doubt the benefits of the roundabout. It's pretty obvious that roundabouts reduce the severity of collisions, but the sheer number of collisions at a given intersection doesn't seem to have any connection to the geometric design of said intersection. There are some signals with a lot of collisions, and some roundabouts with a lot of collisions. Equally, there are some signals with very few collisions, and some roundabouts with very few collisions.

My point was simply that roundabouts, as a whole, have a better severity record. There are inexplicable exceptions, of course, but, they're exceptions.

And to be clear, to tie this back into your original post way back yonder, there are certainly some discrepancies in the FHWA's original studies. But, roundabouts are still pretty damn good at protecting from severe, life-threatening injuries, simply because their design makes such collisions rather difficult (unless of course you drive straight over the middle, like in Carmel, IN).

My post (https://www.aaroads.com/forum/index.php?topic=15546.msg2151711#msg2151711), at the top of this page, was to bring up what I thought was an interesting discrepancy (the FHWA knew full well that roundabouts don't always decrease collisions, but they still heavily marketed roundabouts with that tagline anyway).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 15, 2016, 07:42:43 PM

My post (https://www.aaroads.com/forum/index.php?topic=15546.msg2151711#msg2151711), at the top of this page, was to bring up what I thought was an interesting discrepancy (the FHWA knew full well that roundabouts don't always decrease collisions, but they still heavily marketed roundabouts with that tagline anyway).

And even reduced severity is a poor metrics. If that was the ultimate one, reducing speed limit on interstates to 25 MPH should be a no-brainer.
\
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 16, 2016, 12:40:58 AM

My post (https://www.aaroads.com/forum/index.php?topic=15546.msg2151711#msg2151711), at the top of this page, was to bring up what I thought was an interesting discrepancy (the FHWA knew full well that roundabouts don't always decrease collisions, but they still heavily marketed roundabouts with that tagline anyway).

And even reduced severity is a poor metrics. If that was the ultimate one, reducing speed limit on interstates to 25 MPH should be a no-brainer.

Not in my opinion. Two cars bumping into each other at 80 is safer than a car going 50 rear-ending a car going 25. Which is to say, set speed limits closest to where the majority of cars are going the same speed (lack of differential = less severe collisions).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 16, 2016, 09:34:01 AM

My post (https://www.aaroads.com/forum/index.php?topic=15546.msg2151711#msg2151711), at the top of this page, was to bring up what I thought was an interesting discrepancy (the FHWA knew full well that roundabouts don't always decrease collisions, but they still heavily marketed roundabouts with that tagline anyway).

And even reduced severity is a poor metrics. If that was the ultimate one, reducing speed limit on interstates to 25 MPH should be a no-brainer.

Not in my opinion. Two cars bumping into each other at 80 is safer than a car going 50 rear-ending a car going 25. Which is to say, set speed limits closest to where the majority of cars are going the same speed (lack of differential = less severe collisions).

And you realize that 56% of fatalities occur in single-vehicle accidents?
(putting on traffic engineer hat) to reduce severity of such accidents on freeways, speed of free flowing traffic must be reduced to match that with the new speed limit. traffic calming measures may include lane narrowing and possibly chicanes. While increasing travel times and severely hurting US economy, these measures would allow increased ticket revenue and would reduce crash severity for single vehicle accidents and number of fatalities. Safety first!
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 17, 2016, 09:26:05 AM
My point was simply that roundabouts, as a whole, have a better severity record. There are inexplicable exceptions, of course, but, they're exceptions.

Prince Fielder of the Texas Rangers is batting .197 and having a pretty abysmal year.  Brett Eibner of the Kansas City Royals is batting .471 and is lighting it up.  Can you predict who has more hits?  Prince Fielder is having a bad year but he still has 39 more hits than Eibner (since Eibner only has 17 at bats vs. Fielder’s 238). 

You can have a lot more hits (ie. injury crashes) when you get more at bats (ie. frequency of crashes).  You admit that there is discrepancies in the FHWA's studies yet continue to regurgitate the misleading stats that they cite.  Sure, we can be clapping seals and say how great roundabouts are because they have low severity crashes.  But there should be some focus that at some of these 2x2 multi-lane roundabouts, the frequency of crashes has been abysmally high (leading to injury crashes).

Aren't roundabouts great!
(https://media.giphy.com/media/hDwYu8UEcUone/giphy.gif)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 17, 2016, 01:30:18 PM
  You admit that there is discrepancies in the FHWA's studies yet continue to regurgitate the misleading stats that they cite.  Sure, we can be clapping seals and say how great roundabouts are because they have low severity crashes. 

That is actually what I call indoctrination. Studies may be flawed, but we know the Truth!
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 17, 2016, 07:23:54 PM
You can have a lot more hits (ie. injury crashes) when you get more at bats (ie. frequency of crashes).

So, let me get this straight: roundabouts that had more collisions after installation, also had an increase in injuries (in every case)?? ......

You admit that there is discrepancies in the FHWA's studies yet continue to regurgitate the misleading stats that they cite.  Sure, we can be clapping seals and say how great roundabouts are because they have low severity crashes.  But there should be some focus that at some of these 2x2 multi-lane roundabouts, the frequency of crashes has been abysmally high (leading to injury crashes)

The problem is that there has been very little formal follow-up to the FHWA's initials studies. Some DOT's have investigated before-and-after situations, sometimes finding that the roundabouts resulted in far more collisions than anticipated, but there hasn't been, at least to my knowledge, any sort of legit follow-up, covering the whole of the nation's roundabouts. We've cherry-picked some roundabouts in this thread, but we both know this thread isn't any sort of official study (although I will admit, as I already have dozens of times, that the FHWA's initial studies might be a little off).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 20, 2016, 08:45:12 AM
The problem is that there has been very little formal follow-up to the FHWA's initials studies. Some DOT's have investigated before-and-after situations, sometimes finding that the roundabouts resulted in far more collisions than anticipated, but there hasn't been, at least to my knowledge, any sort of legit follow-up, covering the whole of the nation's roundabouts. We've cherry-picked some roundabouts in this thread, but we both know this thread isn't any sort of official study (although I will admit, as I already have dozens of times, that the FHWA's initial studies might be a little off).

I agree that more studies need to be done.  I already suggested a study that should be published...

This would be an eye opening study if it were published:

“The Safety Performance of Roundabouts with Average Daily Traffic exceeding 30,000”


The 30,000 ADT condition would weed out single-lane roundabouts and most 2x1 multi-lane roundabouts.  The focus would be nearly entirely on the safety performance of 2x2 (or higher) roundabouts in America. Ideally, the study would analyze interchange and non-interchange roundabouts separately and come up with two different sets of safety numbers.


Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 20, 2016, 05:36:14 PM
The problem is that there has been very little formal follow-up to the FHWA's initials studies. Some DOT's have investigated before-and-after situations, sometimes finding that the roundabouts resulted in far more collisions than anticipated, but there hasn't been, at least to my knowledge, any sort of legit follow-up, covering the whole of the nation's roundabouts. We've cherry-picked some roundabouts in this thread, but we both know this thread isn't any sort of official study (although I will admit, as I already have dozens of times, that the FHWA's initial studies might be a little off).

I agree that more studies need to be done.  I already suggested a study that should be published...

This would be an eye opening study if it were published:

“The Safety Performance of Roundabouts with Average Daily Traffic exceeding 30,000”


The 30,000 ADT condition would weed out single-lane roundabouts and most 2x1 multi-lane roundabouts.  The focus would be nearly entirely on the safety performance of 2x2 (or higher) roundabouts in America. Ideally, the study would analyze interchange and non-interchange roundabouts separately and come up with two different sets of safety numbers.


I suspect hourly traffic may be even more important. There are efforts on stretching commute hours - staged shifts, etc - to reduce hourly traffic while maintaining total number of vehicles.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 22, 2016, 07:59:26 AM
Pontiac Trail roundabout most accident-prone in Michigan

An Oakland County intersection is named the most-accident prone in Michigan.  The roundabout at Pontiac Trail and M-5 in Commerce Township had 186 crashes last year.  That's 54 more than any other intersection in the state. Coming in at number two was Telegraph and 12 Mile in Southfield while Eleven Mile and Van Dyke in Warren -- placing third.

http://www.fox2detroit.com/news/local-news/154684840-story
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on June 27, 2016, 12:52:28 PM
Waterloo Region (in Ontario) has dozens of roundabouts, but there is one that has an especially high collision rate; the roundabout at Homer Watson and Block Line in Kitchener.
http://www.therecord.com/opinion-story/6127192-the-record-s-view-this-roundabout-must-be-fixed-at-homer-watson-boulevard-and-block-line-road-in-ki/ (http://www.therecord.com/opinion-story/6127192-the-record-s-view-this-roundabout-must-be-fixed-at-homer-watson-boulevard-and-block-line-road-in-ki/)

Quote
There were 51 collisions at the roundabout in 2011, the year it opened. That number crept upward the next year, when 53 collisions were recorded, then soared in 2013 when there were 72 collisions.

To its credit, the region responded by changing signs, altering lanes and lowering speeds in the vicinity. The result? There were 107 collisions at the roundabout in 2014 – one every three or four days and more than double the number in 2012.

It originally had 3 lanes on one side, but after a bus hit one of my classmates at my high-school, they decided to close the third lane off. They also reduced the speed limit by 20 km/h, but most people ignore that and it hasn't improved the collision rate.

I personally like using roundabouts, but I think it would help a lot if more people would use their signals when exiting.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 27, 2016, 02:08:07 PM
Manufacturers are designing bulky a-pillar in a quest to receive five star safety ratings.  Do bulky A-pillar designs reduce driver visibility and lead to drivers pulling out into the roundabout thinking it’s clear when it’s not?  The curves of a roundabout can make it easy for a vehicle to get lost in the a-pillar.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/A-pillars_zpsrp1ucgda.jpg)
http://www.safespeed.org.uk/bike005.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on June 27, 2016, 02:17:18 PM
Manufacturers are designing bulky a-pillar in a quest to receive five star safety ratings.  Do bulky A-pillar designs reduce driver visibility and lead to drivers pulling out into the roundabout thinking it’s clear when it’s not?  The curves of a roundabout can make it easy for a vehicle to get lost in the a-pillar.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/A-pillars_zpsrp1ucgda.jpg)
http://www.safespeed.org.uk/bike005.pdf


Trebek: Over-exaggerations for $3 please?

And just wondering...why is the picture taken as if the driver is sitting in the middle of the front, rather than in front of the steering wheel?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 27, 2016, 03:52:58 PM
^I agree that "Killer Pillars" is over the top. 

That said, the point is still valid.  Just today i was approaching a roundabout and my a-pillar was blocking the view of a white pickup circulating through the roundabout.  I started to pull out infront of them just as they appeared from my a-pillar's "blind spot".  Luckily i was able to stop in time and no harm was done.  It was the first time i realized that my a-pillar was blocking the view of a circulating vehicle and i instantly took note of the scenario.  I was diligently scanning for circulating vehicles, but that white pickup still came out of nowhere to me.  It's not that i wasn't looking.     

Now the Monday morning quarterbacks will suggest a million different things i should have done to keep myself out of that scenario.  Ultimately, i feel like I almost got in an accident because i can't see through steel.  If I come to a complete stop before entering and turn my head from left-to-right to ensure a vehicle isn't in my a-pillar blind spot, then you get impatient drivers on the verge of rear-ending you because you aren't entering the roundabout fast enough for them.  If you just go assuming nobody is in your a-pillar blind spot, you risk pulling out infront of someone.  Honeslty, i'll piss off people behind me and let them rear end me before I pull out infront of a white-pickup again.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 27, 2016, 05:43:50 PM
I've had large A-pillars block me from seeing pedestrians about to cross, other vehicles when pulling out at a t-junction, literally anything when pulling straight out of a parking spot (after having backed in, which I do quite often). At roundabouts? Sure, but not any more often than at any other type of junction.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on June 27, 2016, 05:56:44 PM
I've had large A-pillars block me from seeing pedestrians about to cross, other vehicles when pulling out at a t-junction, literally anything when pulling straight out of a parking spot (after having backed in, which I do quite often). At roundabouts? Sure, but not any more often than at any other type of junction.

Exactly.  Blind spots are hardly unique to roundabouts. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 27, 2016, 07:44:43 PM
I've had large A-pillars block me from seeing pedestrians about to cross, other vehicles when pulling out at a t-junction, literally anything when pulling straight out of a parking spot (after having backed in, which I do quite often). At roundabouts? Sure, but not any more often than at any other type of junction.

Exactly.  Blind spots are hardly unique to roundabouts.

They are somewhat unique with respect to angles  being unusual. On "normal" intersection, 99% of cases traffic comes from exact left and exact right. There is a certain habit of looking for those directions, known head positions  - I don't know those positions but my body does.
A somewhat similar situation is (also roundabout related) a newly constructed merge to arterial - road was rerouted due to roundabout. I drive that spot every day, and it took me quite a while to get used to new alignment. I am not alone, I just witnessed a close call at the location with bus having to move half a lane to avoid collision.
Problem is that ramp merges to road in a curve, and main road traffic is in unusual spot somewhere between 7 and 8 o'clock - neither over the shoulder, nor in the mirror. Lots of drivers cut off main road traffic without seeing it...

I would say this is same effect.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 27, 2016, 08:45:58 PM
The blue line represents a vehicle path that may be in the blind spot of someone waiting to enter the roundabout.  The angles present at a roundabout can make it pretty easy for a vehicle to get lost in the a-pillar.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/A-pillar_zpszhee5qnz.png)

The most logical alternative to the roundabout pictured above would be a signaled intersection.  It’s true that blind spots are hardly unique to roundabouts.  Here’s another revelation … traffic is controlled by blinky lights at a signalized intersection.  The potential dangers of blind spots at signalized intersections can be alleviated by the use of traffic control devices (ie. no turn on red signs, protected only left turns, conflicting vehicle movements never come on together in the phasing, etc.).  You don’t have the same control at a free-flowing roundabout (you just got to live with the crashes). 
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on June 27, 2016, 09:05:52 PM
The blue line represents a vehicle path that may be in the blind spot of someone waiting to enter the roundabout.  The angles present at a roundabout can make it pretty easy for a vehicle to get lost in the a-pillar.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/A-pillar_zpszhee5qnz.png)

The most logical alternative to the roundabout pictured above would be a signaled intersection.  It’s true that blind spots are hardly unique to roundabouts.  Here’s another revelation … traffic is controlled by blinky lights at a signalized intersection.  The potential dangers of blind spots at signalized intersections can be alleviated by the use of traffic control devices (ie. no turn on red signs, protected only left turns, conflicting vehicle movements never come on together in the phasing, etc.).  You don’t have the same control at a free-flowing roundabout (you just got to live with the crashes). 


You're fucking kidding me, right? You're looking out the drivers door window, inches from ones face. I've been driving in circles and roundabouts all my life, and not once have I ever had such a gastrically huge blind spot.
Title: Re: Crash prone 'modern roundabouts'
Post by: Brian556 on June 28, 2016, 12:27:38 AM
I don't think this should be a problem. It is very easy to see, and you and always lean forward if nessessary.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 28, 2016, 05:42:52 PM
Experimental fencing has been installed at the crash prone roundabout of M-5 & Pontiac Trail in an effort to slow drivers down.  According to the article, the average speed of traffic coming off is 30-33 mph.  They want it to be 18-23 mph.  What does everyone think of this idea? 

http://www.wxyz.com/news/region/oakland-county/drivers-have-mixed-feelings-about-new-fences-at-m-5-roundabout 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 28, 2016, 05:56:15 PM
Experimental fencing has been installed at the crash prone roundabout of M-5 & Pontiac Trail in an effort to slow drivers down.  According to the article, the average speed of traffic coming off is 30-33 mph.  They want it to be 18-23 mph.  What does everyone think of this idea? 

http://www.wxyz.com/news/region/oakland-county/drivers-have-mixed-feelings-about-new-fences-at-m-5-roundabout 

Not in favor.  Reduce visibility to improve safety?  Not cool.  Driver speed through a roundabout should be controlled by geometry; in this case, I'd say they need to both flare the approaches and reduce the ICD.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 28, 2016, 06:06:35 PM
Experimental fencing has been installed at the crash prone roundabout of M-5 & Pontiac Trail in an effort to slow drivers down.  According to the article, the average speed of traffic coming off is 30-33 mph.  They want it to be 18-23 mph.  What does everyone think of this idea? 

http://www.wxyz.com/news/region/oakland-county/drivers-have-mixed-feelings-about-new-fences-at-m-5-roundabout 

Not in favor.  Reduce visibility to improve safety?  Not cool.  Driver speed through a roundabout should be controlled by geometry; in this case, I'd say they need to both flare the approaches and reduce the ICD.

That is a common problem of roundabouts as far as I can tell: when it is being built, it is cheap, it is efficient, it is maintenance-free
And then reality kicks in. Need to add crosswalk signals, rebuild approaches, add lighting, improve pedestrian and bike safety, provide additional training for snow plow drivers - and additional hours for them...   
How often they would need to replace those mesh fences - every two weeks?
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 28, 2016, 06:15:07 PM
Experimental fencing has been installed at the crash prone roundabout of M-5 & Pontiac Trail in an effort to slow drivers down.  According to the article, the average speed of traffic coming off is 30-33 mph.  They want it to be 18-23 mph.  What does everyone think of this idea? 

http://www.wxyz.com/news/region/oakland-county/drivers-have-mixed-feelings-about-new-fences-at-m-5-roundabout 

Not in favor.  Reduce visibility to improve safety?  Not cool.  Driver speed through a roundabout should be controlled by geometry; in this case, I'd say they need to both flare the approaches and reduce the ICD.

That is a common problem of roundabouts as far as I can tell: when it is being built, it is cheap, it is efficient, it is maintenance-free
And then reality kicks in. Need to add crosswalk signals, rebuild approaches, add lighting, improve pedestrian and bike safety, provide additional training for snow plow drivers - and additional hours for them...   
How often they would need to replace those mesh fences - every two weeks?

I'm curious to know when the roundabout in question was constructed.  The engineers should have known better than to build that large of an ICD and that straight of approaches if it was constructed in the last decade.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on June 28, 2016, 07:04:15 PM
Experimental fencing has been installed at the crash prone roundabout of M-5 & Pontiac Trail in an effort to slow drivers down.  According to the article, the average speed of traffic coming off is 30-33 mph.  They want it to be 18-23 mph.  What does everyone think of this idea? 

http://www.wxyz.com/news/region/oakland-county/drivers-have-mixed-feelings-about-new-fences-at-m-5-roundabout 

Not in favor.  Reduce visibility to improve safety?  Not cool.  Driver speed through a roundabout should be controlled by geometry; in this case, I'd say they need to both flare the approaches and reduce the ICD.

That is a common problem of roundabouts as far as I can tell: when it is being built, it is cheap, it is efficient, it is maintenance-free
And then reality kicks in. Need to add crosswalk signals, rebuild approaches, add lighting, improve pedestrian and bike safety, provide additional training for snow plow drivers - and additional hours for them...   
How often they would need to replace those mesh fences - every two weeks?

That stuff is generally taken care of in the planning process.

I drive a snowplow for a state.  We've never been given any additional training for roundabouts or circles. They are just another piece of asphalt that we have to clear snow from.

Again, this tells me that we're just making up excuses why roundabouts shouldn't be built, rather than using any actual concrete evidence why roundabouts shouldn't be built.  Again, every once in a while traditional intersections undergo modifications as well after they are constructed due to unforeseen events.  And snowplowing...training for a roundabout?  Ha!
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 28, 2016, 07:37:44 PM

I drive a snowplow for a state.  We've never been given any additional training for roundabouts or circles. They are just another piece of asphalt that we have to clear snow from.
And that is exactly why extra training is needed. Because that one incoming lane flares into two lanes for different roundabout lanes. So how many plow passes are required to clean that approach? Exactly, three passes because approach is 2 lanes + gore wide.
Some heroic plow drivers do two passes, leaving approximately 1.5 driving lane and then designed flow pattern is not completely screwed up.  Not really a problem since that snow usually melts in a month or so, but still.

And yes, this tells me that even DOTs have no understanding of how roundabouts work.. But hey, this is just a second decade of learning curve!
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 28, 2016, 07:52:52 PM
I'm curious to know when the roundabout in question was constructed.  The engineers should have known better than to build that large of an ICD and that straight of approaches if it was constructed in the last decade.

The approaches seem to have plenty of flair. You could add chicanes, like they do here in Washington, and all over Australia, but many drivers simply ignore the lane lines, drifting all over the place, in an attempt to keep up a high speed. The best way to slow down drivers, is to have them slow down naturally....

The wide visibility really is the biggest issue here. Roundabouts can have high-speeds, but only once you're in the circle...entering speeds need to be much lower. Not so low that a stop sign is the preferred method, but low enough that T-bone collisions don't suddenly become features of roundabouts.

High entry speeds are generally the result of good visibility. While that sounds like a good thing, driver's need to be giving way at or near the yield line, not 400 feet before the roundabout (in other words, you need to decide whether or not you can enter based on conditions present within 20 to 30 feet of the yield line). Because driver's had such excellent visibility, they were deciding whether or not they could enter well before reaching the circle ... some drivers, apparently, chose poorly.

If you decrease the size of the decision-making zone, entry speeds should decrease, because drivers will need to slow down to confirm that they can enter (the smaller size of this zone will naturally result in lower speeds).

The good news is that, if this is successful (which I'm sure it will be), the county will be installing more permanent decoration, such as bushes).

(http://i.imgur.com/FOAQ274.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 28, 2016, 09:05:00 PM
The M-5/Pontiac Trail roundabout saw a big spike in crashes in 2015.  It just so happens the roundabout was part of a major detour route in 2015 during the Haggerty Road closure.  The traffic patterns the roundabout was exposed to during the detour didn’t match the traffic patterns the roundabout was designed for.  Sure, roundabouts can work well under specific scenarios, but when the moon and stars don’t align you can get into trouble.   

My concern is any report dealing with the effectiveness of the experimental fencing will be biased towards comparing 2015 to 2016 crash data.  That to me won’t be a fair comparison.   People will think the fencing is effective simply because there was a year over year drop in crashes.  Again, the traffic patterns at the roundabout during the detour last year doesn’t match the traffic patterns occurring during this experimental fencing test.  That’s a huge point that shouldn’t be ignored.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on June 29, 2016, 12:15:19 AM

I drive a snowplow for a state.  We've never been given any additional training for roundabouts or circles. They are just another piece of asphalt that we have to clear snow from.
And that is exactly why extra training is needed. Because that one incoming lane flares into two lanes for different roundabout lanes. So how many plow passes are required to clean that approach? Exactly, three passes because approach is 2 lanes + gore wide.
Some heroic plow drivers do two passes, leaving approximately 1.5 driving lane and then designed flow pattern is not completely screwed up.  Not really a problem since that snow usually melts in a month or so, but still.

And yes, this tells me that even DOTs have no understanding of how roundabouts work.. But hey, this is just a second decade of learning curve!

What?

You do understand I plow in a state with traffic circles wider than nearly any roundabout, and dealing not only with normal roads entering and exiting, but driveways and parking lots accessing the circle as well.

Circles are just like any other road feature. Put the plow down and push the snow. Spread salt to help melt the snow. Repeat as necessary.

There's an art to it. It takes time to clear a road, and keep it cleared. It's not like there's a wall of 20 inches of snow that traffic can't travel thru.  But with snow falli!g off vehicles, even a plowed road will become slushy again.

A 90 degree right turn at an intersection is worse. Those trucks don't turn on a dime, and snow sticks out far from the curb. Plow operators just keep going at it until it's acceptable.

Please...offer your services to plow a road. No doubt you'll do better than everyone else.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 29, 2016, 01:02:42 PM

What?

You do understand I plow in a state with traffic circles wider than nearly any roundabout, and dealing not only with normal roads entering and exiting, but driveways and parking lots accessing the circle as well.

Circles are just like any other road feature. Put the plow down and push the snow. Spread salt to help melt the snow. Repeat as necessary.

There's an art to it. It takes time to clear a road, and keep it cleared. It's not like there's a wall of 20 inches of snow that traffic can't travel thru.  But with snow falli!g off vehicles, even a plowed road will become slushy again.

A 90 degree right turn at an intersection is worse. Those trucks don't turn on a dime, and snow sticks out far from the curb. Plow operators just keep going at it until it's acceptable.

Please...offer your services to plow a road. No doubt you'll do better than everyone else.

Possibly things are much better in NJ; but roundabouts I deal with in NY often had 2/3 lane under  snow a week after snow ended.  At least that was the case during last winter, 2014/2015 (we didn't have any winter in 2015/2016).  I don't remember any problems with right turns except for barricades of snow pushed from  the main road blocking side roads/driveways. Once again, could be different vehicles used in different places.
And well, thing is turning around and doing another pass at roundabout approach seem less than straightforward. You either need to look for a u-turn spot, or back along curved approach. I am not sure if it is done really carefully
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 29, 2016, 01:12:03 PM
I'm curious to know when the roundabout in question was constructed.  The engineers should have known better than to build that large of an ICD and that straight of approaches if it was constructed in the last decade.

You seem to be implying that a smaller ICD would have been more effective at reducing the number of crashes.  To your original question, the M-5/Pontiac Trail roundabout was constructed in 2011.  While there was an increase in crashes after the roundabout was constructed, the crash rate wasn’t as high as other multi-lane roundabouts cited in this thread.  It wasn’t until 2015 when the roundabout had a big spike in crashes (likely due to it being part of a major detour route).  Now you are throwing the roundabout design under the bus because of an abnormally high number of crashes in 2015.  Yes, a roundabout that experiences 100 crashes in a year is a problem, but you are trying to convince me a smaller ICD would have done better.  I’m not buying it. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 29, 2016, 03:41:22 PM
A 3x2 roundabout at Superior & 14th in Lincoln, NE was constructed in 2012.  Due to the large increase in accidents, one of the circulating lanes was removed in 2013.  It is now a 2x1 roundabout.  In addition, they added fencing at all 4-approaches in 2014.  Now they are talking about spending $888,000 to add more permanent features to replace the "ugly" fencing.  I haven't read any reports indicating how effective the fencing was, but i'm assuming the roundabout saw a big drop in crashes simply because it went from a 3x2 to a 2x1 roundabout.

http://www.1011now.com/content/news/More-updates-likely-coming-to-14th--Superior-roundabout-373306771.html

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 29, 2016, 05:53:38 PM
The problem is we don't know if the fencing was successful at the Lincoln, NE roundabout.  They compared the crash rate of the 3x2 roundabout with no fencing to the 2x1 roundabout with fencing.  I could have told you the crash rate would drop if you convert the roundabout to a simplified 2x1 roundabout.  But what effect did the fencing have?  We have no idea because they lumped in the lane configuration changes with the fence change.

Quote
When the 14th and Superior roundabout was initially built and opened to traffic the crash rate was higher than anticipated. We had the configuration of the initial roundabout studied and the results showed that we needed to reduce the number of lanes and also reduce the sight distance at the roundabout. One lane in each direction was removed with traffic control devices. The site distance was limited by constructing chain link fence with slats in the medians.

The devices have been in place for approximately two years. The results show that the crash rate has been reduced significantly by the lane reduction and the fencing. At this point we are moving ahead with making the temporary adjustments to the roundabout more permanent. Concept plans have been developed to show putting tack on median concrete in place of the lane reductions. This will allow us to remove the traffic control devices along the outer lanes. A landscaping plan was developed for the center island of the roundabout and the medians. The landscaping and a short decorative fence have been shown to take the place of the chain link fence.

Along with this work a piece of artwork will be loaned to the city from the Duncans to be placed in the center of the roundabout. Construction on the more permanent fixes for the roundabout could begin as early as Fall of 2016.
https://www.lincoln.ne.gov/city/pworks/projects/14th/superior-safety/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 29, 2016, 09:27:53 PM
Venice is proposing changes to the crash prone roundabout at Jacaranda Blvd and Venice Avenue.  Since it’s completion in 2008, the roundabout has held the dubious distinction as being the top intersection for wrecks in Sarasota and Manatee Counties.  To combat this, FDOT plans on eliminating a circulating lane inside the roundabout.


Edit:  The proposed roundabout changes slated to cost $585,000 has been approved by the transportation agency.

http://www.wftv.com/news/florida/roundabout-changes-okdjacaranda-and-venice-avenue-intersection-deemed-high-crash-zonekd/332095543
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 30, 2016, 08:53:33 PM
I'm curious to know when the roundabout in question was constructed.  The engineers should have known better than to build that large of an ICD and that straight of approaches if it was constructed in the last decade.

You seem to be implying that a smaller ICD would have been more effective at reducing the number of crashes.  To your original question, the M-5/Pontiac Trail roundabout was constructed in 2011.  While there was an increase in crashes after the roundabout was constructed, the crash rate wasn’t as high as other multi-lane roundabouts cited in this thread.  It wasn’t until 2015 when the roundabout had a big spike in crashes (likely due to it being part of a major detour route).  Now you are throwing the roundabout design under the bus because of an abnormally high number of crashes in 2015.  Yes, a roundabout that experiences 100 crashes in a year is a problem, but you are trying to convince me a smaller ICD would have done better.  I’m not buying it. 

My assertion is that the roundabout should be designed with a smaller ICD and more-flared approaches in order to reduce driver speed, which is what the fencing is supposed to accomplish.

The approaches do have some flare, but not enough. If a driver is physically able to enter the circulating roadway at such speeds, then the geometry of the roundabout is not doing its job. Approaches need to be flared enough that a driver cannot exceed the target speed upon entry. A smaller ICD does the same for vehicles already in the roadway; this, IMO, is a lesser issue but does contribute to a driver's perception as to whether or not it's OK to push the envelope.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 30, 2016, 10:29:35 PM
My assertion is that the roundabout should be designed with a smaller ICD and more-flared approaches in order to reduce driver speed, which is what the fencing is supposed to accomplish.

It seems like you can get more flare at larger diameter roundabouts.  If a roundabout is too small you are limited to how much you can flare the approach out (before you overshoot the circle so to speak).  I have a few other points why I believe larger ICD roundabouts may be more effective at reducing crashes:

#1. You don’t want the fastest path of a roundabout to resemble a straight line if your goal is to keep speeds down.  Which red line resembles a drag strip? 

Small ICD roundabout:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/fastestpath_zpskfw1ywq5.jpg)

Large ICD roundabout:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/largeICD2_zpsrqj98twj.png)

#2. Drivers have more reaction time when the approach legs of a roundabout are spread out.  Imagine CAR A enters the roundabout mistakenly believing CAR B is about to exit.  Would u want CAR B to take 1.7 seconds or 3.4 seconds to travel the blue path?  Now it’s true that the average circulating speeds might be SLIGHTLY higher at the larger ICD roundabout but the speeds wouldn’t be drastically different.  Instead of 3.4 seconds reaction time at the large ICD roundabout, it might really be 3 seconds because the car is circulating at 23 mph as opposed to 20 mph.  Still, would you want 1.7 second reaction time or 3 second reaction time when taking evasive action?

Small ICD roundabout:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test4_zpshnyyiesp.jpg)

Large ICD roundabout:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Test3_zpscdfdzp4h.jpg)

#3.  Look at the empirical evidence.  The 2x2 multi-lane roundabouts with smaller central island diameters have a greater increase in crashes than the roundabouts with larger central island diameters:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBDATASummary_zpsg7upbybr.png)

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 30, 2016, 10:37:15 PM
One other point about the fencing idea.  Sure, you restrict the visibility of vehicles inside the roundabout but you also restrict the visibility of pedestrians inside the crosswalk (who are crossing the exit leg of the roundabout).  Is it really a good idea to restrict the visibility of pedestrians?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 01, 2016, 12:53:01 AM
One other point about the fencing idea.  Sure, you restrict the visibility of vehicles inside the roundabout but you also restrict the visibility of pedestrians inside the crosswalk (who are crossing the exit leg of the roundabout).  Is it really a good idea to restrict the visibility of pedestrians?

I think it's better to hide the pedestrians until they are about to cross each carriageway. That way, overly-courteous drivers in the other carriageway don't stop too early. Use those yellow flashing beacons if visibility is truly an issue.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on July 01, 2016, 07:49:20 AM
Fencing also keeps pedestrians crossing where they should be crossing, rather than jumping out into the street wherever they feel like.  Good for motorists too, as they shouldn't come upon a ped in a random part of the road. As long as the fence is 3 feet high or so, visibility isn't reduced for either peds or motorists.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 01, 2016, 09:26:38 AM
One other point about the fencing idea.  Sure, you restrict the visibility of vehicles inside the roundabout but you also restrict the visibility of pedestrians inside the crosswalk (who are crossing the exit leg of the roundabout).  Is it really a good idea to restrict the visibility of pedestrians?

I think it's better to hide the pedestrians until they are about to cross each carriageway. That way, overly-courteous drivers in the other carriageway don't stop too early. Use those yellow flashing beacons if visibility is truly an issue.
It's even better to hide pedestrians until they are past windshield.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 13, 2016, 11:33:21 AM
The Lee Road roundabout in Livingston County has been previously discussed on this thread.  It had the second highest number of INJURY crashes in Livingston County over the past 5 years and by far the highest number of total crashes.

http://www.livingstondaily.com/story/news/local/community/livingston-county/2015/11/23/livingston-countys-worst-intersections-crashes/75170418/

The Livingston County Road Commission is now considering a proposal which would eliminate a circulating lane within the roundabout. 

http://www.livingstondaily.com/story/news/local/community/green-oak-township/2016/06/10/lee-road-roundabout-redo-considered/85645684/

Here seems to be the trend when it comes to complex 2x2 and 2x3 multi-lane roundabouts in the United States:

1.   Agencies propose a complex multi-lane roundabout, citing safety studies that are heavily skewed towards single-lane and/or simplified 2x1 multi-lane roundabouts (ie. the 2000 Insurance Institute for Highway Safety study).
2.   The multi-lane roundabout is built and there is a big spike in total crashes.
3.   Agencies “tweak”  the roundabout to combat the high crash rate, making minor pavement marking/signage changes.  While these tweaks can reduce the crash rate, they often leave a lot to be desired (ie. there is still too many crashes even after the tweaks).
4.   Agencies decide to remove a circulating lane inside the roundabout to simplify the design (converting 2x2 roundabouts to 2x1 or even single lane roundabouts).   Eliminating a circulating lane can often be done without affecting operation too much since the roundabout was originally designed for 2035 (or whatever) traffic volumes.  Simplifying the roundabout often solves the crash problem. 

Of the 2x2 and 2x3 roundabouts cited in this thread, many are seeing circulating lanes removes due to the high crash rates.  At what point do agencies question whether these complex roundabouts are acceptable in terms of safety?  Should these complex roundabouts be built in the first place if they are just going to be downsized within years of being constructed? 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 13, 2016, 02:35:20 PM
The 10 Most Dangerous Roundabouts in Metro Detroit:

1. M-5/Martin Parkway at Pontiac Trail — Commerce Township Total crashes: 186

2. Van Dyke Ave. (M-53) at 18 1/2 Mile Road — Sterling Heights Total crashes: 124

3. State Street at Ellsworth Road — Ann Arbor/Pittsfield Township Total crashes: 114

4. Maple Road at Farmington Road — West Bloomfield Township Total crashes: 84

5. 14 Mile Road at Farmington Road — Farmington Hills/West Bloomfield Total crashes: 79

6. Maple Road at Drake Road — West Bloomfield Township Total crashes: 63

7. Lee Road at Whitmore Lake Road — Brighton/Green Oak Township Total crashes: 60

8. Martin Parkway at Oakley Park Road — Commerce Township Total crashes: 53

9. Hamlin Road at Livernois Road — Rochester Hills Total crashes: 41

10. Romeo Plank Road at 19 Mile Road — Clinton Township Total crashes: 37

http://womc.cbslocal.com/2016/05/11/the-10-most-dangerous-roundabouts-in-metro-detroit/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 13, 2016, 02:49:03 PM
The roundabout at Van Dyke & 18 1/2 Mile in Metro Detroit was built over a decade ago.  In 2015 it had 124 crashes.  It may be an example of a roundabout that was overbuilt:

(http://www.atdetroit.net/forum/messages/107211/117735.jpg)
(http://www.atdetroit.net/forum/messages/107211/117734.jpg)

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 25, 2016, 11:27:05 AM
New 2015 crash data released for SE Michigan.  The Ellsworth roundabout in Ann Arbor (which averaged 15.5 crashes before the roundabout) has averaged 140 crashes the first 2 years of operation.    If you dig deeper with the numbers, there was 2 injury crashes at the intersection from 2011-2012 (before data) and 9 injury crashes from 2014-2015 (after data). 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Ells_zpspgdzs2in.png)
http://semcog.org/Data-and-Maps/High-Frequency-Crash-Locations

So to recap…
Average total crashes before roundabout = 15.5
Average total crashes after roundabout = 140
That’s a 803% increase  :wow:  in total crashes….

Average injury crashes before roundabout = 1
Average injury crashes after roundabout = 4.5
That’s a 350% increase  :crazy:  in injury crashes… 
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on July 25, 2016, 11:40:31 AM
New 2015 crash data released for SE Michigan.  The Ellsworth roundabout in Ann Arbor (which averaged 15.5 crashes before the roundabout) has averaged 140 crashes the first 2 years of operation.    If you dig deeper with the numbers, there was 2 injury crashes at the intersection from 2011-2012 (before data) and 9 injury crashes from 2014-2015 (after data). 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Ells_zpspgdzs2in.png)
http://semcog.org/Data-and-Maps/High-Frequency-Crash-Locations

So to recap…
Average total crashes before roundabout = 15.5
Average total crashes after roundabout = 140
That’s a 803% increase  :wow:  in total crashes….

Average injury crashes before roundabout = 1
Average injury crashes after roundabout = 4.5
That’s a 350% increase  :crazy:  in injury crashes…

One problem I see with this roundabout is the lack of any obstruction in the centre. Even though it's counter-intuitive, it's better to block people from being able to see across the middle, since it's an unnecessary distraction. Putting some tall plants in the middle would force people to pay attention to cars on their left, like they should.

I still agree though that those crash statistics are still crazy, especially the increase in injury crashes!
https://www.google.ca/maps/@42.2292761,-83.7391719,3a,75y,54.44h,74.65t/data=!3m7!1e1!3m5!1srAaeg2wFciLs9vpdpmQH9A!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3DrAaeg2wFciLs9vpdpmQH9A%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D250.00459%26pitch%3D0!7i13312!8i6656 (https://www.google.ca/maps/@42.2292761,-83.7391719,3a,75y,54.44h,74.65t/data=!3m7!1e1!3m5!1srAaeg2wFciLs9vpdpmQH9A!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3DrAaeg2wFciLs9vpdpmQH9A%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D250.00459%26pitch%3D0!7i13312!8i6656)
(http://i.imgur.com/JyPhrx3.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 25, 2016, 11:46:33 AM
New 2015 crash data released for SE Michigan.  The Ellsworth roundabout in Ann Arbor (which averaged 15.5 crashes before the roundabout) has averaged 140 crashes the first 2 years of operation.    If you dig deeper with the numbers, there was 2 injury crashes at the intersection from 2011-2012 (before data) and 9 injury crashes from 2014-2015 (after data). 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Ells_zpspgdzs2in.png)
http://semcog.org/Data-and-Maps/High-Frequency-Crash-Locations

So to recap…
Average total crashes before roundabout = 15.5
Average total crashes after roundabout = 140
That’s a 803% increase  :wow:  in total crashes….

Average injury crashes before roundabout = 1
Average injury crashes after roundabout = 4.5
That’s a 350% increase  :crazy:  in injury crashes…

One problem I see with this roundabout is the lack of any obstruction in the centre. Even though it's counter-intuitive, it's better to block people from being able to see across the middle, since it's an unnecessary distraction. Putting some tall plants in the middle would force people to pay attention to cars on their left, like they should.

I still agree though that those crash statistics are still crazy, especially the increase in injury crashes!
https://www.google.ca/maps/@42.2292761,-83.7391719,3a,75y,54.44h,74.65t/data=!3m7!1e1!3m5!1srAaeg2wFciLs9vpdpmQH9A!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3DrAaeg2wFciLs9vpdpmQH9A%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D250.00459%26pitch%3D0!7i13312!8i6656 (https://www.google.ca/maps/@42.2292761,-83.7391719,3a,75y,54.44h,74.65t/data=!3m7!1e1!3m5!1srAaeg2wFciLs9vpdpmQH9A!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3DrAaeg2wFciLs9vpdpmQH9A%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D250.00459%26pitch%3D0!7i13312!8i6656)
(http://i.imgur.com/JyPhrx3.png)

For a small roundabout like that, car across the circle is a potential conflict if making 270 turn. 
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on July 25, 2016, 11:57:02 AM
New 2015 crash data released for SE Michigan.  The Ellsworth roundabout in Ann Arbor (which averaged 15.5 crashes before the roundabout) has averaged 140 crashes the first 2 years of operation.    If you dig deeper with the numbers, there was 2 injury crashes at the intersection from 2011-2012 (before data) and 9 injury crashes from 2014-2015 (after data). 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Ells_zpspgdzs2in.png)
http://semcog.org/Data-and-Maps/High-Frequency-Crash-Locations

So to recap…
Average total crashes before roundabout = 15.5
Average total crashes after roundabout = 140
That’s a 803% increase  :wow:  in total crashes….

Average injury crashes before roundabout = 1
Average injury crashes after roundabout = 4.5
That’s a 350% increase  :crazy:  in injury crashes…

One problem I see with this roundabout is the lack of any obstruction in the centre. Even though it's counter-intuitive, it's better to block people from being able to see across the middle, since it's an unnecessary distraction. Putting some tall plants in the middle would force people to pay attention to cars on their left, like they should.

I still agree though that those crash statistics are still crazy, especially the increase in injury crashes!
https://www.google.ca/maps/@42.2292761,-83.7391719,3a,75y,54.44h,74.65t/data=!3m7!1e1!3m5!1srAaeg2wFciLs9vpdpmQH9A!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3DrAaeg2wFciLs9vpdpmQH9A%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D250.00459%26pitch%3D0!7i13312!8i6656 (https://www.google.ca/maps/@42.2292761,-83.7391719,3a,75y,54.44h,74.65t/data=!3m7!1e1!3m5!1srAaeg2wFciLs9vpdpmQH9A!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3DrAaeg2wFciLs9vpdpmQH9A%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D250.00459%26pitch%3D0!7i13312!8i6656)
(http://i.imgur.com/JyPhrx3.png)

For a small roundabout like that, car across the circle is a potential conflict if making 270 turn. 

Here's a similar-sized (maybe even smaller?) roundabout in Kitchener, ON (Lancaster St and Bridge St) (https://www.google.ca/maps/@43.4823287,-80.4829546,3a,75y,107.05h,73.25t/data=!3m6!1e1!3m4!1snwrJ9k0G9fr6T6M0g8wUiQ!2e0!7i13312!8i6656) that has trees and bushes in the middle. Maybe this policy differs by region?
(http://i.imgur.com/Dwtc7dI.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 25, 2016, 12:21:35 PM
Here's a similar-sized (maybe even smaller?) roundabout in Waterloo, ON (Lancaster St and Bridge St) (https://www.google.ca/maps/@43.4823287,-80.4829546,3a,75y,107.05h,73.25t/data=!3m6!1e1!3m4!1snwrJ9k0G9fr6T6M0g8wUiQ!2e0!7i13312!8i6656) that has trees and bushes in the middle. Maybe this policy differs by region?

http://i.imgur.com/Dwtc7dI.png

I'm not sure if it's official policy to decorate the center of the circle, but, it's highly recommended. Several guides that I've seen in the past recommend center decorations to prevent drivers from seeing more than just what's to the left of them.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 25, 2016, 12:37:27 PM

For a small roundabout like that, car across the circle is a potential conflict if making 270 turn. 

Here's asimilar-sized (maybe even smaller?) roundabout in Waterloo, ON (Lancaster St and Bridge St)[/url] that has trees and bushes in the middle. Maybe this policy differs by region?
Which tells nothing about safety of the design, any statistical data on this one?
With 30 meters diameter a car across has about 50 meters to travel before conflict. That is about 5 seconds at recommended speed, and 3 seconds since seeing it with decoration on the center. Is that enough to accelerate and clear the path? Most drivers don't really utilize full 0-60 acceleration rating  at each start... 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 25, 2016, 01:47:06 PM
I'll bring this up here since it was mentioned in another thread.  Another complex crash prone roundabout is being simplified.  The Steptoe St. & Columbia Park roundabout in Tri-Cities, Washington is having a circulating lane removed inside the roundabout.  Yet another example of combating a high crash rate roundabout by removing a circulating lane:

http://goo.gl/kWNe0i
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 25, 2016, 02:29:01 PM
I'll bring this up here since it was mentioned in another thread.  Another complex crash prone roundabout is being simplified.  The Steptoe St. & Columbia Park roundabout in Tri-Cities, Washington is having a circulating lane removed inside the roundabout.  Yet another example of combating a high crash rate roundabout by removing a circulating lane:

http://goo.gl/kWNe0i
Next step should be removal of central island and adding color coded signal light...
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on July 25, 2016, 03:02:40 PM

For a small roundabout like that, car across the circle is a potential conflict if making 270 turn. 

Here's a similar-sized (maybe even smaller?) roundabout in Kitchener, ON (Lancaster St and Bridge St) that has trees and bushes in the middle. Maybe this policy differs by region?

Which tells nothing about safety of the design, any statistical data on this one?
With 30 meters diameter a car across has about 50 meters to travel before conflict. That is about 5 seconds at recommended speed, and 3 seconds since seeing it with decoration on the center. Is that enough to accelerate and clear the path? Most drivers don't really utilize full 0-60 acceleration rating  at each start...

It's not in the top 100 most crash-prone intersections in the Region of Waterloo.
http://www.regionofwaterloo.ca/en/gettingAround/resources/2014-Collision-Ranking---By-Rank.pdf (http://www.regionofwaterloo.ca/en/gettingAround/resources/2014-Collision-Ranking---By-Rank.pdf)

I can't find any statistics for this roundabout though :/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 25, 2016, 03:26:08 PM
It's not in the top 100 most crash-prone intersections in the Region of Waterloo.
http://www.regionofwaterloo.ca/en/gettingAround/resources/2014-Collision-Ranking---By-Rank.pdf (http://www.regionofwaterloo.ca/en/gettingAround/resources/2014-Collision-Ranking---By-Rank.pdf)

I can't find any statistics for this roundabout though :/

I don't see the Homer Watson Blvd and Block Road roundabout on that list.  Did they just leave out roundabouts in their analysis or is that intersection not part of the Waterloo region?

It's somewhat surprising they are going ahead with building a massive 3x2 roundabout at Ottawa Street & Homer Watson Blvd after all the issues with the Homer Watson Blvd & Block Road roundabout.  Based on your link, Ottawa Street & Homer Watson Blvd is the most crash prone intersection in the entire region.  Time will tell if the crash problem gets better or worse after the roundabout is completed. 

(http://i1309.photobucket.com/albums/s636/mithokey/db7262ee47b7a5bc63900ea74112-500x329_zpsapmftepa.jpeg)
http://www.waterlooregionconnected.com/printthread.php?tid=339&page=1
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on July 25, 2016, 03:52:22 PM
It's not in the top 100 most crash-prone intersections in the Region of Waterloo.
http://www.regionofwaterloo.ca/en/gettingAround/resources/2014-Collision-Ranking---By-Rank.pdf (http://www.regionofwaterloo.ca/en/gettingAround/resources/2014-Collision-Ranking---By-Rank.pdf)

I can't find any statistics for this roundabout though :/

I don't see the Homer Watson Blvd and Block Road roundabout on that list.  Did they just leave out roundabouts in their analysis or is that intersection not part of the Waterloo region?

I decided to read the full report this time, and I found this on page 35 (http://www.regionofwaterloo.ca/en/gettingAround/resources/2014_ANNUAL_COLLISION_REPORT.pdf)

(http://i.imgur.com/tAncAEP.png)

So, there are 13 roundabouts in the "Top 100" chart I posted earlier, but the other 7 roundabouts (as of 2014) were there for less than five years, so they were included in the table above. Unfortunately, there isn't much data there. I also still don't see the Bridgeport and Lancaster roundabout I mentioned earlier, maybe it's newer than I thought.

It's somewhat surprising they are going ahead with building a massive 3x2 roundabout at Ottawa Street & Homer Watson Blvd after all the issues with the Homer Watson Blvd & Block Road roundabout.  Based on your link, Ottawa Street & Homer Watson Blvd is the most crash prone intersection in the entire region.  Time will tell if the crash problem gets better or worse after the roundabout is completed. 

(http://i1309.photobucket.com/albums/s636/mithokey/db7262ee47b7a5bc63900ea74112-500x329_zpsapmftepa.jpeg)
http://www.waterlooregionconnected.com/printthread.php?tid=339&page=1

I know what you mean, and I'm sure this will be controversial. But the transportation departments in the Region and the Cities here seem to like roundabouts :-D. They're also putting in two roundabouts on Erb St west of the current roundabout with Ira Needles/Erbsville; they're building a new Costco and they believe it'll help with traffic flow.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 25, 2016, 04:02:30 PM
I know what you mean, and I'm sure this will be controversial. But the transportation departments in the Region and the Cities here seem to like roundabouts :-D. They're also putting in two roundabouts on Erb St west of the current roundabout with Ira Needles/Erbsville; they're building a new Costco and they believe it'll help with traffic flow.
Lets call it religious attitude. After all, it is for everyone's safety! And don't let stupid numbers to obscure the dogma  :poke:
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on July 25, 2016, 04:09:53 PM
Lets call it religious attitude. After all, it is for everyone's safety! And don't let stupid numbers to obscure the dogma  :poke:

Funny, that's what a lot of us would say about tradephoric's repeated goalpost-shifting in this thread.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 25, 2016, 05:33:38 PM
Lets call it religious attitude. After all, it is for everyone's safety! And don't let stupid numbers to obscure the dogma  :poke:

Funny, that's what a lot of us would say about tradephoric's repeated goalpost-shifting in this thread.
You see, I tried real hard - but looks like there is no solid justification for roundabouts published in English. There is some anecdotal evidence that those sometimes cause problems, and equally anecdotal evidence that is may sometimes work. But I didn't find any understanding of WHY and WHEN it goes one way or the other. But everyone is sure it is best thing since sliced bread.
There are some quite interesting works on lane capacity, for example. I didn't see anything of remotely similar quality about roundabouts... 
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on July 25, 2016, 08:09:58 PM
Living in an area (near Carmel IN) with well over 100 roundabouts nearby, I can definitely state that the roundabouts provide a huge advantage for traffic flow.  It is so much better now for traveling the area without having to stop and wait at so many lights and stop signs.  Traffic used to back up significantly before the roundabouts were added.   Is it perfect?  No.  But it is far and away better than it was before the roundabouts were added.  Both my travel times and my gas mileage have noticeably improved.

I have no safety concerns driving the many roundabouts in the area.  A little bit of defensive driving (anticipate that there are other drivers on the road that don't know what they are doing) goes a long way toward avoiding any issues. 

The roundabouts are very popular with the local residents, and another 32 (http://www.carmel.in.gov/Modules/ShowDocument.aspx?documentID=7050) are going to be added within the next several years (http://www.indystar.com/story/news/local/hamilton-county/2016/01/06/carmel-outlines-bold-roundabout-plan/78258640/).  Can't wait for the further improvements in local traffic.



Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 26, 2016, 01:25:25 AM
I have no safety concerns driving the many roundabouts in the area.  A little bit of defensive driving (anticipate that there are other drivers on the road that don't know what they are doing) goes a long way toward avoiding any issues. 

Here is the citywide crash data for Carmel dating back to 2010.
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Carmelroundcrash_zpsdu8wf4uh.png)

There has been a 39% increase in total crashes (2442 crashes in 2015 / 1754 crashes in 2010) and a 56% increase in injury crashes (241 injury crashes in 2015 / 154 injury crashes in 2010).  The population of Carmel has increased 12% in the same time-frame (88,713 in 2015 / 79,191 in 2010).  Population data: http://www.carmel.in.gov/index.aspx?page=45

Ironically, both of Carmel’s fatal crashes in 2014 occurred at roundabouts.  Carmel still has its fair share of “dangerous”  traffic signals; yet the “safe”  roundabouts were the site of the fatal crashes.  We’ve all been told by the “experts”  that roundabouts reduce fatal crashes by 90%.... perhaps they fabricated that safety statistic. 

http://fox59.com/2014/08/06/one-dead-in-carmel-accident-passenger-taken-to-hospital/
http://fox59.com/2014/09/26/person-dead-after-motorcycle-accident-in-carmel/
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on July 26, 2016, 08:10:07 AM
Seems to me that there might have been a reporting change between 2013 and 2014. Quite the big data jump without an explanation of all the contributing factors.
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on July 28, 2016, 12:18:09 PM
Seems to me that there might have been a reporting change between 2013 and 2014. Quite the big data jump without an explanation of all the contributing factors.

For the Homer Watson/Block Line roundabout, the increase in crashes is likely due to the opening of the Block Line Rd bridge on Nov 22nd, 2013:
http://www.therecord.com/news-story/4230728-new-block-line-road-bridge-opening-friday-in-kitchener/ (http://www.therecord.com/news-story/4230728-new-block-line-road-bridge-opening-friday-in-kitchener/)

The bridge, location shown below, provides a useful E-W link between Homer Watson and Courtland Rd/Fairway Rd
(http://i.imgur.com/3fN8w9h.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 28, 2016, 03:05:54 PM
http://wishtv.com/2015/10/08/roundabouts-may-confuse-but-stats-back-up-their-safety/
My favorite quote(s):
Quote
And even if you make a mistake, because speeds are so slow, most wrecks don’t involve serious injuries....[Carmel Mayor Jim Brainard] points out that because accidents and injuries are down in Carmel, insurance rates have dropped. He says the city doesn’t have a full “jaws of life”  crew in its fire department anymore because they don’t have the high speed impacts that they used to have and don’t need them very often.

Total accidents and injury crashes have gone up in Carmel since that quote.  The number of injury crashes has risen 56% in Carmel over the past 6 years.  In addition the only two fatal crashes that occurred in Carmel in 2014 happened at roundabouts.  A lot of good it did not having a full “jaws of life”  crew.  Let's all give Jim Brainard a hand for making his city so safe.  :clap:  :clap:  :clap:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Carmelroundcrash_zpsdu8wf4uh.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: epzik8 on July 30, 2016, 01:06:40 PM
Did anyone mention Maryland's Hampstead Bypass? I clinched Maryland Route 30 this month - I went straight from Reisterstown to Hanover, PA - and on the Hampstead Bypass, a car with a Pennsylvania plate whose driver was obviously headed to Hanover started to exit onto MD-482 east, then suddenly switched lanes right in front of me to stay on MD-30 north. It's a two-lane circle with the left lane in each direction at every circle intended for drivers staying on MD-30. Problem is, some drivers don't realize that and will then cut in front of you to avoid making a wrong turn onto 482 or Business 30 or whatever the cross street of that other circle is.

Honorable mention to the two-lane circle at U.S. 15 and MD-464 in Point of Rocks. Also to the pair of U.S. 15/U.S. 50 circles in Loudoun County, Virginia.
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on August 02, 2016, 07:12:34 PM
Manufacturers are designing bulky a-pillar in a quest to receive five star safety ratings.  Do bulky A-pillar designs reduce driver visibility and lead to drivers pulling out into the roundabout thinking it’s clear when it’s not?  The curves of a roundabout can make it easy for a vehicle to get lost in the a-pillar.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/A-pillars_zpsrp1ucgda.jpg)
http://www.safespeed.org.uk/bike005.pdf

This is my biggest complaint about my current car, the Dodge Caliber. The pillars definitely reduce visibility. But I don't find them too bad with roundabouts; I find making left turns the worst, since pedestrians can easily "hide" behind them. I have to move head to see behind the pillars to make sure no one's there.
Title: Re: Crash prone 'modern roundabouts'
Post by: AlexandriaVA on August 05, 2016, 09:41:57 AM
Progress continutes. Carmel continues to build (http://fox59.com/2016/06/01/32-new-roundabouts-coming-to-carmel-timing-of-the-plan-outlined/)

Quote
"The vast majority of the money is going to improving our transportation system. Making it safer number one and then number two making it easier and quicker for people to get around," Mayor Jim Brainard said.

Quote
Mayor Brainard says the roundabouts make the city appealing.

"That's how we compete. That's how we attract business to the city of Carmel."
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 05, 2016, 09:59:53 AM
^The only two fatal crashes that occurred in Carmel in 2014 occurred at roundabouts.  What does Mayor Jim Brainard have to say about that?  Doesn't really fit into his PR campaign. 
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on August 05, 2016, 10:06:55 AM
^The only two fatal crashes that occurred in Carmel in 2014 occurred at roundabouts.  What does Mayor Jim Brainard have to say about that?  Doesn't really fit into his PR campaign.

It's time to stop blaming the roundabout for drunk and / or speeding drivers.   There will be impaired drivers regardless of the road topology.   The fact that these intersections were roundabouts had little to do with the incidents in question.
Title: Re: Crash prone 'modern roundabouts'
Post by: AlexandriaVA on August 05, 2016, 10:32:22 AM
^The only two fatal crashes that occurred in Carmel in 2014 occurred at roundabouts.  What does Mayor Jim Brainard have to say about that?  Doesn't really fit into his PR campaign.

What about 2015 crash data? My guess is that it doesn't support your position so you decided to omit it.

Yes, fine people of the heartland, roundabouts are fine and will not eat you or your children. There is more to driving than stoplights or four-way stops.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 05, 2016, 10:56:26 AM
Alcohol was a factor in one of the fatal Carmel crashes in 2014. According to the NHTSA, there were 9,967 people killed in alcohol-impaired-driving crashes in 2014.  This accounted for 31 percent of all motor vehicle traffic fatalities in the United States that year.  The point is alcohol is a contributing factor to a LOT of fatal crashes; whether they happen at a roundabout, signalized intersection, or on the freeway.   

The national numbers on roundabouts suggest that they reduce fatal crashes by 90%.  These numbers obviously include fatal crashes involving alcohol.  If Carmel had 2 fatal crashes at their 100 roundabouts, you would expect to see roughly 20 fatal crashes throughout the rest of the city (Carmel does have its fair share of signalized intersections still.. someone just posted an article where 32 more roundabouts are planned, many of which will be replacing signalized intersections).

What about 2015 crash data? My guess is that it doesn't support your position so you decided to omit it.
Yes, fine people of the heartland, roundabouts are fine and will not eat you or your children. There is more to driving than stoplights or four-way stops.

You are suggesting that the 2014 Carmel crash data isn’t statistically significant by itself.  Just think of the hundreds of thousands of miles driven on Carmel roads in 2014.  Yet the only fatal crashes happened at roundabouts which are supposedly the safest places to be driving.  How is it that nobody was killed by some drunk at a signalized intersection (yes, they still exist in Carmel!)?  Or could it be, just maybe, that roundabouts don't reduce fatal crashes as much as they want us to believe?
Title: Re: Crash prone 'modern roundabouts'
Post by: AlexandriaVA on August 05, 2016, 11:11:04 AM
I thought it was because roundabouts are too difficult for Midwesterners to negotiate (as in you don't drive over them, or stop and make a left or right hand turn, etc etc).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 05, 2016, 11:34:08 AM

What about 2015 crash data? My guess is that it doesn't support your position so you decided to omit it.
Yes, fine people of the heartland, roundabouts are fine and will not eat you or your children. There is more to driving than stoplights or four-way stops.

You are suggesting that the 2014 Carmel crash data isn’t statistically significant by itself.  Just think of the hundreds of thousands of miles driven on Carmel roads in 2014.  Yet the only fatal crashes happened at roundabouts which are supposedly the safest places to be driving.  How is it that nobody was killed by some drunk at a signalized intersection (yes, they still exist in Carmel!)?  Or could it be, just maybe, that roundabouts don't reduce fatal crashes as much as they want us to believe?

Problem is that road statistics - especially accident statistics - and especially fatal accident data - is usually statistically insignificant to begin with. If you have a 10% accident reduction from 100 to 90, all you can say is that there is no statistically significant difference. No DOT would ignore the change, though.
  Some multiyear national trends may go better than error bars, but most of it is... well, if you don't have the data you like - you have to like the data you have.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 05, 2016, 11:42:01 AM
I thought it was because roundabouts are too difficult for Midwesterners to negotiate (as in you don't drive over them, or stop and make a left or right hand turn, etc etc).

You might be onto something.  The Midwest states are highlighted yellow as defined by the US Census Bureau.  The pink circles represent roundabouts that have 3 circulating lanes on at least one approach.  These are some of the most complex roundabouts that have been built in the United States.  As you can see, the majority of the complex roundabouts are located in the Midwest (specifically Wisconsin & Michigan).  So are the roundabouts too difficult for Midwestern drivers, or are they just being asked to navigate roundabouts that are more complex than the rest of the country? 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/triplerbs_zpslnpx5k9e.png)

One interesting note… most of the regions in Wisconsin now have a moratorium on designing roundabouts with 3 circulating lanes.  Other state agencies should look closely at how triple lane roundabouts have evolved in Wisconsin before deciding to build a triple lane roundabout of their own.  In addition, several of the triple lane roundabouts in Michigan have since been downsized to only two-lanes with other roundabout downsizing planned (ie. Lee Road Roundabout).
Title: Re: Crash prone 'modern roundabouts'
Post by: AlexandriaVA on August 05, 2016, 11:46:29 AM
I thought Midwesterners like wide roads, so it would follow that the roundabouts should be wide as well.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 05, 2016, 11:52:42 AM
I thought Midwesterners like wide roads, so it would follow that the roundabouts should be wide as well.

That's a pretty good point. Wisconsin in particular seems to have a large number of divided highways, ripe for three lane roundabouts. Same for Michigan.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 05, 2016, 11:57:36 AM
Quote
The national numbers on roundabouts suggest that they reduce fatal crashes by 90%.  These numbers obviously include fatal crashes involving alcohol.  If Carmel had 2 fatal crashes at their 100 roundabouts, you would expect to see roughly 20 fatal crashes throughout the rest of the city...

No you wouldn't. Two issues with this:

You're looking at national numbers.  You're only looking at averages.  Not every single city, town, state, etc is going to see the same reduction.  In some states, there may be no reduction, in other states there could be a 100% reduction.  The *average* is a 90% reduction (at least what we're told).

And two, you can't take the number and say what the rest of the city/state should have had. If there were 0 DUI accidents at the roundabout (let's say that happened in 2015 because you ignored that data), then 90% would equal 0 DUI deaths in the rest of the city as well.  Is that true?  Probably not.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 05, 2016, 12:11:06 PM
And two, you can't take the number and say what the rest of the city/state should have had. If there were 0 DUI accidents at the roundabout (let's say that happened in 2015 because you ignored that data), then 90% would equal 0 DUI deaths in the rest of the city as well.  Is that true?  Probably not.

According to the Carmel, Indiana Police Department there was only 1 fatal crash in 2015 (and it did not occur at a roundabout).  I posted this data in chart form a few posts up, so I don’t see how I’m “ignoring”  the data.  I gave you the source of the data and the number of fatalities that occurred in 2015 already (see Reply #552).  You were welcome to look up the data for yourself instead of relying on me.

There was another fatal roundabout crash in March of 2016:
http://www.indystar.com/story/news/crime/2016/03/18/driver-killed-carmel-roundabout-crash/81967984/

This was the first fatal crash to occur in Carmel in 2016.  So over a 27 month period, 3 of the 4 fatal crashes that occurred in Carmel happened at roundabouts.  Either the rest of Carmel’s street network is incredibly safe, or their roundabouts are much more dangerous than the roundabouts analyzed in the national studies.  The third option is you can just try to discredit the numbers and make an ineffective argument that 27 months isn’t statistically significant.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 05, 2016, 12:18:09 PM
And two, you can't take the number and say what the rest of the city/state should have had. If there were 0 DUI accidents at the roundabout (let's say that happened in 2015 because you ignored that data), then 90% would equal 0 DUI deaths in the rest of the city as well.  Is that true?  Probably not.

According to the Carmel, Indiana Police Department there was only 1 fatal crash in 2015 (and it did not occur at a roundabout).  I posted this data in chart form a few posts up, so I don’t see how I’m “ignoring” the data.  I gave you the source of the data and the number of fatalities that occurred in 2015 already (see Reply #552).  You were welcome to look up the data for yourself instead of relying on me.

There was another fatal roundabout crash in March of 2016:
http://www.indystar.com/story/news/crime/2016/03/18/driver-killed-carmel-roundabout-crash/81967984/

This was the first fatal crash to occur in Carmel in 2016.  So over a 27 month period, 3 of the 4 fatal crashes that occurred in Carmel happened at roundabouts.  Either the rest of Carmel’s street network is incredibly safe, or their roundabouts are much more dangerous than the roundabouts analyzed in the national studies.  The third option is you can just try to discredit the numbers and make an ineffective argument that 27 months isn’t statistically significant.


The article stated he crashed into a concrete barrier in the middle of the roundabout.  As many other have pointed out in the past for similar accidents, that had nothing to do with a functionality failure of the roundabout. 

If anything, they need to figure out why drunks are flying thru roundabouts without turning.
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on August 05, 2016, 12:22:04 PM
I thought it was because roundabouts are too difficult for Midwesterners to negotiate (as in you don't drive over them, or stop and make a left or right hand turn, etc etc).

This reminds me that my grandad tried going "left" in a roundabout instead of going around the circle. The car in front of him had to stop, and the guy got out of his car and said "What are you doing?". My grandad said "I'm going over there!" :-D

He now has poor vision in his left eye, so you'll be glad to hear he no longer has his licence. :colorful:
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 05, 2016, 12:41:03 PM
The article stated he crashed into a concrete barrier in the middle of the roundabout.  As many other have pointed out in the past for similar accidents, that had nothing to do with a functionality failure of the roundabout. 

Use the same logic for someone who blows through a red light.  A driver blowing through a red light has nothing to do with the functionality failure of the traffic light.  But what is the point?  Ultimately, 3 out of 4 fatal crashes (75%) that have occurred in Carmel over a 27 month period happened at roundabouts.  This just doesn’t jive with what we have all been told by the experts.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 05, 2016, 12:44:11 PM
I missed the story where the experts told us how many fatals to expect in a 27 month period in Carmel.  Can you post that link?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 05, 2016, 02:02:15 PM
Are drink/driving collisions statistically significant? I mean, we want to prevent fatal collisions; roundabouts almost certainly have a better fatality record than intersections, simply because there's little in the way of right angles. But is there really anything we can do to meaningfully prevent said collisions? Short of further development in self-driving technology.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 05, 2016, 02:25:05 PM
It sounds like we want to ignore alcohol related fatalities in Carmel's roundabouts.  Fine, let's do that.  If you take out the roundabout fatalities that involved alcohol, you are still left with one fatal roundabout crash in 2014.  That means 50% of your fatalities in Carmel occurred at roundabouts over a 27 month period.  Carmel, the roundabout capital of the United States, where you are just as likely to die in a roundabout as anywhere else in the city. 
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on August 05, 2016, 07:55:35 PM
It sounds like we want to ignore alcohol related fatalities in Carmel's roundabouts.  Fine, let's do that.  If you take out the roundabout fatalities that involved alcohol, you are still left with one fatal roundabout crash in 2014.  That means 50% of your fatalities in Carmel occurred at roundabouts over a 27 month period.  Carmel, the roundabout capital of the United States, where you are just as likely to die in a roundabout as anywhere else in the city.
I live locally to the area and fear not for my safety.

And to add an interesting data point, just one hour ago I was driving through the roundabout near my house on the way home.  Because of the reduced number of conflict points I was able to pay 100% attention to the idiot driver arriving at a high rate of speed from the road to my right (I had already entered the roundabout).   I was easily able to stop and avoid the idiot who blew through the yield sign.   You will have idiot drivers with all types of intersections, from personal experience I find it far easier to avoid the idiots with a roundabout than with other types of intersections where the idiots are approaching from all directions.

Also this was a Westfield roundabout, not a Carmel roundabout.   The Carmel roundabouts tend to have much better designed approach roads to force the approaching drivers to slow.   Never the less since I was oriented with a clear view of the approaching car it was very easy for me to take action to avoid the collision.


Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on August 05, 2016, 08:32:37 PM
For contrast, here is a story (http://fox59.com/2016/08/02/woman-badly-injured-after-crash-involving-ips-school-bus-witnesses-tell-police-bus-ran-stop-sign/) about a similar situation at a four way stop where the bus driver disregarded the stop sign and took out an SUV, sending the driver of the SUV to intensive care.  Likely would have been a far different result at a roundabout, where the bus driver would have had to slow somewhat and the SUV would have had a clear view of the approaching bus.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on August 06, 2016, 01:54:37 AM
If you replace virtually all of the major intersections in a city with one of a particular type, virtually by definition nearly all of the deaths are going to be at that type of intersection, since people typically don't crash their cars in locations that aren't intersections (unless they fall asleep/have a heart attack at the wheel and run off the road).

Hence of course people are going to die in accidents in Carmel at roundabouts because there's almost no other type of intersection being used for major intersections in the city. If Carmel ripped them all out tomorrow and replaced them with all-way stops... all the deaths would now be at all-way stops (statistically there'd also be a lot more of them, although PDO crashes might go down).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 06, 2016, 12:06:55 PM
Hence of course people are going to die in accidents in Carmel at roundabouts because there's almost no other type of intersection being used for major intersections in the city.

A lot of traffic signals and 4-way stops exist in Carmel, Indiana.  Here is a map that shows the current breakdown of traffic signals, roundabouts, and all-way stops:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Carmel_zpsdca63r3q.png)
Green dots = roundabouts
Yellow dots = all-way stops
Red dots = traffic signals

As you can see, there is an even mix of roundabouts and non-roundabout intersections in the city.  The fact is there were 3 fatal crashes at Carmel’s roundabouts over a 27 month period (January 2014-March 2016).  Compare that to just one fatal crash at Carmel’s traffic signals and all-way stops during the same time period.  Carmel is the self-proclaimed roundabout capital of the country but it hasn’t had a good track record of preventing fatal crashes.  You have been better off driving through those “dangerous”  red dots.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on August 06, 2016, 01:31:25 PM

I drive in this area every day, and I feel far safer in the roundabouts then at the traffic signals and four way stops.  Looking forward to the addition of 30 more. (http://www.indystar.com/story/news/local/hamilton-county/2016/01/06/carmel-outlines-bold-roundabout-plan/78258640/)

I find it amusing that someone from outside the area needs to tell me how I'm in so much danger.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 06, 2016, 02:57:38 PM
^ I find it amusing that you think your personal anecdotal evidence means anything.  It doesn’t change the facts.  National studies have suggested that roundabouts reduce fatal crashes by 90% yet Carmel has had triple the number of fatal crashes at their roundabouts than their signalized intersections over a 27 month period.  Go ahead and dispute that, but come back with some meaningful facts and not just anecdotal BS.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on August 06, 2016, 04:34:30 PM
^ I find it amusing that you think your personal anecdotal evidence means anything.  It doesn’t change the facts.  National studies have suggested that roundabouts reduce fatal crashes by 90% yet Carmel has had triple the number of fatal crashes at their roundabouts than their signalized intersections over a 27 month period.  Go ahead and dispute that, but come back with some meaningful facts and not just anecdotal BS.

I understand that you hate roundabouts, but that's no reason to go into name calling.  My personal experience is not BS.  I drive these roads every day.   Feel free to disagree, but don't call other people's posts BS.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on August 06, 2016, 07:04:10 PM
Hence of course people are going to die in accidents in Carmel at roundabouts because there's almost no other type of intersection being used for major intersections in the city.

A lot of traffic signals and 4-way stops exist in Carmel, Indiana.  Here is a map that shows the current breakdown of traffic signals, roundabouts, and all-way stops:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Carmel_zpsdca63r3q.png)
Green dots = roundabouts
Yellow dots = all-way stops
Red dots = traffic signals

As you can see, there is an even mix of roundabouts and non-roundabout intersections in the city.  The fact is there were 3 fatal crashes at Carmel’s roundabouts over a 27 month period (January 2014-March 2016).  Compare that to just one fatal crash at Carmel’s traffic signals and all-way stops during the same time period.  Carmel is the self-proclaimed roundabout capital of the country but it hasn’t had a good track record of preventing fatal crashes.  You have been better off driving through those “dangerous”  red dots.

In a city with over 100 roundabouts, having only 3 fatal crashes in over 2 years actually disproves your point completely.  I live in Carmel too, and it is much safer, and traffic moves much better.  Also why didn't you look at the stats when there were much more signals in the city?  How about when US 31 was completely signaled?  Not to mention the many accidents that occur at 96th and keystone, a signal.  The remaining signals in Carmel are all at not very busy intersections, so accidents wouldn't happen frequently.  Also, one of the 3 was a drunk driver who tried to drive straight through one.  2 of the red dots aren't even in carmel, they're in another community called Home Place that the county maintains.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 06, 2016, 09:04:19 PM
Not to mention the many accidents that occur at 96th and Keystone, a signal.

According to the Carmel Police Department’s 2014 Annual report the intersection of 96th & Keystone ranked in the top 20 highest crash locations with 38 total crashes.  But the roundabout at 116th & Keystone had even more with 68 total crashes.  Keep in mind all the through traffic on Keystone bypasses the 116th & Keystone roundabout so you would think it would experience much lower traffic volumes than the at-grade signalized intersection of 96th & Keystone.  The roundabout at 116th & Keystone had 78% more crashes than the traffic signal at 96th & Keystone yet you only want to point out the high number of crashes happening at the traffic signal.  Why are you ignoring the high crash roundabouts in your city?

You also mentioned that people were drinking in some of the fatal roundabout crashes that occurred over the past few years.  Ok.  What's your point?  The national studies don't omit fatal crashes just because someone was drunk.  According to the national studies, they cite roundabouts should lead to a significant reduction in fatal crashes.  We aren't seeing a reduction in fatalities in Carmel.  There are plenty of high volume signalized intersections remaining in Carmel, yet over the past few years the majority of fatal crashes in Carmel have happened at roundabouts.  It's not what you would expect in the roundabout capital of America.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on August 06, 2016, 09:06:41 PM
Not to mention the many accidents that occur at 96th and Keystone, a signal.

According to the Carmel Police Department’s 2014 Annual report the intersection of 96th & Keystone ranked in the top 20 highest crash locations with 38 total crashes.  But the roundabout at 116th & Keystone had even more with 68 total crashes.  Keep in mind all the through traffic on Keystone bypasses the 116th & Keystone roundabout so you would think it would experience much lower traffic volumes than the at-grade signalized intersection of 96th & Keystone.  The roundabout at 116th & Keystone had 78% more crashes than the traffic signal at 96th & Keystone yet you only want to point out the high number of crashes happening at the traffic signal.  Why are you ignoring the high crash roundabouts in your city?

You also mentioned that people were drinking in some of the fatal roundabout crashes that occurred over the past few years.  Ok.  What's your point?  The national studies don't omit fatal crashes just because someone was drunk.  According to the national studies, they cite roundabouts should lead to a significant reduction in fatal crashes.  We aren't seeing a reduction in fatalities in Carmel.  There are plenty of high volume signalized intersections remaining in Carmel, yet over the past few years the majority of fatal crashes in Carmel have happened at roundabouts.  It's not what you would expect in the roundabout capital of America.
It's exactly what you would expect in a city where the primary feature is a roundabout. What's your point?
You are basically trying to say roundabouts should have no crashes. Signals have many safety issues that are well documented. You also don't even account traffic volume in your analysis.
You could put the same analysis with Indianapolis comparing it's many signals to the small amount of roundabouts and come to the opposite conclusion.
I'd also like to see before and after analysis to see if the signal had more or less crashes than the roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on August 06, 2016, 09:30:15 PM
Honestly, Jim Brainard has kind of lost his mind when it comes to roundabouts, there are some in the city that honestly don't need to be there at all, or the signal was fine. I feel he's more concerned about traffic flow than accidents.


Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 06, 2016, 11:03:23 PM
In a city with over 100 roundabouts, having only 3 fatal crashes in over 2 years actually disproves your point completely.  I live in Carmel too, and it is much safer, and traffic moves much better.  Also why didn't you look at the stats when there were much more signals in the city?  How about when US 31 was completely signaled?  Not to mention the many accidents that occur at 96th and keystone, a signal.  The remaining signals in Carmel are all at not very busy intersections, so accidents wouldn't happen frequently.  Also, one of the 3 was a drunk driver who tried to drive straight through one.  2 of the red dots aren't even in carmel, they're in another community called Home Place that the county maintains.

Honestly speaking, feeling safer has very little to do with actual safety. And they don't care about your beliefs in intensive care unit.

You are basically trying to say roundabouts should have no crashes. Signals have many safety issues that are well documented. You also don't even account traffic volume in your analysis.
Traffic lights problems may be well documented - but main problem of roundabouts is lack of understanding. Unfortunately, my strong impression is that US has few qualified traffic engineers left.
There were some people in Ireland trying to perform in-depth analysis of roundabouts. If you look at their publications, it is pretty clear where roundabouts actually belong and where they don't. But those publications seem way beyond comprehension level of those in charge.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on August 06, 2016, 11:31:31 PM
One of the bigger problems is that a lot of times, they're just a rubber stamp for what the mayor wants. And this is definitely true of Carmel. Even if they disagree with the mayor, they'll get overruled.

Nexus 6P

Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 07, 2016, 10:06:59 AM
Unfortunately, my strong impression is that US has few qualified traffic engineers left.

This statement would be a candidate for the most grossly inaccurate statement of the year.

Unless the roads you're driving on are collapsing on a daily basis, a traffic engineer created or signed off on that design that's keeping you safe.

If people can't negotiate roundabouts, that doesn't mean a traffic engineer messed up. It means the motorist messed up.

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 07, 2016, 10:14:18 AM
Unfortunately, my strong impression is that US has few qualified traffic engineers left.

This statement would be a candidate for the most grossly inaccurate statement of the year.

Unless the roads you're driving on are collapsing on a daily basis, a traffic engineer created or signed off on that design that's keeping you safe.

If people can't negotiate roundabouts, that doesn't mean a traffic engineer messed up. It means the motorist messed up.

There is structural engineering, and there is traffic engineering. I sure hope that the guy who designed the concrete of the bridge is not the one who designed stripping on it - you know, I cannot afford a helicopter...
Alternatively, if it is indeed same guy, I would pray that he knows structural things. As for stripping.. Well, bridge wouldn't collapse because of stripping....
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 07, 2016, 10:16:25 AM
Unfortunately, my strong impression is that US has few qualified traffic engineers left.

This statement would be a candidate for the most grossly inaccurate statement of the year.

Unless the roads you're driving on are collapsing on a daily basis, a traffic engineer created or signed off on that design that's keeping you safe.

If people can't negotiate roundabouts, that doesn't mean a traffic engineer messed up. It means the motorist messed up.

There is structural engineering, and there is traffic engineering. I sure hope that the guy who designed the concrete of the bridge is not the one who designed stripping on it - you know, I cannot afford a helicopter...
Alternatively, if it is indeed same guy, I would pray that he knows structural things. As for stripping.. Well, bridge wouldn't collapse because of stripping....

Put the stripping too close to the outer edge of the bridge, where the bridge height may fall under 13' 6", and have a truck come along...
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 07, 2016, 10:26:22 AM
Unfortunately, my strong impression is that US has few qualified traffic engineers left.

This statement would be a candidate for the most grossly inaccurate statement of the year.

Unless the roads you're driving on are collapsing on a daily basis, a traffic engineer created or signed off on that design that's keeping you safe.

If people can't negotiate roundabouts, that doesn't mean a traffic engineer messed up. It means the motorist messed up.

There is structural engineering, and there is traffic engineering. I sure hope that the guy who designed the concrete of the bridge is not the one who designed stripping on it - you know, I cannot afford a helicopter...
Alternatively, if it is indeed same guy, I would pray that he knows structural things. As for stripping.. Well, bridge wouldn't collapse because of stripping....

Put the stripping too close to the outer edge of the bridge, where the bridge height may fall under 13' 6", and have a truck come along...

Oh, OK.. Looks like I have to start saving for a helicopter...
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on August 07, 2016, 12:06:32 PM
Striping and signage isn't the problem, driver fuck ups are, hard to negotiate a roundabout when your texting or pokemon going.  I still see people trying to make a left turn in a roundabout (the wrong way) there is obvious signage, striping, fuck the damn median forces you to go right.  I think another problem is people incorrectly assuming where people in the roundabout are going and causing crashes, since you cannot signal in a roundabout, you have to wait.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on August 07, 2016, 12:07:33 PM
Unfortunately, my strong impression is that US has few qualified traffic engineers left.

This statement would be a candidate for the most grossly inaccurate statement of the year.

Unless the roads you're driving on are collapsing on a daily basis, a traffic engineer created or signed off on that design that's keeping you safe.

If people can't negotiate roundabouts, that doesn't mean a traffic engineer messed up. It means the motorist messed up.

I agree that statement is bullshit
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 07, 2016, 12:38:42 PM
Here on the west coast, some of the engineering schools are exceptionally difficult to get into, due to the recent influx of students from China. These students are exceptionally good at math, and present stiff competition when applying for an engineering program.

My point being, only the very best of the best are getting into engineering programs (at least out here).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 07, 2016, 12:49:22 PM
Here on the west coast, some of the engineering schools are exceptionally difficult to get into, due to the recent influx of students from China. These students are exceptionally good at math, and present stiff competition when applying for an engineering program.

My point being, only the very best of the best are getting into engineering programs (at least out here).
Best of best are applying for medical and MBA programs. That's where money is. 
And in any case, most roads we have today were designed 15 years ago and build 10 years ago by those who graduated  20-25 years ago and now think about retirement.  That is optimistic  scenario - average bridge age in US is 50 years, you know..
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 08, 2016, 11:36:12 AM
Yet another 3x2 crash prone roundabout has been downsized to a 2x2 roundabout.  The roundabout at 14 Mile & Farmington in West Bloomfield, Michigan was recently restriped to only include two circulating lanes through the roundabout.  According to MDOT, there were 36.43 average crashes before the roundabout was built and 67.33 average crashes after the roundabout (http://www.michigan.gov/documents/mdot/MDOT_Research_Report_RC1566_379286_7.pdf).  This follows the downsizing of other 3x2 roundabouts in the area including the one at Maple & Farmington and Maple & Drake. 

The remaining 3x2 roundabout in the area is the one at Pontiac Trail & M-5 (which was originally constructed in 2011).  The Pontiac Trail & M-5 roundabout was the highest crash prone intersection in the entire state of Michigan for 2015 with 186 total crashes (the intersection of 12 Mile & Telegraph ranked second with 132 crashes).
http://www.freep.com/story/news/local/michigan/oakland/2016/06/05/oakland-county-most-dangerous-intersection-state/85305668/
Title: Re: Crash prone 'modern roundabouts'
Post by: JCinSummerfield on August 08, 2016, 01:46:32 PM
Here in Toledo, OH, the intersection of Cherry, Berdan & Detroit Streets has been a roundabout for several months now.  Accidents occur daily.  What nobody has figured out is that the signage and the pavement striping don't match - at least entering from Cherry St.  I've also seen people make the wrong move for the lane they are in, so it's a combination of engineering issues and driver issues.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 08, 2016, 02:28:23 PM
Here in Toledo, OH, the intersection of Cherry, Berdan & Detroit Streets has been a roundabout for several months now.  Accidents occur daily.  What nobody has figured out is that the signage and the pavement striping don't match - at least entering from Cherry St.  I've also seen people make the wrong move for the lane they are in, so it's a combination of engineering issues and driver issues.

Wow, you’re not kidding.  A lot of people traveling on Cherry Street would assume that continuing on Detroit Avenue is the “straight”  movement while continuing onto Berdan Avenue would be the "turn" movement.  The pavement markings direct vehicles who entered the roundabout from the left lane to continue straight onto Detroit Avenue (and conversely, right lane traffic who enters the roundabout have to cross a solid white line to continue onto Berdan Ave).  I definitely could see myself getting confused driving this roundabout and i should know better.  I’m sure in the next few posts someone with a PHD in roundabout design will explain why the pavement markings and signage is correct, without considering how confusing it is to the average Joe.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Toledocon_zpsdfrdsnw7.png)

The most likely scenario is in a few years time, they will make the right most lane a right turn only lane and convert it to a 2x1 roundabout to limit confusion (and to alleviate the high crash rate).
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 08, 2016, 04:41:54 PM
Here in Toledo, OH, the intersection of Cherry, Berdan & Detroit Streets has been a roundabout for several months now.  Accidents occur daily.  What nobody has figured out is that the signage and the pavement striping don't match - at least entering from Cherry St.  I've also seen people make the wrong move for the lane they are in, so it's a combination of engineering issues and driver issues.

Wow, you’re not kidding.  A lot of people traveling on Cherry Street would assume that continuing on Detroit Avenue is the “straight”  movement while continuing onto Berdan Avenue would be the "turn" movement.  The pavement markings direct vehicles who entered the roundabout from the left lane to continue straight onto Detroit Avenue (and conversely, right lane traffic who enters the roundabout have to cross a solid white line to continue onto Berdan Ave).  I definitely could see myself getting confused driving this roundabout and i should know better.  I’m sure in the next few posts someone with a PHD in roundabout design will explain why the pavement markings and signage is correct, without considering how confusing it is to the average Joe.

http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Toledocon_zpsdfrdsnw7.png

This is why, under certain circumstances, I prefer no lane markings to confusing lane markings. If this roundabout didn't have any lane markings, traffic may be able to better interpret the through movement, but the way it's setup, through traffic has no chance: the movement becomes less of a straight-on movement, and more of a "merge then slight left", all because of the solid lane line.
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on August 08, 2016, 06:48:34 PM
Here in Toledo, OH, the intersection of Cherry, Berdan & Detroit Streets has been a roundabout for several months now.  Accidents occur daily.  What nobody has figured out is that the signage and the pavement striping don't match - at least entering from Cherry St.  I've also seen people make the wrong move for the lane they are in, so it's a combination of engineering issues and driver issues.

Wow, you’re not kidding.  A lot of people traveling on Cherry Street would assume that continuing on Detroit Avenue is the “straight”  movement while continuing onto Berdan Avenue would be the "turn" movement.  The pavement markings direct vehicles who entered the roundabout from the left lane to continue straight onto Detroit Avenue (and conversely, right lane traffic who enters the roundabout have to cross a solid white line to continue onto Berdan Ave).  I definitely could see myself getting confused driving this roundabout and i should know better.  I’m sure in the next few posts someone with a PHD in roundabout design will explain why the pavement markings and signage is correct, without considering how confusing it is to the average Joe.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Toledocon_zpsdfrdsnw7.png)

I'm struggling to see how someone could defend this, it just seems wrong to me! :pan:

The most likely scenario is in a few years time, they will make the right most lane a right turn only lane and convert it to a 2x1 roundabout to limit confusion (and to alleviate the high crash rate).

This would be the easiest way to solve the problem, and at least you wouldn't have to change that stripe in the roundabout. :-D

Ideally, they should have had Cherry St bend to the west before the roundabout to prevent the confusion about Detroit St being a "right turn". But maybe they didn't have the ROW?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 09, 2016, 08:21:33 AM
I'm struggling to see how someone could defend this, it just seems wrong to me! :pan:
Pretty obvious, if you zoom out, you can clearly see which road goes through and which is turning.
And if average Joe is so stupid that he cannot see the big picture while driving through, that is not engineer's problem!

However, honestly speaking, pre-roundabout layout which still shows on web maps, is not much better. I have hard time thinking of a good layout - really no straightforward solution, and local traffic pattern has to be taken into account. And overall area looks... messy. With lots of homes, lots of commute, and lots of NIMBYs.... 
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on August 09, 2016, 08:45:33 AM
I'm struggling to see how someone could defend this, it just seems wrong to me! :pan:
Pretty obvious, if you zoom out, you can clearly see which road goes through and which is turning.
And if average Joe is so stupid that he cannot see the big picture while driving through, that is not engineer's problem!.

I probably could have been more clear here, but I was referring to the solid white line in the roundabout. The sign on Cherry St says you can go straight or right, but the solid white line (next to the red car in the satellite image) suggests that you can only go right, since going straight would require you to cross a solid white line.

As to the problem of drivers thinking Cherry St to N Detroit Ave is "straight" instead of a right-turn, I can see both sides of the coin. And though I understand your point, the fact is (to a certain extent) we need to design roads for stupid drivers because many drivers are stupid. Especially when it comes to roundabouts (in North America anyway), as all the crash statistics in this thread prove.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 09, 2016, 08:53:32 AM
I'm struggling to see how someone could defend this, it just seems wrong to me! :pan:
Pretty obvious, if you zoom out, you can clearly see which road goes through and which is turning.
And if average Joe is so stupid that he cannot see the big picture while driving through, that is not engineer's problem!.

I probably could have been more clear here, but I was referring to the solid white line in the roundabout. The sign on Cherry St says you can go straight or right, but the solid white line (next to the red car in the satellite image) suggests that you can only go right, since going straight would require you to cross a solid white line.

If anyone commenting missed that, then they need to turn in their roadgeek license!  :spin: 
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 09, 2016, 10:31:18 AM
I'm struggling to see how someone could defend this, it just seems wrong to me! :pan:
Pretty obvious, if you zoom out, you can clearly see which road goes through and which is turning.
And if average Joe is so stupid that he cannot see the big picture while driving through, that is not engineer's problem!.

I probably could have been more clear here, but I was referring to the solid white line in the roundabout. The sign on Cherry St says you can go straight or right, but the solid white line (next to the red car in the satellite image) suggests that you can only go right, since going straight would require you to cross a solid white line.

As to the problem of drivers thinking Cherry St to N Detroit Ave is "straight" instead of a right-turn, I can see both sides of the coin. And though I understand your point, the fact is (to a certain extent) we need to design roads for stupid drivers because many drivers are stupid. Especially when it comes to roundabouts (in North America anyway), as all the crash statistics in this thread prove.

I would interpret "straight" on that lane as "Straight to N Detroit", and "right" - as "right to Emmet st. off N Detroit".
If they had that in mind .. but probably not - sign at the roundabout entry shows that right lane goes to Detroit and Berdan, and left.... to Berdan and Detroit as well.

Talk about levels of confusion!
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on August 09, 2016, 10:54:26 AM
I'm struggling to see how someone could defend this, it just seems wrong to me! :pan:
Pretty obvious, if you zoom out, you can clearly see which road goes through and which is turning.
And if average Joe is so stupid that he cannot see the big picture while driving through, that is not engineer's problem!.

I probably could have been more clear here, but I was referring to the solid white line in the roundabout. The sign on Cherry St says you can go straight or right, but the solid white line (next to the red car in the satellite image) suggests that you can only go right, since going straight would require you to cross a solid white line.

As to the problem of drivers thinking Cherry St to N Detroit Ave is "straight" instead of a right-turn, I can see both sides of the coin. And though I understand your point, the fact is (to a certain extent) we need to design roads for stupid drivers because many drivers are stupid. Especially when it comes to roundabouts (in North America anyway), as all the crash statistics in this thread prove.

I would interpret "straight" on that lane as "Straight to N Detroit", and "right" - as "right to Emmet st. off N Detroit".
If they had that in mind .. but probably not - sign at the roundabout entry shows that right lane goes to Detroit and Berdan, and left.... to Berdan and Detroit as well.

Talk about levels of confusion!

Interesting, Google Maps doesn't show Emmet St connecting to N Detroit Ave, but this GSV from Sept 2015 suggests it does. The bolded sentence above is another good point of potential motorist confusion!

(http://i.imgur.com/MVmEU4c.png)
(http://i.imgur.com/XoLP2Dp.png)

Also, Google Maps shows (a second Cherry St?) connecting to the roundabout at W Manhattan Blvd going the wrong way!

(http://i.imgur.com/jsebqb9.png)

But GSV confirms this is an error and that this street doesn't connect to the roundabout.

(http://i.imgur.com/Pm3vklV.png)

The outdated satellite imagery doesn't help with all this confusion :colorful:
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 09, 2016, 10:58:35 AM

(http://i.imgur.com/Pm3vklV.png)


Uh....................
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on August 09, 2016, 11:26:49 AM

(http://i.imgur.com/Pm3vklV.png)


Uh....................

I'm not sure why you're confused. I posted the GSV image to show that the street in the background with the houses on it doesn't connect to the roundabout (there's grass between the two), whereas Google Maps seems to show them overlapping.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on August 09, 2016, 12:22:49 PM

(http://i.imgur.com/Pm3vklV.png)


Uh....................

I'm not sure why you're confused. I posted the GSV image to show that the street in the background with the houses on it doesn't connect to the roundabout (there's grass between the two), whereas Google Maps seems to show them overlapping.

I'm confused by cars driving in opposite directions on the same roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on August 09, 2016, 12:25:28 PM

(http://i.imgur.com/Pm3vklV.png)


Uh....................

I'm not sure why you're confused. I posted the GSV image to show that the street in the background with the houses on it doesn't connect to the roundabout (there's grass between the two), whereas Google Maps seems to show them overlapping.

I'm confused by cars driving in opposite directions on the same roundabout.

Holy crap, I guess that's what he was referring to! :-D I should post that in the Google Street View thread

UPDATE: Here's my post with more views of the wrong way driver: https://www.aaroads.com/forum/index.php?topic=2648.msg2165328#msg2165328 (https://www.aaroads.com/forum/index.php?topic=2648.msg2165328#msg2165328)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 09, 2016, 12:26:46 PM

(http://i.imgur.com/Pm3vklV.png)


Uh....................

I'm not sure why you're confused. I posted the GSV image to show that the street in the background with the houses on it doesn't connect to the roundabout (there's grass between the two), whereas Google Maps seems to show them overlapping.

FOr me new alignment shows up when I untilt the image, old one with tilted image.

And Emmet street is clearly connected to Detroit just off roundabout, maybe 70 feet down the street.
https://www.google.com/maps/place/Toledo,+OH/@41.6863319,-83.5568115,19z/data=!3m1!1e3!4m2!3m1!1s0x883b872dfc1e4e79:0x7c3cc89f453ac345
https://www.google.com/maps/place/Toledo,+OH/@41.6862413,-83.5560435,3a,66.8y,90t/data=!3m4!1e1!3m2!1sohHAkXupMp-umJA_rgki5w!2e0!4m2!3m1!1s0x883b872dfc1e4e79:0x7c3cc89f453ac345
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 09, 2016, 01:26:19 PM

(http://i.imgur.com/Pm3vklV.png)


Uh....................

I'm not sure why you're confused. I posted the GSV image to show that the street in the background with the houses on it doesn't connect to the roundabout (there's grass between the two), whereas Google Maps seems to show them overlapping.

I'm confused by cars driving in opposite directions on the same roundabout.

Holy crap, I guess that's what he was referring to! :-D

That's exactly what I was referring to!!!!
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 09, 2016, 04:07:17 PM
What if you just removed the confusing markings? Install overhead signage that clearly shows the straight movement as being a "slight right then left". Or even change the arrows so that they point slightly left instead of straight.

I don't think you need to remove any lanes to fix the problem here. Although apparently we need more right-facing chevrons, because there's evidently people out there that still don't know which way to go around a roundabout....

(http://i.imgur.com/NdJeFct.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 09, 2016, 04:31:47 PM
What if you just removed the confusing markings? Install overhead signage that clearly shows the straight movement as being a "slight right then left". Or even change the arrows so that they point slightly left instead of straight.

I don't think you need to remove any lanes to fix the problem here. Although apparently we need more right-facing chevrons, because there's evidently people out there that still don't know which way to go around a roundabout....

Actually I was staring at the map trying to visualize traffic patterns.. Looks like there is a massive amount of rebuild going on in the area - I-75 bridge, those two roundabouts, C/D road to I-75. And area looks mostly residential, with lots of homes. Commuter traffic struggling during roadwork in crazy traffic pattern?
Google also shows another roundabout in progress about 1/4 mile west.. Looks like a major realignment of everything..
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on August 09, 2016, 04:42:47 PM
What if you just removed the confusing markings? Install overhead signage that clearly shows the straight movement as being a "slight right then left". Or even change the arrows so that they point slightly left instead of straight.

Most non-signalized 2x2 or 2x1 roundabouts in the UK don't have lane markings, for what it's worth.

Quote
I don't think you need to remove any lanes to fix the problem here. Although apparently we need more right-facing chevrons, because there's evidently people out there that still don't know which way to go around a roundabout....

On the other hand, chevrons (along with a mandatory turn one-way arrow) are probably more, not less, emphasized in the UK (except mini-roundabouts, for obvious reasons) than most US installations. Using a W1-6 on top of the chevrons would probably get the point across better, but for some reason MUTCD doesn't specify that.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 09, 2016, 05:40:51 PM
It would be interesting to see if this design would work or if the traffic volumes turning onto Berdan Ave are too high (requiring the dual circulating lanes).....

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/rbredesign_zpsbffmrhx1.png)

Title: Re: Crash prone 'modern roundabouts'
Post by: johndoe on August 09, 2016, 06:55:39 PM
I have a cheaper fix =)
(http://i63.tinypic.com/sdimue.jpg)

What if you just removed the confusing markings?
Do you find the circulating roadway markings/arrows more confusing than the approach fishhooks?  Usually the normal arrows in the circulating roadway align nicely with the exit (unless the angle between legs is big like this), but it makes a lot of sense to me that "through"="exiting roundabout" and "left"="circulating roundabout" but there's a decent chance I've looked at these things too long =)  I guess I've never understood the desire to remove circulating markings. 

IMO if anything is confusing it's the fishhooks.  We've had lots of debate in our office about their effectiveness!  Some people think the angle between the arrows is most important, while others think it's more about demonstrating which lane can exit at which departure (for instance in the left lane you cannot use the FIRST exit but you can use the second and third).  Just be glad this is only four-legged; things get really weird with a fifth leg!
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on August 10, 2016, 09:44:00 AM
I'm struggling to see how someone could defend this, it just seems wrong to me! :pan:
Pretty obvious, if you zoom out, you can clearly see which road goes through and which is turning.
And if average Joe is so stupid that he cannot see the big picture while driving through, that is not engineer's problem!.

I probably could have been more clear here, but I was referring to the solid white line in the roundabout. The sign on Cherry St says you can go straight or right, but the solid white line (next to the red car in the satellite image) suggests that you can only go right, since going straight would require you to cross a solid white line.

As to the problem of drivers thinking Cherry St to N Detroit Ave is "straight" instead of a right-turn, I can see both sides of the coin. And though I understand your point, the fact is (to a certain extent) we need to design roads for stupid drivers because many drivers are stupid. Especially when it comes to roundabouts (in North America anyway), as all the crash statistics in this thread prove.

I would interpret "straight" on that lane as "Straight to N Detroit", and "right" - as "right to Emmet st. off N Detroit".
If they had that in mind .. but probably not - sign at the roundabout entry shows that right lane goes to Detroit and Berdan, and left.... to Berdan and Detroit as well.

Talk about levels of confusion!

Interesting, Google Maps doesn't show Emmet St connecting to N Detroit Ave, but this GSV from Sept 2015 suggests it does. The bolded sentence above is another good point of potential motorist confusion!

(http://i.imgur.com/MVmEU4c.png)
(http://i.imgur.com/XoLP2Dp.png)

Also, Google Maps shows (a second Cherry St?) connecting to the roundabout at W Manhattan Blvd going the wrong way!

(http://i.imgur.com/jsebqb9.png)

But GSV confirms this is an error and that this street doesn't connect to the roundabout.

(http://i.imgur.com/Pm3vklV.png)

The outdated satellite imagery doesn't help with all this confusion :colorful:

I've corrected the geometry on the second cherry street to the left in mapmaker (it wasn't connected to the roundabout, just drawn too far to the right).   I also removed the building outline that was sitting on top of the roundabout and cleaned up some of the other geometry.   Also connected Emmet Street and split the lanes on North Detroit north of the roundabout.   Will require google moderation for the final touches to set the new lanes to the right highway priority.

Give it 24 hours for everything to show up on maps.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 10, 2016, 10:24:38 AM
What if you just removed the confusing markings? Install overhead signage that clearly shows the straight movement as being a "slight right then left". Or even change the arrows so that they point slightly left instead of straight.

Most non-signalized 2x2 or 2x1 roundabouts in the UK don't have lane markings, for what it's worth.

Most NJ traffic circles don't have lane markings either.  People do have a tendency to creep into other lanes when they're not supposed to.  Plenty of horn honking.  And yet, they don't seem to have the issues many others report at these fully parked roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 10, 2016, 10:52:10 AM
Here is a good streetview compilation of the problem.  In the very first picture there is a sign that directs drivers what lane to be in depending if they want to go on Detroit Ave or Berdan Ave.  Track the white Lincoln Towncar through the roundabout.  The white Lincoln correctly follows the signage and continues onto Berdan Ave (although they have to cross a solid white line inside the roundabout to get there).  Now track the red Camero who was at one point directly beside the white Lincoln.  Both the red Camero and the vehicle behind them incorrectly continues onto Detroit Avenue.  This is your problem.. drivers in the left lane are exiting onto Detroit Ave and they shouldn't be. 
 
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/trackcab2_zpsxn2rhqdo.png)

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/trackredcamero2_zpsbbjjvn32.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 10, 2016, 11:33:40 AM
What if you just removed the confusing markings? Install overhead signage that clearly shows the straight movement as being a "slight right then left". Or even change the arrows so that they point slightly left instead of straight.

Most non-signalized 2x2 or 2x1 roundabouts in the UK don't have lane markings, for what it's worth.

Most NJ traffic circles don't have lane markings either.  People do have a tendency to creep into other lanes when they're not supposed to.  Plenty of horn honking.  And yet, they don't seem to have the issues many others report at these fully parked roundabouts.

I’m not convinced eliminating lane markings would make roundabouts any safer.  There was a notorious traffic circle in Augusta, Maine known as Cony Circle which averaged over 100 crashes per year.  The traffic circle had no pavement markings and it was basically a free-for-all for drivers.  It was the highest crash prone intersection in the entire state of Maine. 

They decided they had to do something about it and reconfigured the traffic circle with modern roundabout standards in 2008.  They striped the circle as a spiral roundabout and reconfigured the entry flares slightly, but the biggest change was the pavement markings themselves.  After the change, total accidents dropped by 50% and injury accidents dropped by 68%.  Even with these impressive numbers, the newly configured roundabout is still the 3rd highest crash location in Maine.   The crash problem didn’t go away, but they definitely made it better with the striping.

http://www.centralmaine.com/2011/08/11/cony-circle-accidents-down_2011-08-10/
http://www.wgme.com/images/DANGEROUS%20ROADWAY%20INTERSECTIONS.pdf

Cony Circle:  Pre-2008
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/08-Untitled_zpshnpikktf.png)

Cony Circle:  Post-2008
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/15Untitled_zpsl7d1abyq.png)

EDIT:  To be fair, i may be underestimating the effects the geometric changes had on Cony Circle in reducing the total crashes.  I'd be all for taking a modern roundabout that has averaged 100 crashes a year and eliminate the signage and pavement markings just to see what happens (don't do any other changes, just remove all the markings inside the roundabout).  At the very least it would be fun to see the results of that study.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 11, 2016, 04:38:29 PM
According to PUBLICATION NO. FHWA-SA-15-072, there have been 46 fatal roundabout crashes between 2005 and 2013.  Here’s a KMZ file that maps every fatal roundabout crash:

http://www.mediafire.com/download/adpyqy0yh6k3h1e/Fatal_Roundabout_crashes_%282005-2013%29.kmz

Two roundabouts had multiple fatal crashes during the 9 year analysis period:
Moore Chapel Rd./I-485 NB Ramps in Charlotte, NC: 2 fatal crashes
US 62/Big Tree Rd. in Hamburg, NY: 2 fatal crashes

Here are some statistics regarding the fatal roundabout crashes:
*83% involved single-vehicle crashes.
*52% involved impaired driving. 
*56% were classified as speed involved crashes (at least two fatal crashes involved vehicles exceeding 100 mph). 
*46% involved motorcycles.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on August 11, 2016, 06:18:56 PM
Those stats sounds reasonable -- you most likely have to be driving impaired, speeding, or doing something else really stupid to get killed in a roundabout.  The high percentage of single vehicle crashes speaks volumes.   Good find on the stats.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 11, 2016, 06:51:28 PM
Those stats sounds reasonable -- you most likely have to be driving impaired, speeding, or doing something else really stupid to get killed in a roundabout.  The high percentage of single vehicle crashes speaks volumes.   Good find on the stats.
Well, lets compare to general statistics
US average fatal crashes: 56% single vehicle, 32% impaired drivers.
DC and RI (I would use those as very urban references) have higher single-vehicle rates - 70 and 77% respectively. Drunk - 47% and 33%.

I would say numbers are not way off national average, considering roundabouts are mostly on urban roads.
I don't know what excessive number of motorcycles mean (13% national, 9 and 14 DC/RI) likely  visibility problems on roundabouts?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 11, 2016, 07:03:10 PM
^The study mentions the disproportionately high number of motorcycle fatalities at roundabouts.  All it takes is a motorcyclist to clip the curbing in the roundabout and the rider goes flying. 
 
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on August 12, 2016, 02:56:54 AM
^The study mentions the disproportionately high number of motorcycle fatalities at roundabouts.  All it takes is a motorcyclist to clip the curbing in the roundabout and the rider goes flying.

Indeed.  I've studied the accident statistics for a bunch of roundabouts in Oregon and have found that even low-volume roundabouts, involving roads with 25mph speed limits in largely residential areas, have had high-severity injury accidents.  In most cases, it's been a motorcyclist.  Having driven through a couple of roundabouts on my 49cc Honda Metropolitan scooter (including this one (https://www.google.com/maps/place/N+Garden+Way,+Eugene,+OR+97401/@44.0610691,-123.0519722,203m/data=!3m1!1e3!4m5!3m4!1s0x54c0e1ec32c4dabd:0x9c100d9127b4be6f!8m2!3d44.0669436!4d-123.05194) in Eugene), they're really quite awkward on that mode of transportation.  Lean too far or not far enough to make all those corners, and there's a ton of curbing all over the place with your name on it.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 12, 2016, 06:05:31 AM
I can also see motorcyclists taking these roundabouts way too fast, as sort of their own obstacle course.  A motorcyclist dropping their bike at slow speeds generally isn't going to be fatal (helmets certainly do help though!).  And in terms of cornering, a roundabout and a general left or right turn has approximately the same radius.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 12, 2016, 11:04:14 AM
A motorcyclist approaching a roundabout suddenly feels like Valentino Rossi... minus the talent:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/motorrb_zpskybeizwp.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on August 12, 2016, 01:14:49 PM
I have a cheaper fix =)
(http://i63.tinypic.com/sdimue.jpg)

I would change very little about these two roundabouts.  The signage is excellent, spelling out which lane is for which street.  And I'm a fan of Alberta striping.  The only two things I would do are...

(1) Extend your suggestion to all points:  remove all solid stripes from within the circulating roadways.
(2) Make all entries and exits the same number of lanes; I believe this helps alleviate drier confusion.

(http://i1092.photobucket.com/albums/i410/kphoger/Toledo%20roundabout_zpsf40vxbvo.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 15, 2016, 10:14:21 AM
I would change very little about these two roundabouts.  The signage is excellent, spelling out which lane is for which street.  And I'm a fan of Alberta striping.  The only two things I would do are...

(1) Extend your suggestion to all points:  remove all solid stripes from within the circulating roadways.
(2) Make all entries and exits the same number of lanes; I believe this helps alleviate drier confusion.

(http://i1092.photobucket.com/albums/i410/kphoger/Toledo%20roundabout_zpsf40vxbvo.png)

In the Streetview montage posted previously, there are multiple vehicles in the left-hand lane that incorrectly exit at Detroit Ave (the red Camero and the vehicle behind it).  I like your drawing (and am curious about what program you used) but I don’t see how this would address this incorrect lane usage problem.  You had said the signage is excellent yet drivers seem to be disregarding it.  It’s amazing that a moment in time on streetview captured a wrong way driver and two incorrect lane usages.  I wonder how many mess ups you would see observing the roundabout for a few hours as opposed to looking at a few streetview images. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on August 15, 2016, 10:49:02 AM
^^  I just use MS Paint, because I'm not tech-savvy.  And I don't think it would address the lane usage problem.  My opinion is that it's been done almost as perfectly as you could do it, yet people are still being stupid.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 15, 2016, 11:09:52 AM
^Thanks.  I use Google Earth to add polygons and paths for my drawings but i find it finicky to work with.  I'll try MS Paint sometime.  I agree that if people are going to disregard the signage that it's hard to design for that.  I personally feel the signage doesn't match the natural instinct drivers have at this roundabout (for whatever reason drivers feel like they should be allowed to exit onto Detroit Ave from the left-most lane). 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on August 15, 2016, 05:16:16 PM
(for whatever reason drivers feel like they should be allowed to exit onto Detroit Ave from the left-most lane). 

I think the geometry of the movement makes it feel like a straight-through movement rather than a turning movement. Two options to correct this:

1) Swing the approach away from center so it meets the roundabout more obliquely, thereby making the right turn more of a right turn.

2) Reduce the diameter of the whole roundabout so all approaches are physically closer to their neighboring exits, thereby highlighting the existence of the roundabout and making that movement feel less like 'staying on the main road:.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 19, 2016, 01:43:31 AM
The 116th Street & Spring Mill Road roundabout in Carmel was originally constructed as a single lane roundabout around 2005.  According to the Carmel Police Department’s Annual reports, it never made the top crash locations when it was a single-lane roundabout.  Then in 2013 the roundabout was converted to a 2x2 multi-lane roundabout.  In 2014 the roundabout was the 3rd highest crash location in the city with 51 total crashes.  If you look at historical imagery, the surrounding geometry of the area didn’t change much (Spring Mill Road is still 2-lanes north & south of the roundabout and 116th Street is 2-lanes west of the roundabout).  Since there wasn’t a significant increase in capacity along the roads surrounding the roundabout, it’s hard to argue that there was a significant increase in traffic volumes that would justify the increase in total crashes.  The more likely scenario is that drivers are having more trouble navigating the multi-lane roundabout.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/CarmelSpringMill_zpsszypdosv.png)


The roundabout at 116th & Spring Mill Road has experienced a significant spike in total crashes since it was converted to a 2x2 multi-lane roundabout a few years ago.  But there are also injury accidents occurring at the roundabout.  Just a few months ago 6 people were injured, 3 critically, when a car crashed at the roundabout:

http://wishtv.com/2016/05/31/police-investigate-serious-one-vehicle-accident-in-carmel/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 19, 2016, 11:34:05 AM
Woodward Avenue in Detroit runs for roughly 27 miles from Pontiac to downtown and is one of the main arterials in the city.  There is a big push for mass transit along Woodward and SEMCOG recently published a 112-page report discussing the rapid transit alternatives being considered.  Included in the report is a list of the most crash prone intersections along the Woodward corridor (there are roughly 70 signalized intersections along Woodward):
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Untitled001_zpszk0n43df.png)
http://www.woodwardanalysis.com/pdfs/20150706_woodwardAA_LPA_FINAL.pdf

I thought it would be fun to include a similar comparison for the critical crash roundabouts in Carmel, Indiana.  I couldn’t find accurate ADT data for the roundabouts in question so I estimated them all at 35,000 ADT.  The highest capacity roundabouts in America rarely see ADT volumes exceed 50000 and these Carmel roundabouts don’t have that much capacity (ie. not one roundabout in Carmel has triple circulating lanes).  Carmel has focused mainly on single-lane roundabouts, which is why the city can spout off their great city wide safety record.  But the fact is the few 2x2 multi-lane roundabouts that have been built in Carmel have not performed very well.  City leaders conveniently ignore this fact.
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Untitled002_zpseskcszkf.png)

Notice how the average crash rate at these 2x2 multi-lane roundabouts in Carmel are higher than the intersections along the Woodward corridor?  And if you want to ignore safety for a second and focus entirely on efficiency, let’s have a little test.  Someone drive 20 miles along the surface streets of Carmel and I’ll drive 20 miles down Woodward and we’ll see who gets to their destination first.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on August 19, 2016, 01:02:05 PM
The 116th Street & Spring Mill Road roundabout in Carmel was originally constructed as a single lane roundabout around 2005.  According to the Carmel Police Department’s Annual reports, it never made the top crash locations when it was a single-lane roundabout.  Then in 2013 the roundabout was converted to a 2x2 multi-lane roundabout.  In 2014 the roundabout was the 3rd highest crash location in the city with 51 total crashes.  If you look at historical imagery, the surrounding geometry of the area didn’t change much (Spring Mill Road is still 2-lanes north & south of the roundabout and 116th Street is 2-lanes west of the roundabout).  Since there wasn’t a significant increase in capacity along the roads surrounding the roundabout, it’s hard to argue that there was a significant increase in traffic volumes that would justify the increase in total crashes.  The more likely scenario is that drivers are having more trouble navigating the multi-lane roundabout.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/CarmelSpringMill_zpsszypdosv.png)


The roundabout at 116th & Spring Mill Road has experienced a significant spike in total crashes since it was converted to a 2x2 multi-lane roundabout a few years ago.  But there are also injury accidents occurring at the roundabout.  Just a few months ago 6 people were injured, 3 critically, when a car crashed at the roundabout:

http://wishtv.com/2016/05/31/police-investigate-serious-one-vehicle-accident-in-carmel/

You've once again quoted a single vehicle incident as a problem with the roundabout.   If an idiot driver in the middle of the night runs off the road at high speed, how is that the roundabout's fault?  If I remember correctly from the news reports at the time this crash was not even in the roundabout - the intersection was simply given in the news story as a nearby reference point.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 19, 2016, 02:12:17 PM
The 116th Street & Spring Mill Road roundabout in Carmel was originally constructed as a single lane roundabout around 2005.  According to the Carmel Police Department’s Annual reports, it never made the top crash locations when it was a single-lane roundabout.  Then in 2013 the roundabout was converted to a 2x2 multi-lane roundabout.  In 2014 the roundabout was the 3rd highest crash location in the city with 51 total crashes.  If you look at historical imagery, the surrounding geometry of the area didn’t change much (Spring Mill Road is still 2-lanes north & south of the roundabout and 116th Street is 2-lanes west of the roundabout).  Since there wasn’t a significant increase in capacity along the roads surrounding the roundabout, it’s hard to argue that there was a significant increase in traffic volumes that would justify the increase in total crashes.  The more likely scenario is that drivers are having more trouble navigating the multi-lane roundabout.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/CarmelSpringMill_zpsszypdosv.png)


The roundabout at 116th & Spring Mill Road has experienced a significant spike in total crashes since it was converted to a 2x2 multi-lane roundabout a few years ago.  But there are also injury accidents occurring at the roundabout.  Just a few months ago 6 people were injured, 3 critically, when a car crashed at the roundabout:

http://wishtv.com/2016/05/31/police-investigate-serious-one-vehicle-accident-in-carmel/

You've once again quoted a single vehicle incident as a problem with the roundabout.   If an idiot driver in the middle of the night runs off the road at high speed, how is that the roundabout's fault?  If I remember correctly from the news reports at the time this crash was not even in the roundabout - the intersection was simply given in the news story as a nearby reference point.
Roundabouts require much more attention to the road compared to regular intersection.
And people may be not in their top shape while driving - coming home after long shift, sleepless night, not feeling well etc. It is part of engineer job to design things so that they accommodate imperfect driving. Otherwise, we would have 104" lanes on highway (102" maximum width + whooping 2" clearance on each side). FOr some reason, 12'=144" is a typical value for highway...
So if you cannot design roads safely -  we have some janitor positions open over here, feel free to apply.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 19, 2016, 02:54:43 PM
You've once again quoted a single vehicle incident as a problem with the roundabout.   If an idiot driver in the middle of the night runs off the road at high speed, how is that the roundabout's fault?  If I remember correctly from the news reports at the time this crash was not even in the roundabout - the intersection was simply given in the news story as a nearby reference point.

I quoted that there were 51 total crashes at the 116th & Spring Mill roundabout in 2014.  In 2013 there were 15 or fewer crashes at the roundabout (it didn’t rank in the top 20 high crash location in 2013... the 20th highest had 15 crashes).  When total crashes nearly triple from the year prior, you got to scratch your head and ask why.   The likely reason is because the city added a circulating lane at the roundabout and drivers are now having trouble navigating the multi-lane roundabout. 

The 116th & Spring Mill's roundabout is an interesting case study because it’s comparing the crash data of the roundabout when it was a single-lane roundabout to the crashes that are occurring now that it’s a multi-lane roundabout.  Do you want a roundabout that has 15 crashes a year or one that has 51 crashes a year?  The roundabout currently has an estimated crash rate of 3.99; nearly double what you want to see as a traffic engineer.  The estimated crash rate of the 116th & Keystone roundabout is even worse at over 5.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 19, 2016, 03:06:38 PM
^Put another way, this intersection at Woodward & 10 Mile has fewer total crashes than the roundabout at 116th & Spring Mill Road in Carmel.

(https://upload.wikimedia.org/wikipedia/commons/8/87/Interstate_696_and_M-1_aerial.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on August 19, 2016, 05:19:24 PM
You've once again quoted a single vehicle incident as a problem with the roundabout.   If an idiot driver in the middle of the night runs off the road at high speed, how is that the roundabout's fault?  If I remember correctly from the news reports at the time this crash was not even in the roundabout - the intersection was simply given in the news story as a nearby reference point.

I quoted that there were 51 total crashes at the 116th & Spring Mill roundabout in 2014.  In 2013 there were 15 or fewer crashes at the roundabout (it didn’t rank in the top 20 high crash location in 2013... the 20th highest had 15 crashes).  When total crashes nearly triple from the year prior, you got to scratch your head and ask why.   The likely reason is because the city added a circulating lane at the roundabout and drivers are now having trouble navigating the multi-lane roundabout. 

The 116th & Spring Mill's roundabout is an interesting case study because it’s comparing the crash data of the roundabout when it was a single-lane roundabout to the crashes that are occurring now that it’s a multi-lane roundabout.  Do you want a roundabout that has 15 crashes a year or one that has 51 crashes a year?  The roundabout currently has an estimated crash rate of 3.99; nearly double what you want to see as a traffic engineer.  The estimated crash rate of the 116th & Keystone roundabout is even worse at over 5.


I think the issue is that you used scientific data to compare total crashes, but then you picked a news article to support your analysis of injury crashes.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 19, 2016, 05:51:44 PM
I think the issue is that you used scientific data to compare total crashes, but then you picked a news article to support your analysis of injury crashes.

I don't know of a good resource that breaks down detailed intersection crashes in Carmel by level of injury.  The Carmel Police Department's annual reports only list the total crashes for the top crash locations.  I wish there was a publicly accessible website where you could look up detailed crash information by intersection.  Then independent analysis could be done to support or discredit any reports published by the City of Carmel.  I do know that 3 out of the last 4 fatal crashes in Carmel have occurred at roundabouts.  Keep in mind that there are roughly the same number of traffic signals as there are roundabouts in Carmel; yet 75% of the fatalities over the past few years have happened at Carmel's incredibly "safe" roundabouts. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 19, 2016, 06:44:22 PM
Keep in mind that there are roughly the same number of traffic signals as there are roundabouts in Carmel; yet 75% of the fatalities over the past few years have happened at Carmel's incredibly "safe" roundabouts.

How much traffic passes through the roundabouts, compared to the signals? I've always maintained that the number of collisions is, more often than not, a factor of the amount of traffic going through the intersection. And to be clear, I'm not suggesting that all busy intersections have high amounts of collisions. It just seems to me that busier intersections have more collisions than quieter ones.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 19, 2016, 08:15:20 PM
I've always maintained that the number of collisions is, more often than not, a factor of the amount of traffic going through the intersection. And to be clear, I'm not suggesting that all busy intersections have high amounts of collisions. It just seems to me that busier intersections have more collisions than quieter ones.

Below is a chart that looks at the average crash rate for different intersection types.  For most intersection types, as the traffic volume (ADT) increases the crash rate decreases.  The old adage “there’s safety in numbers”  applies here.  Yes, there will be more total collisions at a busier intersection than a quite one, but the busier intersection will likely have a lower per million entering vehicle crash rate. 

(http://media.tmiponline.org/clearinghouse/tools/images/figure2.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on August 19, 2016, 08:49:23 PM
Another factor for many of the Carmel roundabouts near US 31 has been 5 years of US 31 reconstruction (http://us31hamiltoncounty.in.gov/) which has substantially disrupted traffic patterns and pushed more traffic to the local roads over the last several years.   Things are just now returning to normal now that the US 31 project is drawing to a close.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on August 20, 2016, 08:35:00 AM
Keep in mind that there are roughly the same number of traffic signals as there are roundabouts in Carmel; yet 75% of the fatalities over the past few years have happened at Carmel's incredibly "safe" roundabouts.

How much traffic passes through the roundabouts, compared to the signals? I've always maintained that the number of collisions is, more often than not, a factor of the amount of traffic going through the intersection. And to be clear, I'm not suggesting that all busy intersections have high amounts of collisions. It just seems to me that busier intersections have more collisions than quieter ones.

Also, I should point out that 4 is a very small pool to draw conclusions from.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 20, 2016, 11:46:42 AM
Below is an updated list estimating the crash rate of 3x2 and 2x2 multi-lane roundabouts in America.  These multi-lane roundabouts have an average crash rate of 4.09 which is more than double the average crash rate of other intersection types (two lane signalized; undivided signalized; left turn signalized; etc.).  The roundabouts highlighted in yellow have had circulating lanes removed in the roundabout.  The fact that agencies have been actively removing circulating lanes at these complex multi-lane roundabouts is a good indication that there is indeed a crash problem. 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/untitled002_zpsmpldqovh.png)

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/figure2_zpsw0ewtim1.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on August 20, 2016, 11:55:23 AM
Below is an updated list estimating the crash rate of 3x2 and 2x2 multi-lane roundabouts in America.  These multi-lane roundabouts have an average crash rate of 4.09 which is more than double the average crash rate of other intersection types (two lane signalized; undivided signalized; left turn signalized; etc.).  The roundabouts highlighted in yellow have had circulating lanes removed in the roundabout.  The fact that agencies have been actively removing circulating lanes at these complex multi-lane roundabouts is a good indication that there is indeed a crash problem. 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/untitled002_zpsmpldqovh.png)

It's hard for me to get behind a table like this, when there are obviously multi-lane roundabouts in North America that are not included in the table.  To me, it seems like you're hand-picking the worst multi-lane roundabouts and then using that data to discredit multi-lane roundabouts in general.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 20, 2016, 12:28:29 PM
^^^If what you are saying is true, i wouldn't have included the 68th Avenue & Randall St. roundabout in the analysis since it had a relatively low crash rate.  A crash rate below 2.0 is basically the cut off of being considered an acceptable crash rate in the engineering community.  The reality is i included crash data for every major 2x2 or 3x2 multi-lane roundabout i could find data on.  In any case, this is a public thread.  Anybody who knows of multi-lane roundabouts with low crash rates are welcome to post them here.

Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on August 20, 2016, 01:24:18 PM
I was just reading Waterloo Region's page "All About Roundabouts" (http://www.regionofwaterloo.ca/en/gettingAround/All-About-Roundabouts.asp) and I thought the following picture and video were funny:

(http://www.regionofwaterloo.ca/en/gettingAround/resources/Roundabout_Posters_Website_-_Main_Graphic.jpg)


Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on August 20, 2016, 02:49:59 PM
^^^If what you are saying is true, i wouldn't have included the 68th Avenue & Randall St. roundabout in the analysis since it had a relatively low crash rate.  A crash rate below 2.0 is basically the cut of of being considered an acceptable crash rate in the engineering community.  The reality is i included crash data for every major 2x2 or 3x2 multi-lane roundabout i could find data on.  In any case, this is a public thread.  Anybody who knows of multi-lane roundabouts with low crash rates are welcome to post them here.

I'm not savvy enough to know where to find such data.  All I know is that none of the multi-lane roundabouts I've personally driven through or can think of offhand are included.

(Sheridan at Ridgeview in Olathe, KS)
(Branson Landing Blvd at Skaggs in Branson, MO)
(Valley Mills at Robinson in Waco, TX)

Sorry if I offended you, but zero out of three immediately made me think the table was untrustworthy.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 20, 2016, 05:41:49 PM
^^^
The Branson, MO roundabout doesn’t have 2 circulating lanes throughout the entire roundabout (one of the leg only has one circulating lane).  This greatly simplifies the turning movements and I would not consider this a true 2x2 multi-lane roundabout. 

The Waco, TX intersection isn’t a modern roundabout.  The entry flare angles are way off and there is no pavement marking inside the roundabout. 

The Olathe, KS roundabout is worthy of further investigation.  I just can’t find any crash data for it.  If anyone can find detailed crash data for the Sheridan at Ridgeview roundabout it would be greatly appreciated! 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 23, 2016, 12:54:10 AM
A newly constructed roundabout in Port Huron township put a sudden stop to this police chase.  Gotta love how this story preempted the terrifying armed robbery video. 

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 23, 2016, 01:55:14 AM
There are a few roundabouts that have had multiple fatal crashes.  One of them is 96th & Westfield Blvd in Carmel Indiana:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBfatalcrash1_zpsqnbnkfsm.png)

Quote
Police say two young men died early Monday morning at a roundabout in Carmel.  It happened around 3:00 am at Westfield Blvd. and 96th Street. Police found a Honda Accord in the center portion of the traffic roundabout. Police say the car crashed into the concrete retaining wall.
http://www.wthr.com/article/two-die-at-carmel-roundabout

Quote
A Carmel resident died March 17 after crashing a vehicle into a concrete barrier in the middle of a roundabout.  Police said Lambert Doll was driving a black 2014 Toyota Scion southbound on Westfield Boulevard and failed to negotiate the roundabout at 96th Street. The driver was taken to St.Vincent Hospital in Indianapolis and died a short time later.
http://currentincarmel.com/carmel-driver-dies-after-crashing-into-roundabouts-concrete-barrier

Another roundabout that has experienced multiple fatal crashes is US 62 & Big Tree Road in Hamburg, New York:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/rbfatalcrashhamburg_zpszu3hgskc.png)
Quote
Police have identified the man who crashed into the boulders at the new roundabout on South Park and Big Tree Friday morning.  The victim is 54-year-old Kenneth D. Braun of South Park Avenue in Blasdell. Braun was the owner of the vehicle in the accident. He was identified by the Medical Examiners Office through Dental Records.
http://hamburg.wgrz.com/news/news/60422-victim-identified-hamburg-fatal-crash
Quote
Hamburg man died early this morning after he was ejected from his motorcycle at the intersection of Big Tree Road and South Park Avenue, according to Hamburg police.  The man, 42, was found in the roundabout shortly after 2 a.m. and taken to Mercy Hospital, where he later died, authorities said.
http://www.buffalonews.com/city-region/hamburg/motorcyclist-killed-at-hamburg-roundabout-20130811

There are many scenarios where someone may blow through the center of a roundabout.  I just posted a video of a driver being chased by the cops and flipping his car in the middle of a roundabout.  You also have drunk drivers, drowsy drivers who fall asleep, inattentive drivers, drivers with medical conditions, drivers who misjudge the road conditions and simply enter the roundabout too fast, and even drivers who experience mechanical failure and are unable to slow down.  You might lose your brakes or be driving one of those pesky Toyota’s that have a sticking accelerator pedal.

So a simple question.  Should roundabouts be built with fixed objects in the middle of them?  Had there not been a retaining wall in the middle of that Carmel roundabout we probably wouldn't be talking about it right now.  As it stands, 3 people are dead from striking that retaining wall.

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 23, 2016, 02:38:30 AM
So a simple question.  Should roundabouts be built with fixed objects in the middle of them?  Had there not been a retaining wall in the middle of that Carmel roundabout we probably wouldn't be talking about it right now.  As it stands, 3 people are dead from striking that retaining wall.

Fixed objects? Maybe a town-center roundabout, with a statue. But most roundabouts should have heavy shrubbery in the middle, no fixed objects (especially not concrete ones). Maybe raise the land in the middle a little too, so there's like a small hill, where you could elevate some of the bushes and trees (or whatever you want to place in the middle).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 23, 2016, 09:48:47 AM
The FHWA published a report reviewing the fatal and severe injury crashes at roundabouts.  According to the report there have been 46 fatal roundabout crashes from 2005-2013.  Of the 46 fatal crashes, 39 involved vehicle striking a fixed object (85% of all fatal roundabout crashes).  This excerpt is found on page 22 of the report:

Quote
Many of the fixed object crashes involved vehicles striking the splitter and central islands of roundabouts, striking curbs and sometimes other fixed objects such as sign posts, light poles, landscaping walls, boulders, and trees. At least 35 of the 39 fixed object crashes involved vehicles striking a curb.
http://safety.fhwa.dot.gov/intersection/innovative/roundabouts/docs/fhwasa15072.pdf

It appears they consider it a fixed object crash when a vehicle strikes a curb but it also mentions drivers hitting other fixed objects such as sign posts, light poles, landscaping walls, boulders, and trees.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 23, 2016, 11:20:42 AM
There have been 134 crashes, 9 injury crashes, and 2 semi’s that have tipped over in the first 9 months of a roundabout opening in Jeffersonville, Indiana.  It opened in September 2015 as part of the Ohio River Bridges project and has been a point of contention ever since.  Here’s a picture of one of the tankers that overturned inside the roundabout:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/SEMI-OVERTURNED_zpsw0gucsaj.jpg)
http://www.newsandtribune.com/news/saturday-spotlight-new-jeffersonville-roundabouts-see-accidents-in-nine-months/article_649f5dca-5b4a-11e6-a6f8-c318a61be753.html

Quote
When it first announced the building of the roundabouts, INDOT boasted national figures that show roundabouts are safer, more efficient and greener.  According to the Insurance Institute for Highway Safety, roundabouts compared to four-way intersections increase traffic capacity by 20 to 50 percent and decrease traffic delays by 20 percent, thus saving fuel use and reducing pollution. And roundabouts are proven to decrease fatalities by 90 percent and all crashes by 35 percent, according to the Federal Highway Administration.

Sixteen years ago the Insurance Institute for Highway Safety analyzed a few dozen single-lane and simplified 2x1 multi-lane roundabouts.  Of course roundabouts being built today are much different than roundabouts built back then.  There was no triple-lane roundabouts analyzed in the IIHS study.  That doesn’t stop agencies from citing the out-of-date IIHS study to push any roundabout they are proposing.  Agencies are misleading the public (either knowingly or unknowingly) into thinking some complex 3-lane roundabout will be safer than they actually will be.  If a triple-lane roundabout is being proposed, maybe a study that looks at the safety of triple-lane roundabouts should be cited.  That would be transparent. 

Quote
Accident numbers in its first year of operation may not reflect the true safety of the traffic configuration.  In fact, INDOT excludes data from the first three to 12 months of operations in follow-up monitoring because "it should be expected that motorists are adjusting to the new intersection during this time frame."

Of course later on in the article it states this….

Quote
INDOT is working to improve the safety of the roundabouts. The agency plans to install larger yield signs and tweak other signs and pavement markings to address the most common accident causes.

So which is it?  They exclude data from the first 3 to 12 months of operations in follow-up monitoring yet there are already plans for INDOT to “tweak”  out the roundabout with larger yield signs and pavement marking changes.  How can INDOT determine tweaks are needed if they don’t do any follow-up monitoring for the first three to 12 months of operations?
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on August 23, 2016, 01:02:51 PM
So a simple question.  Should roundabouts be built with fixed objects in the middle of them?  Had there not been a retaining wall in the middle of that Carmel roundabout we probably wouldn't be talking about it right now.  As it stands, 3 people are dead from striking that retaining wall.
A retaining wall is surely structural?

Its also surely quite hard to drive straight across the middle of a roundabout without some other mitigating circumstances - if it wasn't the retaining wall in the roundabout, it gonna be something else.

But yes. Roundabouts, like all streetscapes, should minimise the amount of unyielding solid objects that are possible to crash into at speech, and protect (just as bridge parapets have crash barriers near, something like a wall would need to to) the necessary ones.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 23, 2016, 01:53:24 PM
A retaining wall is surely structural?

Its also surely quite hard to drive straight across the middle of a roundabout without some other mitigating circumstances - if it wasn't the retaining wall in the roundabout, it gonna be something else.

It looks like they added the retaining wall so that decorative plantings could be raised a few feet off the ground.  That appears to be the only purpose of the retaining wall.  There is also shrubbery that somewhat hides the view of the retaining wall.  Here’s the view of the retaining wall as drivers approach it traveling SB Westfield Blvd:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/CarRBUntitled_zps7r1xseh3.png)

I can foresee a scenario where teenagers are joyriding around at 1 in the morning and decide to “turf”  the middle of the roundabout (not realizing there is actually a retaining wall hidden by shrubbery).  The teenagers are just looking for some cheap thrills but instead hit a concrete barrier doing 30 mph.  I don’t know if this scenario has happened but I could see it.  Do you want your 18 year old son or daughter to be involved in a fatal crash at this roundabout just because they are acting like stupid teenagers?
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 23, 2016, 02:00:57 PM
Do you want your 18 year old son or daughter to be involved in a fatal crash at this roundabout just because they are acting like stupid teenagers?

It's about time someone thought about the children.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on August 23, 2016, 02:02:23 PM
What happened to the concept of personal responsibility?   If you drive like an idiot you live (or die) with the consequences.  These are the same people that would have blown the stop sign and taken out another car when it was a stop controlled intersection -- I'm much happier with them being stopped by an inanimate object rather than another vehicle.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on August 23, 2016, 02:24:11 PM
It looks like they added the retaining wall so that decorative plantings could be raised a few feet off the ground.  That appears to be the only purpose of the retaining wall.  There is also shrubbery that somewhat hides the view of the retaining wall.  Here’s the view of the retaining wall as drivers approach it traveling SB Westfield Blvd:
Well that's someone not thinking things through and designing for stupidness.

You can't blame roundabouts for this though - the problem isn't the roundabout as a road feature, but the really poor thinking about where a garden is by its designer. I would say it's little different to a tree blocking a stop sign, but that's far worse as there's no legitimate reason people should be driving across the roundabout's island.
Quote
Do you want your 18 year old son or daughter to be involved in a fatal crash at this roundabout just because they are acting like stupid teenagers?
No, but
1) They aren't acting stupid, they are acting reckless. It's not that they didn't see the roundabout, or didn't know what to do when driving through one, but that they chose to drive over it at 30mph.
2) This recklessness doesn't absolve them from blame, but you seem to put the entire blame on the traffic engineer, who is entirely blameless as they didn't design the garden nor choose to drive across the roundabout, and his choice of junction for the intersection.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 23, 2016, 02:36:08 PM
There have been 3 deaths already at this Carmel roundabout, all caused when a vehicle struck the retaining wall.  How decorative is that retaining wall to begin with?  Would the roundabout really lose that much aesthetics if the retaining wall was torn down? 

If you drive like an idiot you live (or die) with the consequences.  These are the same people that would have blown the stop sign and taken out another car when it was a stop controlled intersection -- I'm much happier with them being stopped by an inanimate object rather than another vehicle.

The teenager who is willing to turf a roundabout for fun isn't going to be blowing every red light that they come across.  They are reckless not suicidal.  Don't get me wrong, someone turfing a roundabout is an idiot, and they may very well pay with their life if they don't recognize the retaining wall in the middle of it. But your assumption is anyone who dies at a roundabout would have somehow killed or seriously injured someone else if they had not died in the roundabout.  You really believe that?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 23, 2016, 02:44:04 PM
What happened to the concept of personal responsibility?   If you drive like an idiot you live (or die) with the consequences.  These are the same people that would have blown the stop sign and taken out another car when it was a stop controlled intersection -- I'm much happier with them being stopped by an inanimate object rather than another vehicle.
If we rely on personal responsibility only, there would be no airbags, no seatbelts, no handrails on stairs, no many other things. You're not supposed to crash, not supposed to slip on stairs etc. However those things happen, and someone made an effort to minimize the consequences.
Job of engineer is to accommodate common human mistakes in the design. Or choose another job. Did I mention we have some open position in janitorial service?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 23, 2016, 03:50:04 PM
The double-lane roundabouts analyzed in the Michigan study actually saw a 39% increase in fatal & incapacitating injury crashes (1.50 / 1.08).  Based on some of the recent comments in this thread, we should be embracing the increase in fatal crashes at Michigan’s double-lane roundabouts because they are killing off bad drivers.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBMi_zpsagf61awg.png)
https://www.michigan.gov/documents/mdot/MDOT_Research_Report_RC1566_379286_7.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on August 23, 2016, 04:13:10 PM
The double-lane roundabouts analyzed in the Michigan study actually saw a 39% increase in fatal & incapacitating injury crashes (1.50 / 1.08).  Based on some of the recent comments in this thread, we should be embracing the increase in fatal crashes at Michigan’s double-lane roundabouts because they are killing off bad drivers.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBMi_zpsagf61awg.png)
https://www.michigan.gov/documents/mdot/MDOT_Research_Report_RC1566_379286_7.pdf


Today in cherry-picking: the triple-lane roundabouts in the study actually saw over a 50% decrease in "A-level" crashes (from 1.98 to 0.83, page 56, redacted from your table). So clearly drivers are too stupid to understand two-lane roundabouts but do just fine with three-lane jobs...?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 23, 2016, 04:22:04 PM
Job of engineer is to accommodate common human mistakes in the design. Or choose another job. Did I mention we have some open position in janitorial service?

According to tradephoric's study from several pages ago, 52% of all fatal collisions at roundabouts involved impairment. How exactly do you propose that we curb impaired driving collisions at roundabouts? Roundabouts require a quick reflex, which is something that usually drops when you're impaired (though I know this isn't the case for all drugs). Drunk-driving is less of an issue at signals because driving straight doesn't necessarily require a lot of thought -- you just keep your hands on the wheel, don't twist them, and keep going.

Now, I'm not saying that we have to ignore drunk-driving. But by suggesting that roundabouts are poorly designed because they don't accommodate drunk drivers is ludicrous.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on August 23, 2016, 04:38:43 PM
There have been 3 deaths already at this Carmel roundabout, all caused when a vehicle struck the retaining wall.
And therefore recklessness and landscapers not accounting for recklessness are to blame, rather than the highway engineer and their junction choice.
Quote
How decorative is that retaining wall to begin with?
As you point out, entirely. And therefore out of the remit of highway engineers.
Quote
Would the roundabout really lose that much aesthetics if the retaining wall was torn down?
No it wouldn't. Hence why your use of that one fatal collision as part of your argument that multilane roundabouts are death traps is totally and utterly disingenuous.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 23, 2016, 04:43:07 PM
Job of engineer is to accommodate common human mistakes in the design. Or choose another job. Did I mention we have some open position in janitorial service?

According to tradephoric's study from several pages ago, 52% of all fatal collisions at roundabouts involved impairment. How exactly do you propose that we curb impaired driving collisions at roundabouts? Roundabouts require a quick reflex, which is something that usually drops when you're impaired (though I know this isn't the case for all drugs). Drunk-driving is less of an issue at signals because driving straight doesn't necessarily require a lot of thought -- you just keep your hands on the wheel, don't twist them, and keep going.

Now, I'm not saying that we have to ignore drunk-driving. But by suggesting that roundabouts are poorly designed because they don't accommodate drunk drivers is ludicrous.
I am not aware of any roundabout which cannot be fixed to accommodate diversity of human skills. Couple of high power bulldozers would do most of the job within couple of hours.
And reflexes are not only impaired by alcohol and related stuff. Besides, not everyone is a NASCAR driver. Something like a flu (did you ever got sick while at work, for example?) or lack of sleep (ever had to work too much overtime?) may do the trick. Of course,  there is an option of letting Darwin do the job...

Oh, and you know - 1/3 of all fatal traffic accidents in US involve alcohol. 50% of drinking age pedestrians hit with cars were actually drunk.
 Please present your case for elimination of airbags and crosswalks based on that data. Would save tons of money...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 23, 2016, 04:58:14 PM
Today in cherry-picking: the triple-lane roundabouts in the study actually saw over a 50% decrease in "A-level" crashes (from 1.98 to 0.83, page 56, redacted from your table). So clearly drivers are too stupid to understand two-lane roundabouts but do just fine with three-lane jobs...?

I provided a link to the full study.  Anybody that took the time to read the report could easily point out that the triple-lane roundabouts saw fatal crashes drop by over 50% (which is still well short of the 90% reduction in fatal crashes advertised in the national studies).  The study highlights that the reduction in fatal crashes at the double and triple lane roundabouts in Michigan are lackluster at best.  When you combine the double and triple lane roundabouts analyzed in the study, fatal and incapacitating injuries only dropped by 24%.  That's nowhere near a 90% reduction.

The only roundabout type that had a stellar safety record in the Michigan study were the single-lane roundabouts.  They saw a 50% reduction in total crashes, a 56% reduction in injury crashes, and a 88% reduction in fatal and incapacitating injury crashes. That's the kind of safety result you want to see. 
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on August 23, 2016, 05:37:03 PM
Yes, ideally we'd get the improvements of single-lane roundabouts. However, single-lane roundabouts won't accommodate higher traffic volumes without either signalization of entrances (which reduces the traffic flow and efficiency benefits, although at least signalization retains the angle-of-incidence benefits and probably reduces crashes overall over free-flow) or more lanes (which reduce, but certainly doesn't eliminate, the injury/fatal crash benefits on average).

Personally, I'm ok with 25-50% fewer people burying their loved ones due to crashes at high-volume intersections if that means a few more people end up in fender-benders, if that's what the ultimate improvement of multi-lane roundabouts turns out to be. I suspect it's closer to the single-lane case over the long term with more examples and years of data, but even 25% would be a substantial improvement especially in light of the other quality of life benefits (time, stopped vehicle emissions, etc.).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 23, 2016, 05:40:32 PM
Would the roundabout really lose that much aesthetics if the retaining wall was torn down?
No it wouldn't. Hence why your use of that one fatal collision as part of your argument that multilane roundabouts are death traps is totally and utterly disingenuous.

If I’m trying to prove that multilane roundabouts are “death traps”  wouldn’t it be more effective for me to focus on fatal crashes that have occurred at multilane roundabouts?  The roundabout with the retaining wall we have been discussing is the single-lane roundabout at 96th & Westfield Blvd in Carmel.

The theory is that roundabouts with fixed objects in the central island will have more injuries than roundabouts with grassy central islands where there is nothing to hit.  Regardless if the roundabout is single-lane or multi-lane, there will be times when drivers blow through the roundabout's central island.  The question is should these drivers be severely punished for their mistake? 
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 23, 2016, 05:50:07 PM
Today in cherry-picking: the triple-lane roundabouts in the study actually saw over a 50% decrease in "A-level" crashes (from 1.98 to 0.83, page 56, redacted from your table). So clearly drivers are too stupid to understand two-lane roundabouts but do just fine with three-lane jobs...?

I provided a link to the full study.  Anybody that took the time to read the report could easily point out that the triple-lane roundabouts saw fatal crashes drop by over 50% (which is still well short of the 90% reduction in fatal crashes advertised in the national studies).  The study highlights that the reduction in fatal crashes at the double and triple lane roundabouts in Michigan are lackluster at best.  When you combine the double and triple lane roundabouts analyzed in the study, fatal and incapacitating injuries only dropped by 24%.  That's nowhere near a 90% reduction.

The only roundabout type that had a stellar safety record in the Michigan study were the single-lane roundabouts.  They saw a 50% reduction in total crashes, a 56% reduction in injury crashes, and a 88% reduction in fatal and incapacitating injury crashes. That's the kind of safety result you want to see.
It is impossible to tell for sure without full datasets - but looks like there are some roundabouts that work, and there are some that don't.  Probably depends on traffic patterns.. Bust since roundabouts are the most bestest thing since sliced bread, there is no time to think about it, we need to get more contracts out. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 23, 2016, 05:57:21 PM
"I'd say in the past ten years, you've seen an increase in modern roundabouts just because research has proven that they are safer, so we have started implementing them in New York State," said Surdej.  "And we have started implementing them successfully, we are seeing a reduction in accident rates in those intersections where there are modern roundabouts."

(http://awsmedia.dtsph.com/sites/wgrz.com/files/imagecache/story615/111028102552_south_20park_20fatal.jpg)
http://hamburg.wgrz.com/news/news/60422-victim-identified-hamburg-fatal-crash

Put another way... the IIHS assured us that roundabouts are safer so we can build any roundabout we want... hell we're going to put some boulders in the middle of this one.  No harm will be done when drivers strike them... ooh wait, maybe a driver will hit those rocks, causing their vehicle to flip over and catch on fire, burning the driver alive where they can only be identified through dental records.  Yeah, that could happen too i guess.  Maybe not all roundabouts are created equal and maybe it was a really bad idea to put those boulders in the middle of the central island.

Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on August 23, 2016, 09:42:19 PM
Does anyone know what these markings are called? I've circled them in the satellite image below of the Fairway/Kossuth/Fountain roundabout in Cambridge, ON (https://www.google.ca/maps/@43.4434062,-80.3875729,160m/data=!3m1!1e3)

(http://i.imgur.com/yu7YviK.png)

I feel like the fact that they point in the opposite direction of traffic makes them confusing. They're also inconsistently applied. This roundabout in the same city, at Franklin Blvd and Sheldon Dr (https://www.google.ca/maps/@43.4061856,-80.3070214,161m/data=!3m1!1e3) has them at both entrances and exits (notice the first image has no markings on exits).

(http://i.imgur.com/iQ6rwOb.png)

I drove the above roundabout a few weeks ago and for a split second, I saw the markings and wondered if I somehow went the wrong way! Of course I didn't, but the fact that these could make someone think that makes me wonder if they should even be there at all?
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on August 23, 2016, 09:46:18 PM
Those are Yield markings. They're at roundabout entrances to indicate yielding to traffic within the roundabout. The fact that your second example has them at exits is due to there being crosswalks near the exits, and the markings are actually to indicate yielding to pedestrians.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 23, 2016, 09:55:11 PM
Yep...they're the same shape as a yield sign. Its basically a stop bar, but with diamonds instead. There should be a yield sign posted in line with the markings.

They may be confusing if you haven't seen them before, which happens with many traffic control devices that one doesn't come across very often.
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on August 23, 2016, 10:03:12 PM
^ Oh okay, that explains my confusion.

But I noticed this nearby roundabout at Fairway/Zellar/Woolner in Kitchener (https://www.google.ca/maps/@43.4479723,-80.4043804,160m/data=!3m1!1e3) has crosswalks but no yield markings on exits.

(http://i.imgur.com/wkfaTpY.png)

They have these signs, which could be argued have the same function. But the Franklin/Sheldon roundabout with the exit markings also has these signs. I guess the Region decided these markings were no longer needed on exits?

(http://images.roadtrafficsigns.com/img/lg/K/Yield-Here-Pedestrian-Crossing-Sign-K-4222.gif)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 23, 2016, 10:55:22 PM
Does anyone know what these markings are called? I've circled them in the satellite image below of the Fairway/Kossuth/Fountain roundabout in Cambridge, ON (https://www.google.ca/maps/@43.4434062,-80.3875729,160m/data=!3m1!1e3)

I know kphoger and j&n have already filled you in, but they are commonly called "shark's teeth" as well, to distinguish them from the adjacent dashed white lines.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on August 24, 2016, 10:16:43 AM
Put another way... the IIHS assured us that roundabouts are safer so we can build any roundabout we want... hell we're going to put some boulders in the middle of this one.  No harm will be done when drivers strike them... ooh wait, maybe a driver will hit those rocks, causing their vehicle to flip over and catch on fire, burning the driver alive where they can only be identified through dental records.  Yeah, that could happen too i guess.  Maybe not all roundabouts are created equal and maybe it was a really bad idea to put those boulders in the middle of the central island.

Really? I'm not saying we should be putting boulders in the center of a roundabout, but how are they any different than any other fixed object you find along just about any other road? Utility poles, trees, a building too close to a road...hell, many of the newer monotube traffic signal poles aren't breakaway. And even if you only have a mound of grass, it can still be deadly. Several years ago, there was a motorcyclist who vaulted over the central island and hit a Yield sign on the opposite side. Yeah, you guessed it, alcohol and excessive speed were the causes. I had a friend doing something stupid along a country back-road...going too fast, caught some air on a hill, lost control, and hit a utility pole. Dead on impact. So, by your argument, it's the utility company's fault my friend is dead? (FYI, the pole was outside of the right-of-way). Should everything be designed for every possible outcome of a driver doing something stupid, who accounts for a tiny fraction of the overall motoring public?

This maybe an easier solution...wrap anything and everything in 5 layers of industrial-grade bubble wrap.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 24, 2016, 11:06:55 AM
Put another way... the IIHS assured us that roundabouts are safer so we can build any roundabout we want... hell we're going to put some boulders in the middle of this one.  No harm will be done when drivers strike them... ooh wait, maybe a driver will hit those rocks, causing their vehicle to flip over and catch on fire, burning the driver alive where they can only be identified through dental records.  Yeah, that could happen too i guess.  Maybe not all roundabouts are created equal and maybe it was a really bad idea to put those boulders in the middle of the central island.

Really? I'm not saying we should be putting boulders in the center of a roundabout, but how are they any different than any other fixed object you find along just about any other road? Utility poles, trees, a building too close to a road...hell, many of the newer monotube traffic signal poles aren't breakaway. And even if you only have a mound of grass, it can still be deadly. Several years ago, there was a motorcyclist who vaulted over the central island and hit a Yield sign on the opposite side. Yeah, you guessed it, alcohol and excessive speed were the causes. I had a friend doing something stupid along a country back-road...going too fast, caught some air on a hill, lost control, and hit a utility pole. Dead on impact. So, by your argument, it's the utility company's fault my friend is dead? (FYI, the pole was outside of the right-of-way). Should everything be designed for every possible outcome of a driver doing something stupid, who accounts for a tiny fraction of the overall motoring public?

This maybe an easier solution...wrap anything and everything in 5 layers of industrial-grade bubble wrap.

If you will, it is about momentary lapse of attention - what are the consequences? on a straight road without obstacles consequences are usually minimal. Many highways have rumble strips and/or railings along the shoulder to minimize effects. Curbstone along the street also helps to avoid poles. Bright signs at curves and T intersections are there as well.

While running red light is definitely illegal and dangerous - few of this events end up as actual accidents, most limited with swearing, honking and replacement underwear.  Here we're talking about situation, when equivalent of running red light is almost guaranteed to be an injury accident.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 24, 2016, 12:01:45 PM
Welcome back DaBigE.   Haven’t seen any posts from you for a while and it’s good to hear from you again.  You are just the person I wanted to talk to.  A few posts back a triple-lane teardrop roundabout in Jeffersonville, Indiana was being discussed.  In the first 9 months of operation there were 134 crashes, 9 injury crashes, and 2 semi’s that tipped over inside the roundabout.  It hasn’t been a great start to say the least.  I know other triple-lane interchange roundabouts have been built and I wonder how they have performed.   Specifically, Green Bay has built 5 triple-lane interchange roundabouts in recent years:

Mason Street & NB Hwy 41 (built 2012)
Mason Street & SB Hwy 41 (built 2012)
Main Ave & Mid Valley Drive/SB Hwy 41 on-ramp (built 2014?)
Shawano Ave & NB Hwy 41 (built 2014)
Shawano Ave & SB Hwy 41 (built 2014)

The Brown County Planning Commission published a detailed Intersection Crash Study in February 2015 but the crash data only goes up to 2012.  So my question is do you know where I can find up to date intersection crash data for the Green Bay Metropolitan Area?  I thought you might know where to find this data since you are the unofficial Wisconsin expert.  Here's the Intersection Crash Study i was able to find:
http://www.co.brown.wi.us/i/f/Metro%20area%20crash%20study%20for%202010-2012%20(final)%20-%20February%202015.pdf

To respond to your previous post, no I don’t want to live in bubble-boy world.  The point was I don’t see what function those boulders serve.  Was it meant for aesthetics?  It’s my personal believe that if the central island was a simple patch of grass that fewer people would be injured at the roundabout.  Sure, you will still have motorcyclists hopping curbs at roundabouts and finding ways to kill themselves.  But that doesn’t mean we shouldn’t try to get rid of the unnecessary obstacles.  There have already been two fatal crashes at the Hamburg roundabout since it opened in 2011 and the boulders played a part in that.  This is a statement Renee Wall made in a news article about her brother’s death. 

"It was not well lit, the speed limit is 45, it goes from two lanes to one. But to put boulders in the middle of it? They're not forgiving."

Renee is absolutely right.  Those boulders in the middle of the roundabout were not forgiving.  It didn’t take long for someone to find that out the hard way.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 24, 2016, 12:25:46 PM

Renee is absolutely right.  Those boulders in the middle of the roundabout were not forgiving.  It didn’t take long for someone to find that out the hard way.


You never know...there could've been someone traveling on the other side of the roundabout, and the boulder saved the idiot driver from plowing thru the median into their car, killing them instead.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 24, 2016, 12:45:14 PM
You never know...there could've been someone traveling on the other side of the roundabout, and the boulder saved the idiot driver from plowing thru the median into their car, killing them instead.

Actually, we know the facts of this case... no need to play hypotheticals.  Investigators believe “Braun was heading north on South Park Avenue when his pickup truck collided with decorative boulders in the middle of the roundabout and flipped in the air, landing in the southbound lane” .
(http://awsmedia.dtsph.com/sites/wgrz.com/files/imagecache/story615/111028102552_south_20park_20fatal.jpg)
http://hamburg.wgrz.com/news/news/60422-victim-identified-hamburg-fatal-crash

The vehicle wasn’t contained in the central island after striking the boulders.  It cleared the boulders and landed upside down in the southbound lanes.  In the future try reading the articles i post as it might fill you in on some facts.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 24, 2016, 12:58:46 PM
It cleared the boulders and landed upside down in the southbound lanes.  In the future try reading the articles i post as it might fill you in on some facts.

I read the article, and it failed to tell me the other traffic that was in the roundabout; it just told me about this car, that it cleared the boulders, and eventually landed in the southbound lanes.  Please include all the details regarding everything within the roundabout at the time so I know all the facts.

Oh, wait...

Quote
"...no need to play hypotheticals.  Investigators believe"

Please...reread that about a hundred times, and tell me how "believe" is not the same as "hypothetical".   Thus, even what you read states that they don't know the facts...they can only draw up a reasonable conclusion.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 24, 2016, 01:42:08 PM
^There is a picture of the pickup upside down in the southbound lane of the roundabout.  That picture isn't a cartoon.  Your assumption was that the boulders would stop a driver from blowing straight through the roundabout.  All your semantics doesn't change the fact that your assumption was wrong. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 24, 2016, 01:48:02 PM
Here are two similar capacity triple-lane interchange roundabouts.  One is the Jeffersonville, Indiana roundabout that has been a trouble spot over the first 9 months (134 crashes, 9 injuries, and 2 semi’s tipped over).  The other roundabout is from Green Bay constructed in 2014.  I haven’t read any articles to suggest that this Green Bay roundabout is a hot spot for crashes but I don’t have any crash data to verify this either.  Does one design look superior to the other?

10th Street & EB 265; Jeffersonville, Indiana 
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBIND_zpsuy1rfrld.png)

Shawano Ave & NB US 41; Green Bay, Wisconsin
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBWIS_zpscfy1nlcq.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on August 24, 2016, 02:09:36 PM
So my previous comment was based solely on the discussion here and the little the news story had about the crash. I was originally envisioning something with more buffer space between the rocks and the roadway. Looking at the intersection in Google Earth (this is the one, correct? (https://www.google.com/maps/@42.7717896,-78.8237507,269a,20y,349.05h/data=!3m1!1e3)), this roundabout was an accident waiting to happen. From my perspective, there is no way that central island landscaping should have been allowed, especially with that design and those approach speeds. While it does have a barrier curb separating the truck apron from the decoration, there's maybe a foot of space from the curb head to the rock. We require at least 6-feet of distance from the final barrier curb to any landscaping in the central island (mainly for sight, but it also can act as a small recovery zone). Not knowing what kind of trucks have to get through there, I'd say the apron is over-sized for the needs of a standard semi. That would have potentially allowed for a more-forgiving central island design. While I do see some deflection in the approaches, it seems weak, especially if someone is hugging the fog line.

"It was not well lit, the speed limit is 45, it goes from two lanes to one. But to put boulders in the middle of it? They're not forgiving."

Not well-lit? Without seeing photometrics, I can't say for sure, but I do know I've seen unlit roundabouts with faster approaches and no crash issues. This one appears to have average lighting, based on the poles I see in the GE image. Maybe some lights weren't functioning for whatever reason. What I am not seeing is the "two lanes to one". I do see a TWLTL, but that shouldn't matter, as it's not a legal thru driving lane. It's an otherwise two-lane highway.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on August 24, 2016, 02:15:12 PM
Here are two similar capacity triple-lane interchange roundabouts.  One is the Jeffersonville, Indiana roundabout that has been a trouble spot over the first 9 months (134 crashes, 9 injuries, and 2 semi’s tipped over).  The other roundabout is from Green Bay constructed in 2014.  I haven’t read any articles to suggest that this Green Bay roundabout is a hot spot for crashes but I don’t have any crash data to verify this either.  Does one design look superior to the other?

Home-state biases aside, the Green Bay one is more superior. The Indiana one has the speed control at the wrong point on the approach, especially for the EB approach. The tangent section between the yielding point and the approach curve allows traffic to speed up as they're entering the roundabout (what we refer to as a "hockey stick" design). There's also an exceptionally large "flat spot"/tangent in the NB circulatory spiral that would encourage more speed.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 24, 2016, 02:57:26 PM
Looking at the intersection in Google Earth (this is the one, correct? (https://www.google.com/maps/@42.7717896,-78.8237507,269a,20y,349.05h/data=!3m1!1e3)), this roundabout was an accident waiting to happen.

Yes, that's the roundabout in question.

Not well-lit? Without seeing photometrics, I can't say for sure, but I do know I've seen unlit roundabouts with faster approaches and no crash issues. This one appears to have average lighting, based on the poles I see in the GE image. Maybe some lights weren't functioning for whatever reason. What I am not seeing is the "two lanes to one". I do see a TWLTL, but that shouldn't matter, as it's not a legal thru driving lane. It's an otherwise two-lane highway.

The fatal crash occurred shortly after the roundabout opened.  There were questions whether or not the roundabout was ready to be opened to traffic in the first place.  According to another article, the night of the fatal crash overhead lights were not in place and the pavement markings had not been completed.  A few weeks after the fatal crash, crews removed the boulders and replaced them with fiberglass rocks designed to buckle when a vehicle passes over them.  The city must really like the aesthetics of the boulders to reinstall fiberglass rocks to get the same look as before.  Why they like that look so much is beyond me.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 24, 2016, 04:18:49 PM
Home-state biases aside, the Green Bay one is more superior. The Indiana one has the speed control at the wrong point on the approach, especially for the EB approach. The tangent section between the yielding point and the approach curve allows traffic to speed up as they're entering the roundabout (what we refer to as a "hockey stick" design). There's also an exceptionally large "flat spot"/tangent in the NB circulatory spiral that would encourage more speed.

Another obvious difference between the two is that the Green Bay roundabout is a dumbbell whereas the Jeffersonville one is a teardrop. I personally favor dumbbells because you never know when someone may want to make a U-turn.  But more importantly, with a dumbbell drivers that are coming from the bridge have to yield to vehicles that may be circulating the roundabout.  Drivers at teardrop roundabouts OTOH don’t encounter a yield sign along one of the legs which may make the roundabout feel like more of a racetrack to these drivers.  If they don't see a YIELD sign they may be encouraged to go faster.  I hope what I’m saying makes sense since I think it’s an important point.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on August 24, 2016, 04:29:55 PM
Another obvious difference between the two is that the Green Bay roundabout is a dumbbell whereas the Jeffersonville one is a teardrop. I personally favor dumbbells because you never know when someone may want to make a U-turn.  But more importantly, with a dumbbell drivers that are coming from the bridge have to yield to vehicles that may be circulating the roundabout.  Drivers at teardrop roundabouts OTOH don’t encounter a yield sign along one of the legs which may make the roundabout feel like more of a racetrack to these drivers.  If they don't see a YIELD sign they may be encouraged to go faster.  I hope what I’m saying makes sense since I think it’s an important point.

Both dumbbell and teardrop roundabout designs have their merits, which is why I left that out of my commentary not having looked in-depth on the context of the locations beyond what your images show. Teardrop, IMO, are better-suited for closely-spaced roundabouts/ramp terminals. Snowplowing benefits could go either way.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on August 24, 2016, 04:36:22 PM
The fatal crash occurred shortly after the roundabout opened.  There were questions whether or not the roundabout was ready to be opened to traffic in the first place.  According to another article, the night of the fatal crash overhead lights were not in place and the pavement markings had not been completed.  A few weeks after the fatal crash, crews removed the boulders and replaced them with fiberglass rocks designed to buckle when a vehicle passes over them.  The city must really like the aesthetics of the boulders to reinstall fiberglass rocks to get the same look as before.  Why they like that look so much is beyond me.

I would also question if it was ready to be opened as well, however, pavement markings for a single-lane roundabout shouldn't be that critical. Lighting depends on who you ask, as there are quite a few unlit rural roundabouts with no crash issues.

The city probably likes the rocks because they don't require much maintenance...in theory.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 24, 2016, 04:46:59 PM
Both dumbbell and teardrop roundabout designs have their merits, which is why I left that out of my commentary not having looked in-depth on the context of the locations beyond what your images show. Teardrop, IMO, are better-suited for closely space roundabouts/ramp terminals. Snowplowing benefits could go either way.

This dumbbell vs. teardrop (dogbone) roundabout debate has come up before on here.  It's funny because i think it's bad that drivers aren't displayed a yield sign along one of the legs of a teardrop roundabout.  Of course someone on the other thread made a point exactly opposite of me lol

With the dumbbell style, since there are so few vehicles making that U-turn, drivers will get used to never seeing vehicles there and potentially ignore the yield sign.  This becomes a safety hazard, and makes the dogbone style a better choice.  As stated before, drivers can still make that U-turn; they just have to travel a bit farther to do it.
https://www.aaroads.com/forum/?topic=16468.0


Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on August 24, 2016, 05:35:35 PM
"I'd say in the past ten years, you've seen an increase in modern roundabouts just because research has proven that they are safer, so we have started implementing them in New York State," said Surdej.  "And we have started implementing them successfully, we are seeing a reduction in accident rates in those intersections where there are modern roundabouts."

(http://awsmedia.dtsph.com/sites/wgrz.com/files/imagecache/story615/111028102552_south_20park_20fatal.jpg)
http://hamburg.wgrz.com/news/news/60422-victim-identified-hamburg-fatal-crash

Put another way... the IIHS assured us that roundabouts are safer so we can build any roundabout we want... hell we're going to put some boulders in the middle of this one.  No harm will be done when drivers strike them... ooh wait, maybe a driver will hit those rocks, causing their vehicle to flip over and catch on fire, burning the driver alive where they can only be identified through dental records.  Yeah, that could happen too i guess.  Maybe not all roundabouts are created equal and maybe it was a really bad idea to put those boulders in the middle of the central island.

Yes, clearly the NYSDOT spokesperson really hates motorists and wants them to tie horribly in fires. That's the obvious conclusion from the bland quotation that shows no evidence it was actually a response to a question about this specific accident instead of a question like "Why is NYSDOT building roundabouts?"
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on August 24, 2016, 06:29:33 PM
A few posts back a triple-lane teardrop roundabout in Jeffersonville, Indiana was being discussed.  In the first 9 months of operation there were 134 crashes, 9 injury crashes, and 2 semi’s that tipped over inside the roundabout.  It hasn’t been a great start to say the least.  I know other triple-lane interchange roundabouts have been built and I wonder how they have performed.   Specifically, Green Bay has built 5 triple-lane interchange roundabouts in recent years:

Mason Street & NB Hwy 41 (built 2012)
Mason Street & SB Hwy 41 (built 2012)
Main Ave & Mid Valley Drive/SB Hwy 41 on-ramp (built 2014?)
Shawano Ave & NB Hwy 41 (built 2014)
Shawano Ave & SB Hwy 41 (built 2014)

The Brown County Planning Commission published a detailed Intersection Crash Study in February 2015 but the crash data only goes up to 2012.  So my question is do you know where I can find up to date intersection crash data for the Green Bay Metropolitan Area?  I thought you might know where to find this data since you are the unofficial Wisconsin expert.  Here's the Intersection Crash Study i was able to find:
http://www.co.brown.wi.us/i/f/Metro%20area%20crash%20study%20for%202010-2012%20(final)%20-%20February%202015.pdf

I don't have any other data for you...not in a convenient report form and not without going through quite a bit of bureaucracy that I don't have time for at the moment.  Best bet would be to contact Brown County or WisDOT NE regional office directly. Even if there was easily accessible data, it would be skewed with the various detour routes going through the region, altering the flows the roundabouts were originally designed for. You won't get any reliable after data until the whole project is wrapped-up and all detour routes removed.

All I can say is that the media has been very quiet from that area of the state in regards to those intersections.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 24, 2016, 07:09:48 PM
^Thanks for the info.   Hopefully the numbers will come out soon.  There aren't that many triple lane roundabouts in America and the engineering community would be pretty interested to see how these Green Bay roundabouts are performing.  I wouldn't be surprised if they discuss these roundabouts in detail at the next roundabout conference.  And you make a good point about the detour routes skewing the data.  Of course, roundabouts will be the site of detour routes moving forward since every construction season there are new detour routes.  If roundabouts are designed for a certain traffic pattern and they can't adapt to changing traffic patterns due to detours, that could be a concern.
Title: Re: Crash prone 'modern roundabouts'
Post by: johndoe on August 24, 2016, 08:35:10 PM
The tangent section between the yielding point and the approach curve allows traffic to speed up as they're entering
Perhaps they were more concerned with entry path overlap?  Maybe there is a high percentage of trucks?  Does Wisconsin not encourage the 20' tangent before eoct?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 24, 2016, 08:44:11 PM
Half of Pennsylvania’s Roundabouts Show A Decrease In Crashes
http://wnep.com/2016/08/02/half-of-pennsylvanias-roundabouts-show-a-decrease-in-crashes/

I'll be the first to admit I'm no genius, but if half of the roundabouts in Pennsylvania show a decrease in crashes, that means the other half of roundabouts in Pennsylvania either stayed the same or crashes went up.  Pennsylvania hasn't really built any significant roundabouts to date but thought I'd share this news story anyways.  But yeah, flip a coin to determine if a particular roundabout in PA has seen crashes increase or decrease. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 24, 2016, 10:51:09 PM
Yet another 2x2 multi-lane roundabout has been downsized and this time it's in Carmel.  The roundabout at 116th & Illinois has historically been a high crash intersection in the city.  The EB right lane on 116th has been re-striped as a right turn only lane. 

They are downsizing one crash prone 2x2 multi-lane roundabout in Carmel only to construct another 2x2 multi-lane roundabout at Carmel Drive & Rangeline Road (scheduled to be complete this November).  Over the next few years that roundabout will probably make the city's high crash intersection list and they will have to contemplate downsizing it in the future.  Every time i update this chart it's getting more and more yellow (indicating roundabouts that have had circulating lanes removed):

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/untitledcrashrate_zpsmgwaqcjk.png)

Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on August 24, 2016, 11:28:44 PM
The tangent section between the yielding point and the approach curve allows traffic to speed up as they're entering
Perhaps they were more concerned with entry path overlap?  Maybe there is a high percentage of trucks?  Does Wisconsin not encourage the 20' tangent before eoct?

You can prevent entry path overlap without having the tangent occur that far down the entry. Since a picture = 1K words, see Figure 30.17 (pg 63) (http://wisconsindot.gov/rdwy/fdm/fd-11-26.pdf) for Wisconsin's design guidance. Similarly, there are other ways of dealing with higher percentages of trucks, like striping out a gore between the entry lanes. Or, ban vehicles from traveling adjacent to trucks near/within roundabouts as one of Wisconsin's newer laws (https://docs.legis.wisconsin.gov/2015/related/lcactmemo/act139) does.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on August 24, 2016, 11:38:33 PM
Half of Pennsylvania’s Roundabouts Show A Decrease In Crashes
http://wnep.com/2016/08/02/half-of-pennsylvanias-roundabouts-show-a-decrease-in-crashes/

I'll be the first to admit I'm no genius, but if half of the roundabouts in Pennsylvania show a decrease in crashes, that means the other half of roundabouts in Pennsylvania either stayed the same or crashes went up.  Pennsylvania hasn't really built any significant roundabouts to date but thought I'd share this news story anyways.  But yeah, flip a coin to determine if a particular roundabout in PA has seen crashes increase or decrease.
Half of... ten.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 24, 2016, 11:42:14 PM
Every time i update this chart it's getting more and more yellow (indicating roundabouts that have had circulating lanes removed):

You can highlight the Steptoe Roundabout in Washington. Circulating lanes were removed from two approaches in mid-July.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 24, 2016, 11:59:20 PM
Half of Pennsylvania’s Roundabouts Show A Decrease In Crashes
http://wnep.com/2016/08/02/half-of-pennsylvanias-roundabouts-show-a-decrease-in-crashes/

I'll be the first to admit I'm no genius, but if half of the roundabouts in Pennsylvania show a decrease in crashes, that means the other half of roundabouts in Pennsylvania either stayed the same or crashes went up.  Pennsylvania hasn't really built any significant roundabouts to date but thought I'd share this news story anyways.  But yeah, flip a coin to determine if a particular roundabout in PA has seen crashes increase or decrease.
Half of... ten.

Did i say there was more than ten?  I got a hunch if i told you the sun rises in the east you would argue it rises in the west...  that's just the kind of person you are.  Anyways, Pennsylvania really hasn't gotten into the roundabout game and have stuck with constructing little hodunk roundabouts.  I don't even think Pennsylvania has a multi-lane roundabout.  I'm not at all surprised only ten roundabouts were analyzed (apparently you are???... i don't know what to make of your posts anymore lordsutch). 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 25, 2016, 12:01:34 AM
Every time i update this chart it's getting more and more yellow (indicating roundabouts that have had circulating lanes removed):

You can highlight the Steptoe Roundabout in Washington. Circulating lanes were removed from two approaches in mid-July.

Thanks for the info Jake.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on August 25, 2016, 03:37:42 AM
Yet another 2x2 multi-lane roundabout has been downsized and this time it's in Carmel.  The roundabout at 116th & Illinois has historically been a high crash intersection in the city.  The EB right lane on 116th has been re-striped as a right turn only lane. 

Don't confuse temporary changes during US 31 construction with permanent changes.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 25, 2016, 11:00:20 AM
^You are right (meaning i was wrong lol).  I now see why the 116th & Illinois roundabout was temporary reconfigured during construction at US 31.  If the city were to downsize this roundabout they would likely remove circulating lanes along the N/S leg as opposed to the E/W. 

It will be interesting to see how the 2x2 roundabout at Carmel & Rangeline Road performs once finished.  It could easily become an accident hot spot in the city.  To all my Carmel friends, why is it so difficult to find intersection crash data for Carmel's intersections?  I don't know how many total and injury crashes Carmel & Rangeline Road has had over the past 5 years, but it would be pertinent information moving forward in accessing how effective the new 2x2 roundabout will be. 
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on August 25, 2016, 03:05:21 PM
Yes as I mentioned earlier in the thread we are just finishing up from 5 years of US 31 construction which had major impacts on local traffic flows (mainly Westfield during the first half of the project and mainly Carmel during the second half, but some overlap).  So I'd be very cautious about making year to year comparisons on accident rates on anything near US 31 during the period of extended disruption.   Quite a bit of local traffic moved from US 31 to Spring Mill, Illinois, and Pennsylvania during the project period.  Also Illinois street south of 111th is a newly constructed connection to 106th, so there is now through traffic on Illinois that didn't previously exist.

The accident rate on the I 465 to US 31 ramps has also been off the charts lately due to the construction conditions.   Now that the ramps are nearing final completion (a little bit of final paving yet to do and two lanes open at the merge onto US 31 instead of one) I would expect those rates to drop off some.   The US 31 to I 465 Eastbound ramp and Meridian North to I 465 Eastbound ramp are now in much better shape as well, with a dedicated lane for each with no merging required in the final configuration.

Also apologies if my 3:30 am response was a bit short.  Couldn't get to sleep last night after all the local tornado activity so I was a bit toasty from being up too late. :spin:

Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on August 25, 2016, 06:54:15 PM
Did i say there was more than ten?  I got a hunch if i told you the sun rises in the east you would argue it rises in the west...  that's just the kind of person you are.  Anyways, Pennsylvania really hasn't gotten into the roundabout game and have stuck with constructing little hodunk roundabouts.  I don't even think Pennsylvania has a multi-lane roundabout.  I'm not at all surprised only ten roundabouts were analyzed (apparently you are???... i don't know what to make of your posts anymore lordsutch). 

My point is generalizing (drawing broad conclusions from a set of data) from ten cases is stupid, especially when there's no particular reason to believe Pennsylvania's roundabouts are substantially different from roundabouts in other states (or road users in Pennsylvania are substantially different from those in other states), particularly neighboring ones.

Now if Pennsylvania was doing something that substantially deviated from the FHWA guidance or what other states were doing, it might be worthwhile to isolate what's going on in Pennsylvania, but otherwise what you'd really want to do is add Pennsylvania's data on its roundabouts to the data on roundabouts on other states and use that for a comprehensive analysis. Then you could look at what intersection-specific factors (# of entry lanes per leg, # of circulating lanes, # of lanes, presence/absence of various traffic control devices, diameter of circulating roadway, presence/absence of visual obstructions in center, painted versus substantive dividers, presence/absence of segregated bike and pedestrian facilities, lighting/lack of lighting, overall vehicle volume, truck volume, speed limits on entry roadways, ...) seem to drive crash rates (say with a regression model) and go from there... something you can't really do with 10 data points because the number of meaningful factors that vary between cases exceeds the number of cases being analyzed. And more cases lets you deal with the fact that serious accidents and fatalities are relatively rare events, and thus the law of large numbers doesn't kick in as quickly (i.e. you need more cases to establish that a series of rare events aren't just due to random chance).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 26, 2016, 08:26:02 AM
Did i say there was more than ten?  I got a hunch if i told you the sun rises in the east you would argue it rises in the west...  that's just the kind of person you are.  Anyways, Pennsylvania really hasn't gotten into the roundabout game and have stuck with constructing little hodunk roundabouts.  I don't even think Pennsylvania has a multi-lane roundabout.  I'm not at all surprised only ten roundabouts were analyzed (apparently you are???... i don't know what to make of your posts anymore lordsutch). 

My point is generalizing (drawing broad conclusions from a set of data) from ten cases is stupid, especially when there's no particular reason to believe Pennsylvania's roundabouts are substantially different from roundabouts in other states (or road users in Pennsylvania are substantially different from those in other states), particularly neighboring ones.
Yet any DOT will happily report how much safer roundabouts are when there are 19 accidents on roundabout compared to 20 on signalized intersection before that.
It is very difficult to obtain reliable data on real life objects. It is easy to have two identical cages with 20 mice each. It is much more difficult to have 2 identical groups of 20 people - someone will move, someone goes on diet, gets another job etc - although clinical trials of new drugs attempt to do that with reasonable success.  It is almost impossible to have 20 identical interchanges in 2 identical towns - because there are no identical towns with identical traffic patterns to begin with.
It is still possible to extract some information from large datasets, but often there is no interest and/or knowledge required to do that, I am not sure if there is even data collection system in place...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 26, 2016, 03:00:23 PM
For a long time I never questioned the safety benefits of roundabouts.  The national studies said that there was a big decrease in injury crashes and a drop in total crashes.  Worst case was that roundabouts would see about the same number of crashes as the intersection they replaced but the crashes would be less severe resulting in fewer injury accidents.  Even a slight increase in total crashes would be ok in my mind since there would be a reduction in injury crashes.  But then I started reading articles about how some roundabouts were seeing crashes triple and quadruple.  In the Ann Arbor roundabout there was a 10 fold increase in crashes (going from 17 crashes before the roundabout to 170 crashes after).  The crash results of these more complex roundabouts weren’t matching the national studies.  I had to find out why.

The main IIHS roundabout study was weighted heavily towards single-lane and simple multi-lane roundabouts (where main-street has multiple circulating lanes but side-street only has one circulating lane… ie. a 2x1 roundabout).  Some of the roundabouts being built today are much more complex than the roundabouts analyzed in the IIHS study.  Most of my posts have focused on a very specific type of modern roundabout — roundabouts with two-circulating lanes throughout the entire roundabout.  I wanted to see if these complex multi-lane roundabouts have the same safety benefits as the national studies suggest.  After querying out a database of over 5,000 roundabouts, I came up with a list of roughly 50 roundabouts that met specific criteria.  From there I found crash rates for roughly half of them.  The average crash rate for these complex multi-lane roundabouts is 4.09.  Just to put that crash rate into perspective, MassDOT reported that their statewide crash rate at signalized intersections is 0.77.  Interestingly, there is an inverse relationship between traffic volumes and the crash rates of signalized intersections.  Some may argue that if I looked at the highest volume signalized intersections in Massachusetts that they too would have high crash rates, but the research suggests the exact opposite would happen.  There is safety in numbers at signalized intersections.

Agencies don’t like to see crash rates exceed 2.0 MEV and a crash rate of 4.09 is unacceptable to most road agencies.  If agencies knew in advance that a roundabout they were proposing would have a crash rate of 4.09 after construction they probably wouldn’t build it in the first place (and i'm talking about looking at crash data years after construction is complete).  Should these 2x2 and 3x2 roundabouts be built in the first place if they end up having crash rates that are exceedingly high?  The problem is most agencies probably don’t recognize there is a problem.  They truly believe that there will be a reduction in crashes since that is what the national studies told them.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 26, 2016, 04:43:38 PM
Mayor Mike Moore says roundabout in Jeffersonville was a 'bad idea'
http://www.wdrb.com/story/32722447/concerns-about-jeffersonville-roundabout

It’s hard to gain public support for roundabouts when the Mayor says the roundabout was a “bad idea” .   Mike has every right to say what he did as the roundabout has been the site of 134 crashes in the first 9 months of operation.  In response, INDOT gave the “learning curve”  argument saying that it can take up to 12 months for people to get used to a new roundabout configuration.  It’s nothing more than wishful thinking that crashes will go down.  A complex 3-lane roundabout was built at the terminus of M-5 in Commerce, Michigan in 2011.  Ever since then it’s been common for the roundabout to experience over 100 crashes a year.  In 2015 it was the highest crash prone intersection in the entire state of Michigan with 186 total crashes.  Michigan drivers have had 4 years to learn the roundabout, yet there is still a reported crash every other day at this roundabout.  How long does this supposed “learning curve”  take?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 28, 2016, 11:12:42 AM
Gatineau roundabout logs most crashes of any intersection in Quebec
352 crashes – 213 of them resulting in major damage – occurred there over 5-year period
http://www.cbc.ca/news/canada/ottawa/worst-quebec-intersection-1.3735210

With the Allumettières and Saint-Joseph Blvd. roundabout averaging over 70 crashes a year, this 2x2 multi-lane roundabout has a crash rate approaching 5.0 MEV.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 29, 2016, 11:27:40 AM
The Lakeville, MN roundabout at CSAH 50 / CSAH60 has been open for a year now.   According to a recent article, there have been 127 crashes in the first 10 months of operations.  In 2011, Dakota County put together an intersection study and came up with the following crash predictions for the roundabout alternative:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/MN50-60_zpskbeu6bhw.png)
https://www.co.dakota.mn.us/Transportation/RoadStudies/Documents/CR50-CR60FullReport.pdf
http://sunthisweek.com/2016/07/15/some-drivers-still-adjusting-to-lakeville-roundabout/

The study predicted the roundabout would experience 7 PDO crashes and a crash rate of 0.44 for the “full planned growth”  period.  Assuming an AADT of 52,000, 127 crashes would equate to a crash rate of 6.69.  Put another way the current crash rate is 1400% higher than the study predicted.  It would take 19 years of 7 PDO crashes (19 x 7 = 133) to catch up to the current number of crashes that took place in the roundabout’s first year of operation. 

There was another crash prone 2x2 multi-lane roundabout in Richfield, Minnesota that underwent a lot of study and the lessons learned from that roundabout were incorporated into the Lakeville design.  Even though Minnesota’s best practices for roundabout design were included in the Lakeville roundabout, total crashes are still way too high.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 29, 2016, 02:40:08 PM
If you think about it, the leg of a large traffic circle resembles a standard T-intersection.  Drivers at a T-intersection can safely turn into the right lane even when there is an approaching vehicle in the left lane.  The problem is drivers are treating modern roundabouts the same way they treat large traffic circles.  The driver turning into the right lane just assumes the left-lane driver will continue circulating around the circle, which is wrong.  This picture really highlights the “circular road”  misconception and was captured from a webinar Washington County, Minnesota put together.   It touches on a lot of the issues being discussed in this thread:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Untitled33_zpsqelcei11.png)

Below is the full hour long webinar for anyone interested along with some excerpts I found most interesting.


Quote
5:30  The Radio Drive roundabout… “was averaging 40 crashes per year which was very alarming.  By and large they were certainly all very minor crashes; low speeds, low impact; but certainly from a public relations perspective as far as wanting to implement more roundabouts to help promote traffic safety, this was really a problem and something that we had to address.”

7:46  Why is the difference between a modern roundabout and traffic circle important?  … “it is important because especially as you start to get multiple lanes involved, the legal operations and the proper driver behavior we expect are very different between these two.  A single lane configuration can kind of be safely ignored but in multi-lane conditions it is certainly a problem.”

17:08 Prof Hourdos discusses some of the changes made to the 66th & Portland roundabout.  He mentions the turn arrows were changed from “fish-hooks”  to the standard style.  However, if you look at the most recent aerial imagery they have switched back to the “fish-hook”  style. 

21:01 Discusses the results of the 66th & Portland roundabout study.  “The before and after study happened in two stages.  We collected video on the before… 3 months after the changes… and one year after.  There was a slight reduction in yield violations in the immediate 3 month after study.  Unfortunately these were not sustained in the one year after, in which case we actually saw a 30% increase in yield violations.”  

23:20  “Because we did a lot of changes [to the 66th & Portland roundabout] at the same time, one clue that led us to believe that the additional signs (probably the change of the “fish-hook”  signs to the straight) and the extension of the solid line at the entrance (was effective) is that at the same time we saw a reduction in violations we also saw a similar reduction to the incorrect lane choice. 

24:25 Conclusion from Richfield is the changes did not have an effect on yield violations but showed improvement on incorrect lane change and turning violations.
 
26:05 Extend analysis done in Richfield to three additional roundabouts to solidify Minnesota’s understanding of what solutions work to reduce crashes at multi-lane roundabouts. 
-University Dr & 5th Ave in St. Cloud
-Hwy 22 at Adams St and Madison Ave in Mankato
-50/60 Roundabout in Lakeville

28:10  "The roundabout in Lakeville implemented some of the guidance provided from Richfield.  They did use the straight arrows instead of the fish-hook arrows and they also extended the solid line 100 feet from the yield line.  This roundabout also has overhead lane designation signs, which is different from the Richfield roundabout (which did not have overhead signs)."
 
31:02  I noticed it says changes in signs and lane markings took place a year after the roundabout in Mankato opened and data collections was repeated.  Agencies are quick to argue that the first year of crash data may have a disproportionately high number of crashes as drivers get use to using the roundabout.  Yet it seems like Minnesota is going to analyze any roundabout changes they make and determine their effectiveness by analyzing the before data (first year of roundabout being opened when drivers don’t know how to drive it yet) to after data (roundabout has been opened for a year, and drivers are starting to get used to it).  Agencies shouldn’t have it both ways.

36:59  “Do whatever we can to prevent users from having the “circle road”  misconception.

44:15 “We want to minimize crash opportunities.  We have been doing what we can to avoid these 2x2 configurations.  We originally designed for a 20 year volume which really isn’t a bad thing in a non-roundabout context but just creates some of those opportunities for mistakes.  It’s better to design it for future expansion but don’t build it all now if you don’t need to. “

45:20 Discusses the roundabout diet (downsizing 2x2 roundabouts to 1x2 roundabouts).

47:12 "The current MUTCD standard sign really implies the concept of a "circle road".  Is there a different type of sign that could convey this more effectively?"  He also discusses yellow delineators, spaced out chevrons and different types of striping.  Overall a very interesting webinar and will love to hear the results of their study.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on August 29, 2016, 05:17:34 PM
The roundabout at this ramp (https://www.google.com/maps/@39.9927957,-86.1282836,3a,75y,89.84h,74.22t/data=!3m6!1e1!3m4!1s99YUVbYofVpFZJt9zLaGkA!2e0!7i13312!8i6656) in Carmel on the south end of Clay Terrace has signs that say "to both lanes" under the yield sign.  Unfortunately street view isn't available from the front side of the signs.  The square sign says "to both lanes".  Simple but effective.  Also that street view image is a bit compressed -- there are two full lanes entering at that set of yield signs even though it doesn't look big enough in that image.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 29, 2016, 05:42:05 PM
The roundabout at this ramp (https://www.google.com/maps/@39.9927957,-86.1282836,3a,75y,89.84h,74.22t/data=!3m6!1e1!3m4!1s99YUVbYofVpFZJt9zLaGkA!2e0!7i13312!8i6656) in Carmel on the south end of Clay Terrace has signs that say "to both lanes" under the yield sign.  Unfortunately street view isn't available from the front side of the signs.  The square sign says "to both lanes".  Simple but effective.  Also that street view image is a bit compressed -- there are two full lanes entering at that set of yield signs even though it doesn't look big enough in that image.

Here’s some signage that is used at the Homer Watson & Block line roundabout:
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Homersign_zpslchky2kk.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 30, 2016, 11:20:17 AM
American's take on the Dutch turbo.  This could help reduce the number of failure to yield crashes if the "circular road" misconception described in the webinar really is a problem.
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Dutchstyle_zpseijm18fw.png)
https://www.google.com/maps/@43.3849407,-87.9229875,97m/data=!3m1!1e3
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 30, 2016, 12:26:11 PM
American's take on the Dutch turbo.  This could help reduce the number of failure to yield crashes if the "circular road" misconception described in the webinar really is a problem.

Outside of Victoria International Airport on Vancouver Island, BC, there is a genuine turbo roundabout. You can read more about it in this PDF: http://goo.gl/2gXcGn

Google Maps: http://goo.gl/o7xm5i

(http://i.imgur.com/Qb71CJl.png)

(http://i.imgur.com/arKAA29.png) (http://i.imgur.com/L5wNFoH.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on August 30, 2016, 01:24:16 PM
American's take on the Dutch turbo.  This could help reduce the number of failure to yield crashes if the "circular road" misconception described in the webinar really is a problem.
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Dutchstyle_zpseijm18fw.png)
https://www.google.com/maps/@43.3849407,-87.9229875,97m/data=!3m1!1e3

It may be splitting hairs to some, but I wouldn't classify that one as more than a 2x2 with spirals and right-turn bypass lanes. Turbos tend to feature raised dividers within the circulatory, not just paint.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 30, 2016, 02:56:01 PM
Take a look at these two pictures below.  In both cases the yellow car assumes the blue car in the inner-most lane of the roundabout will continue circulating through the roundabout (“the circular road misconception” ).  With a 2x2 roundabout the assumption can lead to a crash when the blue car actually takes the red path.    However, with a 1x2 roundabout this assumption by the yellow driver doesn’t lead to a crash since both paths the blue car can take is in conflict with the yellow car (so the yellow car is forced to wait regardless.. since it's tough to squeeze two cars into one lane).

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Conflicts_zpssn3x8lpr.png)

This is a fundamental problem I see with 2x2 roundabouts.  How do you design 2x2 roundabouts so the driver in the yellow car knows that the blue car may actually be exiting the roundabout?  In too many cases the yellow car wrongfully assumes the blue car is going to continue circulating around the roundabout and pulls out… leading to a failure to yield crash.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on August 30, 2016, 03:15:06 PM


 In too many cases the yellow car wrongfully assumes the blue car is going to continue circulating around the roundabout and pulls out… leading to a failure to yield crash.


Yep.  When cars don't follow the rules of the road, it does sometimes lead to crashes.  Driver error, not design.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on August 30, 2016, 04:02:16 PM
This is a fundamental problem I see with 2x2 roundabouts.  How do you design 2x2 roundabouts so the driver in the yellow car knows that the blue car may actually be exiting the roundabout?  In too many cases the yellow car wrongfully assumes the blue car is going to continue circulating around the roundabout and pulls out… leading to a failure to yield crash.
Design it as an ACTUAL circular road, and so exiting the roundabout requires indication (using your blinkers) to follow the rules of the road (eg 186 (https://www.gov.uk/guidance/the-highway-code/using-the-road-159-to-203), which is the British rule governing these matters) as you are turning off it!
(https://assets.digital.cabinet-office.gov.uk/media/559af891e5274a155c00001d/the-highway-code-rule-185.jpg)

Also, in the second example you give the yellow car has either the blue car crossing its path, or seeking the same space on the (at that point one-lane) roundabout. So that's driver error, not a design flaw. But I see what you mean.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on August 30, 2016, 04:29:31 PM


 In too many cases the yellow car wrongfully assumes the blue car is going to continue circulating around the roundabout and pulls out… leading to a failure to yield crash.


Yep.  When cars don't follow the rules of the road, it does sometimes lead to crashes.  Driver error, not design.

+1.
How many more clues will the entering driver ignore? Traffic within the circulatory has the ROW. Period. End of story. Doesn't matter if you're in the UK or the US. Secondly, if the circulating driver is not signalling left as their circulating, you assume the worst-case, that they're going to exit. Further, many locales post supplementary plaques "To Traffic From Left" or "To Both Lanes" for this very reason. Not much more can be done from a design standpoint other than removing a circulating lane.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 30, 2016, 06:00:25 PM
How many more clues will the entering driver ignore? Traffic within the circulatory has the ROW. Period. End of story. Doesn't matter if you're in the UK or the US. Secondly, if the circulating driver is not signalling left as their circulating, you assume the worst-case, that they're going to exit. Further, many locales post supplementary plaques "To Traffic From Left" or "To Both Lanes" for this very reason. Not much more can be done from a design standpoint other than removing a circulating lane.

BINGO!  Roundabout diets that eliminate circulating lanes at these 2x2 multi-lane roundabouts are becoming more and more common.  Nobody is suggesting that these high crash rate roundabouts be replaced with traffic signals - instead modify them to become low crash rate roundabouts.  I want to reiterate what Joe Gustafson said in the Minnesota webinar:

Quote
“We want to minimize crash opportunities.  We have been doing what we can to avoid these 2x2 configurations.  We originally designed for a 20 year volume which really isn’t a bad thing in a non-roundabout context but just creates some of those opportunities for mistakes.  It’s better to design it for future expansion but don’t build it all now if you don’t need to.”
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 30, 2016, 06:04:47 PM
How many more clues will the entering driver ignore? Traffic within the circulatory has the ROW. Period. End of story. Doesn't matter if you're in the UK or the US. Secondly, if the circulating driver is not signalling left as their circulating, you assume the worst-case, that they're going to exit. Further, many locales post supplementary plaques "To Traffic From Left" or "To Both Lanes" for this very reason. Not much more can be done from a design standpoint other than removing a circulating lane.

BINGO!  Roundabout diets that eliminate circulating lanes at these 2x2 multi-lane roundabouts are becoming more and more common.  Nobody is suggesting that these high crash rate roundabouts be replaced with traffic signals - instead modify them to become low crash rate roundabouts.  I want to reiterate what Joe Gustafson said in the Minnesota webinar:

Quote
“We want to minimize crash opportunities.  We have been doing what we can to avoid these 2x2 configurations.  We originally designed for a 20 year volume which really isn’t a bad thing in a non-roundabout context but just creates some of those opportunities for mistakes.  It’s better to design it for future expansion but don’t build it all now if you don’t need to.”

That way single roundabout can mean job security for the life of the company.
I think that is really a great approach to burning tax dollars providing safe and efficient road environment!
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 30, 2016, 06:26:59 PM
How many more clues will the entering driver ignore? Traffic within the circulatory has the ROW. Period. End of story. Doesn't matter if you're in the UK or the US. Secondly, if the circulating driver is not signalling left as their circulating, you assume the worst-case, that they're going to exit. Further, many locales post supplementary plaques "To Traffic From Left" or "To Both Lanes" for this very reason. Not much more can be done from a design standpoint other than removing a circulating lane.

BINGO!  Roundabout diets that eliminate circulating lanes at these 2x2 multi-lane roundabouts are becoming more and more common.  Nobody is suggesting that these high crash rate roundabouts be replaced with traffic signals - instead modify them to become low crash rate roundabouts.  I want to reiterate what Joe Gustafson said in the Minnesota webinar:

Quote
“We want to minimize crash opportunities.  We have been doing what we can to avoid these 2x2 configurations.  We originally designed for a 20 year volume which really isn’t a bad thing in a non-roundabout context but just creates some of those opportunities for mistakes.  It’s better to design it for future expansion but don’t build it all now if you don’t need to.

Well that's fine, but what happens in 20 years when (or if) they meet that volume? If they re-stripe that second lane, will it cause another bunch of headaches? Will drivers be well enough used to the roundabout at that point that collisions are pretty much unheard of? Or, do they replace the junction with a signal?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 30, 2016, 07:43:36 PM
^^^
Good questions Jake.  If we are OK with seeing crashes on almost a daily basis at some of these complex roundabouts, then keep building them.  If not, then maybe a traffic signal does becomes a better alternative.  In recent years NW Green Bay has constructed 7 triple-lane roundabouts in about a square mile area.  I think that’s a mistake as triple lane roundabouts have not been well proven.  I can cite 4 triple-lane roundabouts that have already undergone roundabout diets and another triple-laner where a diet is planned.  The triple-lane roundabouts that haven’t had circulating lanes removed are experiencing triple digit crashes each year (like the M-5/Pontiac Trail roundabout in Commerce, Michigan which had 186 crashes in 2015).   It sure seems like there is a limit to how complex a roundabout can be before vehicles start crashing into each other on nearly a daily basis.
Title: Re: Crash prone 'modern roundabouts'
Post by: UCFKnights on August 31, 2016, 11:17:08 PM
I was visiting someone and they drove through one of these high accident 2x2 roundabout while I was with them numerous times. The first time was actually with another person visiting driving and they were directing them back to their house and the locals weren't giving good instruction. I piped up saying "hey, you should probably get in the left lane we're making a left in the roundabout" and the local resident told the driver "no, stay on the right, we're making a right"... and then they proceeded to direct them to make a left... from the right lane. After we went through I again commented we made a left from the wrong lane and they started telling me "no, we exited the roundabout to the right, we just made the 3rd right". I tried to explain how it works but I could not explain to them which lane they should be using. We went through multiple more times with them driving incorrectly, and when I drove with them in the car, they scolded me for using the left lane to make a left in the roundabout "you can't exit the roundabout from the inside lane, if you're on that side you have to get to the right lane before you exit". I thought the signage was reasonable. It had the normal road markings and a pictogram signage, and lane usage signs posted as well, but people clearly just could not understand that you need to make a left from the left lane.

For a lot of drivers, it just is very apparent that it is not intuitive to them, even with signs and current markings, that you can exit a roundabout from the inside lane.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on August 31, 2016, 11:34:40 PM
I was visiting someone and they drove through one of these high accident 2x2 roundabout while I was with them numerous times. The first time was actually with another person visiting driving and they were directing them back to their house and the locals weren't giving good instruction. I piped up saying "hey, you should probably get in the left lane we're making a left in the roundabout" and the local resident told the driver "no, stay on the right, we're making a right"... and then they proceeded to direct them to make a left... from the right lane. After we went through I again commented we made a left from the wrong lane and they started telling me "no, we exited the roundabout to the right, we just made the 3rd right". I tried to explain how it works but I could not explain to them which lane they should be using. We went through multiple more times with them driving incorrectly, and when I drove with them in the car, they scolded me for using the left lane to make a left in the roundabout "you can't exit the roundabout from the inside lane, if you're on that side you have to get to the right lane before you exit". I thought the signage was reasonable. It had the normal road markings and a pictogram signage, and lane usage signs posted as well, but people clearly just could not understand that you need to make a left from the left lane.

For a lot of drivers, it just is very apparent that it is not intuitive to them, even with signs and current markings, that you can exit a roundabout from the inside lane.

That would have driven me crazy.  Sort of like Tim in Monty Python and the Holy Grail: "Look at the bones signs!"
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on September 01, 2016, 05:29:06 AM
(“the circular road misconception” )
I feel that my point that roundabouts should be circular roads, so that those leaving the roundabout signal such has been overlooked thanks to my shiny picture distracting people.

Two lane roundabouts would work better if we address "the circular road misconception misconception"! We don't need to diet them - just engineer them properly and educate drivers on their usage.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 01, 2016, 08:48:01 AM
I was visiting someone and they drove through one of these high accident 2x2 roundabout while I was with them numerous times. The first time was actually with another person visiting driving and they were directing them back to their house and the locals weren't giving good instruction. I piped up saying "hey, you should probably get in the left lane we're making a left in the roundabout" and the local resident told the driver "no, stay on the right, we're making a right"... and then they proceeded to direct them to make a left... from the right lane. After we went through I again commented we made a left from the wrong lane and they started telling me "no, we exited the roundabout to the right, we just made the 3rd right". I tried to explain how it works but I could not explain to them which lane they should be using. We went through multiple more times with them driving incorrectly, and when I drove with them in the car, they scolded me for using the left lane to make a left in the roundabout "you can't exit the roundabout from the inside lane, if you're on that side you have to get to the right lane before you exit". I thought the signage was reasonable. It had the normal road markings and a pictogram signage, and lane usage signs posted as well, but people clearly just could not understand that you need to make a left from the left lane.

For a lot of drivers, it just is very apparent that it is not intuitive to them, even with signs and current markings, that you can exit a roundabout from the inside lane.
I would ask a simple question: who should be using the left lane then? it is there, it is built for a reason (although I wouldn't bet my life on a "reason" part)
Title: Re: Crash prone 'modern roundabouts'
Post by: UCFKnights on September 01, 2016, 11:45:18 AM
Oh I did ask exactly that. There answer to that was its fine to use both lanes when everyone is going straight through the intersection. I then tried to explain what if the car on the right was gonna continue in the circle like you always do and the car on the left decided to go straight, wouldn't there be a collision? And they then proceeded to complain that roundabouts don't make any sense... I didn't manage to convince them to do it right, just that what they're doing is dangerous, but perhaps there is nothing they could do about it.

If you sit at these multilane roundabouts, regardless of the signage, it is clear people just flat out do not understand the lane usage in them more then any others. I was interested to watch it for a little while and the number of vehicles making a left from the right lane is very high. I'd venture to guess that the cause of a lot of the accidents even classified as other things like failure to yield really is improper lane usage. I forgot to mention the other out of town friend who was driving was an out of town cop, who does accident reports and whatnot and he was very unsure what lane he should have been in.

The lack of education on it is just the lack of people understanding and willing to follow the lane markings because they think they're exiting to their right and its unnatural to turn right over another lane that continues on (although they're obviously required to exit as well)

I think to some extent, we see this phenomenon on other roadways too. On highways exits with both an option use lane and a dedicated exit lane, probably 80% of the vehicles exiting are in the right lane, even when there is traffic. Many times when I'm driving with others in the car who are trying to give me directions, they'll say get off next exit, and if I don't get all the way over to dedicated exit lane, they'll start insisting I'm going to miss the exit if I'm using the option lane, I need to be in the exit only lane. Obviously in this case there is no danger to what they're doing and the lane still helps for those who do use it.

I know Orlando put large arrows right at the gore points (https://www.google.com/maps/place/Orlando,+FL/@28.5384948,-81.3389702,3a,20.3y,286.27h,85.95t/data=!3m6!1e1!3m4!1sRWXgz9jLw6FHNvz0s0x45g!2e0!7i13312!8i6656!4m5!3m4!1s0x88e773d8fecdbc77:0xac3b2063ca5bf9e!8m2!3d28.5383355!4d-81.3792365!6m1!1e1) indicating what each lane must do on the highways  I'd like to see that tried on some of these high accident roundabouts to help both those in the roundabout really visualize what they can do in their lane as well as making vehicles entering the intersection cross over the arrow so they understand what they are yielding too. The standard size arrows prior to the gore point just flat out do not get the message across to a significant number of people.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 01, 2016, 01:49:18 PM
I feel that my point that roundabouts should be circular roads, so that those leaving the roundabout signal such has been overlooked thanks to my shiny picture distracting people.

Two lane roundabouts would work better if we address "the circular road misconception misconception"! We don't need to diet them - just engineer them properly and educate drivers on their usage.

Consider these two extreme examples.  The Arc De Triomphe is a large circulating road with T-intersections branching out in all directions.  Drivers instinctively know that once they enter the Arc De Triomphe that it becomes the main circulating roadway (and they must merge to the outer edge of the circle when wanting to make an exit).  The opposite extreme is a little planter island in the middle of an intersection.  To drivers this is a standard intersection with a traffic calming device in the middle.  No driver would view the “planter island”  as the main circulating road.

I guess my point is for a circle to function as a circulating road doesn’t the circle have to be sufficiently large?  A prominent traffic circle in the heart of Paris or Manhattan isn’t really problematic (since traffic is traveling at parking lot speeds to begin with).  However, plopping a large circle in the middle of suburbia isn’t going to solve any problems.  America already has experience with these large traffic circles and by and large they have been a failure.  That’s why most of them have being converted to modern roundabouts, signalized intersections, or full blow interchanges. 

In regards to using a signal indication when exiting a roundabout... that was actually being discouraged by the roundabout expert in the Minnesota webinar:
Quote
“We also would never tell a driver to use a right turn signal to exit a roundabout.  Again, that’s a through movement and we don’t wan to create the impression that it’s a right turn.”
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 01, 2016, 02:13:37 PM
Speaking of roundabouts not actually being a circle here in North America (but rather a series of one-way roads crossing at key points), we ought to look into misleading GPSs: "take the second exit at the roundabout" -- you mean go straight? Even if "straight" is in fact the second exit, might it be wiser to say "continue straight at the roundabout" (especially if, on approach, you see two straight arrows on the pavement)?

I use my signal at a roundabout, but only to indicate a left or right movement (i.e. third exit or first exit). I always indicate before entering the roundabout, disabling the left turn indication after passing the "top" of the roundabout (if the entry is the bottom).
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on September 01, 2016, 02:22:56 PM
No driver would view the “planter island”  as the main circulating road.
They would if it was signed as a roundabout, and the drivers were told to treat roundabouts in that way (though judging by the 'expert' who understands how turbo-roundabouts work, and thinks that's how all roundabouts work, they are being told the opposite).
Quote
I guess my point is for a circle to function as a circulating road doesn’t the circle have to be sufficiently large?
Just as they do at, say, Here? (https://www.google.co.uk/maps/@51.6638962,-0.6014679,3a,75y,128.88h,77.86t/data=!3m6!1e1!3m4!1sQmKY5OaSIQ_LWWpuiNZzRQ!2e0!7i13312!8i6656). OK, some people don't indicate leaving the roundabout every time, but it works fine. I doubt there's a 2-lane roundabout in America that has a smaller central island, but certainly roundabouts in England that have smaller islands also work like this.
Quote
In regards to using a signal indication when exiting a roundabout... that was actually being discouraged by the roundabout expert in the Minnesota webinar:
Quote
“We also would never tell a driver to use a right turn signal to exit a roundabout.  Again, that’s a through movement and we don’t wan to create the impression that it’s a right turn.”
Fecking eejit!

 :banghead: :banghead: :banghead: :banghead:
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 01, 2016, 03:12:26 PM
Speaking of roundabouts not actually being a circle here in North America (but rather a series of one-way roads crossing at key points), we ought to look into misleading GPSs: "take the second exit at the roundabout" -- you mean go straight? Even if "straight" is in fact the second exit, might it be wiser to say "continue straight at the roundabout" (especially if, on approach, you see two straight arrows on the pavement)?
The way I give directions is "make 270 on first roundabout, then 180 on the second one, and 90 on the last one".
Yes, those are actual directions....
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 01, 2016, 08:02:48 PM
A double-lane roundabout in Cheyenne that had 88 crashes in 2015 got some new pavement markings and signage.  They are going from the fish-hook style to the standard arrows.  It’s very likely this change is directly due to the Richfield study.  The problem with the Richfield study is that they made multiple changes to the 66th & Portland roundabout and it’s very hard to know for sure what measures actually worked.  Minnesota is currently reviewing 4 additional 2x2 roundabouts and making changes more incrementally to get a better feel to what changes really provide the greatest reduction in crashes. 

http://www.wyomingnews.com/news/pershing-boulevard-roundabout-gets-new-striping-arrows/article_f7a32b38-5df7-11e6-b1f4-9b36ab4ec578.html

The new pavement markings in Cheyenne may temporary reduce the number of crashes moving forward.  But consider this.  Simply re-striping existing faded markings inside a roundabout can reduce the number of crashes because they stick out better to drivers.  But they will eventually fade and the crashes will go back up.  Researchers may contribute a temporary reduction in crashes and contribute it to whatever “tweak”  they are analyzing (when in fact crashes went down simply because the pavement markings were clearer).  Do these studies consider that the before conditions may be when the roundabout had faded markings and the after was when the pavement markings were new and fresh?  Take a look at the quality of the markings at the Richfield roundabout:

2010
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/2010_zpszjrhowaj.png)


2015
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/2015_zps5hjk8n5q.png)


Agencies spend all this time researching these little roundabout “tweaks” .  Does it really matter though when the pavement markings they decided were so much safer fade to nothing?   If Richfield was so concerned about the crashes at their multi-lane roundabouts they may want to lay down some fresh paint every once and a while.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 03, 2016, 10:35:30 AM

Quote
The modern roundabout design is more efficient than the existing signalized intersection, increasing traffic capacity in the I-35 at 51st Street intersection by 30 to 50 percent, resulting in reduced travel time for motorists. In fact, it is anticipated that once the project is complete, drivers will travel through the 51st Street intersection on average almost four minutes faster than they do today. In addition, the new roundabout design is much safer and expected to reduce the overall crashes by about 35 percent, injury crashes by about 75 percent, and fatal crashes about 90 percent when compared to a traditional signalized intersection.

Instead of a 35% reduction in total crashes there will probably be a 335% increase.  Don't worry though.  After there is a big spike in crashes TxDOT will increase the width of the roundabout striping by 0.5 inches and it will magically solve the crash problem!

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 03, 2016, 12:45:44 PM
Instead of a 35% reduction in total crashes there will probably be a 335% increase.  Don't worry though.  After there is a big spike in crashes TxDOT will increase the width of the roundabout striping by 0.5 inches and it will magically solve the crash problem!

You do understand that the overwhelming amount of data available at this time still supports the construction of large, multi-lane roundabouts, yes? While some northern agencies (and you personally) have begun preliminary investigations as to the safety of multi-lane roundabouts, the FHWA's official stance on roundabouts is that they are still much safer than traditional signalized intersections. You can bitch all you want about the continued construction of these roundabouts, but there's no official wording that condemns them.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 03, 2016, 02:30:44 PM
You do understand that the overwhelming amount of data available at this time still supports the construction of large, multi-lane roundabouts, yes? While some northern agencies (and you personally) have begun preliminary investigations as to the safety of multi-lane roundabouts, the FHWA's official stance on roundabouts is that they are still much safer than traditional signalized intersections. You can bitch all you want about the continued construction of these roundabouts, but there's no official wording that condemns them.

The FHWA seems well aware that there is a PDO crash problem at these roundabouts with 2x2 and 2x3 configurations.  Hillary Isebrands from the FHWA gave a presentation at the 4th Annual International Conference on Roundabouts titled “The Multi-lane Roundabout PDO Dilemma” .  In it she discussed many of the roundabouts that have been discussed on this thread:

http://teachamerica.com/RAB14/RAB1410AIsebrands/index.htm

The FHWA knows there is a crash problem at these 2x2 and 2x3 configuration roundabouts.   Yet that doesn't stop TxDOT from suggesting that the I-35 & 51st Street roundabout will see a 35% reduction in total crashes.  Either TxDOT officials are being misleading to the public or they are ignorant to the latest research on roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: UCFKnights on September 03, 2016, 03:44:58 PM

Quote
The modern roundabout design is more efficient than the existing signalized intersection, increasing traffic capacity in the I-35 at 51st Street intersection by 30 to 50 percent, resulting in reduced travel time for motorists. In fact, it is anticipated that once the project is complete, drivers will travel through the 51st Street intersection on average almost four minutes faster than they do today. In addition, the new roundabout design is much safer and expected to reduce the overall crashes by about 35 percent, injury crashes by about 75 percent, and fatal crashes about 90 percent when compared to a traditional signalized intersection.

Instead of a 35% reduction in total crashes there will probably be a 335% increase.  Don't worry though.  After there is a big spike in crashes TxDOT will increase the width of the roundabout striping by 0.5 inches and it will magically solve the crash problem!
The traffic exiting off of I-35 there is 2 lanes and it enters a 3 lane portion of the roundabout, with it being unclear which lane traffic entering the roundabout are supposed to be in (I can tell, but I could easily see people getting confused). As no traffic is entering the roundabout into that third lane, it seems like that is just going to do more harm then good. It seems like if the 51st st to i35 right turn entrance got its own right turn lane as well to help remove that triple lane it wouldn't decrease capacity at all (perhaps increase it) and help make sure it doesn't end up on the list of crash prone roundabouts. I wouldn't be surprised with the current design to see it needing modification, but it seems like such an easy one to solve.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 03, 2016, 06:37:41 PM
You do understand that the overwhelming amount of data available at this time still supports the construction of large, multi-lane roundabouts, yes? While some northern agencies (and you personally) have begun preliminary investigations as to the safety of multi-lane roundabouts, the FHWA's official stance on roundabouts is that they are still much safer than traditional signalized intersections. You can bitch all you want about the continued construction of these roundabouts, but there's no official wording that condemns them.

The FHWA seems well aware that there is a PDO crash problem at these roundabouts with 2x2 and 2x3 configurations.  Hillary Isebrands from the FHWA gave a presentation at the 4th Annual International Conference on Roundabouts titled “The Multi-lane Roundabout PDO Dilemma” .  In it she discussed many of the roundabouts that have been discussed on this thread:

http://teachamerica.com/RAB14/RAB1410AIsebrands/index.htm

The FHWA knows there is a crash problem at these 2x2 and 2x3 configuration roundabouts.   Yet that doesn't stop TxDOT from suggesting that the I-35 & 51st Street roundabout will see a 35% reduction in total crashes.  Either TxDOT officials are being misleading to the public or they are ignorant to the latest research on roundabouts.

Hillary Isebrands fully admits to the situation being a dilemma: on one hand, multi-lane roundabouts do improve traffic flow, and decrease severe injuries, but they generally see a bump in overall collisions. If the situation wasn't a dilemma, and multi-lane roundabouts universally saw a jump in generic injuries, severe injuries, fatalities, and a decrease in overall traffic flow, then it would be a no-brainer: stop building these things. But, it's not that clear cut. Multi-lane roundabouts have pluses and minuses, and they always will. Every form of traffic control does.

As to the studies that TxDOT cites, while those are, apparently, being proven false by the day, it's simply the most solid data available to them. If the FHWA wants to decrease the amount of multi-lane roundabouts being built, they ought to release a new study that isn't just a bunch of loose data.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on September 06, 2016, 01:01:08 AM
The Arc de Triomphe circle (technically, Place Charles de Gaulle) still follows "priorité à droite," with drivers in the circle required to yield to entering traffic, so it's not a circulating roadway at all.

I think a lot of the issue we're seeing was inadvertently identified by english si upthread: American drivers don't know how to properly signal in roundabouts (and in general don't signal as much as they should anyway). Your direction of exit is supposed to be indicated when entering the circle (if you are not going straight), and you're supposed to indicate exiting as you approach your exit leg.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 06, 2016, 01:12:48 AM
The Arc de Triomphe circle (technically, Place Charles de Gaulle) still follows "priorité à droite," with drivers in the circle required to yield to entering traffic, so it's not a circulating roadway at all.

I think a lot of the issue we're seeing was inadvertently identified by english si upthread: American drivers don't know how to properly signal in roundabouts (and in general don't signal as much as they should anyway). Your direction of exit is supposed to be indicated when entering the circle (if you are not going straight), and you're supposed to indicate exiting as you approach your exit leg.
With tight roundabouts being built today, signalling exit seem meaningless. Blinker interval is too long, and visibility of blinker on the side of a car is limited for downstream traffic. Besides, with fairly large steering inputs, both hands on a wheel at all times seem like a good idea.
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on September 06, 2016, 01:55:25 AM
I think a lot of the issue we're seeing was inadvertently identified by english si upthread: American drivers don't know how to properly signal in roundabouts (and in general don't signal as much as they should anyway). Your direction of exit is supposed to be indicated when entering the circle (if you are not going straight), and you're supposed to indicate exiting as you approach your exit leg.

The lack of signaling is one of the things that really drives me batty with going through roundabouts here.  It dramatically decreases the efficiency of the intersection and causes it to act more like an expensive all-way stop (albeit with fewer conflict points).  My method is for signaling in roundabouts is as follows:


I've heard the theory of "not signaling if going straight" (i.e. the second leg in a standard 4-way roundabout, or the "180" in kalvado's description), but with the way roundabouts are supposed to be designed (with the center island sufficiently obstructing the "straight through" view), and the almost 100% reliable assumption that vehicles on that side have no idea of my intent in that case, it seems like it's as bad as not signaling.  In my experience, there is enough time to react generally with the signals, even with smaller roundabouts, though it can require good reflexes.

A big part of the problem is that several DOTs and agencies that are installing and promoting roundabouts give terrible advice in their little "instructional videos" (and I'll admit--I'm kind of skeptical of building a bunch of intersections that still require instructional videos for the general public).  WSDOT is among the worst offenders.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 06, 2016, 07:03:50 AM
In my experience, there is enough time to react generally with the signals, even with smaller roundabouts, though it can require good reflexes.
Well.. tiny problem is that we're not talking about NASCAR track, this is all about general purpose road. And it has to accomodate not only men in their top shape, but everyone with a license. Including that grey-haired lady in her 70s...
Title: Re: Crash prone 'modern roundabouts'
Post by: Mrt90 on September 06, 2016, 01:11:46 PM
I was visiting someone and they drove through one of these high accident 2x2 roundabout while I was with them numerous times. The first time was actually with another person visiting driving and they were directing them back to their house and the locals weren't giving good instruction. I piped up saying "hey, you should probably get in the left lane we're making a left in the roundabout" and the local resident told the driver "no, stay on the right, we're making a right"... and then they proceeded to direct them to make a left... from the right lane. After we went through I again commented we made a left from the wrong lane and they started telling me "no, we exited the roundabout to the right, we just made the 3rd right". I tried to explain how it works but I could not explain to them which lane they should be using. We went through multiple more times with them driving incorrectly, and when I drove with them in the car, they scolded me for using the left lane to make a left in the roundabout "you can't exit the roundabout from the inside lane, if you're on that side you have to get to the right lane before you exit". I thought the signage was reasonable. It had the normal road markings and a pictogram signage, and lane usage signs posted as well, but people clearly just could not understand that you need to make a left from the left lane.

For a lot of drivers, it just is very apparent that it is not intuitive to them, even with signs and current markings, that you can exit a roundabout from the inside lane.
Your post reminded me of something that I had previously posted, turns out that it was almost one year ago. I think you have a different perception of this now, but your point seems to be that people will do what they think is right, despite the rest signage/road marking, which is basically what I was trying to get across last year. Some people think the outside (and only the outside) lane is for exiting despite what the signs/marking might show, and some people remember that they could "go straight" from the left lane in the last roundabout they went through so they think they can "go straight" from the left lane all the time.  For some reason many folks don't pay attention to the signs/markings, they think every roundabout is the same.

https://www.aaroads.com/forum/index.php?topic=15546.msg2093533#msg2093533

Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 06, 2016, 02:30:33 PM
...I think you have a different perception of this now, but your point seems to be that people will do what they think is right, despite the rest signage/road marking, which is basically what I was trying to get across last year. Some people think the outside (and only the outside) lane is for exiting despite what the signs/marking might show, and some people remember that they could "go straight" from the left lane in the last roundabout they went through so they think they can "go straight" from the left lane all the time.  For some reason many folks don't pay attention to the signs/markings, they think every roundabout is the same.

^^ This. I was almost hit in this roundabout (https://www.google.com/maps/@43.1211071,-89.2998699,3a,75y,64.25h,78.06t/data=!3m6!1e1!3m4!1szMMwRVULVr8W_zjKj1L1Zw!2e0!7i13312!8i6656) by some moron attempting to make a right turn from the left lane. :rolleyes:  In the process, they ignored: a large overhead sign, two regulatory lane signs, two sets of pavement marking arrows, and a sign on the left side specifically prohibiting right turns from the left lane. :pan:
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on September 06, 2016, 06:28:47 PM
Assume other drivers are morons and you won't be disappointed.  And by having that assumption up front it's usually easy to take evasive action.   Even with the occasional moron (they show up at non roundabout intersections too) I far and away prefer the efficiency of a roundabout over other intersection types.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on September 07, 2016, 02:46:43 PM
Well.. tiny problem is that we're not talking about NASCAR track, this is all about general purpose road. And it has to accomodate not only men in their top shape, but everyone with a license. Including that grey-haired lady in her 70s...
In my experience, grey haired ladies in their 70s (and 80s) tend to be those who are most consistently good at signalling at roundabouts. And I'm thinking about ladies that are not spritely (though aren't infirm) and probably shouldn't be on the road due to other issues (vision in the dark, not caring about dints and stuff, etc).

If you can't react quickly enough to signal your exit, then - to put it bluntly - you are a car crash waiting to happen and shouldn't be on the road. If the car in front stops suddenly, you'd be going into the back of it!

The big issue with signalling is that 'expert' engineers want turbo roundabouts, but then stripe them like regular 2-lane roundabouts and wonder why people, after they go "don't signal your exit", get confused as to whether a car is exiting and so are unsure and have crashes. But lets go with this idea that drivers are incompetent morons who shouldn't be thought of as capable of doing simple driving tasks unless they are professionals, so why inform them how to use junctions safely. I mean that can't lead to trouble...  :banghead:
Assume other drivers are morons and you won't be disappointed.
Ah, the American way, sadly you will be disappointed as your fatalities per billion km is nearly twice that of the UK (and the UK has stagnated in road safety since it started treating drivers as morons) where they (used to) assume drivers are able to drive cars in a way that doesn't create crashes if they were told how to do so.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 07, 2016, 07:38:09 PM
Well.. tiny problem is that we're not talking about NASCAR track, this is all about general purpose road. And it has to accomodate not only men in their top shape, but everyone with a license. Including that grey-haired lady in her 70s...
In my experience, grey haired ladies in their 70s (and 80s) tend to be those who are most consistently good at signalling at roundabouts. And I'm thinking about ladies that are not spritely (though aren't infirm) and probably shouldn't be on the road due to other issues (vision in the dark, not caring about dints and stuff, etc).

If you can't react quickly enough to signal your exit, then - to put it bluntly - you are a car crash waiting to happen and shouldn't be on the road. If the car in front stops suddenly, you'd be going into the back of it!

The big issue with signalling is that 'expert' engineers want turbo roundabouts, but then stripe them like regular 2-lane roundabouts and wonder why people, after they go "don't signal your exit", get confused as to whether a car is exiting and so are unsure and have crashes. But lets go with this idea that drivers are incompetent morons who shouldn't be thought of as capable of doing simple driving tasks unless they are professionals, so why inform them how to use junctions safely. I mean that can't lead to trouble...  :banghead:
I just did some timing on my favorite roundabout. It took me 4.7 second to make a 270 on a circle. That basically stands for 2 seconds between exits - and that is the maximum time for the signal to operate. Given that it takes some time to actually switch the signal on, and 60/minute blink rate, we're talking about less than 2 flashes going out before exiting - and probably about 1 before commiting to exit. Do you think it is actually helpful for an observer? Even assuming interested party can actually see the signal (hint - they don't) 

Quote
Assume other drivers are morons and you won't be disappointed.
Ah, the American way, sadly you will be disappointed as your fatalities per billion km is nearly twice that of the UK (and the UK has stagnated in road safety since it started treating drivers as morons) where they (used to) assume drivers are able to drive cars in a way that doesn't create crashes if they were told how to do so.
As for fatal crash rate... You may want to look at the numbers a little bit deeper. Simpliest division of numbers is rural vs urban areas. If you look at urban numbers, they are just a bit higher than UKs, while rural are 2.5x higher than urban.
Thinking about it, what does rural stands for? lower population density, longer trips, more fatigue per driver. Unfortunately detailed statistics on smaller than country basis is not really available with per-km rates. But, if you think about it, Scotland has a notably higher accident rate than England - again for lower population density.
With longer drives in UK - such as London-Glasgo being on par with what some people drive to work in US - that looks like a fairly reasonable thought.
As for drivers being treated as morons.. If you're a more or less typical representative of UK driving public, looks like that was, sadly, an unavoidable move.. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 07, 2016, 07:59:37 PM
With longer drives in UK - such as London-Glasgow being on par with what some people drive to work in US - that looks like a fairly reasonable thought.

What the fuck? No one drives 7 hours to work.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on September 08, 2016, 03:36:38 AM
What the fuck? No one drives 7 hours to work.
Indeed! And it's not like you don't get regular long trips to work in the UK. Add in that congestion is higher - even a thirty mile freeway trip on the M25 can take 90 minutes at rush hour and so this fatigue issue being higher in the US is nonsense.

And if you want large US-style countries with big distances, then Sweden has a lower fatality rate than the UK.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 08, 2016, 06:15:33 AM
With longer drives in UK - such as London-Glasgow being on par with what some people drive to work in US - that looks like a fairly reasonable thought.

What the fuck? No one drives 7 hours to work.
Just came across article about San Jose cops commuting from Reno NV. With real estate prices in Silicon valley, commute distance grows out of control...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 08, 2016, 11:56:57 AM
The 161-Riverside Drive roundabout in Dublin, OH was opened on August 13rd and in 23 days has been the site of at least 10 crashes including at least one injury accident (Dublin Police twitter feed reported an injury motorcycle accident in the roundabout on September 5).

http://www.thisweeknews.com/content/stories/dublin/news/2016/09/06/route-161-riverside-roundabout-dublin-addressing-signs-after-accidents.html

This is what Dublin officials were saying before the roundabout was constructed:
Quote
“They improve safety.  We will reduce crashes.  It won’t eliminate crashes.  The frequency of the crashes will be reduced and the severity will be reduced, of the crashes, meaning the number of injury related type crashes will be substantially reduced.”

-Jeannie Willis, Engineering Manager, City of Dublin

Assuming the number of crashes continue at their current pace the roundabout would be the site of 159 crashes in the first year.  A roundabout in Lakeville, MN had a similar poor opening with reports of 7 crashes in the first week of operations.  Since that time, the Lakeville roundabout has been the site of 127 crashes in just 10 months (even 10 months out, that Lakeville roundabout is experiencing double digit crashes a month).  Is this Dublin triple-lane roundabout going to experience a similar fate as the Lakeville roundabout?  Maybe Jeannie Willis will understand that triple-lane roundabouts don't reduce total accidents (too bad she didn't make that clear to the public when promoting the roundabout before it was constructed).
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on September 08, 2016, 12:40:20 PM

Assuming the number of crashes continue at their current pace the roundabout would be the site of 159 crashes in the first year.


You know what they say happens when you assume?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 08, 2016, 02:55:53 PM
^^^
This is what i said when a roundabout in Lakeville MN had a lot of crashes shortly after opening...

After two months of operation, a double-lane roundabout in Lakeville, Minnesota has tallied up 44 crashes.  Traffic counts at the roundabout are about 30,000 vehicles per day.  This equates to a crash rate of 24.1 MEV.  The crash rate should drop as drivers become more familiar with the roundabout - but even still - this is a horrible initial result.  It will be interesting to track the crashes over time at this roundabout. 

(http://sunthisweek.com/wp-content/uploads/sites/23/2015/08/image.jpg)
http://sunthisweek.com/2015/11/05/number-of-lakeville-roundabout-accidents-drop/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+Thisweeklivecom+%28ThisweekLive.com%29

People responded saying it's too early to judge the effectiveness of the Lakeville roundabout based on just a few months of crash data.  That's a fair argument.  But now that the Lakeville roundabout has been around for a year, the roundabout is STILL experiencing double digit crashes a month.  So what started as a horrible initial result remains a very bad result even a year on.  Now we get to go through the same debate with this triple lane Dublin roundabout. 

Rothman, i have a question.  Can you cite a single example of a 2x2 or 2x3 roundabout that has a crash rate below 1.0 MEV?  That should be easy to do.  Besides, most signalized intersections - even extremely busy intersections - have a crash rate below 1.0.  Why is it so hard to find a multi-lane roundabout with a crash rate below 1.0 MEV?  So i'm waiting for your response.  You cite a 2x2 or 2x3 configuration roundabout that doesn't have vehicles crashing into each other on a near daily basis.  Jeannie Willis was trying to convince the public that total crashes will actually go down at this roundabout.  You probably still believe her.

EDIT:  That Lakeville roundabout was designed based on the lessons learned in the Richfield study.  It was designed based on the latest best practices for roundabout design in Minnesota yet you still had 44 people crashing into each other in the first 2 months and 127 crashes in the first 10 months.  What a shock.  :-o   Using standard arrows vs. fishhook arrows really hasn't seemed to solve anything.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on September 08, 2016, 05:15:26 PM
Just came across article about San Jose cops commuting from Reno NV. With real estate prices in Silicon valley, commute distance grows out of control...

San Jose-Reno is 4-5 hours except on days with Tahoe traffic (I just drove that exact route in June). And you could ride the train. Or live a hell of a lot closer for the same money or less - California's generally expensive, but there's plenty of areas closer to San Jose that have cheaper real estate than Reno. Maybe these cops don't want to live in Modesto or Merced but that's another issue.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 08, 2016, 06:24:47 PM
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/161-riverside%20drive_zpsazvivt2f.png)
http://dublinohiousa.gov/dev/dev/wp-content/uploads/2014/02/SR-161-Riverside-Drive-Intersection-Summary.pdf

As a signalized intersection, the 161-Riverside Drive intersection had a crash rate of 0.98 MEV, or about 1 crash per month.  After 23 days as a roundabout, the intersection already has double digit crashes.  What sounds like a higher crash frequency to everyone…1 crash a month or 10 crashes in 23 days?  Rothman, I’m still waiting for you to cite a 2x2 or 2x3 configuration roundabout with a crash rate below 1.0 MEV.  Based on the current crash numbers, it’s obviously not going to be the 161-Riverside Drive roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 08, 2016, 06:38:27 PM
That's exactly what's being argued though.  Listen to what Jeannie Willis has to say about the expected safety benefits of a 3-lane roundabout currently under construction in Dublin, Ohio (6A touched on this roundabout previously in this thread).  What are the residents of Dublin to think if her predictions don't come to pass?  At that point, who cares right?  It will already be constructed.

Well, I can't speak for the specific roundabout being built; it's entirely possible that the existing intersection is so dangerous that it will reduce both the absolute frequency and severity of crashes (the data suggest some roundabouts do lead to less crashes than the intersections they replaced, and without systematically distinguishing between what the previous intersection type was it's hard to predict which will reduce crashes and which will lead to more crashes).

Assuming this is the intersection in question (https://www.google.com/maps/place/Dublin,+OH/@40.0995925,-83.1097332,250m/data=!3m1!1e3!4m2!3m1!1s0x8838ecc4d450a11f:0xc2176815689028!6m1!1e1), given the weird angle of the existing intersection I suspect the multi-lane roundabout will be an improvement on both scores.

There have already been 10 crashes at the 161-Riverside roundabout in the first 23 days.  Even if there are only 2 more crashes over the next 342 days (365-23) the roundabout will have the same crash rate as the pre-roundabout condition.  Lordsutch, do you really believe there will only be 2 crashes at the 161-Riverside Drive roundabout over the next 342 days?  Personally, I suspect there will be more than 2 crashes over the next 342 days.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on September 12, 2016, 08:13:59 AM
All I was pointing out was that it was an obviously gross assumption you were making about a crash rate continuing at a current pace.  Anyone with any background in data analysis knows that such assumptions are quite tentative with any phenomenon.

That all said, I'm no expert in finding location-specific accident data, but I'd wonder about the roundabouts on NY 85 at Maher Road and Blessing Road, especially in the recent couple of years.  Just going by my own limited experience, it seems those 2 x 2 roundabouts have been working pretty smoothly.  Don't know what their crash rates are, but I'd hypothesize that they're at least lower than the one at NY 140.

Where did you get the continuing crash rate for the Lakeville roundabout?

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 12, 2016, 08:50:50 AM
All I was pointing out was that it was an obviously gross assumption you were making about a crash rate continuing at a current pace.  Anyone with any background in data analysis knows that such assumptions are quite tentative with any phenomenon.

That all said, I'm no expert in finding location-specific accident data, but I'd wonder about the roundabouts on NY 85 at Maher Road and Blessing Road, especially in the recent couple of years.  Just going by my own limited experience, it seems those 2 x 2 roundabouts have been working pretty smoothly.  Don't know what their crash rates are, but I'd hypothesize that they're at least lower than the one at NY 140.

Where did you get the continuing crash rate for the Lakeville roundabout?

If I remember correctly, there was a table in this thread with one of those rt.85 circles making into top 10 nationwide... I would be more than happy to be proven wrong, though.
Title: Re: Crash prone 'modern roundabouts'
Post by: UCFKnights on September 12, 2016, 09:32:02 AM
Well.. tiny problem is that we're not talking about NASCAR track, this is all about general purpose road. And it has to accomodate not only men in their top shape, but everyone with a license. Including that grey-haired lady in her 70s...
In my experience, grey haired ladies in their 70s (and 80s) tend to be those who are most consistently good at signalling at roundabouts. And I'm thinking about ladies that are not spritely (though aren't infirm) and probably shouldn't be on the road due to other issues (vision in the dark, not caring about dints and stuff, etc).

If you can't react quickly enough to signal your exit, then - to put it bluntly - you are a car crash waiting to happen and shouldn't be on the road. If the car in front stops suddenly, you'd be going into the back of it!

The big issue with signalling is that 'expert' engineers want turbo roundabouts, but then stripe them like regular 2-lane roundabouts and wonder why people, after they go "don't signal your exit", get confused as to whether a car is exiting and so are unsure and have crashes. But lets go with this idea that drivers are incompetent morons who shouldn't be thought of as capable of doing simple driving tasks unless they are professionals, so why inform them how to use junctions safely. I mean that can't lead to trouble...  :banghead:
Assume other drivers are morons and you won't be disappointed.
Ah, the American way, sadly you will be disappointed as your fatalities per billion km is nearly twice that of the UK (and the UK has stagnated in road safety since it started treating drivers as morons) where they (used to) assume drivers are able to drive cars in a way that doesn't create crashes if they were told how to do so.
Out of curiosity, how is a turn signal supposed to help change anyone's behavior in the roundabouts? I signal everywhere except roundabouts, because it isn't intuitive to do so (my car will put out maybe two blinks, probably one, and its surely not helping the person next to me who can't see it, the person behind me likely doesn't care since its not indicating I'm going to be slowing down or anything that will affect them, and the angle of the roundabouts doesn't allow the person at the next entry to see my right turn signal indicating I'm leaving the roundabout until its useless.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on September 12, 2016, 09:43:18 AM
Well.. tiny problem is that we're not talking about NASCAR track, this is all about general purpose road. And it has to accomodate not only men in their top shape, but everyone with a license. Including that grey-haired lady in her 70s...
In my experience, grey haired ladies in their 70s (and 80s) tend to be those who are most consistently good at signalling at roundabouts. And I'm thinking about ladies that are not spritely (though aren't infirm) and probably shouldn't be on the road due to other issues (vision in the dark, not caring about dints and stuff, etc).

If you can't react quickly enough to signal your exit, then - to put it bluntly - you are a car crash waiting to happen and shouldn't be on the road. If the car in front stops suddenly, you'd be going into the back of it!

The big issue with signalling is that 'expert' engineers want turbo roundabouts, but then stripe them like regular 2-lane roundabouts and wonder why people, after they go "don't signal your exit", get confused as to whether a car is exiting and so are unsure and have crashes. But lets go with this idea that drivers are incompetent morons who shouldn't be thought of as capable of doing simple driving tasks unless they are professionals, so why inform them how to use junctions safely. I mean that can't lead to trouble...  :banghead:
Assume other drivers are morons and you won't be disappointed.
Ah, the American way, sadly you will be disappointed as your fatalities per billion km is nearly twice that of the UK (and the UK has stagnated in road safety since it started treating drivers as morons) where they (used to) assume drivers are able to drive cars in a way that doesn't create crashes if they were told how to do so.
Out of curiosity, how is a turn signal supposed to help change anyone's behavior in the roundabouts? I signal everywhere except roundabouts, because it isn't intuitive to do so (my car will put out maybe two blinks, probably one, and its surely not helping the person next to me who can't see it, the person behind me likely doesn't care since its not indicating I'm going to be slowing down or anything that will affect them, and the angle of the roundabouts doesn't allow the person at the next entry to see my right turn signal indicating I'm leaving the roundabout until its useless.

When I have seen turn signals in use, especially the right signal, just that one blink is enough to let me know what that driver should be doing.  I'll still wait though to make sure they commit to the turn...just in case!
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on September 12, 2016, 09:50:24 AM
All I was pointing out was that it was an obviously gross assumption you were making about a crash rate continuing at a current pace.  Anyone with any background in data analysis knows that such assumptions are quite tentative with any phenomenon.

That all said, I'm no expert in finding location-specific accident data, but I'd wonder about the roundabouts on NY 85 at Maher Road and Blessing Road, especially in the recent couple of years.  Just going by my own limited experience, it seems those 2 x 2 roundabouts have been working pretty smoothly.  Don't know what their crash rates are, but I'd hypothesize that they're at least lower than the one at NY 140.

Where did you get the continuing crash rate for the Lakeville roundabout?

If I remember correctly, there was a table in this thread with one of those rt.85 circles making into top 10 nationwide... I would be more than happy to be proven wrong, though.

That was one at NY 140 that I mentioned and, although accidents were indeed frequent in the months after it opened, I'm betting the crash rate has come down even at that one.  That said, it's still a white-knuckler, mainly due to drivers who don't expect you to go "straight" from the inner lane as they try to enter the roundabout.  Have to say it's been a long while since some turkey tried to go around the roundabout from the outer lane, though (i.e., and almost hit me as I proceed "straight" from the inner lane).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 12, 2016, 11:31:52 AM
That all said, I'm no expert in finding location-specific accident data, but I'd wonder about the roundabouts on NY 85 at Maher Road and Blessing Road, especially in the recent couple of years.  Just going by my own limited experience, it seems those 2 x 2 roundabouts have been working pretty smoothly.  Don't know what their crash rates are, but I'd hypothesize that they're at least lower than the one at NY 140.

The roundabouts at NY 85 / Maher Road and NY 85 / Blessing Road are 1x2 roundabouts.  They aren’t true 2x2 roundabouts.  The “failure to yield”  misconception prevalent at 2x2 roundabouts is practically non-existent at 1x2 roundabouts.  Drivers seem to manage pretty well at these simplified 1x2 multi-lane roundabouts.

The 85/140 roundabout is a different animal.  It has two-entry lanes at all 4-legs of the roundabout (making it a true 2x2 roundabout).   It was built in 2007 and went from averaging 9.6 crashes a year before the roundabout to 38.3 crashes after.  The new Slingerlands Bypass was part of the roundabout construction so it’s expected that crashes would go up.  That’s why it’s important to look at crash rates which accounts for any increases in traffic volumes.  Based on the most current crash data, the 85/140 roundabout has a crash rate of 2.62 (assuming 38.3 average crashes and an ADT of 40,000).  Keep in mind that a typical crash rate for a signalized intersection is only 0.8.   Maybe things have improved as of late at this roundabout, but I'll wait for actual crash data before making the determination.

http://www.timesunion.com/local/article/The-roundabout-Is-it-a-vicious-circle-1440833.php


Where did you get the continuing crash rate for the Lakeville roundabout?

From here:  http://sunthisweek.com/2016/07/15/some-drivers-still-adjusting-to-lakeville-roundabout/

There were 44 crashes in the first 2 months after the Lakeville roundabout opened on August 31, 2015.  OK fine.  Big spikes in crashes are to be expected as people get use to the new configuration.  But in May of 2016 there were 19 reported accidents and 12 crashes in the first 22 days of June.  Drivers had nearly a year to get use to the operations and there are still almost 20 crashes a month.  That’s crazy.  It’s concerning that the Lakeville roundabout is experiencing so many crashes since it was designed based on the lessons learned in the Richfield study.  If the Lakeville roundabout is a failure, what 2x2 roundabout is going to be a success?
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on September 12, 2016, 12:49:35 PM
That all said, I'm no expert in finding location-specific accident data, but I'd wonder about the roundabouts on NY 85 at Maher Road and Blessing Road, especially in the recent couple of years.

The roundabouts at NY 85 / Maher Road and NY 85 / Blessing Road are 1x2 roundabouts. 


Oh, duh.  My bad.  That's me trying to think off-the-top of my head on a Monday morning.

Where did you get the continuing crash rate for the Lakeville roundabout?

From here:  http://sunthisweek.com/2016/07/15/some-drivers-still-adjusting-to-lakeville-roundabout/


Thanks.

Also, I'll take the time savings from the building of the NY 85/NY 140 roundabout.  The traffic signals were horrible. :D
Title: Re: Crash prone 'modern roundabouts'
Post by: cl94 on September 12, 2016, 01:01:53 PM
Also, I'll take the time savings from the building of the NY 85/NY 140 roundabout.  The traffic signals were horrible. :D

You can say that about most of the roundabouts in this area. The Glens Falls roundabout used to be a 5-way signalized intersection. Split phasing. Miss the light and you could be sitting there for a few minutes.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 12, 2016, 01:59:55 PM
Here’s an ABC6 news story that indicates the new Dublin roundabout has experienced 15 crashes in the first 20 days.  More than first thought. 

Quote
“While it is always the City’s goal that no crashes occur, it is worth nothing that 99.999% of vehicles have traveled through the roundabout without a crash report.”
http://abc6onyourside.com/news/local/drivers-still-getting-used-to-dublin-roundabout-causing-some-traffic-confusion

That statement is shameful.  Instead of acknowledging the high number of crashes that have occurred at the roundabout, the city spins some BS 99.999% statistic.  Not that the 99.999% statistic isn’t truthful, but it’s incredibly misleading to the public.  They don’t want to say that the current crash rate of the roundabout is 10MEV... but just do some simple arithmetic:

1 million — (99.999% of 1 million) = 10 MEV

Crash rate before roundabout = 0.98
Crash rate 20 days after roundabout = 10.0

The average crash rate for major 2x2 roundabouts in America is roughly 4.0 MEV.  If i had to guess, this Dublin roundabout will settle down around there.  When you have 4x the number of crashes, there's no guarantees you will see a reduction in injury accidents.  Is this Dublin roundabout safer than the signalized intersection it replaced?  I'm not at all convinced.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on September 12, 2016, 03:22:34 PM
The average crash rate for major 2x2 roundabouts in America is roughly 4.0 MEV.  If i had to guess, this Dublin roundabout will settle down around there.  When you have 4x the number of crashes, there's no guarantees you will see a reduction in injury accidents.  Is this Dublin roundabout safer than the signalized intersection it replaced?  I'm not at all convinced.

Your one-man crusade against public relations officers' failure to unduly alarm the public on the basis of 20 days of data is noted. What that has to do with the likely injury or death rate at this particular intersection remains unclear.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 12, 2016, 08:03:51 PM
Well, I can't speak for the specific roundabout being built; it's entirely possible that the existing intersection is so dangerous that it will reduce both the absolute frequency and severity of crashes (the data suggest some roundabouts do lead to less crashes than the intersections they replaced, and without systematically distinguishing between what the previous intersection type was it's hard to predict which will reduce crashes and which will lead to more crashes).

Assuming this is the intersection in question, given the weird angle of the existing intersection I suspect the multilane roundabout will be an improvement on both scores.
^^^
Remember that lordsutch?  A year ago you suspected the Dublin roundabout would reduce the absolute frequency of crashes.  There have been 15 crashes in just 20 days of the new roundabout opening.  Before the roundabout, the intersection averaged 12 crashes a year.  What ever happened to this reduction in crash frequency?   

Your one-man crusade against public relations officers' failure to unduly alarm the public on the basis of 20 days of data is noted. What that has to do with the likely injury or death rate at this particular intersection remains unclear.

Since your one prediction was wrong let’s shift focus to injury crashes and death.  It’s almost as if in your own mind you never suggested that the Dublin roundabout would reduce crash frequency, even though you did.  Anyways, on September 5th the Dublin Police department reported an injury motorcycle crash at the new roundabout.  It wouldn't shock me if the Dublin roundabout averaged an injury crash per month over the next year.  As I recall the Jeffersonville, Indiana roundabout had 9 injury crashes in the first 10 months of operation.  Both the Dublin and Jeffersonville roundabouts are confusing triple-lane clusters of fun and could end up with similar injury crashes.  I wouldn't bet against it.  Before you take that bet lodrsutch, just remember it only took you 20 days to be wrong about the frequency of crashes.
Title: Re: Crash prone 'modern roundabouts'
Post by: cl94 on September 12, 2016, 08:07:08 PM
Well, I can't speak for the specific roundabout being built; it's entirely possible that the existing intersection is so dangerous that it will reduce both the absolute frequency and severity of crashes (the data suggest some roundabouts do lead to less crashes than the intersections they replaced, and without systematically distinguishing between what the previous intersection type was it's hard to predict which will reduce crashes and which will lead to more crashes).

Assuming this is the intersection in question, given the weird angle of the existing intersection I suspect the multilane roundabout will be an improvement on both scores.
^^^
Remember that lordsutch?  A year ago you suspected the Dublin roundabout would reduce the absolute frequency of crashes.  There have been 15 crashes in just 20 days of the new roundabout opening.  Before the roundabout, the intersection averaged 12 crashes a year.  What ever happened to this reduction in crash frequency?   

Your one-man crusade against public relations officers' failure to unduly alarm the public on the basis of 20 days of data is noted. What that has to do with the likely injury or death rate at this particular intersection remains unclear.

So before you suggested the new Dublin roundabout would reduce total crash frequency; but since it's becoming obvious that prediction wont hold water let’s shift the focus to injury crashes and death.  It’s almost in your own mind you never suggested that the Dublin roundabout would reduce crash frequency, even though you did.  Anyways, on September 5th the Dublin Police department reported an injury motorcycle crash at the new roundabout.  It wouldn't shock me if the Dublin roundabout averaged an injury crash per month over the next year.  As I recall the Jeffersonville, Indiana roundabout had 9 injury crashes in the first 10 months of operation.  Both the Dublin and Jeffersonville roundabouts are confusing triple-lane clusters of fun and could end up with similar injury crashes.  I wouldn't bet against it.  Before you take that bet lodrsutch, just remember it only took you 20 days to be wrong about the frequency of crashes.

Crashes typically spike with a change in traffic patterns, especially a significant change. We need to wait a couple years for things to stabilize. The SPUI nearby took 5-7 years to stabilize. Also won't be nearly as bad when the southbound bypass reopens: SB through traffic typically bypasses the intersection altogether, so traffic counts are much higher than normal.
Title: Re: Crash prone 'modern roundabouts'
Post by: UCFKnights on September 12, 2016, 08:40:49 PM
I was reading today that as part of a major redevelopment project, this 6 way intersection  in Winter Park, FL https://www.google.com/maps/@28.5860923,-81.3649353,3a,75y,145.46h,70.31t/data=!3m6!1e1!3m4!1sDsivZ_qYf5EMmiP8uSUI5g!2e0!7i13312!8i6656 is proposed to be converted to a presumably multilane roundabout, likely with 6 exits. Since people can't figure out the lane usage in 4 way 2x2 roundabouts, I can't imagine how they'd figure it out in a 6 way one. Is there  examples of modern roundabouts with more then 4 exits/entrances?

This project is still just a proposal from a developer who bought up a lot of the land around the intersection, I haven't seen any plans yet. I haven't found data for it, but I believe it is currently already a bit of a higher crash intersection.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on September 12, 2016, 09:53:17 PM
You won't have to worry about comparing roundabouts to the traffic signals in Carmel much longer.   Most of the remaining traffic signals are on their way out. (http://carmellink.com/pdfs/maps/CL2-Overview%20map%20ALL-FINAL.pdf)

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 12, 2016, 11:28:42 PM
Crashes typically spike with a change in traffic patterns, especially a significant change. We need to wait a couple years for things to stabilize. The SPUI nearby took 5-7 years to stabilize. Also won't be nearly as bad when the southbound bypass reopens: SB through traffic typically bypasses the intersection altogether, so traffic counts are much higher than normal.

I get what you are saying but the design life of a roundabout is only so long.  Consider the State & Ellsworth roundabout in Ann Arbor.  Before the roundabout the intersection was averaging about 20 crashes per year.  In 2013 the roundabout was built and from 2013-2015 the intersection had 351 crashes.  If nothing had been done to the intersection it would have taken roughly 18 years to rack up the same number of crashes that the roundabout racked up in just 3 years.  In addition, the number of injury crashes in 2014 was higher than the injury crashes that occurred in the 3 years before the roundabout was built.  It’s just a bad result all around.  It’s unlikely the State & Ellsworth roundabout will ever get back down to 20 crashes per year.  The design life of the roundabout will expire before that happens. 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/untitled11ystats_zpse5i7jcwm.png)
http://semcog.org/Data-and-Maps/High-Frequency-Crash-Locations/Point_Id/81016689/view/RoadIntersectionCrashDetail

*I didn't update the chart, but there were 3 injury crashes at the roundabout in 2015.  Maybe nobody else finds this chart problematic but i do.  There was a huge increase in total crashes and no improvement in injury crashes.   A lose-lose from a safety perspective. 



Title: Re: Crash prone 'modern roundabouts'
Post by: cl94 on September 12, 2016, 11:47:37 PM
Of course, another big variable is area population and its effect on traffic volumes. The effect of volume on congestion and accidents is nonlinear and correlation does not always imply causation. In Ann Arbor, there was a pretty significant population growth between the 2010 census and the most recent estimate. Take the Bethlehem example on NY 85/140 that was cited earlier. Not only does that involve a new roadway, but the area has grown quite significantly over the past decade.

I do agree that a higher number of accidents is troubling, especially if it is higher than would be expected if the prior geometry remains. But, at the same time, if we can expect a roundabout to last 20-30 years, it could stabilize at 30% lower than projections for the prior design and still be a net benefit. Typically, the number of total accidents is relatively constant from year to year if corrected for population change. I'm really curious about where the roundabouts will stabilize.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 13, 2016, 09:34:23 AM
I was reading today that as part of a major redevelopment project, this 6 way intersection  in Winter Park, FL https://www.google.com/maps/@28.5860923,-81.3649353,3a,75y,145.46h,70.31t/data=!3m6!1e1!3m4!1sDsivZ_qYf5EMmiP8uSUI5g!2e0!7i13312!8i6656 is proposed to be converted to a presumably multilane roundabout, likely with 6 exits. Since people can't figure out the lane usage in 4 way 2x2 roundabouts, I can't imagine how they'd figure it out in a 6 way one. Is there  examples of modern roundabouts with more then 4 exits/entrances?

The one that comes to mind is the multi-lane Five-Points roundabout in Valparaiso, Indiana.  According to the city, in the 3 years before the roundabout the intersection had 61 crashes involving 11 personal injuries.  The roundabout was constructed in 2013 and had 25 crashes that year.  In 2014, the first full year of operation, the roundabout had 98 crashes.  That’s obviously a big increase in total crashes but I don’t have any injury crash data.  If only 5% of those 98 crashes resulted in an injury, it would exceed the injury crash rate before the roundabout was built.  Roundabouts aren’t void of injury crashes and assuming only 5% of the crashes would lead to an injury is a pretty reasonable assumption.

Quote
Valparaiso Engineering Director Tim Burkman said while it's not pleasing to see that amount of accidents, it's important to note the severity of those 98 collisions were for the most part quite minor. Many fender benders involving rear ends or side swipes were reported, with more than half of the incidents involving reporting a damage estimate of less than $2,500 and 90 percent having a damage estimate of less than $5,000 -- estimate accounts for damage sustained by both vehicles.
The average daily traffic at the roundabout is 34,112 vehicles per day.
"Over the course of the entire year, that's an estimated total of 1.24 million vehicles that pass through five points," Burkman said. "This equates to an accident rate of one per 127,000 vehicles that traveled through the intersection, which is still considered to be quite low."

http://www.nwitimes.com/news/local/porter/nearly-accidents-at-five-points-roundabout-in/article_3aa6e8e3-5fc3-5a0c-9884-bc7c2dedc36a.html

Seriously Tim?  One crash per 127,000 vehicles equates to a crash rate of 7.87 MEV.  That isn’t considered “quite low”  in the engineering community.  In fact, a crash rate of 7.87 MEV is nearly 10x higher than the crash rate of a typical signalized intersection.  Either Tim Burkman is a complete moron who got his degree from the back of a cracker-jack box or he’s lying to the people of Valparaiso.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 13, 2016, 09:42:53 AM
Seriously Tim?  One crash per 127,000 vehicles equates to a crash rate of 7.87 MEV.  That isn’t considered “quite low”  in the engineering community.  In fact, a crash rate of 7.87 MEV is nearly 10x higher than the crash rate of a typical signalized intersection.  Either Tim Burkman is a complete moron who got his degree from the back of a cracker-jack box or he’s lying to the people of Valparaiso.
Indoctrination. Roundabouts are best thing since sliced bread. All the facts support that, and if facts seem to contradict - see above.
I think we'll see statements like "only 5 people died on that intersection in a past year" as circles keep spreading - and yes, that is indeed "only 5" when compared with, for example, murder rate in Chicago.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 13, 2016, 02:43:38 PM
You won't have to worry about comparing roundabouts to the traffic signals in Carmel much longer.   Most of the remaining traffic signals are on their way out. (http://carmellink.com/pdfs/maps/CL2-Overview%20map%20ALL-FINAL.pdf)

The general consensus is that roundabouts are safer than signalized intersections.  I agree with that consensus since the majority of roundabouts in the country are either single lane or simplified multi-lane roundabouts (and Carmel is no exception).  But in recent years more and more 2x2 and 2x3 configurations have been built and there’s growing evidence that these roundabouts aren’t safer.  They have significantly higher crash rates than standard signalized intersections and there are several examples where even total injury crash rates are higher.

When looking at the map in the link you provided, the roundabouts being proposed in Carmel are concentrated in the middle of the city along major 4-lane roads (ie. 116th Street, Range Line Road, Carmel Drive).   Presumably many of these roundabouts will need to have 2x2 configurations to handle the high traffic volumes and perhaps Carmel will even get into the triple roundabout game.  Let’s face it, Carmel has constructed some pretty mundane roundabouts — sure they have built a lot of them — but they are basic.   Crashes at Carmel roundabouts have nowhere to go but up since the city is transitioning towards building more 2x2 configurations (and perhaps even some 2x3’s).  You really think Carmel is immune from high crash rate roundabouts?  Get ready for a future headline “Rangeline Road and Carmel Drive roundabout has most crashes in Hamilton County” . 
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on September 13, 2016, 03:27:01 PM
You won't have to worry about comparing roundabouts to the traffic signals in Carmel much longer.   Most of the remaining traffic signals are on their way out. (http://carmellink.com/pdfs/maps/CL2-Overview%20map%20ALL-FINAL.pdf)

The general consensus is that roundabouts are safer than signalized intersections.  I agree with that consensus since the majority of roundabouts in the country are either single lane or simplified multi-lane roundabouts (and Carmel is no exception).  But in recent years more and more 2x2 and 2x3 configurations have been built and there’s growing evidence that these roundabouts aren’t safer.  They have significantly higher crash rates than standard signalized intersections and there are several examples where even total injury crash rates are higher.

When looking at the map in the link you provided, the roundabouts being proposed in Carmel are concentrated in the middle of the city along major 4-lane roads (ie. 116th Street, Range Line Road, Carmel Drive).   Presumably many of these roundabouts will need to have 2x2 configurations to handle the high traffic volumes and perhaps Carmel will even get into the triple roundabout game.  Let’s face it, Carmel has constructed some pretty mundane roundabouts — sure they have built a lot of them — but they are basic.   Crashes at Carmel roundabouts have nowhere to go but up since the city is transitioning towards building more 2x2 configurations (and perhaps even some 2x3’s).  You really think Carmel is immune from high crash rate roundabouts?  Get ready for a future headline “Rangeline Road and Carmel Drive roundabout has most crashes in Hamilton County” .

When it is all said and done, Carmel will have a total of 5 Signals. One at Main and Rangeline, and 4 along US 421.  421's will never go away unless INDOT wants them to, 2 of these signals will never go away as they are shopping center signals.  I am against the Carmel/Rangeline roundabout, I'm not convinced it will make traffic better.  22,000 cars a day go through that intersection, and there are plans to make rangeline a 2 lane road, which will actually make traffic worse.  Almost none of these decisions are being made by engineers, they're all coming from a mayor who is obsessed. 
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on September 13, 2016, 03:27:39 PM
there are 32 more being built in the next 5 yrs by the way.  My biggest problem with Brainard (the mayor of carmel) is that he incorrectly assumes that the roundabout is the silver bullet to solve ALL intersections, this is simply not true!  There are a few questionable areas all around the city that either a roundabout didn't need to be there at all, or it actually made things worse (from a traffic flow perspective). 
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on September 13, 2016, 04:54:35 PM
Since your one prediction was wrong let’s shift focus to injury crashes and death.  It’s almost as if in your own mind you never suggested that the Dublin roundabout would reduce crash frequency, even though you did.  Anyways, on September 5th the Dublin Police department reported an injury motorcycle crash at the new roundabout.  It wouldn't shock me if the Dublin roundabout averaged an injury crash per month over the next year.  As I recall the Jeffersonville, Indiana roundabout had 9 injury crashes in the first 10 months of operation.  Both the Dublin and Jeffersonville roundabouts are confusing triple-lane clusters of fun and could end up with similar injury crashes.  I wouldn't bet against it.  Before you take that bet lodrsutch, just remember it only took you 20 days to be wrong about the frequency of crashes.

I'll gladly accept a wager that in two year's time, the injury rate for the prior year will be lower than the injury rate the year prior to the roundabout's construction. That would be a fair wager under the standards used for evaluating the safety of intersections by traffic engineers in the United States, which rightly ignore data from the period of construction and driver adjustment to an intersection reconfiguration.

I look forward to you dredging this comment out for discussion and you conceding my win circa 2020, when the rest of us have moved on to other debates.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 14, 2016, 07:10:08 PM
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 14, 2016, 08:11:08 PM
A bunch of triple-lane roundabouts are opening to traffic along Franklin Blvd in Cambridge, Ontario.  Based on the performance of other roundabouts in the region i doubt these will work out too well.  But i just love Marilyn Gummerson honesty lol

"I hate them.  They're useless.  Most people do not even know how to use a roundabout properly... me included".

http://kitchener.ctvnews.ca/mixed-reviews-in-early-days-of-franklin-boulevard-roundabouts-1.3065887

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 16, 2016, 02:12:06 PM
The Dublin roundabout opened on August 13th and this September 14th article indicates that there have been 23 crashes since opening (the intersection only averaged 1 crash per month before the roundabout).  Lordsutch predicted the roundabout would see a reduction in the crash frequency... they were only wrong by a factor of 23.

http://abc6onyourside.com/news/local/dublin-police-targeting-new-roundabout-violators

Anybody who thinks crashes at this complex Dublin roundabout will drop from 23 per month to 1 per month as people get more familiar driving it are complete idiots.  A crash per month would match the pre-roundabout crash rate but it’s not going to happen.  But this is what will happen.  An article will come out in 6 months saying crashes are down at the Dublin roundabout (when compared to the initial spike in crashes) and some idiot will say “see, told you… the roundabout is working fine” .   It’s happened before on this thread.  People have no concept of a what a crash rate is.  They actually think their anecdotal evidence of driving through a roundabout once or twice a day is meaningful.  Here's renegade's through process... "heck, if i haven't seen a crash at the roundabout it must not be that bad".  It is that bad.

I think I'll leave this here ...

http://www.mlive.com/news/ann-arbor/index.ssf/2016/04/road_commission_improves_state.html#incart_river_home

Number of crashes at State and Ellsworth roundabout drops following initial spike

It's getting better.  The idiots are beginning to learn how to navigate it.  And it's not nearly as bad as someone who does not live here makes it out to be.  I have to deal with it every day, and have yet to see an accident.  I don't think anyone has died there, either.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 25, 2016, 10:54:56 AM
When someone says there is a 90% reduction in fatalities at roundabouts they are referencing the safety statistics published in 2000 Insurance Institute for Highway Safety roundabout study.   Here are a few relevant snippets taken from that study:

Quote
For the group of 7 urban multilane roundabouts, however, the estimated effect on all crash severities combined was smaller – a 15 percent reduction. Because injury data were not available for the period before construction of 4 of these roundabouts, overall estimates for changes in injury crashes were not computed for this group of intersections.

The study admits that they didn’t have before injury crash data for 4 of the 7 urban multilane roundabouts included in the study.  Over half of the urban multi-lane roundabouts analyzed in this national study didn’t have before injury crash data. 

Quote
For completeness, partial results also are given for individual conversions in a group. Readers are cautioned about drawing conclusions from these results because there is a significant likelihood that the change in safety for individual conversions is due to chance.

Again, there are so few multi-lane roundabouts analyzed in this IIHS study that it’s difficult to make any meaningful safety conclusions.  The IIHS study only analyzed 3 urban multi-lane roundabouts that had before/after injury crash data.

Quote
Effects on fatal crashes and those causing incapacitating injuries are more difficult to measure due to the small samples, but indications are that such crashes were substantially reduced. For the 20 converted intersections with injury data, there were 3 fatal crashes during the before period and none during the after period. The fatal crashes may have contributed to the fact that the roundabouts were constructed and may therefore contribute to the regression-to-the-mean phenomenon. There were 27 incapacitating injury crashes during the before period and only 3 during the after period. Taking into account the durations of the before and after periods and increases in traffic volume, and adjusting for regression to the mean (estimated to be roughly 22 percent), the observed value of 3 incapacitating or fatal injury crashes during the after period is substantially and significantly less than the 26.6 expected.  The estimated reduction in fatal and incapacitating injury crashes is 89 percent (p<0.001).

It’s a technical way to say they made up the 89% reduction in fatal crashes.  Too little data and too many assumptions were made when coming up with that 89% number.   I get blasted for pointing out that 3 of the last 4 fatal crashes in Carmel have happened inside roundabouts but it’s perfectly fine for agencies to cite that roundabouts reduce fatal crashes by 90% based on questionable IIHS safety statistics.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on September 25, 2016, 04:19:05 PM
We will just have to agree to disagree.  You can continue to get your enjoyment by ranting against our roundabouts.   I'll continue to enjoy the stress free driving without traffic jams, reduced travel times and the improved gas mileage they provide.  As I said before, we are looking forward to the next 32 roundabouts being added (http://carmellink.com/) and have no desire to go back to the stop and go traffic jams at the four way stops and traffic lights that were eliminated by the first 100 roundabouts in Carmel.



Title: Re: Crash prone 'modern roundabouts'
Post by: cl94 on September 25, 2016, 04:52:22 PM
Of course, who knows how many of the roundabout incidents are due to stupidity of contractors and police departments. The NY 85/140 roundabout was on yesterday's Albany meet and the idiot cops in Bethlehem coned off the inner lane and the truck apron. A truck got stuck in there because it couldn't navigate the turn.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 25, 2016, 05:02:44 PM
We will just have to agree to disagree.  You can continue to get your enjoyment by ranting against our roundabouts.   I'll continue to enjoy the stress free driving without traffic jams, reduced travel times and the improved gas mileage they provide.  As I said before, we are looking forward to the next 32 roundabouts being added (http://carmellink.com/) and have no desire to go back to the stop and go traffic jams at the four way stops and traffic lights that were eliminated by the first 100 roundabouts in Carmel.
sure, just don't ask for federal or state  funding when you need to bulldoze them off
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 25, 2016, 07:30:30 PM
We will just have to agree to disagree.  You can continue to get your enjoyment by ranting against our roundabouts.   I'll continue to enjoy the stress free driving without traffic jams, reduced travel times and the improved gas mileage they provide.  As I said before, we are looking forward to the next 32 roundabouts being added (http://carmellink.com/) and have no desire to go back to the stop and go traffic jams at the four way stops and traffic lights that were eliminated by the first 100 roundabouts in Carmel.

sure, just don't ask for federal or state  funding when you need to bulldoze them off

This is the second time you've brought up the cost of demolition. Why does this matter so much? Ideally, you build an intersection that has the longest life span. The development patterns of Carmel fit roundabouts well.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 25, 2016, 08:14:22 PM
This is the second time you've brought up the cost of demolition. Why does this matter so much? Ideally, you build an intersection that has the longest life span. The development patterns of Carmel fit roundabouts well.

They may not rip them out completely but safety improvements can be costly.  Take the Jacaranda Blvd and Venice Road roundabout that was constructed in 2011.  The city just approved $585,000 dollars in federal funds to “fix”  this crash prone roundabout.  It’s only 5 years old and they already got to spend a half million to fix it.

http://www.mysuncoast.com/news/local/jacaranda-roundabout-approved-for-improvements-to-minimize-accidents/article_c52eb3a8-2e26-11e6-ad17-1bbc2c4a7e92.html

Or take the 14th and Superior roundabout that opened in 2012.  They are planning on spending $888,885 to replace temporary fencing in the median with more aesthetically pleasing dividers (they believe the fencing helps slow drivers as they approach the roundabout… but the temporary fencing looks ugly).  In addition, the plan calls for a statue to be built in the middle of the roundabout (the fixed object statue is a nice touch for this “safety improvement” ).  This roundabout is only 4 years old and they are going to spend nearly a million dollars on upgrades. 

http://www.1011now.com/content/news/More-updates-likely-coming-to-14th--Superior-roundabout-373306771.html
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 25, 2016, 08:36:01 PM
We will just have to agree to disagree.  You can continue to get your enjoyment by ranting against our roundabouts.   I'll continue to enjoy the stress free driving without traffic jams, reduced travel times and the improved gas mileage they provide.  As I said before, we are looking forward to the next 32 roundabouts being added (http://carmellink.com/) and have no desire to go back to the stop and go traffic jams at the four way stops and traffic lights that were eliminated by the first 100 roundabouts in Carmel.

There isn’t much common ground between us when you have such a cavalier attitude towards anyone who has been injured or killed at a roundabout.

Those stats sounds reasonable -- you most likely have to be driving impaired, speeding, or doing something else really stupid to get killed in a roundabout.  The high percentage of single vehicle crashes speaks volumes.   Good find on the stats.

You've once again quoted a single vehicle incident as a problem with the roundabout.   If an idiot driver in the middle of the night runs off the road at high speed, how is that the roundabout's fault?

What happened to the concept of personal responsibility?   If you drive like an idiot you live (or die) with the consequences.  These are the same people that would have blown the stop sign and taken out another car when it was a stop controlled intersection -- I'm much happier with them being stopped by an inanimate object rather than another vehicle.

On September 21st Ventura County firefighter Ryan Osler died in a rollover crash at the Highway 246 roundabout east of Lompoc.  He was on his way to fight the Canyon fire at Vandenberg Air Force Base.   Are you going to take the opportunity to call Ryan an “idiot” ?

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 25, 2016, 08:46:42 PM
We will just have to agree to disagree.  You can continue to get your enjoyment by ranting against our roundabouts.   I'll continue to enjoy the stress free driving without traffic jams, reduced travel times and the improved gas mileage they provide.  As I said before, we are looking forward to the next 32 roundabouts being added (http://carmellink.com/) and have no desire to go back to the stop and go traffic jams at the four way stops and traffic lights that were eliminated by the first 100 roundabouts in Carmel.

sure, just don't ask for federal or state  funding when you need to bulldoze them off

This is the second time you've brought up the cost of demolition. Why does this matter so much? Ideally, you build an intersection that has the longest life span. The development patterns of Carmel fit roundabouts well.
Not demolition only, but reconstructing workable traffic pattern would cost what, 2-3 million per circle?
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 25, 2016, 11:26:09 PM
Or take the 14th and Superior roundabout that opened in 2012.  They are planning on spending $888,885 to replace temporary fencing in the median with more aesthetically pleasing dividers (they believe the fencing helps slow drivers as they approach the roundabout… but the temporary fencing looks ugly).  In addition, the plan calls for a statue to be built in the middle of the roundabout (the fixed object statue is a nice touch for this “safety improvement” ).  This roundabout is only 4 years old and they are going to spend nearly a million dollars on upgrades. 

http://www.1011now.com/content/news/More-updates-likely-coming-to-14th--Superior-roundabout-373306771.html

That spending is completely independent of any new safety improvements. What they're proposing are purely aesthetic "improvements" and thus should not be lumped into the total cost of the roundabout as you're attempting to do.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 25, 2016, 11:44:45 PM
On September 21st Ventura County firefighter Ryan Osler died in a rollover crash at the Highway 246 roundabout east of Lompoc.  He was on his way to fight the Canyon fire at Vandenberg Air Force Base.   Are you going to take the opportunity to call Ryan an “idiot” ?

Labels and name-calling aside, I'm very interested to see the final crash report on this one. Based on the media reports I've seen so far, it sounds like it must have been pretty-dense fog, as it looks like that intersection is illuminated, maybe not as bright as other agencies would illuminate an intersection. Further, the warning sign had a flashing beacon, something many roundabouts do not use, yet don't typically have a similar crash issue. Source (http://www.keyt.com/news/firefighter-fatal-raises-roundabout-safety-concerns/41775136)

Quote
Becker said fire truck drivers from outside the area might not know what to expect.

:confused: I'm at a loss for words on that comment.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 26, 2016, 08:44:00 AM
That spending is completely independent of any new safety improvements. What they're proposing are purely aesthetic "improvements" and thus should not be lumped into the total cost of the roundabout as you're attempting to do.

This was taken directly from the City of Lincoln’s Public Works website giving an overview of the project:

Quote
When the 14th and Superior roundabout was initially built and opened to traffic the crash rate was higher than anticipated. We had the configuration of the initial roundabout studied and the results showed that we needed to reduce the number of lanes and also reduce the sight distance at the roundabout. One lane in each direction was removed with traffic control devices. The site distance was limited by constructing chain link fence with slats in the medians.

The devices have been in place for approximately two years. The results show that the crash rate has been reduced significantly by the lane reduction and the fencing. At this point we are moving ahead with making the temporary adjustments to the roundabout more permanent. Concept plans have been developed to show putting tack on median concrete in place of the lane reductions. This will allow us to remove the traffic control devices along the outer lanes. A landscaping plan was developed for the center island of the roundabout and the medians. The landscaping and a short decorative fence have been shown to take the place of the chain link fence.

Along with this work a piece of artwork will be loaned to the city from the Duncans to be placed in the center of the roundabout. Construction on the more permanent fixes for the roundabout could begin as early as Fall of 2016.
https://www.lincoln.ne.gov/city/pworks/projects/14th/superior-safety/

The city is spending money to make the temporary safety adjustments to the roundabout more permanent.  The city wouldn’t be spending all this money on decorative fencing if the crash rate at the roundabout hadn’t been higher than expected when it first opened to traffic.  You can argue that it's not a "safety improvement" but it really is.  The decorative fencing is replacing the temporary chain link fence that was installed a few years ago.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 26, 2016, 09:56:15 AM
That spending is completely independent of any new safety improvements. What they're proposing are purely aesthetic "improvements" and thus should not be lumped into the total cost of the roundabout as you're attempting to do.

This was taken directly from the City of Lincoln’s Public Works website giving an overview of the project:

Quote
When the 14th and Superior roundabout was initially built and opened to traffic the crash rate was higher than anticipated. We had the configuration of the initial roundabout studied and the results showed that we needed to reduce the number of lanes and also reduce the sight distance at the roundabout. One lane in each direction was removed with traffic control devices. The site distance was limited by constructing chain link fence with slats in the medians.

The devices have been in place for approximately two years. The results show that the crash rate has been reduced significantly by the lane reduction and the fencing. At this point we are moving ahead with making the temporary adjustments to the roundabout more permanent. Concept plans have been developed to show putting tack on median concrete in place of the lane reductions. This will allow us to remove the traffic control devices along the outer lanes. A landscaping plan was developed for the center island of the roundabout and the medians. The landscaping and a short decorative fence have been shown to take the place of the chain link fence.

Along with this work a piece of artwork will be loaned to the city from the Duncans to be placed in the center of the roundabout. Construction on the more permanent fixes for the roundabout could begin as early as Fall of 2016.
https://www.lincoln.ne.gov/city/pworks/projects/14th/superior-safety/

The city is spending money to make the temporary safety adjustments to the roundabout more permanent.  The city wouldn’t be spending all this money on decorative fencing if the crash rate at the roundabout hadn’t been higher than expected when it first opened to traffic.  You can argue that it's not a "safety improvement" but it really is.  The decorative fencing is replacing the temporary chain link fence that was installed a few years ago.

You made no mention about adjustments to the concrete in your original post, only the replacement of the temporary fencing/aesthetic improvements...that's what my cost comment was based on. Now the cost seems a tad more understandable, unfortunate, but understandable. Regardless, since you keep harping on the replacement of the fence, the safety improvement has already been made. There is no reason that the chain link fence could not have remained in place. Changing something from "ugly" is not a safety improvement, at least not in an engineering sense.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 26, 2016, 10:52:55 AM
^^^
By the City’s own admission the chain link fencing was a temporary measure.  They never had any intention to keep the chain link fencing in place.  If it was shown to be ineffective at reducing crashes they would have ripped it out.  If it was shown to reduce crashes (as they believe it did) they would replace it with permanent fencing.  But there’s a bigger issue here then what type of fence the city decided to use.  How does the city know the fencing was effective at reducing crashes at the roundabout in the first place?  The problem is at the same time they installed the fencing they removed a circulating lane of traffic inside the roundabout.  Those two changes combined saw a reduction in crashes at the roundabout, but how do we know if the reduction was due to the fencing or the reduction of a circulating lane? 

Luckily, they have added fencing at the most crash prone roundabout in Michigan (186 crashes in 2015).  No other changes were made other than the fencing so we will see if it actually helps reduce the total number of crashes.  By the way, it looks like there was a Police car responding to a crash at the roundabout the day this news report was done (hmmm.... the fences were in place and people are still crashing into each other at this roundabout).  Big shock! 

http://www.wxyz.com/news/region/oakland-county/drivers-have-mixed-feelings-about-new-fences-at-m-5-roundabout
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 26, 2016, 12:01:19 PM
By the way, it looks like there was a Police car responding to a crash at the roundabout the day this news report was done (hmmm.... the fences were in place and people are still crashing into each other at this roundabout).  Big shock! 

No one ever said it would prevent all crashes. There is no such intersection control which will do that.

We get it; quite a few roundabouts have seen an increase in crashes, yet you keep harping on the same old information over, and over, and over. We're also still learning about roundabouts in this country, both from a design and a driver perspective. It doesn't help that we cannot all agree on capacity equations, which has led to some roundabouts being built larger than what they need to be. Unfortunately, there are two big variables that are still in a state of flux: traffic projections and driver behavior at a roundabout -- how to properly account for timid vs. aggressive drivers. And unfortunately, this cannot be tested completely in a laboratory environment.

Are roundabouts perfect? No. Are they a silver-bullet solution? Not even close. What they are is another tool in the toolbox -- a tool which is still working thru some R&D revisions.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 26, 2016, 12:24:46 PM
Are roundabouts perfect? No. Are they a silver-bullet solution? Not even close. What they are is another tool in the toolbox -- a tool which is still working thru some R&D revisions.
Perfectly put. Problem is I don't see  too much R&D  - or that is just me?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 26, 2016, 02:16:03 PM

No one ever said it would prevent all crashes. There is no such intersection control which will do that.

All I did was point out a simple observation — that there was a police vehicle responding to an apparent accident at the roundabout.  I’m not suggesting one way or another if the fencing will be effective at reducing the high number of crashes that are occurring at the M-5 / Pontiac Trail roundabout. 

I am questioning how Lincoln officials knew the fencing was effective at the Superior roundabout when the lane reduction was part of the safety improvement.  I contend that the reduction in crashes may be due to the fact they converted the roundabout from a complex 2x3 roundabout into a simplified 1x2 configuration.   DaBigE, do you know of any literature that suggests the fencing placed down splitter islands can be effective at reducing crashes?  I’ve never seen such a study and would be interested in reading it.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 27, 2016, 01:21:36 AM
I contend that the reduction in crashes may be due to the fact they converted the roundabout from a complex 2x3 roundabout into a simplified 1x2 configuration.   DaBigE, do you know of any literature that suggests the fencing placed down splitter islands can be effective at reducing crashes?  I’ve never seen such a study and would be interested in reading it.

There are no formal reports that I am aware of at the moment, however there are several locations that have recently attempted to restrict sight to the left on the entry with either fencing or vegetation as a crash mitigation technique. It's almost purely a psychological effect. In theory, the less the driver can see should cause the driver to reduce their speed, thus increasing the likelihood of proper yield on entry behavior. Put another way, unless you're actively being pursued by the cops, how many of you would come barreling down a narrow, building-lined alley at 30 mph when approaching a crossroad?

Unfortunately, the after crash data is not available just yet, but rumors are that it has made a positive difference. With many of the locations, this is the only treatment that has been done, so it should better prove the effectiveness of restricting entering sight distance.

In the case of locations where multiple mitigation techniques have been introduced at the same time, and if the crashes are reported/coded properly, you should be able to get an idea which technique has had an effect. Reducing the number of circulating lanes generally results in less exit/entering crossing crashes. But again, you're at the mercy of the accuracy of the officer reporting the crash. After having reviewed hundreds of crash reports (both roundabout and non-roundabout-related) and having watched reports be actively completed in several ride-alongs, my faith isn't exactly high, especially with municipal officers.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on September 29, 2016, 03:20:20 PM

On September 21st Ventura County firefighter Ryan Osler died in a rollover crash at the Highway 246 roundabout east of Lompoc.  He was on his way to fight the Canyon fire at Vandenberg Air Force Base.   Are you going to take the opportunity to call Ryan an “idiot” ?


Why would I call the passenger an idiot?  That makes no sense at all.   The driver is a separate question.

And I wouldn't come to any conclusions without knowing the full facts of the case.   I've never said that I don't value lives lost -- I've said that people have to be responsible for their own actions.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 29, 2016, 06:47:40 PM
^^^
Now you are only questioning whether the driver of the water tender truck, who was also injured, was an idiot.  That’s a step up from disparaging a dead firefighter.  Before the 246 roundabout was built there was a lot of opposition from Buellton City Council and the Santa Barbara County Supervisor Joni Gray.  Say what you want about before/after public perception about roundabouts, but building a roundabout on a 55 mph road in a valley next to the Pacific Ocean prone to morning fog may not be the best spot.

Quote
Buellton City Council members have joined their counterparts in Lompoc and Santa Barbara County Supervisor Joni Gray in opposing a Caltrans plan to install a roundabout at West Highway 246 and Purisima Road.

A unanimous council agreed Thursday to send a letter to the Sacramento-based state agency in favor of what Lompoc Mayor John Linn has proposed and called a cheaper and safer alternative.

In his presentation Thursday to the Buellton council, Linn said Caltrans’ plan would cost about $2.5 million to build a single-lane roundabout to improve circulation at the T intersection of Highway 246 near La Purisima Mission.

Linn, who has publicly stated his objections to the Caltrans traffic engineers’ plan, has proposed that rerouting the right-turn lane from Highway 246 to Purisima Road would be much less expensive (about $250,000) and safer than the traffic circle that he said would slow traffic to between 15 and 17 mph in an area posted as 55 mph.

Over the past few years, Caltrans, the lead agency on the project, has been planning to modify the intersection, based on the rate of accidents there, which was found to be four times the national average.

According to studies cited by Caltrans, roundabouts prove to be cheaper and safer options for intersections, even in rural areas, than signal lights.

In December 2010, the Lompoc City Council voted 3-2 to send a letter to Caltrans telling the agency to drop its  traffic circle plans.

After the 4-0 vote Thursday in Buellton, with Councilman John Connolly absent, Linn thanked the council for their support and the letter to be sent to Caltrans.

“We’ll see if it does some good,”  he said.

Councilwoman Judith Dale described Caltrans’ plan as “ludicrous”  based on Linn’s presentation.

Mayor Pro Tem Holly Sierra, who represents the city at the Santa Barbara County Association of Governments, where the Caltrans plan has been discussed, said the Buellton California Highway Patrol office opposes the roundabout plan, instead wanting to block Purisima Road and sending drivers to nearby Mission Gate Road.

Councilman Dave King said it appears Caltrans is in a hurry to spend the money for the project.

“It almost seems like Caltrans wants to waste $2.5 million before they lose it,”  he said.

.http://santamariatimes.com/news/local/govt-and-politics/city-joins-opposition-to-hwy-roundabout/article_b7808306-7df2-11e0-8f55-001cc4c03286.html

The fact is there has been a fatal crash at the roundabout within 4 years of being built.  Maybe there would have been a fatal crash if the intersection was a traffic signal.  Who knows.  But Caltran assured the local leaders who opposed the roundabout that it would be safer.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 30, 2016, 08:57:33 AM
Can we at least wait for the full crash report to be released before making judgement? It was foggy and someone had a fatal crash. It doesn't have to be a roundabout for such an occurrence to happen. We don't know if there were mechanical issues with the vehicle, electrical malfunctions, etc. Had it not been a roundabout, we may be talking more fatalities, because the likelihood of a high-speed t-bone collision are that much greater with other intersection types. No intersection control is fog-proof or human-proof.

Further, just because there's opposition, doesn't mean those opposing the idea are correct. Google Glens Falls, NY roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 30, 2016, 09:24:10 AM
Here’s another article involving the Lompoc roundabout.  Mayor Linn was completely opposed to the roundabout but Caltran got their way.  The article also indicates that before the roundabout there were no fatal crashes at the intersection dating back to 1998.  Many of the comments involve approaching the roundabout at night and how dangerous it feels.. it almost “sneaks up”  on you.

http://lompocrecord.com/news/local/round-n-round-about-the-roundabout/article_a83f1bde-cfcf-11e1-90d3-0019bb2963f4.html

Quote
Lefty Jul 17, 2012 8:36am - I have to agree with Mayor Linn on this one. What an absolute waste. ZERO fatalities there? Yet they build a $2.5 million interchange that causes more trouble than it is worth? Someone needed a project to work on while they golfed at La Purisima.

So You Say Jul 17, 2012 11:51am - I am used to roundabouts but this one is an accident waiting to happen.. your forced to slow down to an almost stop in order to round about it successfully...anyone who is not aware its there is going to skid or go over it... everytime I use it I feel like its such a tight squeeze....and feel fortunate when I made it through safely....this is dumb.. really dumb.

Sam C Jul 17, 2012 12:36pm - I know of two crashes happening here already. This is a very dangerous roundabout, and I agree with So You Say on slowing down there. Especially at night, it sneaks up on you. To go from 55 to 25 in just a couple seconds is obviously very dangerous. There could have plenty of other solutions to the high speeds on that road, but this seems like the biggest waste of money.

AF Squaw Jul 17, 2012 1:13pm - We moved away about 6 six years ago and we were back visiting our family and we drove in at 11pm and yes, we almost had an accident because we were not prepared to stop that fast. Over the next few days we used the round about and the more we used it the more I thought "This is the biggest waste of California dollars". Money California does not have!

BeanieNCecil Jul 17, 2012 5:29pm - We came through there yesterday and saw two cars come together and a third car- a truck- almost smash into the first two who had stopped - When you have to drive through this thing, you notice that half the people are reading the signs and trying to figure out what happened to the road instead of watching the road. Very treacherous at night. We got hit in the rear end by some little old ladies from Solvang who were completely confused by the roundabout...John Linn is right-but of course, this is California-so common sense counts for nothing.

Of course you also had ScottRAB, a total roundabout shill, regurgitating FHWA safety statistics. 

Quote
ScottRAB Jul 18, 2012 11:13am - Increase the size and you increase the speed of traffic going around and what those entering have to drive. This would make the driver interactions unsafe and result in injury crashes. This is known because when the US first began building circular intersections they were designed to freeway standards. They still exist on the east coast and are properly named rotaries.  Modern roundabouts are the safest form of intersection in the world. Search IIHS for FAQs and safety facts.  If you want to see the difference between a traffic circle, a rotary (UK roundabout) and a modern roundabout, search www.k-state.edu to see pictures. The FHWA has a video about modern roundabouts that is mostly accurate.  IMO, If you can't handle slowing down to go around a modern roundabout, maybe you're part of the problem.

ScottRAB disregards the experiences of the local community and automatically assumes the Lompoc roundabout is safer because the FHWA says so.  You got to look at roundabouts on a case by case basis but ScottRAB is too biased to do that.  I've stated several times that single lane roundabouts for the most part have good safety records... but that doesn't mean every single-lane roundabout is going to have a good safety record.  ScottRAB seems totally biased and will support every and all roundabouts ever constructed, regardless of the actual crash data or local experiences. 


Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 30, 2016, 11:19:31 AM
Had it not been a roundabout, we may be talking more fatalities, because the likelihood of a high-speed t-bone collision are that much greater with other intersection types. No intersection control is fog-proof or human-proof.

How is a driver blowing through a roundabout any safer than a driver blowing through a red light?  Aren’t other drivers at risk in both scenarios?  In the case of the fatal firefighter crash in Lompoc we know that the firetruck took the roundabout too fast (regardless of the reason why).  It’s almost a certainty that a driver is putting their life in danger when they blow through a roundabout at high speed because they can hit a curb causing their vehicle to flip over, catch on fire, etc. etc.  A driver who blows through a red light is really only putting their life in danger when another vehicle is present in the intersection.  Drivers do blow through roundabouts/circles on occasion.








Title: Re: Crash prone 'modern roundabouts'
Post by: US 81 on September 30, 2016, 11:55:46 AM
...
How is a driver blowing through a roundabout any safer than a driver blowing through a red light?  Aren’t other drivers at risk in both scenarios?  In the case of the fatal firefighter crash in Lompoc we know that the firetruck took the roundabout too fast (regardless of the reason why).  It’s almost a certainty that a driver is putting their life in danger when they blow through a roundabout at high speed because they can hit a curb causing their vehicle to flip over, catch on fire, etc. etc.  A driver who blows through a red light is really only putting their life in danger when another vehicle is present in the intersection.  Drivers do blow through roundabouts/circles on occasion.
...

We're talking totals here. It's not the driver blowing through the intersection, it's the other vehicles which may be struck by that driver.  T-bone collisions have the highest mortality/morbidity for the occupants of the car being struck. The striking car hits "head-on" and its occupants are relatively protected. The goal is lowering total mortality and morbidity, not just protecting the life and health of the careening driver.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 30, 2016, 12:47:46 PM
We're talking totals here.

If we are keeping track of totals, there were zero fatal crashes before the Lompoc intersection was a roundabout (dating back to 1998) and 1 fatal crash since it was converted to a roundabout.

The roundabout is in the lead, 1 death to zero.

Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 30, 2016, 01:58:30 PM
Had it not been a roundabout, we may be talking more fatalities, because the likelihood of a high-speed t-bone collision are that much greater with other intersection types. No intersection control is fog-proof or human-proof.

How is a driver blowing through a roundabout any safer than a driver blowing through a red light?  Aren’t other drivers at risk in both scenarios?

Where did I (or anyone else, for that matter), ever say there was zero risk? NO INTERSECTION CONTROL IS IMMUNE FROM THE POSSIBILITY OF CRASHES AND/OR FATALITIES. However, even your statistics prove that the LIKELIHOOD of a fatality is FAR LESS in a roundabout, provided people stay between the curbs.

It’s almost a certainty that a driver is putting their life in danger when they blow through a roundabout at high speed because they can hit a curb causing their vehicle to flip over, catch on fire, etc. etc.

That risk is present wherever curb is present, and that's not just limited to roundabouts. Drivers still have the legal obligation to keep their vehicle on the roadway, just as they are similarly obligated to reduce their speed in less than optimal driving conditions (fog, rain, snow, etc., etc., etc.). Those operating tanker trucks need to be especially aware of this, as their loads make their vehicles even more prone to tipping. A ramp in a cloverleaf interchange near where I work had 3 trucks tip over within a couple months of each other. The ramp is post with an advisory speed of 40. Each driver was cited for excessive speed. The Lompoc roundabout had more signs than required by the MUTCD, including a 15 mph advisory speed, and also a flashing beacon to aid in visibility. Since you appear to blame the roundabout in the case of the Lompoc crash, do you blame the interchange ramp in my example? Where does the line end for responsible driving?



Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 30, 2016, 05:21:08 PM
Where did I (or anyone else, for that matter), ever say there was zero risk? NO INTERSECTION CONTROL IS IMMUNE FROM THE POSSIBILITY OF CRASHES AND/OR FATALITIES. However, even your statistics prove that the LIKELIHOOD of a fatality is FAR LESS in a roundabout, provided people stay between the curbs.

Would be interesting to see a larger statistics set. Since fatal accidents are not very common, they need to be analyzed on large datasets. Each fatal accident would be a one-off, and you need a big picture to look at.
Anecdotally, roundabout I endure 10+ times a week had 0 fatalities in 10 years before construction per project narrative, and 1 in several - 5 I believe, years since then.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on September 30, 2016, 05:57:53 PM
^^^
Now you are only questioning whether the driver of the water tender truck, who was also injured, was an idiot. 
No I did not say that the driver was an idiot.   I said that was a separate question after you incorrectly implied that I would say the passenger was an idiot.   I even added a second line saying it was too soon to come to conclusions to make it clear that I didn't think that.   The separate question comment was simply an attempt to demonstrate your tendencies to jump to conclusions, and you didn't disappoint.





Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 30, 2016, 06:19:41 PM
No I did not say that the driver was an idiot.
I said you were questioning whether the driver was an idiot.

I said that was a separate question...
I know.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 04, 2016, 07:18:49 PM
Permanent signs are up at the 161/Riverside Drive roundabout.  There's something i don't like about this sign but i can't put my finger on it...

(https://pbs.twimg.com/media/Cti90pxWYAIXgSZ.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: 6a on October 05, 2016, 03:59:23 PM
It's not three lanes all the way around, if that's what you're referencing.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 05, 2016, 04:30:23 PM
It's not three lanes all the way around, if that's what you're referencing.

The sign correctly displays the number of lanes approaching the roundabout from the north (eastbound along route 33). Unless you're being cheeky, referring to tradephoric's dislike for triple-lane roundabouts.

Permanent signs are up at the 161/Riverside Drive roundabout.  There's something i don't like about this sign but i can't put my finger on it...

It's certainly non-standard in a number of ways. Lots of people will dislike the Clearview in the route shield (I don't hate this at all). The Helvetica looks nice, with the different weights. And the white-on-grey lane-usage sign is nice as well. So, I quite like this sign.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 05, 2016, 04:49:21 PM
Another crash happened at the Main Street & Scioto Darby Rd roundabout in Hilliard, Ohio.  From 2013-2015 there were 119 crashes at the roundabout and is one of the most dangerous intersections in the state:

http://branlawfirm.com/most-dangerous-intersections-in-ohio/
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 05, 2016, 05:11:08 PM
Another crash happened at the Main Street & Scioto Darby Rd roundabout in Hilliard, Ohio.  From 2013-2015 there were 119 crashes at the roundabout and is one of the most dangerous intersections in the state.

I'd be more persuaded by an additional collision if it was the result of genuine confusion on the part of the motorist. Drunk drivers can just as easily run into a signal pole or median.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 05, 2016, 05:50:49 PM
Another crash happened at the Main Street & Scioto Darby Rd roundabout in Hilliard, Ohio.  From 2013-2015 there were 119 crashes at the roundabout and is one of the most dangerous intersections in the state.

I'd be more persuaded by an additional collision if it was the result of genuine confusion on the part of the motorist. Drunk drivers can just as easily run into a signal pole or median.
A very significant portion of accidents is due to alcohol. That is why drunk driving is such a concern. But is you want to push down accident number - you have to take into account accidents due to driver impairment, because there will be significant number of drunks, no matter what. You can say that drunk lives matter.. If not - remember, that drunk driver can crash  into perfectly sober guy...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 05, 2016, 05:55:55 PM
Another crash happened at the Main Street & Scioto Darby Rd roundabout in Hilliard, Ohio.  From 2013-2015 there were 119 crashes at the roundabout and is one of the most dangerous intersections in the state.

I'd be more persuaded by an additional collision if it was the result of genuine confusion on the part of the motorist. Drunk drivers can just as easily run into a signal pole or median.
A very significant portion of accidents is due to alcohol. That is why drunk driving is such a concern. But is you want to push down accident number - you have to take into account accidents due to driver impairment, because there will be significant number of drunks, no matter what. You can say that drunk lives matter.. If not - remember, that drunk driver can crash  into perfectly sober guy...

I totally understand that. You can't completely eliminate drink/driving collisions (though I suspect that, like most collisions, there are fewer year-over-year as cars become more advanced, ride sharing use increases, and people become generally more responsible). But, I'd rather a central roundabout island stop a drunk driver, instead of another driver at a four-way intersection. The only loss in the collision above is the driver's car, and a bit of vegetation.
Title: Re: Crash prone 'modern roundabouts'
Post by: US 41 on October 05, 2016, 06:29:12 PM
I'm sure the answer to this is yes, but are you supposed to use a turn signal in a roundabout? No one around Terre Haute or Bloomington ever uses one.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 05, 2016, 06:38:13 PM
I totally understand that. You can't completely eliminate drink/driving collisions (though I suspect that, like most collisions, there are fewer year-over-year as cars become more advanced, ride sharing use increases, and people become generally more responsible). But, I'd rather a central roundabout island stop a drunk driver, instead of another driver at a four-way intersection. The only loss in the collision above is the driver's car, and a bit of vegetation.

The drunk driver in the video could have t-boned a circulating vehicles inside the roundabout.  You are quick to suggest that the drunk driver could hit a signal pole or median - but never another driver.  Are roundabouts so safe in your mind that they only endanger drunk drivers?   

The main argument that roundabouts are safer is based on the assumption that drivers will slow down when approaching them.  That’s not always a safe assumption.  When a driver fails to slow down when approaching a roundabout they are endangering themselves and others. 



Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 05, 2016, 07:01:01 PM
I totally understand that. You can't completely eliminate drink/driving collisions (though I suspect that, like most collisions, there are fewer year-over-year as cars become more advanced, ride sharing use increases, and people become generally more responsible). But, I'd rather a central roundabout island stop a drunk driver, instead of another driver at a four-way intersection. The only loss in the collision above is the driver's car, and a bit of vegetation.

The drunk driver in the video could have t-boned a circulating vehicles inside the roundabout.  You are quick to suggest that the drunk driver could hit a signal pole or median - but never another driver.  Are roundabouts so safe in your mind that they only endanger drunk drivers?   

The main argument that roundabouts are safer is based on the assumption that drivers will slow down when approaching them.  That’s not always a safe assumption.  When a driver fails to slow down when approaching a roundabout they are endangering themselves and others.

Okay. Are roundabouts then equally as safe as signals, when a drunk driver runs straight through one? That's not a very good defence of regular signalized intersections. You're just bringing roundabouts down to their "level".

Further, how many drunk driving collisions at roundabouts result in full-on, t-bone collisions, where the driver hops the median (instead of a failure to yield, side-swiping a car already in the roundabout)? Such is only a possibility at a roundabout, but nearly a guarantee at a signal.

Honestly, we should be celebrating the roundabout in Hilliard. It captured yet another drunk driver. Hooray..!?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 05, 2016, 07:03:36 PM
I'm sure the answer to this is yes, but are you supposed to use a turn signal in a roundabout? No one around Terre Haute or Bloomington ever uses one.

Apparently to turn left and right, but not go straight. American engineers tend to view roundabouts as traditional intersections with a central island, where there's a left, right, and straight movement. Other countries tend to see roundabouts as a single, circular road (usually with spiralling lane lines) with multiple exits. In those cases, you signal right (or left in RHD) when you go to exit.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 05, 2016, 07:17:23 PM
I totally understand that. You can't completely eliminate drink/driving collisions (though I suspect that, like most collisions, there are fewer year-over-year as cars become more advanced, ride sharing use increases, and people become generally more responsible). But, I'd rather a central roundabout island stop a drunk driver, instead of another driver at a four-way intersection. The only loss in the collision above is the driver's car, and a bit of vegetation.

The drunk driver in the video could have t-boned a circulating vehicles inside the roundabout.  You are quick to suggest that the drunk driver could hit a signal pole or median - but never another driver.  Are roundabouts so safe in your mind that they only endanger drunk drivers?   

The main argument that roundabouts are safer is based on the assumption that drivers will slow down when approaching them.  That’s not always a safe assumption.  When a driver fails to slow down when approaching a roundabout they are endangering themselves and others.

Okay. Are roundabouts then equally as safe as signals, when a drunk driver runs straight through one? That's not a very good defence of regular signalized intersections. You're just bringing roundabouts down to their "level".

Further, how many drunk driving collisions at roundabouts result in full-on, t-bone collisions, where the driver hops the median (instead of a failure to yield, side-swiping a car already in the roundabout)? Such is only a possibility at a roundabout, but nearly a guarantee at a signal.

Honestly, we should be celebrating the roundabout in Hilliard. It captured yet another drunk driver. Hooray..!?
Then I would rather have a T-bone, so that another driver unable to look around would leave the road. And it would be even better if there are some underage passengers in a car, because.. Hmm, can you think of something yourself - I am not cynical enough today...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 05, 2016, 07:29:04 PM
I'm sure the answer to this is yes, but are you supposed to use a turn signal in a roundabout? No one around Terre Haute or Bloomington ever uses one.

Apparently to turn left and right, but not go straight. American engineers tend to view roundabouts as traditional intersections with a central island, where there's a left, right, and straight movement. Other countries tend to see roundabouts as a single, circular road (usually with spiralling lane lines) with multiple exits. In those cases, you signal right (or left in RHD) when you go to exit.

I agree with Jake on this.  Here's a direct quote from Joe Gustafson who is a roundabout expert out of Minnesota.  It was taken from the “Evaluation of Safety and Mobility of Two-Lane Roundabouts”  webinar: 

“We also would never tell a driver to use a right turn signal to exit a roundabout.  Again, that’s a through movement and we don’t want to create the impression that it’s a right turn.”
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 05, 2016, 08:09:20 PM
Then I would rather have a T-bone, so that another driver unable to look around would leave the road.

Here's my theory:

At a traditional signal, the driver either misses you, or t-bones you. There's no "angle" crashes. At roundabouts however, assuming the drunk driver might follow the channelisation of the lane, but does not properly yield, there can be more of an angle crash. Or, they can drive straight over the channelising island, and t-bone you, just like at a signal. Or, they might miss you entirely.

Thusly, there's less of a chance of a t-bone collision at a roundabout, because it's one of three options, instead of two. A study would need to be done as to which type of crash is more common at roundabouts, however.

And it would be even better if there are some underage passengers in a car, because.. Hmm, can you think of something yourself - I am not cynical enough today...

(http://i.imgur.com/zl8Be3w.gif)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 05, 2016, 08:42:22 PM
Then I would rather have a T-bone, so that another driver unable to look around would leave the road.

Here's my theory:

At a traditional signal, the driver either misses you, or t-bones you. There's no "angle" crashes. At roundabouts however, assuming the drunk driver might follow the channelisation of the lane, but does not properly yield, there can be more of an angle crash. Or, they can drive straight over the channelising island, and t-bone you, just like at a signal. Or, they might miss you entirely.

Thusly, there's less of a chance of a t-bone collision at a roundabout, because it's one of three options, instead of two. A study would need to be done as to which type of crash is more common at roundabouts, however.

There is also a chance that I am turning left - and here comes angle collision. Also, if I see poorly controlled car in my  rear view mirror, I have more room to move out of impact on a regular intersection.

As for study.. If this wasn't published 5 years ago, it only means that a few (thousands) people in FHWA   DOTs  etc get their paychecks for not doing their jobs.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 05, 2016, 09:03:01 PM
There is also a chance that I am turning left - and here comes angle collision.

Why would you turn left into someone?

Also, if I see poorly controlled car in my  rear view mirror, I have more room to move out of impact on a regular intersection.

I don't think there's any reasonable difference between roundabouts and signals in this regard. You're pretty much just nitpicking here.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on October 05, 2016, 09:05:00 PM
...if I see poorly controlled car in my  rear view mirror, I have more room to move out of impact on a regular intersection.

Ah, yes, the "I know how I'm going to react" statement.

Good luck with that.  Seriously...if you're turning left watching for a gap in front of you, are you really looking in your rearview mirror?  Let me answer that for you: "No".
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 05, 2016, 09:22:21 PM
There is also a chance that I am turning left - and here comes angle collision.

Why would you turn left into someone?

Also, if I see poorly controlled car in my  rear view mirror, I have more room to move out of impact on a regular intersection.

I don't think there's any reasonable difference between roundabouts and signals in this regard. You're pretty much just nitpicking here.
To make it simple: collision at an angle would occur on a regular intersection in case both vehicles aim to the same exit. I am turning left north, you also head straight north, for example.

...if I see poorly controlled car in my  rear view mirror, I have more room to move out of impact on a regular intersection.

Ah, yes, the "I know how I'm going to react" statement.

Good luck with that.  Seriously...if you're turning left watching for a gap in front of you, are you really looking in your rearview mirror?  Let me answer that for you: "No".

Of course nobody knows how they would react until they read police report on the accident.. Point rather is that you have a bit more freedom to avoid hazard in a regular intersection as opposed to curbs bth inside and outside the roundabout. It may only make things worse, after all.
But - and feel free to disagree - I would love to see statistics on a large dataset - probably there are thousands roundabouts which exist for 5+ years. I want that data published and organized by traffic volumes, number of lanes etc.
I would say that is something FHWA must do at some point, better sooner than later. And that should be fairly doable for them as well.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on October 05, 2016, 09:50:30 PM
Having personally experienced this situation just a few weeks ago, I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on October 05, 2016, 09:55:40 PM
There is also a chance that I am turning left - and here comes angle collision.

Why would you turn left into someone?

Also, if I see poorly controlled car in my  rear view mirror, I have more room to move out of impact on a regular intersection.

I don't think there's any reasonable difference between roundabouts and signals in this regard. You're pretty much just nitpicking here.
To make it simple: collision at an angle would occur on a regular intersection in case both vehicles aim to the same exit. I am turning left north, you also head straight north, for example.

...if I see poorly controlled car in my  rear view mirror, I have more room to move out of impact on a regular intersection.

Ah, yes, the "I know how I'm going to react" statement.

Good luck with that.  Seriously...if you're turning left watching for a gap in front of you, are you really looking in your rearview mirror?  Let me answer that for you: "No".

Of course nobody knows how they would react until they read police report on the accident.. Point rather is that you have a bit more freedom to avoid hazard in a regular intersection as opposed to curbs bth inside and outside the roundabout. It may only make things worse, after all.
But - and feel free to disagree - I would love to see statistics on a large dataset - probably there are thousands roundabouts which exist for 5+ years. I want that data published and organized by traffic volumes, number of lanes etc.
I would say that is something FHWA must do at some point, better sooner than later. And that should be fairly doable for them as well.

Statistics are all based on samples.  You don't need to get info from everything.  Even getting polling from voters only require a few thousand responses to gage the tens or hundreds of millions that'll be voting.  Sure, there's going to be a poll or two that turns out to be incorrect (and you'll hear about it forever from the candidate that proved it wrong), but by in large, those small samples will be on target.

Thus, you don't need data on a large subset...because what you're really asking for is data on the entire population of roundabouts.  And like others, you'll nitpick to extract the data you want.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 06, 2016, 07:22:09 AM
Statistics are all based on samples.  You don't need to get info from everything.  Even getting polling from voters only require a few thousand responses to gage the tens or hundreds of millions that'll be voting.  Sure, there's going to be a poll or two that turns out to be incorrect (and you'll hear about it forever from the candidate that proved it wrong), but by in large, those small samples will be on target.

Thus, you don't need data on a large subset...because what you're really asking for is data on the entire population of roundabouts.  And like others, you'll nitpick to extract the data you want.
statistics has a error margin associated with it. For such low-count event as fatal accident on roundabout, error margin will be huge.
Very roughly speaking, to achieve 5% error margin  you need statistics of sqrt(n)/n=0.05 or n=400 fatal accidents on comparable roundabouts to make a conclusion. If you separate things in 4 groups - say 1x1, 1x2,2x2, more than 2x2 lanes - with 400-500 fatal events in each group -   I suspect you need all historical data to make a somewhat valid conclusion, and even then I am not sure if there is enough events overall.
And pointing out single events on individual intersection - or lack thereof - is only good for a single data record
Title: Re: Crash prone 'modern roundabouts'
Post by: 6a on October 06, 2016, 09:36:14 AM
It's not three lanes all the way around, if that's what you're referencing.

The sign correctly displays the number of lanes approaching the roundabout from the north (eastbound along route 33). Unless you're being cheeky, referring to tradephoric's dislike for triple-lane roundabouts.
No, I was being serious. I wasn't sure what he was referring to.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on October 07, 2016, 12:49:47 PM
The latest crash numbers are in for Madison, WI.

Intersection -- 2015 (2014), change
2014 Source (http://www.cityofmadison.com/trafficEngineering/documents/2014CrashReport.pdf)
2015 Source (http://www.cityofmadison.com/trafficEngineering/documents/Current_CrashReport.pdf)

What I don't have at my disposal are the volumes. It would be interesting to see how these intersections are performing as compared to how many crashes would be expected vs. actual.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 07, 2016, 01:56:27 PM
The latest crash numbers are in for Madison, WI.

Intersection -- 2015 (2014), change
  • Mineral Point @ Pleasant View -- 35 (34), +1
  • Lien Rd @ Thompson Rd -- 20 (16), +4
  • CTH M @ Valley View Rd -- 16 (18), -2
  • Commercial Ave @ Thompson Rd -- 6 (8), -2
  • Verona Rd Frontage -- 3 (N/A)
  • Eastpark Blvd @ Hanson Rd -- 0 (0), 0
  • Thompson Rd @ STH 30 -- 0 (2), -2
  • Fatalities -- 0 (0), 0
  • Injuries -- 12 (12), 0
2014 Source (http://www.cityofmadison.com/trafficEngineering/documents/2014CrashReport.pdf)
2015 Source (http://www.cityofmadison.com/trafficEngineering/documents/Current_CrashReport.pdf)

What I don't have at my disposal are the volumes. It would be interesting to see how these intersections are performing as compared to how many crashes would be expected vs. actual.

Great stuff DaBigE.  As you mentioned it doesn't include detailed intersection traffic volumes.  But i did find this link which gives link volumes for all the major roads in Madison.  For example, here are the link volumes near Washington Avenue and Stoughton Road (the signalized intersection with the most number of crashes cited in the report).

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Madisoncounts_zpsa2uujggm.png)
http://cityofmadison.maps.arcgis.com/apps/webappviewer/index.html?id=8c2d43c18d8542c7bdf8a93a11d7e545

Based on these link volumes, can we get a ballpark estimate of the intersection count?  Once we agree on the methodology for estimating the intersection counts we can do some more meaningful analysis.



Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 07, 2016, 03:18:15 PM
I estimated the intersection volume at the Washington Ave & Stroughton Road intersection to be the following:

(47200 + 32700 + 56850 + 29800) / 2 =  83275

I used the same methodology to estimate the traffic volumes for the top 5 intersections in Madison with the highest total crashes in 2015 (looking at just signals and roundabouts).  The 2x2 roundabouts in Madison had exceedingly high crash rates when compared to the signalized intersections.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Madisondata_zps9mztmgvy.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 12, 2016, 04:00:24 PM
There have now been 36 crashes in the first 56 days of operation at the 161/Riverside Drive roundabout in Dublin.  Before the roundabout the intersection only averaged 12 crashes per year.

http://www.thisweeknews.com/content/stories/dublin/news/2016/10/11/state-route-161-riverside-drive-roundabout-growing-supporters-opponents.html

I alluded that this Dublin roundabout would see a lot of crashes.

I don't think anyone ever argued that roundabouts reduce collisions overall. What they argued was that, by reducing conflict points and angle of incidence (particularly head-on and T-bone collisions), they reduce the severity of the collisions that do occur, particularly compared to all-way stop and signalized intersections.

That's exactly what's being argued though.  Listen to what Jeannie Willis has to say about the expected safety benefits of a 3-lane roundabout currently under construction in Dublin, Ohio (6A touched on this roundabout previously in this thread).  What are the residents of Dublin to think if her predictions don't come to pass?  At that point, who cares right?  It will already be constructed.

Not a valid vimeo URL
Quote
“They improve safety.  We will reduce crashes. It won’t eliminate crashes.  The frequency of the crashes will be reduced and the severity will be reduced, of the crashes, meaning the number of injury related type crashes will be substantially reduced.”

-Jeannie Willis, Engineering Manager, City of Dublin


What a reduction in crashes Jeannie!  Great job on your new roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 13, 2016, 08:04:10 PM
I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.

Said the driver of the black Toyota Camry...

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/slack-for-ios-upload-1_zps6atokjqm.jpg)
http://www.ktva.com/three-vehicle-collision-closes-dowling-rd-roundabout-541/
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 13, 2016, 08:14:13 PM
I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.

Said the driver of the black Toyota Camry...

There's gonna be exceptions, trade.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 13, 2016, 08:16:10 PM
I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.

Said the driver of the black Toyota Camry...

There's gonna be exceptions, trade.
Sure, couple more crashes, a little more fatalities- but that is all in the name of safety, we have to understand and accept that!
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on October 13, 2016, 09:13:27 PM
I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.

Said the driver of the black Toyota Camry...

There's gonna be exceptions, trade.
It doesn't bother me in the least that he is able to Google up examples of exceptions.   I drive the roundabouts of Carmel and neighboring cities every single day, I've yet to see the mass carnage in the roundabouts that he predicts.   I'll keep enjoying my vastly improved travel experience and he can post as many exceptions as it takes to make him happy.     :poke:
Title: Re: Crash prone 'modern roundabouts'
Post by: DAL764 on October 16, 2016, 06:49:30 AM
I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.

Said the driver of the black Toyota Camry...

There's gonna be exceptions, trade.
It doesn't bother me in the least that he is able to Google up examples of exceptions.   I drive the roundabouts of Carmel and neighboring cities every single day, I've yet to see the mass carnage in the roundabouts that he predicts.   I'll keep enjoying my vastly improved travel experience and he can post as many exceptions as it takes to make him happy.     :poke:
Clearly you are just living on borrowed time and at some point you, too, will be killed in a massive 50-car roundabout crash that will trigger an explosion so large that will just turn the entirety of Carmel into a massive roundabout with a 3-mile diameter.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on October 16, 2016, 02:49:29 PM
I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.

Said the driver of the black Toyota Camry...

There's gonna be exceptions, trade.
It doesn't bother me in the least that he is able to Google up examples of exceptions.   I drive the roundabouts of Carmel and neighboring cities every single day, I've yet to see the mass carnage in the roundabouts that he predicts.   I'll keep enjoying my vastly improved travel experience and he can post as many exceptions as it takes to make him happy.     :poke:
Clearly you are just living on borrowed time and at some point you, too, will be killed in a massive 50-car roundabout crash that will trigger an explosion so large that will just turn the entirety of Carmel into a massive roundabout with a 3-mile diameter.
Congratulations, you just won the Internet for the Day.
Title: Re: Crash prone 'modern roundabouts'
Post by: cl94 on October 16, 2016, 02:54:20 PM
I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.

Said the driver of the black Toyota Camry...

There's gonna be exceptions, trade.
It doesn't bother me in the least that he is able to Google up examples of exceptions.   I drive the roundabouts of Carmel and neighboring cities every single day, I've yet to see the mass carnage in the roundabouts that he predicts.   I'll keep enjoying my vastly improved travel experience and he can post as many exceptions as it takes to make him happy.     :poke:
Clearly you are just living on borrowed time and at some point you, too, will be killed in a massive 50-car roundabout crash that will trigger an explosion so large that will just turn the entirety of Carmel into a massive roundabout with a 3-mile diameter.
Congratulations, you just won the Internet for the Day.
Except such a thing already exists in Malaysia (https://www.google.com/maps/@2.9425338,101.699587,1297m/data=!3m1!1e3?hl=en).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 16, 2016, 06:49:10 PM
Isn't it convenient that circulating vehicles disappear from the roundabout whenever a drunk driver blows through it.  To suggest that an innocent driver could get t-boned inside a roundabout is pure blasphemy to roundabout proponents:

I don't think it is poorly designed, and it improves Maryland traffic safety by "intercepting" some of those impaired motorists before they crash into something else, or a pedestrian or bicyclist.

Roundabouts (properly designed) vs 4-way intersection aren't going to have head-on or t-bone collisions.

If you drive like an idiot you live (or die) with the consequences.  These are the same people that would have blown the stop sign and taken out another car when it was a stop controlled intersection -- I'm much happier with them being stopped by an inanimate object rather than another vehicle.

You never know...there could've been someone traveling on the other side of the roundabout, and the boulder saved the idiot driver from plowing thru the median into their car, killing them instead.

Had it not been a roundabout, we may be talking more fatalities, because the likelihood of a high-speed t-bone collision are that much greater with other intersection types. No intersection control is fog-proof or human-proof.

But, I'd rather a central roundabout island stop a drunk driver, instead of another driver at a four-way intersection. The only loss in the collision above is the driver's car, and a bit of vegetation.
Title: Re: Crash prone 'modern roundabouts'
Post by: cl94 on October 16, 2016, 06:53:03 PM
I think it's about time we get a lock on this topic. It has devolved into a flame war.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 16, 2016, 07:08:30 PM
Isn't it convenient that circulating vehicles disappear from the roundabout whenever a drunk driver blows through it.  To suggest that an innocent driver could get t-boned inside a roundabout is pure blasphemy to roundabout proponents:

But are the chances of a T-bone at a roundabout the same as a traditional intersection? No one is trying to say that t-bone collisions disappear with roundabouts (if they are, they're certainly mistaken).
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 16, 2016, 07:10:52 PM
I think it's about time we get a lock on this topic. It has devolved into a flame war.

It's staying relatively civil. It's had its ups and downs but no one's getting hurt.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on October 16, 2016, 08:33:21 PM
Isn't it convenient that circulating vehicles disappear from the roundabout whenever a drunk driver blows through it.  To suggest that an innocent driver could get t-boned inside a roundabout is pure blasphemy to roundabout proponents:
...
Had it not been a roundabout, we may be talking more fatalities, because the likelihood of a high-speed t-bone collision are that much greater with other intersection types. No intersection control is fog-proof or human-proof.
...

IF you insist on throwing labels around, I am NOT a roundabout proponent in the definition you're trying to insinuate; more accurately, I am a traffic engineering REALIST. Again, stop cherry-picking/twisting my words to fit your agenda.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on October 16, 2016, 08:40:49 PM
I think it's about time we get a lock on this topic. It has devolved into a flame war.

It's staying relatively civil. It's had its ups and downs but no one's getting hurt.

While that may be true, the information well is clearly running dry...the post content is once again are taking a circular nature.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 16, 2016, 09:58:07 PM
I think it's about time we get a lock on this topic. It has devolved into a flame war.

It's staying relatively civil. It's had its ups and downs but no one's getting hurt.

While that may be true, the information well is clearly running dry...the post content is once again are taking a circular nature.

Very true. It really has devolved into a roundabout discussion.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 16, 2016, 11:10:13 PM
Had it not been a roundabout, we may be talking more fatalities

It's not a stretch to say someone is a roundabout proponent when they insinuate that a fatal roundabout crash that occurred may have been deadlier if it was another intersection type.  If you take offense to that, sobeit.  The family of Ryan Osler may take offense to certain insinuations too. 

While that may be true, the information well is clearly running dry...the post content is once again are taking a circular nature.

DaBigE, just a week ago you posted the latest crash data for Madison, Wisconsin.  It was used to determine the most up-to-date crash rates for multiple roundabouts in that city (and the finding was they had high crash rates).  That's new and pertinent information for a thread titled "crash prone modern roundabouts".
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on October 16, 2016, 11:45:05 PM
Had it not been a roundabout, we may be talking more fatalities

It's not a stretch to say someone is a roundabout proponent when they insinuate that a fatal roundabout crash that occurred may have been deadlier if it was another intersection type.  If you take offense to that, sobeit.  The family of Ryan Osler may take offense to certain insinuations too.

Making a generalization on a couple data points is a stretch...try publishing a scientific paper on that logic. It's called having an open and scientific mind...looking at all the possibilities and points of view rather than throwing the baby out with the bath water. So, yes, I do take offense to your generalization, just as I would if someone lumped me into one political orientation based on one or two talking points, and just as you appear to when others perpetuate you have an agenda to prove.   

While that may be true, the information well is clearly running dry...the post content is once again are taking a circular nature.

DaBigE, just a week ago you posted the latest crash data for Madison, Wisconsin.  It was used to determine the most up-to-date crash rates for multiple roundabouts in that city (and the finding was they had high crash rates).  That's new and pertinent information for a thread titled "crash prone modern roundabouts".

And what did that information yield? Your same conclusions and discussions made numerous thread pages ago. Also note that data was provided without opinion or much commentary. I could have highlighted the roundabouts that had a decrease in crashes (as a true proponent would do).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 17, 2016, 01:00:54 AM
DaBigE, you have agreed with me in the past that agencies should no longer be promoting the 2000 IIHS study:
 
For similar reasons, I also disagree with the IIHS study being promoted any further because, as tradephoric also pointed out, it was done on fewer roundabouts and over 15 years ago. A lot has changed within the past 5 years, let alone 15. Similarly, as I've said earlier, many of us (professional colleagues included), have fundamental issues with the studies WisDOT has carried out as well.

Now watch Myth #2 in this video (released in Oct. 2015).  The safety statistics sound oddly familiar.  The t-bone picture at the signalized intersection juxtaposed with the glancing blow of the roundabout was a nice touch for this propaganda piece (I feel justified saying it’s a propaganda piece because they are citing safety statistics from the previous century).   Did a 2x3 configuration roundabout even exist in America in the late 90s?  I know they do today.   But according to you I'm the one with the agenda.

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 17, 2016, 01:20:37 AM
Did a 2x3 configuration roundabout even exist in America in the late 90s?  I know they do today.

I think one of the first roundabouts in the US was 3x3 (Summerlin, NV), built in the mid 90s:

https://historicaerials.com/?layer=1999&zoom=18&lat=36.17836265443195&lon=-115.31760692596436
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on October 17, 2016, 11:04:08 AM
Similar idea but different subject: I've heard people say that when one's using a cell phone, they are 4 times more likely to get in an accident.

I'm still waiting to hear what the probability is of getting in an accident.  And if that's not known, how do you come up with 4 times of an unknown?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 20, 2016, 12:39:27 PM
I could have highlighted the roundabouts that had a decrease in crashes (as a true proponent would do).

Some people favor insinuations over facts.  I have made this challenge before, but cite a multi-lane roundabout (2x2 or 2x3 configuration) that has a crash rate below 1.0 MEV.  A typical signalized intersection has a crash rate of 0.7 MEV so there should be plenty of examples of multi-lane roundabouts with crash rates below 1.0 MEV.  Maybe you will have better luck, but here are the multi-lane roundabouts i could find crash data for and none of them have a crash rate below 1.0 MEV . 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBcrashrate_zpsl0dosxlc.png)

The average crash rate for these multi-lane roundabouts is about 5X higher than a standard signalized intersection.  Even the best performing roundabouts have crash rates double that of a typical traffic signal.  These are very bad results.  They are so bad that many agencies have removed circulating lanes inside the roundabout to address the high crash rates (roundabouts highlighted yellow have had lanes removed).

Making a generalization on a couple data points is a stretch...try publishing a scientific paper on that logic. It's called having an open and scientific mind...

My open and scientific mind is looking at the latest and greatest crash data - not relying on some 15 year old study to determine how effective roundabouts are.  DaBigE, you should be proud that I’m continually updating the crash rates of these multi-lane roundabouts and not lamenting when new data is cited on this thread.
Title: Re: Crash prone 'modern roundabouts'
Post by: cl94 on October 20, 2016, 01:57:15 PM
Of course, accident statistics aren't necessarily comparable across intersections and, more importantly, population changes need to be accounted for.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 20, 2016, 02:22:30 PM
Of course, accident statistics aren't necessarily comparable across intersections and, more importantly, population changes need to be accounted for.
Oh, come on, you are a transportation engineer! Shame on you for saying something like that.
Just praise the Holy Roundabout! Otherwise you wouldn't find a job, you know..
Title: Re: Crash prone 'modern roundabouts'
Post by: cl94 on October 20, 2016, 02:44:00 PM
Of course, accident statistics aren't necessarily comparable across intersections and, more importantly, population changes need to be accounted for.
Oh, come on, you are a transportation engineer! Shame on you for saying something like that.
Just praise the Holy Roundabout! Otherwise you wouldn't find a job, you know..

I'm on the research side. I don't give a damn about the propaganda, I just want to know how stuff truly compares.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on October 20, 2016, 03:11:58 PM
Making a generalization on a couple data points is a stretch...try publishing a scientific paper on that logic. It's called having an open and scientific mind...

My open and scientific mind is looking at the latest and greatest crash data - not relying on some 15 year old study to determine how effective roundabouts are.  DaBigE, you should be proud that I’m continually updating the crash rates of these multi-lane roundabouts and not lamenting when new data is cited on this thread.

The only thing anyone is lamenting is the lack of new discussion. It's the same song and dance each time... crashes are not going down, crashes are going up, yada, yada, yada. Great, there's new numbers...what myself and I can only assume others are waiting for is new action to be taken to correct the number of crashes. I'm guessing nearly no one that is a member of this forum has any power to change how policy and research are being done, so posting new data is by and large a waste of energy and only serving to decrease the number of interested readers.

And until new research or design action comes out, I'm not going to waste any more energy responding to cherry-picked quotes in this thread.

Are roundabouts perfect? No. Are they a silver-bullet solution? Not even close. What they are is another tool in the toolbox -- a tool which is still working thru some R&D revisions.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 20, 2016, 04:45:48 PM
Making a generalization on a couple data points is a stretch...try publishing a scientific paper on that logic. It's called having an open and scientific mind...

My open and scientific mind is looking at the latest and greatest crash data - not relying on some 15 year old study to determine how effective roundabouts are.  DaBigE, you should be proud that I’m continually updating the crash rates of these multi-lane roundabouts and not lamenting when new data is cited on this thread.

The only thing anyone is lamenting is the lack of new discussion. It's the same song and dance each time... crashes are not going down, crashes are going up, yada, yada, yada. Great, there's new numbers...what myself and I can only assume others are waiting for is new action to be taken to correct the number of crashes. I'm guessing nearly no one that is a member of this forum has any power to change how policy and research are being done, so posting new data is by and large a waste of energy and only serving to decrease the number of interested readers.

And until new research or design action comes out, I'm not going to waste any more energy responding to cherry-picked quotes in this thread.

Are roundabouts perfect? No. Are they a silver-bullet solution? Not even close. What they are is another tool in the toolbox -- a tool which is still working thru some R&D revisions.

I, for one, absolutely pissed off with the fact that roundabouts are sold as silver bullets. I am not sure what is needed to reverse the trend of Holy Roundabouts construction. 
Of course, there is not much we can do on this forum. But I don't see what can be done  in general... Seems like too much money is involved.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 20, 2016, 04:47:39 PM
Of course, accident statistics aren't necessarily comparable across intersections and, more importantly, population changes need to be accounted for.
Oh, come on, you are a transportation engineer! Shame on you for saying something like that.
Just praise the Holy Roundabout! Otherwise you wouldn't find a job, you know..

I'm on the research side. I don't give a damn about the propaganda, I just want to know how stuff truly compares.
Count me in.. and lets keep dreaming..
On research side, however,  only real papers I found are dealing with minor street joining arterial, which makes some sense.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 21, 2016, 12:56:58 PM
The only thing anyone is lamenting is the lack of new discussion. It's the same song and dance each time... crashes are not going down, crashes are going up, yada, yada, yada. Great, there's new numbers...what myself and I can only assume others are waiting for is new action to be taken to correct the number of crashes. I'm guessing nearly no one that is a member of this forum has any power to change how policy and research are being done, so posting new data is by and large a waste of energy and only serving to decrease the number of interested readers.

And until new research or design action comes out, I'm not going to waste any more energy responding to cherry-picked quotes in this thread.

You are diminishing the importance of new crash data, you accuse me of having an agenda when other agencies are citing statistics from the previous century, you ignore my request to cite a 2x2 multi-lane roundabout with a crash rate below 1.0 MEV, and you grumble that the thread is ”˜going in circles’ when I respond to your accusations.  Should I care if you leave?

It’s amazing that there isn’t a single example of a multi-lane roundabout (2x2) that has a crash rate below that of a standard signalized intersection.  Agencies can keep pushing their propaganda that these multi-lane roundabouts reduce total crashes, but it’s not true.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 21, 2016, 01:12:50 PM
It’s amazing that there isn’t a single example of a multi-lane roundabout (2x2) that has a crash rate below that of a standard signalized intersection.

...that you know of.

Your list contains dozens of multi-lane roundabouts, but according to Roundabouts USA, there were nearly five thousand roundabouts in the US by the end of last year (source (http://www.roundaboutsusa.com/history.html)). Of course most of these are single lane, but there are hundreds that aren't. And the bottom of your list, while still not below 1 MEV, gets pretty close (last I remember seeing, at least--your table isn't showing up for me anymore). The chance of there being multi-lane roundabouts with crash rates below 1 MEV is pretty likely. We just need numbers that aren't publicly available (or better yet, a comprehensive modern-day study from the FHWA).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 21, 2016, 01:20:16 PM
We just need numbers that aren't publicly available (or better yet, a comprehensive modern-day study from the FHWA).
Wow, looks like you started to change your mind! First step is always the most difficult one... And welcome to the club!
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 21, 2016, 01:24:21 PM
We just need numbers that aren't publicly available (or better yet, a comprehensive modern-day study from the FHWA).

Wow, looks like you started to change your mind! First step is always the most difficult one... And welcome to the club!

Despite what I've said in the past, I very much agree with tradephoric that the oft-cited study is simply too old to be relevant. We definitely need a new, more comprehensive study.

Where I've disagreed with him in the past is with his propensity to declare all multi-lane roundabouts to be duds, based on the data of the several dozens that he's found. I'm not saying his research isn't appreciated -- it is, and it's definitely opened some eyes. But we need to study all of the roundabouts in America before we come to a conclusion.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on October 21, 2016, 01:37:16 PM
It’s amazing that there isn’t a single example of a multi-lane roundabout (2x2) that has a crash rate below that of a standard signalized intersection.  Agencies can keep pushing their propaganda that these multi-lane roundabouts reduce total crashes, but it’s not true.

I've restrained myself from wading back into this thread, but I will agree that transportation departments shouldn't make the claim roundabouts will reduce the incidence rate of total crashes or property-damage only crashes over signalized intersections, because that's not borne out by the evidence in the general case. And I'll gladly concede that roundabouts - constructed against engineering guidance - that have fixed objects in the island should have been properly engineered.

However, I think you need to be willing to concede that roundabouts - even multilane roundabouts - do in general reduce the incidence of injury and fatality crashes, even if they don't prevent all of them (which has never been claimed by anyone, to my knowledge). In fact that's the key trade-off - with roundabouts, you get some more low-angle of incidence, lower-speed crashes in return for fewer 90-degree, high-speed crashes, which are the ones (particularly with today's safety technologies) are the most dangerous.

Does that mean I (and others) have callous disregard for the deaths and injuries that remain, as you have stated on several occasions? Of course not, and such an implication is frankly offensive. No intersection is perfect or (as DaBigE puts it) a "silver bullet," particularly when you have high traffic volumes. But unless you think that some human lives have more intrinsic value than other human lives, an option that results in fewer injuries and deaths overall is preferable to one that results in more of them, even if some deaths and injuries are going to happen either way. That doesn't bring back specific crash victims who might not have died in the counterfactual universe where there was a different intersection, but it does mean that more people didn't die in their place.

And I will say that if your beef boils down to (like kalvado's appears to boil down to) "transportation agencies are making false/exaggerated claims about total crash rates," this thread appears to have run its course and you need to address yourself elsewhere, because transportation agencies and their media representatives aren't reading random threads on Internet message boards to decide how they will communicate with the public.

But we need to study all of the roundabouts in America before we come to a conclusion.

This. Unless you're studying the entire population of interest, you're going to arrive at bad conclusions. Otherwise you end up being the guy on Twitter claiming that Trump is winning the election because he got a few million votes on a Drudge Report web poll.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on October 21, 2016, 01:58:25 PM
It’s amazing that there isn’t a single example of a multi-lane roundabout (2x2) that has a crash rate below that of a standard signalized intersection.  Agencies can keep pushing their propaganda that these multi-lane roundabouts reduce total crashes, but it’s not true.

I've restrained myself from wading back into this thread, but I will agree that transportation departments shouldn't make the claim roundabouts will reduce the incidence rate of total crashes or property-damage only crashes over signalized intersections, because that's not borne out by the evidence in the general case. And I'll gladly concede that roundabouts - constructed against engineering guidance - that have fixed objects in the island should have been properly engineered.

However, I think you need to be willing to concede that roundabouts - even multilane roundabouts - do in general reduce the incidence of injury and fatality crashes, even if they don't prevent all of them (which has never been claimed by anyone, to my knowledge). In fact that's the key trade-off - with roundabouts, you get some more low-angle of incidence, lower-speed crashes in return for fewer 90-degree, high-speed crashes, which are the ones (particularly with today's safety technologies) are the most dangerous.

Does that mean I (and others) have callous disregard for the deaths and injuries that remain, as you have stated on several occasions? Of course not, and such an implication is frankly offensive. No intersection is perfect or (as DaBigE puts it) a "silver bullet," particularly when you have high traffic volumes. But unless you think that some human lives have more intrinsic value than other human lives, an option that results in fewer injuries and deaths overall is preferable to one that results in more of them, even if some deaths and injuries are going to happen either way. That doesn't bring back specific crash victims who might not have died in the counterfactual universe where there was a different intersection, but it does mean that more people didn't die in their place.

And I will say that if your beef boils down to (like kalvado's appears to boil down to) "transportation agencies are making false/exaggerated claims about total crash rates," this thread appears to have run its course and you need to address yourself elsewhere, because transportation agencies and their media representatives aren't reading random threads on Internet message boards to decide how they will communicate with the public.

^This. The only thing missing is a mic drop.

The only thing anyone is lamenting is the lack of new discussion. It's the same song and dance each time... crashes are not going down, crashes are going up, yada, yada, yada. Great, there's new numbers...what myself and I can only assume others are waiting for is new action to be taken to correct the number of crashes. I'm guessing nearly no one that is a member of this forum has any power to change how policy and research are being done, so posting new data is by and large a waste of energy and only serving to decrease the number of interested readers.

And until new research or design action comes out, I'm not going to waste any more energy responding to cherry-picked quotes in this thread.

You are diminishing the importance of new crash data, you accuse me of having an agenda when other agencies are citing statistics from the previous century, you ignore my request to cite a 2x2 multi-lane roundabout with a crash rate below 1.0 MEV, and you grumble that the thread is ”˜going in circles’ when I respond to your accusations.  Should I care if you leave?

You do have a way with words. Replace "last century" with "20 years ago" and see if there's a change in the drama of that statement. No one is diminishing the importance of new data, far from it, actually. We're saying your point has been proven time and time again. New numbers aren't changing anything, unfortunately. That is where this thread is going in circles. Me pointing this out again is further evidence. And it's not that I give a shit whether you care or not, rather, it's my way of saying don't bother targeting me in your posts. No other data I have access to will add anything new to this discussion. You have the same access to the internet as I.

And since you like to twist and throw my words back at me, I chose to respond since for a change you didn't cherry-pick something in your post
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 21, 2016, 03:56:33 PM
And I will say that if your beef boils down to (like kalvado's appears to boil down to) "transportation agencies are making false/exaggerated claims about total crash rates," this thread appears to have run its course and you need to address yourself elsewhere, because transportation agencies and their media representatives aren't reading random threads on Internet message boards to decide how they will communicate with the public.
Well, let me expand my point a little bit.
My impression is that roundabouts are controversial enough (this thread may be the evidence) for the issues to be addressed with some more detailed analysis. And - as pretty even jakeroot has admitted - there is no such analysis available to general public. Compare that with SPUI, for example - although there is much lower number, but they seem  way less controversial for general public.
Now... why would such structures be built in large number without looking at public input? My two possible answers are indoctrination and corruption. And my bet is that its not even about transportation officials, it is about election money.
And, if you think about it, roundabouts are expensive. I've seen anything between $1.5M and $15M... 1% or even 0.1% of such contract is a sizeable chunk of money...

Yes, roundabout is definitely another tool in the box. But it takes some learning to use proper tools - and learning is something I don't see. But I see a lot of situations where tool is used in a way someone else would use sledgehammer on screws.

I am not against ALL roundabouts, I am against those built without understanding of usability ..... which seem to be most of them, unfortunately.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on October 21, 2016, 04:19:45 PM
Well, let me expand my point a little bit.
My impression is that roundabouts are controversial enough (this thread may be the evidence) for the issues to be addressed with some more detailed analysis. And - as pretty even jakeroot has admitted - there is no such analysis available to general public. Compare that with SPUI, for example - although there is much lower number, but they seem  way less controversial for general public.

But when you boil it down, a SPUI is still a traffic signal. Movements are still largely the same as a conventional cross intersection. IMO, that is why SPUIs aren't as controversial. Going right to ultimately turn left in a roundabout? That logic still blows the mind of a lot of people. It disrupts the binary thought process so many drivers are entrenched in. And we should begin to see more transparency in the decision process of intersection controls as ICE (Intersection Control Evaluation) reports become more common. Each state may have a slightly different format to them, but they're a part of public record (at least for state-run projects), so you should be able to request to see them. Wisconsin has had them for a few years, MnDOT uses a form of ICE as does Illinois (I believe they're called IDS reports), and GDOT is working on implementing them. Other states may be in various stages of use as well, but they're out of my normal work area.

...But it takes some learning to use proper tools - and learning is something I don't see. But I see a lot of situations where tool is used in a way someone else would use sledgehammer on screws.

I would agree with that on many levels...drivers, engineers, and politicians. But I do see the general opinion of roundabouts losing a bit of controversy. It used to be where you'd look at the comments section of a news story regarding a roundabout and you'd see nearly 100% of commenters against any and all roundabouts. You still see a lot of negativity, but there's also a big upswing in the number of people with positive things to say. I've witnessed similar experiences in various PIMs I've been to recently.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 21, 2016, 04:29:06 PM
You do have a way with words. Replace "last century" with "20 years ago" and see if there's a change in the drama of that statement.

Go ahead and replace “last century”  with “20 years ago” .  That’s fine.  Some members here weren’t even alive 20 years ago.  What’s dramatic is that agencies still push safety statistics from such an old study.

No one is diminishing the importance of new data, far from it, actually. We're saying your point has been proven time and time again. New numbers aren't changing anything, unfortunately. That is where this thread is going in circles.

I don’t understand what you are getting at.  Should we stop citing new crash prone modern roundabouts simply because there are already examples of crash prone modern roundabouts?  Kalvado just mentioned SPUIs... what if somebody started a thread wanting to know the location of every SPUI in America.  Should that compilation of data stop once some arbitrary number of SPUI locations is determined?  I guess compiling a database of SPUIs is less controversial than compiling a database of crash prone modern roundabouts.

I like to piecemeal posts so i can respond to individual points.  I'm not trying to cherry-pick.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 21, 2016, 04:59:39 PM
Well, let me expand my point a little bit.
My impression is that roundabouts are controversial enough (this thread may be the evidence) for the issues to be addressed with some more detailed analysis. And - as pretty even jakeroot has admitted - there is no such analysis available to general public. Compare that with SPUI, for example - although there is much lower number, but they seem  way less controversial for general public.

But when you boil it down, a SPUI is still a traffic signal. Movements are still largely the same as a conventional cross intersection. IMO, that is why SPUIs aren't as controversial. Going right to ultimately turn left in a roundabout? That logic still blows the mind of a lot of people. It disrupts the binary thought process so many drivers are entrenched in. And we should begin to see more transparency in the decision process of intersection controls as ICE (Intersection Control Evaluation) reports become more common. Each state may have a slightly different format to them, but they're a part of public record (at least for state-run projects), so you should be able to request to see them. Wisconsin has had them for a few years, MnDOT uses a form of ICE as does Illinois (I believe they're called IDS reports), and GDOT is working on implementing them. Other states may be in various stages of use as well, but they're out of my normal work area.

...But it takes some learning to use proper tools - and learning is something I don't see. But I see a lot of situations where tool is used in a way someone else would use sledgehammer on screws.

I would agree with that on many levels...drivers, engineers, and politicians. But I do see the general opinion of roundabouts losing a bit of controversy. It used to be where you'd look at the comments section of a news story regarding a roundabout and you'd see nearly 100% of commenters against any and all roundabouts. You still see a lot of negativity, but there's also a big upswing in the number of people with positive things to say. I've witnessed similar experiences in various PIMs I've been to recently.

I used SPUI as an example of novel structure which is accepted without major issue. And having oncoming traffic on your right is counter-intuitive as well for me. I still have to experience diverging diamond, so I didn't talk about that, but may be a fair comparison as well. 

Roundabout for me are not a totally new thing, not more than SPUI. More like a mandatory turn on red. If you buy that interpretion,  underlying movement - turn on red - is fairly common in US and shouldn't be an issue. Yet I see many people unhappy, but still force fed new circles. Yes, there is some degree of acceptance... But people tend to get used to many things, and that doesn't prove safety or convenience. Moreover, given significant level of opposition after so many years...
That is why I don't take DOT(using term lousily) pro-circle arguments at face value.

 
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on October 21, 2016, 06:52:21 PM
Roundabout for me are not a totally new thing, not more than SPUI. More like a mandatory turn on red. If you buy that interpretion,  underlying movement - turn on red - is fairly common in US and shouldn't be an issue. Yet I see many people unhappy, but still force fed new circles. Yes, there is some degree of acceptance... But people tend to get used to many things, and that doesn't prove safety or convenience. Moreover, given significant level of opposition after so many years...
That is why I don't take DOT(using term lousily) pro-circle arguments at face value.

I like that comparison...I think it fits the situation very well. Multilane roundabouts should, in theory be not much different than a RTOR from a dual-lane right turn approach.

One of the biggest reasons for the force-feeding of many roundabouts is to be due to federal HSIP funding structure. Many of those grants are tied specifically to the construction of roundabouts, due to the outdated IIHS information. Until a new study of similar size is done, good luck getting the feds to take off the rose-colored glasses. Unfortunately, no roundabout = no money for an improvement project, so many cash-strapped agencies will swallow the bitter roundabout pill in order to be seen as doing something to improve a safety problem.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on October 21, 2016, 07:08:27 PM
You do have a way with words. Replace "last century" with "20 years ago" and see if there's a change in the drama of that statement.

Go ahead and replace “last century”  with “20 years ago” .  That’s fine.  Some members here weren’t even alive 20 years ago.  What’s dramatic is that agencies still push safety statistics from such an old study.

Hate to break it to you, but there are other design decisions based on data that is much older. Unfortunately, many agencies don't have the money to fill all their potholes, let alone fund proper, revised safety studies.

I like to piecemeal posts so i can respond to individual points.  I'm not trying to cherry-pick.

There's obviously a lot more you don't get (or don't want to admit to doing)...you cherry-pick parts of statements, many times out of context to make it sound like we're saying something we're not.
Title: Re: Crash prone 'modern roundabouts'
Post by: cl94 on October 21, 2016, 08:00:36 PM
One of the biggest reasons for the force-feeding of many roundabouts is to be due to federal HSIP funding structure. Many of those grants are tied specifically to the construction of roundabouts, due to the outdated IIHS information. Until a new study of similar size is done, good luck getting the feds to take off the rose-colored glasses. Unfortunately, no roundabout = no money for an improvement project, so many cash-strapped agencies will swallow the bitter roundabout pill in order to be seen as doing something to improve a safety problem.

This. It all boils down to money. Sometimes, roundabouts are a good solution (such as for a moderately-trafficked 5+ point intersection or low speeds). Other times, they aren't. Being on the research side, I can tell you that transportation research funding is very limited and, honestly, there are more important things to study right now where the money would have more impact.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on October 22, 2016, 06:28:32 AM
I'd love to post collision data from the several multi-lane roundabouts in my town. But as there haven't been any collisions at the roundabouts for over 20 years, there's no data to find. ;)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 22, 2016, 10:41:54 AM
And I'm sure none of them have fixed objects in the island, all approaches have opaque fencing, all of them have exactly the same ideal traffic volumes, lines are never faded or obscured by snow......

I've really been waiting for a post from english si. His experience across the pond is strong evidence that roundabout crashes are a product of culture and education, not geometry and design.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 22, 2016, 11:51:47 AM
However, I think you need to be willing to concede that roundabouts - even multilane roundabouts - do in general reduce the incidence of injury and fatality crashes, even if they don't prevent all of them (which has never been claimed by anyone, to my knowledge). In fact that's the key trade-off - with roundabouts, you get some more low-angle of incidence, lower-speed crashes in return for fewer 90-degree, high-speed crashes, which are the ones (particularly with today's safety technologies) are the most dangerous.

A roundabout with an ADT of 50,000 experienced 10% injury crashes last year.  A signalized intersection with an ADT of 50,000 experienced 50% injury crashes last year.  Which intersection had more injury crashes last year?  We can’t answer that question without knowing the total crashes that occurred at both intersections.  You can argue that roundabouts on a percentage basis have fewer injury crashes, but it’s a misleading statistics.  Maybe the roundabout had 100 crashes (10 leading to injury) and the traffic signal only had 12 crashes (6 leading to injury).  Under that scenario the traffic signal sounds much safer, even though 50% of the crashes at the signal led to injury. 

Let’s start looking at injury crash rates, which account for total crashes, as opposed to the crash severity, which doesn’t account for total crashes.  Like I have said before, if you have a big spike in total crashes at a roundabout - which is what we are seeing at these 2x2 and 2x3 configurations - there’s no guarantee that there will be a reduction in injury crashes.


Does that mean I (and others) have callous disregard for the deaths and injuries that remain, as you have stated on several occasions? Of course not, and such an implication is frankly offensive. No intersection is perfect or (as DaBigE puts it) a "silver bullet," particularly when you have high traffic volumes. But unless you think that some human lives have more intrinsic value than other human lives, an option that results in fewer injuries and deaths overall is preferable to one that results in more of them, even if some deaths and injuries are going to happen either way. That doesn't bring back specific crash victims who might not have died in the counterfactual universe where there was a different intersection, but it does mean that more people didn't die in their place.

When someone suggests that only drunks and idiots are getting seriously injured and killed at roundabouts — which has been mentioned many times on this thread - then those comments do risk being construed as callous.  An argument made in ad nauseam is that it’s not the fault of the roundabout when these crashes occur.  That line of thinking didn’t stop engineers from replacing traffic signals with roundabouts for their supposed safety benefits.  How is it the fault of a traffic signal when a driver blows through a red light?  Maybe we should overlook red light running crashes when analyzing the safety benefits of traffic signals.  If that was the case there would be no need for roundabouts in the first place.


And I will say that if your beef boils down to (like kalvado's appears to boil down to) "transportation agencies are making false/exaggerated claims about total crash rates," this thread appears to have run its course and you need to address yourself elsewhere, because transportation agencies and their media representatives aren't reading random threads on Internet message boards to decide how they will communicate with the public.

Transportation agencies may be making false/exaggerated claims about injury and fatal crash rates as well.  When I pointed out that 3 of the last 4 fatal crashes in Carmel occurred at roundabouts, people were critical saying that there wasn’t enough data to make any meaningful determination.  Of course nobody had a problem when the IIHS study concluded that roundabouts reduce fatal crashes by 90%, even though the study only analyzed 24 roundabouts.

But we need to study all of the roundabouts in America before we come to a conclusion.

This. Unless you're studying the entire population of interest, you're going to arrive at bad conclusions. Otherwise you end up being the guy on Twitter claiming that Trump is winning the election because he got a few million votes on a Drudge Report web poll.

Here’s a population of over 5,100 modern roundabouts in America.  If you want, query out and analyze the roundabouts of interest.  It’s dangerous to mention the C-word and T-word on here, but based on your previous predictions I wouldn’t rule out either candidate.  Remember Dublin?

http://www.mediafire.com/file/e9ch50iu2afkh4x/Modern+Roundabouts+%28May-2015%29.kmz
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on October 22, 2016, 01:36:07 PM
I've really been waiting for a post from english si. His experience across the pond is strong evidence that roundabout crashes are a product of culture and education, not geometry and design.
I'd argue that the main problem with US roundabouts is culture and education, but in the UK it's geometry and design if a roundabout has lots of crashes.

In the US, when the issue seems to be design, it's actually due to education reasons - assuming that American drivers are stupid, lazy and unobservant, and therefore designing poor practice to be proscribed by road markings is a recipe for disaster.

If we educate US drivers well, design the roundabouts to match that education, and create a driving culture that's able to deal with roundabouts, and comes into contact with them regularly, then roundabouts will certainly meet the claims that Tradephoric is attacking.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on October 22, 2016, 01:42:45 PM
If we educate US drivers well, design the roundabouts to match that education, and create a driving culture that's able to deal with roundabouts, and comes into contact with them regularly, then roundabouts will certainly meet the claims that Tradephoric is attacking.

Bingo. How many drivers had roundabouts as part of their driver's ed program? Currently, only a small percentage, but thankfully it's growing [slowly] daily. Since there's no mandatory retraining, older drivers don't get the same education. PI blitzes only go so far. Arguably, driver's ed is the only time you can force someone to learn about a roundabout...after one receives their license, keeping up on laws and designs is completely voluntary. I wonder how many members of this forum have bothered to reread their agency's drivers' handbook? And if so, how long ago?
Title: Re: Crash prone 'modern roundabouts'
Post by: cl94 on October 22, 2016, 01:54:12 PM
I've been saying that people should be retested every 5-10 years for a while. Would do a lot to stop the lazy habits and force them to take a driver's ed course as part of it.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 22, 2016, 05:24:19 PM
Maybe we should overlook red light running crashes when analyzing the safety benefits of traffic signals.  If that was the case there would be no need for roundabouts in the first place.

Perhaps I'm quoting this out of context, or more likely ignoring the tongue-in-cheek you were attempting to employ. None the less, I think it betrays your true bias: roundabouts are unnecessary. You do not believe them to be 'one tool in the bag,' as we have recently taken to calling them in this thread, but rather a superfluous tool that no real craftsman would ever buy (if you'll allow me to extend the metaphor) because it's substandard, underperforming, overpriced crap. Real craftsmen buy stoplights.

While I appreciate your efforts at putting roundabouts and stoplights together on the same table when it comes to crunching the numbers, I still believe your goal to be discounting roundabouts en masse by highlighting the worst of the data at hand.

Traffic control is necessary (although quite a bit less necessary than we seem to think here in America), be it Yield signs, Stop signs, signals, roundabouts, what have you. It's necessary because intersections exist. But to say that roundabouts are only necessary if _______ is true compared to stoplights... That's bias. Turn it around and ask if it has the same ring of truth or not: Stoplights are only necessary if _______ is true compared to roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 22, 2016, 09:15:08 PM
I'd love to post collision data from the several multi-lane roundabouts in my town. But as there haven't been any collisions at the roundabouts for over 20 years, there's no data to find. ;)
Well, you may want to add traffic numbers to that statement. Maybe both drivers in your town have to share same car, hence there are no accidents?
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on October 23, 2016, 04:52:33 AM
Well, you may want to add traffic numbers to that statement. Maybe both drivers in your town have to share same car, hence there are no accidents?
Only A Roads have traffic counts, and some of these legs are measured away from the roundabout, after some side turns (which add traffic to the roundabout).
Roundabout 1 - legs of 11363, 16818, 18470, 16569. 31610
Roundabout 2 - legs of 18804, 20388, 18470, 26135. 41898
Roundabout 3 - legs of 14997, 14917, 26135. 28024
Roundabout 4 - legs of 14917, 14917, unknown. At least 14917 vehicles use the roundabout daily
Roundabout 5 - legs of 20388, 20388, unknown, unknown. There probably is a lazy bit of counting here, but at least 20388 vehicles use the roundabout daily (as one leg certainly has that figure).

A mix of traffic figures, but none are small.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on October 23, 2016, 05:15:38 AM
There's a valid statistic for measuring injury and death rates at intersections - incidence per MEV, the same rate that tradephoric has been using to measure total crash rates. You don't need total crashes to calculate deaths per MEV or injuries per MEV.

Alternatively you could use a weighting scheme, like that described here (http://safety.fhwa.dot.gov/local_rural/training/fhwasaxx1210/s5.cfm) that weights fatality crashes 12x and injury crashes 3x as "severe" as a PDO crash - of course, other weighting schemes are possible.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 23, 2016, 08:24:02 PM
While I appreciate your efforts at putting roundabouts and stoplights together on the same table when it comes to crunching the numbers, I still believe your goal to be discounting roundabouts en masse by highlighting the worst of the data at hand.

Here's a timeline of how roundabouts have evolved in America...

1990-1999:  Roundabouts introduced to America
The first modern roundabout in America was constructed in Summerlin, Nevada in 1990.  Over the next decade, roughly 300 roundabouts are built throughout the country.  These were mostly single-lane or multi-lane roundabouts with 1x2 configurations.  A lot of literature existed in other countries but nobody really knew how these "guinea pig" roundabouts would perform in America.

2000-2005:  The “simple”  roundabout era
In March 2000, the IIHS releases a study entitled “Crash Reductions Following Installation of Roundabouts in the United States” .  This is taken directly from the study - “Of the 24 intersections studied, 21 were previously controlled by stop signs, and 3 were controlled by traffic signals. Fifteen of the roundabouts were single-lane circulation designs, and 9, all in Colorado, were multilane.”   This routinely cited study concluded that roundabouts reduce total crashes by 39%, injury crashes by 76%, and fatal crashes by 90%.  After the release of the study, roundabouts gain further acceptance.  Agencies build more and more roundabouts, mimicking the “simple”  configurations analyzed in the IIHS study (single-lane and 1x2 multi-lane).  By 2005, there are roughly 2000 modern roundabouts in America.

2006-current:  The “complex”  roundabout era
By the mid 2000s, most consider it “settled science”  that roundabouts are safer.  Agencies feel emboldened to design more "complex" roundabouts with 2x2 configurations and even some triple-lane roundabouts.  The problem is these complex configurations were seeing abysmally high crash rates that weren't jiving with the 2000 IIHS study.  We are talking 10X increases in crashes; suffice it to say that is not a 39% decrease!  Today, there are roughly 5000 roundabouts in America and about 100 of them have 2x2 or 2x3 configurations. 

So the focus of this thread has largely been on the "complex" roundabouts with 2x2 and 2x3 configurations.  By highlighting a small subset of roundabouts that aren’t working well, does that mean I’m trying to discredit all roundabouts en masse?

Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 24, 2016, 09:28:05 PM
No, it does not necessarily mean that. And there are posts of yours that show an interest (perhaps even genuine) in determining what factors cause certain roundabouts to perform poorly.

But what I was drawing from is a general perception (possibly misguided), that you consider a stoplight to be superior and a roundabout a alternative novelty that must be proven. The history of roundabouts in America is only useful in understanding roundabouts as a relatively modern concept; this on paper (screen?) supports the assertion that more research needs to be done, but it also suggests (intentionally or unintentionally) that roundabouts in general are a newfangled fad that's worth discrediting.

As english si has illustrated, however, there are plenty of places in the world where roundabouts have a longer and more established history, and the sort of problems we see here don't happen nearly to the same extent there. And all these ideas that get thrown around on here (median fencing, elimination of objects, specific striping and signage, large or small diameter, elimination of circulating lanes) are definitely not ubiquitous in these other places. Elsewhere in the world, roundabouts of all sorts function much better than here.

I think, in order to have a straight conversation on the topic, we need to consider those multi-lane roundabouts that perform well. You asked for an example, and english si provided you with a whole town. Now that you have the data you were seeking, can we assume you'll be using it for fair analysis?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 27, 2016, 08:42:47 AM
Well, you may want to add traffic numbers to that statement. Maybe both drivers in your town have to share same car, hence there are no accidents?
Only A Roads have traffic counts, and some of these legs are measured away from the roundabout, after some side turns (which add traffic to the roundabout).
Roundabout 1 - legs of 11363, 16818, 18470, 16569. 31610
Roundabout 2 - legs of 18804, 20388, 18470, 26135. 41898
Roundabout 3 - legs of 14997, 14917, 26135. 28024
Roundabout 4 - legs of 14917, 14917, unknown. At least 14917 vehicles use the roundabout daily
Roundabout 5 - legs of 20388, 20388, unknown, unknown. There probably is a lazy bit of counting here, but at least 20388 vehicles use the roundabout daily (as one leg certainly has that figure).

A mix of traffic figures, but none are small.

OK, to put things in perspective:
An number often mentioned in this thread is 0.7 crashes per 1 million vehicles. For the numbers you have, that means 1 crash a month to 4 crashes a year.
And crash doesn't mean that police had to use power tools to remove trapped people; it is something serious enough to call insurance; e.g. dent on a door...
Are you sure you can find data on events like that?

As a matter of fact, I can find a few accidents in Buckinghamshire  roundabouts attended by firefighters just within one month of 2014: Wednesday 23 July, 12.34am; Sunday 20 July, 2.41am; Tuesday 8 July, 11.23am.

I am not sure which roundabouts you had in mind; but if these collisions were on circles you mentioned, then accident rate for a given month is higher than on traffic light controlled intersections in US (and US drivers are indeed statistically less safe than UK)
Title: Re: Crash prone 'modern roundabouts'
Post by: cl94 on October 27, 2016, 11:18:09 AM
Very few US intersections have leg traffic counts as high as some of those, either.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on October 27, 2016, 11:24:42 AM
An number often mentioned in this thread is 0.7 crashes per 1 million vehicles. For the numbers you have, that means 1 crash a month to 4 crashes a year.
Which is very high.
Quote
And crash doesn't mean that police had to use power tools to remove trapped people; it is something serious enough to call insurance; e.g. dent on a door...
Duh!
Quote
Are you sure you can find data on events like that?
I can, the problem is a lack of datums to create data. It's hard to find data when there's almost zero to find.

I found 2011 data that covers the busiest 4 roundabouts. 3 slight collisions, all at the busiest roundabout, none of which have anything to do with the junction being a roundabout, but have everything to do with the junction being a junction, the road they took place on being a slope, and the road being slippery at the time. Only 3 of the 6 cars have any damage (one collision was entirely damage free) and there were no injuries. But that's one year - and a big spike - and still fewer (and far less severe) than a mile long stretch of straight road with no junctions and only a couple of driveways up the top of the hill - we don't see a 889 post thread here on "crash prone straight roads" as there no vendetta against them.

3 collisions in a year at that roundabout is a collision rate of 0.196. Let's call it 0.2.
Quote
As a matter of fact, I can find a few accidents in Buckinghamshire roundabouts attended by firefighters just within one month of 2014: Wednesday 23 July, 12.34am; Sunday 20 July, 2.41am; Tuesday 8 July, 11.23am.
I've googled them and the two early hours (which suggests that the issue is less likely to be the existence of a roundabout rather than any other form of at-grade junction) ones aren't in Buckinghamshire. The other one was near that second busiest roundabout I mentioned, but wasn't actually at the junction itself.

Lets say we count that anyway and pretend that the crash was not only at the roundabout, but a monthly occurance that year (rather than the one off it was), just to skew things your way, and add that to the 0 crashes recorded in 2011 (despite the surfaces of roads in the area being so potholed as to nearly cause accidents, getting the council in trouble that year), and you get a value of 0.52 per million vehicles.
Quote
then accident rate for a given month
A skewed month designed to make your case, but one that can only find just 2 serious crashes at roundabouts in a very large town despite that town having about 100 roundabouts.
Quote
circles
If you don't even understand the terminology, what's the point in bothering to discuss it?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 27, 2016, 11:51:09 AM
An number often mentioned in this thread is 0.7 crashes per 1 million vehicles. For the numbers you have, that means 1 crash a month to 4 crashes a year.
Which is very high.
Quote
And crash doesn't mean that police had to use power tools to remove trapped people; it is something serious enough to call insurance; e.g. dent on a door...
Duh!
Quote
Are you sure you can find data on events like that?
I can, the problem is a lack of datums to create data. It's hard to find data when there's almost zero to find.

I found 2011 data that covers the busiest 4 roundabouts. 3 slight collisions, all at the busiest roundabout, none of which have anything to do with the junction being a roundabout, but have everything to do with the junction being a junction, the road they took place on being a slope, and the road being slippery at the time. Only 3 of the 6 cars have any damage (one collision was entirely damage free) and there were no injuries. But that's one year - and a big spike - and still fewer (and far less severe) than a mile long stretch of straight road with no junctions and only a couple of driveways up the top of the hill - we don't see a 889 post thread here on "crash prone straight roads" as there no vendetta against them.

3 collisions in a year at that roundabout is a collision rate of 0.196. Let's call it 0.2.
Quote
As a matter of fact, I can find a few accidents in Buckinghamshire roundabouts attended by firefighters just within one month of 2014: Wednesday 23 July, 12.34am; Sunday 20 July, 2.41am; Tuesday 8 July, 11.23am.
I've googled them and the two early hours (which suggests that the issue is less likely to be the existence of a roundabout rather than any other form of at-grade junction) ones aren't in Buckinghamshire. The other one was near that second busiest roundabout I mentioned, but wasn't actually at the junction itself.

Lets say we count that anyway and pretend that the crash was not only at the roundabout, but a monthly occurance that year (rather than the one off it was), just to skew things your way, and add that to the 0 crashes recorded in 2011 (despite the surfaces of roads in the area being so potholed as to nearly cause accidents, getting the council in trouble that year), and you get a value of 0.52 per million vehicles.
Quote
then accident rate for a given month
A skewed month designed to make your case, but one that can only find just 2 serious crashes at roundabouts in a very large town despite that town having about 100 roundabouts.
Quote
circles
If you don't even understand the terminology, what's the point in bothering to discuss it?

Just a few posts ago you were claiming

I'd love to post collision data from the several multi-lane roundabouts in my town. But as there haven't been any collisions at the roundabouts for over 20 years, there's no data to find. ;)

Now we're talking numbers. See the change?

I did not look for any bad or good month. I opened first page I found, believe it or not.
Assembling full statistics out of these accidents reports.. You know, I am not paid for that.  :ded: My point was not to show that Buckinghamshire is oh-so-dangerous place. Point is, you perfectly demonstrated that safety issues may be less obvious than a casual observer would believe.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 09, 2016, 08:28:04 PM
A serious accident occurred at a roundabout in Walker, Michigan. 
http://woodtv.com/2016/11/04/walker-pd-driver-may-have-suffered-medical-condition-before-crash/

Accidents are up since the roundabout opened in 2015:
http://www.mlive.com/walker/index.ssf/2016/07/roundabout_use_in_walker_bring.html

Here was the pre-roundabout condition.  Adding a protected left turn could have improved the safety of this intersection without building a costly roundabout (just my opinion):
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 15, 2016, 07:40:36 PM
Roundabout at Auburn and Main Still Causing Car Carnage
http://www.mystateline.com/news/roundabout-at-auburn-and-main-still-causing-car-carnage


Going from single digit crashes to nearly triple digit crashes a year.  This roundabout is just so much safer for everyone.  Great job.  Just fantastic.

CRASH DATA:
2012 - 3 crashes (Jan-Jun)
2013 - roundabout constructed
2014 - 86 crashes
2015 - 91 crashes
2016 - 71 crashes (Jan-Oct)

Title: Re: Crash prone 'modern roundabouts'
Post by: doorknob60 on November 15, 2016, 08:52:16 PM
Maybe doesn't add a lot to this discussion we haven't already heard, but ODOT just uploaded this today:

Title: Re: Crash prone 'modern roundabouts'
Post by: UCFKnights on November 15, 2016, 10:23:46 PM
A new "double" 2 lane roundabout was constructed right after a new bridge over I-75 in Gainesville, FL. Here's Google Street View during contruction:
https://www.google.com/maps/@29.6258591,-82.3883651,3a,75y,210.13h,68.7t/data=!3m6!1e1!3m4!1sPF5UUK8WoIjdeW7QewCnrw!2e0!7i13312!8i6656

I didn't take pictures as I first saw it tonight and it was dark out, but few cars are using it so far as its leading to a new development with only one store open and few people seemingly aware of the new route. Once this get some traffic, I can't imagine it being safe and having good flow.

I'll try to go back and get some pictures, but the bridge drops immediately into the roundabout, which has its first exit into another roundabout that exits to 2 roads and back into the roundabout, and the next exit into a stop sign facing the road I pictured (where the left turn lane enters the roundabout under construction). I'll have to get pictures, but this is probably the worst roundabout I've seen yet
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on November 17, 2016, 08:17:23 PM
Fun facts on Carmel roundabouts: http://www.indystar.com/story/news/local/hamilton-county/2016/11/17/carmels-opens-100th-roundabout/93966544/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 22, 2016, 04:22:37 PM
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/CIC-COM-1129-100-Roundabouts-2-720x540_zpsywnfurwv.jpg)
http://www.gooddaycarmel-bepartofthepositive.com/single-post/2016/11/18/Carmel-celebrates-historic-opening-of-100th-roundabout

As mentioned, Carmel opened its 100th roundabout at Rangeline Road and Carmel Drive on November 17th, 2016.  But to be honest, I have my concerns about this one.  This 2x2 geometry reminds me of Rockford’s “wreck-it”  roundabout or Ann Arbor’s Ellsworth roundabout.  This quite possibly could be the first roundabout in Carmel to average 100 crashes a year (would be fitting being the 100th roundabout and all!).  According to the Carmel Police Department Annual Reports, this busy intersection averaged 27 crashes a year from 2012-2014.  We will have to wait and see how many crashes occur moving forward.

Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on November 22, 2016, 06:44:52 PM
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/CIC-COM-1129-100-Roundabouts-2-720x540_zpsywnfurwv.jpg)
http://www.gooddaycarmel-bepartofthepositive.com/single-post/2016/11/18/Carmel-celebrates-historic-opening-of-100th-roundabout

As mentioned, Carmel opened its 100th roundabout at Rangeline Road and Carmel Drive on November 17th, 2016.  But to be honest, I have my concerns about this one.  This 2x2 geometry reminds me of Rockford’s “wreck-it”  roundabout or Ann Arbor’s Ellsworth roundabout.  This quite possibly could be the first roundabout in Carmel to average 100 crashes a year (would be fitting being the 100th roundabout and all!).  According to the Carmel Police Department Annual Reports, this busy intersection averaged 27 crashes a year from 2012-2014.  We will have to wait and see how many crashes occur moving forward.

ya i wouldn't be making grand pronouncements on things like this, we'll see if crashes go up. this intersection is the busiest in carmel at around 22,000 cars a day.  I was against this roundabout because it simply wasn't necessary. There are several multi-lane roundabouts in the city and 2 more will be going in on rangeline next year.  there will be 2 more multi-lane ones on towne road on the west side of town.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 22, 2016, 08:13:47 PM
Armdale Roundabout safety probed
http://thechronicleherald.ca/metro/1195561-armdale-roundabout-safety-probed

The Armdale rotary in Halifax, Nova Scotia was completed in 1956 and was converted to modern roundabout standards in 2007 (although I’ll note there is no truck apron at the roundabout).  A few years after the conversion, municipal staff noted a “sharp and sustained”  increase in accidents (jumping from the low 60s to the high 90s).  Here are a few recent news reports of injury accidents that have occurred at the roundabout:

http://www.cbc.ca/news/canada/nova-scotia/armdale-roundabout-crash-sends-3-to-hospital-with-serious-injuries-1.3116629
http://www.cbc.ca/news/canada/nova-scotia/armdale-roundabout-motorcyclist-crash-1.3300385

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 27, 2016, 11:25:50 PM
Two motorcyclists were killed after striking a newly constructed roundabout in Manteca, California.  These street outlaws definitely picked the wrong drag strip to race down. 

Quote
Witnesses said the trio was racing in an easterly direction on Woodward between Union Road and Airport Way at about 4:15 p.m. when they collided with the roundabout, leaving more than 100 feet of skid marks before they struck the circular traffic directional barrier leaving pieces of motorcycles scattered about the roadway and then flying more than 100 feet beyond.
http://www.mantecabulletin.com/section/38/article/139257/

Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 30, 2016, 05:53:06 PM
Two motorcyclists were killed after striking a newly constructed roundabout in Manteca, California.  These street outlaws definitely picked the wrong drag strip to race down. 

Quote
Witnesses said the trio was racing in an easterly direction on Woodward between Union Road and Airport Way at about 4:15 p.m. when they collided with the roundabout, leaving more than 100 feet of skid marks before they struck the circular traffic directional barrier leaving pieces of motorcycles scattered about the roadway and then flying more than 100 feet beyond.
http://www.mantecabulletin.com/section/38/article/139257/



Is that troll bait?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 01, 2016, 07:16:42 PM
The multiple fatalities at the Manteca roundabout highlight how dangerous roundabouts can be when approaching them at high speeds.  It’s putting things into perspective, not troll bait.   Just consider why the IIHS believes roundabouts are safer:

Quote
Roundabouts are a safer alternative to traffic signals and stop signs. The tight circle of a roundabout forces drivers to slow down, and the most severe types of intersection crashes – right-angle, left-turn and head-on collisions – are unlikely.http://www.iihs.org/iihs/topics/t/roundabouts/topicoverview

It’s an absurd statement if you think about it.  How do roundabouts “force”  drivers to slow down?   Drivers can either slow down or come to a "dead stop".   Of course this is the same agency that claims roundabouts reduce fatal crashes by 90%... there is no limit to the IIHS absurdity.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on December 01, 2016, 07:29:11 PM
Is that troll bait?
Looks more like goat feed to lure people onto the bridge.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 01, 2016, 07:47:46 PM
Is that troll bait?
Looks more like goat feed to lure people onto the bridge.
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Random/035ostrich_468x538_zpsmti9fabj.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 01, 2016, 07:48:41 PM
Quote from: IIHS
The tight circle of a roundabout forces drivers to slow down, and the most severe types of intersection crashes – right-angle, left-turn and head-on collisions – are unlikely.

It’s an absurd statement if you think about it.  How do roundabouts “force”  drivers to slow down?   Drivers can either slow down or come to a "dead stop".

It's not "force" in the sense that a roundabout will stomp on the brakes for you. It's "force" in the sense that, if you choose to not slow down, you'll probably bin it.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 01, 2016, 08:23:25 PM
Quote from: IIHS
The tight circle of a roundabout forces drivers to slow down, and the most severe types of intersection crashes – right-angle, left-turn and head-on collisions – are unlikely.

It’s an absurd statement if you think about it.  How do roundabouts “force”  drivers to slow down?   Drivers can either slow down or come to a "dead stop".

It's not "force" in the sense that a roundabout will stomp on the brakes for you. It's "force" in the sense that, if you choose to not slow down, you'll probably bin it.

From my experience, it is either full stop to let traffic pass, or step on throttle for extra 10 MPH to fit into that gap...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 01, 2016, 08:28:39 PM
Quote from: IIHS
The tight circle of a roundabout forces drivers to slow down, and the most severe types of intersection crashes – right-angle, left-turn and head-on collisions – are unlikely.

It’s an absurd statement if you think about it.  How do roundabouts “force”  drivers to slow down?   Drivers can either slow down or come to a "dead stop".

It's not "force" in the sense that a roundabout will stomp on the brakes for you. It's "force" in the sense that, if you choose to not slow down, you'll probably bin it.

From my experience, it is either full stop to let traffic pass, or step on throttle for extra 10 MPH to fit into that gap...

Okay then.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on December 02, 2016, 02:21:47 AM
It’s an absurd statement if you think about it.  How do roundabouts “force”  drivers to slow down?   Drivers can either slow down or come to a "dead stop".   Of course this is the same agency that claims roundabouts reduce fatal crashes by 90%... there is no limit to the IIHS absurdity.

Similar arguments could be made for speed bumps, speed tables, chicanes, or more simply, designing any roadway with unnecessary curves (the later making up many of the modern subdivision layout principles of the late 1990s and early 2000s).
Title: Re: Crash prone 'modern roundabouts'
Post by: 6a on December 02, 2016, 09:38:05 AM
Two motorcyclists were killed after striking a newly constructed roundabout in Manteca, California.  These street outlaws definitely picked the wrong drag strip to race down. 

Quote
Witnesses said the trio was racing in an easterly direction on Woodward between Union Road and Airport Way at about 4:15 p.m. when they collided with the roundabout, leaving more than 100 feet of skid marks before they struck the circular traffic directional barrier leaving pieces of motorcycles scattered about the roadway and then flying more than 100 feet beyond.
http://www.mantecabulletin.com/section/38/article/139257/



Is that troll bait?

Nooooooooo, this (http://www.citylab.com/weather/2016/11/all-hail-carmel-indiana-americas-king-of-roundabouts/508943/?utm_source=atlas) is troll bait ;)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 02, 2016, 06:15:50 PM
Roundabout crash makes car airborne, leaves two dead
http://www.krcrtv.com/north-coast-news/fatal-crash-on-roundabout-leaves-two-dead/189582788

Another incident where a vehicle slams into the center median of a roundabout.  Both the driver and passenger were killed.




 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 02, 2016, 06:35:00 PM
Vehicle bursts into flames after woman hits roundabout while lost in Washington County
http://fox6now.com/2016/11/28/vehicle-starts-on-fire-after-woman-hits-roundabout-while-lost-in-washington-county/

(https://localtvwiti.files.wordpress.com/2016/11/washington-county6.jpg)


Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on December 02, 2016, 06:39:04 PM
So if you are going to google every serious roundabout accident in the USA and report on a regular basis, you need to also report on all the serious non roundabout collisions so we can have a fair feel for the ratio of roundabout collisions to non roundabout collisions in each locality.    I think you will be far busier reporting on all the non roundabout crashes.   In my metro area there are many serious accidents reported every day, often with fatalities, and with it being a quite rare occasion that one involves a roundabout (maybe once every year or so for the ones you've already reported for us).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 03, 2016, 06:11:42 AM
So if you are going to google every serious roundabout accident in the USA and report on a regular basis, you need to also report on all the serious non roundabout collisions so we can have a fair feel for the ratio of roundabout collisions to non roundabout collisions in each locality.    I think you will be far busier reporting on all the non roundabout crashes.   In my metro area there are many serious accidents reported every day, often with fatalities, and with it being a quite rare occasion that one involves a roundabout (maybe once every year or so for the ones you've already reported for us).
Well, first of all - there are far less roundabouts than normal intersections. Being as advertised as super-duper safe, I expect roundabouts to be immune to driver mistakes. And given roundabouts are far and few in between and so safe, I expect only a tiny share of twice-an-hour urban fatalities to be on roundabouts. Hard to say, but my first impression is that rate of posts tradephoric writes here is disproportionally high.
And, interestingly enough, if you look at the thread carefully, you may get an idea about roundabout major failure mode for fatal accidents. Which, if you look even more carefully, may not be a major failure mode in UK due to differences in design approaches
But, who cares - pray The Safest Roundabout! FWHA got no money or time to learn - only money for new projects!
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 03, 2016, 08:40:29 AM
Quote
Being as advertised as super-duper safe, I expect roundabouts to be immune to driver mistakes.

That's where most people get it wrong. Roundabouts don't make people immune to mistakes...but they normally reduce the severity of people's mistakes.

Btw, please show where they have been advertised as such.  Even the world's safest roads will have an accident or fatality on occasion.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 03, 2016, 09:22:23 AM
Quote
Being as advertised as super-duper safe, I expect roundabouts to be immune to driver mistakes.

That's where most people get it wrong. Roundabouts don't make people immune to mistakes...but they normally reduce the severity of people's mistakes.

Btw, please show where they have been advertised as such.  Even the world's safest roads will have an accident or fatality on occasion.
OK,  lets start from the beginning.
There is a concept in general safety called "hierarchy of controls". Usually 5 levels are defined:
Elimination; Substitution; Engineering; Administration; Personal protective equipment. Higher in the list is preferable; for example moving work from the roof to ground level, if possible, is much more efficient in eliminating hazard of falling. Much better that safety belts, which must be worn when working up there.

We're talking here about Engineering vs Administrative levels, since Eliminating intersections (or prohibiting driving) is not an option; and Substitution - say with public transportation and specially trained drivers - is a big can of worms.
Administrative is basically all the regulations - speed limit, don't drink and drive, read the effing driver manual one in a while etc. Try to avoid mistakes.
Engineering is about making sure mistakes have minimal consequences - which is better than administrative. Use of railings along the road an divider between oncoming lanes, for example.

And this is where roundabouts fail miserably - approaching them at excessive speed leaves no chance. For regular intersection, I can pray hard and blow horn if traffic light jumps in front of me; for US designed roundabout this is a guaranteed accident. See the problem?

I believe it was our friend @english_si who posted a picture of roundabout with a through ramp for runaway traffic; I cannot find that at the moment. Which can be slightly improved - for example entire island may be paved; once that is done -  some ways of sequencing traffic to further improve safety may be implemented to further improve safety..

But this requires safety-minded engineering, not spending-driven approach..
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 03, 2016, 10:55:55 AM
And this is where roundabouts fail miserably - approaching them at excessive speed leaves no chance. For regular intersection, I can pray hard and blow horn if traffic light jumps in front of me; for US designed roundabout this is a guaranteed accident. See the problem?

This is true of every curve in existence (which means it's true of every skewed intersection at which one road S-curves to make the angles closer to 90°.  It's also true of every three-way intersection and every intersection with five or more connecting roads.

Drivers running into things while traveling at stupidly excessive speeds should not be our primary concern here.  A punk driver might do substantial damage to those in the vehicle and the roundabout island.  As @tradephoric has pointed out, it's even possible that serious damage be done to other vehicles.  However, I'd say the likelihood of stupid speed-punk behavior doing damage to multiple vehicles is less at a roundabout than at a red light.  Running a red light, you have the substantial risk of T-boning another vehicle at speed.

I recently T-boned a car at less than 30 mph because I was lost in thought and blew a red light, and you should have seen the wreck my Pathfinder made of that Honda Accord; now imagine the carnage if the speed had been 50 mph instead.  But, with a roundabout, something about them makes everyone else already be on the lookout for traffic entering the intersection, not simply assuming everyone else will stop.  That other driver, I'm sure, would have seen me coming in time to stop short of the accident–because he would have, by virtue of the roundabout's design–been made to slow down and become cautious.  I would have too, of course, but I'm still assuming stupid behavior on my part.

At a stoplight, all it takes is one inattentive driver to cause some carnage.  At a roundabout, it seems to take either more than one inattentive driver or some seriously excessive speed (or both).
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on December 03, 2016, 02:48:10 PM
And this is where roundabouts fail miserably - approaching them at excessive speed leaves no chance. For regular intersection, I can pray hard and blow horn if traffic light jumps in front of me; for US designed roundabout this is a guaranteed accident. See the problem?

This is true of every curve in existence (which means it's true of every skewed intersection at which one road S-curves to make the angles closer to 90°.  It's also true of every three-way intersection and every intersection with five or more connecting roads.

Drivers running into things while traveling at stupidly excessive speeds should not be our primary concern here.  A punk driver might do substantial damage to those in the vehicle and the roundabout island.  As @tradephoric has pointed out, it's even possible that serious damage be done to other vehicles.  However, I'd say the likelihood of stupid speed-punk behavior doing damage to multiple vehicles is less at a roundabout than at a red light.  Running a red light, you have the substantial risk of T-boning another vehicle at speed.

I recently T-boned a car at less than 30 mph because I was lost in thought and blew a red light, and you should have seen the wreck my Pathfinder made of that Honda Accord; now imagine the carnage if the speed had been 50 mph instead.  But, with a roundabout, something about them makes everyone else already be on the lookout for traffic entering the intersection, not simply assuming everyone else will stop.  That other driver, I'm sure, would have seen me coming in time to stop short of the accident–because he would have, by virtue of the roundabout's design–been made to slow down and become cautious.  I would have too, of course, but I'm still assuming stupid behavior on my part.

At a stoplight, all it takes is one inattentive driver to cause some carnage.  At a roundabout, it seems to take either more than one inattentive driver or some seriously excessive speed (or both).

Exactly on target with those comments.   I had an idiot blindly follow the large dump truck in front of them into the roundabout near my home last night (the dump trunk had plenty of time and correctly entered the roundabout, the following driver wasn't paying attention and should have yielded to oncoming traffic in the circle [me]).  Because I'm paying full attention in the roundabout, I'm able to apply the brakes and easily avoid the idiot (while blowing my horn and making some unfriendly hand gestures on the side).  So other than some ruffled feathers and the clueless driver needing new underwear, there was no collision.
Title: Re: Crash prone 'modern roundabouts'
Post by: Mr_Northside on December 03, 2016, 03:52:58 PM
Being as advertised as super-duper safe, I expect roundabouts to be immune to driver mistakes.

With all due respect, this is the dumbest thing I've read or heard in at least a month.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 03, 2016, 08:14:18 PM
And this is where roundabouts fail miserably - approaching them at excessive speed leaves no chance. For regular intersection, I can pray hard and blow horn if traffic light jumps in front of me; for US designed roundabout this is a guaranteed accident. See the problem?
Drivers running into things while traveling at stupidly excessive speeds should not be our primary concern here.  A punk driver might do substantial damage to those in the vehicle and the roundabout island.  As @tradephoric has pointed out, it's even possible that serious damage be done to other vehicles.  However, I'd say the likelihood of stupid speed-punk behavior doing damage to multiple vehicles is less at a roundabout than at a red light.  Running a red light, you have the substantial risk of T-boning another vehicle at speed.

I recently T-boned a car at less than 30 mph because I was lost in thought and blew a red light, and you should have seen the wreck my Pathfinder made of that Honda Accord; now imagine the carnage if the speed had been 50 mph instead.  But, with a roundabout, something about them makes everyone else already be on the lookout for traffic entering the intersection, not simply assuming everyone else will stop.  That other driver, I'm sure, would have seen me coming in time to stop short of the accident—because he would have, by virtue of the roundabout's design—been made to slow down and become cautious.  I would have too, of course, but I'm still assuming stupid behavior on my part.

Well, most accidents we have are preventable ones. People do make mistakes, and that is the major source of traffic problems.
To put things in perspective - 1/3 of all trafic deaths is caused by alcohol. That is 1 person per hour in US.
You don't care about that problem?.. Well, let's mirror that: Too bad you survived your accident, we don't need idiots on the road.

Harsh? Sure. So try to be nice guy for once.


This is true of every curve in existence (which means it's true of every skewed intersection at which one road S-curves to make the angles closer to 90°.  It's also true of every three-way intersection and every intersection with five or more connecting roads.
[....]
At a stoplight, all it takes is one inattentive driver to cause some carnage.  At a roundabout, it seems to take either more than one inattentive driver or some seriously excessive speed (or both).

Well, that is why mountain roads are often seen as dangerous, that is why curve radius is regulated. Message is, there is no reason to deliberatly create such hazards.

And there are many scenarios when single mistake results in  a serious accident  on roundabout, as shown above.  I have hard time tying to think of single-person mistake on a traditional intersection without other  traffic. Even crashing into a pole involves both loss of directional control and failure to brake properly

Being as advertised as super-duper safe, I expect roundabouts to be immune to driver mistakes.

With all due respect, this is the dumbest thing I've read or heard in at least a month.

Oh, this must be your first time reading about roundabouts?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 04, 2016, 03:31:02 AM
Being as advertised as super-duper safe, I expect roundabouts to be immune to driver mistakes.

With all due respect, this is the dumbest thing I've read or heard in at least a month.

Oh, this must be your first time reading about roundabouts?

Your expectation of "immun(ity)" is ridiculous. The FHWA's initial study never concluded that any sort of collision would be eliminated entirely. Just reduced.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 04, 2016, 09:08:44 AM
Being as advertised as super-duper safe, I expect roundabouts to be immune to driver mistakes.

With all due respect, this is the dumbest thing I've read or heard in at least a month.

Oh, this must be your first time reading about roundabouts?

Your expectation of "immun(ity)" is ridiculous. The FHWA's initial study never concluded that any sort of collision would be eliminated entirely. Just reduced.

Usual wording is "virtually eliminated".
Check it out:
https://www.google.com/search?q=roundabout+virtually+eliminate&ie=utf-8&oe=utf-8

Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 04, 2016, 09:28:14 AM
Being as advertised as super-duper safe, I expect roundabouts to be immune to driver mistakes.

With all due respect, this is the dumbest thing I've read or heard in at least a month.

Oh, this must be your first time reading about roundabouts?

Your expectation of "immun(ity)" is ridiculous. The FHWA's initial study never concluded that any sort of collision would be eliminated entirely. Just reduced.

Usual wording is "virtually eliminated".
Check it out:
https://www.google.com/search?q=roundabout+virtually+eliminate&ie=utf-8&oe=utf-8

As shown in the very first google link: "virtually eliminate high- speed right-angle and head-on crashes"

And that, it does do.

When you provide a link, and you're going to quote a line and even provide a link to such quotes, at least quote the entire sentence, not just two words. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 04, 2016, 09:33:03 AM
Being as advertised as super-duper safe, I expect roundabouts to be immune to driver mistakes.

With all due respect, this is the dumbest thing I've read or heard in at least a month.

Oh, this must be your first time reading about roundabouts?

Your expectation of "immun(ity)" is ridiculous. The FHWA's initial study never concluded that any sort of collision would be eliminated entirely. Just reduced.

Usual wording is "virtually eliminated".
Check it out:
https://www.google.com/search?q=roundabout+virtually+eliminate&ie=utf-8&oe=utf-8

As shown in the very first google link: "virtually eliminate high- speed right-angle and head-on crashes"

And that, it does do.

When you provide a link, and you're going to quote a line and even provide a link to such quotes, at least quote the entire sentence, not just two words.

When I quote something, I expect people to actually read it - and that is exactly why I didn't bother quote FHWA. Let me reconstruct entire dialog for you:

-Your expectation of "immun(ity)" is ridiculous. The FHWA's initial study never concluded that any sort of collision would be eliminated entirely. Just reduced.
-Usual wording is "virtually eliminated" (link).

Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 04, 2016, 09:39:31 AM
I'm confused.  So you're agreeing with us that they never concluded that any sort of collision would be eliminated entirely.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 04, 2016, 09:56:14 AM
I'm confused.  So you're agreeing with us that they never concluded that any sort of collision would be eliminated entirely.
not entirely, but virtually.
I believe smallpox is the only thing people could entirely eliminate - and even then never say never.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 04, 2016, 05:25:02 PM
At this point, I'd say we've well established that roundabouts don't automatically reduce crashes to quite the degree they keep being said to–even injury crashes.  Let's step away from the semantics and agree on that.



Well, most accidents we have are preventable ones. People do make mistakes, and that is the major source of traffic problems.
To put things in perspective - 1/3 of all trafic deaths is caused by alcohol. That is 1 person per hour in US.
You don't care about that problem?

Wow, talk about putting words in someone's mouth.  Did I say I don't care about drunk driving at some point in this discussion?  That was out of the blue.

I'm not entirely sure what direction that argument is going, though.  My recent crash was caused by people (me) making a mistake.  Not drunkenness but inattentiveness.  And my point in even bringing it up is that roundabouts can help mitigate the risk of serious injury and death due to people making mistakes.

Well, let's mirror that: Too bad you survived your accident, we don't need idiots on the road.

Harsh? Sure. So try to be nice guy for once.

Point taken.  And I mean that.

But again, you're not actually mirroring what I said.  What I said was 'Drivers running into things while traveling at stupidly excessive speeds should not be our primary concern here.'  That is not the same thing as saying drivers who have accidents ought not to survive.  My simple point is that, every so often, someone doing something utterly reckless and foolish will have a terrible wreck, and it is not the job of engineers to eliminate that possibility.  That's all.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 04, 2016, 06:12:28 PM
At this point, I'd say we've well established that roundabouts don't automatically reduce crashes to quite the degree they keep being said to–even injury crashes.  Let's step away from the semantics and agree on that.
I don't mean "automatic" - but see my logic below.
But again, you're not actually mirroring what I said.  What I said was 'Drivers running into things while traveling at stupidly excessive speeds should not be our primary concern here.'  That is not the same thing as saying drivers who have accidents ought not to survive.  My simple point is that, every so often, someone doing something utterly reckless and foolish will have a terrible wreck, and it is not the job of engineers to eliminate that possibility.  That's all.

Well, I think you're wrong. Job of engineers is to create environment where mistakes are not getting aggregated. If you will, a job of engineer is to put a smoother curve and railings along dangerous spot. This is done to reduce both number of crashes (turn radius, warning signs)  and consequences of those (railings, divided highway). This is done exactly for people who fail to maintain control.. How is that different from treatment of  city intersection?

Or, looking at extreme... Of course, someone going 100 MPH over 35 MPH speed limit is asking for trouble - but putting automatic machine guns to ensure they get what they deserve is a bit excessive!
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on December 04, 2016, 10:35:15 PM
Quote
Being as advertised as super-duper safe, I expect roundabouts to be immune to driver mistakes.

That's where most people get it wrong. Roundabouts don't make people immune to mistakes...but they normally reduce the severity of people's mistakes.

The types of severe/fatal single-car wrecks that have been brought up here are very unlikely to occur in conventional signalized intersections.  There's not much to hit.  Roundabouts, however, have a ton of stuff to hit--curbing, signs, lighting, landscaping, art--and due to the geometry of the intersection, it's easier to hit it if you're not paying attention/inebriated/trying to be a snazzbucket, because it obstructs the straight line path.  In these particular scenarios, they greatly compound the severity of people's mistakes.  There's trade-offs.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 05, 2016, 05:19:08 PM
The types of severe/fatal single-car wrecks that have been brought up here are very unlikely to occur in conventional signalized intersections.  There's not much to hit. 

Except other cars, of course. At a conventional signalized intersection, there is substantial probability that the severe/fatal single-car wrecks that have been brought up here would have actually been severe/fatal multi-car wrecks.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 05, 2016, 05:42:34 PM
The types of severe/fatal single-car wrecks that have been brought up here are very unlikely to occur in conventional signalized intersections.  There's not much to hit. 

Except other cars, of course. At a conventional signalized intersection, there is substantial probability that the severe/fatal single-car wrecks that have been brought up here would have actually been severe/fatal multi-car wrecks.

Interesting question.. Most of single vehicle crashes we discuss occur in low traffic situations.
 And in those situations roundabout wouldn't prevent multivehicle event anyway.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 05, 2016, 06:13:52 PM
The types of severe/fatal single-car wrecks that have been brought up here are very unlikely to occur in conventional signalized intersections.  There's not much to hit. 

Except other cars, of course. At a conventional signalized intersection, there is substantial probability that the severe/fatal single-car wrecks that have been brought up here would have actually been severe/fatal multi-car wrecks.

Interesting question.. Most of single vehicle crashes we discuss occur in low traffic situations.
 And in those situations roundabout wouldn't prevent multivehicle event anyway.

A lone car on the crossroad at a stoplight creates that potential. The odds are less than at a busier time of day, but a T-bone is a T-bone, no matter the traffic volume.

At a stoplight, the cars are likely to be traveling at full speed and partially blind to each other (commonly 90°), whereas at a roundabout at least one of them is bound to be traveling slowly (correctly) and there's a 50/50 chance that the cautious vehicle will be pointed more towards the offender (with the offender approaching from the right rather than the left).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 05, 2016, 06:27:25 PM
The types of severe/fatal single-car wrecks that have been brought up here are very unlikely to occur in conventional signalized intersections.  There's not much to hit. 

Except other cars, of course. At a conventional signalized intersection, there is substantial probability that the severe/fatal single-car wrecks that have been brought up here would have actually been severe/fatal multi-car wrecks.

Interesting question.. Most of single vehicle crashes we discuss occur in low traffic situations.
 And in those situations roundabout wouldn't prevent multivehicle event anyway.

A lone car on the crossroad at a stoplight creates that potential. The odds are less than at a busier time of day, but a T-bone is a T-bone, no matter the traffic volume.

At a stoplight, the cars are likely to be traveling at full speed and partially blind to each other (commonly 90°), whereas at a roundabout at least one of them is bound to be traveling slowly (correctly) and there's a 50/50 chance that the cautious vehicle will be pointed more towards the offender (with the offender approaching from the right rather than the left).

there is a difference between potential and certain severe accident...
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on December 05, 2016, 07:05:55 PM
The types of severe/fatal single-car wrecks that have been brought up here are very unlikely to occur in conventional signalized intersections.  There's not much to hit. 

Except other cars, of course. At a conventional signalized intersection, there is substantial probability that the severe/fatal single-car wrecks that have been brought up here would have actually been severe/fatal multi-car wrecks.

In the scenario I was outlining, there are no other cars in the intersection.  If someone goes blazing through a red light at 100mph and there's no one else in the intersection, there's no wreck there. If someone goes blazing into a roundabout at 100mph, and there's no one else in the roundabout, they'll hit curbing, and most likely flip.

All that said, if you take the second scenario, and a car happens to be inside the roundabout on the same side, the benefits of the roundabout go out the window.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 11, 2017, 11:57:36 PM
The Lee Road roundabouts at Whitmore Lake Road and U.S. 23 in Green Oak Township saw 40 accidents that resulted in injuries (between 2011-2016). Last year, 16 injury accidents were called in to 911, including 15 serious enough to require EMS assistance and one instance in which the crash victim refused EMS.

Livingston County's worst intersections for injury crashes
http://www.livingstondaily.com/story/news/local/community/livingston-county/2017/02/10/livingston-countys-worst-intersections-injury-crashes/97607006/
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 12, 2017, 01:53:30 AM
The Lee Road roundabouts at Whitmore Lake Road and U.S. 23 in Green Oak Township

I don't think I've seen a double roundabout diagram in the US before. The only one I'm familiar with is in Kelowna, BC. Here's the two side by side...

Michigan on left, British Columbia on right:
(http://i.imgur.com/AksmzW3.png) (http://i.imgur.com/l4h6DLn.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 15, 2017, 12:15:24 AM
Traffic crashes continue to rise at Bluffton roundabout
http://www.wjcl.com/article/traffic-crashes-continue-to-rise-at-bluffton-roundabout/8800659
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 21, 2017, 02:43:49 PM
Less than a year after opening, the city of Dublin is dumping $29,046 at MTJ Engineering to study the 161-Riverside Drive roundabout design.  According to the article, there have been 77 crashes at the roundabout since opening on Aug. 13, 2016.  After six months, 77 crashes.  That’s really bad considering the intersection only averaged 12 crashes per year before the roundabout was constructed.

77 crashes in 6 months or 12 crashes in 1 year?  Those safe roundabouts are really doing the trick in Dublin.

http://www.thisweeknews.com/news/20170214/riverside-161-roundabout-design-being-reviewed
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 22, 2017, 10:58:49 AM
It looks like they are using HAWK signals to meter traffic at the 136th and Keystone Parkway roundabout in Carmel.  Maybe i'm confused, but they aren't going to use traffic signals?  Here some news articles regarding the changes.

http://wishtv.com/2017/02/17/carmel-installs-new-metering-system-at-keystone-parkway-and-136th-street/
https://archive.org/details/Traffic_metering_of_136th_Street_and_Keystone_Parkway_Roundabout_Interchange 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on February 22, 2017, 11:46:18 AM
It looks like they are using HAWK signals to meter traffic at the 136th and Keystone Parkway roundabout in Carmel.  Maybe i'm confused, but they aren't going to use traffic signals?  Here some news articles regarding the changes.

http://wishtv.com/2017/02/17/carmel-installs-new-metering-system-at-keystone-parkway-and-136th-street/
https://archive.org/details/Traffic_metering_of_136th_Street_and_Keystone_Parkway_Roundabout_Interchange 

I wonder why they didn't choose "normal" two-lamp ramp meters like this one:

(http://www.ajfroggie.com/roadpics/ut/rampmeter.jpg)[photo courtesy of froggie]
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on February 22, 2017, 11:56:44 AM
When NJ metered traffic into a traffic circle, they simply used a traditional traffic light. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 22, 2017, 12:14:59 PM
I wonder why they didn't choose "normal" two-lamp ramp meters
When NJ metered traffic into a traffic circle, they simply used a traditional traffic light. 

A green light literally feet before a yield isn't the best idea. HAWKs can go dark when not in use, so there's less confusion.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on February 22, 2017, 12:51:34 PM
I wonder why they didn't choose "normal" two-lamp ramp meters
When NJ metered traffic into a traffic circle, they simply used a traditional traffic light. 

A green light literally feet before a yield isn't the best idea. HAWKs can go dark when not in use, so there's less confusion.

It was about a 1/4 mile prior to the circle, with signage stating Traffic Metering Light.  They were designed to reduce traffic going into the circle when the circle started getting clogged up, but wouldn't stop it completely, as businesses and other driveways could be located between the light and the circle.  I glanced quickly at Google images seeing if I could find something, but came up empty.  The last circle with metering lights I'm aware of was the Somers Point Circle near Ocean City, and that circle was removed before 2010.

This was also at a time when roundabouts didn't exist, so traffic circles (and the lights) were pretty unique.  And Jersey traffic circles didn't have yield signs!



Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on February 22, 2017, 05:29:39 PM
Signalized roundabouts in the UK are quite common, but they tend to control both the circulating roadway and the entrance, and are used more often in big multilane roundabouts that more resemble the old-style US rotaries than the designs FHWA favors.

As for why they're not using traditional ramp meters, I think it's because they want to cycle the lights less frequently and allow a variable number of cars through per "non-red" cycle. Green would also imply they don't need to yield to circulating traffic when entering, so unless it was significantly upstream of the roundabout it could be more confusing than the HAWK-style approach.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on February 22, 2017, 09:04:08 PM
The meters will only come on during peak periods when traffic backs up (the rush hours when the nearby high school is discharging or pulling in mass traffic or when the evening rush hour is producing high volumes of traffic on the keystone ramp.   The vast majority of the time the signals will simply be dark. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 22, 2017, 10:44:48 PM
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/CIC-COM-1129-100-Roundabouts-2-720x540_zpsywnfurwv.jpg)
http://www.gooddaycarmel-bepartofthepositive.com/single-post/2016/11/18/Carmel-celebrates-historic-opening-of-100th-roundabout

As mentioned, Carmel opened its 100th roundabout at Rangeline Road and Carmel Drive on November 17th, 2016.  But to be honest, I have my concerns about this one.  This 2x2 geometry reminds me of Rockford’s “wreck-it”  roundabout or Ann Arbor’s Ellsworth roundabout.  This quite possibly could be the first roundabout in Carmel to average 100 crashes a year (would be fitting being the 100th roundabout and all!).  According to the Carmel Police Department Annual Reports, this busy intersection averaged 27 crashes a year from 2012-2014.  We will have to wait and see how many crashes occur moving forward.

Here's one crash to tally up at the Rangeline Road and Carmel Drive roundabout.  A Carmel Police officer was injured inside the roundabout a few days ago. 

http://fox59.com/2017/02/21/carmel-police-officer-injured-in-motorcycle-crash/
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on February 23, 2017, 10:08:41 AM
Likely this has more to do with the quality of the at fault driver than the properties of the roundabout:

"Guzman was arrested for operator never licensed, a class C misdemeanor. He was also cited for expired license plates and performing an unsafe lane change."
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 23, 2017, 11:17:45 AM
Likely this has more to do with the quality of the at fault driver than the properties of the roundabout:

"Guzman was arrested for operator never licensed, a class C misdemeanor. He was also cited for expired license plates and performing an unsafe lane change."

It has a lot to do with the properties of the roundabout.  The Rangeline Road and Carmel Drive roundabout has a 2x2 geometry.  These geometries are notorious for having high crash rates.  You ignore the fact that the average crash rate of 2x2 roundabouts are roughly 4x higher than signalized intersections and instead focus on trivialities. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on February 23, 2017, 11:56:49 AM
Likely this has more to do with the quality of the at fault driver than the properties of the roundabout:

"Guzman was arrested for operator never licensed, a class C misdemeanor. He was also cited for expired license plates and performing an unsafe lane change."

It has a lot to do with the properties of the roundabout.  The Rangeline Road and Carmel Drive roundabout has a 2x2 geometry.  These geometries are notorious for having high crash rates.  You ignore the fact that the average crash rate of 2x2 roundabouts are roughly 4x higher than signalized intersections and instead focus on trivialities. 

I saw it that cjw2001 was simply poking a hole in your using the example of an unlicensed driver performing an illegal maneuver in an unregistered vehicle as evidence in support of a claim about safety.

While I agree that the design of multi-lane roundabouts is likely a contributing factor to many of the crashes at them (and this very thread has convinced me that it's likely), the specific example referred to was not particularly valuable to the conversation.  I might call it "clutter."
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 23, 2017, 01:40:41 PM
Likely this has more to do with the quality of the at fault driver than the properties of the roundabout:

"Guzman was arrested for operator never licensed, a class C misdemeanor. He was also cited for expired license plates and performing an unsafe lane change."

It has a lot to do with the properties of the roundabout.  The Rangeline Road and Carmel Drive roundabout has a 2x2 geometry.  These geometries are notorious for having high crash rates.  You ignore the fact that the average crash rate of 2x2 roundabouts are roughly 4x higher than signalized intersections and instead focus on trivialities. 

I saw it that cjw2001 was simply poking a hole in your using the example of an unlicensed driver performing an illegal maneuver in an unregistered vehicle as evidence in support of a claim about safety.

While I agree that the design of multi-lane roundabouts is likely a contributing factor to many of the crashes at them (and this very thread has convinced me that it's likely), the specific example referred to was not particularly valuable to the conversation.  I might call it "clutter."
License does little to improve driving skills.
There is probably some fraction of unlicensed and/or drunk drivers on each intersection in US, they - and some properly licensed sober drivers - sometimes perform unsafe maneuvers, and probably some vehicles are not fully legal (inspected, registered, insured..).
This all gets enveloped into some numbers by statistics.
Now big question - I asked it before - if we're OK with Darwin approach towards non-topnotch drivers (drunk, sick, poorly trained, eldery, inexperienced, distracted... ), or design has to take into account that some drivers are less than perfect?
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on February 23, 2017, 03:00:56 PM
License does little to improve driving skills.

Considering that the driver in question improperly changed lanes, and studying for a license involves learning when it's OK to change lanes and how to safely do that, I'd say your claim is baseless.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 23, 2017, 03:10:51 PM
License does little to improve driving skills.

Considering that the driver in question improperly changed lanes, and studying for a license involves learning when it's OK to change lanes and how to safely do that, I'd say your claim is baseless.
I see people using roundabout lanes incorrectly at least once a week.. I would say 1 out of 20-50 drivers does that. If you include failure to signal intentions (NY term for not using turn signal) - probably 1 out of 3-5. I doubt that many drivers are unlicensed...
And in NY the only thing you really need to know to pass a test - drunk driving is bad, BAD, BAD!!! Add a pinch of common sense (like "running over police officer who signals you to stop on green light" is probably an incorrect answer) , and you easily get passing grade.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 23, 2017, 04:11:19 PM
Roundabout safety on Hilliard's radar
http://www.thisweeknews.com/news/20170221/roundabout-safety-on-hilliards-radar

According to a Mid-Ohio Regional Planning Commission (MORPC) study, the top 3 most crash prone intersections in Hilliard from 2013-2015 have been at modern roundabouts.  The Cemetery Road and Main Street roundabout had the highest number of accidents in Hilliard:  233 crashes during the three-year period.  Of course maybe 233 unlicensed drivers have been driving around the streets of Hilliard wreaking havoc. 

Here’s a complete list of the 5 most crash prone intersections in Hilliard according to the MORPC study:
#1.  Cemetery Road and Main Street (roundabout) — 233 crashes including 7 minor injuries
#2.  Main Street and Scioto Darby Road (roundabout) — 141 crashes including 8 minor injuries
#3.  Davidson Road and Britton Parkway (roundabout) — 72 crashes including 7 minor injuries
#4.  Cemetery Road and Lyman Drive (traffic signal) — 58 crashes (doesn’t mention how many injuries)
#5.  Cemetery Road and Britton Parkway (traffic signal) — 52 crashes (doesn’t mention how many injuries)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on February 23, 2017, 04:13:12 PM
I see people using roundabout lanes incorrectly at least once a week.. I would say 1 out of 20-50 drivers does that. If you include failure to signal intentions (NY term for not using turn signal) - probably 1 out of 3-5. I doubt that many drivers are unlicensed...

Your argument is basically...
1. Some people drive incorrectly.
2. Most of them have licenses.
3. Therefore, licensing doesn't help people drive correctly.

That's the same logic as...
1. Some people get injured while riding a bicycle.
2. Most of them are wearing helmets.
3. Therefore, helmets do not protect cyclists from injury.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 23, 2017, 04:47:13 PM
I see people using roundabout lanes incorrectly at least once a week.. I would say 1 out of 20-50 drivers does that. If you include failure to signal intentions (NY term for not using turn signal) - probably 1 out of 3-5. I doubt that many drivers are unlicensed...

Your argument is basically...
1. Some people drive incorrectly.
2. Most of them have licenses.
3. Therefore, licensing doesn't help people drive correctly.

That's the same logic as...
1. Some people get injured while riding a bicycle.
2. Most of them are wearing helmets.
3. Therefore, helmets do not protect cyclists from injury.

Well, tell me how helmets affect broken leg statistics...

License guarantees some minimum skill level for new driver. Not a very high level, I would say. Then there is experience accumulated over years - insurance companies definitely think so, and there are some legal provisions - like certain experience required to supervise learning driver.

In this case we have a 32 year who was never licensed. Do you think there was no driving experience involved? I doubt so, more like someone who never got pulled over in the past 10 years. Abruptly changing lanes in roundabout is more of a sign of someone getting confused than someone not knowing the law...
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on February 23, 2017, 05:36:42 PM
I see people using roundabout lanes incorrectly at least once a week.. I would say 1 out of 20-50 drivers does that. If you include failure to signal intentions (NY term for not using turn signal) - probably 1 out of 3-5. I doubt that many drivers are unlicensed...

Your argument is basically...
1. Some people drive incorrectly.
2. Most of them have licenses.
3. Therefore, licensing doesn't help people drive correctly.

That's the same logic as...
1. Some people get injured while riding a bicycle.
2. Most of them are wearing helmets.
3. Therefore, helmets do not protect cyclists from injury.

Well, tell me how helmets affect broken leg statistics...

License guarantees some minimum skill level for new driver. Not a very high level, I would say. Then there is experience accumulated over years - insurance companies definitely think so, and there are some legal provisions - like certain experience required to supervise learning driver.

Sounds to me like we need more drivers' license and educational reform (along with a healthy dose of personal responsibility). When did ignorance become an acceptable excuse? When has that ever worked in fighting a traffic ticket?

Quote
In this case we have a 32 year who was never licensed. Do you think there was no driving experience involved? I doubt so, more like someone who never got pulled over in the past 10 years. Abruptly changing lanes in roundabout is more of a sign of someone getting confused than someone not knowing the law...

Agree to disagree. People are becoming lazier drivers overall.  Just about any big box parking lot will give a good example on how careless and lazy people are. But, like your statement, it's based on biased observation. Lane lines, like red lights seem to have a gray area of definition until someone crashes. Just on my drive to work this morning, it was mind-blowing how many people sneak through seconds after the light has turned red.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 23, 2017, 05:59:48 PM
While I have swayed my view on roundabouts many times, there is one certainty that I cannot ignore: drunk drivers and idiots will always be a thing. While designing a roadway around those types of people is obviously not of utmost important to engineers, one of the main goals of an engineer is to design a road that is safe for all drivers. That does, unfortunately, mean designing for drunks and idiots. A road that is the most forgiving will likely produce the least amount of collisions. Roundabouts are not forgiving at all. If you don't react to them, you will crash. You have to turn the steering wheel, brake, (shift if necessary) and accelerate back out of it, while simultaneously maintaining lane position and following all relevant signage. It's very easy to do if you aren't an idiot or drunk, but if you are, it's definitely not as easy as sailing through a signal.

Now, with that in mind, here's where I think roundabouts are still quite good even when idiots and drunks are involved. A drunk or inattentive driver sailing through a red light has potentially fatal consequences. At the very least, any collision (likely of the t-bone variety) could be very severe, with life-threatening injuries almost a certainty. Roundabouts, as far as I know, have far fewer severe collisions, and overall less deaths even though most double-lane roundabouts have more collisions than the intersection that they replaced.

We basically have two options here: 1) accept the fact the double lane roundabouts produce more collisions, but are safer, or 2) revert back to large signals because roundabouts cause too many collisions, despite an overall reduction in severity and fatalities. It's almost to the point where it's more a factor of which control type produces more optimal traffic flow. Both signals and roundabouts have their ups and downs; neither is better than the other, IMO.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 23, 2017, 06:00:24 PM
People are becoming lazier drivers overall.  Just about any big box parking lot will give a good example on how careless and lazy people are. But, like your statement, it's based on biased observation. Lane lines, like red lights seem to have a gray area of definition until someone crashes. Just on my drive to work this morning, it was mind-blowing how many people sneak through seconds after the light has turned red.
Congratulations! You just achieved OLD FART rank!

The grass much greener and drivers much better those days, right?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 23, 2017, 06:01:57 PM
Reconstruction of Jacaranda roundabout to start March 6
http://www.heraldtribune.com/news/20170222/reconstruction-of-jacaranda-roundabout-to-start-march-6

The city of Venice is spending $1.1 million dollars to reconstruct a roundabout that was built in 2011.  The roundabout at Jacaranda Boulevard and Venice Avenue is the highest crash prone intersection in the region and they believe the proposed changes (which includes realigning the splitter islands, bigger yield signs, and pavement marking changes) will cut down on the number of crashes.  Of course much of the roundabout will remain two-lanes, which seems to be the real culprit when you have these high crash rate roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on February 23, 2017, 06:04:18 PM
While I have swayed my view on roundabouts many times, there is one certainty that I cannot ignore: drunk drivers and idiots will always be a thing. While designing a roadway around those types of people is obviously not of utmost important to engineers, one of the main goals of an engineer is to design a road that is safe for all drivers. That does, unfortunately, mean designing for drunks and idiots. A road that is the most forgiving will likely produce the least amount of collisions.

Putting the Devil's Advocate hat on...
Where do we draw the line of "idiot" drivers? Even the crash cushions in front of freeway hazards have their design limits. Is it the idiot driving drunk in a Prius going 45 mph or an idiot drunk and hitting up on heroin behind the wheel of U-haul truck going 70 mph?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 23, 2017, 06:07:00 PM
We basically have two options here: 1) accept the fact the double lane roundabouts produce more collisions, but are safer, or 2) revert back to large signals because roundabouts cause too many collisions, despite an overall reduction in severity and fatalities. It's almost to the point where it's more a factor of which control type produces more optimal traffic flow. Both signals and roundabouts have their ups and downs; neither is better than the other, IMO.
Well, I would add some more statements: Properly designed intersection is better than poorly designed roundabout. Properly designed roundabout is better than poorly designed intersection.
Now my problem is that I see no good understanding of what makes roundabout properly designed, and I see no desire to learn.... Light controlled intersections are in business for .. hundred years, right? - and are pretty well understood...
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on February 23, 2017, 06:09:33 PM
People are becoming lazier drivers overall.  Just about any big box parking lot will give a good example on how careless and lazy people are. But, like your statement, it's based on biased observation. Lane lines, like red lights seem to have a gray area of definition until someone crashes. Just on my drive to work this morning, it was mind-blowing how many people sneak through seconds after the light has turned red.
Congratulations! You just achieved OLD FART rank!

The grass much greener and drivers much better those days, right?

Huh, so 33 equates to 'old fart'. Gotcha. Recent statistics for crashes where distracted driving was involved seem to differ with your assertion.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 23, 2017, 06:18:10 PM
People are becoming lazier drivers overall.  Just about any big box parking lot will give a good example on how careless and lazy people are. But, like your statement, it's based on biased observation. Lane lines, like red lights seem to have a gray area of definition until someone crashes. Just on my drive to work this morning, it was mind-blowing how many people sneak through seconds after the light has turned red.
Congratulations! You just achieved OLD FART rank!

The grass much greener and drivers much better those days, right?

Huh, so 33 equates to 'old fart'. Gotcha. Recent statistics for crashes where distracted driving was involved seem to differ with your assertion.
Some people are born as old farts, some remain young in their heart past 100 anniversary..
Relax, distracted driving was a pet issue 2 FHWA administrators ago...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 23, 2017, 06:55:48 PM
While I have swayed my view on roundabouts many times, there is one certainty that I cannot ignore: drunk drivers and idiots will always be a thing. While designing a roadway around those types of people is obviously not of utmost important to engineers, one of the main goals of an engineer is to design a road that is safe for all drivers. That does, unfortunately, mean designing for drunks and idiots. A road that is the most forgiving will likely produce the least amount of collisions.

Putting the Devil's Advocate hat on...
Where do we draw the line of "idiot" drivers? Even the crash cushions in front of freeway hazards have their design limits. Is it the idiot driving drunk in a Prius going 45 mph or an idiot drunk and hitting up on heroin behind the wheel of U-haul truck going 70 mph?

I'm not sure I could define "idiot". The point is to design a forgiving roadway. I suppose someone who crashes on a road that was designed to be forgiving would be considered an idiot.

I do have one issue with forgiving roadways. They are very easy to drive on without paying attention. Americans are very relaxed drivers (except those who aren't). We prefer automatics. We build our cities in straight lines. Signals at crossroads, etc. The second you install a road feature that requires even a modicum of quick but difficult assessment, you may end up creating collisions that weren't there before.

Compared to single lane roundabouts, which are often low speed affairs and require almost no thinking other than "give way to the left", double lane roundabouts suffer because they are often installed along high speed roadways, and they require you to assess signage and pavement markings quickly, while simultaneously not crashing into the vehicle next to you. For most of us, this is no problem. But there are some drivers out there who are so incredibly dumb, so inattentive and lacking in skill...they can't handle quick thinking and *BAM* collision.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 23, 2017, 07:19:16 PM
I do have one issue with forgiving roadways. They are very easy to drive on without paying attention. Americans are very relaxed drivers (except those who aren't). We prefer automatics. We build our cities in straight lines. Signals at crossroads, etc. The second you install a road feature that requires even a modicum of quick but difficult assessment, you may end up creating collisions that weren't there before.

Compared to single lane roundabouts, which are often low speed affairs and require almost no thinking other than "give way to the left", double lane roundabouts suffer because they are often installed along high speed roadways, and they require you to assess signage and pavement markings quickly, while simultaneously not crashing into the vehicle next to you. For most of us, this is no problem. But there are some drivers out there who are so incredibly dumb, so inattentive and lacking in skill...they can't handle quick thinking and *BAM* collision.

Just brought up by your words:
Once upon a time, I was reading an article on interface on MTA ticket machines, ones selling fare cards for NYC subway.
The interface is minimalistic, and if you make a mistake, you need to start all over again. Why?
Well, because majority of customers use those machines quite often, know what to do, what to expect, and don't need fancy options.
Now for roads that is commuter vs out-of-towner dilemma. The only difference is that resetting after the *BAM* is a bit more difficult...
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on February 23, 2017, 07:25:51 PM
I do have one issue with forgiving roadways. They are very easy to drive on without paying attention. Americans are very relaxed drivers (except those who aren't). We prefer automatics. We build our cities in straight lines. Signals at crossroads, etc. The second you install a road feature that requires even a modicum of quick but difficult assessment, you may end up creating collisions that weren't there before.

Compared to single lane roundabouts, which are often low speed affairs and require almost no thinking other than "give way to the left", double lane roundabouts suffer because they are often installed along high speed roadways, and they require you to assess signage and pavement markings quickly, while simultaneously not crashing into the vehicle next to you. For most of us, this is no problem. But there are some drivers out there who are so incredibly dumb, so inattentive and lacking in skill...they can't handle quick thinking and *BAM* collision.

Just brought up by your words:
Once upon a time, I was reading an article on interface on MTA ticket machines, ones selling fare cards for NYC subway.
The interface is minimalistic, and if you make a mistake, you need to start all over again. Why?
Well, because majority of customers use those machines quite often, know what to do, what to expect, and don't need fancy options.
Now for roads that is commuter vs out-of-towner dilemma. The only difference is that resetting after the *BAM* is a bit more difficult...

Traffic reports are the same way.  They cater to the local motorist that uses the roads every day.  If a one-time visitor is going thru the city and doesn't know the nickname, they're not worried about it.

Current, local example:  When they say 'No delays on the Delaware River Bridges', they are clearly excluding the PA/NJ Turnpike Bridge situation.  Randomly listening to the radio, they do tend to mention the Turnpike Bridge closure more often on the weekend, when motorists not in their weekday routine may need to be a little more alert about unusual situations.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 23, 2017, 07:33:50 PM
Traffic reports are the same way.  They cater to the local motorist that uses the roads every day.  If a one-time visitor is going thru the city and doesn't know the nickname, they're not worried about it.

Current, local example:  When they say 'No delays on the Delaware River Bridges', they are clearly excluding the PA/NJ Turnpike Bridge situation.  Randomly listening to the radio, they do tend to mention the Turnpike Bridge closure more often on the weekend, when motorists not in their weekday routine may need to be a little more alert about unusual situations.
And the question is about the price of mistake: 30 seconds reset for MTA, hour in traffic for report (and thank you so much, Waze!), and possible injury in accident..
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on February 24, 2017, 01:17:15 PM
While I have swayed my view on roundabouts many times, there is one certainty that I cannot ignore: drunk drivers and idiots will always be a thing. While designing a roadway around those types of people is obviously not of utmost important to engineers, one of the main goals of an engineer is to design a road that is safe for all drivers. That does, unfortunately, mean designing for drunks and idiots. A road that is the most forgiving will likely produce the least amount of collisions.

Putting the Devil's Advocate hat on...
Where do we draw the line of "idiot" drivers? Even the crash cushions in front of freeway hazards have their design limits. Is it the idiot driving drunk in a Prius going 45 mph or an idiot drunk and hitting up on heroin behind the wheel of U-haul truck going 70 mph?

I'm not sure I could define "idiot". The point is to design a forgiving roadway. I suppose someone who crashes on a road that was designed to be forgiving would be considered an idiot.

I do have one issue with forgiving roadways. They are very easy to drive on without paying attention. Americans are very relaxed drivers (except those who aren't). We prefer automatics. We build our cities in straight lines. Signals at crossroads, etc. The second you install a road feature that requires even a modicum of quick but difficult assessment, you may end up creating collisions that weren't there before.

Compared to single lane roundabouts, which are often low speed affairs and require almost no thinking other than "give way to the left", double lane roundabouts suffer because they are often installed along high speed roadways, and they require you to assess signage and pavement markings quickly, while simultaneously not crashing into the vehicle next to you. For most of us, this is no problem. But there are some drivers out there who are so incredibly dumb, so inattentive and lacking in skill...they can't handle quick thinking and *BAM* collision.

Semantics aside, where's the limit on forgiving roadway? As you said, and I would agree, there are dangers to forgiving roadways too. Roads that are too straight and have no intersecting traffic can lull drivers to sleep or increase the temptation to play with their electronic devices. In many cases, we're talking about potentially designing for what are illegal behaviors...further graying the definition of a forgiving roadway.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 24, 2017, 02:34:41 PM
Semantics aside, where's the limit on forgiving roadway? As you said, and I would agree, there are dangers to forgiving roadways too. Roads that are too straight and have no intersecting traffic can lull drivers to sleep or increase the temptation to play with their electronic devices. In many cases, we're talking about potentially designing for what are illegal behaviors...further graying the definition of a forgiving roadway.
A well-known effect: once you improve technical safety, more relaxed attitude takes most of those gains back - not all of them. We have cars much more forgiving than they were years ago - ABS, seatbelt, airbags, crash mode test (keeping survivable volume intact). Partially taken back by higher speeds...

There is an urban legend that there were less accident with those working on high-rise structures before safety harness became mandatory (look at old pictures of NYC skyscraper construction to see how it was back then) - because people relied on themselves, not on layers of safety.  Not sure how true that is, and definitely such a story wouldn't buy you any points with EHS..
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on February 24, 2017, 03:26:15 PM
Roundabouts are not forgiving at all. If you don't react to them, you will crash. You have to turn the steering wheel, brake, (shift if necessary) and accelerate back out of it, while simultaneously maintaining lane position and following all relevant signage. It's very easy to do if you aren't an idiot or drunk, but if you are, it's definitely not as easy as sailing through a signal.

Almost all of those points are also true for single-lane roundabouts, yet what I think tradephoric has brought out over the course of this thread is that single-lane or hybrid single/double-lane roundabouts do better at safety.  I really do think it comes down to the number of circulating lanes.  As I had illustrated further up-thread are are non-sideswipe conflict points on a standard 2x2 roundabout.  With a single-laner, an approaching driver only has to watch for one lane of cross traffic, but with two lanes there's a lot more at play.  Now, I don't know if this is actually what has contributed to the crash rates tradephoric has illustrated, but the fact seems to be that there's something inherent in the complexity of a 2x2 that makes it more dangerous.

Now, some of this is bound to be a lack of familiarity and education in the USA compared to, say, the British isles.  With greater familiarity and education as to how a large roundabout works, it's likely that the number of these crashes would be reduced.  But there's a fine balance between designing for what should happen and what does happen.



In this case we have a 32 year who was never licensed. Do you think there was no driving experience involved? I doubt so, more like someone who never got pulled over in the past 10 years. Abruptly changing lanes in roundabout is more of a sign of someone getting confused than someone not knowing the law...

But driver's education is about more than just knowing the law.  It's about being familiar with something before you encounter it, so you know what to do when the time comes.  For example, I grew up in a small town.  In driver's ed class, we had to drive 30 miles away for freeway driving and we had to drive out of state for "city" driving–which was a town of 8000 people.  My intuition about how to use a dual left-turn lane was incorrect, and so I was taught in class what the proper thing to do is.  Then, when I moved to the Chicago area and actually encountered dual left-turn lanes, I was able to put my knowledge to use.  Similarly, this driver might have had 15 years of driving experience, but that doesn't mean he had any experience at all with multi-lane roundabouts.  Now, I highly doubt multi-lane roundabout navigation was taught in driver's ed 15 years ago, but it should be.  Licensing does matter.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 24, 2017, 05:28:30 PM
But driver's education is about more than just knowing the law.  It's about being familiar with something before you encounter it, so you know what to do when the time comes.  For example, I grew up in a small town.  In driver's ed class, we had to drive 30 miles away for freeway driving and we had to drive out of state for "city" driving–which was a town of 8000 people.  My intuition about how to use a dual left-turn lane was incorrect, and so I was taught in class what the proper thing to do is.  Then, when I moved to the Chicago area and actually encountered dual left-turn lanes, I was able to put my knowledge to use.  Similarly, this driver might have had 15 years of driving experience, but that doesn't mean he had any experience at all with multi-lane roundabouts.  Now, I highly doubt multi-lane roundabout navigation was taught in driver's ed 15 years ago, but it should be.  Licensing does matter.
Well, I don't think I heard much about roundabout at the time I got the license, and my first roundabout was navigated probably 10 years after getting the card. More than enough time to forget everything I read - even if it was in the manual at that time.
I don't think I ever read anything about dual-left lanes, but few spots we got around have (quite  helpful) dashed  lines painted on pavement...

Yet again - no sane person, licensed or not, would change lanes (or perform any other maneuver)  if they see it could lead to crash and injury of another driver (at least during peace time). Guy just didn't see a motorcycle - and that does happen now and then, roundabouts or not.  Had at least one close call myself - no consequences other than angry horn from the rider, lucky me.
Now, what it adds up to from my perspective:  roundabout with plenty of points requiring attention - and easy to miss small vehicle in another lane; lane curvature not helping to use side mirrors; getting in a wrong lane - meaning going to miss the turn and trying last second correction.... Easy situation for an expensive mistake. I can see myself being prone to such mistake - with many years of driving with valid license.  And yes, roundabout is a contributing factor.   Could same thing happen in regular intersection? Who knows, those intersection also have their fair share of problems...
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on February 25, 2017, 04:29:47 PM
It looks like they are using HAWK signals to meter traffic at the 136th and Keystone Parkway roundabout in Carmel.  Maybe i'm confused, but they aren't going to use traffic signals?  Here some news articles regarding the changes.


Here is a good picture of the new HAWK signal in action.  There are two sets of signals, one pictured here for eastbound traffic at the intersection where northbound ramp traffic from Keystone Parkway enters from the right.   The other set is just before the end of that same ramp.  I've driven by the area many times since these went live, but I've yet to see them in action as they only trigger when traffic has backed up.  Think these are mainly activating during the morning (and possibly the evening) rush hour.

(https://tribwxin.files.wordpress.com/2017/02/roundabout-signal.jpg?quality=85&strip=all&w=770)

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 25, 2017, 04:52:10 PM
It looks like they are using HAWK signals to meter traffic at the 136th and Keystone Parkway roundabout in Carmel.  Maybe i'm confused, but they aren't going to use traffic signals?  Here some news articles regarding the changes.


Here is a good picture of the new HAWK signal in action.  There are two sets of signals, one pictured here for eastbound traffic at the intersection where northbound ramp traffic from Keystone Parkway enters from the right.   The other set is just before the end of that same ramp.  I've driven by the area many times since these went live, but I've yet to see them in action as they only trigger when traffic has backed up.  Think these are mainly activating during the morning (and possibly the evening) rush hour.


And is it just me - or there is a perfect proof that roundabouts cannot handle high traffic? Yes, they are good in case traffic numbers a low, probably few hundred VPH... But I really want to see formalized guidelines...
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on February 25, 2017, 05:26:43 PM
It looks like they are using HAWK signals to meter traffic at the 136th and Keystone Parkway roundabout in Carmel.  Maybe i'm confused, but they aren't going to use traffic signals?  Here some news articles regarding the changes.


Here is a good picture of the new HAWK signal in action.  There are two sets of signals, one pictured here for eastbound traffic at the intersection where northbound ramp traffic from Keystone Parkway enters from the right.   The other set is just before the end of that same ramp.  I've driven by the area many times since these went live, but I've yet to see them in action as they only trigger when traffic has backed up.  Think these are mainly activating during the morning (and possibly the evening) rush hour.


And is it just me - or there is a perfect proof that roundabouts cannot handle high traffic? Yes, they are good in case traffic numbers a low, probably few hundred VPH... But I really want to see formalized guidelines...

Hundreds if not thousands of roundabouts, and because there's a traffic volume issue at one you say they all can't handle high volumes?

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 25, 2017, 06:01:45 PM

And is it just me - or there is a perfect proof that roundabouts cannot handle high traffic? Yes, they are good in case traffic numbers a low, probably few hundred VPH... But I really want to see formalized guidelines...

Hundreds if not thousands of roundabouts, and because there's a traffic volume issue at one you say they all can't handle high volumes?
Question is about numbers. I didn't see actual published performance datato be used as design inputs. Looks like they are not as high as people want them to be.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on February 25, 2017, 07:32:40 PM
The traffic volume issue at this roundabout is very time specific (when the nearby high school of 5,000 students generates a burst of traffic).   Most of the day this functions as a very normal roundabout.  The addition of the meters to handle these short term bursts in no way makes the roundabout a "bad" solution.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on February 25, 2017, 07:56:18 PM
I think it's fair to say (based on the experience in the UK) roundabouts with very unbalanced traffic patterns or very high volumes may need part-time or full-time signalization. That said (as I mentioned up-thread) in the US we probably wouldn't use the same approach since most US designs are for "small" roundabouts that are hard to signalize because of the lack of storage space in the circulating roadway - in the UK anything signalized would typically be the size of an old-school NJ rotary - and the volumes and layouts in the UK where roundabout signalization is typically used would normally warrant a free-flow interchange in the US.

Here's a UK government document on the subject (https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/329062/ltn-1-09_Signal_controlled_roundabouts.pdf).

Of course you still get the general injury/fatality crash benefits from roundabouts when they're signalized because the reduction in conflict points and avoidance of 90-degree angle of incidence is still in effect.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 25, 2017, 09:28:39 PM
The traffic volume issue at this roundabout is very time specific (when the nearby high school of 5,000 students generates a burst of traffic).   Most of the day this functions as a very normal roundabout.  The addition of the meters to handle these short term bursts in no way makes the roundabout a "bad" solution.
With all my respect... School is not a number!
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 01, 2017, 12:30:37 PM
You can’t make this stuff up.  The roundabout at Main and Cemetary in Hilliard is the most crash prone intersection in Ohio.  The engineering firm Burgess & Niples completed the roundabouts initial design.  Now Hilliard City officials want to shell out $220,000 to study the roundabout (along with 2 other double-lane roundabouts) and come up with modifications that would reduce the number of crashes.  Want to take a guess which engineering firm they want to hire?  Instead of paying $220,000 dollars to the very engineering firm who designed the most crash prone intersection in the state, i can tell you what's wrong over a $2.20 cup of coffee... it's a double-lane roundabout.  At least City Counsel is now questioning whether Burgess & Niple is the best choice to study the roundabout.

Quote
Hilliard roundabout study gets stop sign
http://www.thisweeknews.com/news/20170301/hilliard-roundabout-study-gets-stop-sign

Hilliard City Council put the brakes on an administrative initiative to hire the engineering firm Burgess & Niple to determine whether any modifications to the city's double-roundabout intersection on Main Street could reduce the number of accidents.

City Council members tabled the resolution Feb. 27 and asked public-services director Butch Seidle to arrange for representatives from Burgess & Niple to attend the March 13 meeting to discuss the issue.

City Council Vice President Kelly McGivern asked that the resolution be postponed until March 13 and that the engineering firm "provide an explanation" why it is qualified to review the work since the firm completed the roundabouts' initial design.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on March 03, 2017, 09:46:50 AM
You can’t make this stuff up.  The roundabout at Main and Cemetary in Hilliard is the most crash prone intersection in Ohio.  The engineering firm Burgess & Niples completed the roundabouts initial design.  Now Hilliard City officials want to shell out $220,000 to study the roundabout (along with 2 other double-lane roundabouts) and come up with modifications that would reduce the number of crashes.  Want to take a guess which engineering firm they want to hire?  Instead of paying $220,000 dollars to the very engineering firm who designed the most crash prone intersection in the state, i can tell you what's wrong over a $2.20 cup of coffee... it's a double-lane roundabout.  At least City Counsel is now questioning whether Burgess & Niple is the best choice to study the roundabout.

I see similar stuff all too often really.  A firm, politically connected, gets a job.  After the job is completed, results aren't what were expected.  The same firm that got the original job get another job to fix what they messed up in the first place.

The firm gets more money...and the politicians that allow it get re-elected.  It's a vicious cycle that has gone on for hundreds of years.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 03, 2017, 10:26:09 AM
I see similar stuff all too often really.  A firm, politically connected, gets a job.  After the job is completed, results aren't what were expected.  The same firm that got the original job get another job to fix what they messed up in the first place.

The firm gets more money...and the politicians that allow it get re-elected.  It's a vicious cycle that has gone on for hundreds of years.
Good thing that at least interstates have pretty stringent standards, and those standards are mostly followed...
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on March 03, 2017, 10:30:08 AM
I see similar stuff all too often really.  A firm, politically connected, gets a job.  After the job is completed, results aren't what were expected.  The same firm that got the original job get another job to fix what they messed up in the first place.

The firm gets more money...and the politicians that allow it get re-elected.  It's a vicious cycle that has gone on for hundreds of years.
Good thing that at least interstates have pretty stringent standards, and those standards are mostly followed...

Roadwise, yes.  But this activity occurs much more frequently in so many different areas.  Studies for buildings, trash trucks, parks, schools, etc, etc, etc. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 06, 2017, 12:04:00 PM
Quote
Carmel to require turn signals in roundabouts

Ever get frustrated trying to figure out when vehicles will exit a roundabout?

The Carmel City Council will consider an ordinance Monday to require people to use their turn signals to make it clear. Scofflaws will face a $100 fine.

"This is standard in countries with many roundabouts and allows a driver waiting to enter a roundabout to know whether a circulating car is going to cross in front or turn out of the circle," said Mayor Jim Brainard. "It will speed up our roundabouts and make them more efficient."

http://www.indystar.com/story/news/local/hamilton-county/2017/03/06/carmel-require-turn-signals-roundabouts/98686674/

There are roundabout experts who say drivers shouldn’t signal when exiting a roundabout.  In a roundabout webinar hosted by the University of Minnesota, Joe Gustafson from Washington County stated the following:

“We also would never tell a driver to use a right turn signal to exit a roundabout.  Again, that’s a through movement and we don’t want to create the impression that it’s a right turn.”  

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/CIC-COM-1129-100-Roundabouts-2-720x540_zpsywnfurwvyellow_zpsxupqlvhm.jpg)

Here’s an aerial of the new Rangeline Road and Carmel Drive roundabout.  Should the driver in the yellow path be required to signal when exiting the roundabout?  At no point do the pavement markings or signage indicate the driver is making a right turn.  There’s a straight arrow inside the roundabout.  It doesn’t make sense to require drivers to use their right turn signal indication as they are driving overtop a “straight only”  arrow.  It is confusing.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 06, 2017, 12:11:24 PM
Quote
Carmel to require turn signals in roundabouts

Ever get frustrated trying to figure out when vehicles will exit a roundabout?

The Carmel City Council will consider an ordinance Monday to require people to use their turn signals to make it clear. Scofflaws will face a $100 fine.

"This is standard in countries with many roundabouts and allows a driver waiting to enter a roundabout to know whether a circulating car is going to cross in front or turn out of the circle," said Mayor Jim Brainard. "It will speed up our roundabouts and make them more efficient."

http://www.indystar.com/story/news/local/hamilton-county/2017/03/06/carmel-require-turn-signals-roundabouts/98686674/

There are roundabout experts who say drivers shouldn’t signal when exiting a roundabout.  In a roundabout webinar hosted by the University of Minnesota, Joe Gustafson from Washington County stated the following:

“We also would never tell a driver to use a right turn signal to exit a roundabout.  Again, that’s a through movement and we don’t want to create the impression that it’s a right turn.”  
.....
Here’s an aerial of the new Rangeline Road and Carmel Drive roundabout.  Should the driver in the yellow path be required to signal when exiting the roundabout?  At no point do the pavement markings or signage indicate the driver is making a right turn.  There’s a straight arrow inside the roundabout.  It doesn’t make sense to require drivers to use their right turn signal indication as they are driving overtop a “straight only”  arrow.  It is confusing.

This is how cars would look like if designed by those designing roundabouts:
(http://cs4.pikabu.ru/images/big_size_comm/2015-05_2/14311088229659.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on March 06, 2017, 12:15:20 PM
Quote
Carmel to require turn signals in roundabouts

Ever get frustrated trying to figure out when vehicles will exit a roundabout?

The Carmel City Council will consider an ordinance Monday to require people to use their turn signals to make it clear. Scofflaws will face a $100 fine.

"This is standard in countries with many roundabouts and allows a driver waiting to enter a roundabout to know whether a circulating car is going to cross in front or turn out of the circle," said Mayor Jim Brainard. "It will speed up our roundabouts and make them more efficient."

http://www.indystar.com/story/news/local/hamilton-county/2017/03/06/carmel-require-turn-signals-roundabouts/98686674/

There are roundabout experts who say drivers shouldn’t signal when exiting a roundabout.  In a roundabout webinar hosted by the University of Minnesota, Joe Gustafson from Washington County stated the following:

“We also would never tell a driver to use a right turn signal to exit a roundabout.  Again, that’s a through movement and we don’t want to create the impression that it’s a right turn.”  

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/CIC-COM-1129-100-Roundabouts-2-720x540_zpsywnfurwvyellow_zpsxupqlvhm.jpg)

Here’s an aerial of the new Rangeline Road and Carmel Drive roundabout.  Should the driver in the yellow path be required to signal when exiting the roundabout?  At no point do the pavement markings or signage indicate the driver is making a right turn.  There’s a straight arrow inside the roundabout.  It doesn’t make sense to require drivers to use their right turn signal indication as they are driving overtop a “straight only”  arrow.  It is confusing.

I agree that's confusing.  I always signal when exiting so drivers waiting on the cross street know it's OK to start into the roundabout.  It also implies that, whenever you don't exit a roundabout, you should have your left signal on.  That seems counter-intuitive on the one hand (roundabouts have no left turns, so why a left signal?) but makes sense on the other hand (conventional signalling in the UK states you should signal right (our left) upon approaach when turning right.



This is how cars would look like if designed by those designing roundabouts:
(http://cs4.pikabu.ru/images/big_size_comm/2015-05_2/14311088229659.png)

Oh yes, precisely.  What a great argument.  Now I'm convinced, by the picture, that roundabouts are stupid and anyone who thinks otherwise is an idiot.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 06, 2017, 12:18:10 PM
Oh yes, precisely.  What a great argument.  Now I'm convinced, by the picture, that roundabouts are stupid and anyone who thinks otherwise is an idiot.
Those who think otherwise are fine. Those who believe otherwise...  And that seem to be overwhelming majority...
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on March 06, 2017, 12:25:19 PM
I find the recommended signalling technique for Waterloo Region to be easy enough:
http://www.regionofwaterloo.ca/en/gettingAround/How-To-Use-A-Roundabout.asp#signaling (http://www.regionofwaterloo.ca/en/gettingAround/How-To-Use-A-Roundabout.asp#signaling)

Quote
A roundabout is similar to an intersection with signals you need to signal the direction in which you are going to take.  When turning right, you need to signal right, when going straight you don't signal, and when turning left or doing a U-turn you signal left.  The only difference is that whenever you exit a roundabout you need to signal right to show you are exiting.  Below are step by step directions on how to signal:

Turning Right

Signal right as you approach the roundabout in the right-hand lane.
Maintain your signal through the roundabout and stay in the right-hand lane.
Maintain your signal as you exit in the right-hand lane.

Going Straight

Do not signal as you approach the roundabout and select the appropriate lane.
Stay in this lane until you need to exit the roundabout.
Signal right prior to your exit, and exit from the lane you are in.

Turning Left

Signal left as you approach the roundabout in the left-hand lane.
Maintain your signal through the roundabout and stay in the left-hand lane.
Signal right prior to your exit, and exit in the left-hand lane.

Going full circle (U-turn)

Signal left as you approach the roundabout in the left-hand lane.
Maintain your signal through the roundabout and stay in the left-hand lane.
Signal right prior to your exit, and exit in the left-hand lane.

I wish more people would signal right when exiting, so you're not left waiting for no reason.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 06, 2017, 12:39:04 PM
I find the recommended signalling technique for Waterloo Region to be easy enough:
http://www.regionofwaterloo.ca/en/gettingAround/How-To-Use-A-Roundabout.asp#signaling (http://www.regionofwaterloo.ca/en/gettingAround/How-To-Use-A-Roundabout.asp#signaling)

Quote
A roundabout is similar to an intersection with signals you need to signal the direction in which you are going to take.  When turning right, you need to signal right, when going straight you don't signal, and when turning left or doing a U-turn you signal left.  The only difference is that whenever you exit a roundabout you need to signal right to show you are exiting.  Below are step by step directions on how to signal:

Turning Right

Signal right as you approach the roundabout in the right-hand lane.
Maintain your signal through the roundabout and stay in the right-hand lane.
Maintain your signal as you exit in the right-hand lane.

Going Straight

Do not signal as you approach the roundabout and select the appropriate lane.
Stay in this lane until you need to exit the roundabout.
Signal right prior to your exit, and exit from the lane you are in.

Turning Left

Signal left as you approach the roundabout in the left-hand lane.
Maintain your signal through the roundabout and stay in the left-hand lane.
Signal right prior to your exit, and exit in the left-hand lane.

Going full circle (U-turn)

Signal left as you approach the roundabout in the left-hand lane.
Maintain your signal through the roundabout and stay in the left-hand lane.
Signal right prior to your exit, and exit in the left-hand lane.

I wish more people would signal right when exiting, so you're not left waiting for no reason.

Few complications:
-right signals are not  readily visible to those down the line. Pure geometry.
-visibility through roundabout center is supposed to be limited.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 06, 2017, 12:47:52 PM
I agree that's confusing.  I always signal when exiting so drivers waiting on the cross street know it's OK to start into the roundabout.  It also implies that, whenever you don't exit a roundabout, you should have your left signal on.  That seems counter-intuitive on the one hand (roundabouts have no left turns, so why a left signal?) but makes sense on the other hand (conventional signalling in the UK states you should signal right (our left) upon approaach when turning right.

If someone had their right turn on when exiting a roundabout i would assume they are about to make a right-turn into a driveway just past the roundabout.  In the aerial i posted above I'd assume you are about to pull into the gas station.  If somebody pulling out of the gas station wrongfully assumes you are about to pull into the gas station, that could lead to a crash. 
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on March 06, 2017, 12:56:11 PM
I think signaling is appropriate and should be encouraged (if not required), particularly on exits from the circular roadway; and, yes, you're turning right from the circular roadway when you exit a roundabout, even if there's no painted arrow saying that.

But given the serious lack of signaling discipline from American drivers in general, I doubt it'll ever be a widespread practice except in places that go out of their way to promote it like Carmel is planning to do.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 06, 2017, 01:46:46 PM
I think signaling is appropriate and should be encouraged (if not required), particularly on exits from the circular roadway; and, yes, you're turning right from the circular roadway when you exit a roundabout, even if there's no painted arrow saying that.
What if I am going straight to exit roundabout? And that seem a more common design approach - you barely need to move steering wheel to exit, you need to keep it turned to stay on circular path.
Title: Re: Crash prone 'modern roundabouts'
Post by: chays on March 06, 2017, 03:01:24 PM
I'm thinking that roundabouts will not be a better solution until we are a completely self-driving-car society.  Too much room for human error.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on March 06, 2017, 03:23:04 PM
I'm thinking that roundabouts will not be a better solution until we are a completely self-driving-car society.  Too much room for human error.

From the mid 1960's to early 1980's there were virtually 0 roundabouts in the US...and we had over 50,000 traffic deaths nearly every year during that era.  Today there's around 100 traffic deaths per day, and almost none occur in roundabouts.

I don't think roundabouts are really the problem here.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on March 06, 2017, 03:26:50 PM
Rather than citing UK recommendations, it might be better to see what Australia/NZ recommend, since their roundabouts are constructed with very similar standards and markings (heavy use of turbo markings, etc), and also use left/right/straight arrows leading up to the roundabout.

Since both drive on the left, I've changed the verbiage so that it can be comprehended quicker:

Quote from: NZTA
If you are going 'straight' through a roundabout:

- don't signal as you come up to the roundabout
- signal (right) as you pass the exit before the one you wish to take. At some small roundabouts it may not be possible to give three seconds warning, but it is courteous to give as much indication as you can.
https://goo.gl/YmYGfF

Quote from: NSW Roads and Maritime agency
Going straight ahead
...
You must indicate a (right) turn just before you exit unless it is not practical to do so.
https://goo.gl/wf2clW
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on March 06, 2017, 03:27:20 PM
I think signaling is appropriate and should be encouraged (if not required), particularly on exits from the circular roadway; and, yes, you're turning right from the circular roadway when you exit a roundabout, even if there's no painted arrow saying that.
What if I am going straight to exit roundabout? And that seem a more common design approach - you barely need to move steering wheel to exit, you need to keep it turned to stay on circular path.

This is the "going straight" instruction from Waterloo, which is consistent with UK/continental European practice:

Quote
Going Straight

Do not signal as you approach the roundabout and select the appropriate lane.
Stay in this lane until you need to exit the roundabout.
Signal right prior to your exit, and exit from the lane you are in.

As for whether "moving the steering wheel" matters, you barely have to move a steering wheel to change lanes or get on an exit ramp, yet you're expected to signal in that circumstance too.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 06, 2017, 04:15:08 PM
I think signaling is appropriate and should be encouraged (if not required), particularly on exits from the circular roadway; and, yes, you're turning right from the circular roadway when you exit a roundabout, even if there's no painted arrow saying that.
What if I am going straight to exit roundabout? And that seem a more common design approach - you barely need to move steering wheel to exit, you need to keep it turned to stay on circular path.

This is the "going straight" instruction from Waterloo, which is consistent with UK/continental European practice:

Quote
Going Straight

Do not signal as you approach the roundabout and select the appropriate lane.
Stay in this lane until you need to exit the roundabout.
Signal right prior to your exit, and exit from the lane you are in.

As for whether "moving the steering wheel" matters, you barely have to move a steering wheel to change lanes or get on an exit ramp, yet you're expected to signal in that circumstance too.

It is actually a bit difficult to apply plain road logic to roundabouts since very few roads have enough curvature to cause questions.  But if talking about exit - what is the move you indicate with a blinker? You can blink to move to an exit lane, or blink negotiating actual curvature at gore point. Exit I often take has a fairly long exit-only lane - and once I am in that lane I turn off my blinkers and just follow the lane.
On a same token - modern roundabouts often have dedicated "this exit only" lanes...
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on March 06, 2017, 04:46:42 PM
There are roundabout experts who say drivers shouldn’t signal when exiting a roundabout.  In a roundabout webinar hosted by the University of Minnesota, Joe Gustafson from Washington County stated the following:

“We also would never tell a driver to use a right turn signal to exit a roundabout.  Again, that’s a through movement and we don’t want to create the impression that it’s a right turn.”
Joe Gustafson is a menace who should be tried for gross misconduct, and perhaps even vehicular manslaughter by proxy. He's the main reason this thread is credible. Go gunning for him, rather than the Mayor of Carmel, who gets it.

By making something that is typically fairly unfamiliar to US drivers even more confusing by demanding that you shouldn't inform other drivers of your intentions, nor be informed by other drivers of what they will do, Gustafson is wilfully creating danger on the roads and encouraging careless driving.

Almost all near misses and crashes on UK roundabouts are created by people not realising a vehicle is coming round the circulatory carriageway. Signal discipline is often poor, but at least we know we should signal, rather than actively being told by muppets to not signal intent.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 06, 2017, 05:06:07 PM
There are roundabout experts who say drivers shouldn’t signal when exiting a roundabout.  In a roundabout webinar hosted by the University of Minnesota, Joe Gustafson from Washington County stated the following:

“We also would never tell a driver to use a right turn signal to exit a roundabout.  Again, that’s a through movement and we don’t want to create the impression that it’s a right turn.”
Joe Gustafson is a menace who should be tried for gross misconduct, and perhaps even vehicular manslaughter by proxy. He's the main reason this thread is credible. Go gunning for him, rather than the Mayor of Carmel, who gets it.

By making something that is typically fairly unfamiliar to US drivers even more confusing by demanding that you shouldn't inform other drivers of your intentions, nor be informed by other drivers of what they will do, Gustafson is wilfully creating danger on the roads and encouraging careless driving.

Almost all near misses and crashes on UK roundabouts are created by people not realising a vehicle is coming round the circulatory carriageway. Signal discipline is often poor, but at least we know we should signal, rather than actively being told by muppets to not signal intent.

And it looks like we're talking about somewhat different things here. It was mentioned that UK has somewhat different design.
So, if you don't mind - can you show some exemplary UK roundabout on a map? Not biggest and greatest, but regular ones with best possible design from your perspective?.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on March 06, 2017, 05:31:20 PM
While lordsutch's point about Oceanian roundabouts being more like US ones than British ones is a good one - though these rules don't disagree with the NZ or NSW ones posted above wrt straight on traffic (and I doubt they will much at all with the whole lot) - lets refresh on the rules of the second-lowest (half the rate of the US, despite being infested with roundabouts) road fatalities per distance stats.
Quote from: The Highway Code (https://www.gov.uk/guidance/the-highway-code/using-the-road-159-to-203)
Rule 184
On approaching a roundabout take notice and act on all the information available to you, including traffic signs, traffic lights and lane markings which direct you into the correct lane. You should
  • use Mirrors — Signal — Manoeuvre at all stages
    decide as early as possible which exit you need to take
  • give an appropriate signal (see Rule 186, below). Time your signals so as not to confuse other road users
  • get into the correct lane
  • adjust your speed and position to fit in with traffic conditions
  • be aware of the speed and position of all the road users around you.
Rule 185
When reaching the roundabout you should
  • give priority to traffic approaching from your right, unless directed otherwise by signs, road markings or traffic lights
  • check whether road markings allow you to enter the roundabout without giving way. If so, proceed, but still look to the right before joining
  • watch out for all other road users already on the roundabout; be aware they may not be signalling correctly or at all
  • look forward before moving off to make sure traffic in front has moved off.
(https://assets.digital.cabinet-office.gov.uk/media/559af891e5274a155c00001d/the-highway-code-rule-185.jpg)
Rule 185: Follow the correct procedure at roundabouts

Rule 186
Signals and position. When taking the first exit to the left, unless signs or markings indicate otherwise
  • signal left and approach in the left-hand lane
  • keep to the left on the roundabout and continue signalling left to leave.
When taking an exit to the right or going full circle, unless signs or markings indicate otherwise
  • signal right and approach in the right-hand lane
  • keep to the right on the roundabout until you need to change lanes to exit the roundabout
  • signal left after you have passed the exit before the one you want.
When taking any intermediate exit, unless signs or markings indicate otherwise
  • select the appropriate lane on approach to and on the roundabout
  • you should not normally need to signal on approach
  • stay in this lane until you need to alter course to exit the roundabout
  • signal left after you have passed the exit before the one you want.
When there are more than three lanes at the entrance to a roundabout, use the most appropriate lane on approach and through it.

Rule 187
In all cases watch out for and give plenty of room to
  • pedestrians who may be crossing the approach and exit roads
  • traffic crossing in front of you on the roundabout, especially vehicles intending to leave by the next exit
  • traffic which may be straddling lanes or positioned incorrectly
  • motorcyclists
  • cyclists and horse riders who may stay in the left-hand lane and signal right if they intend to continue round the roundabout. Allow them to do so
  • long vehicles (including those towing trailers). These might have to take a different course or straddle lanes either approaching or on the roundabout because of their length. Watch out for their signals.

I make that 32 times it says signal. The real roundabout experts are clear: Joe Gustafson is a dangerous quack who doesn't deserve to be considered a roundabout expert.


And it looks like we're talking about somewhat different things here. It was mentioned that UK has somewhat different design.
So, if you don't mind - can you show some exemplary UK roundabout on a map? Not biggest and greatest, but regular ones with best possible design from your perspective?.
The artists impression in the above picture is a perfectly typical UK roundabout design. This one picked at random (https://www.google.co.uk/maps/@54.609657,-3.1409292,394m/data=!3m1!1e3) might not be best possible design, but it is perfectly acceptable roundabout. Have another random one (https://www.google.co.uk/maps/@53.3441525,0.0039724,357m/data=!3m1!1e3), this time a county council one. The speed limit on all the arms is 60mph (hence the different surface on approach). How about a smaller one (https://www.google.co.uk/maps/@51.5718578,-1.7708922,454a,20y,22.79h/data=!3m1!1e3) - this one (again somewhat randomly picked) is more US in feel nowadays, with non-circulatory lane markings (https://www.google.co.uk/maps/@51.5718059,-1.7712906,3a,75y,16.77h,86.95t/data=!3m6!1e1!3m4!1sPTYuTVFLo-ZZLl7hafToLQ!2e0!7i13312!8i6656) and such like (the aerial view and the more-recent streetview are different: the red area is gone) - but the same rules of signalling are involved.

None of these are exemplary, but they do they job. I'd argue that the key issue in the US isn't design or geometry or whatever, but driver miseducation: the Aus/NZ stuff that lordsutch brought in (and brought up that UK roundabouts are slightly different) still seem to follow the same rules of the road, despite their different design.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 06, 2017, 05:55:31 PM

None of these are exemplary, but they do they job. I'd argue that the key issue in the US isn't design or geometry or whatever, but driver miseducation: the Aus/NZ stuff that lordsutch brought in (and brought up that UK roundabouts are slightly different) still seem to follow the same rules of the road, despite their different design.
Well, one - and possibly most important in the context - difference I can see is that no lanes are marked within roundabout.
Just to compare: https://www.google.com/maps/place/Malta,+NY+12020/@42.9700608,-73.8040097,691m/data=!3m1!1e3!4m5!3m4!1s0x89de3e54fcae9891:0x90c15e79d1ad5e9d!8m2!3d42.9854395!4d-73.7868236
Ones you have don't feature that spiral spool of lanes, and I would say it affects blinker strategy.
And the one you marked as a smaller one is the normal size over here, so although you say same rules apply - it would be interesting to see if same rules are actuallyfollowed.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on March 06, 2017, 07:01:29 PM
Well, one - and possibly most important in the context - difference I can see is that no lanes are marked within roundabout.
Other than the 'smaller' Swindon one, sure. Though that's, in part due to the small sample - some do (eg (https://www.google.co.uk/maps/@52.9495078,-0.9779082,3a,68.6y,339.13h,83.47t/data=!3m6!1e1!3m4!1sL-QYL8WzYSHoAMuEtJ-orQ!2e0!7i13312!8i6656)), other's don't and I just found two that don't. Not having markings is more typical, but markings are far from rare.

Confusing markings aren't good (the UK only spiralises if it signalises as it's formal allocation of lanes confuses us and creates panic), but in the US, I'd argue that the misleading markings aren't the problem, but a symptom: of the "don't signal" dogma problem.
Quote
And the one you marked as a smaller one is the normal size over here
The ones I randomly picked just happened to be big ones - in part as they are easier to see on the map. Smaller was comparative with the other two linked (again, same problem of picking one at random off a map zoomed out). The ones on the dumbell you linked would be seen as mid-sized here - and this (https://www.google.com/maps/@51.7485366,-0.575628,3a,75y,43.64h,83.18t/data=!3m7!1e1!3m5!1s0sGXPC5ZDeBB00983YZFjw!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3D0sGXPC5ZDeBB00983YZFjw%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D78.26967%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656) would be a roundabout that's smaller than average in the UK (though a common size).
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on March 06, 2017, 08:58:07 PM
While lordsutch's point about Oceanian roundabouts being more like US ones than British ones is a good one - though these rules don't disagree with the NZ or NSW ones posted above wrt straight on traffic (and I doubt they will much at all with the whole lot) - lets refresh on the rules of the second-lowest (half the rate of the US, despite being infested with roundabouts) road fatalities per distance stats. ...

None of these are exemplary, but they do they job. I'd argue that the key issue in the US isn't design or geometry or whatever, but driver miseducation: the Aus/NZ stuff that lordsutch brought in (and brought up that UK roundabouts are slightly different) still seem to follow the same rules of the road, despite their different design.

Small correction: the Australia and New Zealand examples were brought up by jakeroot, not me.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 08, 2017, 08:24:51 AM
More roundabout rules for Indiana drivers.  Most modern roundabouts do have truck aprons but they serve no purpose for trucks navigating the outer lane of a multi-lane roundabout.  In that instance, their trailer is going to encroach on the adjacent lane of traffic and potentially cause a sideswipe crash. 

Quote
Indiana lawmakers move to re-write roundabout rules

Some big rigs–as in semi-trucks–are having big problems getting through roundabouts. The proposed solution calls for giving tractor trailer trucks indisputable right of way rights in roundabouts.

According to the Indiana State Police there were 92 accidents involving semi-trucks in roundabouts in 2016 and only one produced personal injury. Those in support of HB1039 suggest that the rest were the kind of minor fender benders that are becoming more and more common.

http://www.wndu.com/content/news/semis-Passenger-vehicles-could-take-a-back-seat-in-Indiana-roundabout-rules-rewrite-415615193.html
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on March 08, 2017, 08:43:51 AM
While lordsutch's point about Oceanian roundabouts being more like US ones than British ones is a good one - though these rules don't disagree with the NZ or NSW ones posted above wrt straight on traffic (and I doubt they will much at all with the whole lot) - lets refresh on the rules of the second-lowest (half the rate of the US, despite being infested with roundabouts) road fatalities per distance stats.
Quote from: The Highway Code (https://www.gov.uk/guidance/the-highway-code/using-the-road-159-to-203)
Rule 184
On approaching a roundabout take notice and act on all the information available to you, including traffic signs, traffic lights and lane markings which direct you into the correct lane. You should
  • use Mirrors — Signal — Manoeuvre at all stages
    decide as early as possible which exit you need to take
  • give an appropriate signal (see Rule 186, below). Time your signals so as not to confuse other road users
  • get into the correct lane
  • adjust your speed and position to fit in with traffic conditions
  • be aware of the speed and position of all the road users around you.
Rule 185
When reaching the roundabout you should
  • give priority to traffic approaching from your right, unless directed otherwise by signs, road markings or traffic lights
  • check whether road markings allow you to enter the roundabout without giving way. If so, proceed, but still look to the right before joining
  • watch out for all other road users already on the roundabout; be aware they may not be signalling correctly or at all
  • look forward before moving off to make sure traffic in front has moved off.
(https://assets.digital.cabinet-office.gov.uk/media/559af891e5274a155c00001d/the-highway-code-rule-185.jpg)
Rule 185: Follow the correct procedure at roundabouts

Rule 186
Signals and position. When taking the first exit to the left, unless signs or markings indicate otherwise
  • signal left and approach in the left-hand lane
  • keep to the left on the roundabout and continue signalling left to leave.
When taking an exit to the right or going full circle, unless signs or markings indicate otherwise
  • signal right and approach in the right-hand lane
  • keep to the right on the roundabout until you need to change lanes to exit the roundabout
  • signal left after you have passed the exit before the one you want.
When taking any intermediate exit, unless signs or markings indicate otherwise
  • select the appropriate lane on approach to and on the roundabout
  • you should not normally need to signal on approach
  • stay in this lane until you need to alter course to exit the roundabout
  • signal left after you have passed the exit before the one you want.
When there are more than three lanes at the entrance to a roundabout, use the most appropriate lane on approach and through it.

Rule 187
In all cases watch out for and give plenty of room to
  • pedestrians who may be crossing the approach and exit roads
  • traffic crossing in front of you on the roundabout, especially vehicles intending to leave by the next exit
  • traffic which may be straddling lanes or positioned incorrectly
  • motorcyclists
  • cyclists and horse riders who may stay in the left-hand lane and signal right if they intend to continue round the roundabout. Allow them to do so
  • long vehicles (including those towing trailers). These might have to take a different course or straddle lanes either approaching or on the roundabout because of their length. Watch out for their signals.

I make that 32 times it says signal. The real roundabout experts are clear: Joe Gustafson is a dangerous quack who doesn't deserve to be considered a roundabout expert.


And it looks like we're talking about somewhat different things here. It was mentioned that UK has somewhat different design.
So, if you don't mind - can you show some exemplary UK roundabout on a map? Not biggest and greatest, but regular ones with best possible design from your perspective?.
The artists impression in the above picture is a perfectly typical UK roundabout design. This one picked at random (https://www.google.co.uk/maps/@54.609657,-3.1409292,394m/data=!3m1!1e3) might not be best possible design, but it is perfectly acceptable roundabout. Have another random one (https://www.google.co.uk/maps/@53.3441525,0.0039724,357m/data=!3m1!1e3), this time a county council one. The speed limit on all the arms is 60mph (hence the different surface on approach). How about a smaller one (https://www.google.co.uk/maps/@51.5718578,-1.7708922,454a,20y,22.79h/data=!3m1!1e3) - this one (again somewhat randomly picked) is more US in feel nowadays, with non-circulatory lane markings (https://www.google.co.uk/maps/@51.5718059,-1.7712906,3a,75y,16.77h,86.95t/data=!3m6!1e1!3m4!1sPTYuTVFLo-ZZLl7hafToLQ!2e0!7i13312!8i6656) and such like (the aerial view and the more-recent streetview are different: the red area is gone) - but the same rules of signalling are involved.

None of these are exemplary, but they do they job. I'd argue that the key issue in the US isn't design or geometry or whatever, but driver miseducation: the Aus/NZ stuff that lordsutch brought in (and brought up that UK roundabouts are slightly different) still seem to follow the same rules of the road, despite their different design.

The picture is more like a Jersey Traffic Circle, where there can be multiple lanes entering a circle, but no lane markings within the circle.

However, Jersey traffic circles don't have anywhere near the number of rules posted here.  In fact, there aren't really any rules!  Basic guidelines apply...if there's a yield sign, you have to yield, etc.  But otherwise there aren't any official rules for Jersey traffic circles!
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 08, 2017, 10:55:24 AM
The picture is more like a Jersey Traffic Circle, where there can be multiple lanes entering a circle, but no lane markings within the circle.

However, Jersey traffic circles don't have anywhere near the number of rules posted here.  In fact, there aren't really any rules!  Basic guidelines apply...if there's a yield sign, you have to yield, etc.  But otherwise there aren't any official rules for Jersey traffic circles!
Well, I guess ongoing confusion of traffic circle vs modern roundabout is also part of it.
My impression is that roundabout should be able to handle more traffic than circle - although not as much as some planner think it should.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on March 08, 2017, 10:57:36 AM
My impression is that roundabout should be able to handle more traffic than circle - although not as much as some planner think it should.

I don't actually recall having read that claim about modern roundabouts, but that's certainly not to say it hasn't been claimed.  All I've read claimed in modern roundabout versus larger traffic circle has been about safety.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on March 08, 2017, 11:03:56 AM
The picture is more like a Jersey Traffic Circle, where there can be multiple lanes entering a circle, but no lane markings within the circle.

However, Jersey traffic circles don't have anywhere near the number of rules posted here.  In fact, there aren't really any rules!  Basic guidelines apply...if there's a yield sign, you have to yield, etc.  But otherwise there aren't any official rules for Jersey traffic circles!
Well, I guess ongoing confusion of traffic circle vs modern roundabout is also part of it.
My impression is that roundabout should be able to handle more traffic than circle - although not as much as some planner think it should.

I think it's been said a roundabout should be able to handle more traffic than a standard intersection.  Circles are rare so there's very little to compare with.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 08, 2017, 11:16:51 AM
The picture is more like a Jersey Traffic Circle, where there can be multiple lanes entering a circle, but no lane markings within the circle.

However, Jersey traffic circles don't have anywhere near the number of rules posted here.  In fact, there aren't really any rules!  Basic guidelines apply...if there's a yield sign, you have to yield, etc.  But otherwise there aren't any official rules for Jersey traffic circles!
Well, I guess ongoing confusion of traffic circle vs modern roundabout is also part of it.
My impression is that roundabout should be able to handle more traffic than circle - although not as much as some planner think it should.

I think it's been said a roundabout should be able to handle more traffic than a standard intersection.  Circles are rare so there's very little to compare with.

There is a distinction between it's been said they should be able and they are. I can throw word safely into the mix to make things worse.
As for circles, per our UK friend there should be an ample stash of data overseas..
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 13, 2017, 08:22:57 AM
A bunch of triple-lane roundabouts are opening to traffic along Franklin Blvd in Cambridge, Ontario.  Based on the performance of other roundabouts in the region i doubt these will work out too well.  But i just love Marilyn Gummerson honesty lol

"I hate them.  They're useless.  Most people do not even know how to use a roundabout properly... me included".

http://kitchener.ctvnews.ca/mixed-reviews-in-early-days-of-franklin-boulevard-roundabouts-1.3065887

Data is now coming in for the roundabouts on Franklin Boulevard.  The triple lane roundabout at Franklin Blvd and Pinebush has had 49 accidents in the first 3 months of operations.  Compare that to the accident prone Homer Watson & Block Line Road roundabout which had 34 accidents in the first 3 months of operations when it opened back in 2011. 

Quote
Crashes plague Cambridge’s biggest roundabout

CAMBRIDGE – Cambridge's biggest roundabout opened to 49 fender-benders in its first three months. That's far more collisions than the launch of a notorious Kitchener roundabout that's since become the most dangerous road in the region.

The Pinebush traffic circle opened Sept, 14, 2016. An analysis by The Record reveals 49 collisions in 109 days through Dec. 31, 2016.

This compares to 34 collisions between Sept. 14 and Dec. 31, 2011, during the launch of the troubled roundabout at Homer Watson Boulevard and Block Line Road in Kitchener.

The Homer Watson roundabout has defeated tweaks meant to make it safer, including changes to speed limits, lanes, paint, and signs. It's now rated the region's most dangerous road, requiring crossing guards to help St. Mary's High School students get across it. Planners contend the problem is not its design, but older drivers who don't know how to yield.

The Pinebush circle opened with three lanes like the Homer Watson roundabout. Planners later dropped the third lane at Homer Watson, concerned it's too confusing.
http://www.therecord.com/news-story/7186456-crashes-plague-cambridge-s-biggest-roundabout/
Title: Re: Crash prone 'modern roundabouts'
Post by: doorknob60 on March 30, 2017, 04:43:02 PM
In my drivers ed course in Bend, OR (a place pretty familiar with roundabouts, to say the least), we were taught to always signal right before exiting the roundabout. If you're turning right, you can signal before entering. Left signal should not be used (as was taught; a lot of people like my Dad left signaled to indicate he wasn't exiting which in my opinion is okay, but we were taught it wasn't necessary so I stick with that), and you should never not signal an exit.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on March 30, 2017, 06:16:27 PM
One problem with that rule is when the inside lane also can exit the roundabout.  So, if you turn on your signal, people may think you're moving over! :D
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 04, 2017, 08:46:52 PM
According to a recently published Detroit Free Press article, the roundabout at 14 Mile and Orchard Lake had the highest number of accidents in Michigan in 2016.  There were 163 total crashes at the roundabout including 27 injury crashes.  This is the third consecutive year where a roundabout has earned the title for the most crash-prone intersection in Michigan. 

14-Orchard roundabout is tops for accidents, but is it really dangerous?
http://www.freep.com/story/news/local/michigan/oakland/2017/04/04/orchard-roundabout-tops-accidents-really-dangerous/100046220/

(http://www.mtjengineering.com/wp-content/uploads/2014/10/OLR-3.jpg)


Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 04, 2017, 09:24:01 PM
^^ I don't see the significance of a high number of collisions. If no one is seriously hurt or killed, it's a win. According to the article, there weren't any at this roundabout (and only 16% of collisions even resulted in injuries).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 04, 2017, 11:43:57 PM
Take a look at the pre-roundabout crash data for 14 Mile and Orchard Lake (roundabout constructed in 2015).  From 2011-2014 the intersection averaged 49 total crashes and 9.5 injury crashes.  In the first year of operations, the roundabout has seen a 232% increase in total crashes (from 49 to 163) and a 184% increase in injury crashes (from 9.5 to 27).

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/untitled232_zps21amc2ug.png)
http://semcog.org/Data-and-Maps/High-Frequency-Crash-Locations/Point_Id/63052513/view/RoadIntersectionCrashDetail

Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on April 17, 2017, 09:57:40 AM
Quote
Carmel to require turn signals in roundabouts

Ever get frustrated trying to figure out when vehicles will exit a roundabout?

The Carmel City Council will consider an ordinance Monday to require people to use their turn signals to make it clear. Scofflaws will face a $100 fine.

"This is standard in countries with many roundabouts and allows a driver waiting to enter a roundabout to know whether a circulating car is going to cross in front or turn out of the circle," said Mayor Jim Brainard. "It will speed up our roundabouts and make them more efficient."

http://www.indystar.com/story/news/local/hamilton-county/2017/03/06/carmel-require-turn-signals-roundabouts/98686674/

There are roundabout experts who say drivers shouldn’t signal when exiting a roundabout.  In a roundabout webinar hosted by the University of Minnesota, Joe Gustafson from Washington County stated the following:

“We also would never tell a driver to use a right turn signal to exit a roundabout.  Again, that’s a through movement and we don’t want to create the impression that it’s a right turn.”  

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/CIC-COM-1129-100-Roundabouts-2-720x540_zpsywnfurwvyellow_zpsxupqlvhm.jpg)

Here’s an aerial of the new Rangeline Road and Carmel Drive roundabout.  Should the driver in the yellow path be required to signal when exiting the roundabout?  At no point do the pavement markings or signage indicate the driver is making a right turn.  There’s a straight arrow inside the roundabout.  It doesn’t make sense to require drivers to use their right turn signal indication as they are driving overtop a “straight only”  arrow.  It is confusing.

Logic won the battle:  http://www.indystar.com/story/news/local/hamilton-county/2017/04/17/carmel-nix-idea-turn-signals-roundabouts/100457422/
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 17, 2017, 10:50:43 AM
Quote
Carmel to require turn signals in roundabouts

Ever get frustrated trying to figure out when vehicles will exit a roundabout?

The Carmel City Council will consider an ordinance Monday to require people to use their turn signals to make it clear. Scofflaws will face a $100 fine.

"This is standard in countries with many roundabouts and allows a driver waiting to enter a roundabout to know whether a circulating car is going to cross in front or turn out of the circle," said Mayor Jim Brainard. "It will speed up our roundabouts and make them more efficient."

http://www.indystar.com/story/news/local/hamilton-county/2017/03/06/carmel-require-turn-signals-roundabouts/98686674/

There are roundabout experts who say drivers shouldn’t signal when exiting a roundabout.  In a roundabout webinar hosted by the University of Minnesota, Joe Gustafson from Washington County stated the following:

“We also would never tell a driver to use a right turn signal to exit a roundabout.  Again, that’s a through movement and we don’t want to create the impression that it’s a right turn.”  

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/CIC-COM-1129-100-Roundabouts-2-720x540_zpsywnfurwvyellow_zpsxupqlvhm.jpg)

Here’s an aerial of the new Rangeline Road and Carmel Drive roundabout.  Should the driver in the yellow path be required to signal when exiting the roundabout?  At no point do the pavement markings or signage indicate the driver is making a right turn.  There’s a straight arrow inside the roundabout.  It doesn’t make sense to require drivers to use their right turn signal indication as they are driving overtop a “straight only”  arrow.  It is confusing.

Logic won the battle:  http://www.indystar.com/story/news/local/hamilton-county/2017/04/17/carmel-nix-idea-turn-signals-roundabouts/100457422/

Not yet. Logic would win when those roundabouts finally get bulldozed out of misery.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on April 17, 2017, 11:15:09 AM
Quote
Carmel to require turn signals in roundabouts

Ever get frustrated trying to figure out when vehicles will exit a roundabout?

The Carmel City Council will consider an ordinance Monday to require people to use their turn signals to make it clear. Scofflaws will face a $100 fine.

"This is standard in countries with many roundabouts and allows a driver waiting to enter a roundabout to know whether a circulating car is going to cross in front or turn out of the circle," said Mayor Jim Brainard. "It will speed up our roundabouts and make them more efficient."

http://www.indystar.com/story/news/local/hamilton-county/2017/03/06/carmel-require-turn-signals-roundabouts/98686674/

There are roundabout experts who say drivers shouldn’t signal when exiting a roundabout.  In a roundabout webinar hosted by the University of Minnesota, Joe Gustafson from Washington County stated the following:

“We also would never tell a driver to use a right turn signal to exit a roundabout.  Again, that’s a through movement and we don’t want to create the impression that it’s a right turn.”  

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/CIC-COM-1129-100-Roundabouts-2-720x540_zpsywnfurwvyellow_zpsxupqlvhm.jpg)

Here’s an aerial of the new Rangeline Road and Carmel Drive roundabout.  Should the driver in the yellow path be required to signal when exiting the roundabout?  At no point do the pavement markings or signage indicate the driver is making a right turn.  There’s a straight arrow inside the roundabout.  It doesn’t make sense to require drivers to use their right turn signal indication as they are driving overtop a “straight only”  arrow.  It is confusing.

Logic won the battle:  http://www.indystar.com/story/news/local/hamilton-county/2017/04/17/carmel-nix-idea-turn-signals-roundabouts/100457422/

Not yet. Logic would win when those roundabouts finally get bulldozed out of misery.

Nobody in misery here.   We enjoy being able to travel without unneeded backups from obsolete traffic lights and 4 way stops.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 19, 2017, 03:36:50 PM
Nobody in misery here.   We enjoy being able to travel without unneeded backups from obsolete traffic lights and 4 way stops.

CJW2001, here’s a challenge for you.  Take a video driving 20 miles through the roundabouts of Carmel and let's see how long it takes you.  Here’s a 20 mile drive through the traffic lights of Detroit (averaged 46 mph over 20 miles).  Just imagine if every traffic signal in the video was a roundabout and how much longer it would take to drive. 

Title: Re: Crash prone 'modern roundabouts'
Post by: tdindy88 on April 19, 2017, 04:24:34 PM
There are no roads in Carmel that could compare to Woodward Avenue. There is simply no comparison, people are not traveling through Carmel like they would on some of the long boulevards of Detroit with Michigan lefts. And while I am personally one to think that the roundabouts planned for 96th Street between Keystone and the White River are a bad idea I do know that roundabouts do work if they are placed properly. I live near one of the few roundabouts in Indianapolis proper, Edgewood Avenue and Gray Road. A former four-way stop sign on two two-lane roads was reconstructed as a one-lane roundabout and it has done wonders for the traffic there. I used to remember backups of 15+ cars at rush hour in various directions approaching the stop sign intersection. Those are now a thing of the past. But as I see it, the roundabout was perfect in THIS location. It functions well for the two class of roads it serves.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 19, 2017, 04:29:11 PM
There are no roads in Carmel that could compare to Woodward Avenue. There is simply no comparison, people are not traveling through Carmel like they would on some of the long boulevards of Detroit with Michigan lefts. And while I am personally one to think that the roundabouts planned for 96th Street between Keystone and the White River are a bad idea I do know that roundabouts do work if they are placed properly. I live near one of the few roundabouts in Indianapolis proper, Edgewood Avenue and Gray Road. A former four-way stop sign on two two-lane roads was reconstructed as a one-lane roundabout and it has done wonders for the traffic there. I used to remember backups of 15+ cars at rush hour in various directions approaching the stop sign intersection. Those are now a thing of the past. But as I see it, the roundabout was perfect in THIS location. It functions well for the two class of roads it serves.
That is the point - roundabouts are NOT universal solution, as they are being sold. And looks like nobody knows - and nobody WANTS to know - what is the proper niche for them. Just sign those damn checks!
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on April 19, 2017, 04:38:27 PM
No one is saying that roundabouts are a universal solution, but you seem to be saying that all roundabouts are intrinsically evil.

Take a look at this route https://www.google.com/maps/dir/39.9232311,-86.1121404/40.0648746,-86.1262864/@39.9712591,-86.0688241,12.25z going from 96th and Keystone Parkway northward through Carmel and on through Westfield.    Almost every interchange along this route has roundabout intersections, but the through traffic passes under or over the roundabouts.   This is intelligent usage of roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 19, 2017, 04:39:14 PM
There are no roads in Carmel that could compare to Woodward Avenue. There is simply no comparison, people are not traveling through Carmel like they would on some of the long boulevards of Detroit with Michigan lefts. And while I am personally one to think that the roundabouts planned for 96th Street between Keystone and the White River are a bad idea I do know that roundabouts do work if they are placed properly. I live near one of the few roundabouts in Indianapolis proper, Edgewood Avenue and Gray Road. A former four-way stop sign on two two-lane roads was reconstructed as a one-lane roundabout and it has done wonders for the traffic there. I used to remember backups of 15+ cars at rush hour in various directions approaching the stop sign intersection. Those are now a thing of the past. But as I see it, the roundabout was perfect in THIS location. It functions well for the two class of roads it serves.

That is the point - roundabouts are NOT universal solution, as they are being sold. And looks like nobody knows - and nobody WANTS to know - what is the proper niche for them. Just sign those damn checks!

Michigan lefts are also not a universal solution. They require gigantic ROW throughout the length of the route. At least roundabouts only require wide ROW at junctions.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 19, 2017, 04:41:22 PM
No one is saying that roundabouts are a universal solution, but you seem to be saying that all roundabouts are intrinsically evil.
I am saying that thoughtless design of anything is evil.  Most, if not all, roundabouts I see around do fall into that category. 
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on April 19, 2017, 04:47:29 PM
Carmel does a far better job on their roundabout design than most places.   Having lived here in the pre roundabout era and the post roundabout era I can say that traffic is far far better today than in the past.   There are another 30 roundabouts on the way  and very much looking forward to it.  http://carmellink.com/

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 19, 2017, 05:01:54 PM
No one is saying that roundabouts are a universal solution, but you seem to be saying that all roundabouts are intrinsically evil.

I am saying that thoughtless design of anything is evil.  Most, if not all, roundabouts I see around do fall into that category.

Not really thoughtless design. Most (all?) are designed to MUTCD standards. Never mind that no comprehensive studies have ever come out that steadfastly show multi-lane roundabouts to be not-as-great as we previously thought. There have been seminars, small studies, presentations, etc that have presented the idea of multi-lane roundabouts having more than their fair share of collisions, but there's never been anything thorough before.

I understand that the FHWA based a lot of current roundabout rhetoric off old, small studies. But trying to refute those studies with an equally small study doesn't prove anything (except that small studies can often be engineered to reflect the desired outcome of the author).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 19, 2017, 05:10:03 PM
No one is saying that roundabouts are a universal solution, but you seem to be saying that all roundabouts are intrinsically evil.

I am saying that thoughtless design of anything is evil.  Most, if not all, roundabouts I see around do fall into that category.

Not really thoughtless design. Most (all?) are designed to MUTCD standards. Never mind that no comprehensive studies have ever come out that steadfastly show multi-lane roundabouts to be not-as-great as we previously thought. There have been seminars, small studies, presentations, etc that have presented the idea of multi-lane roundabouts having more than their fair share of collisions, but there's never been anything thorough before.

I understand that the FHWA based a lot of current roundabout rhetoric off old, small studies. But trying to refute those studies with an equally small study doesn't prove anything (except that small studies can often be engineered to reflect the desired outcome of the author).

As far as I remember earlier posts in this thread, you're now infected with my skepticism...  :hmmm:
Yes, that is pretty much the point - building without looking back.  Road standards, by their nature, are not set in stone or asphalt, they have to adapt. Quite often you can say you're on an old road just by driving it.  And "we just follow MUTCD" is not a good excuse for not learning on past experience.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on April 19, 2017, 05:16:28 PM
No one is saying that roundabouts are a universal solution, but you seem to be saying that all roundabouts are intrinsically evil.

I am saying that thoughtless design of anything is evil.  Most, if not all, roundabouts I see around do fall into that category.

Not really thoughtless design. Most (all?) are designed to MUTCD standards. Never mind that no comprehensive studies have ever come out that steadfastly show multi-lane roundabouts to be not-as-great as we previously thought. There have been seminars, small studies, presentations, etc that have presented the idea of multi-lane roundabouts having more than their fair share of collisions, but there's never been anything thorough before.

I understand that the FHWA based a lot of current roundabout rhetoric off old, small studies. But trying to refute those studies with an equally small study doesn't prove anything (except that small studies can often be engineered to reflect the desired outcome of the author).

FIFY. The MUTCD doesn't govern roundabout design. The MUTCD only provides suggested marking and signing layouts for roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 19, 2017, 05:23:19 PM
No one is saying that roundabouts are a universal solution, but you seem to be saying that all roundabouts are intrinsically evil.

I am saying that thoughtless design of anything is evil.  Most, if not all, roundabouts I see around do fall into that category.

Not really thoughtless design. Most (all?) are designed to MUTCD standards. Never mind that no comprehensive studies have ever come out that steadfastly show multi-lane roundabouts to be not-as-great as we previously thought. There have been seminars, small studies, presentations, etc that have presented the idea of multi-lane roundabouts having more than their fair share of collisions, but there's never been anything thorough before.

I understand that the FHWA based a lot of current roundabout rhetoric off old, small studies. But trying to refute those studies with an equally small study doesn't prove anything (except that small studies can often be engineered to reflect the desired outcome of the author).

As far as I remember earlier posts in this thread, you're now infected with my skepticism...  :hmmm:
Yes, that is pretty much the point - building without looking back.  Road standards, by their nature, are not set in stone or asphalt, they have to adapt. Quite often you can say you're on an old road just by driving it.  And "we just follow MUTCD" is not a good excuse for not learning on past experience.

I am skeptical of large roundabouts, yes. I'm just not as worried as Trade is. A lot of the small studies that I've seen seem to show that, while collisions are on the rise, every other aspect of junction safety is on the decline (not true at all roundabouts, though).

The MUTCD doesn't govern roundabout design. The MUTCD only provides suggested marking and signing layouts for roundabouts.

Good to know. I thought the MUTCD was more thorough. Do individual states provide roundabout engineering standards?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 20, 2017, 12:01:22 PM
Take a look at this route https://www.google.com/maps/dir/39.9232311,-86.1121404/40.0648746,-86.1262864/@39.9712591,-86.0688241,12.25z going from 96th and Keystone Parkway northward through Carmel and on through Westfield.    Almost every interchange along this route has roundabout intersections, but the through traffic passes under or over the roundabouts.   This is intelligent usage of roundabouts.

The most intelligent roundabout is one where drivers don’t have to drive through it?  We are starting to agree!  Although I'll point out that the roundabout at 116th & Keystone Parkway has a horrendous crash rate.  According to the Carmel Police Department Annual Reports, the 116th and Keystone roundabout averaged 64.3 crashes a year from 2011-2014 and had an AADT of 20,463.  That equates to a crash rate of 8.7 MEV which is over 4x higher than 2.0 MEV (what many agencies consider a ”˜critical’ crash rate that warrants further investigation).  In addition, the city added a traffic signal at the 136th Street and Keystone Parkway roundabout to address the traffic snarls that would occur at that roundabout during heavy rushes.   

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Carmel116thKeystone_zpsmcrormht.png)

I don’t see how roundabouts with horrendous crash rates and ones that require traffic signals to function properly could be considered “intelligent” .  Not to mention, the through traffic along Keystone Parkway totally bypasses the roundabouts.  Imagine the cluster that would occur if Keystone Parkway wasn't grade separated.  Roundabouts wouldn't have even been an option.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on April 20, 2017, 03:01:42 PM
The ramp meters at 136 and keystone only operate a few minutes a day on demand as triggered by traffic sensors, during the sudden rush brought on by 5000+ students arriving or leaving the state's largest high school (http://www.indystar.com/story/news/local/hamilton-county/2017/04/19/peek-into-1-million-square-foot-carmel-high-school/100427706/) all at the same time.   The vast majority of the day it operates as a normal roundabout.   That's an intelligent solution that only invokes the ramp meters as needed.

I'll take the traffic throughput  of the roundabout at 116th and Keystone any day over the stop light it replaced.  Yes there may be more minor fender benders as compared to a stoplight (it's hard to run into other people when stuck in gridlock) but traffic flows well without backups.  There is no way we would want to go back to the previous intersection.  I don't define the success of the intersection based on the number of fender benders, I define it based on the smooth traffic flow that we have today.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 20, 2017, 03:35:41 PM
Carmel does a far better job on their roundabout design than most places.   Having lived here in the pre roundabout era and the post roundabout era I can say that traffic is far far better today than in the past.   There are another 30 roundabouts on the way  and very much looking forward to it.  http://carmellink.com/

Much of the improved traffic flow is a result of grade-separating the city's heaviest traveled routes.  You can’t credit roundabouts for the improved flow along Keystone Parkway and Meridian Street.  Of the heavily traveled surface-streets that haven't been grade-separated, most are void of roundabouts.  You just don’t encounter a roundabout every intersection as you drive down Rangeline Road, 96th Street or 116th Street.  But that’s all about to change.  If you look at the link provided by cjw2001, 18 of the 30 upcoming roundabouts are being constructed along these major routes.  While Carmel has been conservative in their roundabout design in the past, they are finally jumping in head first and building more complex roundabouts along the heaviest traveled roadways.

CJW2001, did they finish constructing the 96th and Gray Road roundabout?  To the best of my knowledge, this is the first roundabout in Carmel that has three circulating lanes of traffic. Roundabouts with triple circulating lanes are the type of roundabouts that win awards... specifically most crashes in the state awards.  I'm sure you would be proud if Carmel could win such a prestigious award!   
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on April 20, 2017, 09:11:01 PM
96th and Gray will be summer 2017
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 21, 2017, 12:37:40 PM
96th and Gray will be summer 2017

Thanks for the info.  Since Carmel will be constructing their first triple-lane roundabout this year it might be wise to consider how triple-lane roundabouts have performed in other parts of the country.  Over the past ten years, Wisconsin has constructed about 20 triple-lane roundabouts and not surprisingly many have exceedingly high crash rates.  The international roundabout conference is taking place in Green Bay this year so we might hear more about these “triple-laners” .  But to the best of my knowledge, all but one district in Wisconsin has placed a moratorium on designing triple-lane roundabouts moving forward.  It's telling when an agency with the most experience building triple-lane roundabouts places a moratorium on them.    Wisconsin has spent ten years tested the limitations of roundabouts and they seemingly concluded that “triple laners”  are too much. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 21, 2017, 12:44:13 PM
I wonder if a three-lane turbo roundabout would see lower crash rates.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 21, 2017, 03:46:00 PM
Car shoots through roundabout and over bluff at Bachman Tunnel
http://wdef.com/2017/04/21/car-shoots-roundabout-bluff-bachman-tunnel/

Early this morning a driver failed to make a turn at the Bluffman Tunnel roundabout in Chattanooga and plunged 50 feet down a cliff.  The passenger is in critical condition.   Looking at historical imagery and streetview, this isn’t the first time a driver hit the guardrail on the other side of the roundabout.  Exhibit A in the upcoming lawsuit:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/DamagedGuardrail4_zpsmhlow9pi.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 21, 2017, 05:21:44 PM
^^ There doesn't seem to be much (if any) warning of the impending roundabout. A blinking overhead W2-6 may be in order.

The only sign seems to be this one before the tunnel, which is only half correct:

(http://i.imgur.com/1pHScDc.png)

*also, Bluffman tunnel? :-D
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 21, 2017, 06:16:18 PM
What does this have to do with the intersection being a roundabout?
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on April 21, 2017, 08:02:13 PM
^^ There doesn't seem to be much (if any) warning of the impending roundabout. A blinking overhead W2-6 may be in order.

The only sign seems to be this one before the tunnel, which is only half correct:

(http://i.imgur.com/1pHScDc.png)

*also, Bluffman tunnel? :-D

There's also a large overhead 'Yield ahead at end of tunnel' with blinking lights sign prior to these signs. Not to mention what appears to be a slow speed tunnel and a pretty good Yield sign at the end of the tunnel.

What the issue probably was is some kid who decided to speed way too fast they the tunnel and couldn't slow down in time.

Sometimes, you just have to chalk things up to driver stupidity.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 21, 2017, 08:31:09 PM
What does this have to do with the intersection being a roundabout?

Actually that's a good point. The intersection is still T-shaped. Roundabout or not, going over that bluff is inevitable if one is going too quickly.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on April 22, 2017, 05:09:51 AM
What does this have to do with the intersection being a roundabout?
I'd argue that it is somewhat relevant as, ignoring jeffandnicole's comments about the reality, it is part of the "engineers are often terrible at providing decent information to drivers" and "drivers are often stupid" problems that seems to be sustaining this thread.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 22, 2017, 05:55:28 AM
What does this have to do with the intersection being a roundabout?
I'd argue that it is somewhat relevant as, ignoring jeffandnicole's comments about the reality, it is part of the "engineers are often terrible at providing decent information to drivers" and "drivers are often stupid" problems that seems to be sustaining this thread.
I would add "intentionally obscuring the view, as required per roundabout concept"

Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on April 22, 2017, 09:33:08 PM
Car shoots through roundabout and over bluff at Bachman Tunnel
http://wdef.com/2017/04/21/car-shoots-roundabout-bluff-bachman-tunnel/

Early this morning a driver failed to make a turn at the Bluffman Tunnel roundabout in Chattanooga and plunged 50 feet down a cliff.  The passenger is in critical condition.   Looking at historical imagery and streetview, this isn’t the first time a driver hit the guardrail on the other side of the roundabout.  Exhibit A in the upcoming lawsuit:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/DamagedGuardrail4_zpsmhlow9pi.png)


Since Trade has a tendency to provide only half the story...here's a possible reason those guardrail dents are there: http://wdef.com/2016/07/20/cascades-motel-robbery-suspect-crashes-chattanooga-chase/  Apparently, leading police on a high speed chase and hitting another car is now a fault of a roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on April 22, 2017, 10:15:05 PM
Apparently, leading police on a high speed chase and hitting another car is now a fault of a roundabout.

Idiots will always be idiots, there's no helping that.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 22, 2017, 11:43:12 PM
Car shoots through roundabout and over bluff at Bachman Tunnel
http://wdef.com/2017/04/21/car-shoots-roundabout-bluff-bachman-tunnel/

Early this morning a driver failed to make a turn at the Bluffman Tunnel roundabout in Chattanooga and plunged 50 feet down a cliff.  The passenger is in critical condition.   Looking at historical imagery and streetview, this isn’t the first time a driver hit the guardrail on the other side of the roundabout.  Exhibit A in the upcoming lawsuit:



Since Trade has a tendency to provide only half the story...here's a possible reason those guardrail dents are there: http://wdef.com/2016/07/20/cascades-motel-robbery-suspect-crashes-chattanooga-chase/  Apparently, leading police on a high speed chase and hitting another car is now a fault of a roundabout.
From the look of those guardrails, looks like they have daily police chases in the area.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 24, 2017, 10:02:06 AM
Maybe it was an epic multi-year police chase ;).  The roundabout crash is relevant in that it dispels the whole premise of why roundabouts are safer.  Just read what the Insurance Institute for Highway Safety website says…

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/IIHS_zpsu4sxkw2e.png)

A driver blowing through a roundabout and flying 50 feet over a cliff is evidence that roundabouts don’t force drivers to slow down.  With their logic I could make the argument that traffic signals are safer than roundabouts because red lights force drivers to stop - at roundabouts you merely slow down.   If they can’t even get the premise right, why would anyone believe their dubious claim that roundabouts reduce fatal crashes by 90%? 
Title: Re: Crash prone 'modern roundabouts'
Post by: Brian556 on April 24, 2017, 10:24:26 AM
The accidents at the Bachman Tunnel roundabout that are being described here would happen whether the roundabout was there or not.

They are happening because there is a T-junction/sharp turn after the tunnel, and people are stupid and don't read signs.

That roundabout wasn't always there. I'd be willing to bet the accidents were happening long before the roundabout was installed
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 24, 2017, 10:45:50 AM
The accidents at the Bachman Tunnel roundabout that are being described here would happen whether the roundabout was there or not.

They are happening because there is a T-junction/sharp turn after the tunnel, and people are stupid and don't read signs.

That roundabout wasn't always there. I'd be willing to bet the accidents were happening long before the roundabout was installed
I would say that money ($1M or so I suspect) were just lost here. Roundabout was apparently built as a way to eliminate accidents - but equally apparently fails.
I have hard time finding location on the map, but from the look of posted mapshots I suspect that there is no power readily available at the location - i.e. no traffic lights or flashing warnings.
Maybe it would make more sense to spend money either running power line, or installing solar array + batteries to power some more aggressive warning signals?
And if that is more or less the case - this is exactly what I am complaining about - thoughtless building of roundabouts under flawed assumptions of "it solves all problems"

UPD: taking power available portion back. Apparently power is available, so illuminated signs probably just don't result in attractive enough contracts...
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on April 24, 2017, 01:28:30 PM
A driver blowing through a roundabout and flying 50 feet over a cliff is evidence that roundabouts don’t force drivers to slow down.  With their logic I could make the argument that traffic signals are safer than roundabouts because red lights force drivers to stop - at roundabouts you merely slow down.   If they can’t even get the premise right, why would anyone believe their dubious claim that roundabouts reduce fatal crashes by 90%? 

Now you're just being silly. For example, road diets are designed to slow drivers down because drivers generally drive slower in narrower lanes (9' to 11' lanes rather than 12'+), with closer curbs, etc. Yet there's no physical impediment to using a dieted road as a drag strip, so I guess road diets don't actually work.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 24, 2017, 01:44:01 PM
A driver blowing through a roundabout and flying 50 feet over a cliff is evidence that roundabouts don’t force drivers to slow down.  With their logic I could make the argument that traffic signals are safer than roundabouts because red lights force drivers to stop - at roundabouts you merely slow down.   If they can’t even get the premise right, why would anyone believe their dubious claim that roundabouts reduce fatal crashes by 90%? 

Now you're just being silly. For example, road diets are designed to slow drivers down because drivers generally drive slower in narrower lanes (9' to 11' lanes rather than 12'+), with closer curbs, etc. Yet there's no physical impediment to using a dieted road as a drag strip, so I guess road diets don't actually work.

As I said multiple times, the root cause problem is quality of engineering personnel.
Roads are designed for average Joe. Maybe for 80 years old aunt Mary and her husband who is still driving. For those college kids who have more hormones than brains. And roads MUST be designed with them in mind.
If it was about designing NASCAR track, requirements may be different. But there is a clear sign of accident pattern observable in that area - even on google maps.
That is design problem.
That is engineering problem.
In private company such performance failure would be a reason for firing, plain and simple.
 
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on April 24, 2017, 02:11:06 PM
A driver blowing through a roundabout and flying 50 feet over a cliff is evidence that roundabouts don’t force drivers to slow down.  With their logic I could make the argument that traffic signals are safer than roundabouts because red lights force drivers to stop - at roundabouts you merely slow down.   If they can’t even get the premise right, why would anyone believe their dubious claim that roundabouts reduce fatal crashes by 90%? 

Now you're just being silly. For example, road diets are designed to slow drivers down because drivers generally drive slower in narrower lanes (9' to 11' lanes rather than 12'+), with closer curbs, etc. Yet there's no physical impediment to using a dieted road as a drag strip, so I guess road diets don't actually work.

As I said multiple times, the root cause problem is quality of engineering personnel.
Roads are designed for average Joe. Maybe for 80 years old aunt Mary and her husband who is still driving. For those college kids who have more hormones than brains. And roads MUST be designed with them in mind.
If it was about designing NASCAR track, requirements may be different. But there is a clear sign of accident pattern observable in that area - even on google maps.
That is design problem.
That is engineering problem.
In private company such performance failure would be a reason for firing, plain and simple.
 

How did those accidents happen with the guardrail?

If there was 3 separate accidents, and 3 different causes, what was the design problem?

What if an accident was caused by a deer running thru the roundabout?  Or someone blew a tire?  The guardrail SAVED their lives.  Simply because a guardrail was hit doesn't mean there's a design problem.  On the contrary, the guardrail was designed properly.

By your and Trade's logic, we should never have guardrails anywhere ever, because that reveals a design problem when hit.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 24, 2017, 02:25:31 PM
Now you're just being silly. For example, road diets are designed to slow drivers down because drivers generally drive slower in narrower lanes (9' to 11' lanes rather than 12'+), with closer curbs, etc. Yet there's no physical impediment to using a dieted road as a drag strip, so I guess road diets don't actually work.

It’s one thing to say roundabouts are designed to slow drivers down.   But that’s not what the Insurance Institute for Highway Safety is claiming.  On their main website they state that the tight circle of a roundabout “forces”  drivers to slow down.  There is a distinction there.  This woman in Britain wasn’t forced to slow down as she approached a roundabout:

http://www.liverpoolecho.co.uk/news/liverpool-news/shocking-video-shows-car-launched-12874854

The IIHS makes a ludicrous claim that is easily disproven by watching a 20 second youtube video.  This is the same agency that has long propagated the myth that roundabouts reduce fatal crashes by 90%.  Their findings come into question when they can't even get a simple statement on their website right.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 24, 2017, 02:36:21 PM
A driver blowing through a roundabout and flying 50 feet over a cliff is evidence that roundabouts don’t force drivers to slow down.  With their logic I could make the argument that traffic signals are safer than roundabouts because red lights force drivers to stop - at roundabouts you merely slow down.   If they can’t even get the premise right, why would anyone believe their dubious claim that roundabouts reduce fatal crashes by 90%? 

Now you're just being silly. For example, road diets are designed to slow drivers down because drivers generally drive slower in narrower lanes (9' to 11' lanes rather than 12'+), with closer curbs, etc. Yet there's no physical impediment to using a dieted road as a drag strip, so I guess road diets don't actually work.

As I said multiple times, the root cause problem is quality of engineering personnel.
Roads are designed for average Joe. Maybe for 80 years old aunt Mary and her husband who is still driving. For those college kids who have more hormones than brains. And roads MUST be designed with them in mind.
If it was about designing NASCAR track, requirements may be different. But there is a clear sign of accident pattern observable in that area - even on google maps.
That is design problem.
That is engineering problem.
In private company such performance failure would be a reason for firing, plain and simple.
 

How did those accidents happen with the guardrail?

If there was 3 separate accidents, and 3 different causes, what was the design problem?

What if an accident was caused by a deer running thru the roundabout?  Or someone blew a tire?  The guardrail SAVED their lives.  Simply because a guardrail was hit doesn't mean there's a design problem.  On the contrary, the guardrail was designed properly.

By your and Trade's logic, we should never have guardrails anywhere ever, because that reveals a design problem when hit.

Well, at least they managed design guardrail. Problem is that it acted not as a backup, which should be used only a few times during life - but pretty much as a primary system, with what appears to be quite frequent collisions. In such situation, it is only a matter of time that a fatal accident... And usually fatal accident is the reason to review situation - so we may hope for the best...
Title: Re: Crash prone 'modern roundabouts'
Post by: Brian556 on April 24, 2017, 02:45:57 PM
Google Map of the location:
https://www.google.com/maps/@35.0097643,-85.2696198,371m/data=!3m1!1e3 (https://www.google.com/maps/@35.0097643,-85.2696198,371m/data=!3m1!1e3)

There is plenty of warning of what comes after the tunnel. The single narrow lane in tunnel encourages low speeds.

The roundabout at he end of the tunnel makes the situation no more dangerous then before it was installed.

I don't see anything particularly unsafe engineering wise that would be the cause of these accidents.

I think the problem here is simply that some people stupid and should not be driving
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 24, 2017, 02:46:03 PM
Maybe it was an epic multi-year police chase ;).  The roundabout crash is relevant in that it dispels the whole premise of why roundabouts are safer.  Just read what the Insurance Institute for Highway Safety website says…

[img width=800 height=679]...

A driver blowing through a roundabout and flying 50 feet over a cliff is evidence that roundabouts don’t force drivers to slow down.  With their logic I could make the argument that traffic signals are safer than roundabouts because red lights force drivers to stop - at roundabouts you merely slow down.   If they can’t even get the premise right, why would anyone believe their dubious claim that roundabouts reduce fatal crashes by 90%? 


Fallacy of equivocation.

"Force" is not intended to mean what you make it out to mean.  A giant center island, landscaping (maybe), curved/flared entries, warning signs (often with flashing warning lights of their own), et cetera certainly do a better job of "forcing" a driver to slow down than a couple of lights hung above an otherwise straightforward intersection.  There are simply more and bigger things for a driver to notice, and there are physical realities that lead any but the most unobservant driver to slow down.  This doesn't mean the spirit of a roundabout inhabits the body of a drive and moves his foot over onto the brake.  But that's not what the word "force" means in the context of the IIHS blurb you posted.

As to your reworking of their logic:  A stoplight is just as likely to make (notice how I use that word in a non-literal sense) a driver speed up as slow down.  Yellow light? speed up!  You can't speed up to beat a red roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 24, 2017, 03:04:50 PM
Google Map of the location:
https://www.google.com/maps/@35.0097643,-85.2696198,371m/data=!3m1!1e3 (https://www.google.com/maps/@35.0097643,-85.2696198,371m/data=!3m1!1e3)

There is plenty of warning of what comes after the tunnel. The single narrow lane in tunnel encourages low speeds.
And since there is still a pattern, it means that there is not enough warning.  I mean, advance signage and and so on. You design for realities of life, not to what you think it should be.

There is obviously a hazard in the way tunnel and street are aligned, no question about that. It takes some effort to design things so that they actually work, not just pass a half-assed review process.
Quote
The roundabout at he end of the tunnel makes the situation no more dangerous then before it was installed.
So spending something like one million dollars TennDOT managed to make things not worse than they were. That is a great achievement, oftentimes it takes billions to achieve same "it wasn't better" result

Quote
I think the problem here is simply that some people stupid and should not be driving
I think some engineers are  stupid and should not be designing things. I also think that is easier to accomplish in terms of affected headcount.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on April 24, 2017, 03:27:46 PM
Google Map of the location:
https://www.google.com/maps/@35.0097643,-85.2696198,371m/data=!3m1!1e3 (https://www.google.com/maps/@35.0097643,-85.2696198,371m/data=!3m1!1e3)

There is plenty of warning of what comes after the tunnel. The single narrow lane in tunnel encourages low speeds.
And since there is still a pattern, it means that there is not enough warning.  I mean, advance signage and and so on. You design for realities of life, not to what you think it should be.

What's the pattern?  How can you tell those guardrail hits all occurred the same way?
Title: Re: Crash prone 'modern roundabouts'
Post by: intelati49 on April 24, 2017, 03:35:25 PM
Google Map of the location:
https://www.google.com/maps/@35.0097643,-85.2696198,371m/data=!3m1!1e3 (https://www.google.com/maps/@35.0097643,-85.2696198,371m/data=!3m1!1e3)

There is plenty of warning of what comes after the tunnel. The single narrow lane in tunnel encourages low speeds.
And since there is still a pattern, it means that there is not enough warning.  I mean, advance signage and and so on. You design for realities of life, not to what you think it should be.

There is obviously a hazard in the way tunnel and street are aligned, no question about that. It takes some effort to design things so that they actually work, not just pass a half-assed review process.
Quote
The roundabout at he end of the tunnel makes the situation no more dangerous then before it was installed.
So spending something like one million dollars TennDOT managed to make things not worse than they were. That is a great achievement, oftentimes it takes billions to achieve same "it wasn't better" result

Quote
I think the problem here is simply that some people stupid and should not be driving
I think some engineers are  stupid and should not be designing things. I also think that is easier to accomplish in terms of affected headcount.


I have no idea what the traffic situation is like here, but safety isn't the only warrant for a intersection change. Capacity is another, and they probably thought they could get more traffic through here.

And I wanted to reply to the last quote with a joke, but I guess a statement will suffice. Nobody wants to pay for a 99.9% safe road (14ft lanes with 1000ft sightlines), so 95% safe roads have to suffice. There's only so much you can do without making the markings a distraction
Title: Re: Crash prone 'modern roundabouts'
Post by: TheArkansasRoadgeek on April 24, 2017, 03:55:50 PM
I love how we resort to the second generation of interchanges to solve a hazardous problem in an intersection. You would think we are pushing forward in transportation engineering not going backward. Weird.
Title: Re: Crash prone 'modern roundabouts'
Post by: intelati49 on April 24, 2017, 03:59:32 PM
I love how we resort to the second generation of interchanges to solve a hazardous problem in an intersection. You would think we are pushing forward in transportation engineering not going backward. Weird.

Hey, the saying "hindsight's 20/20" is for a reason. Sometimes we get so caught up with going forward, we forget the original ideas we had before.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 24, 2017, 04:20:01 PM
I love how we resort to the second generation of interchanges to solve a hazardous problem in an intersection. You would think we are pushing forward in transportation engineering not going backward. Weird.
Ypu're not pushing towards 5th generation antibiotics or GM insulin to treat flu or broken leg.
You need a lot of water and rest -  or cast, respectively.  Both are first generation treatments...

Obsession with advanced design is actually bad - until there is a clear understanding of what are problems of old methods, when they work, and when they don't - and why. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 24, 2017, 04:23:21 PM
I'm not even sure what "second generation of interchanges" is supposed to mean/imply.  I wouldn't want to turn a freeway interchange into an at-grade intersection, but I also wouldn't want to turn the now-uncontrolled intersection three doors down from my house into a cloverstack.
Title: Re: Crash prone 'modern roundabouts'
Post by: TheArkansasRoadgeek on April 24, 2017, 04:29:12 PM
I love how we resort to the second generation of interchanges to solve a hazardous problem in an intersection. You would think we are pushing forward in transportation engineering not going backward. Weird.

Hey, the saying "hindsight's 20/20" is for a reason. Sometimes we get so caught up with going forward, we forget the original ideas we had before.
Quote
Ypu're not pushing towards 5th generation antibiotics or GM insulin to treat flu or broken leg.
You need a lot of water and rest -  or cast, respectively.  Both are first generation treatments...

Obsession with advanced design is actually bad - until there is a clear understanding of what are problems of old methods, when they work, and when they don't - and why.

Makes scense, but I just thought of how we always say we want and are pushing forward in something, and yet we are still using primitive methods of solving a problem. Noting wrong in that, but the question that comes up if we are still using old habits, is that: "Are we really improving and making progress?"
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 24, 2017, 04:32:36 PM


I have no idea what the traffic situation is like here, but safety isn't the only warrant for a intersection change. Capacity is another, and they probably thought they could get more traffic through here.

And I wanted to reply to the last quote with a joke, but I guess a statement will suffice. Nobody wants to pay for a 99.9% safe road (14ft lanes with 1000ft sightlines), so 95% safe roads have to suffice. There's only so much you can do without making the markings a distraction
Well, traffic counts are there. 20k from the tunnel and to the right and back, 5k on a street coming from the left looking from the tunnel.
Some turn lanes in roundabout footprint should help traffic lines.
As for 99.9% safe road... Not a penny. Because 1 accident out of 1000 passing vehicles is incredibly high. If you will, it means anyone driving through the intersection will crash annually....  Aim 1 out of million, and now we're talking.
Title: Re: Crash prone 'modern roundabouts'
Post by: TheArkansasRoadgeek on April 24, 2017, 04:36:29 PM
I'm not even sure what "second generation of interchanges" is supposed to mean/imply.  I wouldn't want to turn a freeway interchange into an at-grade intersection, but I also wouldn't want to turn the now-uncontrolled intersection three doors down from my house into a cloverstack.

There are three generations of interchanges, Cloverleaf, Roundabout, and Stack. Just look up some history and you'll see what I was talking about.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 24, 2017, 04:43:52 PM
Googling "second generation of interchanges" with quotes returns exactly two hits; without quotes returns nothing useful.

And I think you might be confusing roundabout interchanges with roundabouts.  They're not the same thing.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 24, 2017, 04:52:14 PM
I love how we resort to the second generation of interchanges to solve a hazardous problem in an intersection. You would think we are pushing forward in transportation engineering not going backward. Weird.

Hey, the saying "hindsight's 20/20" is for a reason. Sometimes we get so caught up with going forward, we forget the original ideas we had before.
Quote
Ypu're not pushing towards 5th generation antibiotics or GM insulin to treat flu or broken leg.
You need a lot of water and rest -  or cast, respectively.  Both are first generation treatments...

Obsession with advanced design is actually bad - until there is a clear understanding of what are problems of old methods, when they work, and when they don't - and why.

Makes scense, but I just thought of how we always say we want and are pushing forward in something, and yet we are still using primitive methods of solving a problem. Noting wrong in that, but the question that comes up if we are still using old habits, is that: "Are we really improving and making progress?"

Excellent question.
there is one ideology called KISS - aka "keep it simple, stupid!"
Now question is what "simple" means, and how idea of "simple" changes over time.
I don't know how traffic light were driven 50 years ago; I suspect either mechanics or some tubes and relays. Today it is a small chip - which can do much more.
What "simple" means in this case - advanced chip technology,  or 20 simple vacuum tubes?.. But although we have all those chips - plates spoons and forks are basically the same they were 100 years ago. Understanding where new tech actually makes life simple, and where it is more pain than gain is a big thing.
My impression - and I told that many times - understanding where roundabouts actually fit is the biggest deal here
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 24, 2017, 05:44:22 PM
It’s one thing to say roundabouts are designed to slow drivers down.   But that’s not what the Insurance Institute for Highway Safety is claiming.  On their main website they state that the tight circle of a roundabout “forces”  drivers to slow down.  There is a distinction there.  This woman in Britain wasn’t forced to slow down as she approached a roundabout:

Oh for fuck's sake, trade. You are taking that claim waaaay too literally.

It does force you to slow down, lest you want to collide with nature.

We don't build our world in straight lines. There's curves and corners everywhere, man. Roundabouts are adding corners and curves where there weren't any before (maybe), but that's just the nature of the intersection. And I've yet to see any studies that show a direct correlation between the circlular nature of the intersection, and a rise in collisions or injuries. Most of the collisions seem to be failure to yield or failure to maintain lane.
Title: Re: Crash prone 'modern roundabouts'
Post by: hm insulators on April 26, 2017, 12:53:56 PM
Apparently, leading police on a high speed chase and hitting another car is now a fault of a roundabout.

Idiots will always be idiots, there's no helping that.

And as soon as you make something idiot-proof, along comes a bigger idiot.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 26, 2017, 02:13:49 PM
It’s one thing to say roundabouts are designed to slow drivers down.   But that’s not what the Insurance Institute for Highway Safety is claiming.  On their main website they state that the tight circle of a roundabout “forces” drivers to slow down.  There is a distinction there.  This woman in Britain wasn’t forced to slow down as she approached a roundabout:

Oh for fuck's sake, trade. You are taking that claim waaaay too literally.

It does force you to slow down, lest you want to collide with nature.

We don't build our world in straight lines. There's curves and corners everywhere, man. Roundabouts are adding corners and curves where there weren't any before (maybe), but that's just the nature of the intersection. And I've yet to see any studies that show a direct correlation between the circlular nature of the intersection, and a rise in collisions or injuries. Most of the collisions seem to be failure to yield or failure to maintain lane.

Well, we hope that ALL roads are designed so that an average sober driver can navigate them without an issue. Moreover, they should be designed with some safety factor in mind - e.g. interstate lane is 12', and truck standard is 8'6", if I remember correctly.
Safety factor include, among other things, enough time to respond to mistake - your or other driver. That is why we have all red phase on traffic lights.
These are examples of proper engineering for
Quote
  failure to yield or failure to maintain lane
- and speed, I may add.
Looks like roundabout in question is not designed with sufficient cushion in mind. It is not only an issue of circle itself, it is an issue of, for example, signing approaches. Tunnels have their own set of issues - e.g. with line of sight and illumination - which have to be taken into account. I bet combination of "tunnel + roundabout" is not listed in any design manual..
ANd this is where engineering failed - or rather business as usual, if you ask me. They took "force to reduce speed" claim at face value....
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 26, 2017, 02:38:16 PM
 75-year-old woman killed in one-car Gorham roundabout

http://www.wlbz2.com/news/local/fatal-crash-closes-rte-114-bypass-in-gorham/434022792

Another example of a driver not being forced to slow down.  And of course I'm going to take the IIHS claim that roundabouts "forces" drivers to slow down literally.  Why wouldn't I?
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 26, 2017, 03:54:51 PM
And of course I'm going to take the IIHS claim that roundabouts "forces" drivers to slow down literally.  Why wouldn't I?

Because it was not the intent.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 26, 2017, 03:56:45 PM
75-year-old woman killed in one-car Gorham roundabout

http://www.wlbz2.com/news/local/fatal-crash-closes-rte-114-bypass-in-gorham/434022792

So is this now a 'crash prone modern roundabout'?
Title: Re: Crash prone 'modern roundabouts'
Post by: intelati49 on April 26, 2017, 04:56:12 PM
75-year-old woman killed in one-car Gorham roundabout

http://www.wlbz2.com/news/local/fatal-crash-closes-rte-114-bypass-in-gorham/434022792

So is this now a 'crash prone modern roundabout'?

I just realized he's the one who started this mess. We're really going around in circles right now (Pun unintentionally found in 2015 in this thread)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 26, 2017, 06:33:54 PM
75-year-old woman killed in one-car Gorham roundabout

http://www.wlbz2.com/news/local/fatal-crash-closes-rte-114-bypass-in-gorham/434022792

So is this now a 'crash prone modern roundabout'?

Any intersection where a fatal crash is involved warrants further analysis.  Most would agree that one fatal crash is worse than 100 property damage only crashes.

Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on April 26, 2017, 06:37:58 PM
this is fucking bullshit http://currentincarmel.com/carmel-mayor-instructing-police-to-ticket-drivers-for-not-using-turn-signals-in-roundabouts
you should signal in a roundabout, but when it was voted down by the city counsel, and state law is ambiguous to the issue, you shouldn't proceed with ticketing! 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 26, 2017, 06:42:26 PM
75-year-old woman killed in one-car Gorham roundabout

http://www.wlbz2.com/news/local/fatal-crash-closes-rte-114-bypass-in-gorham/434022792

So is this now a 'crash prone modern roundabout'?

Any intersection where a fatal crash is involved warrants further analysis.  Most would agree that one fatal crash is worse than 100 property damage only crashes.



But that doesn't make it crash-prone, any more than one fatal T-bone at a stoplight makes that intersection crash-prone.

A single accident does not a trend make.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 26, 2017, 07:16:23 PM
75-year-old woman killed in one-car Gorham roundabout

http://www.wlbz2.com/news/local/fatal-crash-closes-rte-114-bypass-in-gorham/434022792

So is this now a 'crash prone modern roundabout'?

Any intersection where a fatal crash is involved warrants further analysis.  Most would agree that one fatal crash is worse than 100 property damage only crashes.



But that doesn't make it crash-prone, any more than one fatal T-bone at a stoplight makes that intersection crash-prone.

A single accident does not a trend make.
Most intersections go for decades without a fatal event. And pretty often a fatal event is a solid, often the only convincing, reason to seriously reconsider design.  So one fatal accident is indeed one too many.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 26, 2017, 08:35:42 PM
The IIHS website concedes there is a potential crash problem at two-lane roundabouts.   It’s buried deep in the Q&A section about how roundabouts affect safety… at the very bottom.  When a pro-roundabout organization alludes to the potential crash problem at two-lane roundabouts, you know it’s legitimate.  Crash rates of 1 MEV - a common crash rate at signalized intersections — seems unattainable at these complex double-lane roundabouts. 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/IIHS2_zpsnwwifedn.png)

Most people can deal with a slight increase in crashes at roundabouts if they reduce injury and fatal crashes — although a sixfold increase in crashes is hardly a slight increase.  Do we really believe roundabouts reduce injury and fatal crashes as much as they say?  My concern is certain types of roundabouts have exceedingly high crash rates and they aren’t reducing injury and fatal crashes as much as the experts lead us to believe.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on April 26, 2017, 09:00:30 PM
75-year-old woman killed in one-car Gorham roundabout

http://www.wlbz2.com/news/local/fatal-crash-closes-rte-114-bypass-in-gorham/434022792

So is this now a 'crash prone modern roundabout'?

Any intersection where a fatal crash is involved warrants further analysis.  Most would agree that one fatal crash is worse than 100 property damage only crashes.



But that doesn't make it crash-prone, any more than one fatal T-bone at a stoplight makes that intersection crash-prone.

A single accident does not a trend make.
Most intersections go for decades without a fatal event. And pretty often a fatal event is a solid, often the only convincing, reason to seriously reconsider design.  So one fatal accident is indeed one too many.

There was over 30,000 fatals last year. Compared to the previous few decades, it was a good year.  That would mean by your suggestion above there are nearly 30,000 sections of road that need reconstructing in just one year alone.

I'm pretty sure you're just trolling right now with such thoughts that a fatal at a roundabout, without knowing a single other thing in regards to the incident, requires a reconstruction.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 26, 2017, 10:34:27 PM
Most intersections go for decades without a fatal event. And pretty often a fatal event is a solid, often the only convincing, reason to seriously reconsider design.  So one fatal accident is indeed one too many.

There was over 30,000 fatals last year. Compared to the previous few decades, it was a good year.  That would mean by your suggestion above there are nearly 30,000 sections of road that need reconstructing in just one year alone.

I'm pretty sure you're just trolling right now with such thoughts that a fatal at a roundabout, without knowing a single other thing in regards to the incident, requires a reconstruction.
Well, there are definitely a lot of areas which may need improvement, and often authorities are reactive, not proactive..
But indeed, I know nothing about the spot in question. Moreover, local elderly driver going at high speed to an  intersection sounds as some sort of driver issue. However, I am equally not going to downplay single fatal event as a non-issue. Because at a rate of fatal accidents we get, single one does form a trend. To put things in perspective - for a town of Gorham size, that may very well be the only one for the year.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 27, 2017, 09:35:39 AM
The IIHS website concedes there is a potential crash problem at two-lane roundabouts.   It’s buried deep in the Q&A section about how roundabouts affect safety… at the very bottom.  When a pro-roundabout organization alludes to the potential crash problem at two-lane roundabouts, you know it’s legitimate.  Crash rates of 1 MEV - a common crash rate at signalized intersections — seems unattainable at these complex double-lane roundabouts. 

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/IIHS2_zpsnwwifedn.png)

Most people can deal with a slight increase in crashes at roundabouts if they reduce injury and fatal crashes — although a sixfold increase in crashes is hardly a slight increase. 

Wow, congratulations on finding that!  Is this the first bit of evidence that anyone but us armchair geeks is actually acknowledging the safety distinction between single- and multi-lane roundabouts?  And no, a sixfold increase is no slight increase.

Do we really believe roundabouts reduce injury and fatal crashes...

Without the pursuant qualifying phrase, the answer would be 'yes.'  Chipping away at the claimed benefits does not dispel the benefits entirely.  The problem several of us have with your posting new blurbs one after the other is that you seem to be trying to offer evidence that all roundabouts are crash-prone.  This is not the way to do it, and I for one miss seeing the actual statistics you used to compile and post, showing what trends are actually happening at what locations.  I realize that probably took a lot of time and work but, failing that, linking to random news stories (for all I know generated by daily googling "roundabout accident") is not a good substitution.

...as much as they say?  My concern is certain types of roundabouts have exceedingly high crash rates and they aren’t reducing injury and fatal crashes as much as the experts lead us to believe.

But the answer to this seems to be 'yes.'  Especially if recent roundabout installation is increasingly favoring the types of roundabouts that have higher crash rates, I'd say it's a mathematical certainty that the numbers are wrong.

Most would agree that one fatal crash is worse than 100 property damage only crashes.

I'm sure everyone would agree that one fatal crash is worse than two property damage only crashes.  However, I'm not certain most would agree that one fatal crash is worse than 100 property damage only crashes.  1 to 100 is a pretty big leap, and I'd warrant that most people would need to employ some critical thinking before coming to an agreement or not.  There is a line somewhere, the point at which the number of property damage only crashes is as bad as one fatal crash, and that line is going to be different for everyone and it obviously has to be drawn somewhere by those in charge of deciding what type of intersection to build.



In other news, I noticed there were two separate car crashes on the same three-mile stretch of westbound Kellogg (in Wichita) within three hours of each other yesterday.  This is not evidence that all six-lane divided freeways are crash-prone.  But it might be evidence that this particular stretch of six-lane divided freeway is crash-prone.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 27, 2017, 12:45:00 PM
For what it's worth, in 2010, ~.006% of collisions involved a fatality (5,149,000 collisions compared to 32,999 fatalities). This data comes from the wiki page on US road fatalities (https://en.wikipedia.org/wiki/List_of_motor_vehicle_deaths_in_U.S._by_year).

If the current trends indicate anything, it's that one fatality for every 16,666 crashes is too many (based on Vision Zero movements lately). :-D
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 27, 2017, 09:57:22 PM
this is fucking bullshit http://currentincarmel.com/carmel-mayor-instructing-police-to-ticket-drivers-for-not-using-turn-signals-in-roundabouts
you should signal in a roundabout, but when it was voted down by the city counsel, and state law is ambiguous to the issue, you shouldn't proceed with ticketing!
Well, dealing with court is a punishment by itself. So even if no revenue is collected, (and many would just plead guilty to a lesser one - that would allow to raise funds for further construction), mayor would get it his way...
Title: Re: Crash prone 'modern roundabouts'
Post by: Brian556 on April 30, 2017, 06:03:24 PM
Video of car hitting roundabout:
https://www.facebook.com/ICSLTSIF/videos/1531549346856434/ (https://www.facebook.com/ICSLTSIF/videos/1531549346856434/)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 02, 2017, 10:30:19 AM
Distracted driver crashes into building in center of roundabout
https://www.villages-news.com/distracted-driver-crashes-building-center-roundabout/

Of the roughly 5000 roundabouts in America, five of them have buildings constructed in the central island (give or take a few).... we are now down to four.  Imagine the insurance premiums we would have if 1 in 5 buildings had cars plow through them.  According to the IIHS, the roundabout must have been malfunctioning since it didn't force the driver to slow down before plowing into the building.

Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on May 02, 2017, 12:53:24 PM
I'm pretty sure neither the IIHS nor FHWA (nor any transportation agency in the world, for that matter) recommends putting a building in the middle of a roundabout.

Then again, if it wasn't a roundabout, I guess cars would be crashing into the building all the time since it would literally be in the middle of the intersection.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 02, 2017, 01:27:37 PM
According to the IIHS, the roundabout must have been malfunctioning since it didn't force the driver to slow down before plowing into the building.

You're an idiot.
Title: Re: Crash prone 'modern roundabouts'
Post by: intelati49 on May 02, 2017, 01:56:52 PM
According to the IIHS, the roundabout must have been malfunctioning since it didn't force the driver to slow down before plowing into the building.

You're an idiot.

Not an idiot, just a blockhead.

A blockhead specialising in freaking out over isolated incidents.

But he does have a point for increased crash rates for multi lane roundabouts. It's just the consensus right now is that it needs more research. (not just a "random" person datamining)
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on May 02, 2017, 02:15:56 PM
Wow...this was in the Villages, FL, where I was just vacationing 2 weeks ago!  In fact, we stayed at our friends house about a mile from here.  It's a huge golf cart community (which the person driving would be better off doing for a while).  They have a countless number of multilane roundabouts in the community, but a building within the roundabout is extremely unusual (and I have no clue what the purpose of the building would've been for).

That said...this isn't the only roundabout within the community with a building in the middle.  https://goo.gl/maps/HHJrqc6PmUu

Since we're talking about roundabouts, and a golf cart community, they've even installed roundabouts for golf carts!  Not too far away from this accident scene is this one:  https://goo.gl/maps/2db3xjE7UgL2 , and elsewhere in the Villages is this one: https://goo.gl/maps/YEW4x4FaedQ2
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 02, 2017, 02:34:29 PM
Distracted driver crashes into building in center of roundabout
https://www.villages-news.com/distracted-driver-crashes-building-center-roundabout/

Of the roughly 5000 roundabouts in America, five of them have buildings constructed in the central island (give or take a few).... we are now down to four.  Imagine the insurance premiums we would have if 1 in 5 buildings had cars plow through them.  According to the IIHS, the roundabout must have been malfunctioning since it didn't force the driver to slow down before plowing into the building.

Good thing the car didn't T-bone another vehicle!  ~or~  Good thing it was a roundabout!
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 02, 2017, 02:47:59 PM
According to the IIHS, the roundabout must have been malfunctioning since it didn't force the driver to slow down before plowing into the building.

You're an idiot.

If I claimed that a red light forces drivers to stop, then you could call me an idiot.  In reality people blow through red lights just like they blow through roundabouts.  Now we can argue the likelihood of someone blowing through a red light vs. someone blowing through a roundabout, but it doesn’t change the fact that the IIHS premise of why roundabouts are safer is flawed. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 02, 2017, 02:56:35 PM
it doesn’t change the fact that the IIHS premise of why roundabouts are safer is flawed. 

Again, fallacy of equivocation.  The most commonsense reading of the word "force" in the IIHS context is not a literal one.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on May 02, 2017, 03:09:18 PM
If I claimed that a red light forces drivers to stop, then you could call me an idiot.  In reality people blow through red lights just like they blow through roundabouts.  Now we can argue the likelihood of someone blowing through a red light vs. someone blowing through a roundabout, but it doesn’t change the fact that the IIHS premise of why roundabouts are safer is flawed. 

I guess in the semantic sense, a curve on a roadway doesn't force (in the coercive sense) the driver to actually turn the steering wheel. But I think in common parlance you'd say the curve forces the driver to turn the wheel.

For example, my students in a class have to complete a presentation for a certain percentage of their grade. I will not literally drag them in front of the class at gunpoint and make them give a presentation on pain of death, but nonetheless I think the statement "I force my students to give a presentation in class" would be reasonably interpreted as "if they don't do it, there will be bad consequences for their grades."

Would you be satisfied if the verb "force to do X" was replaced with "strongly encourage a conscious, attentive driver to do X, given that failing to do so would subject one to a high risk of death, injury, and/or totaling one's vehicle"? Blowing through red lights and not following the course of the roadway (i.e. continuing straight ahead rather than turning) on entry to a roundabout would seem to fall into the same category there.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 03, 2017, 12:12:01 PM
I guess in the semantic sense, a curve on a roadway doesn't force (in the coercive sense) the driver to actually turn the steering wheel. But I think in common parlance you'd say the curve forces the driver to turn the wheel.

For example, my students in a class have to complete a presentation for a certain percentage of their grade. I will not literally drag them in front of the class at gunpoint and make them give a presentation on pain of death, but nonetheless I think the statement "I force my students to give a presentation in class" would be reasonably interpreted as "if they don't do it, there will be bad consequences for their grades."

Would you be satisfied if the verb "force to do X" was replaced with "strongly encourage a conscious, attentive driver to do X, given that failing to do so would subject one to a high risk of death, injury, and/or totaling one's vehicle"? Blowing through red lights and not following the course of the roadway (i.e. continuing straight ahead rather than turning) on entry to a roundabout would seem to fall into the same category there.

A student could blow off your presentation assignment, giving you the middle finger as they walk out of class.  Or a suicidal person could purposely drive through the middle of a roundabout at 100 mph, launching 50 feet into the air after striking the central island curbing.  A passing grade and the preservation of life is usually enough encouragement to prevent these things from happening... but not always.  In the example of a suicidal individual, the tight circle of a roundabout actually encourages them to speed up, not slow down.  Taken literally, the idea that roundabouts "force" drivers to slow down is pure lunacy.

The public has been conditioned to believe that roundabouts are always the safest alternative.  The IIHS is perpetuating that myth by saying that roundabouts "force" drivers to slow down.  Only a fool would argue that red lights force drivers to stop, but it's somehow OK for the IIHS to argue that roundabouts force drivers to slow down?  Just try to convince the family members of the two men killed in Gainsville on Tuesday that the roundabout forced the driver to slow down. 

Roundabout crash kills two, police say
http://www.gainesville.com/news/20170502/roundabout-crash-kills-two-police-say

People are encouraged to slow down at a roundabout just like they are encouraged to stop at a red light.  Had the IIHS said that the tight circle of a roundabout only "encourages" drivers to slow down, then roundabouts would be at the same level as traffic signals - where if you ignore the encouragement a deadly crash can occur.  At that point who's to say what type of intersection is safer?  The IIHS didn't want that.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on May 03, 2017, 12:45:49 PM
I guess in the semantic sense, a curve on a roadway doesn't force (in the coercive sense) the driver to actually turn the steering wheel. But I think in common parlance you'd say the curve forces the driver to turn the wheel.

For example, my students in a class have to complete a presentation for a certain percentage of their grade. I will not literally drag them in front of the class at gunpoint and make them give a presentation on pain of death, but nonetheless I think the statement "I force my students to give a presentation in class" would be reasonably interpreted as "if they don't do it, there will be bad consequences for their grades."

Would you be satisfied if the verb "force to do X" was replaced with "strongly encourage a conscious, attentive driver to do X, given that failing to do so would subject one to a high risk of death, injury, and/or totaling one's vehicle"? Blowing through red lights and not following the course of the roadway (i.e. continuing straight ahead rather than turning) on entry to a roundabout would seem to fall into the same category there.

A student could blow off your presentation assignment, giving you the middle finger as they walk out of class.  Or a suicidal person could purposely drive through the middle of a roundabout at 100 mph, launching 50 feet into the air after striking the central island curbing.  A passing grade and the preservation of life is usually enough encouragement to prevent these things from happening... but not always.  In the example of a suicidal individual, the tight circle of a roundabout actually encourages them to speed up, not slow down.  Taken literally, the idea that roundabouts "force" drivers to slow down is pure lunacy.

The public has been conditioned to believe that roundabouts are always the safest alternative.  The IIHS is perpetuating that myth by saying that roundabouts "force" drivers to slow down.  Only a fool would argue that red lights force drivers to stop, but it's somehow OK for the IIHS to argue that roundabouts force drivers to slow down?  Just try to convince the family members of the two men killed in Gainsville on Tuesday that the roundabout forced the driver to slow down. 

Where's the thread devoted to crash-prone railroad crossings? Lights, bells, and gates don't "force" you to stop, yet are arguably more dangerous/deadly than a roundabout. What's the solution when a crossing has passive warning devices (signs only)? Put up signals and gates...same silver-bullet crash fix mentality that roundabout installations have been claimed here to have been peddled to the public. The same suicidal person can blow-through a gate (hell, they're designed to break away) and smash right into a passing train, possibly into a car transporting hazardous materials.

ANYTHING, even "properly designed" when not used properly can have deadly consequences.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 03, 2017, 12:53:32 PM
Taken literally, ...

You seem to be the only one on here who does, though.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 03, 2017, 01:57:50 PM
Ultimately, if the argument is roundabouts force drivers to slow down then by the same logic red lights force drivers to stop.  Of course neither argument is true.  People blow through red lights and get into deadly crashes and people blow through the center of roundabouts and get into deadly crashes.  Without knowing the rate of these deadly crashes for each intersection type, how can the IIHS claim that roundabouts are safer than traffic signals?  By arguing that roundabouts force drivers to slow down the IIHS completely downplaying the possibility of a driver blowing through the center of the roundabout at high speeds.   It’s easy to argue that roundabouts are safer than traffic signals when you start with the premise that everyone traveling through a roundabout is driving slowly.  The problem is their whole premise is wrong (the double fatality crash at the Gainsville roundabout is evidence of this). 
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on May 03, 2017, 02:09:17 PM
The whole premise of Who Wants To Be A Millionaire is that the people on the show want to be a millionaire.  The premise is the contestants will answer 15 questions correctly and win a million dollars.  The problem is their whole premise is wrong (you can stop at any point and take home the money you already won).  Thus, all of television is incorrect and we should explode into a fireball of grass clippings.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on May 03, 2017, 02:27:35 PM
We know the rate of deadly crashes at signalized intersections versus roundabouts: there's empirical data on the point, from jurisdictions all over the world. There's no need to base the safety claim on whether or not drivers actually are forced to slow down or whether or not they obey traffic signals; it can be derived from simple observation of fatality incidence over time, without a causal argument.

The argument you seem to be making, out of your infatuation with Dearborn-style evenly spaced grid streets with wide medians, signalized intersections, and "green wave" progression timing in every direction (a situation that obtains in the Detroit area and virtually nowhere else in the country, since most grids are irregular due to either the local geographic features or historical development patterns), is that since collisions are not completely preventable, it really doesn't matter what intersection design is used at a particular location since accidents are inevitable, and any effort to reduce crash fatality rates or severity should take a back seat to the potential efficiency of evenly-spaced arterial grids with Michigan lefts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 03, 2017, 02:38:39 PM
We know the rate of deadly crashes at signalized intersections versus roundabouts: there's empirical data on the point, from jurisdictions all over the world. There's no need to base the safety claim on whether or not drivers actually are forced to slow down or whether or not they obey traffic signals; it can be derived from simple observation of fatality incidence over time, without a causal argument.

The argument you seem to be making, out of your infatuation with Dearborn-style evenly spaced grid streets with wide medians, signalized intersections, and "green wave" progression timing in every direction (a situation that obtains in the Detroit area and virtually nowhere else in the country, since most grids are irregular due to either the local geographic features or historical development patterns), is that since collisions are not completely preventable, it really doesn't matter what intersection design is used at a particular location since accidents are inevitable, and any effort to reduce crash fatality rates or severity should take a back seat to the potential efficiency of evenly-spaced arterial grids with Michigan lefts.
Well, anecdotal fact: we had a high traffic intersection replaced with roundabout nearby. After that traffic reduced due to relocation of some offices (not related to construction). Pre-construction documents showed 0 fatal accidents over 10 years. There was 1 in 5 years after construction
Is that a statistically significant trend? No, because 0 and 1 are within statistical error margin. You really need high volume data, which is pretty much impossible to collect without being able to access all raw statistics and probably changing report forms...

What Trade is doing by bringing individual crash reports is beyond me. But he mentioned significant number of high-crash rate sites... Which is statistically significant piece of information.
I didn't see proper statistics of fatal accidents. Claiming that "there are almost no fatalities" is clearly rebutted by Trade's  accident reports, though. It doesn't matter if accident is weird one-off. Almost all fatal accidents are such these days, and same situations contribute towards traffic light and stop/yield controlled locations.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 03, 2017, 02:58:50 PM
Had the IIHS said that the tight circle of a roundabout only "encourages" drivers to slow down, then roundabouts would be at the same level as traffic signals - where if you ignore the encouragement a deadly crash can occur.

So is your problem the roundabouts or the FHWA's grammar?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 03, 2017, 03:11:58 PM
Had the IIHS said that the tight circle of a roundabout only "encourages" drivers to slow down, then roundabouts would be at the same level as traffic signals - where if you ignore the encouragement a deadly crash can occur.

So is your problem the roundabouts or the FHWA's grammar?
Let me try to interpret:
Looks like problem is with state/local authorities taking that statement at face value, and failure to address underlying conditions. Which is actually a problem.
We talked about a roundabout at the end of tunnel. Clearly that is not safest possible design, and clearly roundabout itself is not the cure or problem, it is just part of a failure to create safe situation.
Just another anecdotal situation:
we had another roundabout built nearby. An intersection before that one was built had a hill blocking the view when approaching from one direction. Making things worse, traffic light was visible from far away - and often people sped up to catch the light. That was a relatively slow light, giving priority to higher traffic cross street.  At the same time, another car could be making a turn while someone flies over the hill at them.. I had some close calls personally, both as bullet and target.
Now that hill was smoothed quite a bit during roundabout construction. That alone could make light controlled intersection much better - but was funded only as part of a much bigger project including roundabout. This is what I call "addressing underlying condition". And roundabout should not take whole - only  small part, if any - credit for making that intersection safer (although I didn't see any data or crashes)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 03, 2017, 03:32:23 PM
...

Let me try to interpret:
Looks like problem is with state/local authorities taking that statement at face value

I have trouble believing that any DOT has in fact interpreted the word "forces" in the IIHS statement ("the tight circle of a roundabout forces drivers to slow down," for those who don't want to dig back several pages to find the original statement) to mean that a roundabout literally and physically prevents a driver from going above a certain speed when entering the intersection–and has then installed a roundabout based on the expectation that zero drivers will ever enter at faster than x mph.

To suggest that the reason roundabouts are being constructed is that the word "forces" in that statement was taken as absolutely literal......is silly.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 03, 2017, 03:49:11 PM
...

Let me try to interpret:
Looks like problem is with state/local authorities taking that statement at face value

I have trouble believing that any DOT has in fact interpreted the word "forces" in the IIHS statement ("the tight circle of a roundabout forces drivers to slow down," for those who don't want to dig back several pages to find the original statement) to mean that a roundabout literally and physically prevents a driver from going above a certain speed when entering the intersection–and has then installed a roundabout based on the expectation that zero drivers will ever enter at faster than x mph.

To suggest that the reason roundabouts are being constructed is that the word "forces" in that statement was taken as absolutely literal......is silly.
If it looks like a duck...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 03, 2017, 04:32:30 PM
We know the rate of deadly crashes at signalized intersections versus roundabouts: there's empirical data on the point, from jurisdictions all over the world. There's no need to base the safety claim on whether or not drivers actually are forced to slow down or whether or not they obey traffic signals; it can be derived from simple observation of fatality incidence over time, without a causal argument.

It’s difficult to determine how effective roundabouts are at reducing fatal crashes - assuming they reduce them at all - because fatal crashes are such a rare event.   In addition, signalized intersections that have been the site of a fatal crash are often the intersections specifically targeted for roundabout conversion.  Comparing the safety of the worst performing signalized intersections to roundabouts isn't the same as comparing roundabouts to a standard signalized intersection.  Interestingly, when a roundabout is the site of a fatal crash they don’t become a target to be converted back to a signalized intersection. 

On September 21, 2014 a 23 year old motorcyclist slid into the roundabout island on Fischer-Hallman Road in Kitchener and was pronounced dead at hospital.  Investigator Staff Sgt. James Strand concluded that “speed and poor rod conditions were the reason for this collision happening and not the roundabout” .   Since this crash wasn’t blamed on the roundabout, the Region of Waterloo can keep claiming that there has never been a fatality in a local roundabout.

Roundabout death? Motorcycle speeding, lost control on wet road, before Kitchener crash
http://www.therecord.com/news-story/6225063-roundabout-death-motorcycle-speeding-lost-control-on-wet-road-before-kitchener-crash/
Title: Re: Crash prone 'modern roundabouts'
Post by: intelati49 on May 03, 2017, 05:04:09 PM
We know the rate of deadly crashes at signalized intersections versus roundabouts: there's empirical data on the point, from jurisdictions all over the world. There's no need to base the safety claim on whether or not drivers actually are forced to slow down or whether or not they obey traffic signals; it can be derived from simple observation of fatality incidence over time, without a causal argument.

Since this crash wasn’t blamed on the roundabout, the Region of Waterloo can keep claiming that there has never been a fatality in a local roundabout.


{{citation-needed}}

Just because the roundabout isn't at fault doesn't mean that information disappears. (Or at least isn't in Missouri)

And if they're claiming that, they're the idiots.

(https://i.imgur.com/kVu8c7B.png)

Article with corresponding crash (http://www.ky3.com/content/news/Hit-and-run-crash-kills-man-at-busy-intersection-by-Missouri-State-411506405.html)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 03, 2017, 05:14:54 PM
If it looks like a duck...

It doesn't look like a duck.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on May 03, 2017, 05:32:09 PM
Yes, it's difficult to determine in any single location due to fatalities being a rare event. That's why the data is aggregated. Here are two meta-analysis studies that aggregate local/regional studies into a more complete picture:

Road safety effects of roundabouts: A meta-analysis (http://www.sciencedirect.com/science/article/pii/S0001457516304560)
Effects on Road Safety of Converting Intersections to Roundabouts: Review of Evidence from Non-U.S. Studies (http://trrjournalonline.trb.org/doi/abs/10.3141/1847-01)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 03, 2017, 05:57:26 PM
Yes, it's difficult to determine in any single location due to fatalities being a rare event. That's why the data is aggregated. Here are two meta-analysis studies that aggregate local/regional studies into a more complete picture:

Road safety effects of roundabouts: A meta-analysis (http://www.sciencedirect.com/science/article/pii/S0001457516304560)
Effects on Road Safety of Converting Intersections to Roundabouts: Review of Evidence from Non-U.S. Studies (http://trrjournalonline.trb.org/doi/abs/10.3141/1847-01)
In short: decrease of number of fatal accidents, no effect to possibly increase of property-only crashes; no breakdown on roundabout type - small side roads vs major roads, 1-lane vs 2-lane vs 3-lane; 2 US papers in past 2 years.

Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on May 04, 2017, 11:44:25 AM
In short: decrease of number of fatal accidents, no effect to possibly increase of property-only crashes; no breakdown on roundabout type - small side roads vs major roads, 1-lane vs 2-lane vs 3-lane; 2 US papers in past 2 years.

To be precise (I believe the first article includes all the studies that were looked at in the second, since it's newer): ~65% decrease fatality accidents, ~35% decrease in injury accidents, a statistical wash on PDO.

There are extant studies that break down effectiveness by roundabout type but they are based on smaller samples or case studies, and there you run into the rare events problem (somewhat resolved by lumping injury and fatality accidents into a single category).

The general evidence is that injury and fatality accidents are reduced regardless of roundabout size, but the effects are smaller at higher volume, higher capacity roundabouts. PDO tends to go up, as you have more vehicles getting into low angle-of-incidence, low net-momentum collisions due to failure to yield and/or failure to stay in lane. That PDO goes up is kind of what you'd expect since vehicles generally don't pass next to each other on a single-lane roundabout but can and do on a multi-lane roundabout, and staying in lane on a curve takes more driver attention than staying in lane in a straight line across a typical signalized intersection. Hence the recommended use of turbo markings etc. rather than the old--school UK approach of "you're supposed to know where the lanes are even though there are no markings."
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 04, 2017, 12:15:24 PM
Yes, it's difficult to determine in any single location due to fatalities being a rare event. That's why the data is aggregated. Here are two meta-analysis studies that aggregate local/regional studies into a more complete picture:

Road safety effects of roundabouts: A meta-analysis (http://www.sciencedirect.com/science/article/pii/S0001457516304560)
Effects on Road Safety of Converting Intersections to Roundabouts: Review of Evidence from Non-U.S. Studies (http://trrjournalonline.trb.org/doi/abs/10.3141/1847-01)

Thank you for posting those aggregate studies.  First off the safety findings in those studies aren’t as impressive as the 2000 IIHS study.  This is important as a lot of complex roundabouts have been constructed in this country after agencies have highlighted the safety statistics found in the IIHS study.  Do you realize the only 2x2 roundabout analyzed in the IIHS study was a roundabout on Avon Road in Vale, Colorado?  Avon road has a speed limit of 25 mph.  Conveniently road agencies in America have promoted the safety statistics of double-lane roundabouts for the next 20-years based on a roundabout in the middle of a ski-resort.  But i digress...

The real issue is not all roundabouts are created equal.  Of the roughly 5,000 roundabouts in America only a few hundred have complex 2x2 or 3x2 geometries.  That’s less than 5% of the total roundabouts in this country.  If these complex roundabouts have poor safety records, they would be masked in these aggregate studies since single-lane roundabouts would be weighted heavily in the analysis.  When looking into just these complex roundabouts a troubling safety trend appears.  The average crash rate of these complex roundabouts is about 4.0 MEV; roughly 4X higher than the crash rate of a typical signalized intersection.  It’s harder to tie down the injury crash rates, but if PDO crashes are 4X higher it’s not a stretch to assume that they won’t see injury crashes reduced by 35%.  Put another way, the aggregate studies say that there is a ~35% reduction in injury crashes, but that’s assuming total crashes are roughly the same.
 
The FHWA and IIHS need to analyze the safety performance of complex roundabouts; ones with 2x2 and 3x2 geometries.  Only then will we get a good understanding if these roundabouts are even worth building from a safety perspective.  Imagine if they found complex roundabouts see a 300% increase PDO crashes, a 22% increase in injury crashes, and a 0% increase in fatalities.  Would communities be so eager to build THESE roundabouts then?  I don’t have a problem with agencies promoting roundabouts, but we should at least know which types of roundabouts will reduce injury crashes and which ones won’t.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on May 04, 2017, 12:43:59 PM
Well, then you can either accept evidence from other countries that have a lot more multi-lane roundabouts already (which do show improvements in both injury and fatality rates), or you can wait until sufficient data is accumulated on multi-lane roundabouts in the U.S. alone to draw those conclusions from a large sample over time and space.

What we do know, based on the laws of physics, is that injury and (particularly) fatality accidents are highly associated with two factors in collisions: high speed and high net momentum. Putting aside the semantics of the word "force" for a moment, the evidence is that most drivers traverse roundabouts at lower speed than they would traverse a signalized intersection and that most drivers follow lane markings and curbs so the angle of incidence in the event of a collision is low with both vehicles moving on roughly the same vector, hence low net momentum.

This design is effective to the extent that fatality accidents at roundabouts are almost exclusively the result of driver impairment or criminal activity in some form (DUI, driving while senile, heart attack behind the wheel, evading police in a high-speed pursuit, etc.), as virtually all of your examples to date have been. By contrast a momentary lapse in concentration in a roundabout that results in a collision will, at worst, give you and/or the other driver whiplash and a very expensive repair bill, rather than a guaranteed trip to the hospital or the morgue from a side impact or head-on crash when you try to beat a red or don't see it in time.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 04, 2017, 01:30:47 PM
lordsuch & tradephoric:  Thank you both for quickly bringing this thread back into an intelligent, reasonable, and interesting conversation.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 04, 2017, 04:09:44 PM
Well, then you can either accept evidence from other countries that have a lot more multi-lane roundabouts already (which do show improvements in both injury and fatality rates), or you can wait until sufficient data is accumulated on multi-lane roundabouts in the U.S. alone to draw those conclusions from a large sample over time and space.

What we do know, based on the laws of physics, is that injury and (particularly) fatality accidents are highly associated with two factors in collisions: high speed and high net momentum. Putting aside the semantics of the word "force" for a moment, the evidence is that most drivers traverse roundabouts at lower speed than they would traverse a signalized intersection and that most drivers follow lane markings and curbs so the angle of incidence in the event of a collision is low with both vehicles moving on roughly the same vector, hence low net momentum.

This design is effective to the extent that fatality accidents at roundabouts are almost exclusively the result of driver impairment or criminal activity in some form (DUI, driving while senile, heart attack behind the wheel, evading police in a high-speed pursuit, etc.), as virtually all of your examples to date have been. By contrast a momentary lapse in concentration in a roundabout that results in a collision will, at worst, give you and/or the other driver whiplash and a very expensive repair bill, rather than a guaranteed trip to the hospital or the morgue from a side impact or head-on crash when you try to beat a red or don't see it in time.
That still doesn't address issues of throughput or tradeoffs between property and injury accidents.
Would roundabout be still better compared to intersection with wavy approaches, for example?
Title: Re: Crash prone 'modern roundabouts'
Post by: UCFKnights on May 04, 2017, 04:27:19 PM
Well, then you can either accept evidence from other countries that have a lot more multi-lane roundabouts already (which do show improvements in both injury and fatality rates), or you can wait until sufficient data is accumulated on multi-lane roundabouts in the U.S. alone to draw those conclusions from a large sample over time and space.
Do other countries have the amount of improper lane usage in their roundabouts as compared to the US? Its still my core concern with multilane roundabouts, and why they fail so quickly when you add lanes... many Americans simply cannot understand that a left cannot be made from the right lane, as if another car fails to stop for you, you will crash. When I go through multilane roundabouts, I see someone use the wrong lane for their turn just about every single time. And from talking to my cop friends, they seem unaware that using the wrong lane in the roundabout causes an accident and file their accident reports incorrectly quite frequently.
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on May 04, 2017, 06:26:29 PM
In my experience driving in the UK and observing in Ireland, where lane marking is rare except at signalized roundabouts, lane discipline is nonetheless quite good.

But they have 50 years of experience with them, while on the continent where they're more recently introduced, turbo markings and the like seem to have been settled on as the best approach.

Even in the UK signalized or complex roundabouts will a typically have a "Get in lane" lane assignment sign with destinations in advance of the roundabout, in addition to the standard diagrammatic guide sign, something that really should be introduced here, like here: https://goo.gl/images/FyOjMu
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 18, 2017, 12:12:35 PM
A presentation that evaluates the safety of Wisconsin roundabouts was given during the 5th International Conference on Roundabouts held on May 8-10, 2017 in Green Bay.   All the roundabouts evaluated in this presentation were built in 2009 and before.   This means that the explosion of triple-lane roundabouts built in Wisconsin after 2009 were not evaluated in this analysis - and these are the types of roundabouts that seem to have the highest crash rates. 
 
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Untitled01_zps5vcivcyn.png)
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Untitled02_zpsofwlp6an.png)
http://teachamerica.com/RAB17/RAB174A_Bill/index.htm

Of the 29 multi-lane roundabouts evaluated, there was a 35% increase in total crashes and a 26% decrease in injury and fatal crashes (KABC crashes).   If you look at the 39 urban roundabouts evaluated, there was a 48% increase in total crashes and just an 18% decrease in injury and fatal crashes (KABC crashes).   It’s great that all this data exists but it would be nice if WTOP broke it down further.  What would happen if they evaluated the safety performance of urban multi-lane roundabouts that have two-approach lanes at all legs of the roundabout (IE 2x2 and 3x2 roundabouts)?   It’s quite possible you would see an increase in both injury crashes and total crashes if just those types of multi-lane roundabouts were evaluated.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 19, 2017, 11:50:51 AM
By the City’s [of Lincoln] own admission the chain link fencing was a temporary measure.  They never had any intention to keep the chain link fencing in place.  If it was shown to be ineffective at reducing crashes they would have ripped it out.  If it was shown to reduce crashes (as they believe it did) they would replace it with permanent fencing.  But there’s a bigger issue here then what type of fence the city decided to use.  How does the city know the fencing was effective at reducing crashes at the roundabout in the first place?  The problem is at the same time they installed the fencing they removed a circulating lane of traffic inside the roundabout.  Those two changes combined saw a reduction in crashes at the roundabout, but how do we know if the reduction was due to the fencing or the reduction of a circulating lane? 

Luckily, they have added fencing at the most crash prone roundabout in Michigan (186 crashes in 2015).  No other changes were made other than the fencing so we will see if it actually helps reduce the total number of crashes. 

http://www.wxyz.com/news/region/oakland-county/drivers-have-mixed-feelings-about-new-fences-at-m-5-roundabout

We now have crash data to see if the screen fencing added to the M-5 & Pontiac Trail roundabout in Michigan was effective at reducing total crashes.  When comparing the 6 months before the screen fence was added to the 6 months after, there was no reduction in the total number of crashes.  From an operational standpoint, they do believe the screen fence provided greater gaps for drivers to enter the roundabout.  This data was presented by Tom Blust at the 5th International Conference on Roundabouts:

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Untitledfencing3_zpsp2fdrbnr.png)
http://teachamerica.com/RAB17/RAB176A_Blust/index.htm

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 25, 2017, 11:28:49 AM
Samuel Bobko gave a presentation at the 5th International Conference on Roundabout that focused on a multi-lane roundabout in Cleveland Ohio at I-71 and Quigley Road.   It was constructed in 2007 and he acknowledged that there was an elevated crash issue at the roundabout.  The presenter thinks that the increase in crashes starting around 2011 was due to I-71 being under construction and more drivers were getting off and going through the roundabout. He then goes through low cost improvements made to the roundabout that reduced the collisions at the roundabout.  While the presenter hits on the usual changes —lane arrows, pavement markings, signage changes — one of the biggest changes that likely reduced the crashes was the removal of a circulating lane inside the roundabout. 

The presenter claims that the roundabout was never constructed for safety.   But isn’t it always about safety when it comes to modern-roundabouts?   We have been conditioned to believe that roundabouts are safe and this roundabout was no exception.  Here is the official press release from ODOT back in 2006:

Quote
August 18, 2006, Garfield Heights, OH...
This is the first modern roundabout to be built in Northeast Ohio. The only other roundabout in Ohio is in the City of Dublin. A roundabout was chosen for this location because it will increase capacity and lower delays, calm traffic, improve aesthetics, improve safety, and be able to handle U-turn movements.
https://www.dot.state.oh.us/projects/ClevelandUrbanCoreProjects/Innerbelt/News%20Releases/QuigleyRdPressRelease.pdf

Here’s the before and after crashes at the I-71 and Quigley Road roundabout.  Even after the improvements were made to the roundabout the crashes in 2015 and 2016 were still much higher than the pre-roundabout crashes.  And there doesn’t appear to be a big drop in injury crashes either.  I’m not seeing the safety improvements ODOT were advertising back in 2006 play out at this roundabout.  This is yet another example of a multi-lane roundabout that failed to improve safety.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Untitled35_zpsqvzxdfho.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 25, 2017, 11:41:59 AM

The presenter claims that the roundabout was never constructed for safety.   But isn’t it always about safety when it comes to modern-roundabouts?   We have been conditioned to believe that roundabouts are safe and this roundabout was no exception.  Here is the official press release from ODOT back in 2006:

Quote
August 18, 2006, Garfield Heights, OH...
This is the first modern roundabout to be built in Northeast Ohio. The only other roundabout in Ohio is in the City of Dublin. A roundabout was chosen for this location because it will increase capacity and lower delays, calm traffic, improve aesthetics, improve safety, and be able to handle U-turn movements.
https://www.dot.state.oh.us/projects/ClevelandUrbanCoreProjects/Innerbelt/News%20Releases/QuigleyRdPressRelease.pdf
Well, you cannot have a cake and eat it too. At some point I expect rhetoric shift toward "it is about capacity, and accident rate is increased only by that much.. "
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 26, 2017, 02:19:54 PM
Well, you cannot have a cake and eat it too. At some point I expect rhetoric shift toward "it is about capacity, and accident rate is increased only by that much.. "

There is a growing consensus that there is a crash problem at these multi-lane roundabouts.  But you still have roundabout experts saying that the injury crashes have been taken care of at these high crash roundabouts.  The problem is they have convinced themselves that roundabouts are safer and won’t even entertain the idea that certain types of roundabouts may be increasing injury and fatal crashes.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 26, 2017, 03:50:01 PM
Well, you cannot have a cake and eat it too. At some point I expect rhetoric shift toward "it is about capacity, and accident rate is increased only by that much.. "

There is a growing consensus that there is a crash problem at these multi-lane roundabouts.  But you still have roundabout experts saying that the injury crashes have been taken care of at these high crash roundabouts.  The problem is they have convinced themselves that roundabouts are safer and won’t even entertain the idea that certain types of roundabouts may be increasing injury and fatal crashes.
Thing is, I don't understand how that happened. Why would engineers jump on the idea?
My only explanation is that roundabout is the only big thing traffic engineers in many areas can design, especially in northeast-midwest. Few big projects going on; even big rebuilds seem to be done exactly and carefully by old blueprints...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 03, 2017, 08:04:24 AM
Armdale Roundabout safety probed
http://thechronicleherald.ca/metro/1195561-armdale-roundabout-safety-probed

The Armdale rotary in Halifax, Nova Scotia was completed in 1956 and was converted to modern roundabout standards in 2007 (although I’ll note there is no truck apron at the roundabout).  A few years after the conversion, municipal staff noted a “sharp and sustained”  increase in accidents (jumping from the low 60s to the high 90s).  Here are a few recent news reports of injury accidents that have occurred at the roundabout:

http://www.cbc.ca/news/canada/nova-scotia/armdale-roundabout-crash-sends-3-to-hospital-with-serious-injuries-1.3116629
http://www.cbc.ca/news/canada/nova-scotia/armdale-roundabout-motorcyclist-crash-1.3300385



Major crashes still occurring at the Armdale roundabout.  A crash this week saw a small compact car take out a steel light pole and a wooden pole all in one shot!  Car must have been flying to do that much damage...

Roundabout crash knocks down poles, slows traffic in Halifax
http://thechronicleherald.ca/metro/1473156-roundabout-crash-knocks-down-poles-slows-traffic-in-halifax

Armdale Roundabout car-pedestrian crash sends 72-year-old man to hospital
http://www.cbc.ca/news/canada/nova-scotia/armdale-roundabout-car-pedestrian-crash-sends-72-year-old-man-to-hospital-1.3177515

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 15, 2017, 07:50:28 PM
The IIHS remade their roundabout safety video that reflects the reality of how people are driving though them.  Just imagine if the IIHS made a video that promoted the safety of traffic signals by making definitive statements about how red lights force drivers to stop.  They would lose credibility because everyone knows red lights don’t force drivers to stop.  But it’s acceptable for them to argue that roundabouts are safe simply because roundabout have tight curves.  That's justification that roundabouts are safer?

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 16, 2017, 01:33:25 AM
Okay that was actually pretty funny.

But, you still seem to be taking this whole "force drivers to slow down" thing a little too seriously.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 16, 2017, 07:55:10 AM
Okay that was actually pretty funny.

But, you still seem to be taking this whole "force drivers to slow down" thing a little too seriously.
Try looking at in a bigger context.
If you know thee is an obstacle on a road, you're slowing down. Roundabout, speed bump, intersection, "object on road ahead".. Just knowing something may force you doing things.. Same thing as cop saying "make that music quieter" - no need to use actual force.
With that, those DUI (designed under influence) approaches to roundabout  send a good reminder to someone driving that roundabout on a regular basis - forcing them to prepare for safe pass. But at the same time DUI approaches hide an obstacle from a stranger. This is unlike traffic light, where approaches are mostly straight, and lights can be seen from a distance. And low visibility on approach can lead to higher accident rate etc. This is not unlike DUI roundabout approaches.
So yes - roundabouts try to force drivers to slow down.. but the message can easily be misunderstood.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 16, 2017, 05:25:23 PM
So, basically, it's easier to run a red light than to run a roundabout?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 17, 2017, 06:12:08 AM
So, basically, it's easier to run a red light than to run a roundabout?
That depends on what you mean by "run".
Find yourself in a middle of intersection when you didn't expect that? Probably more difficult traffic light where visibility is not artificially engineered.
Enter intersection deliberately  disregarding interests and intentions of other drivers regardless of right of way? Fairly common for traffic lights as drivers accelerate on yellow, and basically design behavior for roundabouts... 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 17, 2017, 03:39:08 PM
Find yourself in a middle of intersection when you didn't expect that? Probably more difficult traffic light where visibility is not artificially engineered.

What?
Title: Re: Crash prone 'modern roundabouts'
Post by: JJBers on June 17, 2017, 04:37:16 PM


So, basically, it's easier to run a red light than to run a roundabout?
That depends on what you mean by "run".
Find yourself in a middle of intersection when you didn't expect that? Probably more difficult traffic light where visibility is not artificially engineered.
Enter intersection deliberately  disregarding interests and intentions of other drivers regardless of right of way? Fairly common for traffic lights as drivers accelerate on yellow, and basically design behavior for roundabouts...

I don't understand half of this

LGL52VL

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 17, 2017, 06:33:34 PM
Find yourself in a middle of intersection when you didn't expect that? Probably more difficult with traffic light where visibility is not artificially engineered.

What?
sorry, missed "with"
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 17, 2017, 08:24:47 PM
Find yourself in a middle of intersection when you didn't expect that? Probably more difficult with traffic light where visibility is not artificially engineered.

What?

sorry, missed "with"

Ahh okay.

While it is easier to "get away" with not stopping at a signal, not doing so can be catastrophic. Now, I'm not sure if that's something that actually happens a lot. We know at multi-lane roundabouts, crashes seem to go up. But are they the result of small things like failure to yield, or something larger like driving over the center circle? I don't think people driving over the center of the circle is very common.

It's possible to get away with running a red light. It's not possible to get away with failing to yield to the central island. I'll give you that. But how often is this an issue?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 17, 2017, 08:42:14 PM
Find yourself in a middle of intersection when you didn't expect that? Probably more difficult with traffic light where visibility is not artificially engineered.

What?

sorry, missed "with"

Ahh okay.

While it is easier to "get away" with not stopping at a signal, not doing so can be catastrophic. Now, I'm not sure if that's something that actually happens a lot. We know at multi-lane roundabouts, crashes seem to go up. But are they the result of small things like failure to yield, or something larger like driving over the center circle? I don't think people driving over the center of the circle is very common.

It's possible to get away with running a red light. It's not possible to get away with failing to yield to the central island. I'll give you that. But how often is this an issue?

Well, thing is this recent surge of activity in this never dying thread started with a video where this exact type of event is compiled.
And my point is that such accident is very unlikely to happen with commuter negotiating that roundabout 10 times a week - and I would buy  "force drivers to slow down" thing with respect to commuters. However for non-local drivers, roundabout with engineered limited visibility on approach and messy signs is quite conductive for the type of event.
And I would argue that such limiting visibility and often sign overload is pretty much today's trend. Need to know, access control, fake news,  all that crap.

On a bigger scale, it is actually an interesting question of designing for commuter vs design for a stranger. First time that occurred to me when I got slightly lost in MTA ticket machine controls, and few days later came across an article describing that design as optimized for long-term resident. Average NYCer can go through the process in like 10 second, as next step is always in a right spot; stranger may struggle and have to start over as "back" button is not even implemented. But that is still net benefit in terms of machine throughput due to local/stranger ratio.
Once I started to pay attention, I realized it is not an uncommon scenario...
Can it be that roundabouts are working the same way - reducing commuter accident rate at a cost of stranger accident rate? I wouldn't be surprised, but collecting statistics is quite difficult...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 17, 2017, 10:24:47 PM
Can it be that roundabouts are working the same way - reducing commuter accident rate at a cost of stranger accident rate? I wouldn't be surprised, but collecting statistics is quite difficult...

I have been convinced, pretty much since day one, that if we introduced more roundabouts, the average crash rate would drop when the data from all are compiled.

The only way I can think of figuring out who in a collision is a stranger or a commuter is to consider the address of the involved, and the time of the collision. If it's within, say 30 miles, and the collision occured during rush hours, there's a decent chance that it could be a "commuter". But there's no way to be sure. I don't think that's a statistic that you could collect, short of police directly inquiring. Of course, people wouldn't be required to answer the question.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 17, 2017, 11:11:40 PM
Can it be that roundabouts are working the same way - reducing commuter accident rate at a cost of stranger accident rate? I wouldn't be surprised, but collecting statistics is quite difficult...

I have been convinced, pretty much since day one, that if we introduced more roundabouts, the average crash rate would drop when the data from all are compiled.

The only way I can think of figuring out who in a collision is a stranger or a commuter is to consider the address of the involved, and the time of the collision. If it's within, say 30 miles, and the collision occured during rush hours, there's a decent chance that it could be a "commuter". But there's no way to be sure. I don't think that's a statistic that you could collect, short of police directly inquiring. Of course, people wouldn't be required to answer the question.
Small problem is that designs shouldn't be based on being convinced, personal beliefs, religion of parents and similar stuff. Data, understanding patterns, analyzing existing dependences and so on - that is a proper basis for the design.
As for assumption of stranger/commuter ratio.. First problem is figuring out ratio in every day traffic. I can see ways of doing that, but it is time and money..
But if (and that is just hypothetical if) assumption is correct, that should give a hint about some design criteria - like placement of roundabouts near  locations frequently visited by non-locals (tourist attractions, some government offices, hospitals..) should face additional scrutiny. Or considering changes in warning patterns. Or..
But I am wasting time - such details are probably beyond the level of competence  of most engineering workforce.
Title: Re: Crash prone 'modern roundabouts'
Post by: US 89 on June 18, 2017, 12:14:22 AM
At small intersections, roundabouts work great. They often enable more cars to get through the intersection and avoid huge lines forming behind a stop sign while the cars in front wait for a gap, often darting out in front of cross traffic and causing crashes.

That said, when you start having more than one lane in roundabouts, then things start to get messy. At one particular roundabout (https://goo.gl/EJfH5k) in my area, it seems that nobody can stay in their lane. (The lanes have been reconfigured since this image was taken, but it is still an issue.

The idea of a roundabout is even worse if the roundabout replaced a traffic signal. That automatically decreases the potential volume, since signals are designed to accomodate much more traffic than roundabouts can. (Exception: there was very little traffic and therefore no need for a signal.)

And no matter what, there will always be a few people who don't understand that you're supposed to yield to cars that are already in the roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 18, 2017, 04:00:09 PM
Many experts believe roundabouts should be safer than the intersections they are replacing.  And if a roundabout does have an excessive number of crashes it’s easy to blame it on poor signage, pavement markings, or deflection angles.  But their expectations about roundabout safety are largely based on an IIHS study done in 2000 — at a time when complex roundabouts were nearly non-existent.  Now agencies are building these complex 2x2 or 3x2 roundabouts believing they will be safer simply because they are a roundabout.   That is a dangerous mindset.   

Listen to Mark McCulloch’s remarks at the 5th International Conference on Roundabouts.  Mark is a project engineer for the Washtenaw County Road Commission and was the man behind the State & Ellsworth roundabout in Ann Arbor.  Before it was constructed he was cocky that the roundabout would work great.  Now reality has set in…

Quote
So my first roundabout that I put in was in 2007 and you know it’s going really well — we’re saving lives, we’re doing capacity, things are just going great, and then 2013 my nemesis showed up.  I did my first two lane 2-by-2 multi-lane roundabout with high capacities — we’re talking about 30,000 vehicles coming in and out of this thing.  And I remember sitting at a public forum and I’m telling 200 people that it’s just going to work great.  I’m sitting up there and I’m very confident, maybe even a little bit too cocky, and I’m saying how great it’s going to be, you’ll see.  And then the first year that it opened, the first full year that it was opened to traffic, we had 170 fender bender crashes at this roundabout. 

We had fifteen - um typically we had 15 injury crashes at this intersection when it was a traffic signal.  You know from a standpoint of capacity, from a standpoint of efficiency, from a standpoint of safety we won.  But I and no one else saw the 170 crashes coming.  We thought to ourselves it was one hiccup, they are going to get use to it.  There was a road closure on a major freeway project that we did a mile down the road and we utilized this roundabout as a detour, so I conveniently blamed that for the reason of the 170, and the next year it was 171.  Oops.  Nice job Mark.  So it forced me to say alright what can we do better, what’s going on, why is this happening, and what can we be doing?  And here it is, forever and ever in the state of Michigan in the calendar year 2015 - 2014 I believe it was - I have the most dangerous intersection in the state of Michigan.  So that’s forever on my resume. 

Slide #5:  http://teachamerica.com/RAB17/RAB1710A_McCulloch/index.htm

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 18, 2017, 07:44:47 PM
^^^

Wow. That's a pretty telling confession. I kind of feel bad for him. He was a little misled by the early stats, and the double lane roundabout was a new thing, so there was no way to know how it was going to operate. Unfortunately for him, it ended up performing rather poorly.

THAT SAID, there have to be at least a few double lane roundabouts in the US that perform reasonably well. Tradephoric, any idea where the safest double lane roundabout is in the US (at least from what you can tell from the data you've compiled)?
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on June 18, 2017, 10:09:41 PM
An interesting presentation from the 2011 roundabout conference on crash rates in areas familiar with roundabouts (Carmel, IN) vs areas unfamiliar.   Some multilane stats on slide 48.  http://teachamerica.com/RAB11/RAB1107Barbier/player.html
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on June 18, 2017, 10:17:05 PM
Speaking of multi-lane roundabouts, construction has started on two side-by-side roundabouts on Ottawa Street in Kitchener (one at Homer Watson Blvd, and one at Alpine Road). This is not far from the infamous Homer Watson/Block Line Roundabout. They're aiming to be finished by the fall (http://www.cbc.ca/news/canada/kitchener-waterloo/roundabout-construction-kitchener-ottawa-homer-watson-alpine-1.4127727). We'll have to wait and see if it ends up improving the Region's second worst intersection or not.
Title: Re: Crash prone 'modern roundabouts'
Post by: US 89 on June 18, 2017, 10:28:53 PM
Speaking of multi-lane roundabouts, construction has started on two side-by-side roundabouts on Ottawa Street in Kitchener (one at Homer Watson Blvd, and one at Alpine Road). This is not far from the infamous Homer Watson/Block Line Roundabout. They're aiming to be finished by the fall (http://www.cbc.ca/news/canada/kitchener-waterloo/roundabout-construction-kitchener-ottawa-homer-watson-alpine-1.4127727). We'll have to wait and see if it ends up improving the Region's second worst intersection or not.

The one at Homer Watson looks like a really busy intersection. Based on what has been posted, that sounds like it's going to be a bad move.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 18, 2017, 10:57:14 PM
Speaking of multi-lane roundabouts, construction has started on two side-by-side roundabouts on Ottawa Street in Kitchener (one at Homer Watson Blvd, and one at Alpine Road). This is not far from the infamous Homer Watson/Block Line Roundabout. They're aiming to be finished by the fall (http://www.cbc.ca/news/canada/kitchener-waterloo/roundabout-construction-kitchener-ottawa-homer-watson-alpine-1.4127727). We'll have to wait and see if it ends up improving the Region's second worst intersection or not.

The one at Homer Watson looks like a really busy intersection. Based on what has been posted, that sounds like it's going to be a bad move.

I don't think we've seen the end of gigantic, two and three lane roundabouts. Until we get a real research project going that involves several high-profile agencies, the only thing stopping more from popping up is an engineer's previous experience (e.g. Mark McCulloch probably won't be building any more multi-lane roundabouts).
Title: Re: Crash prone 'modern roundabouts'
Post by: US 89 on June 18, 2017, 11:11:23 PM
Speaking of multi-lane roundabouts, construction has started on two side-by-side roundabouts on Ottawa Street in Kitchener (one at Homer Watson Blvd, and one at Alpine Road). This is not far from the infamous Homer Watson/Block Line Roundabout. They're aiming to be finished by the fall (http://www.cbc.ca/news/canada/kitchener-waterloo/roundabout-construction-kitchener-ottawa-homer-watson-alpine-1.4127727). We'll have to wait and see if it ends up improving the Region's second worst intersection or not.

The one at Homer Watson looks like a really busy intersection. Based on what has been posted, that sounds like it's going to be a bad move.

I don't think we've seen the end of gigantic, two and three lane roundabouts. Until we get a real research project going that involves several high-profile agencies, the only thing stopping more from popping up is an engineer's previous experience (e.g. Mark McCulloch probably won't be building any more multi-lane roundabouts).

If the new crash rate is 11x what it was before, like the one in Michigan, then those engineers probably won't install any more.

As more and more engineers make these mistakes, less and less of these roundabouts will be built.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 19, 2017, 02:00:17 AM
Speaking of multi-lane roundabouts, construction has started on two side-by-side roundabouts on Ottawa Street in Kitchener (one at Homer Watson Blvd, and one at Alpine Road). This is not far from the infamous Homer Watson/Block Line Roundabout. They're aiming to be finished by the fall (http://www.cbc.ca/news/canada/kitchener-waterloo/roundabout-construction-kitchener-ottawa-homer-watson-alpine-1.4127727). We'll have to wait and see if it ends up improving the Region's second worst intersection or not.

The one at Homer Watson looks like a really busy intersection. Based on what has been posted, that sounds like it's going to be a bad move.

I don't think we've seen the end of gigantic, two and three lane roundabouts. Until we get a real research project going that involves several high-profile agencies, the only thing stopping more from popping up is an engineer's previous experience (e.g. Mark McCulloch probably won't be building any more multi-lane roundabouts).

If the new crash rate is 11x what it was before, like the one in Michigan, then those engineers probably won't install any more.

As more and more engineers make these mistakes, less and less of these roundabouts will be built.

There's two types of engineers (I'd reckon): the kind that do things once, and determine whether or not they'll do it again based on the feedback from that "thing", and the kind that do things over and over again until it's clear that something either works or doesn't.

The traffic engineer for a city near me replaced (roughly) ten protected lefts with flashing yellow arrows in 2006, and watched them for a year before he decided what he thought of them. They were a resounding success (reducing traffic congestion and collisions/injuries), and all remaining city-maintained single-lane protected lefts were replaced with FYAs over the next ten years.

He's the second kind of engineer, and that's a good thing: if he based his study on just one intersection, there'd be too many variables to be certain of any outcome. Installing many at once eliminates many of the location-based variables, such as sight distance, intersection size, TOD flow, etc. The first kind of engineer would have installed one or two, and based their future left turn signal designs entirely on the results of those two signals. I think that's just dumb. The sample size isn't big enough.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on June 19, 2017, 06:07:35 AM
Speaking of multi-lane roundabouts, construction has started on two side-by-side roundabouts on Ottawa Street in Kitchener (one at Homer Watson Blvd, and one at Alpine Road). This is not far from the infamous Homer Watson/Block Line Roundabout. They're aiming to be finished by the fall (http://www.cbc.ca/news/canada/kitchener-waterloo/roundabout-construction-kitchener-ottawa-homer-watson-alpine-1.4127727). We'll have to wait and see if it ends up improving the Region's second worst intersection or not.

The one at Homer Watson looks like a really busy intersection. Based on what has been posted, that sounds like it's going to be a bad move.

I don't think we've seen the end of gigantic, two and three lane roundabouts. Until we get a real research project going that involves several high-profile agencies, the only thing stopping more from popping up is an engineer's previous experience (e.g. Mark McCulloch probably won't be building any more multi-lane roundabouts).

If the new crash rate is 11x what it was before, like the one in Michigan, then those engineers probably won't install any more.

As more and more engineers make these mistakes, less and less of these roundabouts will be built.

There's two types of engineers (I'd reckon): the kind that do things once, and determine whether or not they'll do it again based on the feedback from that "thing", and the kind that do things over and over again until it's clear that something either works or doesn't.

The traffic engineer for a city near me replaced (roughly) ten protected lefts with flashing yellow arrows in 2006, and watched them for a year before he decided what he thought of them. They were a resounding success (reducing traffic congestion and collisions/injuries), and all remaining city-maintained single-lane protected lefts were replaced with FYAs over the next ten years.

He's the second kind of engineer, and that's a good thing: if he based his study on just one intersection, there'd be too many variables to be certain of any outcome. Installing many at once eliminates many of the location-based variables, such as sight distance, intersection size, TOD flow, etc. The first kind of engineer would have installed one or two, and based their future left turn signal designs entirely on the results of those two signals. I think that's just dumb. The sample size isn't big enough.

Not to mention when you install just one of something, there's a steep learning curve for motorists at that one intersection, which is unusual and abnormal from all the rest.  Many will encounter it on rare occasion, and it's possible they'll be confused when they reach it.  Do it at 11 intersections, and more people see them more often.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 19, 2017, 09:34:50 AM
THAT SAID, there have to be at least a few double lane roundabouts in the US that perform reasonably well. Tradephoric, any idea where the safest double lane roundabout is in the US (at least from what you can tell from the data you've compiled)?

The double-lane roundabout at County Road M & Valley View Road in Madison appears to be performing reasonably well.  But just a mile up the road there is a double-lane roundabout on Mineral Point Road with a relatively high crash rate (approaching 4.0 MEV).  I believe both roundabouts were built in 2010 so it could be interesting to compare the design of those two roundabouts.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBcrashrate_zpsl0dosxlc.png)

The average crash rate of signalized intersections is roughly 0.7 MEV.  Double-lane roundabouts (with 2x2 or 3x2 configurations) have average crash rates approaching 4.0 MEV.  Nearly 1 in 3 roundabouts on that list have had circulating lanes removed or they are planning to do so (roundabouts highlighted in yellow).  Even if you don’t believe the numbers, the fact that agencies are removing circulating lanes from so many of these complex roundabouts should indicate that there is indeed a problem.  And in all the research I’ve seen, when a circulating lane is removed the crash rate drops precipitously.  Conversely, when only “tweaks”  are made to a roundabout in attempt to reduce the crash rate (such as signage or lane marking changes), the reduction in crashes seems to only be temporary (the Bluffton Parkway roundabout in South Carolina comes to mind).
 
An interesting presentation from the 2011 roundabout conference on crash rates in areas familiar with roundabouts (Carmel, IN) vs areas unfamiliar.   Some multilane stats on slide 48.  http://teachamerica.com/RAB11/RAB1107Barbier/player.html

Communities with a high concentration of roundabouts aren’t immune to high crash rates.  While Carmel has an abundance of roundabouts, relatively few have complex geometries.  In fact, of the 100 roundabouts in Carmel not a single one has a 3x2 geometry. And the few 2x2 roundabouts in Carmel that exist have high crash rates.  The roundabout at 116th and Keystone is one of the worst performing intersections in the city with a crash rate over 5.0 MEV.  To put that into perspective, the roundabout at M-5 & Pontiac trail has the same crash rate as the 116th & Keystone roundabout, and that roundabout had the most crashes in Michigan in 2015.  The only reason 116th and Keystone Parkway isn’t winning “most crashes in the State”  awards is because it carries 20,000 fewer vehicles than the M-5 roundabout.
 
Over the past few years more complex roundabouts have been built in Carmel but it’s too early to see how well they are performing.  Unfortunately, the Carmel Police department no longer lists the highest crash intersections in their annual reports, so it’s harder to pin down numbers on recently constructed roundabouts.  Too bad the city of Carmel isn’t being as transparent as they once were.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 19, 2017, 10:25:42 AM
Communities with a high concentration of roundabouts aren’t immune to high crash rates.  While Carmel has an abundance of roundabouts, relatively few have complex geometries.  In fact, of the 100 roundabouts in Carmel not a single one has a 3x2 geometry. And the few 2x2 roundabouts in Carmel that exist have high crash rates.  The roundabout at 116th and Keystone is one of the worst performing intersections in the city with a crash rate over 5.0 MEV.  To put that into perspective, the roundabout at M-5 & Pontiac trail has the same crash rate as the 116th & Keystone roundabout, and that roundabout had the most crashes in Michigan in 2015.  The only reason 116th and Keystone Parkway isn’t winning “most crashes in the State”  awards is because it carries 20,000 fewer vehicles than the M-5 roundabout.
 
An interesting safety metrics for a given community is average insurance rate - which is published online. Interestingly enough, Carmel is lower than neighbors; not much - but noticeable.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 19, 2017, 10:29:41 AM
Speaking of multi-lane roundabouts, construction has started on two side-by-side roundabouts on Ottawa Street in Kitchener (one at Homer Watson Blvd, and one at Alpine Road). This is not far from the infamous Homer Watson/Block Line Roundabout. They're aiming to be finished by the fall (http://www.cbc.ca/news/canada/kitchener-waterloo/roundabout-construction-kitchener-ottawa-homer-watson-alpine-1.4127727). We'll have to wait and see if it ends up improving the Region's second worst intersection or not.

The one at Homer Watson looks like a really busy intersection. Based on what has been posted, that sounds like it's going to be a bad move.

I don't think we've seen the end of gigantic, two and three lane roundabouts. Until we get a real research project going that involves several high-profile agencies, the only thing stopping more from popping up is an engineer's previous experience (e.g. Mark McCulloch probably won't be building any more multi-lane roundabouts).

If the new crash rate is 11x what it was before, like the one in Michigan, then those engineers probably won't install any more.

As more and more engineers make these mistakes, less and less of these roundabouts will be built.
A smart person is the one who can learn from their mistakes
A wise person is the one who can learn from mistakes others made
Some people don't learn from neither their own mistakes nor mistakes others made...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 19, 2017, 06:18:36 PM
THAT SAID, there have to be at least a few double lane roundabouts in the US that perform reasonably well. Tradephoric, any idea where the safest double lane roundabout is in the US (at least from what you can tell from the data you've compiled)?

The double-lane roundabout at County Road M & Valley View Road in Madison appears to be performing reasonably well.  But just a mile up the road there is a double-lane roundabout on Mineral Point Road with a relatively high crash rate (approaching 4.0 MEV).  I believe both roundabouts were built in 2010 so it could be interesting to compare the design of those two roundabouts.

The thing that sticks out to me are the slip lanes at the CR-M/Valley View roundabout.

Out of curiosity, do AADT numbers count those that turn right via slip lanes?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 19, 2017, 07:01:38 PM
^^^
The AADT numbers would include the right turn counts via the slip lanes.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 19, 2017, 07:45:23 PM
^^^
The AADT numbers would include the right turn counts via the slip lanes.

Makes sense. I'd like to see the safety numbers for a roundabout where all the right turn slip lanes are protected (followed by a merge or something).

Is it possible that the separation of the right turn lane from the straight/left lanes may have improved sightlines? Nevermind the slip lane traffic going from north to northwest (at the Valley View/CR-M roundabout outside of Madison, WI) that don't conflict with the circle at all.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 19, 2017, 08:11:35 PM
Makes sense. I'd like to see the safety numbers for a roundabout where all the right turn slip lanes are protected (followed by a merge or something).

The Rte. 101/Winchester Street roundabout in Keene has protected right turn slip lanes for all approaches.   There was a head on crash near the roundabout about a month ago that injured 2 people.

Two taken to hospital after head-on crash near Keene roundabout

http://www.sentinelsource.com/news/local/two-taken-to-hospital-after-head-on-crash-near-keene/article_1130b673-283f-5724-88b8-93108b6eeb97.html

Someone apparently caught the crash on dashcam... 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 19, 2017, 08:29:33 PM
Makes sense. I'd like to see the safety numbers for a roundabout where all the right turn slip lanes are protected (followed by a merge or something).

The Rte. 101/Winchester Street roundabout in Keene has protected right turn slip lanes for all approaches.   There was a head on crash near the roundabout about a month ago that injured 2 people.

Ooooookay. So maybe slip lanes don't protect against drifting after you leave a roundabout, but maybe they help prevent right turn crashes, where somebody turning right fails to give way, or maybe where their visibility wasn't good, so they just went and hoped for the best?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 20, 2017, 11:42:31 AM
Here is an example of a multi-lane roundabout in Milton Keynes, UK. 

https://www.google.com/maps/@52.0416474,-0.7445147,95m/data=!3m1!1e3

This is the type of complex roundabout that seems so problematic for American drivers.  There are literally dozens more roundabouts just like this in Milton Keynes and many have minimal signage/pavement markings to direct traffic through the roundabout.  Truck aprons are nearly non-existent and there is no overhead signs to direct traffic what lane to be in when navigating the roundabout.  Here is an example of a roundabout where there are no visible pavement markings in the circle at all.

https://www.google.com/maps/@52.0443739,-0.7637102,95m/data=!3m1!1e3

I’m not suggesting that roundabouts with minimal pavement markings and directional signs are safer than roundabouts without them.  It just seems like the UK isn’t hung up on every little design element.  It’s a circle, and drivers circulate through it the best they can without hitting another vehicle.  So the question becomes how many crashes are occurring at these complex Milton Keynes roundabouts and what are the daily traffic volumes?  Do the crash rates of these UK roundabouts compare to the complex roundabouts found in America? 
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on June 20, 2017, 12:36:23 PM
I’m not suggesting that roundabouts with minimal pavement markings and directional signs are safer than roundabouts without them.  It just seems like the UK isn’t hung up on every little design element.  It’s a circle, and drivers circulate through it the best they can without hitting another vehicle.
Yes - this is what I've been banging on about. The problem is that America is very prescriptive - do this, do that. Whereas the UK puts more onus on the driver, only guiding them and telling them not to do stuff (though we're changing to a more nannying principle and our crash rate improvements has flattened out).
Quote
So the question becomes how many crashes are occurring at these complex Milton Keynes roundabouts and what are the daily traffic volumes?  Do the crash rates of these UK roundabouts compare to the complex roundabouts found in America?
I think upthread I did one.

Brinklow Roundabout is a 3-lane roundabout with 70mph dual carriageway arms carrying traffic volumes (2016 figures taken from nearby count points) as follows
A421W: 25941
A421E: 28760
A4146N: 30485
A4146S: 20516
which, as everyone will use 2 legs and be counted twice, giving an average traffic on the circulatory carriageway of 52851/day (2004 figures of 23840+19921+30449+18762/2 = 46486)

I can't find any RTC data, but in 2002, they reduced visibility on the approaches to increase safety and it worked.
Quote from: MK LTP 2006 (https://www.milton-keynes.gov.uk/assets/attach/1485/Milton_Keynes_LTP_Delivery_Report_July_2006.pdf)
A re-engineered junction on Barnsdale Drive and Tattenhoe, a gap closure on Avebury/Elder Gate, removal of a right hand turn from Grafton Street into Walgrave Drive and installing of visibility barriers on approach to Brinklow roundabout have so far resulted in no serious injuries or fatalities and only 40 slight injuries. Over the three years prior to implementation between 2000 and 2002, there were 11 serious and 96 slight injuries, indicating that in total these schemes have successfully reduced casualties.

Lets say that all those 40 slight injuries happened in 2004, rather than over the three-year 2003-05 period (to really tilt the table against MK), and at that roundabout, rather than also at the other junctions. That gives 17013876 vehicles passing and 40 injury crashes - an injury crash every 425347 vehicle entries is a rate of 2.35MEV.

Edit: I've found a not that useful way of finding it: http://www.crashmap.co.uk/search This covers all crashes. On the roundabout and it's approaches (where most rtas are clustered (we'll go to the bus stops on each approach), there are 51 recorded incidents, but this covers the 5 year period from 01/01/12 to 31/12/16. All but 1 are slight, though no damage only incidents are included (as seems to be the case with UK statistics).

Even putting that whole 5 years of injury crashes into 2016, that's 2.63MEV.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 20, 2017, 01:49:39 PM
Edit: I've found a not that useful way of finding it: http://www.crashmap.co.uk/search This covers all crashes. On the roundabout and it's approaches (where most rtas are clustered (we'll go to the bus stops on each approach), there are 51 recorded incidents, but this covers the 5 year period from 01/01/12 to 31/12/16. All but 1 are slight, though no damage only incidents are included (as seems to be the case with UK statistics).

That link is incredibly useful!  As you mentioned the data doesn’t appear to include damage only incidents.  This is confirmed when reading about the data on the website:

Quote
CrashMap uses data collected by the police about road traffic crashes occurring on British roads where someone is injured which is then compiled in to an easy to use format showing each incident on a map. This data is approved by the National Statistics Authority and reported on by the Department for Transport each year. Northern Ireland data is not provided proactively and has been obtained through an FoI request. Incidents are plotted to within 10 metres of their location and as such, can sometimees appear to be off the carriageway when zoomed in very closely.

I zoomed into one of the Milton Keynes roundabouts I linked in my above post to see how many injury crashes there were over the past 5 years:
https://www.google.com/maps/@52.0416474,-0.7445147,95m/data=!3m1!1e3

The Childs Way / Marlborough St roundabout had 15 injury crashes over a 5 year period (14 slight, 1 serious).  Now do you know of a good resource to find traffic volumes on British roadways?  Then we can nail down injury crash rates for these British roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: ScottRAB on June 20, 2017, 03:29:53 PM
Many people confuse other and older styles of circular intersections with modern roundabouts. East coast rotaries, large multi-lane traffic circles (Arc D’Triomphe, Dupont Circle), and small neighborhood traffic circles are not modern roundabouts. If you want to see the difference between a traffic circle, a rotary (UK traffic roundabout) and a modern roundabout (UK continental roundabout).
Go to  http://www.k-state.edu/roundabouts/photos.htm to see pictures. 
The Brits even call a merry-go-round a kid’s roundabout.

The US and UK introduced circular intersections in the early 20th century.  The US and UK adopted widespread use of rotaries in the 40's and 50's and while both countries found them to be less than ideal, the US walked away from them while the UK kept on tinkering. The offside priority rule (yield on entry) and smaller size with deflection on entry are the key operational and design changes developed by the British. The French and Aussies have applied them more than the US. We're essentially importing the refined, safer grandchild of the east coast rotary, thus the preferred name modern roundabout. Look up Frank Blackmore.

Roundabout History
Frank Blackmore:  https://en.wikipedia.org/wiki/Frank_Blackmore
https://www.theguardian.com/theguardian/2008/jun/21/6
http://www.mini-roundabout.com/tribute.htm
https://supernet.isenberg.umass.edu/visuals/FOMgt341-F10/Rotaries%20vs%20Roundabouts.pdf
http://rodel-interactive.com/about/capacity.html
http://www.economist.com/news/europe/21697235-invented-britain-modern-traffic-circles-invade-frances-hexagon-french-revolution
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on June 20, 2017, 03:48:00 PM
Now do you know of a good resource to find traffic volumes on British roadways?  Then we can nail down injury crash rates for these British roundabouts.
If the arms are A roads, then http://www.dft.gov.uk/traffic-counts/, otherwise there's typically only stuff for a specific study if there is one.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on July 08, 2017, 12:52:58 PM
A little "red meat" for the Carmel roundabout haters...  Injury accidents continue to decline in Carmel despite population growth (http://currentincarmel.com/injury-accidents-continue-to-decline-in-carmel-despite-population-growth)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 08, 2017, 01:20:44 PM
A little "red meat" for the Carmel roundabout haters...  Injury accidents continue to decline in Carmel despite population growth (http://currentincarmel.com/injury-accidents-continue-to-decline-in-carmel-despite-population-growth)
Glass can be half-full or half-empty.
Lets try flip it around,... Total number of injury incidents in Carmel is flat over past 20 years while US saw 30% drop! Roundabouts INURE people!
Proper analysis is often more involved. They gamble on population growth over the period - but what does it tell about traffic? Not much. How many transit vehicles are there for those just going through the town? Is it possible that drivers literally go extra mile not to struggle with roundabouts? Any new highways so traffic avoids intersections?
Of course, that is too complicated for most traffic engineers...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 08, 2017, 05:22:30 PM
Here is a link to the 2016 Carmel Police Department Annual report so you can analyze the data for yourself: 

http://carmel.in.gov/Modules/ShowDocument.aspx?documentID=8375

In previous years the Carmel Police Department Annual Repots would provide a map of the highest crash intersections in the city.  Starting in 2015 they omitted this map, and readers can no longer determine what intersections in Carmel are experiencing the most crashes.  If anybody has another resource to track crashes at Carmel intersections, that would be useful info.

Any new highways so traffic avoids intersections?

That’s a good point.  Over the past decade Carmel has converted heavily traveled surface streets (Keystone Parkway and Meridian Street) to grade-separated highways.  A lot of Carmel drivers bypass the major intersections that they once had to travel through.  It’s hard to get t-boned on a highway.  Brainard attributes the decrease in the accident rate to the city’s investment in roundabouts, but it could be due to the major surface streets in the city being converted to grade-separated highways.
Title: Re: Crash prone 'modern roundabouts'
Post by: UCFKnights on July 09, 2017, 01:11:21 AM
I was in Gainesville, Florida recently, and as part of the new development and bridge over I-75, they put in a really weird two lane roundabout, that seems like it will be very accident prone once it gets any traffic. One leg exits into another roundabout, one leg to a stop sign about 10 feet forward of the exit, and one leg comes in from the 2 lane bridge. The signage is also wrong on the bridge approach indicating what each lane does, and even though its a two lane roundabout, the bridge leg is the only one that is 2 lanes.

No pictures on google maps yet, but especially considering they had a completely fresh slate on both sides of the bridge with all empty lane, and all new roads, its hard to envision why anyone would design it like this.

I still stand by my opinion of being a fan of single lane roundabouts (especially to replace any intersection controlled by a stop sign), but strongly against multilane roundabouts as there seems to be just about no way to get Americans to understand the lane use in them, making crashes inevitable.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 20, 2017, 11:31:48 AM
Carmel awards $28.8M contract for 96th and Keystone roundabout
https://www.ibj.com/articles/64656-carmel-awards-288m-contract-for-96th-and-keystone-roundabout

The headline doesn't mention that 96th and Keystone is being converted from a standard intersection to a full blown grade-separated interchange.  They are so roundabout obsessed in Carmel that the headline focuses on the on/off ramp roundabouts and make no mention the grade-separated interchange.   The roundabouts being proposed at 96th and Keystone have a similar design to the existing roundabouts at 116th and Keystone (which has one of the highest crash rates in Carmel with a crash rate over 5.0 MEV).
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on July 20, 2017, 12:09:47 PM
Carmel awards $28.8M contract for 96th and Keystone roundabout
https://www.ibj.com/articles/64656-carmel-awards-288m-contract-for-96th-and-keystone-roundabout

They are so roundabout obsessed in Carmel that the headline focuses on the on/off ramp roundabouts and make no mention the grade-separated interchange.

Well, except in the very first sentence.  And in the graphic below the very first sentence.

And I think there's someone much more roundabout obsessed than this town or newspaper.

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 20, 2017, 01:21:05 PM
Carmel awards $28.8M contract for 96th and Keystone roundabout
https://www.ibj.com/articles/64656-carmel-awards-288m-contract-for-96th-and-keystone-roundabout

They are so roundabout obsessed in Carmel that the headline focuses on the on/off ramp roundabouts and make no mention the grade-separated interchange.

Well, except in the very first sentence.  And in the graphic below the very first sentence.

And I think there's someone much more roundabout obsessed than this town or newspaper.



Yeah, but it's not in the headline. A lot of people will read a headline and nothing else.  They are so roundabout obsessed that a major $28.8 million dollar interchange project is viewed as a "roundabout" project.  Yeah, it's the "roundabouts" that are improving traffic flow on Keystone Parkway (nothing to do with the grade-separation right?).  Also it's very likely there will be more crashes at the interchange roundabouts than the surface intersection they are replacing (just like there were when 116th & Keystone was converted to a grade-separated interchange).  But somehow it will be viewed as a success because there are bunch of ideologues running that city who believe roundabouts are always the best option... to the point where the mayor of Carmel is proposing every traffic signal in the city be converted to a roundabout.  The mayor is obsessed.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 20, 2017, 04:59:22 PM
The rest of Keystone is a freeway. If it's locals that are reading the story, I think they'll known straight-away that it's going to be an interchange.

But, in the event that maybe they don't...

Quote
roundabout interchange
Quote
construction of the roundabout interchange
Quote
traffic on Keystone will travel over 96th Street
Quote
The intersection is the only one along the Keystone corridor in Carmel that hasn’t been upgraded to an elevated roundabout
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 20, 2017, 08:56:54 PM
The rest of Keystone is a freeway. If it's locals that are reading the story, I think they'll known straight-away that it's going to be an interchange.

But, in the event that maybe they don't...

Quote
roundabout interchange
Quote
construction of the roundabout interchange
Quote
traffic on Keystone will travel over 96th Street
Quote
The intersection is the only one along the Keystone corridor in Carmel that hasn’t been upgraded to an elevated roundabout

Sounds like Fake News Jake.  CNN did some propaganda piece on Carmel's roundabouts...

CNN: Very Fake News


Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 20, 2017, 09:00:55 PM
(http://i.imgur.com/BFQBW.gif)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 24, 2017, 01:39:40 PM
Why an Indiana City is Totally Obsessed with Roundabouts:  When is a circle better than an X?
https://www.inverse.com/article/34337-carmel-indiana-might-forever-be-america-s-roundabout-kingdom

Quote
Circles and Cyclists May Not Mix

It was safety stats like these that allowed modern traffic circles to hop the pond and find a home in cities like Carmel. But in recent years, many English cities have been paving over their roundabouts, in part because of the damage this design seems to pose to cyclists.

While the statistics about driver safety may still ring true, a 2008 study in the journal Accident Analysis & Prevention found that turning a traffic signal into a roundabout actually increased a cyclist’s risk of injury by 27 percent. Reduced speeds can reduce damage, but even helmet-wearing cyclists aren’t totally protected from the full force of a car going 25 miles an hour. This study isn’t the last word, of course, and many cities continue to report improved safety for cyclists in roundabouts over traditional intersections, but this and other concerning data has been enough to spur some urban planners to reconsider.

Other research, like the fact that there isn't a documented 2x2 roundabout in America with a crash rate below 1.0 MEV.  Every complex geometry roundabout where crash data is available has an unacceptably high crash rate.  It's quite amazing that there isn't even one outlier, where the crash rate could be viewed as acceptable.

Quote
Christine Scales, a city-county councillor representing neighboring Indianapolis, which shares more than a few roads with Carmel, tells Inverse that some intersections are just better without a roundabout.

“I have no opposition to roundabouts when their location is considered in a judicious manner,”  Scales says. And yet she opposes Carmel’s mayor in his attempted expansion of the roundabout program. “I believe he has convinced himself of the safety of roundabouts, as well as their benefit of enhancing traffic flow,”  she says. “[But] because he does not appear to evaluate each intersection as to the cost-benefit of replacing a traditional intersection, he has run into some problems.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 24, 2017, 02:18:30 PM
Listen to the first thing Mayor James Brainard said relating to roundabouts in that CNN piece:  “Roundabouts work everywhere” .  Luckily not everyone is as indoctrinated as Mayor Brainard.  Arizona State University found that double lane roundabouts in their state saw a 62% increase in total accidents, a 60% increase in damages, and only a 16% drop in injuries. 

Link to Arizona State University study:
https://repository.asu.edu/attachments/170314/content/Souliman_asu_0010N_15713.pdf

ADOT may replace roundabouts with diverging-diamond interchange design
http://www.azcentral.com/story/news/local/phoenix-traffic/2017/07/19/adot-may-replace-roundabouts-diverging-diamond-design-interchange/490345001/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 25, 2017, 10:32:15 AM
Council, residents speak against roundabout plans
http://www.ricentral.com/nk_standard_times/news/local_news/council-residents-speak-against-roundabout-plans/article_a7042b7a-6d6c-11e7-a959-2b0b9a38eba6.html

So this roundabout is being opposed by residents and city counsel, but listen to the outlandish claim made back in 2012 about the safety of roundabouts by someone from RIDOT.
 
Quote
RIDOT’s Robert Rocchio also said in 2012 that the roundabout was being envisioned as the town prepared for the Rolling Greens development.

“Whether it occurs or doesn’t occur, we want to make sure our improvements could accommodate that,”  he said in 2012. “Roundabouts are much safer than signals, it is proven. They reduce up to 90 percent of crashes.”  

No Robert Rocchio there is not a 90% reduction in crashes at roundabouts.  And it hasn't been proven that there is a 90% reduction in fatalities (if that is what you indeed meant to say).  If you actually read the 2000 IIHS study that made the claim that roundabouts reduce fatalities by 90%, they basically admit that it's a fabricated number...

Quote
Effects on fatal crashes and those causing incapacitating injuries are more difficult to measure due to the small samples, but indications are that such crashes were substantially reduced. For the 20 converted intersections with injury data, there were 3 fatal crashes during the before period and none during the after period. The fatal crashes may have contributed to the fact that the roundabouts were constructed and may therefore contribute to the regression-to-the-mean phenomenon.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 26, 2017, 01:34:55 PM
Controversy revolving around Shawnee Roundabout
http://www.hometownstations.com/story/35968348/controversy-revolving-around-shawnee-roundabout

Quote
In the 23 months prior to construction beginning at Shawnee and Ft. Amanda Road, 27 vehicle accidents occurred at the location. Since the completion of the roundabout, 61 vehicle accidents took place.

Engineer's comment:
Quote
“It's moving traffic very efficiently. There's little to no back-ups," states Rhodes. "Because of that, the people in the area that use it on a daily basis report to me that they love it.”

Police Chief's comment:
Quote
It is a burden on our manpower and resources. There's no question about it. Nobody working here is really happy about that," says Shawnee Township Police Chief Mike Keith. "For one, for the expenses and costs of people involved in accidents. Two, for the manpower and resources we direct toward that.”

“We suggested one lane. A lot of our accidents are people changing lanes in the round about, which is not permitted. Doesn't stop the accident from occurring. And trucks and buses can't really stay in one lane making that shoulder curve,”  states Chief Keith.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 26, 2017, 02:46:08 PM
How often do you send your data to engineers?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 27, 2017, 08:43:24 AM
ANother small non-injury accident on a roundabout: truck with hot tar rolled over on one of the roundabots in Malta - the road in question has a chain of 7.
Previously those circles made to the top of Trade's list of bad guys, and one of them made it to the list of 20 most dangerous intersections in the area as published by local insurance company. But that all is a small price to pay for your safety!
http://cbs6albany.com/news/local/traffic-alert-tanker-rollover-at-exit-12
(http://static-18.sinclairstoryline.com/resources/media/12aaf405-0e4e-43dd-b518-e78170c73750-large16x9_12tankerrollTogaOESPic.jpg_frame_0.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: hm insulators on July 27, 2017, 12:14:33 PM
That's one way to resurface a roadway! :-D
Title: Re: Crash prone 'modern roundabouts'
Post by: hm insulators on July 27, 2017, 01:55:43 PM
A few days ago, I was exercising my shoulder at the physical therapist's office (a word of advice: never dislocate a shoulder and/or tear a rotator cuff) and the TV was tuned to a station that showed a diverging-diamond intersection either already in place at some freeway/surface-street interchange or about to be installed (the sound was off) and it showed a video of how a diverging diamond intersection works. I watched it and said, "I definitely like that better than these stupid roundabouts that having been cropping up!"
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on July 27, 2017, 02:05:34 PM
ANother small non-injury accident on a roundabout: truck with hot tar rolled over on one of the roundabots in Malta - the road in question has a chain of 7.
Previously those circles made to the top of Trade's list of bad guys, and one of them made it to the list of 20 most dangerous intersections in the area as published by local insurance company. But that all is a small price to pay for your safety!
http://cbs6albany.com/news/local/traffic-alert-tanker-rollover-at-exit-12
(http://static-18.sinclairstoryline.com/resources/media/12aaf405-0e4e-43dd-b518-e78170c73750-large16x9_12tankerrollTogaOESPic.jpg_frame_0.png)

While that does suck, we can find rollover truck accidents that have occurred everywhere.  Why the insistence of nitpicking when they happen on a roundabout?  I've yet to see anyone say we need to eliminate all curves because of a single truck rollover.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 27, 2017, 02:19:01 PM
Tradephoric: dumbell/roundabout interchange or diverging diamond interchange?
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on July 27, 2017, 02:31:15 PM
Tradephoric: dumbell/roundabout interchange or diverging diamond interchange?

Parclo B.  Everytime.  Regardless of the circumstances.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 27, 2017, 02:36:21 PM
Tradephoric: dumbell/roundabout interchange or diverging diamond interchange?

Parclo B.  Everytime.  Regardless of the circumstances.

Oh, right. I've heard they're great for signal progression. Not so much for safety. But who cares about safety?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 27, 2017, 02:45:03 PM
ANother small non-injury accident on a roundabout: truck with hot tar rolled over on one of the roundabots in Malta - the road in question has a chain of 7.
Previously those circles made to the top of Trade's list of bad guys, and one of them made it to the list of 20 most dangerous intersections in the area as published by local insurance company. But that all is a small price to pay for your safety!
http://cbs6albany.com/news/local/traffic-alert-tanker-rollover-at-exit-12
(http://static-18.sinclairstoryline.com/resources/media/12aaf405-0e4e-43dd-b518-e78170c73750-large16x9_12tankerrollTogaOESPic.jpg_frame_0.png)

While that does suck, we can find rollover truck accidents that have occurred everywhere.  Why the insistence of nitpicking when they happen on a roundabout?  I've yet to see anyone say we need to eliminate all curves because of a single truck rollover.
Because harsh sequential curves of roundabouts, along with design pushing trucks to uneven inner circle are very likely a contributing factor in this accident. Ideology of roundabout, when traffic never has a right of way on entry, makes maneuvering that is relatively easy for cars somewhat difficult for heavy trucks, which often struggle with proper acceleration, which is required for proper navigation of roundabouts. Wouldn't be surprised that entry at higher rate of speed is a contributing factor - but required to avoid accidents with cars sneaking by.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 27, 2017, 04:25:54 PM
Tradephoric: dumbell/roundabout interchange or diverging diamond interchange?

That’s like asking me to pick my favorite type of broccoli.  Both the dumbbell roundabout and DDI kill good signal progression along Happy Valley Road, making driving along Happy Valley Road less happy for drivers.

Oh, right. I've heard they [Parclo B4s] are great for signal progression. Not so much for safety. But who cares about safety?

I encountered the dangers of freeway exiting loop ramps about a year ago.  The guy infront of me exited a freeway loop ramp at about 80 mph and didn’t even tap his brakes.  But the interchange in question wasn’t a Parclo B4.  The fact is there are hundreds - probably thousands - of interchanges in America that include exiting loop ramps.  Even today many freeway interchanges are being designed with exiting loop ramps.  If you have a problem with the safety of exiting loop ramps on freeways, then there are a lot of different interchange designs you can focus on.

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 27, 2017, 06:03:12 PM
While that does suck, we can find rollover truck accidents that have occurred everywhere.  Why the insistence of nitpicking when they happen on a roundabout?  I've yet to see anyone say we need to eliminate all curves because of a single truck rollover.

The Herb Gray Parkway roundabout outside Windsor, Ontario had 4 trucks rollover from April 2015 to August 2015.  That’s right - 4 truck rollovers in 5 months.  What signalized intersection has seen 4 trucks rollover over a 5 month period?  There are roughly 300,000 traffic signals in America compared to about 5,000 roundabouts.  With 300,000 traffic signals to choose from, surely you can find a traffic signal that averages a rollover a month.

Apr 22, 2015:  All lanes open after another roundabout rollover at Highway 3
http://www.cbc.ca/news/canada/windsor/all-lanes-open-after-another-roundabout-rollover-at-highway-3-1.3043578

May 20, 2015:  The Star's View: Warn truckers of traffic circle tipping hazard
http://windsorstar.com/uncategorized/warn-truckers-of-traffic-circle-tipping-hazard

August 4, 2015:Transport rollover at Howard Avenue and Highway 401
http://windsorstar.com/news/transport-rollover-at-howard-avenue-and-highway-401
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 27, 2017, 06:10:47 PM
Tradephoric: dumbell/roundabout interchange or diverging diamond interchange?

That’s like asking me to pick my favorite type of broccoli.  Both the dumbbell roundabout and DDI kill good signal progression along Happy Valley Road, making driving along Happy Valley Road less happy for drivers.

What interchange do you think would be superior? I don't think a regular diamond would be any good. Maybe a SPUI? A B4 Parclo could fit in the space, honestly.

How do roundabouts kill good signal progression? Roundabouts seem to process what's thrown at them pretty well (though I know some use metering due to the large amount of entering traffic from one direction). DDI's seem far worse to me.

Oh, right. I've heard they [Parclo B4s] are great for signal progression. Not so much for safety. But who cares about safety?

I encountered the dangers of freeway exiting loop ramps about a year ago.  The guy infront of me exited a freeway loop ramp at about 80 mph and didn’t even tap his brakes.  But the interchange in question wasn’t a Parclo B4.  The fact is there are hundreds - probably thousands - of interchanges in America that include exiting loop ramps.  Even today many freeway interchanges are being designed with exiting loop ramps.  If you have a problem with the safety of exiting loop ramps on freeways, then there are a lot of different interchange designs you can focus on.

I was mostly being facetious. I just remember you mentioning them being less popular with DOTs due to a perceived danger with exiting loops.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 27, 2017, 06:19:21 PM
While that does suck, we can find rollover truck accidents that have occurred everywhere.  Why the insistence of nitpicking when they happen on a roundabout?  I've yet to see anyone say we need to eliminate all curves because of a single truck rollover.

The Herb Gray Parkway roundabout outside Windsor, Ontario had 4 trucks rollover from April 2015 to August 2015.  That’s right - 4 truck rollovers in 5 months.

Which makes me wonder, more than anything else: why do all of our roundabouts have truck aprons? Why not just have the circulating lane (the actual circle) be two lanes wide, with a short inner curb that trucks could run over if absolutely necessary? Seems to me that the truck apron indirectly contributes to rollover crashes (certainly not helping if a truck enters faster than they should).

Some of Washington's older roundabouts have this design:

(2005) Cordata Parkway Roundabout(s), Bellingham -- photo from Reid Middleton (http://www.reidmiddleton.com/awards/2005-project-year-transportation-less-2-million/):
(http://www.reidmiddleton.com/wp-content/uploads/2016/07/Awards-HeroImage-CordataParkwayRBBellingham-1024x785.jpg)

(2002) Tester Road Roundabout, Monroe:
(http://i.imgur.com/pL23UXa.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 27, 2017, 06:49:36 PM

Which makes me wonder, more than anything else: why do all of our roundabouts have truck aprons? Why not just have the circulating lane (the actual circle) be two lanes wide, with a short inner curb that trucks could run over if absolutely necessary? Seems to me that the truck apron indirectly contributes to rollover crashes (certainly not helping if a truck enters faster than they should).
If you ask me: there shouldn't be any extra lanes, which do not have proper entrance/exit ports associated with them for car navigation reasons. Trucks in tight turns need extra room. If you ever saw 53' navigating tight 2-lane intersection...
Now making those extra lanes flush with roadway invites traffic... So you need to have that cake and eat it too. Outcome? You're hungry and have no cake...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 27, 2017, 09:07:59 PM

Which makes me wonder, more than anything else: why do all of our roundabouts have truck aprons? Why not just have the circulating lane (the actual circle) be two lanes wide, with a short inner curb that trucks could run over if absolutely necessary? Seems to me that the truck apron indirectly contributes to rollover crashes (certainly not helping if a truck enters faster than they should).

If you ask me: there shouldn't be any extra lanes, which do not have proper entrance/exit ports associated with them for car navigation reasons.

Sorry, what I meant was one lane that was roughly 20-24 feet wide. Not two marked lanes with no apron.

Not sure if that changes your response, though.



Tradephoric, have you seen this story? http://www.dailymail.co.uk/news/article-2639400/Australian-roundabouts-dangerous-world.html

Quote
[A] report...released by Austroads last week, found that the design of Australian roundabouts encouraged drivers to speed through intersections and to ”˜look but not see’ other motorists

Australian roundabouts are built according to a tangential design, which means that the driver has very good visibility as they approach the roundabout and is less likely to slow down, or check the roundabout closely as they approach the intersection.

European radial design left, Australian (and American) tangential design right:
(http://i.dailymail.co.uk/i/pix/2014/05/26/article-0-1E3697ED00000578-768_634x310.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 27, 2017, 10:17:11 PM

Which makes me wonder, more than anything else: why do all of our roundabouts have truck aprons? Why not just have the circulating lane (the actual circle) be two lanes wide, with a short inner curb that trucks could run over if absolutely necessary? Seems to me that the truck apron indirectly contributes to rollover crashes (certainly not helping if a truck enters faster than they should).

If you ask me: there shouldn't be any extra lanes, which do not have proper entrance/exit ports associated with them for car navigation reasons.

Sorry, what I meant was one lane that was roughly 20-24 feet wide. Not two marked lanes with no apron.

Not sure if that changes your response, though.
It doesn't matter if that affects my response, it does matter if it affect driver behavior  :bigass:.

And what I would expect.... I go through one of roundabouts daily; I approach from the side where 1 lane splits into two: one dedicated right turn, one option lane for through traffic and left turn. Everything is marked, signed, labeled... Once or twice a week I see someone trying to continue through  by going into dedicated right lane (and frankly speaking, that means a less wavy drive).   usually they realize and yield to traffic in proper lane, but once a month I see a close call.
Now what you suggest is a similar design without pavement marks and designated lanes...  I expect this to be a non-stop close call...

One possibility would be using two-color pavement (and that is  what they do anyway) - in a level layout, not elevated apron. That may work...  if weather is fine. Rainy nights, snow - not so much.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 27, 2017, 10:23:11 PM
I agree that the straighter the line, the higher the speed, chance for collision, etc. But if we designed our roundabouts with a less tangential entry (see above), maybe we'd see lower speeds? An entry with more of a right turn?

While the Dutch are heavy users of truck aprons, they use this "right turn to enter" approach at most, if not all new roundabouts:

image from Urban Design NL (Twitter (https://twitter.com/projectsfromnl)):
(https://pbs.twimg.com/media/CGunBnSXEAAsrE-.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on July 28, 2017, 05:43:32 AM
kill good signal progression
If anyone wants to know where tradephoric got his initial dislike of roundabouts, it is his love of good signal progression and roundabouts changing that.

Of course, if you do a Carmel, then signal progression doesn't matter as there very few signals.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 28, 2017, 08:08:30 AM
I agree that the straighter the line, the higher the speed, chance for collision, etc. But if we designed our roundabouts with a less tangential entry (see above), maybe we'd see lower speeds? An entry with more of a right turn?

While the Dutch are heavy users of truck aprons, they use this "right turn to enter" approach at most, if not all new roun
Well. two things: tangential approaches often include wavy patterns to begin with - although I suspect that is a result of DUI (Design Under Influence), slowing down traffic is another outcome.
As for square-in approach... I don't see that working well for more than 1 circulating lane. Remember - Trade's crusade is after the multilane ones, single lane are less of a problem generally.
And re-introducing possibility of T-bone, reducing throughput... what is the point of construction then?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 28, 2017, 11:15:39 AM
Remember - Trade's crusade is after the multilane ones, single lane are less of a problem generally.

This is true.  I’m mainly focused on the multilane roundabouts that have exceedingly high crash rates.  The single-lane roundabouts I have opposed are ones with fixed objects in the central island.  For instance, the roundabout at 96th and Westfield Blvd in Carmel has been the site of multiple fatalities over the past decade.   Two people were killed in 2007 when a vehicle slammed into the retaining wall in the middle.  The same thing happened again in 2016, killing one person.  These fatalities account for a significant percentage of total roadway fatalities in Carmel over the past decade.

Of the roundabouts analyzed in the IIHS study, there were 3 fatal crashes during the before period and none during the after period.  Based on this limited data they made the claim that roundabouts reduce fatalities by 90%.  Looking back at the 96th and Westfield Blvd intersection there are no news reports of fatal crashes occurring before the roundabout was constructed.  Since the fatalities at 96th and Westfield Blvd went from 0 in the before period to 3 in the after period, maybe we can claim that roundabouts increase fatalities by 90% (same amount of fatalities cited in the 2000 IIHS study when they made their claims).

The 96th and Westfield Blvd isn’t the only roundabout in Carmel that has had a fatal crash.  In August 2014, a driver was killed after losing control of their vehicle in the Pennsylvania St and 106th roundabout.  In Sept. 2014 a motorcyclist was killed after colliding with the curb on the north side of the 126th and Hazel Dell Parkway roundabout.  According to the Carmel Police Department there were 5 fatal crashes in the city from 2014-2016.  Of these 5 fatal crashes, 3 of them occurred at roundabouts.  Here are news reports of the fatal roundabout crashes:

Fishers man dies in motorcycle crash
http://fox59.com/2014/09/26/person-dead-after-motorcycle-accident-in-carmel/

Driver dead following accident in Carmel, passenger taken to hospital
http://fox59.com/2014/08/06/one-dead-in-carmel-accident-passenger-taken-to-hospital/

Carmel driver dies after crashing into roundabout’s concrete barrier
http://currentincarmel.com/carmel-driver-dies-after-crashing-into-roundabouts-concrete-barrier
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 01, 2017, 02:55:42 PM
Worst roundabout in Britain? Multiple crashes at 'lethal' roundabout cause concern
http://www.telegraph.co.uk/news/2017/07/31/worst-roundabout-britain-multiple-crashes-lethal-roundabout/

Incredibly there were 10 crashes in a 48 hour period at a newly opened roundabout in Britain.  These are British drivers who supposedly have a lot of experience driving through roundabouts.  So why so many crashes?  Is it just bad British drivers or bad design? 

Title: Re: Crash prone 'modern roundabouts'
Post by: english si on August 01, 2017, 06:03:42 PM
see thread on SABRE about that roundabout: https://www.sabre-roads.org.uk/forum/viewtopic.php?f=1&t=37936

it seems that while there are many things not up to muster (too flat, signs not big enough for the speed, junction not in keeping with the road, clearly designed by home-builders rather than highways people), it's not quite as bad as the drivers are making out and their numptiness is a contributing factor to the incidents.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 01, 2017, 06:29:12 PM
Odd that they would put in a roundabout where there was already grade separation. Seems like a bad idea (mostly because of driver expectation).

OSM shows where the roundabout is (Google has not yet updated their maps as of 1 Aug): https://goo.gl/NMePAs
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 02, 2017, 08:39:12 AM
it's not quite as bad as the drivers are making out and their numptiness is a contributing factor to the incidents.
Oh, now UK drivers are not fit for roundabouts... You're making progress, my friend, soon you would acknowledge that roundabouts are too good  to be built on planet Earth!
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 02, 2017, 09:05:59 AM
it's not quite as bad as the drivers are making out and their numptiness is a contributing factor to the incidents.

Oh, now UK drivers are not fit for roundabouts... You're making progress, my friend, soon you would acknowledge that roundabouts are too good  to be built on planet Earth!

I'd like to see how well American drivers could handle an unsigned roundabout suddenly appearing out of nowhere on a 70 MPH freeway.

A rogue roundabout is likely to produce more collisions off the bat than a signal due to the "conform or crash" nature of the design. Not denying that.
Title: Re: Crash prone 'modern roundabouts'
Post by: english si on August 02, 2017, 10:10:18 AM
Oh, now UK drivers are not fit for roundabouts...
No not saying that at all - the issue isn't the existence of the roundabout, it is that poor warning of this new feature, on a road where it doesn't really belong, raised the bar of attention needed on the road far above the already-high minimum expected on UK roads, catching the less attentive out. If the signs were the right size for 70mph, if the roundabout was well lit and had stuff in the middle (even just a raised mound of earth), then none of these crashes would have happened - but at the same time, if the drivers were as attentive they ought to have been, they wouldn't have crashed as they'd have seen the small signs on the approach and would be warned - even though the maroon car had taken out the chevron signs that mark the island.

I imagine the outcome of investigation into the RTIs will be zero bad driving charges (ie that they were driving with the legally expected amount of due care and attention), but also zero insurance payout from the constructors of the roundabout as they met the required standards even though they fell way short of best practice.

AFAICS, no one was hurt, and the only reason that cars were damaged (it seems that the maroon car has a puncture, but no dents, and the blue car is stuck in the mud, with some dents) was due to the sign poles (like everything else) merely conforming to minimum standards, but not best practice. It's a lesson in why shoddy practices are bad, ie what I've been saying, rather than one in "roundabouts are dangerous and require too high a standard of driving that drivers can't cope with" that you and tradephoric are pushing as a narrative in order to push shoddy practices. Tradephoric has attacked raised areas on islands as death traps, but the lack of one here is a key factor into why people didn't see the roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 02, 2017, 11:27:43 AM
Oh, now UK drivers are not fit for roundabouts.

English_si would never admit that.  British drivers are blameless and if there are a lot of crashes at a UK roundabout it must be bad design.    Of course if there are a lot of crashes at an American roundabout then it’s due to those stupid, lazy, and unobservant American drivers. 

I'd argue that the main problem with US roundabouts is culture and education, but in the UK it's geometry and design if a roundabout has lots of crashes.

In the US, when the issue seems to be design, it's actually due to education reasons - assuming that American drivers are stupid, lazy and unobservant, and therefore designing poor practice to be proscribed by road markings is a recipe for disaster.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 02, 2017, 12:39:00 PM
Oh, now UK drivers are not fit for roundabouts...
No not saying that at all - the issue isn't the existence of the roundabout, it is that poor warning of this new feature, on a road where it doesn't really belong, raised the bar of attention needed on the road far above the already-high minimum expected on UK roads, catching the less attentive out. If the signs were the right size for 70mph, if the roundabout was well lit and had stuff in the middle (even just a raised mound of earth), then none of these crashes would have happened - but at the same time, if the drivers were as attentive they ought to have been, they wouldn't have crashed as they'd have seen the small signs on the approach and would be warned - even though the maroon car had taken out the chevron signs that mark the island.

I imagine the outcome of investigation into the RTIs will be zero bad driving charges (ie that they were driving with the legally expected amount of due care and attention), but also zero insurance payout from the constructors of the roundabout as they met the required standards even though they fell way short of best practice.

AFAICS, no one was hurt, and the only reason that cars were damaged (it seems that the maroon car has a puncture, but no dents, and the blue car is stuck in the mud, with some dents) was due to the sign poles (like everything else) merely conforming to minimum standards, but not best practice. It's a lesson in why shoddy practices are bad, ie what I've been saying, rather than one in "roundabouts are dangerous and require too high a standard of driving that drivers can't cope with" that you and tradephoric are pushing as a narrative in order to push shoddy practices. Tradephoric has attacked raised areas on islands as death traps, but the lack of one here is a key factor into why people didn't see the roundabout.
Got it, got it...
Then, good sir, would you mind explaining what you mean by the following phrase:


it's not quite as bad as the drivers are making out and their numptiness is a contributing factor to the incidents.

And just to be cristal clear about the roots of my question:
Quote from: oxford dictionaries
numpty, noun British informal
    A stupid or ineffectual person.

So, good sir, do I get it correct that said drivers got into the accident on said roundabout are  stupid and/or ineffectual - in other words, not really qualified for driving?
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on August 10, 2017, 03:07:04 PM
For reference, this is what the intersection is now (http://www.openstreetmap.org/node/288022408#map=16/52.9012/-1.5572) while Google still has the old layout (https://www.google.com/maps/place/Mickleover,+Derby,+UK/@52.9024857,-1.5596431,1057m/data=!3m1!1e3!4m5!3m4!1s0x4879f655513db393:0xcec5721600e262ce!8m2!3d52.909805!4d-1.5369795).

Plop down any sort of at-grade intersection in the middle of what is effectively a freeway (fully grade-separated dual carriageway, what is now being called an "expressway" in England, which really is just a freeway with somewhat relaxed design standards and no legal restriction on non-motor vehicle users, even though they are highly discouraged) without adequate warning and you'll get lots of wrecks.

See also the SABRE thread, https://www.sabre-roads.org.uk/forum/viewtopic.php?f=1&t=37936:

Quote
Apparently the problems were as such:
- minimal signage that didn't make the approach obvious
- the street lighting wasn't switched on until several days after the roundabout opened
- the roundabout is kerb height, so again, isn't obvious on its approach
- no rumble strips

I leave it as an exercise for the reader to decide what would happen if you put a four-way signalized intersection in the middle of a road signed for and designed for 70 mph, where previously there was a free-flow ramp, with no advance warning signs or lighting.

(BTW if you zoom out you can see the road is part of a cut-off between two major freeway-class roads, the A50 - which was originally intended to be a full motorway, the M64 (http://pathetic.org.uk/unbuilt/m64/) - and A38. Basically the local authority did the equivalent of dumping a new at-grade in the middle of SC 277 between I-20 and I-77 so a few houses would have direct access to SC 277.)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 10, 2017, 03:10:55 PM
For reference, this is what the intersection is now (http://www.openstreetmap.org/node/288022408#map=16/52.9012/-1.5572) while Google still has the old layout (https://www.google.com/maps/place/Mickleover,+Derby,+UK/@52.9024857,-1.5596431,1057m/data=!3m1!1e3!4m5!3m4!1s0x4879f655513db393:0xcec5721600e262ce!8m2!3d52.909805!4d-1.5369795).

Plop down any sort of at-grade intersection in the middle of what is effectively a freeway (fully grade-separated dual carriageway, what is now being called an "expressway" in England, which really is just a freeway with somewhat relaxed design standards and no legal restriction on non-motor vehicle users, even though they are highly discouraged) without adequate warning and you'll get lots of wrecks.

See also the SABRE thread, https://www.sabre-roads.org.uk/forum/viewtopic.php?f=1&t=37936:

Quote
Apparently the problems were as such:
- minimal signage that didn't make the approach obvious
- the street lighting wasn't switched on until several days after the roundabout opened
- the roundabout is kerb height, so again, isn't obvious on its approach
- no rumble strips

I leave it as an exercise for the reader to decide what would happen if you put a four-way signalized intersection in the middle of a road signed for and designed for 70 mph, where previously there was a free-flow ramp, with no advance warning signs or lighting.
But... But... But this is roundabout, greatest and bestest thing ever!!!! There is no way  there would be any problem!!!
Title: Re: Crash prone 'modern roundabouts'
Post by: lordsutch on August 10, 2017, 03:14:38 PM
But... But... But this is roundabout, greatest and bestest thing ever!!!! There is no way  there would be any problem!!!

Strawman much?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 10, 2017, 03:26:29 PM
But... But... But this is roundabout, greatest and bestest thing ever!!!! There is no way  there would be any problem!!!

Strawman much?
No, just enjoying the show. Too bad innocent cars were damaged, not careers...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 10, 2017, 05:41:52 PM
But... But... But this is roundabout, greatest and bestest thing ever!!!! There is no way  there would be any problem!!!

Strawman much?

No, just enjoying the show. Too bad innocent cars were damaged, not careers...

No, that was a strawman. Don't try and weasel your way out now.
Title: Re: Crash prone 'modern roundabouts'
Post by: 6a on August 10, 2017, 11:56:06 PM
Presented without comment:
(https://uploads.tapatalk-cdn.com/20170811/3e971a2cb19b4151bde638645e34a935.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 15, 2017, 11:35:07 AM
Accidents at Dublin’s 161/Riverside roundabout jumped from 20 accidents before the roundabout to 156 after the roundabout.  Dublin engineers already have plans to eliminate a circulating lane through the roundabout to address the high number of accidents.  Not like anyone could have predicted this would happen though…  :crazy:

I have my doubts that the triple-lane roundabout currently under construction in Dublin, Ohio will see a reduction in total crashes (even though this is what the engineering manager of Dublin is predicting).

Dublin Built A Traffic Circle To Reduce Accidents. The Opposite Happened
In 2014, before the roundabout, there were 20 accidents at the intersection. In the past year, that jumped to 156 accidents..
http://radio.wosu.org/post/dublin-built-traffic-circle-reduce-accidents-opposite-happened#stream/0

Instead of learning from others mistakes, the City will forge ahead and construct it as a triple-lane roundabout.  A year later, the City will be perplexed why there are so many crashes at the roundabouts and hire a consultant to perform a safety audit.
   
Riverside-161 roundabout design being reviewed
Dublin officials said they are taking a closer look at the city’s largest roundabout to see whether any adjustments are needed to improve driver safety.  The city has a $29,046 contract with Wisconsin firm MTJ Engineering to study the state Route 161-Riverside Drive roundabout.
http://www.thisweeknews.com/news/20170214/riverside-161-roundabout-design-being-reviewed

The consultant, after being handed a big bag of money, will come to the conclusion that the roundabout should be reconfigured to a two-lane roundabout to reduce the total number of crashes.

(http://mediad.publicbroadcasting.net/p/wosu2/files/styles/medium/public/201708/roundabout_changes.png)

Engineers and police analyzed the roundabout design, and will change one busy entry point.  "The northbound lane configuration will become, the left lane will be left turn or straight through," O'Callaghan says. "The center lane will be straight only. And there will be a dedicated right-turn only lane."  Officials hope the changes will greatly reduce the number of crashes.  But it will cost $260,000.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 16, 2017, 11:00:37 PM
Jeannie Willis predicted there would be a reduction in crash frequency at the SR 161 / Riverside roundabout.  It turns out there has been 166 crashes at the roundabout in the first 9 months.  Compare that to just 20 crashes per year before the roundabout.  It's surprising that Jeannie didn't see this coming... all she had to do was look at the crash records of any triple-lane roundabout constructed in America to realize they are crash prone.  At least they are attempting to fix the mess they created.

Quote
Proposed changes for Dublin roundabout to take place in fall
http://www.10tv.com/article/proposed-changes-dublin-roundabout-take-place-fall

"The roundabout is actually operating fairly well on all of the approaches except the northbound approach," said Jeannie Willis, engineering manager for City of Dublin. "That seems to be where our drivers are getting the most confused."

"We did not expect to see anything like this. Safety is Dublin's number one priority," said Willis.

"We came to realize simplifying the decision making for the driver approaching the roundabout would help things out quite a bit," said Willis.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 22, 2017, 09:16:01 PM
It only took about two months for a driver to destroy Saegertown's new roundabout...  'Shakayla Shantel Deible ran her car into the masonry wall in the center of the roundabout on Main Street.  Authorities say she appeared to be under the influence of alcohol and drugs and will be charged based on the results of blood tests.'

June 12, 2017 - Saegertown's southern roundabout opens to traffic
http://www.yourerie.com/news/local-news/saegertowns-southern-roundabout-opens-to-traffic/739056574

Aug 22, 2017 - Woman destroys new roundabout in Saegertown
http://www.yourerie.com/news/local-news/woman-destroys-new-roundabout-in-saegertown/795648083
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 22, 2017, 09:22:40 PM
Another semitruck has tipped over at the 37th Street and Highway 275 roundabout in Nebraska, two months to the day that a semitrailer loaded with hogs tipped over in the roundabout back on June 22nd.  The roundabout opened in November 2016 and has already been the site of 2 tip-overs. 

Truck tips in roundabout
http://norfolkdailynews.com/news/truck-tips-in-roundabout/article_28e040c4-8777-11e7-a7e2-1f180cd69b14.html

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 22, 2017, 09:26:18 PM
It only took about two months for a driver to destroy Saegertown's new roundabout...  'Shakayla Shantel Deible ran her car into the masonry wall in the center of the roundabout on Main Street.  Authorities say she appeared to be under the influence of alcohol and drugs and will be charged based on the results of blood tests.'

June 12, 2017 - Saegertown's southern roundabout opens to traffic
http://www.yourerie.com/news/local-news/saegertowns-southern-roundabout-opens-to-traffic/739056574

Aug 22, 2017 - Woman destroys new roundabout in Saegertown
http://www.yourerie.com/news/local-news/woman-destroys-new-roundabout-in-saegertown/795648083
Destroy is a big word here. A roll or two of duck tape - and the thing would be as ugly as it was the day before accident...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 22, 2017, 09:43:39 PM
The animation for the 37th Street and US Hwy 275 in Norfolk, Nebraska is all wrong.  It doesn't show the semi-trucks flipping over on their sides.

Not a valid vimeo URL
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 22, 2017, 09:47:47 PM
The animation for the 37th Street and US Hwy 275 in Norfolk, Nebraska is all wrong.  It doesn't show the semi-trucks flipping over on their sides.

I went through a roundabout just a few days ago right behind a truck. It didn't flip over.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 22, 2017, 10:04:44 PM
A truck tipped over today on the Interchange 4 on-ramp to the NJ Turnpike. We need to ban highway on-ramps.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 22, 2017, 10:54:30 PM
A truck tipped over today on the Interchange 4 on-ramp to the NJ Turnpike. We need to ban highway on-ramps.

Trucks seemingly have a higher propensity to rolling over at roundabouts than at signalized intersections.  That's the point you are ignoring when you argue that trucks tip over on the NJ Turnpike.  The Herb Gray Parkway roundabout outside Windsor, Ontario saw 4 trucks rollover from April 2015 to August 2015.  Can you cite a traffic signal that has had 4 truck rollovers in a 5 month period?   You got roughly 300,000 traffic signals in America to choose from.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 23, 2017, 02:50:10 AM
Have there been any rollovers involving single-lane roundabouts? You've mentioned time and time again that single-lane roundabouts are not the problem. Yet, your issue with roundabouts has, lately, been more about the circle itself, and how you have to physically steer around it to avoid crashing (particularly the fact the FHWA indicates that the circle "forces" drivers to slow down). Single-lane roundabouts are just as prone to rollovers as large roundabouts, yet I don't think you've posted about single-lane roundabout rollovers just yet (although this thread is huge, so I may have missed a post).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 23, 2017, 06:35:15 AM
Have there been any rollovers involving single-lane roundabouts? You've mentioned time and time again that single-lane roundabouts are not the problem. Yet, your issue with roundabouts has, lately, been more about the circle itself, and how you have to physically steer around it to avoid crashing (particularly the fact the FHWA indicates that the circle "forces" drivers to slow down). Single-lane roundabouts are just as prone to rollovers as large roundabouts, yet I don't think you've posted about single-lane roundabout rollovers just yet (although this thread is huge, so I may have missed a post).
Good question actually. My best guess is that not all intersections are born equal. Intersections of heavier used roads, say arterial grade ones, get much higher share of truck traffic. Trucks are not frequent visitors on residential side streets where single lane roundabout would-be built.
Now if you put a compact single laner on a corner of Warehouse road and Factory drive, where 90% of 2000 daily vehicles are 53 feet long, then that would be a rollover heaven...
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on August 23, 2017, 06:48:04 PM
I know for a fact that there have been rollovers with single-lane roundabouts here in Oregon--particularly the Verboort Road/Martin Road roundabout north of Forest Grove.  I'm trying to find a link to one of the news stories.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on August 23, 2017, 08:11:53 PM
The simple truth is that drivers do stupid things on all types of roads.   We could just as easily have a thread on "Crash prone modern freeways", "Crash prone modern on ramps", Crash prone modern <fill in the blank".   Or we could just have a thread on "Crash prone impaired drivers".
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 23, 2017, 08:42:04 PM
The simple truth is that drivers do stupid things on all types of roads.   We could just as easily have a thread on "Crash prone modern freeways", "Crash prone modern on ramps", Crash prone modern <fill in the blank".   Or we could just have a thread on "Crash prone impaired drivers".

Humans are naturally prone to errors. All infrastructure is capable of producing collisions, but there does seem to be a remarkable uptick in collisions at roundabouts. This seems to be the case due to the, uhh, less-forgiving design of roundabouts. Not seeing a roundabout will almost certainly result in a collision, whereas not seeing a signal has the potential to have no effect (although if there is another car, the collision (a t-bone most likely) could be remarkably worse than simply driving off the road, in the case of a roundabout).

The potential for these catastrophic t-bone collisions seems to be the biggest reason that road agencies prefer roundabouts. However, new data (poorly compiled by Tradephoric -- no offence mate) seems to suggest that the trade-off may not be worth it (which is to say, the number of low-severity collisions skyrockets, whereas severe collisions barely drop off, if at all).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 24, 2017, 12:40:09 AM
This thread has banged on about the crash rates of 2x2 roundabouts, but admittedly it was piecemealed together.  Luckily new research was published in July 2017 that looks at the performance of 2x2 modern roundabouts (entitled Evaluation of Safety and Mobility of Two-Lane Roundabouts).  The research paper concludes what many of us have been saying all along - multilane roundabouts fail to provide a benefit in reducing less severe crashes...

Quote
Abstract: When looking at measures of fatal and severe-injury crashes, roundabouts have demonstrated improved safety performance compared to traditional signalized intersections. Despite this, when it comes to less severe crashes, multilane roundabouts fail to provide a similar benefit. Previous research into this topic has identified behaviors that are associated with crashes in two-lane roundabouts, with yielding violations and turn violations generally being the largest contributors to crashes. This study sought to build on that work by expanding the data collection effort to include more sites and relate the frequency of individual behaviors to specific design features. Ultimately, four roundabouts were chosen for data collection and analysis, with two of them being full 2x2 roundabouts and the other two half-2x2. These locations were University Dr. S and 5th Ave. S in St. Cloud (half-2x2), 185th St. W and Kenwood Trail in Lakeville (full-2x2), and TH-22 and Adams St. (half-2x2) and TH-22 and Madison Ave. in Mankato (full-2x2). In the last two, changes in traffic control were implemented to reduce failure-to-yield crashes, and the study compared the driver behavior before and after the interventions. In general, the collective results show that the problems observed in the earlier site are present in all of the other sites with scale variations prompted by geometric and traffic control design elements. For example, in the St. Cloud roundabout, an increased rate of right-from-inner-lane turn violations were observed, which can be attributed to the sharper deflection angles present. Additionally, from the aforementioned roundabout as well as the one in Lakeville, it was concluded that turn violation rates are affected on the single or multilane geometry of the links approaching the roundabout. Single-lane roads result in fewer left-from-outer-lane violations. Overhead lane designation signs result in reduced turn violations similar to the earlier studies’ interventions in the approach lane markings. Unfortunately, apart from confirming the trend, no successful design or intervention was discovered regarding yield violations.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&ved=0ahUKEwjAotWnge_VAhVoxoMKHY-sAOsQFghFMAY&url=http%3A%2F%2Fwww.cts.umn.edu%2FPublications%2FResearchReports%2Fpdfdownload.pl%3Fid%3D2818&usg=AFQjCNErF5f42w3IotPdklo9998d9SMgcA
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 24, 2017, 10:08:37 AM
A car was cut in half after a driver flew through the middle of a roundabout.  Miraculously everyone survived. 

https://au.news.yahoo.com/video/watch/36726027/out-of-control-car-smashes-through-roundabout/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 27, 2017, 08:37:33 PM
The Mineral Point & Pleasant View roundabout was the most crash prone intersection in Madison in 2016 with 47 crashes.  It has averaged 38.4 crashes per year since it was constructed in 2011.  It has been the most crash prone intersection in the city in 4 of the past 5 years.  Considering the roundabout is surrounded by cornfields, it’s somewhat surprising that this is the most crash prone in the city, but then again these 2x2 roundabouts are crash magnets. 

Roundabout on Madison's Far West Side has become a crash magnet
http://host.madison.com/wsj/news/local/roundabout-on-madison-s-far-west-side-has-become-a/article_97b3dd77-a269-5354-8c0a-3f7040cf4373.html

So what is the solution to all these crashes?  City engineer Mark Winter believes drivers are entering the roundabout too fast.  He wants to add more landscaping to the splitter island of the roundabout to restrict the view of drivers approaching the roundabout.  As Winter puts it “if you can see too far to the left when you enter a roundabout, you’ll never slow down” .  However, temporary fencing was recently added along the splitter islands of M-5 and Pontiac Trail, a crash prone roundabout in Michigan.  While the fencing did slightly lower the average speed of traffic entering the roundabout, there were just as many crashes in the before and after condition.  A presentation that discussed the M-5/Pontiac Trail fencing was presented at the 5th International Conference on Roundabouts in Green Bay earlier this year. 

There seems to be a level of frustration among roundabout experts regarding these high crash roundabouts.  The realization might be setting in that even a perfectly designed roundabout can fail at reducing crashes.  Here are some of the excerpts from the article…

Quote
“Too many drivers still don’t know what they are doing in a roundabout,”  Winter said.

“We’ve given up trying to control the behavior of drivers. It’s impossible,”  Winter said.

“It’s a tradeoff, like most counter-safety measures,”  Ball said. “I still think there will be fewer crashes. I think there’s a lot we’re still learning.”
 
Finally the article discusses the findings of a 2013 study done by Ball looking at the safety of roundabouts in Wisconsin.  Of the 30 roundabouts analyzed, 23 saw increases in total crashes (76%).  In addition, the injury crash rate were similar in the before and after condition.  Even while there was a significant increase in total crashes, there was not a significant reduction in injuries.
 
Quote
A study of 30 roundabouts in the state completed by Ball in 2013 that looked at crashes three years before and four years after they opened showed that 23 had more crashes after they opened.

Overall, there were 572 crashes four years after the 30 roundabouts opened versus 311 during the three years before the intersections were converted. Of those, 464 crashes resulting in property damage occurred after the roundabouts opened versus 194 before they opened. Both periods saw similar numbers of accidents with injuries.

But there were no fatalities at the time of the study’s release, which was the biggest reason why the roundabouts were built.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 27, 2017, 08:51:28 PM
The Mineral Point & Pleasant View roundabout was the most crash prone intersection in Madison in 2016 with 47 crashes.  It has averaged 38.4 crashes per year since it was constructed in 2011.  It has been the most crash prone intersection in the city in 4 of the past 5 years.  Considering the roundabout is surrounded by cornfields, it’s somewhat surprising that this is the most crash prone in the city, but then again these 2x2 roundabouts are crash magnets. 

Roundabout on Madison's Far West Side has become a crash magnet
http://host.madison.com/wsj/news/local/roundabout-on-madison-s-far-west-side-has-become-a/article_97b3dd77-a269-5354-8c0a-3f7040cf4373.html

So what is the solution to all these crashes?  City engineer Mark Winter believes drivers are entering the roundabout too fast.  He wants to add more landscaping to the splitter island of the roundabout to restrict the view of drivers approaching the roundabout.  As Winter puts it “if you can see too far to the left when you enter a roundabout, you’ll never slow down” .  However, temporary fencing was recently added along the splitter islands of M-5 and Pontiac Trail, a crash prone roundabout in Michigan.  While the fencing did slightly lower the average speed of traffic entering the roundabout, there were just as many crashes in the before and after condition.  A presentation that discussed the M-5/Pontiac Trail fencing was presented at the 5th International Conference on Roundabouts in Green Bay earlier this year. 

There seems to be a level of frustration among roundabout experts regarding these high crash roundabouts.  The realization might be setting in that even a perfectly designed roundabout can fail at reducing crashes.  Here are some of the excerpts from the article…

Quote
“Too many drivers still don’t know what they are doing in a roundabout,”  Winter said.

“We’ve given up trying to control the behavior of drivers. It’s impossible,”  Winter said.

“It’s a tradeoff, like most counter-safety measures,”  Ball said. “I still think there will be fewer crashes. I think there’s a lot we’re still learning.”
 
Finally the article discusses the findings of a 2013 study done by Ball looking at the safety of roundabouts in Wisconsin.  Of the 30 roundabouts analyzed, 23 saw increases in total crashes (76%).  In addition, the injury crash rate were similar in the before and after condition.  Even while there was a significant increase in total crashes, there was not a significant reduction in injuries.
 
Quote
A study of 30 roundabouts in the state completed by Ball in 2013 that looked at crashes three years before and four years after they opened showed that 23 had more crashes after they opened.

Overall, there were 572 crashes four years after the 30 roundabouts opened versus 311 during the three years before the intersections were converted. Of those, 464 crashes resulting in property damage occurred after the roundabouts opened versus 194 before they opened. Both periods saw similar numbers of accidents with injuries.

But there were no fatalities at the time of the study’s release, which was the biggest reason why the roundabouts were built.

My only question is if retirement savings of those experts would be used towards restitution...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 28, 2017, 02:20:38 AM
In other Wisconsin roundabout news, a truck tipped over on a multi-lane roundabout in Eau Claire on US 53 just south of I-94.  The SB lanes of US 53 were shut down for over 3 hours while they cleaned up the mess.

Truck rolls over, spills oil at Eau Claire roundabout
http://www.leadertelegram.com/News/Daily-Updates/2017/08/26/Truck-rolls-over-spills-oil-at-Eau-Claire-roundabout.html

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 29, 2017, 08:19:10 AM
A triple lane roundabout at Northland and Richmond in Appleton is set to open on Friday. 

Quote
Appleton's Richmond/Northland intersection to reopen Friday
(http://static-20.sinclairstoryline.com/resources/media/e5ea2b53-be3b-4ca3-96c9-6ef588ec9840-large16x9_47ooRab.jpg)
http://fox11online.com/news/local/appletons-richmond-northland-hwy-oo-roundabout-to-reopen-friday

A previous article indicated that the intersection averaged about 26 crashes/year between 2004 and 2012 (ie. a crash every two weeks).  Now that the roundabout is opening, you are more likely to see a crash every two days. 

Quote
Roundabout coming to Richmond and Northland
http://www.postcrescent.com/story/news/local/2014/07/24/roundabout-coming-richmond-northland/13119107/

Between 2004 and 2012, the intersection averaged about a crash every two weeks. About half of those wrecks resulted in an injury, authorities said.

In 2014 Northland and Richmond had 27 crashes, the most in the city.  Does anybody believe a complex triple-lane roundabout will help reduce the number of crashes?  Apparently WisDOT does.

Quote
Appleton ranks intersections with most crashes, looks at how to improve them
http://fox11online.com/news/local/fox-cities/appleton-ranks-intersections-with-most-crashes-looks-at-how-to-improve-them

Northland and Richmond was deemed the Appleton intersection with the most crashes in 2014. But the city, county, and state already have a plan in place to address that.

Tim Rank, WisDOT Project Manager, said, "We've got our multi-lane roundabout project planned, construction is planned to start in 2017."

These plans have been in the works since 2009, and now they're close to coming to fruition.

To be exact, 27 crashes happened at that intersection in 2014 alone. The DOT says the new multi-lane roundabout would hopefully reduce that number in the future.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 30, 2017, 08:09:14 AM
Beaufort County City Council members are not big fans of the Bluffton Parkway roundabout.  Significant pavement marking changes were made in 2012 meant to reduce crashes.  There was a short-term reduction in crashes after the pavement changes but it didn’t last.  There are now talks to eliminate the outside lane of the multi-lane roundabout and force the right-hand lane to go right at all entry points or to eliminate the roundabout altogether and replace it with a traffic signal.

Quote
Hate the Bluffton Parkway traffic circle? Join the club. But how could it change?
http://www.islandpacket.com/news/local/traffic/article170040982.html

“The number of phone calls (from local drivers), the number of visits, the number of emails – this subject has been unending,”  Beaufort County Councilman Mike Covert said.

Councilman Jerry Stewart said, “From what I hear, a lot of people won’t drive there because they don’t want to negotiate”  the circle.

Councilman Tabor Vaux said he supports an idea to eliminate the outside lane of the roundabout and force the right-hand lane to go right at all entry points, similar to the Sea Pines Circle on Hilton Head Island.  “I think that’s what needs to happen there,”  he said. “What do we need to make that happen?”  Vaux asked county engineering staff. “I came very, very close to getting in a wreck there (earlier this week) – I know of six or seven people who have gotten in wrecks there recently.”

Stewart agreed, saying, “You really have to very careful or you’re going to be hit. Something has to be done,”  he said. “... It was poorly designed – period.”
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 05, 2017, 08:41:08 AM
Have there been any rollovers involving single-lane roundabouts? You've mentioned time and time again that single-lane roundabouts are not the problem. Yet, your issue with roundabouts has, lately, been more about the circle itself, and how you have to physically steer around it to avoid crashing (particularly the fact the FHWA indicates that the circle "forces" drivers to slow down). Single-lane roundabouts are just as prone to rollovers as large roundabouts, yet I don't think you've posted about single-lane roundabout rollovers just yet (although this thread is huge, so I may have missed a post).

Single-lane roundabouts haven’t been a problem in respect to high crash rates, but they are prone to truck tip overs.  Over the weekend a fuel tanker flipped on its side at a single-lane roundabout at St. John’s International Airport.  The roundabout was shut down for 8 hours as hazmat crews cleaned up the accident and offloaded the fuel from the tanker onto another truck.  Worst yet, the airlines experienced a fuel shortage at the airport and a Boeing 747 took off with a low fuel load.  Due to a diversion mid-flight, the plane ran out of fuel and crashed into a cornfield in Kansas killing all 269 people on board.   The last part of the story may not have happened, but even if it had the roundabout would be touted for its safety record.

Having a truck tip over and shutting down a roundabout for a good part of the day is not desirable (not to mention the danger to truck drivers when their 20 ton load flips over).  Hopefully not too many people in St. John's missed their flight over the weekend.

Fuel tanker overturns in St. John's airport roundabout -
Tanker driver taken to hospital with non-life threatening injuries

http://www.cbc.ca/news/canada/newfoundland-labrador/fuel-tanker-overturns-in-roundabout-at-st-john-s-airport-roundabout-1.4273758
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on September 05, 2017, 08:46:56 AM
Have there been any rollovers involving single-lane roundabouts? You've mentioned time and time again that single-lane roundabouts are not the problem. Yet, your issue with roundabouts has, lately, been more about the circle itself, and how you have to physically steer around it to avoid crashing (particularly the fact the FHWA indicates that the circle "forces" drivers to slow down). Single-lane roundabouts are just as prone to rollovers as large roundabouts, yet I don't think you've posted about single-lane roundabout rollovers just yet (although this thread is huge, so I may have missed a post).

Single-lane roundabouts haven’t been a problem in respect to high crash rates, but they are prone to truck tip overs.  Over the weekend a fuel tanker flipped on its side at a single-lane roundabout at St. John’s International Airport.  The roundabout was shut down for 8 hours as hazmat crews cleaned up the accident and offloaded the fuel from the tanker onto another truck.  Worst yet, the airlines experienced a fuel shortage at the airport and a Boeing 747 took off with a low fuel load.  Due to a diversion mid-flight, the plane ran out of fuel and crashed into a cornfield in Kansas killing all 269 people on board.   The last part of the story may not have happened, but even if it had the roundabout would be touted for its safety record.

Having a truck tip over and shutting down a roundabout for a good part of the day is not desirable (not to mention the danger to truck drivers when their 20 ton load flips over).  Hopefully not too many people in St. John's missed their flight over the weekend.

Fuel tanker overturns in St. John's airport roundabout -
Tanker driver taken to hospital with non-life threatening injuries

http://www.cbc.ca/news/canada/newfoundland-labrador/fuel-tanker-overturns-in-roundabout-at-st-john-s-airport-roundabout-1.4273758


Being that traffic had to detour a whole 1/4 mile to the next intersection, I think people managed to deal with the situation just fine.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 05, 2017, 09:11:38 AM
A truck tipped over today on the Interchange 4 on-ramp to the NJ Turnpike. We need to ban highway on-ramps.

Trucks seemingly have a higher propensity to rolling over at roundabouts than at signalized intersections.  That's the point you are ignoring when you argue that trucks tip over on the NJ Turnpike.  The Herb Gray Parkway roundabout outside Windsor, Ontario saw 4 trucks rollover from April 2015 to August 2015.  Can you cite a traffic signal that has had 4 truck rollovers in a 5 month period?   You got roughly 300,000 traffic signals in America to choose from.

Jeffandnicole you never got back to me.  Did you ever find a signalized intersection that has had 4 truck rollovers in a 5 month period?  That’s what happened at the Herb Gray Parkway roundabout. Depending what direction on the 401 you are traveling, traffic is diverted over 6 miles if that roundabout is closed (which it is frequently due to the absurd number of trucks flipping over on it).  Maybe a ¼ mile is no big deal, but what about 6 miles?  Wouldn’t you find that annoying?  You seem to give roundabouts the benefit of the doubt, so I take it you wouldn’t mind driving 6 miles out of your way.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on September 05, 2017, 09:16:59 AM
A truck tipped over today on the Interchange 4 on-ramp to the NJ Turnpike. We need to ban highway on-ramps.

Trucks seemingly have a higher propensity to rolling over at roundabouts than at signalized intersections.  That's the point you are ignoring when you argue that trucks tip over on the NJ Turnpike.  The Herb Gray Parkway roundabout outside Windsor, Ontario saw 4 trucks rollover from April 2015 to August 2015.  Can you cite a traffic signal that has had 4 truck rollovers in a 5 month period?   You got roughly 300,000 traffic signals in America to choose from.

Jeffandnicole you never got back to me.  Did you ever find a signalized intersection that has had 4 truck rollovers in a 5 month period?  That’s what happened at the Herb Gray Parkway roundabout. Depending what direction on the 401 you are traveling, traffic is diverted over 6 miles if that roundabout is closed (which it is frequently due to the absurd number of trucks flipping over on it).  Maybe a ¼ mile is no big deal, but what about 6 miles?  Wouldn’t you find that annoying?  You seem to give roundabouts the benefit of the doubt, so I take it you wouldn’t mind driving 6 miles out of your way.


I don't spend every waking moment Googling accidents at specific intersections for the sole purpose of posting on this forum, so no, I didn't find any.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 05, 2017, 10:14:58 AM
There are so many problematic roundabouts that have a history of tip-overs it takes hardly any time at all compiling the data.  Instead of spending 5 minutes highlighting traffic signals that are prone to truck tip-overs, you spend your time researching NJ Turnpike accidents and then post them on a forum about roundabouts.  Stay classy NJ.  So how is that petition to ban highway on-ramps going?

A truck tipped over today on the Interchange 4 on-ramp to the NJ Turnpike. We need to ban highway on-ramps.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 05, 2017, 10:48:14 AM
There are so many problematic roundabouts that have a history of tip-overs it takes hardly any time at all compiling the data.  Instead of spending 5 minutes highlighting traffic signals that are prone to truck tip-overs, you spend your time researching NJ Turnpike accidents and then post them on a forum about roundabouts.  Stay classy NJ.  So how is that petition to ban highway on-ramps going?

A truck tipped over today on the Interchange 4 on-ramp to the NJ Turnpike. We need to ban highway on-ramps.

As far as I remember, there are 2 people loosing life on roads every hour. We need to ban roads!
 
On a more serious note, problems are associated with any single human action; and it is about cost-benefit analysis to determine if solution worth the trouble, or it creates more problems than is solves.
It is pretty obvious that roundabouts are designed so that they become prone to tipping over. You only need to know high school physics to tell that. Now if that is an acceptable problem because it is fairly uncommon, or it is a systematic problem which needs to be addressed is another issue.
Tipping over on a ramp seems way less common, and given mere amount of ramps compared to roundabout - i wonder if there would be a single truck left on the road if probabilities were the same...
Title: Re: Crash prone 'modern roundabouts'
Post by: johndoe on September 05, 2017, 08:25:32 PM
TRB has an upcoming webinar that may interest some of you: http://www.trb.org/Calendar/Blurbs/176470.aspx
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 05, 2017, 08:58:44 PM
TRB has an upcoming webinar that may interest some of you: http://www.trb.org/Calendar/Blurbs/176470.aspx
Just $105? Sorry, I don't have any spare change with me..
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 06, 2017, 10:36:50 AM
TRB has an upcoming webinar that may interest some of you: http://www.trb.org/Calendar/Blurbs/176470.aspx

John Hourdos is going to be moderating this webinar.  In a previous webinar he had discussed crash prone multi-lane roundabouts in Richfield, MN and his research was going to be expanded to additional multi-lane roundabouts in Minnesota (University Dr & 5th Ave in St. Cloud; Hwy 22 at Adams St and Madison Ave in Mankato; 50/60 Roundabout in Lakeville).  A research paper was published in July 2017 that discusses the results of this additional research and I’m sure the upcoming webinar will touch on a lot of it.  The paper concluded that no successful design or intervention was discovered that lowered yield violations (which is a big percentage of the crashes that occur at these complex roundabouts).

Evaluation of Safety and Mobility of Two-Lane Roundabouts
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&ved=0ahUKEwjAotWnge_VAhVoxoMKHY-sAOsQFghFMAY&url=http%3A%2F%2Fwww.cts.umn.edu%2FPublications%2FResearchReports%2Fpdfdownload.pl%3Fid%3D2818&usg=AFQjCNErF5f42w3IotPdklo9998d9SMgcA

It looks like Mark McCulloch from Washtenaw Road Commission will also be presenting in the webinar.  He is the man behind the notorious State and Ellsworth roundabout.  Before the roundabout was built, Mark was cocky and thought the roundabout was going to work great (he admitted so much at the roundabout conference this year).  But after countless crashes, reality has set in for him.  And until he can cite concrete evidence that the roundabout has reduced injury crashes at the intersection, he's delusional for thinking that the roundabout is safer. 

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 06, 2017, 11:08:54 AM
Probability and statistics question:

The City of Madison has about 200 traffic signals and 7 roundabouts.  Assuming that traffic signals and roundabouts have the same crash rate, what is the probability that the top 3 most crash prone intersections in the city are all roundabouts? 

City of Madison, WI 2016 Crash Report
https://www.cityofmadison.com/trafficEngineering/documents/2016CrashReport.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 06, 2017, 11:11:47 AM
It looks like Mark McCulloch from Washtenaw Road Commission will also be presenting in the webinar.  He is the man behind the notorious State and Ellsworth roundabout.  Before the roundabout was built, Mark was cocky and thought the roundabout was going to work great (he admitted so much at the roundabout conference this year).  But after countless crashes, reality has set in for him.  And until he can cite concrete evidence that the roundabout has reduced injury crashes at the intersection, he's delusional for thinking that the roundabout is safer.

He wasn't cocky. There wasn't much of any "concrete evidence" that multi-lane roundabouts weren't an effective solution to curbing collisions and reducing severity back when they built the roundabout. A lot of the data that you cite comes from the last three to four years.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 06, 2017, 11:12:38 AM
Probability and statistics question:

The City of Madison has about 200 traffic signals and 7 roundabouts.  Assuming that traffic signals and roundabouts have the same crash rate, what is the probability that the top 3 most crash prone intersections in the city are all roundabouts?

It's a 207-way tie.

EDIT: Or, is that not what you are getting at?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 06, 2017, 11:17:06 AM
Probability and statistics question:

The City of Madison has about 200 traffic signals and 7 roundabouts.  Assuming that traffic signals and roundabouts have the same crash rate, what is the probability that the top 3 most crash prone intersections in the city are all roundabouts? 

City of Madison, WI 2016 Crash Report
https://www.cityofmadison.com/trafficEngineering/documents/2016CrashReport.pdf
Incomplete problem definition.
If roundabouts were built to replace most problematic  - highest volume, or otherwise difficult - light control intersections, pure arithmetic probability is not 100% relevant.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 06, 2017, 01:23:04 PM
There are 200 red marbles and 7 blue marbles mixed up in a bag.  What is the probability that the first 3 marbles pulled out of the bag are blue. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 06, 2017, 01:25:30 PM
Driver fatally injured after striking a 4-ton boulder in the middle of a Prescott roundabout.  Another fixed object fatality in the middle of a roundabout.

37-Year-Old Man from Page Dies in Crash at Roundabout
http://www.prescottenews.com/index.php/news/current-news/item/30613-37-year-old-man-from-page-dies-in-crash-at-roundabout

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 06, 2017, 02:04:18 PM
There are 200 red marbles and 7 blue marbles mixed up in a bag.  What is the probability that the first 3 marbles pulled out of the bag are blue.
What is the probability I would see a mastodon on my way home?
I would say 50% - either  "yes" or "no"!
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on September 06, 2017, 02:17:51 PM
There are 200 red marbles and 7 blue marbles mixed up in a bag.  What is the probability that the first 3 marbles pulled out of the bag are blue. 

1 in 41,627.

Do you want me to show my work?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 06, 2017, 02:59:04 PM
There are 200 red marbles and 7 blue marbles mixed up in a bag.  What is the probability that the first 3 marbles pulled out of the bag are blue. 

1 in 41,627.

Do you want me to show my work?

7/207 x 6/206 x 5/205

Still not sure what he wants us to get out of this.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 06, 2017, 03:28:04 PM
There are 200 red marbles and 7 blue marbles mixed up in a bag.  What is the probability that the first 3 marbles pulled out of the bag are blue. 

1 in 41,627.

Do you want me to show my work?

Nope that is the answer I got!  Now replace red marbles with traffic signals and blue marbles with roundabouts and it highlights the unlikelihood that Madison’s top 3 crash locations would all be at roundabouts.  To put 1 in 41,627 into perspective… the odds of getting struck by lightning in your lifetime is 1 in 3,000.

And the crashes aren't even close.  The Mineral Point & Pleasant View roundabout experienced 47 crashes compared to just 16 crashes at the Darwin Rd & Packers Ave traffic signal (the most crash prone traffic signal in the city).  And as mentioned the Mineral Point & Pleasant View roundabout is surrounded by cornfields… not a location you would expect to see the most number of crashes in the city.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 06, 2017, 03:49:46 PM
There are 200 red marbles and 7 blue marbles mixed up in a bag.  What is the probability that the first 3 marbles pulled out of the bag are blue. 

1 in 41,627.

Do you want me to show my work?

Nope that is the answer I got!  Now replace red marbles with traffic signals and blue marbles with roundabouts and it highlights the unlikelihood that Madison’s top 3 crash locations would all be at roundabouts.  To put 1 in 41,627 into perspective… the odds of getting struck by lightning in your lifetime is 1 in 3,000.

And the crashes aren't even close.  The Mineral Point & Pleasant View roundabout experienced 47 crashes compared to just 16 crashes at the Darwin Rd & Packers Ave traffic signal (the most crash prone traffic signal in the city).  And as mentioned the Mineral Point & Pleasant View roundabout is surrounded by cornfields… not a location you would expect to see the most number of crashes in the city.

Common mistake for freshmen probability course.
What you're saying would be correct if roundabouts were randomly distributed around the city ("marbles" are all equal).
WIth all my disrespect to those designing roundabouts, I still doubt they choose locations by flipping a coin. Most likely intersections with pre-existing problem are addressed. So roundabout locations were not just simple regular marbles to begin with
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 06, 2017, 03:54:28 PM
[T]he Mineral Point & Pleasant View roundabout is surrounded by cornfields… not a location you would expect to see the most number of crashes in the city.

Not necessarily. We've discussed, in the past, about visibility at (and approaching) roundabouts. If visibility is too good, drivers might* be more likely to determine whether or not they can "make it" through without crashing from a longer way's away. It's possible that some of these crashes are due to poor judgement in that respect.

It's also possible that the rural location has high-speed approaches, contributing to run-off, "I didn't see it coming" collisions. The kind where the car goes over the roundabout, or fails to yield due to high speed + not enough braking time to properly yield.

*emphasis on "might" because past studies on visibility have been inconclusive (IIRC).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 18, 2017, 05:35:36 PM
The City of Hilliard Division of Engineering is studying three crash prone roundabouts in Hilliard.  They put together an informative website detailing the problems and possible counter-measures they are considering at the roundabouts.  According to the city, there have been 231 crashes at the Cemetery Rd & Main St roundabout from 2014-2016 (10% resulting in injury).

http://www.hilliardohio.gov/roundabouts/study



   

Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on October 19, 2017, 06:30:29 AM
The last time I went through a roundabout, it ran out of memory and froze up until the DOT came by and rebooted it.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 19, 2017, 10:31:01 AM
The last time I went through a roundabout, it ran out of memory and froze up until the DOT came by and rebooted it.

Hmm. That's two silly posts in a row from you. I think some one needs to be rebooted.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 19, 2017, 01:29:25 PM
There are 200 red marbles and 7 blue marbles mixed up in a bag.  What is the probability that the first 3 marbles pulled out of the bag are blue. 

1 in 41,627.

Do you want me to show my work?

Nope that is the answer I got!  Now replace red marbles with traffic signals and blue marbles with roundabouts and it highlights the unlikelihood that Madison’s top 3 crash locations would all be at roundabouts.  To put 1 in 41,627 into perspective… the odds of getting struck by lightning in your lifetime is 1 in 3,000.

And the crashes aren't even close.  The Mineral Point & Pleasant View roundabout experienced 47 crashes compared to just 16 crashes at the Darwin Rd & Packers Ave traffic signal (the most crash prone traffic signal in the city).  And as mentioned the Mineral Point & Pleasant View roundabout is surrounded by cornfields… not a location you would expect to see the most number of crashes in the city.

Common mistake for freshmen probability course.
What you're saying would be correct if roundabouts were randomly distributed around the city ("marbles" are all equal).
WIth all my disrespect to those designing roundabouts, I still doubt they choose locations by flipping a coin. Most likely intersections with pre-existing problem are addressed. So roundabout locations were not just simple regular marbles to begin with

This.  The math exercise was pointless.

If roundabouts are being installed to mitigate injury crashes or crashes in general, then it's more like....
Put 200 blue marbles and 7 red marbles in a tube, except the red marbles are three times as big.  Whittle the red marbles down so they're only twice the size, put them back in, and shake the tube for a few minutes.  What are the chances that the red marbles still end up on top?

And yes, I know it's not a perfect analogy.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on October 19, 2017, 02:05:44 PM
how do you unsubscribe from a topic?  i don't give a flying fuck about this anymore, roundabouts are great.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 19, 2017, 02:16:40 PM
how do you unsubscribe from a topic?  i don't give a flying fuck about this anymore, roundabouts are great.
We will let you unsubscribe only once you are fully convinced that roundabouts are public enemy. No other way around!
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on October 19, 2017, 02:21:43 PM
how do you unsubscribe from a topic?  i don't give a flying fuck about this anymore, roundabouts are great.
We will let you unsubscribe only once you are fully convinced that roundabouts are public enemy. No other way around!

gonna be hard living in the roundabout capital of america  :-D
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 19, 2017, 02:22:19 PM
how do you unsubscribe from a topic?  i don't give a flying fuck about this anymore, roundabouts are great.

Seriously though, I don't think there's a way. I've tried deleting all my posts from a topic, in such a way that it didn't appear as though I was connected to the topic anymore. But I continued to receive notifications on the 'new replies' page anyway.

Guess you're in for the long haul!
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 19, 2017, 02:47:37 PM
how do you unsubscribe from a topic?  i don't give a flying fuck about this anymore, roundabouts are great.

Seriously though, I don't think there's a way. I've tried deleting all my posts from a topic, in such a way that it didn't appear as though I was connected to the topic anymore. But I continued to receive notifications on the 'new replies' page anyway.

Guess you're in for the long haul!

I remember when this came up last time, jakeroot.  Your question is here (https://www.aaroads.com/forum/index.php?topic=18751.msg2187961#msg2187961), and the pertinent reply links to here (https://www.aaroads.com/forum/index.php?topic=18320.0).  You tried as suggested, but then replied (https://www.aaroads.com/forum/index.php?topic=18751.msg2188043#msg2188043) that it doesn't work if you've replied in the thread.

I've never done the whole notify or subscribe thing, so I'm a little clueless as to how this all works.  Does anyone know if there's a fix to this problem?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 19, 2017, 03:04:56 PM
I remember when this came up last time, jakeroot.  Your question is here (https://www.aaroads.com/forum/index.php?topic=18751.msg2187961#msg2187961), and the pertinent reply links to here (https://www.aaroads.com/forum/index.php?topic=18320.0).  You tried as suggested, but then replied (https://www.aaroads.com/forum/index.php?topic=18751.msg2188043#msg2188043) that it doesn't work if you've replied in the thread.

I've never done the whole notify or subscribe thing, so I'm a little clueless as to how this all works.  Does anyone know if there's a fix to this problem?

Funny. In that third link, my reply indicates that deleting your posts works, but it doesn't. Don't know why I said that.

I'm not sure anyone uses that "notify" feature. I know I don't, nor have I ever. If I was interested in a thread, I'd probably drop a line in it anyways, expunging the need for that feature anyways.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 19, 2017, 03:12:28 PM
Personally, I can barely stand my new phone notifying me whenever an email comes in, and I only get one or two emails a day.  I can't imagine wanting notifications every time a thread gets bumped.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 19, 2017, 05:32:32 PM
This.  The math exercise was pointless.

If roundabouts are being installed to mitigate injury crashes or crashes in general, then it's more like....
Put 200 blue marbles and 7 red marbles in a tube, except the red marbles are three times as big.  Whittle the red marbles down so they're only twice the size, put them back in, and shake the tube for a few minutes.  What are the chances that the red marbles still end up on top?

And yes, I know it's not a perfect analogy.

That was really the point of the marble analogy.  At certain types of roundabouts you have beach-ball sized crash rates compared to golf-ball sized crash rates at traffic signals.  I’m not arguing that roundabouts and traffic signals have similar crash rates.  That is why it’s not surprising that the top 3 crash rate intersections in Madison are at roundabouts (all 2x2s).  That’s why it’s not surprising that the most crash prone intersection in Michigan last year was at the 14 Mile and Orchard Lake roundabout (3x2).  The year before that the most crash prone intersection was at the M-5 and Pontiac Trail roundabout (3x2).  That roundabout was constructed over 6 years ago and drivers should have had plenty of time to get use to it by now.  It wouldn’t shock me if the most crash prone intersection in the entire country was at a roundabout.  The fact that there are so many more traffic signals than roundabouts in the country doesn’t matter.  When certain types of roundabouts (2x2s, 3x2s) have such high crash rates, they rise to the top of these crash lists (whether it be Madison, Michigan, or the entire USA). 

i don't give a flying fuck about this anymore, roundabouts are great.

Roundabouts are great at crashing cars into each other.
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on October 19, 2017, 08:15:39 PM
i don't give a flying fuck about this anymore, roundabouts are great.

Roundabouts are great at crashing cars into each other.

Personally, I'm willing to accept the risk for the improved traffic flow. The roundabout at Fountain St and Fairway Rd / Kossuth Rd in Cambridge, ON works great! I drive it twice a day, and despite both of these roads being pretty busy for two-lane roads, I rarely stop for more than 5 seconds. Meanwhile, heading east on Speedvale Ave through the traffic light at CR 32 near Guelph takes almost 5 minutes due to poor signal timing :pan:.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on October 20, 2017, 11:14:12 AM
I have been wondering if tradephoric has been keeping track of roundabouts that he has highlighted over time.

Pretty sure incidents drop off on a lot of them just like engineers say they do.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 20, 2017, 12:03:06 PM
I have been wondering if tradephoric has been keeping track of roundabouts that he has highlighted over time.

Pretty sure incidents drop off on a lot of them just like engineers say they do.
I'm afraid it is more difficult than it sounds. Full statistics is not easy to come across, and not all accidents get into the news.
Ones in Malta seems to come up once in a while in mostly negative light. Those are what, 10+ years old? No real improvement... 
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on October 20, 2017, 06:35:42 PM
Meanwhile roundabouts number 111 and 112 are opening in Carmel, with no mass carnage. (http://carmellink.com/pdfs/news/4th%20and%20Range%20Line%20RAB%20and%20update.pdf) 
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on October 20, 2017, 10:55:44 PM
I have been wondering if tradephoric has been keeping track of roundabouts that he has highlighted over time.

Pretty sure incidents drop off on a lot of them just like engineers say they do.
I'm afraid it is more difficult than it sounds. Full statistics is not easy to come across, and not all accidents get into the news.
Ones in Malta seems to come up once in a while in mostly negative light. Those are what, 10+ years old? No real improvement...
Negative light, yes, but I haven't heard complaints about accidents -- just annoyance at having to navigate 5 of them within a half-mile.

Incidents have surely dropped off on the NY 85 roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 20, 2017, 11:03:38 PM
I have been wondering if tradephoric has been keeping track of roundabouts that he has highlighted over time.

Pretty sure incidents drop off on a lot of them just like engineers say they do.
I'm afraid it is more difficult than it sounds. Full statistics is not easy to come across, and not all accidents get into the news.
Ones in Malta seems to come up once in a while in mostly negative light. Those are what, 10+ years old? No real improvement...
Negative light, yes, but I haven't heard complaints about accidents -- just annoyance at having to navigate 5 of them within a half-mile.

Incidents have surely dropped off on the NY 85 roundabouts.
http://m.timesunion.com/news/article/The-Capital-Region-s-most-dangerous-intersections-11281734.php
Whatever it worth. 
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on October 20, 2017, 11:12:11 PM
I have been wondering if tradephoric has been keeping track of roundabouts that he has highlighted over time.

Pretty sure incidents drop off on a lot of them just like engineers say they do.
I'm afraid it is more difficult than it sounds. Full statistics is not easy to come across, and not all accidents get into the news.
Ones in Malta seems to come up once in a while in mostly negative light. Those are what, 10+ years old? No real improvement...
Negative light, yes, but I haven't heard complaints about accidents -- just annoyance at having to navigate 5 of them within a half-mile.

Incidents have surely dropped off on the NY 85 roundabouts.
http://m.timesunion.com/news/article/The-Capital-Region-s-most-dangerous-intersections-11281734.php
Whatever it worth.
Not much.  A report done by our local ambulance chasers that shows the Slingerlands Roundabouts on NY 85 not on the list, although the US 9/NY 67 one may be on it.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 21, 2017, 01:13:00 AM
Hazmat accident involving a tractor-trailer in one of the roundabouts on Wednesday, July 26, 2017 in Malta, New York.  According to Police Route 67 Exit 12 was closed for 12 hours as 2000 gallons of liquefied asphalt additive was mopped up off the roadway.  Both the driver and 6 year old passenger were taken to Saratoga Hospital and later released. 

http://www.timesunion.com/news/article/Northway-exit-reopens-hours-after-crash-in-Malta-11466679.php
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 21, 2017, 02:31:57 AM
I assume you will continue to report on all collisions that occur at roundabouts, because it can be assumed that the circular nature of the junction is the main cause?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 21, 2017, 06:36:45 AM
I have been wondering if tradephoric has been keeping track of roundabouts that he has highlighted over time.

Pretty sure incidents drop off on a lot of them just like engineers say they do.
I'm afraid it is more difficult than it sounds. Full statistics is not easy to come across, and not all accidents get into the news.
Ones in Malta seems to come up once in a while in mostly negative light. Those are what, 10+ years old? No real improvement...
Negative light, yes, but I haven't heard complaints about accidents -- just annoyance at having to navigate 5 of them within a half-mile.

Incidents have surely dropped off on the NY 85 roundabouts.
http://m.timesunion.com/news/article/The-Capital-Region-s-most-dangerous-intersections-11281734.php
Whatever it worth.
Not much.  A report done by our local ambulance chasers that shows the Slingerlands Roundabouts on NY 85 not on the list, although the US 9/NY 67 one may be on it.

Don't want to be political, but things are really similar to recent political standards... Goals  shift from aiming high  towards getting a badge of honor for not being the worst one.
OK, those roundabouts are no longer in bottom 1%, great! Next one would be in top 95%!
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 21, 2017, 09:36:00 AM
I assume you will continue to report on all collisions that occur at roundabouts, because it can be assumed that the circular nature of the junction is the main cause?

There were a string of posts about the Malta roundabout (not brought up by me i'll add) and someone had mentioned that they haven't heard complaints about accidents at them.  Three months ago a truck tips over, spills over 2000 gallons of liquefied asphalt additive, creates a hazmat situation that shuts the roundabout for 12 hours, and a 6-year old boy is transported to the hospital after he cuts his head open... and nobody is complaining about accidents?  This became an event for the town of Malta that day.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on October 21, 2017, 09:40:57 AM
I assume you will continue to report on all collisions that occur at roundabouts, because it can be assumed that the circular nature of the junction is the main cause?

There were a string of posts about the Malta roundabout (not brought up by me i'll add) and someone had mentioned that they haven't heard complaints about accidents at them.  Three months ago a truck tips over, spills over 2000 gallons of liquefied asphalt additive, creates a hazmat situation that shuts the roundabout for 12 hours, and a 6-year old boy is transported to the hospital after he cuts his head open... and nobody is complaining about accidents?  This became an event for the town of Malta that day.
So...one recent accident...and we are certain the roundabout is to blame.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 21, 2017, 09:47:57 AM
I assume you will continue to report on all collisions that occur at roundabouts, because it can be assumed that the circular nature of the junction is the main cause?

There were a string of posts about the Malta roundabout (not brought up by me i'll add) and someone had mentioned that they haven't heard complaints about accidents at them.  Three months ago a truck tips over, spills over 2000 gallons of liquefied asphalt additive, creates a hazmat situation that shuts the roundabout for 12 hours, and a 6-year old boy is transported to the hospital after he cuts his head open... and nobody is complaining about accidents?  This became an event for the town of Malta that day.
So...one recent accident.
One of top 5 accidents in a region for the year? Not a bad bet.
Granted, this is a freak one-time event (6 year old riding in a hazmat truck? WTF?) - but I didn't see statistics; and throughput - which is the advertised super-benefit - of those circles is not perfect. At least, town of Malta didn't allow GF to adjust shift times because some roundabouts are already overloaded. Some paths through secondary circles are plainly blocked during rush hour...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 21, 2017, 10:02:27 AM
I assume you will continue to report on all collisions that occur at roundabouts, because it can be assumed that the circular nature of the junction is the main cause?

There were a string of posts about the Malta roundabout (not brought up by me i'll add) and someone had mentioned that they haven't heard complaints about accidents at them.  Three months ago a truck tips over, spills over 2000 gallons of liquefied asphalt additive, creates a hazmat situation that shuts the roundabout for 12 hours, and a 6-year old boy is transported to the hospital after he cuts his head open... and nobody is complaining about accidents?  This became an event for the town of Malta that day.
So...one recent accident...and we are certain the roundabout is to blame.


Here is another Malta roundabout melee from 2016.  According to Police a Mack dump truck failed to yield and drove over the center median and into a tractor-trailer headed south on Round Lake Road in the roundabout.  These roundabouts are causing a lot of excitement for the good people of Malta.

Police: Overweight truck caused Malta roundabout crash
http://www.timesunion.com/local/article/Police-Overweight-truck-caused-Malta-roundabout-6871246.php#photo-9504846
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on October 21, 2017, 10:12:54 AM
I assume you will continue to report on all collisions that occur at roundabouts, because it can be assumed that the circular nature of the junction is the main cause?

There were a string of posts about the Malta roundabout (not brought up by me i'll add) and someone had mentioned that they haven't heard complaints about accidents at them.  Three months ago a truck tips over, spills over 2000 gallons of liquefied asphalt additive, creates a hazmat situation that shuts the roundabout for 12 hours, and a 6-year old boy is transported to the hospital after he cuts his head open... and nobody is complaining about accidents?  This became an event for the town of Malta that day.
So...one recent accident...and we are certain the roundabout is to blame.


Here is another Malta roundabout melee from 2016.  According to Police a Mack dump truck failed to yield and drove over the center median and into a tractor-trailer headed south on Round Lake Road in the roundabout.  These roundabouts are causing a lot of excitement for the good people of Malta.

Police: Overweight truck caused Malta roundabout crash
http://www.timesunion.com/local/article/Police-Overweight-truck-caused-Malta-roundabout-6871246.php#photo-9504846
That isn't the roundabout's fault.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 21, 2017, 10:15:05 AM
I assume you will continue to report on all collisions that occur at roundabouts, because it can be assumed that the circular nature of the junction is the main cause?

There were a string of posts about the Malta roundabout (not brought up by me i'll add) and someone had mentioned that they haven't heard complaints about accidents at them.  Three months ago a truck tips over, spills over 2000 gallons of liquefied asphalt additive, creates a hazmat situation that shuts the roundabout for 12 hours, and a 6-year old boy is transported to the hospital after he cuts his head open... and nobody is complaining about accidents?  This became an event for the town of Malta that day.
So...one recent accident...and we are certain the roundabout is to blame.


Here is another Malta roundabout melee from 2016.  According to Police a Mack dump truck failed to yield and drove over the center median and into a tractor-trailer headed south on Round Lake Road in the roundabout.  These roundabouts are causing a lot of excitement for the good people of Malta.

Police: Overweight truck caused Malta roundabout crash
http://www.timesunion.com/local/article/Police-Overweight-truck-caused-Malta-roundabout-6871246.php#photo-9504846
Frankly speaking, that is almost a non-event compared to what could happen. That roundabout is a route for hazmat trucks going to GF. If a truckload of something like RFNA or TMAH is spilled, now that would make CNN headlines..
The only hope is that those drivers are better trained - I talked to someone who was almost sidesweeped by the same truck on a highway few minutes before the accident..
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 21, 2017, 10:19:48 AM
I assume you will continue to report on all collisions that occur at roundabouts, because it can be assumed that the circular nature of the junction is the main cause?

There were a string of posts about the Malta roundabout (not brought up by me i'll add) and someone had mentioned that they haven't heard complaints about accidents at them.  Three months ago a truck tips over, spills over 2000 gallons of liquefied asphalt additive, creates a hazmat situation that shuts the roundabout for 12 hours, and a 6-year old boy is transported to the hospital after he cuts his head open... and nobody is complaining about accidents?  This became an event for the town of Malta that day.
So...one recent accident...and we are certain the roundabout is to blame.


Here is another Malta roundabout melee from 2016.  According to Police a Mack dump truck failed to yield and drove over the center median and into a tractor-trailer headed south on Round Lake Road in the roundabout.  These roundabouts are causing a lot of excitement for the good people of Malta.

Police: Overweight truck caused Malta roundabout crash
http://www.timesunion.com/local/article/Police-Overweight-truck-caused-Malta-roundabout-6871246.php#photo-9504846
That isn't the roundabout's fault.
Of course, 99.999% of drivers can make it safe through roundabout. Actually, even 99.999% correspond to quite high accident rate of 10 MEV.
It is that remaining 0.001% that need to be taken into account by design to be truly safe. And that 0.001% also includes drunk, sick, distressed, distracted... Designers must take them into account as well...
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on October 21, 2017, 10:51:01 AM
I have been wondering if tradephoric has been keeping track of roundabouts that he has highlighted over time.

Pretty sure incidents drop off on a lot of them just like engineers say they do.
I'm afraid it is more difficult than it sounds. Full statistics is not easy to come across, and not all accidents get into the news.
Ones in Malta seems to come up once in a while in mostly negative light. Those are what, 10+ years old? No real improvement... 

So, trade is able to find and download statistics on every intersection throughout an entire region whenever it shows a roundabout is at the top of the list, but once those accidents go down suddenly the statistics can't be found?

And as far as accidents getting into the news, from my experiences almost no accident makes it in the news.  If a roundabout accident is in the news, there's probably a hundred others at normal intersections that didn't make the news.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 21, 2017, 11:01:55 AM
I have been wondering if tradephoric has been keeping track of roundabouts that he has highlighted over time.

Pretty sure incidents drop off on a lot of them just like engineers say they do.
I'm afraid it is more difficult than it sounds. Full statistics is not easy to come across, and not all accidents get into the news.
Ones in Malta seems to come up once in a while in mostly negative light. Those are what, 10+ years old? No real improvement... 

So, trade is able to find and download statistics on every intersection throughout an entire region whenever it shows a roundabout is at the top of the list, but once those accidents go down suddenly the statistics can't be found?

And as far as accidents getting into the news, from my experiences almost no accident makes it in the news.  If a roundabout accident is in the news, there's probably a hundred others at normal intersections that didn't make the news.

That is the problem - sometimes data slips out, but I - as a regular driver - have little ways to know actual numbers. Trade may be able to find those numbers somewhere, but there is no go-to place for all the data - at least in NY. Many states have traffic count data available, but accident rates seem to be not published. Probably something can be FOILed, but that seems too much effort..
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 21, 2017, 01:56:05 PM
I have been wondering if tradephoric has been keeping track of roundabouts that he has highlighted over time.

Pretty sure incidents drop off on a lot of them just like engineers say they do.
I'm afraid it is more difficult than it sounds. Full statistics is not easy to come across, and not all accidents get into the news.
Ones in Malta seems to come up once in a while in mostly negative light. Those are what, 10+ years old? No real improvement... 

So, trade is able to find and download statistics on every intersection throughout an entire region whenever it shows a roundabout is at the top of the list, but once those accidents go down suddenly the statistics can't be found?

State and Ellsworth crash history:
2012:  16 crashes (#6,321 most crashes in Michigan… give or take).
2013:  Roundabout constructed
2014:  168 crashes (#1 most crashes in Michigan)
2015:  114 crashes (#7 most crashes in Michigan)
2016:  120 crashes (#7 most crashes in Michigan)

You can look at this two ways.  A roundabout proponent can argue that crashes have dropped nearly 30% since the roundabout opened in 2013.  But if you compare the post-roundabout crashes to the pre-roundabout crashes, then crashes have increased by over 650%.  Also accidents increased from 2015 to 2016 suggesting a plateau in the reduction of crashes moving forward.  Does it really matter that there has been a drop off in crashes at the roundabout and it's no longer the most crash prone intersection in Michigan?  Now it's only the 7th most crash prone intersection in Michigan (where before it was 6,321st on the list).  Time to celebrate how safe roundabouts are!  WOOHOO!

A newly constructed roundabout at 14 Mile and Orchard Lake has earned the #1 spot as the most crash prone intersection in Michigan.  That roundabout saw 146 crashes in 2016 — with 27 causing injury.  Just because the accidents will likely drop in the coming years doesn’t mean it’s not problematic.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on October 21, 2017, 02:22:39 PM
I have been wondering if tradephoric has been keeping track of roundabouts that he has highlighted over time.

Pretty sure incidents drop off on a lot of them just like engineers say they do.
I'm afraid it is more difficult than it sounds. Full statistics is not easy to come across, and not all accidents get into the news.
Ones in Malta seems to come up once in a while in mostly negative light. Those are what, 10+ years old? No real improvement... 

So, trade is able to find and download statistics on every intersection throughout an entire region whenever it shows a roundabout is at the top of the list, but once those accidents go down suddenly the statistics can't be found?

State and Ellsworth crash history:
2012:  16 crashes (#6,321 most crashes in Michigan… give or take).
2013:  Roundabout constructed
2014:  168 crashes (#1 most crashes in Michigan)
2015:  114 crashes (#7 most crashes in Michigan)
2016:  120 crashes (#7 most crashes in Michigan)

You can look at this two ways.  A roundabout proponent can argue that crashes have dropped nearly 30% since the roundabout opened in 2013.  But if you compare the post-roundabout crashes to the pre-roundabout crashes, then crashes have increased by over 650%.  Also accidents increased from 2015 to 2016 suggesting a plateau in the reduction of crashes moving forward.  Does it really matter that there has been a drop off in crashes at the roundabout and it's no longer the most crash prone intersection in Michigan?  Now it's only the 7th most crash prone intersection in Michigan (where before it was 6,321st on the list).  Time to celebrate how safe roundabouts are!  WOOHOO!

A newly constructed roundabout at 14 Mile and Orchard Lake has earned the #1 spot as the most crash prone intersection in Michigan.  That roundabout saw 146 crashes in 2016 — with 27 causing injury.  Just because the accidents will likely drop in the coming years doesn’t mean it’s not problematic.
But such cases do not support a blanket condemnation of roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 21, 2017, 02:36:30 PM
I have been wondering if tradephoric has been keeping track of roundabouts that he has highlighted over time.

Pretty sure incidents drop off on a lot of them just like engineers say they do.
I'm afraid it is more difficult than it sounds. Full statistics is not easy to come across, and not all accidents get into the news.
Ones in Malta seems to come up once in a while in mostly negative light. Those are what, 10+ years old? No real improvement... 

So, trade is able to find and download statistics on every intersection throughout an entire region whenever it shows a roundabout is at the top of the list, but once those accidents go down suddenly the statistics can't be found?

State and Ellsworth crash history:
2012:  16 crashes (#6,321 most crashes in Michigan… give or take).
2013:  Roundabout constructed
2014:  168 crashes (#1 most crashes in Michigan)
2015:  114 crashes (#7 most crashes in Michigan)
2016:  120 crashes (#7 most crashes in Michigan)

You can look at this two ways.  A roundabout proponent can argue that crashes have dropped nearly 30% since the roundabout opened in 2013.  But if you compare the post-roundabout crashes to the pre-roundabout crashes, then crashes have increased by over 650%.  Also accidents increased from 2015 to 2016 suggesting a plateau in the reduction of crashes moving forward.  Does it really matter that there has been a drop off in crashes at the roundabout and it's no longer the most crash prone intersection in Michigan?  Now it's only the 7th most crash prone intersection in Michigan (where before it was 6,321st on the list).  Time to celebrate how safe roundabouts are!  WOOHOO!

A newly constructed roundabout at 14 Mile and Orchard Lake has earned the #1 spot as the most crash prone intersection in Michigan.  That roundabout saw 146 crashes in 2016 — with 27 causing injury.  Just because the accidents will likely drop in the coming years doesn’t mean it’s not problematic.
But such cases do not support a blanket condemnation of roundabouts.

Actually they may.
If this is statistics for one in a group of 10 similar roundabouts constructed in the city, and others demonstrated 3x reduction of accidents - we're still in the red.

Or, to put it in perspective.. you went to a shop to get new tires. Mechanics did a great job.. mostly great job - just one of the wheels fell off on your way home. Are you going to return to that shop for future service?
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on October 21, 2017, 02:45:58 PM
But such cases do not support a blanket condemnation of roundabouts.

Actually they may.
If this is statistics for one in a group of 10 similar roundabouts constructed in the city, and others demonstrated 3x reduction of accidents - we're still in the red.

Or, to put it in perspective.. you went to a shop to get new tires. Mechanics did a great job.. mostly great job - just one of the wheels fell off on your way home. Are you going to return to that shop for future service?

Based on that perspective, and comparing it to the very previous sentence, we would need to compare that shop to 10 other similar shops in the city.  Your first paragraph appears to say that if 4 out of 10 of something doesn't work right, then we need to get rid of all of them.  Your second paragraph alludes to just avoiding one shop, not writing off all mechanics.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 21, 2017, 05:59:13 PM
But such cases do not support a blanket condemnation of roundabouts.

Actually they may.
If this is statistics for one in a group of 10 similar roundabouts constructed in the city, and others demonstrated 3x reduction of accidents - we're still in the red.

Or, to put it in perspective.. you went to a shop to get new tires. Mechanics did a great job.. mostly great job - just one of the wheels fell off on your way home. Are you going to return to that shop for future service?

Based on that perspective, and comparing it to the very previous sentence, we would need to compare that shop to 10 other similar shops in the city.  Your first paragraph appears to say that if 4 out of 10 of something doesn't work right, then we need to get rid of all of them.  Your second paragraph alludes to just avoiding one shop, not writing off all mechanics.

Nope. I compare project results: roundabout vs traffic light on one hand and ABC mechanics vs XYZ car service on the other. 
In both cases I compare quality of batch of deliverables - 5-pc roundabout project in Malta vs 4-pc tire project for license plate XXXABC. Failing one roundabout in a batch is pretty much the same as failing one wheel in a batch.   
Of course, changing vendor can come into play in roundabout case; but replacing unionized NYSDOT staff along with FHWA crew is a mission impossible, akin of suggesting buying a new car not to deal with tire shop.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 21, 2017, 07:52:42 PM
I do think, the more roundabouts we have, the less stupid or inattentive drivers can get away with. But, unfortunately for us who believe "stupid is as stupid does", the government does have an obligation to ensure the safety of all drivers, the smart ones and the retards alike.

For this reason, unless collisions drop significantly over the next 10 years, I'm not sure the roundabout has a future in this country.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 21, 2017, 10:24:19 PM
I do think, the more roundabouts we have, the less stupid or inattentive drivers can get away with. But, unfortunately for us who believe "stupid is as stupid does", the government does have an obligation to ensure the safety of all drivers, the smart ones and the retards alike.

For this reason, unless collisions drop significantly over the next 10 years, I'm not sure the roundabout has a future in this country.
As my driving instructor told me - remember, you're not the only idiot who drives here!

As for roundabouts, most likely we're going through standard Gartner hype cycle. We're somewhere close  to the peak right now. Once some understanding of roundabouts drips down to state DOTs, we may see more roundabout built with some understanding of where they are appropriate and how to make them safe - not just for the sake of building cool innovative thingy. Once that happens, many of existing ones would have to meet bulldozer, meaning $$$ wasted. Human nature is hard to change, though...
(http://blog.genesis-mining.com/files/2015/09/GM_Gartner_Hype_Cycle.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 21, 2017, 10:40:07 PM
Once some understanding of roundabouts drips down to state DOTs, we may see more roundabout built with some understanding of where they are appropriate and how to make them safe - not just for the sake of building cool innovative thingy. Once that happens, many of existing ones would have to meet bulldozer, meaning $$$ wasted.

I think we're more likely to see them signalised, instead of bulldozed. That's what the UK has been doing for the last couple decades.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 21, 2017, 11:09:26 PM
Once some understanding of roundabouts drips down to state DOTs, we may see more roundabout built with some understanding of where they are appropriate and how to make them safe - not just for the sake of building cool innovative thingy. Once that happens, many of existing ones would have to meet bulldozer, meaning $$$ wasted.

I think we're more likely to see them signalised, instead of bulldozed. That's what the UK has been doing for the last couple decades.
Whatever. I bet 20 years from now these early designs would look like 2 lane undivided road posted at 90 MPH. It is all about understanding and quality engineering...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 22, 2017, 12:22:00 AM
Once some understanding of roundabouts drips down to state DOTs, we may see more roundabout built with some understanding of where they are appropriate and how to make them safe - not just for the sake of building cool innovative thingy. Once that happens, many of existing ones would have to meet bulldozer, meaning $$$ wasted.

I think we're more likely to see them signalised, instead of bulldozed. That's what the UK has been doing for the last couple decades.

Whatever. I bet 20 years from now these early designs would look like 2 lane undivided road posted at 90 MPH. It is all about understanding and quality engineering...

Even some of the early ones built maybe a decade ago are starting to show their age. Many of the early roundabouts in Maryland and Colorado have massive path overlap issues.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 26, 2017, 12:49:19 PM
The Northland and Richmond roundabout in Appleton opened on September 1.  According to Appleton Police there have been 25 reported crashes between August 31st and October 10th.  At the current crash rate, there will be 228 crashes at the roundabout in the first year of operation.  Compare that to 27 crashes in all of 2014 when it was a signalized intersection (the highest crash intersection in Appleton that year).  On the project website, the stated reason the roundabout was selected was to address the high rate of crashes that were occurring at the signaled intersection.  This is the design they came up with.

(http://static-20.sinclairstoryline.com/resources/media/e5ea2b53-be3b-4ca3-96c9-6ef588ec9840-large16x9_47ooRab.jpg)

So after 25 crashes in just 40 days, does anyone still think the roundabout will do a good job at reducing crashes at the intersection moving forward?  While there probably won't be 228 crashes per year, this roundabout could easily see 100+ crashes per year.  Their baseline is 27 crashes, and 100+ crashes is about 4X worse than that.  As long as this roundabout remains a complex 3x2 roundabout next to a busy commercial district, crashes will remain a problem.  But fear not, they will study the roundabout and throw hundreds of thousands of additional dollars to “fix”  the roundabout that they just completed.  Good job.

Crash numbers increase in new roundabout
http://fox11online.com/news/local/crash-numbers-increase-in-new-roundabout
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 26, 2017, 12:54:21 PM
A previous article indicated that the intersection averaged about 26 crashes/year between 2004 and 2012 (ie. a crash every two weeks).  Now that the roundabout is opening, you are more likely to see a crash every two days. 

That was my prediction before the Appleton roundabout even opened.  At 25 crashes in 40 days, that is a crash every 1.6 days.  When will we return to a crash every 2 weeks?  Probably never as long as it remains a complex 3x2 roundabout. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 26, 2017, 01:19:36 PM
I've never driven through a 3-lane roundabout, but I can easily imagine making a dangerous maneuver at one.  And I'm a relatively young guy who likes roundabouts; first-time drivers, the elderly, people distracted by something else...  I tell you what, I'm coming around more and more to the turbo roundabout concept.  I wasn't thrilled at first, but I think I'm starting to get it.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 26, 2017, 01:31:49 PM
I've never driven through a 3-lane roundabout, but I can easily imagine making a dangerous maneuver at one.  And I'm a relatively young guy who likes roundabouts; first-time drivers, the elderly, people distracted by something else...  I tell you what, I'm coming around more and more to the turbo roundabout concept.  I wasn't thrilled at first, but I think I'm starting to get it.
There are many great concepts floating around which never got past the concept stage, and quite a few which failed in production and were successfully abandoned.
Nuclear powered cars and planes come to mind as most relevant to this forum - although nuclear warships are out there.. Fuel cell powered everything as a more recent example. I even touched fuel cell powered car (I could get a ride if I wanted) - but didn't see any lately.



Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 26, 2017, 01:40:07 PM
I've never driven through a 3-lane roundabout, but I can easily imagine making a dangerous maneuver at one.  And I'm a relatively young guy who likes roundabouts; first-time drivers, the elderly, people distracted by something else...  I tell you what, I'm coming around more and more to the turbo roundabout concept.  I wasn't thrilled at first, but I think I'm starting to get it.
There are many great concepts floating around which never got past the concept stage, and quite a few which failed in production and were successfully abandoned.
Nuclear powered cars and planes come to mind as most relevant to this forum - although nuclear warships are out there.. Fuel cell powered everything as a more recent example. I even touched fuel cell powered car (I could get a ride if I wanted) - but didn't see any lately.

Turbo roundabouts exist in reality, though, and have since the turn of the century.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 26, 2017, 02:28:35 PM
Arguably the most famous "circle" in America is the Columbus Circle in NYC.  If you take a look at the lane markings of the Columbus Circle, a "straight arrow" is directing drivers to continue circulating the circle road (ie. the circle is the main road).  With modern roundabouts the circle is viewed as an intersection and a "straight arrow" is directing drivers to EXIT the circle.  To your average driver a circle is a circle.  Instinctively how are drivers to know if they are driving on a circle road (like the Columbus Circle in NYC) or a modern roundabout that is functioning as an intersection?  In each instance the "straight arrow" means two totally different things.  You can have very clear signage at roundabouts including the use of overhead signs, but if drivers fundamentally don't understand the meaning of a "straight arrow" then we may be doomed.

(http://c8.alamy.com/comp/FCHJ4A/looking-down-at-columbus-circle-time-warner-center-central-park-trump-FCHJ4A.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 26, 2017, 02:53:27 PM
What's your thoughts on the Long Beach/Los Alamitos Circle (if you haven't addressed it before)? It doesn't really look like anything else in the US.

According to this LA Times article from 2006, lane lines were considered, but eventually dropped, to more closely conform to the British standards of the time: https://goo.gl/n99389

(https://i.ytimg.com/vi/qRFKfERL5ZQ/maxresdefault.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 26, 2017, 02:54:05 PM
Arguably the most famous "circle" in America is the Columbus Circle in NYC.  If you take a look at the lane markings of the Columbus Circle, a "straight arrow" is directing drivers to continue circulating the circle road (ie. the circle is the main road).  With modern roundabouts the circle is viewed as an intersection and a "straight arrow" is directing drivers to EXIT the circle.  To your average driver a circle is a circle.  Instinctively how are drivers to know if they are driving on a circle road (like the Columbus Circle in NYC) or a modern roundabout that is functioning as an intersection?  In each instance the "straight arrow" means two totally different things.  You can have very clear signage at roundabouts including the use of overhead signs, but if drivers fundamentally don't understand the meaning of a "straight arrow" then we may be doomed.

(http://c8.alamy.com/comp/FCHJ4A/looking-down-at-columbus-circle-time-warner-center-central-park-trump-FCHJ4A.jpg)

Hmm.  I interpreted the arrows in the picture above to mean "don't go the wrong way around this thing"–or, better, "You're going the wrong way" if you happened to turn left.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 26, 2017, 03:00:02 PM
Arguably the most famous "circle" in America is the Columbus Circle in NYC.  If you take a look at the lane markings of the Columbus Circle, a "straight arrow" is directing drivers to continue circulating the circle road (ie. the circle is the main road).  With modern roundabouts the circle is viewed as an intersection and a "straight arrow" is directing drivers to EXIT the circle.  To your average driver a circle is a circle.  Instinctively how are drivers to know if they are driving on a circle road (like the Columbus Circle in NYC) or a modern roundabout that is functioning as an intersection?  In each instance the "straight arrow" means two totally different things.  You can have very clear signage at roundabouts including the use of overhead signs, but if drivers fundamentally don't understand the meaning of a "straight arrow" then we may be doomed.

http://c8.alamy.com/comp/FCHJ4A/looking-down-at-columbus-circle-time-warner-center-central-park-trump-FCHJ4A.jpg

Hmm.  I interpreted the arrows in the picture above to mean "don't go the wrong way around this thing"–or, better, "You're going the wrong way" if you happened to turn left.

Much like these arrows often seen at off-ramps (at least out west): https://goo.gl/buBTvN.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on October 26, 2017, 03:18:33 PM
What's your thoughts on the Long Beach/Los Alamitos Circle (if you haven't addressed it before)? It doesn't really look like anything else in the US.

According to this LA Times article from 2006, lane lines were considered, but eventually dropped, to more closely conform to the British standards of the time: https://goo.gl/n99389

Fascinating. I'd never even thought about having circles/roundabouts without lane lines. Could that be a better, less-confusing solution for problematic two/three-lane roundabouts?
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 26, 2017, 03:27:38 PM
What's your thoughts on the Long Beach/Los Alamitos Circle (if you haven't addressed it before)? It doesn't really look like anything else in the US.

According to this LA Times article from 2006, lane lines were considered, but eventually dropped, to more closely conform to the British standards of the time: https://goo.gl/n99389

Fascinating. I'd never even thought about having circles/roundabouts without lane lines. Could that be a better, less-confusing solution for problematic two/three-lane roundabouts?

My suspicion is that it might reduce one problem and augment another.  But that's just a hunch.

The famous one in Towson (MD) used to have no lines, but that's no longer the case.
(http://councilmandavidmarks.com/wp-content/uploads/2013/06/towsontraffic.jpg)

(Google imagery here (https://goo.gl/maps/jLbUMMJzvxo))
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 26, 2017, 03:41:19 PM
What's your thoughts on the Long Beach/Los Alamitos Circle (if you haven't addressed it before)? It doesn't really look like anything else in the US.

According to this LA Times article from 2006, lane lines were considered, but eventually dropped, to more closely conform to the British standards of the time: https://goo.gl/n99389

Fascinating. I'd never even thought about having circles/roundabouts without lane lines. Could that be a better, less-confusing solution for problematic two/three-lane roundabouts?

My suspicion is that it might reduce one problem and augment another.  But that's just a hunch.

'Tis the case for all traffic control devices. But it's a matter of figuring out which device is the least problematic, assuming all traffic control devices can, in some way, be interpreted improperly.

The famous one in Towson (MD) used to have no lines, but that's no longer the case.
(http://councilmandavidmarks.com/wp-content/uploads/2013/06/towsontraffic.jpg)

(Google imagery here (https://goo.gl/maps/jLbUMMJzvxo))

I suspect the Towson circle was changed for the sake of change. A lot of roundabouts in the US, especially those in New England, had "modern roundabout" markings grafted on top of them, which in theory should improve the flow and reduce collisions. But I believe that, barring a few examples, some/many have seen an increase in collisions. Perhaps with all the markings, people were starting to let their guard down? It's said that the Long Beach Circle works because of the heightened sense of awareness that comes along with no markings.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 26, 2017, 03:56:55 PM
I suspect the Towson circle was changed for the sake of change.

The Towson roundabout has gone through periodic tweaking for a good number of years, now.  Lane width, striping, curbing, and other stuff.  Basically, they've experimented with it and figured out what works and what doesn't for their particular situation.  That's not to say everything from Towson would work at another location, but I don't see Towson doing things just for the sake of change.
Title: Re: Crash prone 'modern roundabouts'
Post by: D-Dey65 on October 26, 2017, 04:07:28 PM
FDOT #7 wants to put a new one up on US 98 and Hernando CR 491 in Deschamp's Corner. I think it's a bad idea


Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 26, 2017, 04:14:41 PM
Looking at the Los Alamitos Circle on Google imagery you can tell it carries a massive amount of traffic (3 of the 4 legs at the roundabout are 6-lane roads downstream).  Also looking through the historical imagery it doesn't appear the circle has been touched for the past 25 years.  That said i don't know what the crash data is like.  Does it have 150 crashes per year?  If not, it's got fewer crashes than the highest crash roundabouts discussed so far.

Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 26, 2017, 04:25:46 PM
Looking at the Los Alamitos Circle on Google imagery you can tell it carries a massive amount of traffic (3 of the 4 legs at the roundabout are 6-lane roads downstream).  Also looking through the historical imagery it doesn't appear the circle has been touched for the past 25 years.  That said i don't know what the crash data is like.  Does it have 150 crashes per year?  If not, it's got fewer crashes than the highest crash roundabouts discussed so far.

An article from 2013 cites the Long Beach Engineering Bureau as saying the circle tops the list for accidents in the city, but doesn't say what the rate is.  That kind of data would require a call to the bureau.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 26, 2017, 04:31:37 PM
In other news, a 71 year old pedestrian was killed at the Fifth Avenue South and University Drive roundabout in Saint Cloud on Tuesday.

St. Cloud pedestrian dies after being hit at university roundabout
http://www.sctimes.com/story/news/local/2017/10/25/st-cloud-pedestrian-dies-after-being-hit-university-roundabout/799620001/

In yet other news, a deadly intersection in Nevada is going to get a roundabout.  I wonder when a deadly roundabout is going to get an intersection :hmmm:  The Westfield Blvd and 96th Street roundabout in Carmel has been the site of 3 fatalities since it was built (in each fatal crash the driver blew through the middle of the roundabout and hit a retaining wall in the central island).  The perception is roundabouts are safe and there is no public outcry to tear the roundabout down even as 3 people have lost their lives. 

Deadly intersection to get roundabout
http://www.recordcourier.com/news/local/deadly-intersection-to-get-roundabout/

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 26, 2017, 04:34:04 PM
I've never driven through a 3-lane roundabout, but I can easily imagine making a dangerous maneuver at one.  And I'm a relatively young guy who likes roundabouts; first-time drivers, the elderly, people distracted by something else...  I tell you what, I'm coming around more and more to the turbo roundabout concept.  I wasn't thrilled at first, but I think I'm starting to get it.
There are many great concepts floating around which never got past the concept stage, and quite a few which failed in production and were successfully abandoned.
Nuclear powered cars and planes come to mind as most relevant to this forum - although nuclear warships are out there.. Fuel cell powered everything as a more recent example. I even touched fuel cell powered car (I could get a ride if I wanted) - but didn't see any lately.

Turbo roundabouts exist in reality, though, and have since the turn of the century.
Planes with nuclear power plant did fly, and fuel cell cars did hit the road.  FUel cell laptops were demonstrated. Didn't make it viable in a long run, though
(https://i.pinimg.com/736x/bf/41/4d/bf414d4250fce9e303ee7a4d3332c798--funny-vintage-vintage-stuff.jpg)

Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on October 26, 2017, 04:34:26 PM
In other news, a 71 year old pedestrian was killed at the Fifth Avenue South and University Drive roundabout in Saint Cloud on Tuesday.

To be fair, it is St. Cloud we're talking about. Not exactly a stellar example of the best of humanity. :bigass: (Note that I am talking about the driver, not the pedestrian.)
Title: Re: Crash prone 'modern roundabouts'
Post by: Brian556 on October 26, 2017, 04:42:10 PM
What's your thoughts on the Long Beach/Los Alamitos Circle (if you haven't addressed it before)? It doesn't really look like anything else in the US.

According to this LA Times article from 2006, lane lines were considered, but eventually dropped, to more closely conform to the British standards of the time: https://goo.gl/n99389

Fascinating. I'd never even thought about having circles/roundabouts without lane lines. Could that be a better, less-confusing solution for problematic two/three-lane roundabouts?

My suspicion is that it might reduce one problem and augment another.  But that's just a hunch.

The famous one in Towson (MD) used to have no lines, but that's no longer the case.
(http://councilmandavidmarks.com/wp-content/uploads/2013/06/towsontraffic.jpg)

(Google imagery here (https://goo.gl/maps/jLbUMMJzvxo))

What the heck is that? An ovalabout?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 26, 2017, 05:03:39 PM
I suspect the Towson circle was changed for the sake of change.

The Towson roundabout has gone through periodic tweaking for a good number of years, now.  Lane width, striping, curbing, and other stuff.  Basically, they've experimented with it and figured out what works and what doesn't for their particular situation.  That's not to say everything from Towson would work at another location, but I don't see Towson doing things just for the sake of change.

"Change for the sake of change" was the wrong phrasing. They changed things with the understanding that, whatever the "situation" was, would improve. I assume they wouldn't change things just because they can. I would hope there was a reason. As we can see in this thread, a lot of roundabouts are built to reduce collisions, although the opposite usually occurs. I can't help but wonder if crashes increased after the modern roundabout markings were first installed.

I really want to know the stats on the Towson Circle from its construction in the late 90s, to when they made the first changes in 2007. That's a long time without changes if crashes were a problem, especially if, like you say, the city continues to modify the circle to figure out what works "best".
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 26, 2017, 05:10:29 PM
The famous one in Towson (MD) used to have no lines, but that's no longer the case.

http://councilmandavidmarks.com/wp-content/uploads/2013/06/towsontraffic.jpg

What the heck is that? An ovalabout?

There's a couple other roundabouts with similar shapes:

US-395 @ Hawthorne & Glenn Ave's, Colville, WA: https://goo.gl/wdWF45
US-101 @ Milpas St, Santa Barbara, CA: https://goo.gl/TMwxG5

I seem to recall them just being referred to as "squeezed roundabouts" but I'm pretty sure there's an official name.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on October 26, 2017, 05:22:10 PM
Maybe I've missed it, given that I haven't thoroughly read the entire thread, but I feel like there's an important nuance that this discussion seems to miss: the severity of accidents. While there sure seems to be a lot of talk about how accident rates have increased at these roundabouts, I think a key factor that seems to be overlooked is the severity. I'd much rather have, for example, 100 side-swipe accidents, which usually result in few or no injuries, than 20 head-on or side-impact collisions that could potentially result in serious injuries.

Again, maybe I missed the discussion about this because I haven't read this thread fully. Still, I think it's something to keep in mind while discussing this topic.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 26, 2017, 05:46:16 PM
We have discussed severity, and it's a point of contention amongst sides here. Tradephoric, and those that lean his direction, maintain that severe collisions at normal intersections, while technically possible, are rather uncommon, so the low crash rate of most normal intersections is considered more desirable, if choosing between the two

The other side believes that roundabouts don't produce as-severe collisions due to the angle of impact. The problem is that not all drivers are paying attention when approaching a roundabout, and if you so choose to, you can drive straight over the roundabout, and straight into whatever cars are passing through the circle. The angle of impact can be 90-degrees in these situations, and can be just as severe of a collision as a T-bone at a normal signal. Then, you have all the fender benders and side-swipes from people cocking about while driving through the roundabout. After a year, you might only have one death in a roundabout, but you also have way more collisions overall.

As a percentage of collisions, do signals have more severe collisions? Maybe. But, crashes in general are pretty uncommon, so that's not saying much.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 26, 2017, 05:54:17 PM
Maybe I've missed it, given that I haven't thoroughly read the entire thread, but I feel like there's an important nuance that this discussion seems to miss: the severity of accidents. While there sure seems to be a lot of talk about how accident rates have increased at these roundabouts, I think a key factor that seems to be overlooked is the severity. I'd much rather have, for example, 100 side-swipe accidents, which usually result in few or no injuries, than 20 head-on or side-impact collisions that could potentially result in serious injuries.

Again, maybe I missed the discussion about this because I haven't read this thread fully. Still, I think it's something to keep in mind while discussing this topic.
You need to start assigning weights  and do fine accounting to get  required "improvement"... WHich basically means concept already falls apart.
Anecdotal data: I have  huge roundabout  300 feet from my desk.  Project data: 0 fatal accidents in prior 10 years.  Since constructed ~10 years ago: at least 1 fatal accident. But this is a small price to pay in the name of safe... coolness, right?

Simple estimate: 1 death cost is about equal to cost of 100-500  sidesweep accidents. (yes, human life has a cost)  How many intersections are there with annual fatal accidents to justify 100 crashes/year on replacement roundabout?
Title: Re: Crash prone 'modern roundabouts'
Post by: US 89 on October 26, 2017, 06:21:37 PM
What's your thoughts on the Long Beach/Los Alamitos Circle (if you haven't addressed it before)? It doesn't really look like anything else in the US.

According to this LA Times article from 2006, lane lines were considered, but eventually dropped, to more closely conform to the British standards of the time: https://goo.gl/n99389

(https://i.ytimg.com/vi/qRFKfERL5ZQ/maxresdefault.jpg)

That looks like a recipe for sideswipes and disasters.

The problem with trying to be British is that the drivers who are going to go through this aren’t British.
Title: Re: Crash prone 'modern roundabouts'
Post by: Truvelo on October 26, 2017, 06:34:54 PM
I don't see any problems with that Long Beach circle. In fact it looks better than most modern designs. Too many modern roundabouts have excessive deflection on the approaches causing semi trucks to flip over. I don't see Britishness being a problem, especially when American drivers get used to them once they become common.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on October 27, 2017, 06:08:48 AM
You need to start assigning weights  and do fine accounting to get  required "improvement"... WHich basically means concept already falls apart.
Anecdotal data: I have  huge roundabout  300 feet from my desk.  Project data: 0 fatal accidents in prior 10 years.  Since constructed ~10 years ago: at least 1 fatal accident. But this is a small price to pay in the name of safe... coolness, right?

Simple estimate: 1 death cost is about equal to cost of 100-500  sidesweep accidents. (yes, human life has a cost)  How many intersections are there with annual fatal accidents to justify 100 crashes/year on replacement roundabout?

Anecdotal data is meaningless, and that sample size is so ridiculously small that it makes it even more meaningless. Also, if I have to choose, I'm going with hundreds of dinged up fenders and bumpers over one person's death. It's ridiculous to even equate the two.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 27, 2017, 06:30:55 AM
You need to start assigning weights  and do fine accounting to get  required "improvement"... WHich basically means concept already falls apart.
Anecdotal data: I have  huge roundabout  300 feet from my desk.  Project data: 0 fatal accidents in prior 10 years.  Since constructed ~10 years ago: at least 1 fatal accident. But this is a small price to pay in the name of safe... coolness, right?

Simple estimate: 1 death cost is about equal to cost of 100-500  sidesweep accidents. (yes, human life has a cost)  How many intersections are there with annual fatal accidents to justify 100 crashes/year on replacement roundabout?

Anecdotal data is meaningless, and that sample size is so ridiculously small that it makes it even more meaningless. Also, if I have to choose, I'm going with hundreds of dinged up fenders and bumpers over one person's death. It's ridiculous to even equate the two.
You're a young men with noble heart, I am an old fart who is  totally down-to-earth... May I ask how many fender benders are equal to one fatal accident in your world? 1000? 10,000? 1,000,000? Would you be willing to break every vehicle in your city if that would save one life?
Statistically speaking it will work - cities do have their fair share of road fatalities, and breaking all vehicles around should reduce this number - until a new fleet is purchased...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 27, 2017, 11:13:04 AM
I don't see any problems with that Long Beach circle. In fact it looks better than most modern designs. Too many modern roundabouts have excessive deflection on the approaches causing semi trucks to flip over. I don't see Britishness being a problem, especially when American drivers get used to them once they become common.

It seems to work pretty well. The idea of a large circle without any markings is very foreign to us Americans, particularly Southern California drivers. You can watch videos of the circle on YouTube. It seems like drivers will cut other drivers off a lot, enter without yielding, and continue circling even from the outer edge (pretty sure outer lane always exits as a matter of principle). But still doesn't seem to perform all that bad, especially considering the amount of traffic it handles (as tradephoric alluded to just above).
Title: Re: Crash prone 'modern roundabouts'
Post by: CtrlAltDel on October 27, 2017, 01:04:19 PM
You're a young men with noble heart, I am an old fart who is  totally down-to-earth... May I ask how many fender benders are equal to one fatal accident in your world? 1000? 10,000? 1,000,000? Would you be willing to break every vehicle in your city if that would save one life?
Statistically speaking it will work - cities do have their fair share of road fatalities, and breaking all vehicles around should reduce this number - until a new fleet is purchased...

Well, the FAA (admittedly not the purview here) values a human life at 5.8 million dollars. If your average fender bender causes damage in the amount of 1,500 dollars, the tipping point would be 3,867 fender benders. So, that makes a good starting point.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 27, 2017, 01:08:53 PM
You're a young men with noble heart, I am an old fart who is  totally down-to-earth... May I ask how many fender benders are equal to one fatal accident in your world? 1000? 10,000? 1,000,000? Would you be willing to break every vehicle in your city if that would save one life?
Statistically speaking it will work - cities do have their fair share of road fatalities, and breaking all vehicles around should reduce this number - until a new fleet is purchased...

Well, the FAA (admittedly not the purview here) values a human life at 5.8 million dollars. If your average fender bender causes damage in the amount of 1,500 dollars, the tipping point would be 3,867 fender benders. So, that makes a good starting point.
$1-2M is a more realistic number given that money come directly from drivers (maybe in the form of insurance).  FAA enforces extremely high standard...
And as we were talking sidesweep, I assumed 3 doors, 2 quarter panels and a headlight - a bit more than $1.5k..

Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on October 27, 2017, 01:09:47 PM
What's your thoughts on the Long Beach/Los Alamitos Circle (if you haven't addressed it before)? It doesn't really look like anything else in the US.

According to this LA Times article from 2006, lane lines were considered, but eventually dropped, to more closely conform to the British standards of the time: https://goo.gl/n99389

Fascinating. I'd never even thought about having circles/roundabouts without lane lines. Could that be a better, less-confusing solution for problematic two/three-lane roundabouts?

My suspicion is that it might reduce one problem and augment another.  But that's just a hunch.

'Tis the case for all traffic control devices. But it's a matter of figuring out which device is the least problematic, assuming all traffic control devices can, in some way, be interpreted improperly.

The famous one in Towson (MD) used to have no lines, but that's no longer the case.
(http://councilmandavidmarks.com/wp-content/uploads/2013/06/towsontraffic.jpg)

(Google imagery here (https://goo.gl/maps/jLbUMMJzvxo))

I suspect the Towson circle was changed for the sake of change. A lot of roundabouts in the US, especially those in New England, had "modern roundabout" markings grafted on top of them, which in theory should improve the flow and reduce collisions. But I believe that, barring a few examples, some/many have seen an increase in collisions. Perhaps with all the markings, people were starting to let their guard down? It's said that the Long Beach Circle works because of the heightened sense of awareness that comes along with no markings.

Thats more of a turbine square than a roundabout
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 27, 2017, 02:00:15 PM
Well, the FAA (admittedly not the purview here) values a human life at 5.8 million dollars. If your average fender bender causes damage in the amount of 1,500 dollars, the tipping point would be 3,867 fender benders. So, that makes a good starting point.
Here is a chart taken from the FHWA website detailing comprehensive crash costs by injury severity level:

Fatality (K)           $4,008,900
Disabling Injury (A)   $216,000
Evident Injury (B)   $79,000
Fatal/Injury (K/A/B)   $158,200
Possible Injury (C)   $44,900
PDO (O)   $7,400

They estimates the comprehensive crash costs of a fatal crash at $4 million.  The thing is fatal crashes are a very rare event.  To put things into perspective I took the most crash prone intersection in Michigan over the past 10 years according to SEMCOG (Haggerty & Ford Road) and broke out the Crashes by Severity:

Fatal = 0 X $4,008,900 = 0
A-Level = 8 X $216,000 = $1,728,000
B-Level = 45 X $79,000 = $3,555,000
C-Level = 131 X $44,900 = $5,881,900
PD0 = 690 X $7,400 = $5,106,000
TOTAL COST = $16,270,900

Of the 874 total crashes at Haggerty and Ford, 690 were PDO crashes and 184 were injury crashes.  There were no fatal crashes at this signalized intersection over the past 10 years.  The estimated cost for all these crashes comes to $16,270,900.  Now suppose they decide to install a roundabout at the intersection Let’s assume the roundabout will eliminate all injury crashes but it will increase PDO crashes by 4X.   
 
Fatal = 0 X $4,008,900 = 0
A-Level = 0 X $216,000 = 0
B-Level = 0 X $79,000 = 0
C-Level = 0 X $44,900 = 0
PD0 = 2760 X $7,400 = $20,424,000
TOTAL COST = $20,424,000

Maybe arguing that the roundabout will see a 4 fold increase in crashes is too high.  But there are plenty of examples of similar increases when complex roundabouts have been built.  And obviously roundabouts don’t eliminate all injury crashes.  The point is a compelling case can be made that building a roundabout at Haggerty and Ford would actually increase comprehensive crash costs at the intersection.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on October 27, 2017, 07:22:50 PM
In other news, a 71 year old pedestrian was killed at the Fifth Avenue South and University Drive roundabout in Saint Cloud on Tuesday.

St. Cloud pedestrian dies after being hit at university roundabout
http://www.sctimes.com/story/news/local/2017/10/25/st-cloud-pedestrian-dies-after-being-hit-university-roundabout/799620001/

In yet other news, a deadly intersection in Nevada is going to get a roundabout.  I wonder when a deadly roundabout is going to get an intersection :hmmm:  The Westfield Blvd and 96th Street roundabout in Carmel has been the site of 3 fatalities since it was built (in each fatal crash the driver blew through the middle of the roundabout and hit a retaining wall in the central island).  The perception is roundabouts are safe and there is no public outcry to tear the roundabout down even as 3 people have lost their lives. 

Deadly intersection to get roundabout
http://www.recordcourier.com/news/local/deadly-intersection-to-get-roundabout/

The roundabout at Westfield and 96th isn't going away.  New artwork just installed. 



Get over it.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 27, 2017, 07:55:06 PM
^^
I really wish cities would just install shrubbery within the center of circles. I don't think people drive through the middle of roundabouts very often (obviously, it would be accidental), but with a sculpture in the middle, the potential for damage and injury is much higher than with some bushes.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 28, 2017, 12:05:48 PM
The roundabout at Westfield and 96th isn't going away.  New artwork just installed. 



Get over it.

That sculpture is a touching memorial to the people who have died at the 96th and Westfield roundabout in Carmel.  The three tall-stemmed, flower-like structures represent the three people who have been killed since the roundabout opened.  In each fatal accident the driver blew through the middle of the roundabout and struck a retaining wall in the central island.  The cost of the statue, its base and installation was reported to cost $352,900.  With all that money spent, that deadly wall still remains… of course now they need to protect the memorial sculpture from getting hit.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on October 28, 2017, 04:37:25 PM
The wall (https://www.google.com/maps/@39.926761,-86.1265607,31a,55.5y,332.07h,47t/data=!3m1!1e3) isn't deadly.   It doesn't jump out in front of people.  It's well off the roadway.   The people of Carmel are not in deathly fear of driving around this roundabout.   

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 28, 2017, 06:45:50 PM
The wall (https://www.google.com/maps/@39.926761,-86.1265607,31a,55.5y,332.07h,47t/data=!3m1!1e3) isn't deadly.   It doesn't jump out in front of people.  It's well off the roadway.   The people of Carmel are not in deathly fear of driving around this roundabout.

But, consider for a moment drivers who unintentionally drive through the middle. Walls and sculptures exacerbate these crashes. No reason to make the intersection more dangerous. I'm sure the people of Carmel would be just as happy with a big garden or decorative bush display.
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on October 30, 2017, 05:21:10 AM
Speaking of 96th, Indianapolis sued Carmel to stop the latter from building more roundabouts on that stretch of road.  Indianapolis won. (https://www.indystar.com/story/news/local/hamilton-county/2017/08/10/judge-sides-indianapolis-over-carmel-dispute-over-96th-street-roundabouts/557305001/)
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on October 30, 2017, 12:10:31 PM
Speaking of 96th, Indianapolis sued Carmel to stop the latter from building more roundabouts on that stretch of road.  Indianapolis won. (https://www.indystar.com/story/news/local/hamilton-county/2017/08/10/judge-sides-indianapolis-over-carmel-dispute-over-96th-street-roundabouts/557305001/)

they didn't. every roundabout will be built except one (the one at randall drive).  also, the driver of the car that drove through that roundabout at 96th and westfield was drunk. 

Not to mention the lawsuit, as mentioned in the paper, had nothing to do with safety concerns or being crash prone. 

Quote
Although Brainard thinks the roundabouts will ease traffic, Scales has said she thinks the area is not congested enough to warrant roundabouts. She also is concerned they will hurt area businesses, particularly car dealerships along the corridor.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on October 30, 2017, 12:14:13 PM
Speaking of 96th, Indianapolis sued Carmel to stop the latter from building more roundabouts on that stretch of road.  Indianapolis won. (https://www.indystar.com/story/news/local/hamilton-county/2017/08/10/judge-sides-indianapolis-over-carmel-dispute-over-96th-street-roundabouts/557305001/)
They didn't. Every roundabout will be built except one (the one at Randall Drive).  This was recently agreed upon by both city counsels.  Construction will happen next year.
Indy didn't care except for the counselwoman who has no idea what she's talking about in her reasons in opposing them.  She was easily overruled by a counsel vote earlier this year.  She needs to go back to focusing on the streets in terrible condition in her district anyway.  One other thing that was part of the agreement was a study on adding Hawk signals to the Gray Road roundabout, and paving some roads in Indy that will be affected by the detours.  Also, the driver of the car that drove through that roundabout at 96th and Westfield was drunk.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on October 30, 2017, 12:17:00 PM
The roundabout at Westfield and 96th isn't going away.  New artwork just installed. 



Get over it.

That sculpture is a touching memorial to the people who have died at the 96th and Westfield roundabout in Carmel.  The three tall-stemmed, flower-like structures represent the three people who have been killed since the roundabout opened.  In each fatal accident the driver blew through the middle of the roundabout and struck a retaining wall in the central island.  The cost of the statue, its base and installation was reported to cost $352,900.  With all that money spent, that deadly wall still remains… of course now they need to protect the memorial sculpture from getting hit.

None of the roundabouts are going away, and when it's all said and done, Carmel will have around 7 signals in the city, 6 of which are INDOT signals that they can't change, and never will be able to, since they're US highways.  And even the one remaining city owned signal at main and rangeline is being discussed to be turned into a roundabout.  It would be a shame to see that one go, it was the first in the state, and one of the first in the US, and i dont think a roundabout would work there anyway, it's too small an area for an effective one to be built. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on October 30, 2017, 12:19:17 PM
none of the roundabouts are going away, and when it's all said and done, Carmel will have around 7 signals in the city, 6 of which are INDOT signals that they can't change, and never will be able to, since they're US highways. 

How come?  Unless there's something specific to Indy, there's nothing that prevents a US Highway from going through a roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on October 30, 2017, 12:21:49 PM
none of the roundabouts are going away, and when it's all said and done, Carmel will have around 7 signals in the city, 6 of which are INDOT signals that they can't change, and never will be able to, since they're US highways. 

How come?  Unless there's something specific to Indy, there's nothing that prevents a US Highway from going through a roundabout.

Because INDOT won't do it.  It's not impossible on 421, but it wouldn't happen any time soon, state has more important things to do in other areas.  The one on 31 and 96th will never change, would require a teardrop interchange, and i dont see them wanting to spend the money.  O and i forgot about the 2 signals at 465 and us 31.  that's just the way i see it though
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 30, 2017, 03:32:27 PM
none of the roundabouts are going away, and when it's all said and done, Carmel will have around 7 signals in the city, 6 of which are INDOT signals that they can't change, and never will be able to, since they're US highways. 

How come?  Unless there's something specific to Indy, there's nothing that prevents a US Highway from going through a roundabout.

I will also mention that roundabouts on US Routes have to go through a more stringent design process than roundabouts on local roads.  This, for example, is why US-65 Business through Branson (MO) was taken over by the city of Branson prior to the construction of the five-legged Skaggs roundabout (https://goo.gl/maps/uPiBEevL8Y12):  the hill coming south down US-65 Business was too steep for a roundabout to be allowed.  So the city took over the road, renamed it Branson Landing Blvd, and built the roundabout anyway.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on October 30, 2017, 03:34:38 PM
none of the roundabouts are going away, and when it's all said and done, Carmel will have around 7 signals in the city, 6 of which are INDOT signals that they can't change, and never will be able to, since they're US highways. 

How come?  Unless there's something specific to Indy, there's nothing that prevents a US Highway from going through a roundabout.

I will also mention that roundabouts on US Routes have to go through a more stringent design process than roundabouts on local roads.  This, for example, is why US-65 Business through Branson (MO) was taken over by the city of Branson prior to the construction of the five-legged Skaggs roundabout (https://goo.gl/maps/uPiBEevL8Y12):  the hill coming south down US-65 Business was too steep for a roundabout to be allowed.  So the city took over the road, renamed it Branson Landing Blvd, and built the roundabout anyway.

geeze even for a business route?  interesting.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 30, 2017, 03:45:41 PM
Were there any signalized intersection in Carmel that had 3 fatalities over a 10 year period before the roundabout craze began?  I can’t speak for Carmel, but according to SEMCOG there were 3 fatalities at the top 20 most crash prone intersections in SE Michigan between 2007 and 2016.  It’s just hard to believe that the top 20 most crash prone intersections in a region of 4.3 million people would have as many fatalities as some innocuous single-lane roundabout in Carmel.  If there wasn't a retaining wall in the middle of the 96th and Westfield roundabout, i believe the roundabout would be much safer and we wouldn't be having this discussion.  Here are SEMCOG’s high frequency crash locations:

(https://i.imgur.com/ZV48A5x.png)
http://semcog.org/High-Frequency-Crash-Locations
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 30, 2017, 04:13:53 PM
Speaking of 96th, Indianapolis sued Carmel to stop the latter from building more roundabouts on that stretch of road.  Indianapolis won. (https://www.indystar.com/story/news/local/hamilton-county/2017/08/10/judge-sides-indianapolis-over-carmel-dispute-over-96th-street-roundabouts/557305001/)

Councillor Scales' reasons against building the roundabout seem really shallow:

Quote from: Indy Star
Although Brainard thinks the roundabouts will ease traffic, Scales has said she thinks the area is not congested enough to warrant roundabouts. She also is concerned they will hurt area businesses, particularly car dealerships along the corridor.

What I want to know is what Scales' would prefer. Roundabouts work better in low- to mid-trafficked areas than signals (which are better along busy corridors), plus, I don't see how roundabouts, instead of signals, would have any effect on businesses. Roundabouts require more ROW at intersections, but from what I can tell, there's plenty of room along the corridor to allow for roundabouts without taking any more than a few parking spots away from the corner-based businesses.
Title: Re: Crash prone 'modern roundabouts'
Post by: TheHighwayMan394 on October 30, 2017, 05:13:30 PM
MnDOT releases a detailed study claiming massive decreases in both fatal and non-fatal incidents at intersections where roundabouts have been installed (this includes both state and non-state-built projects).

I won't comment further since I figure people will cherry-pick what they want out of the PDF.

http://www.dot.state.mn.us/trafficeng/safety/docs/roundaboutstudy.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 30, 2017, 05:23:39 PM
MnDOT releases a detailed study claiming massive decreases in both fatal and non-fatal incidents at intersections where roundabouts have been installed (this includes both state and non-state-built projects).

http://www.dot.state.mn.us/trafficeng/safety/docs/roundaboutstudy.pdf

There were 6 full dual-lane roundabouts analyzed in that Minnesota study (ie. 2x2 roundabouts).  Here is a table of the dual-lane roundabouts with before construction and after construction crash data based on crash severity:

(https://i.imgur.com/D77VC6z.png)

If we use FHWA’s comprehensive crash costs by injury severity level to perform a cost/benefit analysis, we see that these dual-lane Minnesota roundabouts increased crash costs by $1,664,300.  Even though there were 3 less A-level crashes at the roundabouts, there were 7 more C-level crashes and a whopping 270 more PDO crashes.

BEFORE ROUNDABOUT CRASH COSTS = $4,882,600
Fatality (K)           0 X $4,008,900 = $0
Disabling Injury (A)   3 X  $216,000 = $648,000
Evident Injury (B)   15 X $79,000 = $1,185,000
Possible Injury (C)   46 X $44,900 = $2,065,400
PDO (O)          133 X $7,400 =  $984,200

AFTER ROUNDABOUT CRASH COSTS = $6,546,900
Fatality (K)           0 X $4,008,900 = $0
Disabling Injury (A)   0 X  $216,000 = $0
Evident Injury (B)   15 X $79,000 = $1,185,000
Possible Injury (C)   53 X $44,900 = $2,379,700
PDO (O)          403 X $7,400 =  $2,982,200
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 30, 2017, 05:27:01 PM
I won't comment further since I figure people will cherry-pick what they want out of the PDF.

http://www.dot.state.mn.us/trafficeng/safety/docs/roundaboutstudy.pdf

I'm just happy they broke down the results by single lane, unbalanced multi-lane, and full multi-lane.  This is one of the first studies i have seen that distinguishes 2x2 multi-lane roundabouts from unbalanced 2x1 roundabouts. 
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on October 30, 2017, 05:28:13 PM
She wanted to do nothing, an Indianapolis staple. Her opposition was so obviously that she didn't like roundabouts.  Indy was paying the massive price of $0 for the project and she lied about business owners being against it, they were for it.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on October 30, 2017, 07:10:37 PM
More new roundabout art added on Hazel Dell.


(https://www.wthr.com/sites/wthr.com/files/Hazeldell-RAB-131.jpg)

(https://www.wthr.com/sites/wthr.com/files/Hazeldell-RAB-126.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 30, 2017, 07:44:57 PM
She wanted to do nothing, an Indianapolis staple. Her opposition was so obviously that she didn't like roundabouts.  Indy was paying the massive price of $0 for the project and she lied about business owners being against it, they were for it.

Her only real point is that they're building, without a permit, within the Indianapolis city limits. That should be an easy fix (hopefully a settlement will be reached as Mr Brainard hopes). I don't see why she has to make a big deal about it.

More new roundabout art added on Hazel Dell.

Bloody painful if you hit those things.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on October 30, 2017, 07:49:59 PM
She wanted to do nothing, an Indianapolis staple. Her opposition was so obviously that she didn't like roundabouts.  Indy was paying the massive price of $0 for the project and she lied about business owners being against it, they were for it.

Her only real point is that they're building, without a permit, within the Indianapolis city limits. That should be an easy fix (hopefully a settlement will be reached as Mr Brainard hopes). I don't see why she has to make a big deal about it.

More new roundabout art added on Hazel Dell.

Bloody painful if you hit those things.

they have resolved this, i need to find the link, but as i said before they will build all but one, it was recently approved by both parties.  i still think the property angle is a weak excuse to oppose it. but it was only mildly successful.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 31, 2017, 09:05:38 AM
I won't comment further since I figure people will cherry-pick what they want out of the PDF.

http://www.dot.state.mn.us/trafficeng/safety/docs/roundaboutstudy.pdf

I'm just happy they broke down the results by single lane, unbalanced multi-lane, and full multi-lane.  This is one of the first studies i have seen that distinguishes 2x2 multi-lane roundabouts from unbalanced 2x1 roundabouts. 

Seriously.  This study seems to be exactly what you've been calling for since dozens of pages ago.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 31, 2017, 09:46:44 AM
I won't comment further since I figure people will cherry-pick what they want out of the PDF.

http://www.dot.state.mn.us/trafficeng/safety/docs/roundaboutstudy.pdf

I'm just happy they broke down the results by single lane, unbalanced multi-lane, and full multi-lane.  This is one of the first studies i have seen that distinguishes 2x2 multi-lane roundabouts from unbalanced 2x1 roundabouts. 

Seriously.  This study seems to be exactly what you've been calling for since dozens of pages ago.
ANd results are quite similar to what Trade was saying... Maybe someone from MinnDOT read this thread?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 31, 2017, 04:31:52 PM
I won't comment further since I figure people will cherry-pick what they want out of the PDF.

http://www.dot.state.mn.us/trafficeng/safety/docs/roundaboutstudy.pdf

I'm just happy they broke down the results by single lane, unbalanced multi-lane, and full multi-lane.  This is one of the first studies i have seen that distinguishes 2x2 multi-lane roundabouts from unbalanced 2x1 roundabouts. 

Seriously.  This study seems to be exactly what you've been calling for since dozens of pages ago.
ANd results are quite similar to what Trade was saying... Maybe someone from MinnDOT read this thread?

Yes some vindication.  No longer are all multi-lane roundabouts being lumped together and analyzed as if they will perform equally.  In past studies the unbalanced multi-lane roundabouts would mask just how poorly these full dual-lane roundabouts were performing in terms of crash rates.    Now anybody with an irrational exuberance for roundabouts must consider the results of the MnDOT study.  They should listen to John Hourdos and other roundabout experts who realize that these complex multi-lane roundabouts aren’t working out so well.  The full dual-lane roundabouts in the MnDOT study saw a 212.5% increase in PDO crashes and a 6.3% increase in total injury crashes (even as traffic volumes decreased by 3%).  The only silver lining is that the most serious A-type crash was reduced.  But the fact remains total injury crashes went up at these Minnesota roundabouts.  For as long as we have been told that roundabouts reduce injury crashes, the research may suggest otherwise when the focus is on these complex full dual-lane roundabouts. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 02, 2017, 07:55:25 PM
Anyone know where this roundabout is? I see the photo used all the time as a stock photo, but I can't seem to find the original image with any information:

(https://19f4g9425ypu3nc2jy13bbrh-wpengine.netdna-ssl.com/wp-content/uploads/2016/12/Are-Roundabouts-Safer.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 07, 2017, 03:31:19 PM
Video of an RV blowing through the middle of a roundabout in Worthington Minnesota.  At least their wasn't a retaining wall in the central island for the driver to hit.  Nobody came to a "dead" stop, like the fate of several people at the 96th and Westfield roundabout in Carmel.  Three people have died at that Carmel roundabout already, that can be considered several right?  Luckily there wasn't a family in an RV to add to the 96th and Westfield roundabout death list.

Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 07, 2017, 04:19:09 PM
People who blow through the middle of a roundabout..... How do these people manage to make it to Wal-Mart and back?  I just don't get it.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 07, 2017, 07:56:19 PM
Video of an RV blowing through the middle of a roundabout in Worthington Minnesota.  At least their wasn't a retaining wall in the central island for the driver to hit.  Nobody came to a "dead" stop, like the fate of several people at the 96th and Westfield roundabout in Carmel.  Three people have died at that Carmel roundabout already, that can be considered several right?  Luckily there wasn't a family in an RV to add to the 96th and Westfield roundabout death list.


I think that video demonstrates exactly why those retaining walls don't make any sense. The only reason that crash wasn't any worse, was because there weren't any retaining walls in the center. Retaining walls inside the center of roundabouts are about as smart as putting concrete barriers in all of the negative space inside of an intersection. They don't allow for error.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 09, 2017, 02:23:08 PM
^Apart from the RV blowing through the middle of that Worthington Minnesota roundabout, there has been two other pretty major events at the roundabout over the past couple weeks.

Tanker hauling cream overturns in Worthington roundabout
(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/111117.N.DG_.TANKERCREAM%20rgb_0.jpg?itok=rxMKiQ4I)
http://www.dglobe.com/news/accidents/4356792-tanker-hauling-cream-overturns-worthington-roundabout


These little piggies almost didn't make it to market when a Minn. hog truck rolled

(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/102817.N.DG_.ROLLOVER%203.jpg?itok=DOQatmVs)
http://www.agweek.com/news/4350581-these-little-piggies-almost-didnt-make-it-market-when-minn-hog-truck-rolled

Cream trucks rolling over, hogs running around the highway, some RV driver thinking they are Bo Duke... these roundabouts really give the good people of Worthington Minnesota something to talk about!
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 09, 2017, 03:36:26 PM
Worthington Minnesota roundabout

It was only due to my attentiveness that I didn't get side-swiped at two of Worthington's roundabouts last month.  In fact, the experience made me think of this thread at the time.  But, since they are 2x1 rather than full 2x2, I didn't bring it up.

The main road (MN-60) is striped as two lanes in each direction through the roundabouts.  The driver next to me didn't seem to be the most capable, and seemed like the kind who drives as if she's the only one on the road.  So I decided to lag behind just a little bit as we drove through–which was fortunate, because she took both lanes and would have run into me if I hadn't lagged behind.  At the next roundabout, it was the same thing.  Good thing for me, she was getting off the highway at that second roundabout–turning left, I might add, from the right entry lane.  I can understand trucks and buses taking two lanes through a roundabout, but pure disregard for other drivers is just really irritating to me.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 09, 2017, 04:00:20 PM
I seem to recall that, when the MUTCD was starting to draw up some "modern roundabout" standards, that all roundabouts would have truck aprons, instead of wider-than-normal circulating lanes, because drivers have a tendency to take the fastest line. Since most drivers aren't too keen on driving on curbs, the apron came into play to ensure that drivers, assuming they were paying attention, would not attempt to take the fast line through the roundabout, but still allow trucks room to navigate through the circle.

Unfortunately, when a roundabout has two lanes, it's much easier for an inattentive driver to simply ignore all the markings, and take the fastest line anyway. I can understand doing this when no one else is around. I drive over lane lines when I'm "rushing" all the time. But people do seem to forget that they aren't the only ones driving, so you get some close calls like ^above^.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 09, 2017, 04:41:36 PM
Wouldn't it make more sense to have depressed truck aprons as opposed to raised truck aprons at roundabouts?  Raising one side of the trailer up 5 or 6 inches as they ride the apron curbing in the middle of a sweeping turn sounds like it's a recipe for a tip-over.  If the apron was depressed, it would  be counteracting the centrifugal force of the trailer wanting to tip.  I'm sure someone who has researched truck aprons will tell me why a depressed apron would be a horrible idea, but i do know there are a lot of trucks tipping over at roundabouts (that Worthington roundabout has seen 2 in the past 2 weeks alone).  Just look at the picture below and you see the trailer leaning to one side as it climbs the curbing.

(https://i.ytimg.com/vi/jGM8UGfgeMg/maxresdefault.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 09, 2017, 04:46:58 PM
Wouldn't it make more sense to have depressed truck aprons as opposed to raised truck aprons at roundabouts?  Raising one side of the trailer up 5 or 6 inches as they ride the apron curbing in the middle of a sweeping turn sounds like it's a recipe for a tip-over.  If the apron was depressed, it would  be counteracting the centrifugal force of the trailer wanting to tip.  I'm sure someone who has researched truck aprons will tell me why a depressed apron would be a horrible idea, but i do know there are a lot of trucks tipping over at roundabouts (that Worthington roundabout has seen 2 in the past 2 weeks alone).  Just look at the picture below and you see the trailer leaning to one side as it climbs the curbing.

[img

Drainage, for one thing.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 09, 2017, 08:15:17 PM
(https://i.ytimg.com/vi/jGM8UGfgeMg/maxresdefault.jpg)

Pretty sure I recognised that roundabout...near Vernon, BC (if anyone's curious): https://goo.gl/zAuqC9

The city of Vernon re-worked a few of their right-turn slip lanes at a few of their intersections to include truck aprons, and are raised in much the same as those you see at roundabouts: https://goo.gl/rvPMMy (note the red stamped concrete). Not aware of any rollovers at these intersections.

I'm sure someone who has researched truck aprons will tell me why a depressed apron would be a horrible idea

Drainage, for one thing.

I don't think that would present too much of an issue, as long the grade was kept between like 1-3%. You'd need to have a part of the apron be slightly deeper than the rest, and the water would drain to that point. Just hookup a sewer, and you're golden.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 10, 2017, 01:21:57 PM
(https://i.ytimg.com/vi/jGM8UGfgeMg/maxresdefault.jpg)

Pretty sure I recognised that roundabout...near Vernon, BC (if anyone's curious): https://goo.gl/zAuqC9

The city of Vernon re-worked a few of their right-turn slip lanes at a few of their intersections to include truck aprons, and are raised in much the same as those you see at roundabouts: https://goo.gl/rvPMMy (note the red stamped concrete). Not aware of any rollovers at these intersections.

Aren't roundabouts already constructed such that water drains away from the center island?  Assuming that's correct, then the truck apron at a roundabout exists on a slope–which also happens to slope in the same direction of centrifugal force.  Alongside a typical intersection, any such slope would be counteracting the centrifugal force of a turn.  FWIW, I think the apron implementation you linked to is a great idea.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 13, 2017, 11:41:16 AM
There was a presentation about geometric parameters that affect truck stability at the international roundabout conference this year in Green Bay.  They simulated the Rollover Index (RI) which is the relative difference in loading on left versus right side of truck at the rear axles.  Here are some of the key findings (most of these seem to be common sense):

-RI decreased with increase in ICD.
-RI lower in right lane than left.
-RI decreases most significantly when lowering truck speed from 15 mph to 10 mph.
-RI lower with crowned section than with constant outward slope.
-Higher rollover risk when encountering a modeled 3-inch vertical face truck apron. 

They also compared different truck types and loading to determine which were more susceptible to rollovers.  The key findings of truck type and loads are the following:

-WB-67 trucks less stable than SU-30 and B-train at smaller, single-lane roundabouts
-Empty trucks (WB-67 and B-train) at higher risk of rollover in small roundabouts.
-Fully loaded trucks higher risk in two-lane roundabouts due to higher center of gravity
-Non-static loads (unsecured or liquid loads) not tested.


Review of Fatal and Severe Injury Crashes and Evaluation of Geometric Parameters that Affect Truck Stability

http://teachamerica.com/RAB17/RAB172A_Steyn/index.htm
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 13, 2017, 12:30:31 PM
There was a presentation about geometric parameters that affect truck stability at the international roundabout conference this year in Green Bay.  They simulated the Rollover Index (RI) which is the relative difference in loading on left versus right side of truck at the rear axles.  Here are some of the key findings (most of these seem to be common sense):

-RI decreased with increase in ICD.
-RI lower in right lane than left.
-RI decreases most significantly when lowering truck speed from 15 mph to 10 mph.
-RI lower with crowned section than with constant outward slope.
-Higher rollover risk when encountering a modeled 3-inch vertical face truck apron. 

They also compared different truck types and loading to determine which were more susceptible to rollovers.  The key findings of truck type and loads are the following:

-WB-67 trucks less stable than SU-30 and B-train at smaller, single-lane roundabouts
-Empty trucks (WB-67 and B-train) at higher risk of rollover in small roundabouts.
-Fully loaded trucks higher risk in two-lane roundabouts due to higher center of gravity
-Non-static loads (unsecured or liquid loads) not tested.


Review of Fatal and Severe Injury Crashes and Evaluation of Geometric Parameters that Affect Truck Stability

http://teachamerica.com/RAB17/RAB172A_Steyn/index.htm
So rollover is the dominant problem for trucks... Interesting... and slowing down to pedestrian pace is the solution? 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 13, 2017, 02:26:57 PM
What pedestrian walks at 10mph?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 13, 2017, 03:43:16 PM
This PDF (https://goo.gl/Pmy8ib) from Teach America covers the roundabout design guidelines in Germany. As it relates to the topic at hand, Germany does not use truck aprons at all for larger roundabouts, and uses a much shorter variation at smaller single-lane roundabouts. The apron, rather than the raised type seen in the US, is more of a slight bump, composed of asphalt, stamped concrete, or bricks (judging by the pictures on page 6). Larger (rural) single-lane roundabouts do not have truck aprons because the diameter does not require them, and multi-lane roundabouts also do not require them because of the additional pavement width. Something tells me Germany doesn't have quite the same rollover issues.

Page 11 also covers the landscaping of roundabouts. Roundabouts on state highways used to have quite a few large structures built in the middle, but after a very severe collision that killed two people, the government ordered a review, and many of the structures were removed. For the most part, the middle of roundabouts no longer have any vertical elements, such as columns, trees, or rocks. Roundabouts in low-speed urban environments do not have the same restrictions (although all decorations must be approved).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 13, 2017, 07:26:21 PM
This PDF (https://goo.gl/Pmy8ib) from Teach America covers the rounbabout design guidelines in Germany. As it relates to the topic at hand, Germany does not use truck aprons at all for larger roundabouts, and uses a much shorter variation at smaller single-lane roundabouts. The apron, rather than the raised type seen in the US, is more of a slight bump, composed of asphalt, stamped concrete, or bricks (judging by the pictures on page 6). Larger (rural) single-lane roundabouts do not have truck aprons because the diameter does not require them, and multi-lane roundabouts also do not require them because of the additional pavement width. Something tells me Germany doesn't have quite the same rollover issues.

Page 11 also covers the landscaping of roundabouts. Roundabouts on state highways used to have quite a few large structures built in the middle, but after a very severe collision that killed two people, the government ordered a review, and many of the structures were removed. For the most part, the middle of roundabouts no longer have any vertical elements, such as columns, trees, or rocks. Roundabouts in low-speed urban environments do not have the same restrictions (although all decorations must be approved).

Another nice chart is the one with roundabouts types and dimensions for different traffic volumes.
Once a 100 ft = 30 m roundabout is put into a 52k traffic intersection - while german standard calls for a signalized one with 60m=200' dia minimum, you do get one of most dangerous intersections in the area... I wonder if NYSDOT did that on purpose..
Overall, comparing those guidelines with actual NYS structures provides a nice demo of indoctrination that roundabouts are assumingly superior design - without understanding of limitations.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 13, 2017, 09:07:54 PM
Here is that chart from Germany that looks at roundabouts based on ICD and ADT.  Ignoring signalized roundabouts, the cap for the applicability of roundabouts in Germany is about 30,000 ADT.   

(https://i.imgur.com/FiKKPn3.png)

Here is an equivalent chart taken from the FHWA website.  The cap for the likely acceptability of double-lane roundabouts in the US is about 30,000 AADT (the same as Germany).   Roundabouts may be sufficient at higher AADT but additional analysis would be needed. 

(https://i.imgur.com/DvlD2eH.png)


The M-5 and Pontiac Trail roundabout in Michigan has an AADT approaching 55,000.  That’s almost double the cap that Germany and the FHWA set as an acceptable volume for roundabouts.  A complex triple-lane roundabout with daily traffic volumes approaching 55,000 AADT isn’t going to perform the same as a simple single-lane roundabout with 15,000 AADT... the type of roundabout analyzed in the IIHS study back in 2000 that really started the roundabout indoctrination.  And maybe the roundabouts built back in the early 2000s are great, but the roundabouts being built in America today are a whole other beast!
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 13, 2017, 11:11:09 PM
The M-5 and Pontiac Trail roundabout in Michigan has an AADT approaching 55,000.

Fucking hell. Do you know what the AADT was before the roundabout was installed?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 13, 2017, 11:59:59 PM
The M-5 and Pontiac Trail roundabout in Michigan has an AADT approaching 55,000.

Fucking hell. Do you know what the AADT was before the roundabout was installed?

Before it was T-intersection and now it's a 4-leg roundabout.  With one less leg of traffic, volumes before the roundabout were inevitably lower (can't find an exact number.. my guess would be 35-40k).  By the way the 55,000 AADT may be conservative.  According to this article the spokesperson for the Road Commission of Oakland County says the roundabout carries 60,000 trips per day.

http://www.wxyz.com/news/region/oakland-county/despite-166-accidents-officials-say-roundabout-makes-m-5pontiac-trail-intersection-safer
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 14, 2017, 05:53:43 AM
The M-5 and Pontiac Trail roundabout in Michigan has an AADT approaching 55,000.

Fucking hell. Do you know what the AADT was before the roundabout was installed?
I don't think anyone cared. Roundabouts are seen as an ultimate high throughput solution and a good fit for any situation.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 14, 2017, 10:58:12 AM
The M-5 and Pontiac Trail roundabout in Michigan has an AADT approaching 55,000.

Fucking hell. Do you know what the AADT was before the roundabout was installed?
I don't think anyone cared. Roundabouts are seen as an ultimate high throughput solution and a good fit for any situation.

Watch any PM rush at the M-5/Pontiac Trail roundabout and you see drivers on WB Pontiac Trail backed up to the Walmart just creeping along at a snail’s pace.  It routinely takes 10-15 minutes to get through the roundabout.  That is equivalent to drivers waiting 5-8 cycles to get through a light that is running a 120 second cycle.  The problem is NB M-5 traffic is so dominate that it overtakes the roundabout and there are very few gaps for WB Pontiac Trail traffic to enter.  High AADT roundabouts can break down pretty badly during rush hour especially when a dominate leg is present. 

When another major roundabout was being proposed in the area, they put together a traffic model using estimated 2035 Peak hour volumes.  Now that the 14 Mile and Orchard Lake roundabout has been built, it’s laughable at how inaccurate the model was at depicting real world conditions.  There is a traffic signal literally 175 feet upstream from the roundabout and we are to believe that traffic will never back up through the roundabout?  Somebody should really take some drone footage of the roundabout and compare it to this model.  By the way, this roundabout was the most crash prone intersection in Michigan in 2016 experiencing 163 crashes including 27 injury crashes. 


Now that we know what we know... 163 crashes, 27 injury crashes, traffic that routinely backs up through the roundabout.... was this roundabout a good idea?  Even the most ardent supporters of roundabouts should question that.

14-Orchard roundabout is tops for accidents, but is it really dangerous?
http://www.freep.com/story/news/local/michigan/oakland/2017/04/04/orchard-roundabout-tops-accidents-really-dangerous/100046220/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 17, 2017, 11:00:02 AM
1 person dies when car slams into tree in Summerlin roundabout
https://www.reviewjournal.com/local/summerlin/1-person-dies-when-car-slams-into-tree-in-summerlin-roundabout/

A fatal crash happened at the Village Center Circle and Hills Center Drive roundabout in Summerland, NV on Wednesday night.  The Village Center Circle roundabout is credited as being the first modern roundabout built in America.  The driver was able to get out of the vehicle but the passenger had to be freed by rescue personal and was pronounced dead at the hospital.  Here is a streetview of the central island:

(https://i.imgur.com/dR9E254.jpg)

Some brush and shrubs planted throughout the large central island would be effective at slowing down an out of control driver without the vehicle coming to a "dead stop".  Blowing through 50 yards of shrubbery would get a drunk driver's attention and probably disable their vehicle.  Then the driver can be placed in handcuffs instead of being placed on a gurney after slamming into a palm tree.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on November 17, 2017, 11:16:40 AM
Some brush and shrubs planted throughout the large central island would be effective at slowing down an out of control driver without the vehicle coming to a "dead stop".  Blowing through 50 yards of shrubbery would get a drunk driver's attention and probably disable their vehicle.  Then the driver can be placed in handcuffs instead of being placed on a gurney after slamming into a palm tree.

The driver was placed in handcuffs for DUI.  It was the passenger who died.

Then again, there's something she could've been wearing that might've reduced her chances of dying as well.

Quote
His 56-year-old female passenger, who wasn’t wearing a seat belt...

While the roundabout was where the fatal accident occurred, better them slamming into a tree than into another innocent vehicle.

And, as this is supposedly the 'first' modern roundabout, if there have been no other fatal accidents here, speaks to how well the roundabout has worked over the years.  Even the most safest roads will have a rare fatal on occasion; mostly due to other circumstances, which in this case was a drunk driver transporting an unbuckled passenger.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 17, 2017, 11:51:30 AM
Some brush and shrubs planted throughout the large central island would be effective at slowing down an out of control driver without the vehicle coming to a "dead stop".  Blowing through 50 yards of shrubbery would get a drunk driver's attention and probably disable their vehicle.  Then the driver can be placed in handcuffs instead of being placed on a gurney after slamming into a palm tree.

The driver was placed in handcuffs for DUI.  It was the passenger who died.

Then again, there's something she could've been wearing that might've reduced her chances of dying as well.

Quote
His 56-year-old female passenger, who wasn’t wearing a seat belt...

While the roundabout was where the fatal accident occurred, better them slamming into a tree than into another innocent vehicle.

And, as this is supposedly the 'first' modern roundabout, if there have been no other fatal accidents here, speaks to how well the roundabout has worked over the years.  Even the most safest roads will have a rare fatal on occasion; mostly due to other circumstances, which in this case was a drunk driver transporting an unbuckled passenger.

In a grand scheme of things, most of the roads around are incredibly safe. We're talking about average crash rate of (round up to make my calc easier) of 10 in 1 million per intersection.
I am going through about 10 intersections a day - that means I (assuming I am an average driver) can expect 1 crash in 10 000 days - or 1 in 30 years,  give or take. And most of those crashes are property only..
With that - significant number of those accidents are due to driver being not fit to drive or making a mistake. Drunk, sick, old, under influence, stressed, tired, on the phone, unnecessary changing lanes, rushed through traffic light  etc. Alert and attentive driver is much safer than average.
And if you want to keep accidents in check - you need to take those drivers into account. Yes, we need to push for DUI awareness etc - but extermination of offenders is not the only approach
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 17, 2017, 01:36:30 PM
Why is it even possible to drive a straight path into the center island?  Shouldn't deflection direct a driver away from that?  Guardrails (guiderails?) along the approaches might help with that.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 17, 2017, 01:58:13 PM
Why is it even possible to drive a straight path into the center island?  Shouldn't deflection direct a driver away from that?  Guardrails (guiderails?) along the approaches might help with that.
Guardrails look fairly ugly for urban locations. And with those curved approaches, number of expensive property-only accidents would go up as people would scrape those rails - while now it is just running the curb.
Some soft stopping items in central island - no trees no concrete - seem to be the least evil.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 17, 2017, 02:02:22 PM
While the roundabout was where the fatal accident occurred, better them slamming into a tree than into another innocent vehicle.
As mentioned in another thread, retractable bollards should be added at signalized intersections.  The bollards would extend up when the signal turns red.  It is better for a red light driver to slam into a bollard than to T-bone somebody already in the intersection.  Would you be in favor of this idea?  I found a crash test on youtube that simulates a red light runner plowing into the bollards.
 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 17, 2017, 02:18:58 PM
While the roundabout was where the fatal accident occurred, better them slamming into a tree than into another innocent vehicle.
As mentioned in another thread, retractable bollards should be added at signalized intersections.  The bollards would extend up when the signal turns red.  It is better for a red light driver to slam into a bollard than to T-bone somebody already in the intersection.  Would you be in favor of this idea?  I found a crash test on youtube that simulates a red light runner plowing into the bollards.
 

No, inattentive drivers might rear-end someone being stopped by a retractable bollard.



Why is it even possible to drive a straight path into the center island?  Shouldn't deflection direct a driver away from that?  Guardrails (guiderails?) along the approaches might help with that.
Guardrails look fairly ugly for urban locations. And with those curved approaches, number of expensive property-only accidents would go up as people would scrape those rails - while now it is just running the curb.
Some soft stopping items in central island - no trees no concrete - seem to be the least evil.

I think we should just construct everything out of Nerf.  Then people can get away without knowing how to drive at all and still not get injured.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 17, 2017, 02:39:28 PM
The Village Center Circle roundabout is credited as being the first modern roundabout built in America.

Huh, so they were. I always thought the first two were the roundabouts at Hualapai Way and Canyon Run Drive, along Town Center Drive (both full 3x3 roundabouts). However, those didn't fully open until the late 90s! I was way off; the first two along Village Center Circle opened up in 1990. Neither of the Town Center Drive roundabouts must have been very safe, since they replaced the far right lane of each with slip lanes in the early 2000s. They were definitely the first full 3x3 roundabouts in this country, though (the Village Center/Town Drive roundabout had three lanes, but it was more of a T-approach with a driveway at the top) -- although, now that I think of it, I'm not sure any full 3x3 roundabouts were ever built beyond those two? Every other three-lane roundabout has a part with only two lanes.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 17, 2017, 03:05:52 PM
I think we should just construct everything out of Nerf.  Then people can get away without knowing how to drive at all and still not get injured.
I still believe red light cameras should be replaced with red light machine guns. You know, just shoot that damn criminal on the spot!
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 17, 2017, 03:11:04 PM
I think we should just construct everything out of Nerf.  Then people can get away without knowing how to drive at all and still not get injured.
I still believe red light cameras should be replaced with red light machine guns. You know, just shoot that damn criminal on the spot!

But then the car might crash into the central island of a nearby roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 17, 2017, 03:16:53 PM
I think we should just construct everything out of Nerf.  Then people can get away without knowing how to drive at all and still not get injured.
I still believe red light cameras should be replaced with red light machine guns. You know, just shoot that damn criminal on the spot!

But then the car might crash into the central island of a nearby roundabout.
OK, make it red light grenade launcher.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 17, 2017, 03:26:55 PM
I think we should just construct everything out of Nerf.  Then people can get away without knowing how to drive at all and still not get injured.
I still believe red light cameras should be replaced with red light machine guns. You know, just shoot that damn criminal on the spot!

But then the car might crash into the central island of a nearby roundabout.
OK, make it red light grenade launcher.

too bulky
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on November 17, 2017, 03:28:19 PM
I think we should just construct everything out of Nerf.  Then people can get away without knowing how to drive at all and still not get injured.
I still believe red light cameras should be replaced with red light machine guns. You know, just shoot that damn criminal on the spot!

But then the car might crash into the central island of a nearby roundabout.
OK, make it red light grenade launcher.

too bulky

Only briefly. Or are we talking about the launcher and not the red light runner? :bigass:
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 17, 2017, 03:35:35 PM
The Village Center Circle roundabout is credited as being the first modern roundabout built in America.

Huh, so they were. I always thought the first two were the roundabouts at Hualapai Way and Canyon Run Drive, along Town Center Drive (both full 3x3 roundabouts). However, those didn't fully open until the late 90s! I was way off; the first two along Village Center Circle opened up in 1990. Neither of the Town Center Drive roundabouts must have been very safe, since they replaced the far right lane of each with slip lanes in the early 2000s. They were definitely the first full 3x3 roundabouts in this country, though (the Village Center/Town Drive roundabout had three lanes, but it was more of a T-approach with a driveway at the top) -- although, now that I think of it, I'm not sure any full 3x3 roundabouts were ever built beyond those two? Every other three-lane roundabout has a part with only two lanes.

Caltrans reclassified the Los Alamitos Circle in Long Beach from a traffic circle to a modern roundabout in 1993.  But they basically just converted it from stop control to yield control and the basic design still mimics that of a "traffic circle".  I personally wouldn't consider it a modern roundabout, but the Los Alamitos Circle does have triple entry lanes at all 4 approaches.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 17, 2017, 05:04:50 PM
The Village Center Circle roundabout is credited as being the first modern roundabout built in America.

Huh, so they were. I always thought the first two were the roundabouts at Hualapai Way and Canyon Run Drive, along Town Center Drive (both full 3x3 roundabouts). However, those didn't fully open until the late 90s! I was way off; the first two along Village Center Circle opened up in 1990. Neither of the Town Center Drive roundabouts must have been very safe, since they replaced the far right lane of each with slip lanes in the early 2000s. They were definitely the first full 3x3 roundabouts in this country, though (the Village Center/Town Drive roundabout had three lanes, but it was more of a T-approach with a driveway at the top) -- although, now that I think of it, I'm not sure any full 3x3 roundabouts were ever built beyond those two? Every other three-lane roundabout has a part with only two lanes.

Caltrans reclassified the Los Alamitos Circle in Long Beach from a traffic circle to a modern roundabout in 1993.  But they basically just converted it from stop control to yield control and the basic design still mimics that of a "traffic circle".  I personally wouldn't consider it a modern roundabout, but the Los Alamitos Circle does have triple entry lanes at all 4 approaches.

That's true. Though as far as I can tell from Historic Aerials, from when the 3x3 Summerlin roundabouts opened to around 2003, they also lacked markings. So in a way, the Los Alamitos Circle was indeed the first 3x3 modern roundabout, relative to the standards of the era.

I'm 99% sure the first "three lane" roundabout in the US (that also had markings, which the Long Beach, Summerlin, and I-70 Vail/Avon roundabouts lacked) was the 18 1/2 & Van Dyke roundabout in Sterling Heights. Unless you know of an earlier one.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 17, 2017, 05:18:59 PM
I'm 99% sure the first "three lane" roundabout in the US (that also had markings, which the Long Beach, Summerlin, and I-70 Vail/Avon roundabouts lacked) was the 18 1/2 & Van Dyke roundabout in Sterling Heights. Unless you know of an earlier one.

I believe the first triple lane modern roundabout with lane markings was the I-95 and Ritchie Marlboro Road roundabouts in Maryland (opened in 2003). 

https://www.google.com/maps/@38.8687399,-76.8449236,575m/data=!3m1!1e3

EDIT:  Nevermind, scratch that.  They were originally 2-lane roundabouts with the third lane going in around 2010.  I think you are right, the Van Dyke roundabout was the first.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 17, 2017, 05:56:57 PM
I'm 99% sure the first "three lane" roundabout in the US (that also had markings, which the Long Beach, Summerlin, and I-70 Vail/Avon roundabouts lacked) was the 18 1/2 & Van Dyke roundabout in Sterling Heights. Unless you know of an earlier one.

I believe the first triple lane modern roundabout with lane markings was the I-95 and Ritchie Marlboro Road roundabouts in Maryland (opened in 2003). 

https://www.google.com/maps/@38.8687399,-76.8449236,575m/data=!3m1!1e3

EDIT:  Nevermind, scratch that.  They were originally 2-lane roundabouts with the third lane going in around 2010.  I think you are right, the Van Dyke roundabout was the first.

Regardless, that's pretty interesting that a roundabout was widened from two lanes to three. I've heard of roundabouts going from one lane to two, but not two to three.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 22, 2017, 07:18:03 PM
And, as this is supposedly the 'first' modern roundabout, if there have been no other fatal accidents here, speaks to how well the roundabout has worked over the years.  Even the most safest roads will have a rare fatal on occasion; mostly due to other circumstances, which in this case was a drunk driver transporting an unbuckled passenger.

The Summerlin roundabout really hasn't performed well.  It is estimated there are 311,000 traffic signals in America.  If signals averaged a fatal crash every 27 years, there would be 11,518 traffic signal fatalities each year.  According to the FHWA, there were 2,924 fatalities at intersections controlled by traffic signals in 2007.  I'll take 2,924 fatalities over 11,518 fatalities any day.  Good thing traffic signals average fewer fatal crashes than the inaugural modern roundabout in Summerlin does.

https://safety.fhwa.dot.gov/intersection/other_topics/fhwasa10005/brief_2.cfm
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on November 22, 2017, 07:26:58 PM
And, as this is supposedly the 'first' modern roundabout, if there have been no other fatal accidents here, speaks to how well the roundabout has worked over the years.  Even the most safest roads will have a rare fatal on occasion; mostly due to other circumstances, which in this case was a drunk driver transporting an unbuckled passenger.

The Summerlin roundabout really hasn't performed well.  It is estimated there are 311,000 traffic signals in America.  If signals averaged a fatal crash every 27 years, there would be 11,518 traffic signal fatalities each year.  According to the FHWA, there were 2,924 fatalities at intersections controlled by traffic signals in 2007.  I'll take 2,924 fatalities over 11,518 fatalities any day.  Good thing traffic signals average fewer fatal crashes than the inaugural modern roundabout in Summerlin does.

https://safety.fhwa.dot.gov/intersection/other_topics/fhwasa10005/brief_2.cfm


Nothing you rambled has anything to do with that specific roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 22, 2017, 07:55:24 PM
The Summerlin roundabout really hasn't performed well.

Based on what evidence? I suspect it probably has performed pretty well, because half the roundabout is single lane.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 22, 2017, 08:05:54 PM
Nothing you rambled has anything to do with that specific roundabout.

Do you realize that traffic signals in America average one fatality every 100 years?  The Summerlin roundabout, which is one of the first modern roundabouts in the nation, had a fatal crash after just 27 years.  In 73 years time, how many more people will slam into the palm trees of that Summerlin roundabout? 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 22, 2017, 08:39:13 PM
Nothing you rambled has anything to do with that specific roundabout.

Do you realize that traffic signals in America average one fatality every 100 years?  The Summerlin roundabout, which is one of the first modern roundabouts in the nation, had a fatal crash after just 27 years.  In 73 years time, how many more people will slam into the palm trees of that Summerlin roundabout?

I'm sure there are many signals with fatality rates greater than once-every-73-years. Should a roundabout's standard be that of the worst-performing traffic light? Probably not. But, me and J&N would like to see some numbers before a conclusion is reached here.

If you can't find any, just say it. I'd look it up, but if you can't find any numbers, I doubt I'd be able to.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 22, 2017, 09:25:38 PM
I'm sure there are many signals with fatality rates greater than once-every-73-years. Should a roundabout's standard be that of the worst-performing traffic light? Probably not. But, me and J&N would like to see some numbers before a conclusion is reached here.

Let’s look at a localized example.  I keep going back to SE Michigan because SEMCOG has compiled a tremendous amount of publicly available crash data that anyone can analyze.  Over the past decade, there have been 3 fatal crashes at the top 20 most crash prone intersections.  Analyzing 20 intersections over a 10 year period is equivalent to 200 years of crash data.  Extrapolating the numbers, the SE Michigan intersections have averaged a fatal crash every 66.6 years (200 years of data / 3 fatal crashes).  These are some of the heaviest traveled intersections in the region and they only average a fatal crash every 66.6 years. 

(https://i.imgur.com/ZV48A5x.png)
http://semcog.org/High-Frequency-Crash-Locations
Title: Re: Crash prone 'modern roundabouts'
Post by: Occidental Tourist on November 22, 2017, 11:07:23 PM
Caltrans reclassified the Los Alamitos Circle in Long Beach from a traffic circle to a modern roundabout in 1993.  But they basically just converted it from stop control to yield control and the basic design still mimics that of a "traffic circle".  I personally wouldn't consider it a modern roundabout, but the Los Alamitos Circle does have triple entry lanes at all 4 approaches.
How is the Los Alamitos Circle in its current configuration not the same configuration as a roundabout?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 22, 2017, 11:29:40 PM
Caltrans reclassified the Los Alamitos Circle in Long Beach from a traffic circle to a modern roundabout in 1993.  But they basically just converted it from stop control to yield control and the basic design still mimics that of a "traffic circle".  I personally wouldn't consider it a modern roundabout, but the Los Alamitos Circle does have triple entry lanes at all 4 approaches.

How is the Los Alamitos Circle in its current configuration not the same configuration as a roundabout?

If you want to be strict, technically it's too big to be classified as a modern roundabout (a stupid requirement in my opinion), but more importantly, it lacks guidance lines. Many of the east coast "traffic circles" have been converted to yield control for all entries, but they still lack guidance lines so they are still often referred to as traffic circles or rotaries.

That said, due to the sheer number of lanes that flow through the Los Alamitos Circle, I think it works better without guidance lines. Apparently the British who helped design it agree, since they're the reason there isn't any today.
Title: Re: Crash prone 'modern roundabouts'
Post by: Occidental Tourist on November 23, 2017, 12:51:16 AM
Caltrans reclassified the Los Alamitos Circle in Long Beach from a traffic circle to a modern roundabout in 1993.  But they basically just converted it from stop control to yield control and the basic design still mimics that of a "traffic circle".  I personally wouldn't consider it a modern roundabout, but the Los Alamitos Circle does have triple entry lanes at all 4 approaches.
How is the Los Alamitos Circle in its current configuration not the same configuration as a roundabout?

If you want to be strict, technically it's too big to be classified as a modern roundabout (a stupid requirement in my opinion), but more importantly, it lacks guidance lines. Many of the east coast "traffic circles" have been converted to yield control for all entries, but they still lack guidance lines so they are still often referred to as traffic circles or rotaries.

That said, due to the sheer number of lanes that flow through the Los Alamitos Circle, I think it works better without guidance lines. Apparently the British who helped design it agree, since they're the reason there isn't any today.
Ah ha.  Thanks.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 23, 2017, 04:24:36 AM
Nothing you rambled has anything to do with that specific roundabout.

Do you realize that traffic signals in America average one fatality every 100 years?  The Summerlin roundabout, which is one of the first modern roundabouts in the nation, had a fatal crash after just 27 years.  In 73 years time, how many more people will slam into the palm trees of that Summerlin roundabout?
You're disappointing here.
First, not all intersections are equal. Normalizing per MEV as commonly done  is a semi-descent metric.
Second, you need statistics in order to draw numeric conclusions. If you consider the day fatal accident happened - then just think about other 36500 days within 100 years?? 
You need at least 10 events to talk reasonable statistic trends - and, thanks god, there are really few places which have that many fatal events over reasonable timeframe. That is why we either talk about less severe more common events, or consider larger ensembles of similar objects for statistical purposes.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 23, 2017, 12:44:24 PM
First, not all intersections are equal. Normalizing per MEV as commonly done  is a semi-descent metric.

I was trying to give the roundabout every chance to succeed.  The Summerlin roundabout, a town center roundabout with an AADT of maybe 20k, was compared to the highest crash location in a region of 4.3 million people. Each individual intersection analyzed in SE Michigan had AADTs ranging from 40k to close to 100k.  The SE Michigan intersections - which carry significantly more traffic than the Summerlin roundabout - averaged a fatal crash every 66.6 years.  The Summerlin roundabout had a fatal crash after 27 years.  One of the nation’s inaugural modern roundabout in Summerlin has averaged a fatal crash faster than even the worst performing intersections in SE Michigan. 

J&N cited the fact that the Summerlin roundabout had one fatal crash in 27 years as proof that the roundabout is performing well.  If fatalities is the metric used to determine if a roundabout is performing well, I would disagree with them (unless if a fatality at over twice the rate of the worst performing intersections is seen as a good thing). 

And, as this is supposedly the 'first' modern roundabout, if there have been no other fatal accidents here, speaks to how well the roundabout has worked over the years.
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on November 24, 2017, 11:29:46 AM



I was trying to give the roundabout every chance to succeed.

I doubt that very much.

SM-T230NU

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 24, 2017, 05:59:33 PM
Many close calls for this driver at roundabouts in 2017.  Supposedly this is just part 1 and focuses on "failure to yield".

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 25, 2017, 12:37:58 AM
Many close calls for this driver at roundabouts in 2017.  Supposedly this is just part 1 and focuses on "failure to yield".

https://www.youtube.com/watch?v=zShxhYSA7Dc

Interesting. When I search "roundabout fails" on Youtube, this video is the sixth result. I wonder what you could have searched...
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on November 25, 2017, 06:08:01 AM
Many close calls for this driver at roundabouts in 2017.  Supposedly this is just part 1 and focuses on "failure to yield".

Wow, those were some horrible crashes.  Blood everywhere.

SM-T230NU

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 25, 2017, 12:55:14 PM
^That video is a compilation of just one driver's roundabout adventures in 2017 in Kitchener, Ontario.  Multiply that dash cam video by all the other daily drivers that use the town's roundabouts and it's not surprising so many crashes are happening.  Blood is being shed at Kitchener's roundabouts, but authorities are just not counting those crashes.

Roundabout death? Motorcycle speeding, lost control on wet road, before Kitchener crash
https://www.southwesternontario.ca/news-story/6225063-roundabout-death-motorcycle-speeding-lost-control-on-wet-road-before-kitchener-crash/

The motorcyclist crashed into a Kitchener roundabout, their bike ending up in the central island, and it's not considered a roundabout fatality.  Easy to say that roundabouts are safe when fatalities aren't counted. 
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on November 25, 2017, 03:29:39 PM
By that logic you should be arguing to close every Freeway and Interstate in the country.  I hear far more about fatalities on the local Interstate highways on a regular basis - roundabout fatalities are quite rare by comparison.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 25, 2017, 05:39:37 PM
By that logic you should be arguing to close every Freeway and Interstate in the country.  I hear far more about fatalities on the local Interstate highways on a regular basis - roundabout fatalities are quite rare by comparison.

The interstate system is the safest road system in the country with 0.8 fatalities per 100 million vehicle miles traveled.  By comparison all road types had a fatality rate of 1.46 in 2004 (source: FHWA).  Much of the safety improvements in Carmel over the past decade can be attributed to the fact that two dangerous surface streets were converted to grade-separated freeways.  The interchange roundabouts built along Keystone Parkway and Meridian Street were simply a byproduct of the freeway expansion.  The remaining non-interchange roundabouts in Carmel seemingly haven’t reduced fatalities.  In August 2014, a driver was killed after losing control at the Pennsylvania St. and 106th roundabout.  In September 2014 a motorcyclist was killed after colliding with the curbing along the 126th and Hazel Dell Parkway roundabout.  And there have been 3 fatalities in a decade at the 96th and Westfield roundabout.

There have been 5 documented fatalities at Carmel roundabouts.  Contrary to popular belief plenty of signalized intersections still exist in Carmel (and there were lots more traffic signals than roundabouts in the city just a decade ago).  So CJW how many fatal crashes have there been at Carmel traffic signal over the past say 20 years?  You got to catch up to at at least 5.... and even then roundabouts supposedly reduce fatal crashes by 90%... so you should easily be able to find more than 5 fatal crashes.

EDIT:  It’s a serious challenge for you CJW.  A good place to start would be the City of Carmel Police Department Annual Reports.  I’ve cross referenced the fatal crashes listed in those reports over the past decade and they correspond to the fatal roundabout crashes I already cited (or they were non-intersection fatalities).  I’m personally having trouble finding the latest signalized intersection fatality in Carmel but maybe you will have better luck.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 25, 2017, 08:37:19 PM
^^
Crash rates are relative; shouldn't you already have data on Carmel's signalised junctions? If there were five fatalities in the last twenty years at Carmel roundabouts, but sixty fatalities in the last twenty years at signalised junctions (whether they exist now or were converted), that would mean the roundabouts have proven safer (as long as fatalities are the main measure).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 26, 2017, 12:21:21 AM
^^
Crash rates are relative; shouldn't you already have data on Carmel's signalised junctions? If there were five fatalities in the last twenty years at Carmel roundabouts, but sixty fatalities in the last twenty years at signalised junctions (whether they exist now or were converted), that would mean the roundabouts have proven safer (as long as fatalities are the main measure).

I found one fatal crash that happened at a signalized junction in Carmel over the past decade.  On February 4th 2007, Charles Ricky watched the first half of the Super Bowl at the Moon Dog Tavern before leaving for his girlfriend’s house.  On the way there he was involved in a single vehicle accident and rolled his truck near the signalized intersection of 116th and Hazel Dell Parkway.  When his abandoned truck was discovered, Charles was nowhere to be found.  Ricky's family and friends searched for him for over a month before his body was discovered at the Martin Marietta aggregates pit along 96th Street in Carmel.  Investigators believe Charles tried to walk back to the tavern after wrecking his truck and either got lost or was taking a shortcut through the quarry and fell down a perilous drop in the darkness.  Police determined Charles died of exposure. 

Charles Ricky’s fatal crash proves that every signalized intersection in Carmel should be converted to roundabouts.

http://www.theindychannel.com/news/missing-man-s-body-found-in-carmel-gravel-pit
https://www.wthr.com/article/missing-lawrence-man-found-in-carmel-quarry
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 26, 2017, 02:17:00 AM
Charles Ricky’s fatal crash proves that every signalized intersection in Carmel should be converted to roundabouts.

Well yeah, obviously.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on November 26, 2017, 08:06:53 AM
^^
Crash rates are relative; shouldn't you already have data on Carmel's signalised junctions? If there were five fatalities in the last twenty years at Carmel roundabouts, but sixty fatalities in the last twenty years at signalised junctions (whether they exist now or were converted), that would mean the roundabouts have proven safer (as long as fatalities are the main measure).

I found one fatal crash that happened at a signalized junction in Carmel over the past decade.  On February 4th 2007, Charles Ricky watched the first half of the Super Bowl at the Moon Dog Tavern before leaving for his girlfriend’s house.  On the way there he was involved in a single vehicle accident and rolled his truck near the signalized intersection of 116th and Hazel Dell Parkway.  When his abandoned truck was discovered, Charles was nowhere to be found.  Ricky's family and friends searched for him for over a month before his body was discovered at the Martin Marietta aggregates pit along 96th Street in Carmel.  Investigators believe Charles tried to walk back to the tavern after wrecking his truck and either got lost or was taking a shortcut through the quarry and fell down a perilous drop in the darkness.  Police determined Charles died of exposure. 

Charles Ricky’s fatal crash proves that every signalized intersection in Carmel should be converted to roundabouts.

http://www.theindychannel.com/news/missing-man-s-body-found-in-carmel-gravel-pit
https://www.wthr.com/article/missing-lawrence-man-found-in-carmel-quarry

Speaking to the choir, dude.
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on November 26, 2017, 05:59:37 PM
^That video is a compilation of just one driver's roundabout adventures in 2017 in Kitchener, Ontario.  Multiply that dash cam video by all the other daily drivers that use the town's roundabouts and it's not surprising so many crashes are happening.  Blood is being shed at Kitchener's roundabouts, but authorities are just not counting those crashes.

Roundabout death? Motorcycle speeding, lost control on wet road, before Kitchener crash
https://www.southwesternontario.ca/news-story/6225063-roundabout-death-motorcycle-speeding-lost-control-on-wet-road-before-kitchener-crash/

The motorcyclist crashed into a Kitchener roundabout, their bike ending up in the central island, and it's not considered a roundabout fatality.  Easy to say that roundabouts are safe when fatalities aren't counted.
So a motorcycle crash linked to speeding on a wet roadway 'should' be blamed on the roundabout? If this type of accident had happened at any other locale you never would've heard about it because you only search for "accident" and "roundabout" in Google news.

SM-T230NU

Title: Re: Crash prone 'modern roundabouts'
Post by: D-Dey65 on November 26, 2017, 10:35:41 PM
Didn't the frequent accidents at the Hawthorne Circle make most highway engineers realize that traffic circles/roundabouts are a hazard, which in fact forced the former parkway commissions in Westchester County to replace it with a partial stack interchange? And now they have an exact reversal of this thinking.

This "new urbanism" shit just keeps pissing me off more and more.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 27, 2017, 03:24:15 AM
traffic circles/roundabouts

Traffic circles ≠ roundabouts. Largely similar, yes, but remarkably different in the ways that count.

Clearly, these roundabouts aren't as perfect as we all thought. However, I think most civil engineers (and even tradephoric) would agree that they are miles better than any of the old traffic circles seen in New England (minus those that have been converted, such as Latham Circle).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 27, 2017, 10:09:46 AM
^That video is a compilation of just one driver's roundabout adventures in 2017 in Kitchener, Ontario.  Multiply that dash cam video by all the other daily drivers that use the town's roundabouts and it's not surprising so many crashes are happening.  Blood is being shed at Kitchener's roundabouts, but authorities are just not counting those crashes.

Roundabout death? Motorcycle speeding, lost control on wet road, before Kitchener crash
https://www.southwesternontario.ca/news-story/6225063-roundabout-death-motorcycle-speeding-lost-control-on-wet-road-before-kitchener-crash/

The motorcyclist crashed into a Kitchener roundabout, their bike ending up in the central island, and it's not considered a roundabout fatality.  Easy to say that roundabouts are safe when fatalities aren't counted.
So a motorcycle crash linked to speeding on a wet roadway 'should' be blamed on the roundabout? If this type of accident had happened at any other locale you never would've heard about it because you only search for "accident" and "roundabout" in Google news.

SM-T230NU

According to the latest region of Waterloo collision report, the roundabout at Homer Watson and Block Line Road was the most crash-prone intersection in the region with 435 crashes over the past 5 years.  These are just the crashes that have been classified as roundabout crashes by local authorities (notwithstanding motorcyclists crashing into roundabouts).  Here are the intersection rankings:

(https://i.imgur.com/0bySVMx.png)
http://www.regionofwaterloo.ca/en/gettingAround/resources/2016_Annual_Collision_Report.pdf

The Block Line roundabout averaged 10.2 FI (Fatal/Injury) crashes per year and has the highest annual cost to society due to collisions in the region.  The roundabout opened in 2011 and is right next to St. Mary’s High School.  The roundabout gets a tremendous amount of pedestrian traffic and within months of opening two pedestrians had been struck in the crosswalk (including a Grade 11 St. Mary’s student hit by a transit bus).  This led to student protests at the roundabout and ultimately a crossing guard was put in place to assist the high school students crossing (they must feel like they are back in elementary school!).  Here’s an interesting roundtable discussion about the Block Line Road roundabout and a video demonstrating just how much pedestrian traffic it gets:


The proposed roundabout near St. Benedict referenced several times in the roundtable discussion was never built.  Several roundabouts were constructed along Franklin Blvd but none right next to the school.  The poor performance of the Block Line roundabout most likely led leaders to scrap those plans.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 27, 2017, 12:03:34 PM
traffic circles/roundabouts

Traffic circles ≠ roundabouts. Largely similar, yes, but remarkably different in the ways that count.

Clearly, these roundabouts aren't as perfect as we all thought. However, I think most civil engineers (and even tradephoric) would agree that they are miles better than any of the old traffic circles seen in New England (minus those that have been converted, such as Latham Circle).
With all that talk from our european friends about removal of lane markings - do you think we're about to return to basics?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 27, 2017, 01:51:39 PM
The second most crash prone intersection in the region of Waterloo was the signalized intersection at Ottawa Street and Homer Watson.  It had 178 crashes over the past 5 years.  Well the city just finished converting the signalized intersection to a triple lane roundabout similar to the roundabout at Block Line Road.  The result has been 34 crashes in 29 days including 4 injury crashes.   A cyclist was struck by a minivan while she was cycling through the roundabout and is interviewed in the report below:

Ottawa/Homer Watson roundabout sees 34 collisions in 29 days
http://kitchener.ctvnews.ca/ottawa-homer-watson-roundabout-sees-34-collisions-in-29-days-1.3671232

At the current crash rate the new triple lane roundabout will see 2138 crashes over the next 5 years, including 251 injury crashes.  Wow, what an improvement!  OK, so what’s a more reasonable crash estimate?  Considering the Ottawa Street roundabout carries nearly 20k more vehicles per day than the Block Line Road roundabout, it could easily top 500 crashes over the next 5 years (Block Line Road had 435 crashes in 5 years).  Any city official who believes the Ottawa Street roundabout will reduce total crashes is delusional (and reading articles from just a few years back when the Ottawa Street roundabout was being proposed, that was their claim).  I had my doubts they would even go ahead with the Ottawa Street roundabout after all the problems the Block Line Road roundabout experienced, but they forged ahead with it. 

It's somewhat surprising they are going ahead with building a massive 3x2 roundabout at Ottawa Street & Homer Watson Blvd after all the issues with the Homer Watson Blvd & Block Road roundabout.  Based on your link, Ottawa Street & Homer Watson Blvd is the most crash prone intersection in the entire region.  Time will tell if the crash problem gets better or worse after the roundabout is completed. 

(http://i1309.photobucket.com/albums/s636/mithokey/db7262ee47b7a5bc63900ea74112-500x329_zpsapmftepa.jpeg)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 27, 2017, 02:09:32 PM
(https://pbs.twimg.com/media/DNHF2ClWAAIzuzz.jpg:large)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 28, 2017, 08:06:08 AM
The proposed roundabout near St. Benedict referenced several times in the roundtable discussion was never built.  Several roundabouts were constructed along Franklin Blvd but none right next to the school.  The poor performance of the Block Line roundabout most likely led leaders to scrap those plans.

Coincidentally a transport truck flipped over and lost his load at the Franklin Boulevard and Clyde Road roundabout about 3 hours after i wrote that post.  It had traffic tied up for hours, partially closing the roundabout.  While crews were cleaning up the mess a 2-vehicle crash on the Savage side of the roundabout left 2 people in hospital with minor injuries.  Not only are Waterloo Police dealing with a reported crash a day at the new Ottawa Street roundabout, they got to deal with trucks tipping over along Franklin Blvd.  Another entertaining day in the region of Waterloo thanks to their "safe" roundabouts.

Truck flips on side in roundabout, loses load
http://kitchener.ctvnews.ca/truck-flips-on-side-in-roundabout-loses-load-1.3696192
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 01, 2017, 08:02:07 AM
Many close calls for this driver at roundabouts in 2017.  Supposedly this is just part 1 and focuses on "failure to yield".

Wow, those were some horrible crashes.  Blood everywhere.

SM-T230NU



You can joke about seeing blood everywhere but Cassi Lam isn't laughing.  She was the 16 year old St. Mary's high school student who was hit by a municipal bus shortly after the Homer Watson and Block Line Road roundabout opened.  Cassi's injury accident isn't an isolated incident.  Over the past 5 years the Homer Watson and Block Line roundabout was deemed to have the highest cost to society due to collisions based on the region's own published report.  The roundabout has averaged 10.2 injury crashes a year which is about the same number of injury crashes as the most dangerous signal in the region (even as the roundabout carries 16k fewer vehicles per day).  And the roundabout had a whopping 257 more total crashes.  If you look closely there was blood on the streets in that video of a driver navigating through the Waterloo roundabouts...  you just got to get your eyes checked.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 01, 2017, 09:51:35 AM
Caltrans reclassified the Los Alamitos Circle in Long Beach from a traffic circle to a modern roundabout in 1993.  But they basically just converted it from stop control to yield control and the basic design still mimics that of a "traffic circle".  I personally wouldn't consider it a modern roundabout, but the Los Alamitos Circle does have triple entry lanes at all 4 approaches.

How is the Los Alamitos Circle in its current configuration not the same configuration as a roundabout?

If you want to be strict, technically it's too big to be classified as a modern roundabout (a stupid requirement in my opinion), but more importantly, it lacks guidance lines. Many of the east coast "traffic circles" have been converted to yield control for all entries, but they still lack guidance lines so they are still often referred to as traffic circles or rotaries.

That said, due to the sheer number of lanes that flow through the Los Alamitos Circle, I think it works better without guidance lines. Apparently the British who helped design it agree, since they're the reason there isn't any today.

Here is a TRB discussion about the Los Alamitos Circle conversion from the man behind it. Talks to convert the circle to a "modern roundabout" began in 1985 when Leif Ourston pitched the idea to John Burnside who was working for Caltran at the time.  According to John congestion virtually disappeared after the conversion but accidents remained a problem.  John also mentions that there are no striped lanes in the circular roadway to conform to British practices of the day. 

Quote
Subject: Re: Los Alamitos Traffic Circle, Long Beach, California

I am very pleased to weigh in on this discussion as I was the Caltrans employee charged with the operation of the Los Alamitos Traffic Circle when Leif Ourston walked up to my desk in December 1985 and offered to help me and Caltrans fix it.  (Hence the line in my signature below, "Designing roundabouts since 1985.")  Since I was having no success solving the large number of accidents at each of the four entries, I said, "Show us how!"  This was the beginning of my love affair with roundabouts.

I will now set out to answer, as best I can, the statements and questions of others, and Wikipedia. Caltrans, being a huge government organization, was not about to go along with this totally unknown "roundabout" nonsense without a whole lot of scrutiny.  That's why it took 7.5 years until "30 June 1993," as Andrew O'Brien correctly stated, to get it converted.  It was initially thought that this site was too big and busy for California's first roundabout, so we looked for a smaller site to start with.  In Ojai (also mentioned by Andrew) we found a three-legged signalized "Y" intersection of two state highways that had congestion and sufficient right of way because it was previously a triangle with three "Y" intersections.  Lief worked up the design (the outline of which is still the logo of Ourston Roundabout Engineering, q.v. at http://www.ourston.com/).  Leif and Caltrans senior engineer Al Maas (an early "believer") began meeting with the locals.  The public, Planning Commission, and City Council loved it for a few months . . . until a local high school teacher charged that Caltrans was "experimenting with the lives of our children!"  The tide quickly turned against us, and Al Maas saw the handwriting on the wall and pulled the project before the locals could shoot it down.  So Andrew, Ojai was before Los Alamitos, but it was never built.

So then we timidly turned our attention back to Los Alamitos (Al Maas and I were gung ho, but the rest of Caltrans was scared to death).  Leif slowly educated us, bringing over first Frank Blackmore and then Andrew O'Brien to try to persuade us.  The plans called for making all entering traffic yield to circulating traffic, including two entries that operated in the reverse.  To augment capacity, entries were flared to as many as four lanes by cutting into the splitter islands.  I probably should have mentioned that this is a huge circle, with a 55-foot circulating roadway around a 360-foot diameter central island (chop down the eucalyptus trees and you'd have room for an international soccer game--my other British passion).  The revisions were completed and traffic began full use of the new roundabout midday on 30 June 1993 with Leif and I there to witness the first PM and AM peaks--we stayed overnight at the motel on the circle.  Congestion virtually disappeared but the accidents went down by only about one-third, as I recall.  So there is to this day an accident problem, contrary to Wikipedia.  The problem is the speed.  Caltrans had only a quarter million dollars for this project--if we had a million dollars we could have done as New York state did by constructing a completely new smaller roundabout inside the existing one, thus controlling the speed.  Today, as I understand it, Ourston Roundabout Engineering is under contract with Caltrans to design spiral striping to increase the safety.

What else?  Wikipedia says, in part, "Also added were wider lanes, redundant traffic signs, and devoted lanes for traffic traveling only 90 of the 360 degrees of the circle."  There are NO striped lanes in the circular roadway (a change order from the plans to match British practice at the time), except for the two "devoted" free-rights, which were not new but were there before the modifications. I am personally indebted to Leif Ourston for much of what I know.  His pioneering spirit allowed him to design the first two modern roundabouts in the USA in Summerlin, NW of Las Vegas, and these are three-laners!

John Burnside, P.E.
Consulting Traffic Engineer
Designing roundabouts since 1985
INs and OUTs of ROUNDABOUTS
10628 Melody Road
Big Oak Valley, CA  95977-9537
530-432-6526
530-575-5007 cell
530-432-6511 fax
_________________________________________________________
From:    "tonyrvt@aceweb.com" <tonyrvt@ACEWEB.COM>
Subject: Re: Los Alamitos Traffic Circle, Long Beach, California--Really?

Crash rates at roundabouts are rather meaningless--injury rates are critical.  The Long Beach roundabout data was published about a decade ago showing a sharp reduction injuries and erasing daily circle lockup at peak hours.  At the time about 15 years ago--Leif Ourston can provide the details--Ourston published the before and after injury data.  The Brattleboro (VT) Keene Turn Roundabout crash rate is up during the first five years of roundabout operation over signals with protected left turns--but the injuries before were 55 (11 per year) including a fatality and 1 injury after--a 95% decline,  Reason for the crash rate increase?   Two design flaws which the State DOT has declined to address in spite of the fact that the bulk of the crashes involve commercial vehicles (tractor trailers).

A final note--because the Long Beach roundabout was one of the first in the US. Catrans decided against reducing the size of the circle, just roundaboutizing it otherwise. This was unlike the first NYSDOT which reduced the circle to a reasonable size in their first roundabout, a two-laner in Kingston, NY.

The question becomes would there be more or fewer crashes if circulating lane markings were added or if the central island diameter was downsized?  Both questions are debatable.  It seems like no matter what is done to these complex circles, they are prone to lots of crashes (big vs. small; lane lines vs. no lane lines... it doesn't seem to matter).

Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 01, 2017, 01:52:50 PM
The question becomes would there be more or fewer crashes if circulating lane markings were added or if the central island diameter was downsized?  Both questions are debatable.  It seems like no matter what is done to these complex circles, they are prone to lots of crashes (big vs. small; lane lines vs. no lane lines... it doesn't seem to matter).


In my mind, that's because there's more room to work with.  If a person crosses a lane line or makes a sudden move, it's more likely to not be right at a conflict point.  To put it another way, it functions more like a series of four Y-intersections than as a single intersections.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 01, 2017, 02:35:53 PM
I'm cross-posting this at the suggestion of a member in another thread.


Accident-prone crossroads and roundabout on the A140 at Hempnall to be replaced - with more than £3m of funding
(https://www.dissexpress.co.uk/news/accident-prone-crossroads-and-roundabout-on-the-a140-at-hempnall-to-be-replaced-with-more-than-3m-of-funding-1-8206708)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 01, 2017, 04:35:53 PM
Here is a TRB discussion about the Los Alamitos Circle conversion from the man behind it. Talks to convert the circle to a "modern roundabout" began in 1985 when Leif Ourston pitched the idea to John Burnside who was working for Caltran at the time.  According to John congestion virtually disappeared after the conversion but accidents remained a problem.  John also mentions that there are no striped lanes in the circular roadway to conform to British practices of the day. 

Quote
Subject: Re: Los Alamitos Traffic Circle, Long Beach, California
[clipped]

Wow, great read! Thanks for posting that. No surprise that the first real roundabout in the US was built in-part because of an engineer's anglophile-ness. I seem to recall one Jim Brainard also being a bit of an anglophile! Nothing wrong with that, of course...the TRL has come with a lot of very cool stuff.

The question becomes would there be more or fewer crashes if circulating lane markings were added or if the central island diameter was downsized?  Both questions are debatable.  It seems like no matter what is done to these complex circles, they are prone to lots of crashes (big vs. small; lane lines vs. no lane lines... it doesn't seem to matter).

I do honestly think that, when geometry gets tough, people tend to "drift". They either approach too quickly and have no time to react, or intentionally approach at-speed, fully intending to drift-about. Regardless if roundabouts are large or small, you need to turn your wheel to continue. I think that particular fact is where roundabouts are having trouble. Why exactly roundabouts suffer from this problem, and not any other bend in the road, I don't know. Drivers genuinely just don't seem to notice them.

Here's something that the British do, that I haven't yet seen in the US: countdown warning lines(?); lines in the road that gradually get closer and closer as you approach the roundabout. They're typically yellow in the UK. Ideally, these would be audible. If you're approaching a roundabout with your eyes focused elsewhere, the sudden grooves would get your attention. It's easy to ignore signs, but I've yet to meet anyone that wasn't alarmed by rumble strips.

(https://i.imgur.com/2hI2GDg.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on December 01, 2017, 04:41:59 PM
Maybe it's just me, but those lines seem a bit excessive, as in there's too many of them for too long (lengthwise).
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 01, 2017, 04:44:14 PM
Here's something that the British do, that I haven't yet seen in the US: countdown warning lines(?); lines in the road that gradually get closer and closer as you approach the roundabout. They're typically yellow in the UK. Ideally, these would be audible. If you're approaching a roundabout with your eyes focused elsewhere, the sudden grooves would get your attention. It's easy to ignore signs, but I've yet to meet anyone that wasn't alarmed by rumble strips.

(https://i.imgur.com/2hI2GDg.png)

I know of roundabouts that have rumble strips in advance, but they're all in rural locations.  Here's an example on US-50 in Kansas. (https://goo.gl/maps/aJCYB4FXWz72)

Not aware of any in urban settings.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 01, 2017, 04:48:10 PM
Maybe it's just me, but those lines seem a bit excessive, as in there's too many of them for too long (lengthwise).

The speed limit along that road is 70, so they actually go by pretty quickly.

I know of roundabouts that have rumble strips in advance, but they're all in rural locations.  Here's an example on US-50 in Kansas. (https://goo.gl/maps/aJCYB4FXWz72)

Not aware of any in urban settings.

Interesting. I wish the rumble strip was placed a little later, though (and a bit more often, rather than just once). Speed limit 55, with only one rumble strip, doesn't seem adequate.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 01, 2017, 05:05:48 PM
I know of roundabouts that have rumble strips in advance, but they're all in rural locations.  Here's an example on US-50 in Kansas. (https://goo.gl/maps/aJCYB4FXWz72)

Not aware of any in urban settings.

Interesting. I wish the rumble strip was placed a little later, though (and a bit more often, rather than just once). Speed limit 55, with only one rumble strip, doesn't seem adequate.

There is more than one set of rumble strips.  Go west two or three mouse clicks, and you'll find another one.  And the speed limit along US-50 is 65 mph, by the way.  55 is just the reduced speed limit approaching town.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 01, 2017, 06:53:35 PM
I know of roundabouts that have rumble strips in advance, but they're all in rural locations.  Here's an example on US-50 in Kansas. (https://goo.gl/maps/aJCYB4FXWz72)

Not aware of any in urban settings.

Interesting. I wish the rumble strip was placed a little later, though (and a bit more often, rather than just once). Speed limit 55, with only one rumble strip, doesn't seem adequate.

There is more than one set of rumble strips.  Go west two or three mouse clicks, and you'll find another one.  And the speed limit along US-50 is 65 mph, by the way.  55 is just the reduced speed limit approaching town.

Oh, I found them. Didn't think there'd be more in that direction. Still would like to see more closer to the actual roundabout.

According to this sign, placed opposite a 65 mph speed limit for southbound traffic (heading away from the roundabout), the limit approaching the roundabout is 55: https://goo.gl/LPGY55
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on December 02, 2017, 04:03:16 AM



You can joke about seeing blood everywhere but Cassi Lam isn't laughing.

What's wrong with you?
I was commenting on the video you posted, nothing else.

SM-T230NU

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 02, 2017, 02:53:41 PM
You can joke about seeing blood everywhere but Cassi Lam isn't laughing.

What's wrong with you?
I was commenting on the video you posted, nothing else.

In a last ditch effort to win over the more easily-influenced of us, tradephoric has turned to the Helen Lovejoy, "think of the children" style of arguing.

All engineers have blood on their hands. Even the safest of intersections have probably had a bad accident at one point, where someone was hurt. You can prevent 99% of collisions, but there will always be that 1% that you just have no control over. I'm not saying Cassie Lam's accident is one of those cases, but you just can't take these things personally.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 02, 2017, 03:23:00 PM
You can joke about seeing blood everywhere but Cassi Lam isn't laughing.

What's wrong with you?
I was commenting on the video you posted, nothing else.

In a last ditch effort to win over the more easily-influenced of us, tradephoric has turned to the Helen Lovejoy, "think of the children" style of arguing.

All engineers have blood on their hands. Even the safest of intersections have probably had a bad accident at one point, where someone was hurt. You can prevent 99% of collisions, but there will always be that 1% that you just have no control over. I'm not saying Cassie Lam's accident is one of those cases, but you just can't take these things personally.

There should always be a balance between taking too much personal responsibility vs. ignoring personal aspect at all. From my perspective, we shifted toward too much of chapter 11 when CEO walking out of the window or eating bullet would be more appropriate due to total clusterfuck on their watch. For example, Katsuaki Watanabe - chairmen of Toyota during "sticky mat" fiasco,  still works for Toyota.

I don't know if I would be able to sleep well if something I designed would result in a fatal accident - but apparently any car/airplane/traffic designer knows that will happen, sooner or later. Then statistics may come to help - if there will be less of those events, it should be sort of OK.
Now, looks like numbers don't add up for some of those circles... And I am not sure how designers should feel in such situation. "I was just doing my job"? Oh, well...
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on December 02, 2017, 03:47:55 PM


Now, looks like numbers don't add up for some of those circles... And I am not sure how designers should feel in such situation. "I was just doing my job"? Oh, well...

It depends. Not all crashes are created equally. There's a lot of distracted driving these days and I'm not convinced that's not playing a role in some of what's being offered here.
I've not read every post in this thread but I've seen some links to stories of drunk drivers or speeders. The OP likely wouldn't blame the design of a four-way traffic controlled intersection if a drunk driver blew through a functioning red light.



HTC6525LVW

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 02, 2017, 03:57:13 PM


Now, looks like numbers don't add up for some of those circles... And I am not sure how designers should feel in such situation. "I was just doing my job"? Oh, well...

It depends. Not all crashes are created equally. There's a lot of distracted driving these days and I'm not convinced that's not playing a role in some of what's being offered here.
I've not read every post in this thread but I've seen some links to stories of drunk drivers or speeders. The OP likely wouldn't blame the design of a four-way traffic controlled intersection if a drunk driver blew through a functioning red light.
And these are probably the worst possible excuses for the engineer to make. But oh, well, Roger Boisjoly is dead - and probably forgotten. And Toyota still sells.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 03, 2017, 02:42:32 AM
I don't know if I would be able to sleep well if something I designed would result in a fatal accident - but apparently any car/airplane/traffic designer knows that will happen, sooner or later. Then statistics may come to help - if there will be less of those events, it should be sort of OK.
Now, looks like numbers don't add up for some of those circles... And I am not sure how designers should feel in such situation. "I was just doing my job"? Oh, well...

There's a huge difference in a design flaw that killed someone, and an accident that just happened to kill someone in an intersection you designed.

Design flaw: Car approaches an intersection with driver who can't see the traffic light. Runs red light. Kills innocent motorist. Bad design.

Not a design flaw: Car approaches intersection with driver high on meth and cocaine. Runs red light.  Kills innocent motorist. Bad driver.

If you can't go to sleep at night over the latter, you would need to find another line of work.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on December 03, 2017, 10:41:16 AM
Nice to see some sanity in the thread.   Meanwhile the city of Carmel continues to open new roundabouts (http://carmellink.com/pdfs/maps/CL2-Overview%20map%20ALL-FINAL.pdf) at a rapid pace, with lots of happy drivers from reduced congestion and no mass carnage. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 03, 2017, 12:09:35 PM
Nice to see some sanity in the thread.   Meanwhile the city of Carmel continues to open new roundabouts (http://carmellink.com/pdfs/maps/CL2-Overview%20map%20ALL-FINAL.pdf) at a rapid pace, with lots of happy drivers from reduced congestion and no mass carnage. 

Carmel drivers are guaranteed to experience some delay when traversing through a roundabout.  That’s not the case with traffic lights.  Last night I literally drove 40 miles without getting stopped at a signal — driving through 122 consecutive green lights.  Zero delay while traveling through 122 green lights.  That could never happen at roundabouts. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 03, 2017, 12:16:41 PM
I don't know if I would be able to sleep well if something I designed would result in a fatal accident - but apparently any car/airplane/traffic designer knows that will happen, sooner or later. Then statistics may come to help - if there will be less of those events, it should be sort of OK.
Now, looks like numbers don't add up for some of those circles... And I am not sure how designers should feel in such situation. "I was just doing my job"? Oh, well...

There's a huge difference in a design flaw that killed someone, and an accident that just happened to kill someone in an intersection you designed.

Design flaw: Car approaches an intersection with driver who can't see the traffic light. Runs red light. Kills innocent motorist. Bad design.

Not a design flaw: Car approaches intersection with driver high on meth and cocaine. Runs red light.  Kills innocent motorist. Bad driver.

If you can't go to sleep at night over the latter, you would need to find another line of work.
Sure, dehumanizing coupled with ignorance in statistics can go a long way..
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on December 03, 2017, 12:18:56 PM
I looked up the Cassie Lam case.

"Child found that Lam stepped into a crosswalk at the last second without signaling her intent to cross and without giving the driver time to stop. The empty bus was not speeding."

SM-T230NU

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 03, 2017, 12:49:34 PM
^^Cassi was just one of two girls to get hit in the crosswalk shortly after the Homer Watson/Block Line roundabout opened… the other being an 11 year old girl who was hit while riding her bike in the crosswalk.  Everybody knows you aren’t supposed to ride your bike across the crosswalk so we can ignore her injury crash too.  Of course if we ignore every crash where someone was found to be at fault, then there wouldn’t be a crash problem at these roundabouts.  Hmmm… I think you just solved the problem!  Just ignore all these crashes. 

Maybe I’m humanizing these crashes because you seem to ignore the cold hard facts.   The fact is the Homer Watson/Block Line roundabout had 435 crashes over a 5 year period - a whopping 257 more crashes than the next closest intersection in the region.  The fact is the Homer Watson/ Block Line roundabout averaged 10.2 injury crashes per year, about the same average injury crashes as the most dangerous signalized intersection in the region (even as the signalized intersection carried much higher traffic volumes than the roundabout).  The fact is the Homer Watson/Block Line roundabout was deemed the most dangerous intersection in the region of Waterloo with an average excess social cost of $271,780.
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on December 03, 2017, 01:03:52 PM
You cannot blame a roundabout for a teen walking right in front of an oncoming bus. You chose to raise this case to further your argument and to take a dig at me. No one forced you to point out the Cassie Lam story.

SM-T230NU

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 03, 2017, 01:15:51 PM
You cannot blame a roundabout for a teen walking right in front of an oncoming bus. You chose to raise this case to further your argument and to take a dig at me. No one forced you to point out the Cassie Lam story.

SM-T230NU
As someone who had to cross a road by roundabout a few times:
you SHOULD blame roundabout for any pedestrian accident. Moreover, roads SHOULD be driven - and  designed - with irresponsible kids in mind.
I remember a video they showed during mandatory pre-license class: what kind of unexpected road hazards driver has to anticipate. Kids, pets, animals running into the road are a big issue - and if you see them roadside, keep an eye on them.
And to add insult to injury - roundabouts don't allow that monitoring, in fact view to the other side is often deliberately blocked, hence they are part of the problem.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on December 03, 2017, 01:40:33 PM
If all roads were designed with irresponsible kids in mind, then they would all be fenced off and have a speed limit of 10. You can't eliminate incidents due to stupidity.

No, the roundabout is not at fault when a kid just steps out in front of a vehicle.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 03, 2017, 01:51:07 PM
If all roads were designed with irresponsible kids in mind, then they would all be fenced off and have a speed limit of 10. You can't eliminate incidents due to stupidity.

No, the roundabout is not at fault when a kid just steps out in front of a vehicle.
If roads were not designed with stupid kids in mind, we would have speed limit of 65 on city streets.
Roundabout may not be the cause of that kid action; but it creates certain traffic - vehicular and pedestrian - patterns, and certain (in)visibility areas. One isolated accident may - or may not - occur with traffic light instead of roundabout; this is all about statistics.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on December 03, 2017, 01:54:10 PM
By your logic stemming from the kid getting by the bus, crosswalks should be done away with as well.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 03, 2017, 01:58:16 PM
One isolated accident may - or may not - occur with traffic light instead of roundabout; this is all about statistics.

That's what we've been saying all along.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 03, 2017, 02:04:02 PM
By your logic stemming from the kid getting by the bus, crosswalks should be done away with as well.
Did you ever use crosswalk by the round about? If you want, I invite you participate in a test on a local one.  PM me for phone number, we can meet and try out the funny one in Albany.  I'll  do my best to ensure you survive that experience, although that is definitely not a given.

Roundabouts and crosswalks just don't match, like party balloons and sewing needles.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 03, 2017, 02:04:54 PM
One isolated accident may - or may not - occur with traffic light instead of roundabout; this is all about statistics.

That's what we've been saying all along.
Yep, and numbers show roundabouts are heavily overrated.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 03, 2017, 02:15:50 PM
You cannot blame a roundabout for a teen walking right in front of an oncoming bus. You chose to raise this case to further your argument and to take a dig at me. No one forced you to point out the Cassie Lam story.

Neither a signalized intersection or roundabout is immune to drunk drivers, distracted drivers or kids running out into the crosswalk.   All i know is we have been told that roundabouts are suppose to reduce injury crashes.  When that doesn't happen i question why.  Cassi Lam's injury happened in 2011 and the 2016 region of Waterloo collision report analyzes crash data from 2012-2016.  Even without her injury analyzed, the Homer Watson/Block Line roundabout was the most dangerous intersection in the region over the past 5 years.  There are literally hundreds of signalized intersections in Kitchener and Cambridge (which makes up the region of Waterloo) yet the title for the most dangerous intersection goes to a roundabout.  What a prestigious award!

In addition to the Kitchener roundabout, a published report out of Minnesota looked at six 2x2 roundabouts and found that INJURY crashes increased by 6.3%.  In addition PDO crashes increased by 212.5%.  That's pretty much in line with what i have been arguing throughout this thread.  For all this time we have been told roundabouts reduce injury crashes, recent studies are starting to dispute that common believe in regards to these complex roundabouts.  It doesn't appear all types of roundabouts reduce injuries (and they sure as hell don't reduce PDO crashes!.. those go through the roof). 
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on December 03, 2017, 02:54:52 PM
Neither a signalized intersection or roundabout is immune to drunk drivers, distracted drivers or kids running out into the crosswalk.

But you don't bang on about those. 
For you, if someone gets hit crossing at a light it's the fault of the driver or the pedestrian or a combination of the two. 
If they get hit crossing at a roundabout then it's the roundabout's fault.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 03, 2017, 03:42:23 PM
Neither a signalized intersection or roundabout is immune to drunk drivers, distracted drivers or kids running out into the crosswalk.

But you don't bang on about those. 
For you, if someone gets hit crossing at a light it's the fault of the driver or the pedestrian or a combination of the two. 
If they get hit crossing at a roundabout then it's the roundabout's fault.
There is a so-called "swiss cheese model" for accidents: https://en.wikipedia.org/wiki/Swiss_cheese_model
Any accident in a properly designed system is a result of multiple failures. That is, of you stack a few slices of swiss cheese - chances are you are not having any through holes. Or the holes may align..

In case of pedestrian-car accident, there are driver who should pay attention, pedestrian who should pay attention, road design which should favor proper behavior of both, police presence to help those folks behave, speed limits which increase time to react and reduce injury, deformable car exterior which absorbs collision energy and reduces injury - and so on.
A fatal accident means too many of these issues came up at the same time. And we must examine role of each and every factor. Kid not paying attention? check. Driver not paying attention? Possibly. Roundabout inflicting lower speed? check. Roundabout preventing driver from seeing pedestrian? check.  Bus not responding properly to collision? possibly - etc.

Saying roundabout (signalized intersection, crosswalk layout) is not relevant to the accident is plain wrong. It may worked as designed - or not worked as designed; but you need to crunch the numbers to be certain. If intersection A does better than intersection B - if other factors are equal - then it is about design.
Since no structures are truly equal, it boils to more statistics and analysis.. Yet that is the overall logic
Title: Re: Crash prone 'modern roundabouts'
Post by: TheHighwayMan394 on December 03, 2017, 08:00:40 PM
What exactly is the continued purpose of this thread? Will posting enough articles about roundabout accidents somehow prevent future ones from being built? What actions are you guys taking other than cruising google for articles that fit your views and saying it proves you right? Do you deliberately avoid any roads that have them in use?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 03, 2017, 09:14:47 PM
What exactly is the continued purpose of this thread? Will posting enough articles about roundabout accidents somehow prevent future ones from being built? What actions are you guys taking other than cruising google for articles that fit your views and saying it proves you right? Do you deliberately avoid any roads that have them in use?
Well, what is the purpose of any internet discussion?  Same here.

Talking for myslef: no, I cannot avoid roundabouts - I cannot get easily from home without driving through one (other options are cutting through corner gas station or 5 miles of back roads to next highway exit, about 10 minutes extra drive). The only entry to work is through roundabout; my wife has to navigate at least 2 - and up to 6 - to get to her. We both believe traffic lights would be a better solution for the area.

Single crashes reports are moot; but there is enough higher level analysis posted here to question unrestricted roundabout ideology.

As for what else can be done.. Maybe not related - but the party which pushed for local flood roundabouts lost some local offices after forcing through a quite controversial batch. Although that didn't make NY battleground state as Trump wanted - county voted red last year. Is that related? Maybe yes, maybe not. But no new roundabout construction is planned..
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 04, 2017, 09:30:53 AM
What exactly is the continued purpose of this thread?
There is continued roundabout research to discuss.  Several articles of trucks tipping over at roundabouts have been posted but also research that looks at potential counter measures to prevent truck tip-overs has been posted.   I’m not suggesting we rip out that Worthington roundabout because two trucks tipped-over during a two week period last month, but maybe there are ways to prevent them.  A presentation was given at the roundabout conference in Green Bay this year that was entitled “Geometric Parameters that Affect Truck Stability” .  In the presentation the RI (Rollover Index) decreased when the ICD increased, the RI was lower in the right lane than the left lane of the roundabout, the RI decreased most significantly when lowering truck speed from 15 mph to 10 mph, the RI was lower with crowned section than with constant outer slope, and a higher rollover risk was associated with 3-inch vertical face truck aprons.  Other counter measures to slow traffic down include the use of optical speed bars and rumble strips along the roundabout approaches.
 
Will posting enough articles about roundabout accidents somehow prevent future ones from being built?
Accidents at roundabouts can have an effect on future plans.  As I mentioned the region of Waterloo scrapped plans to build a major roundabout next to a high school on Franklin Blvd. in Cambridge largely due to Cassi Lam getting hit by a bus in the crosswalk shortly after the Block Line roundabout opened in Kitchener.  Her injury accident made the public question if a roundabout was a good idea at high pedestrian traffic locations.  Fast forward to today and the region just constructed another large roundabout at Ottawa Street and Homer Watson similar to the Block Line roundabout design.  It has much less pedestrian traffic as it is not right next to a high school, but two bicyclists have already been hit in the roundabout within a month of opening.  Much of the reason these roundabouts have been built is because city leaders have stated the roundabouts would be safer.  People in the community have every right to question if that’s the case.

What actions are you guys taking other than cruising google for articles that fit your views and saying it proves you right?
About 20 years ago the IIHS proclaimed that roundabouts are safer than traditional signalized intersections.  Are we just supposed to assume that it is ”˜settled science’ and never cite anything that contradicts this general belief?  It’s one thing to look at roundabouts in general and say they are safer but not all roundabouts are created equal.  I have long argued that complex roundabouts with 2x2 or higher geometries have high crash rates and that reductions in injury crashes at these types of roundabouts are questionable.  The Ellsworth roundabout in Ann Arbor experienced a 10 fold increase in crashes after the roundabout was completed.  But that is just one location and maybe it’s a total fluke.  Then you hear that the 2x2 roundabouts analyzed in the Minnesota study saw a 200% increase in total crashes and a 6.2% increase in INJURY crashes.  There has to reach a point where you question if certain complex roundabouts are safer.  I just find it humorous when a complex roundabout has nearly 200 crashes in a year, and people will just say “yeah but it’s safe because it’s a roundabout” . 

Do you deliberately avoid any roads that have them in use?
The IIHS is such a reputable organization that has shaped public opinion that roundabouts are safer.  Remember, it’s a roundabout so it must be safe!  Well if you believe that, they also researched two roundabouts in Bellingham, Washington and found that drivers 70 years and older were less likely to travel through the roundabouts and would find alternative routes to avoid it. 

Personally I have avoided driving on roundabout corridors if I didn’t feel like slowing down, speeding up, slowing down, and speeding up again.  I mentioned that this weekend I drove for 40 miles without hitting a red light along a major corridor in Detroit, cruising through 122 consecutive green lights.  Why would I want to drive through a bunch of roundabouts when I can just cruise through 122 consecutive green lights?  It's a lot more convenient then having to slow down for every roundabout you come to. 
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on December 04, 2017, 12:34:35 PM
It's unfortunate what happened to Cassi Lam. I went to St. Mary's High School and she was actually in my class, so unlike most accidents, this one felt more personal. I can see why pedestrians are scared to use roundabout crosswalks. Entering vehicles have lots of time to see pedestrians and the tight curve entering the roundabout forces them to slow down. But exiting the roundabout, you have a much shorter distance to notice the pedestrian waiting to cross, and there's less of curve, encouraging faster exit speeds. I don't use the infamous Homer Watson/Block Line roundabout often, but I used it once this summer and I blew by a pedestrian waiting to cross. By the time I saw them, I felt like I was going to fast to stop (thankfully they didn't start crossing!). It's tough though, since I still like roundabouts. They often seem to be more efficient than traffic lights, and I prefer stopping briefly (or slowing down) every time to drive through a roundabout then sometimes getting stuck waiting for minutes at a red light.

I think larger roundabouts with sharp turns at both the entrance and the exits would help slow people down, making it easier to stop for pedestrians. Of course, this would require more land, so I can understand why this may not be practical in a lot of cases. I also wonder if there are other downsides to larger roundabouts (other than increased travel time)?

Changing the topic a bit, I find this roundabout in Arthur, ON to be poorly designed: https://www.google.ca/maps/@43.83622,-80.532375,297m/data=!3m1!1e3 (https://www.google.ca/maps/@43.83622,-80.532375,297m/data=!3m1!1e3) (unfortunately there's no street view).
They made it very small to fit in the available right-of-way, but it's so small that you can go straight through it without turning!
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on December 04, 2017, 09:38:27 PM
Posting this before tradephoric does his google search of the day....

There was a motorcycle crash at one of the Hazel Dell roundabouts in Carmel today.   The motorcycle was fleeing police at high speed after refusing to pull over for a traffic stop.   Somehow I'm sure he will say this was the roundabout's fault as well.    :no:
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 05, 2017, 02:52:15 AM
Changing the topic a bit, I find this roundabout in Arthur, ON to be poorly designed: https://www.google.ca/maps/@43.83622,-80.532375,297m/data=!3m1!1e3 (https://www.google.ca/maps/@43.83622,-80.532375,297m/data=!3m1!1e3) (unfortunately there's no street view).
They made it very small to fit in the available right-of-way, but it's so small that you can go straight through it without turning!

Reminds me of those mini roundabouts in the UK, where going through without turning much is quite common. In other European countries, especially France for whatever reason, the traversable area of the roundabout is so wide, many allow you pass right through without hardly turning your wheel. See here (west to east movement): https://goo.gl/tCyV1H
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 05, 2017, 12:16:20 PM
Posting this before tradephoric does his google search of the day....

There was a motorcycle crash at one of the Hazel Dell roundabouts in Carmel today.   The motorcycle was fleeing police at high speed after refusing to pull over for a traffic stop.   Somehow I'm sure he will say this was the roundabout's fault as well.    :no:

The motorcyclist was critically injured.  Cjw2001, have you been able to find the last time someone was killed at a Carmel traffic signal?  I know Carmel is known as the roundabout capital of America but to this day traffic signals still exist in the city.   There have been 5 documented fatalities at Carmel roundabouts over the past decade but not a single documented fatal crash at a traffic signal (let alone 5 of them).  I figured you would have some idea when the last fatality happened at a traffic signal in Carmel.  An important thing to keep in mind is there were more traffic signals than roundabouts in Carmel a decade ago (in fact not a single roundabout had been built along Meridian Street or Keystone Pkwy back in 2007).

Documented fatalities in Carmel over the past decade....
Roundabouts = 5 fatalities
Traffic signals = 0 fatalities
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 05, 2017, 12:32:57 PM
Posting this before tradephoric does his google search of the day....

There was a motorcycle crash at one of the Hazel Dell roundabouts in Carmel today.   The motorcycle was fleeing police at high speed after refusing to pull over for a traffic stop.   Somehow I'm sure he will say this was the roundabout's fault as well.    :no:

The motorcyclist was critically injured.  Cjw2001, have you been able to find the last time someone was killed at a Carmel traffic signal?  I know Carmel is known as the roundabout capital of America but to this day traffic signals still exist in the city.   There have been 5 documented fatalities at Carmel roundabouts over the past decade but not a single documented fatal crash at a traffic signal (let alone 5 of them).  I figured you would have some idea when the last fatality happened at a traffic signal in Carmel.  An important thing to keep in mind is there were more traffic signals than roundabouts in Carmel a decade ago (in fact not a single roundabout had been built along Meridian Street or Keystone Pkwy back in 2007).

Documented fatalities in Carmel over the past decade....
Roundabouts = 5 fatalities
Traffic signals = 0 fatalities

Easy enough to find: http://www.nixle.us/alert/5777716/

Oh, wait, you specifically said traffic signal intersections to exclude intersections without traffic signals, which appears to be the case of this accident.  Guess we need to narrow our focus a bit to meet your agenda.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 05, 2017, 01:03:40 PM
Oh, wait, you specifically said traffic signal intersections to exclude intersections without traffic signals, which appears to be the case of this accident.  Guess we need to narrow our focus a bit to meet your agenda.
Sure, if roundabouts were positioned where they belong - to intersections with too much traffic for a stop/yield sign flow control, yet with too little for full signal - we should be comparing roundabouts to non-signalized intersections.
Unfortunately, we have roundabouts built where traffic signals have hard time handling traffic - that is, 30k+ daily traffic.
But of course to meet your agenda, you would show how safe low traffic roundabouts are.
Trade seems to be somewhat more honest person in this context. Agenda-driven like everyone is these day,  but still a bit more honest.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 05, 2017, 01:55:57 PM
Easy enough to find: http://www.nixle.us/alert/5777716/

Oh, wait, you specifically said traffic signal intersections to exclude intersections without traffic signals, which appears to be the case of this accident.  Guess we need to narrow our focus a bit to meet your agenda.

They should never have planted trees along there.  It's their job to plan for idiot drivers who run off the side of the road.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 05, 2017, 02:04:48 PM
Easy enough to find: http://www.nixle.us/alert/5777716/

Oh, wait, you specifically said traffic signal intersections to exclude intersections without traffic signals, which appears to be the case of this accident.  Guess we need to narrow our focus a bit to meet your agenda.

They should never have planted trees along there.  It's their job to plan for idiot drivers who run off the side of the road.
Of course it is. Divided highways and guardrails are simple examples of such planning.
Always remember - you're not the only idiot behind the steering wheel (c)my driving instructor
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 05, 2017, 02:44:48 PM
A signalized corridor leads to platooning where a group of vehicles are traveling in packs.  Conversely, a roundabout breaks up platoons and traffic exits the roundabout more sporadically.  Imagine a scenario where a driver is trying to make a left out of an unsignalized sub-street.  Do roundabouts help or hurt their chances of pulling out of their sub safely?  Once a roundabout is complete drivers at nearby sub-streets will often complain that there isn’t enough gap to pull out of the sub.  Imagine a scenario where a roundabout reduces injury crashes by 30% but mid-block injury crashes increases by 50%.  Would the roundabout still be seen as a safety improvement? 

See Walker's new I-12 roundabout in action; residents, police call it 'confusing'
http://www.theadvocate.com/baton_rouge/news/communities/livingston_tangipahoa/article_6d52d828-d611-11e7-9582-8f8dcc4fe95f.html

Watch the video of the new I-12 roundabout along Walker Road.  Admittedly one of the off-ramp lanes is still coned off which is greatly reducing the capacity of the roundabout.  But look how off-ramp traffic is backing up onto the freeway.  Do you think that this will be the only time that the off-ramp will experience lane restrictions?  Maybe in stasis that would be true, but this is the real world.  At least with a traffic signal you can favor the off-ramp traffic and give them more time if there are lane restrictions (so that off-ramp traffic don't back up onto the freeway).  With an unsignalized roundabout you can't do that.  But don't worry the roundabout is safe.. nevermind the family in a mini-van that just got rear-ended by a semi on the freeway. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 05, 2017, 03:44:40 PM
A signalized corridor leads to platooning where a group of vehicles are traveling in packs.  Conversely, a roundabout breaks up platoons and traffic exits the roundabout more sporadically.  Imagine a scenario where a driver is trying to make a left out of an unsignalized sub-street.  Do roundabouts help or hurt their chances of pulling out of their sub safely? 

Depends on the traffic volumes coming from each signal phase of the nearest stoplights both up- and downstream of the intersection.  Stoplights do not simply stop all traffic and then allow all traffic to go.  To turn left out of my bank, for example, I need to wait for [1] nearside through traffic from the left to clear; [2] then nearside right-turning traffic to clear (which had previously been waiting, and which often keeps flowing until the next signal phase); [3] and then protected left-turning traffic to clear.  By the time all of that happens, my gap on the far side of the road has often already been filled by some phase or other of the signal on my right, and all hope is lost.

In this case, a roundabout may or may not help.  I don't know.  But the platooning of vehicles caused by stoplights doesn't necessarily lead to useful gaps for left-turning traffic.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 07, 2017, 10:32:34 AM
WisDOT is considering a roundabout for Rhinelander at highways 8 and 47.
http://www.rivernewsonline.com/main.asp?SectionID=6&SubSectionID=47&ArticleID=79609&PollID=678&btnView=1

According to officials there have been 28 accidents at the intersection between 2012 and 2016 resulting in one fatality and eight injuries.  Half of the accidents were caused by vehicles turning left into the path of oncoming traffic.  Do you really need to put a roundabout in to fix that problem?  If you look at the aerial of the existing intersection (https://www.google.com/maps/@45.63114,-89.43786,19z/data=!3m1!1e3) the left turn bays are offset so somebody trying to make a left-turn can’t see past the vehicle in the opposing left turn lane.  Simply realigning the left turn lanes (which is another option on the table) could greatly improve sight distances for left-turning vehicles and cut down on these dangerous head-on-left-turn crashes.

There are many ways to improve the safety of an intersection that don’t involve building a roundabout.  Innovative intersections that eliminate left turns at the main-intersection can greatly improve safety.  Various studies have shown that signalized Median U-Turn Intersection Treatments (MUTITs) reduced injury crashes by as much as 75%.  Compare that to the Minnesota study where 2x2 roundabouts actually saw a 6% increase in injury crashes.  And unlike complex roundabouts, Median U-Turns can handle high traffic volumes without several fold increases in total crashes.  But the perception is that signals are dangerous and roundabouts are safe.  That’s why agencies keep pushing roundabouts and largely ignore any signalized alternative... WisDOT isn't pushing for a roundabout outright at this intersection, so maybe the perception is slowly changing.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 07, 2017, 10:50:46 AM
So...  It's not actually a crash-prone modern roundabout.  Because it hasn't even been built yet.

Side note:  Apparently, I can only go to the article linked once without subscribing.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 07, 2017, 11:02:19 AM
WisDOT is considering a roundabout for Rhinelander at highways 8 and 47.
http://www.rivernewsonline.com/main.asp?SectionID=6&SubSectionID=47&ArticleID=79609&PollID=678&btnView=1

According to officials there have been 28 accidents at the intersection between 2012 and 2016 resulting in one fatality and eight injuries.  Half of the accidents were caused by vehicles turning left into the path of oncoming traffic.  Do you really need to put a roundabout in to fix that problem?  If you look at the aerial of the existing intersection (https://www.google.com/maps/@45.63114,-89.43786,19z/data=!3m1!1e3) the left turn bays are offset so somebody trying to make a left-turn can’t see past the vehicle in the opposing left turn lane.  Simply realigning the left turn lanes (which is another option on the table) could greatly improve sight distances for left-turning vehicles and cut down on these dangerous head-on-left-turn crashes.

There are many ways to improve the safety of an intersection that don’t involve building a roundabout.  Innovative intersections that eliminate left turns at the main-intersection can greatly improve safety.  Various studies have shown that signalized Median U-Turn Intersection Treatments (MUTITs) reduced injury crashes by as much as 75%.  Compare that to the Minnesota study where 2x2 roundabouts actually saw a 6% increase in injury crashes.  And unlike complex roundabouts, Median U-Turns can handle high traffic volumes without several fold increases in total crashes.  But the perception is that signals are dangerous and roundabouts are safe.  That’s why agencies keep pushing roundabouts and largely ignore any signalized alternative... WisDOT isn't pushing for a roundabout outright at this intersection, so maybe the perception is slowly changing.


As there's a public comment period, you are more than welcome to put in your opinion. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 07, 2017, 11:08:56 AM
WisDOT is considering a roundabout for Rhinelander at highways 8 and 47.
http://www.rivernewsonline.com/main.asp?SectionID=6&SubSectionID=47&ArticleID=79609&PollID=678&btnView=1

[....]

As there's a public comment period, you are more than welcome to put in your opinion.
I wonder if a non-local input is welcomed, and if these hearings are anything more than a required procedure not affecting anything.
And the real question is why a big and expancive build is chosen when a more simple alternative actually exists. Maybe Wisconsin has budget surplus?
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 07, 2017, 11:23:43 AM
WisDOT is considering a roundabout for Rhinelander at highways 8 and 47.
http://www.rivernewsonline.com/main.asp?SectionID=6&SubSectionID=47&ArticleID=79609&PollID=678&btnView=1

[....]

As there's a public comment period, you are more than welcome to put in your opinion.

Quote
I wonder if a non-local input is welcomed
It'll probably be ignored.

Quote
and if these hearings are anything more than a required procedure not affecting anything.
That depends on the project, the agency, the quality of the responses, and who is responding.  Elected politicians generally have the most pull.  Residents that can support their responses with something that doesn't start with "Everyone" may have some pull.  Certain agencies do have their mind made up, and the hearing is a necessary evil.

Quote
And the real question is why a big and expancive build is chosen when a more simple alternative actually exists. Maybe Wisconsin has budget surplus?

Because there's supposed to be more going into these projects than what can be done today to solve yesterday's problems.  What appears 'simple' via a glance at an aerial picture may have more to it. 

Also, being that the 'Do Nothing' option is the cheapest option, that must mean every state with work going on must have budget surpluses, right?

Most often, the cheapest option isn't going to be the best option because of numerous other factors.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 07, 2017, 12:46:11 PM
And the real question is why a big and expancive build is chosen when a more simple alternative actually exists. Maybe Wisconsin has budget surplus?

Because there's supposed to be more going into these projects than what can be done today to solve yesterday's problems.  What appears 'simple' via a glance at an aerial picture may have more to it. 

Also, being that the 'Do Nothing' option is the cheapest option, that must mean every state with work going on must have budget surpluses, right?

Most often, the cheapest option isn't going to be the best option because of numerous other factors.

Well, then there is a specific reason NOT to build a roundabout.
Traffic counts on that spot are just shy of 40k/day (I don't quite understand why, but whatever) - and we saw upper limit for roundabout is about 30K. Right turn traffic is low... SO that roundabout would be overcapacity on day 1 - and only grow worse if traffic goes up.
A flyover may be a truly forward-looking solution, but we have money for roundabout only
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 07, 2017, 01:18:49 PM
Here's a way to view both improvement suggestions without the newspaper site restrictions:

http://wisconsindot.gov/Pages/projects/by-region/nc/us8wis47/default.aspx

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 07, 2017, 04:06:19 PM
Here's a way to view both improvement suggestions without the newspaper site restrictions:

http://wisconsindot.gov/Pages/projects/by-region/nc/us8wis47/default.aspx
Interesting, that both suggestions remove dedicated high speed right turns - which had some mild flavor of roundaboutness to begin with. Merge issues?
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 07, 2017, 04:12:07 PM
Here's a way to view both improvement suggestions without the newspaper site restrictions:

http://wisconsindot.gov/Pages/projects/by-region/nc/us8wis47/default.aspx
Interesting, that both suggestions remove dedicated high speed right turns - which had some mild flavor of roundaboutness to begin with. Merge issues?

Thanks for pointing that out.  I wonder if it's because the scope of the project doesn't extend far enough out from the intersection itself to make any merge improvements, therefore the solution was to simply eliminate them.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 07, 2017, 04:18:43 PM
Here's a way to view both improvement suggestions without the newspaper site restrictions:

http://wisconsindot.gov/Pages/projects/by-region/nc/us8wis47/default.aspx
Interesting, that both suggestions remove dedicated high speed right turns - which had some mild flavor of roundaboutness to begin with. Merge issues?

Thanks for pointing that out.  I wonder if it's because the scope of the project doesn't extend far enough out from the intersection itself to make any merge improvements, therefore the solution was to simply eliminate them.
Scope of the project has to extend enough to include removal, though. I suspect traffic counts on those didn't quite support the case (~1000 each, I already closed that page)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 07, 2017, 04:20:25 PM
Here's a way to view both improvement suggestions without the newspaper site restrictions:

http://wisconsindot.gov/Pages/projects/by-region/nc/us8wis47/default.aspx
Interesting, that both suggestions remove dedicated high speed right turns - which had some mild flavor of roundaboutness to begin with. Merge issues?

Thanks for pointing that out.  I wonder if it's because the scope of the project doesn't extend far enough out from the intersection itself to make any merge improvements, therefore the solution was to simply eliminate them.
Scope of the project has to extend enough to include removal, though. I suspect traffic counts on those didn't quite support the case (~1000 each, I already closed that page)

Right, but scope of project might not include the ability to extend acceleration lanes.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 07, 2017, 09:20:46 PM
They appear to be eliminating the merges to improve pedestrian accommodation. The right turns still appear to be slip lanes with yield signs (judging by the lack of a stop line in the diagram). But, I don't see any crosswalk markings in the intersection, so perhaps its just to cut down on failure-to-yield situations with the current slip lanes. The slip lanes that meet at the angle shown in the diagram have been shown to improve pedestrian safety and reduce collisions.

I would prefer they kept the signalised intersection, with the improved left turns. A really cheap alternative would be to switch the left turns at the current intersection to protected-only, but that would seriously diminish the capacity of the intersection (and judging the current proposal, they already know this since that isn't one of the alternatives).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 08, 2017, 08:55:24 AM
Nobody in misery here.   We enjoy being able to travel without unneeded backups from obsolete traffic lights and 4 way stops.

CJW2001, here’s a challenge for you.  Take a video driving 20 miles through the roundabouts of Carmel and let's see how long it takes you.  Here’s a 20 mile drive through the traffic lights of Detroit (averaged 46 mph over 20 miles).  Just imagine if every traffic signal in the video was a roundabout and how much longer it would take to drive. 



CJW2001, bump that challenge to 40 miles.  At a minimum every Carmel driver has to slow down as they approach a roundabout.  Often drivers will have to come to a complete stop if vehicles are already circulating through the roundabout.  Talk about needless delays!  Maybe Carmel could have spent a few hundred thousand to retime their traffic lights as opposed to spending a few hundred million to construct all those roundabouts - and after all those roundabouts drivers still experience delays as they have to slow down at every roundabout they approach.  Conversely, you could cruise 40 miles hitting 124 consecutive green lights and barely tap your brakes. 


Meanwhile roundabouts number 111 and 112 are opening in Carmel, with no mass carnage. (http://carmellink.com/pdfs/news/4th%20and%20Range%20Line%20RAB%20and%20update.pdf) 

No mass carnage?  There have been 5 documented fatalities over the past decade at Carmel’s roundabout. That is fatal carnage.  I’ve asked you this before but can you cite even one example of a fatal traffic signal crash in Carmel over the past decade?  Considering a decade ago there were more traffic signals than roundabouts in Carmel that should be easy to find.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 08, 2017, 06:38:05 PM
Maybe Carmel could have spent a few hundred thousand to retime their traffic lights as opposed to spending a few hundred million to construct all those roundabouts - and after all those roundabouts drivers still experience delays as they have to slow down at every roundabout they approach.  Conversely, you could cruise 40 miles hitting 124 consecutive green lights and barely tap your brakes.

Yeah good point. All Carmel needs is 180-foot ROW for all their roads, and a diminishing population. Problems solved!
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 08, 2017, 10:49:21 PM
Maybe Carmel could have spent a few hundred thousand to retime their traffic lights as opposed to spending a few hundred million to construct all those roundabouts - and after all those roundabouts drivers still experience delays as they have to slow down at every roundabout they approach.  Conversely, you could cruise 40 miles hitting 124 consecutive green lights and barely tap your brakes.

Yeah good point. All Carmel needs is 180-foot ROW for all their roads, and a diminishing population. Problems solved!

Thanks for posting that.  After logging out last time, I was still wondering how the signal timing in suburban Detroit related to the roundabouts in Carmel.
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on December 09, 2017, 12:17:59 PM
Maybe Carmel could have spent a few hundred thousand to retime their traffic lights as opposed to spending a few hundred million to construct all those roundabouts - and after all those roundabouts drivers still experience delays as they have to slow down at every roundabout they approach.  Conversely, you could cruise 40 miles hitting 124 consecutive green lights and barely tap your brakes.

Yeah good point. All Carmel needs is 180-foot ROW for all their roads, and a diminishing population. Problems solved!
Very well put. I like getting several green lights in a row as much as the next guy but it's not the kind of environment I'd want to live near, let alone be a pedestrian in.
Obviously with all those greens 'someone' is getting a red. When that one car waiting on a side street 'does' get his green it'll mean everyone on the 40 mile 'green light freeway' will have to come to a full stop and have their 250-green-light-series broken up.

SM-T230NU

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 09, 2017, 03:34:46 PM
Maybe Carmel could have spent a few hundred thousand to retime their traffic lights as opposed to spending a few hundred million to construct all those roundabouts - and after all those roundabouts drivers still experience delays as they have to slow down at every roundabout they approach.  Conversely, you could cruise 40 miles hitting 124 consecutive green lights and barely tap your brakes.

Yeah good point. All Carmel needs is 180-foot ROW for all their roads, and a diminishing population. Problems solved!
Very well put. I like getting several green lights in a row as much as the next guy but it's not the kind of environment I'd want to live near, let alone be a pedestrian in.
Obviously with all those greens 'someone' is getting a red. When that one car waiting on a side street 'does' get his green it'll mean everyone on the 40 mile 'green light freeway' will have to come to a full stop and have their 250-green-light-series broken up.

SM-T230NU
And that is exactly how this does NOT work. No surprise people support roundabouts if that is the general level of understanding things...
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 11, 2017, 12:45:04 PM
Maybe Carmel could have spent a few hundred thousand to retime their traffic lights as opposed to spending a few hundred million to construct all those roundabouts - and after all those roundabouts drivers still experience delays as they have to slow down at every roundabout they approach.  Conversely, you could cruise 40 miles hitting 124 consecutive green lights and barely tap your brakes.

Yeah good point. All Carmel needs is 180-foot ROW for all their roads, and a diminishing population. Problems solved!
Very well put. I like getting several green lights in a row as much as the next guy but it's not the kind of environment I'd want to live near, let alone be a pedestrian in.
Obviously with all those greens 'someone' is getting a red. When that one car waiting on a side street 'does' get his green it'll mean everyone on the 40 mile 'green light freeway' will have to come to a full stop and have their 250-green-light-series broken up.

SM-T230NU
And that is exactly how this does NOT work. No surprise people support roundabouts if that is the general level of understanding things...

That doesn't make Carmel=Detroit.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 11, 2017, 03:15:56 PM
Obviously with all those greens 'someone' is getting a red. When that one car waiting on a side street 'does' get his green it'll mean everyone on the 40 mile 'green light freeway' will have to come to a full stop and have their 250-green-light-series broken up.

Here’s an aerial model of how the lights in downtown Portland are timed.  The turning movements are purposely left out to highlight how there is “daylight”  between the platoons.  Sure, there are always turning vehicles filling up this daylight but those movements are much more sporadic than the main platoon.  You seem to be picturing every time a side-street turns green that all the main street traffic has to stop.  That’s not really how it works.  A well timed network of lights would theoretically stop only the sporadic vehicles that made a turn at an upstream signal or those who pulled out of a midblock drive.
 

By the way the closely spaced traffic signals in downtown Portland are timed for 13 mph and help regulate the speed of traffic downtown.  Roundabouts would never be as effective at regulating the speed of traffic in downtown as the traffic signals are.  But you have people mindlessly believing that roundabouts are safer than the traffic signals they replace without question.  Let's hope James Brainard doesn't runs for the mayor of Portland. 
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on December 11, 2017, 03:21:58 PM
Obviously with all those greens 'someone' is getting a red. When that one car waiting on a side street 'does' get his green it'll mean everyone on the 40 mile 'green light freeway' will have to come to a full stop and have their 250-green-light-series broken up.

Here’s an aerial model of how the lights in downtown Portland are timed.  The turning movements are purposely left out to highlight how there is “daylight”  between the platoons.  Sure, there are always turning vehicles filling up this daylight but those movements are much more sporadic than the main platoon.  You seem to be picturing every time a side-street turns green that all the main street traffic has to stop.  That’s not really how it works.  A well timed network of lights would theoretically stop only the sporadic vehicles that made a turn at an upstream signal or those who pulled out of a midblock drive.
 

By the way the closely spaced traffic signals in downtown Portland are timed for 13 mph and help regulate the speed of traffic downtown.  Roundabouts would never be as effective at regulating the speed of traffic in downtown as the traffic signals are.  But you have people mindlessly believing that roundabouts are safer than the traffic signals they replace without question.  Let's hope James Brainard doesn't runs for the mayor of Portland.
No offense, but when it comes to roundabouts I don't find you to be an honest broker.
I'm not saying you have zero data or have made no good points but you're SO anti-roundabout that I'm not sure this thread is rational.

HTC6525LVW

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 14, 2017, 09:13:11 AM
No offense, but when it comes to roundabouts I don't find you to be an honest broker.
I'm not saying you have zero data or have made no good points but you're SO anti-roundabout that I'm not sure this thread is rational.

A December 2017 Caltrans pamphlet promotes the safety of roundabouts by citing decades old IIHS safety statistics.  Next to those impressive numbers is a picture of a complex roundabout that has a propensity to increasing total crashes AND injury crashes.  I’m citing published roundabout research from 2017 - not generic safety statistics from two decades ago.   The definition of propaganda is information, especially of a biased or misleading nature, used to promote or publicize a particular political cause or point of view.   You may think that definition describes my posts.  But isn't it misleading for Caltrans to cite decades old IIHS safety statistics when much more recent roundabout research exists that refute it? 

(https://i.imgur.com/WrjndAm.png)
http://www.dot.ca.gov/milemarker/docs/articles/2017/Q4/MM-2017-Q4-roundabout.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 14, 2017, 03:27:16 PM
isn't it misleading for Caltrans to cite decades old IIHS safety statistics when much more recent roundabout research exists that refute it?

Research exists in this thread, and a few PowerPoints presented at various research conferences (and accompanying PDFs), but there still hasn't been any major country-wide research done on the topic. Just regional stuff that not all traffic engineers might be privy to.

Just a few months ago, I spoke to a local traffic engineer in my area (city of Fife, WA) about flashing yellow arrows. The city recently changed a 4-way intersection with stop signs for the minor road into a fully-protected intersection with protected-only phasing for the left turns. I asked him why they went from minimum control to complete control, and he stated that their consultant suggested it. I asked about protected/permissive phasing, and he stated that left turns against more than one lane should have protected phasing. I informed him of the numerous permissive left turns against three+ lanes of traffic in Federal Way, a city literally due north about three miles, and he told me that he'd never heard of such a thing. I told him that Federal Way had seen a decrease in collisions/injuries, but he told me that he was limited in his options due to this "consultant" evidently holding more power than him.

My point is that engineers sometimes live in these bubbles, where they genuinely aren't privy to work outside of their area. They eventually hear of certain things like roundabouts or Michigan Lefts, many years after they were first implemented, but the follow-up studies sometimes don't reach them. And from what I can tell, rarely do the laziest engineers ever go out and try to see "what's up"...they just keep on doing what they've always been doing, with only occasional innovation. Think of all the protected left turns that Caltrans continues to install. That's so painfully 70s that I'm stunned that they even consider roundabouts, which are effectively the opposite of signals with fully protected phasing.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 14, 2017, 03:44:36 PM
isn't it misleading for Caltrans to cite decades old IIHS safety statistics when much more recent roundabout research exists that refute it?

Research exists in this thread, and a few PowerPoints presented at various research conferences (and accompanying PDFs), but there still hasn't been any major country-wide research done on the topic. Just regional stuff that not all traffic engineers might be privy to.

Just a few months ago, I spoke to a local traffic engineer in my area (city of Fife, WA) about flashing yellow arrows. The city recently changed a 4-way intersection with stop signs for the minor road into a fully-protected intersection with protected-only phasing for the left turns. I asked him why they went from minimum control to complete control, and he stated that their consultant suggested it. I asked about protected/permissive phasing, and he stated that left turns against more than one lane should have protected phasing. I informed him of the numerous permissive left turns against three+ lanes of traffic in Federal Way, a city literally due north about three miles, and he told me that he'd never heard of such a thing. I told him that Federal Way had seen a decrease in collisions/injuries, but he told me that he was limited in his options due to this "consultant" evidently holding more power than him.

My point is that engineers sometimes live in these bubbles, where they genuinely aren't privy to work outside of their area. They eventually hear of certain things like roundabouts or Michigan Lefts, many years after they were first implemented, but the follow-up studies sometimes don't reach them. And from what I can tell, rarely do the laziest engineers ever go out and try to see "what's up"...they just keep on doing what they've always been doing, with only occasional innovation. Think of all the protected left turns that Caltrans continues to install. That's so painfully 70s that I'm stunned that they even consider roundabouts, which are effectively the opposite of signals with fully protected phasing.

Frustratingly true.

The same can be said within Transportation organizations as well.  One engineering department can be for a certain intersection arrangement; another can be against it.  Or one administration be for something; another against it.  You wind up with a single road designed at different times with different arrangements at different intersections, because different teams were involved (and which don't actually talk with each other).

Actually, the same can be said of consultants.  I recall one NJDOT public meeting I went to where they were planning on 'widening' a local road at an intersection.  The current road is one lane per direction with no turn lanes at the intersection.  The widening will consist of adding a single lane left turn channel on each approach.  I asked why they don't widen the main roadway to 2 lanes per direction as well, which is badly needed.  He accused me of being a speed racer who only wanted fast roads.

The same consultant, I learned, was redesigning a local roadway in Virginia. It was going to be 3 or 4 lanes per direction.  I guess they're all speed racers down there if they're getting such a wide roadway.  Shame I didn't know that at the time of the NJDOT meeting.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 14, 2017, 07:12:22 PM
isn't it misleading for Caltrans to cite decades old IIHS safety statistics when much more recent roundabout research exists that refute it?

Research exists in this thread, and a few PowerPoints presented at various research conferences (and accompanying PDFs), but there still hasn't been any major country-wide research done on the topic. Just regional stuff that not all traffic engineers might be privy to.

Just a few months ago, I spoke to a local traffic engineer in my area (city of Fife, WA) about flashing yellow arrows. The city recently changed a 4-way intersection with stop signs for the minor road into a fully-protected intersection with protected-only phasing for the left turns. I asked him why they went from minimum control to complete control, and he stated that their consultant suggested it. I asked about protected/permissive phasing, and he stated that left turns against more than one lane should have protected phasing. I informed him of the numerous permissive left turns against three+ lanes of traffic in Federal Way, a city literally due north about three miles, and he told me that he'd never heard of such a thing. I told him that Federal Way had seen a decrease in collisions/injuries, but he told me that he was limited in his options due to this "consultant" evidently holding more power than him.

My point is that engineers sometimes live in these bubbles, where they genuinely aren't privy to work outside of their area. They eventually hear of certain things like roundabouts or Michigan Lefts, many years after they were first implemented, but the follow-up studies sometimes don't reach them. And from what I can tell, rarely do the laziest engineers ever go out and try to see "what's up"...they just keep on doing what they've always been doing, with only occasional innovation. Think of all the protected left turns that Caltrans continues to install. That's so painfully 70s that I'm stunned that they even consider roundabouts, which are effectively the opposite of signals with fully protected phasing.
You know, sometimes I really wonder if there is a hidden helicopter parking lot near the local DOT building. If they were driving same roads I do, they would definitely notice problems which apparently go unnoticed for decades....
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 19, 2017, 08:09:29 AM
^Apart from the RV blowing through the middle of that Worthington Minnesota roundabout, there has been two other pretty major events at the roundabout over the past couple weeks.

Tanker hauling cream overturns in Worthington roundabout
(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/111117.N.DG_.TANKERCREAM%20rgb_0.jpg?itok=rxMKiQ4I)
http://www.dglobe.com/news/accidents/4356792-tanker-hauling-cream-overturns-worthington-roundabout


These little piggies almost didn't make it to market when a Minn. hog truck rolled

(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/102817.N.DG_.ROLLOVER%203.jpg?itok=DOQatmVs)
http://www.agweek.com/news/4350581-these-little-piggies-almost-didnt-make-it-market-when-minn-hog-truck-rolled

Cream trucks rolling over, hogs running around the highway, some RV driver thinking they are Bo Duke... these roundabouts really give the good people of Worthington Minnesota something to talk about!


Another vehicle vaulted over the Worthington roundabout on Sunday.  The driver sustained non-life threatening injuries.  This comes a month after an RV was videotaped launching over the roundabout in early November.

Minivan vaults over roundabout Sunday
https://www.dglobe.com/news/accidents/4375814-minivan-vaults-over-roundabout-sunday
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 19, 2017, 08:25:29 AM
Walker roundabouts creating more problems than solutions
http://www.wbrz.com/news/walker-roundabouts-creating-more-problems-than-solutions/

Quote
"It's been a tremendous headache for us," said Captain John Sharp. "We're a small police department. We have enough officers to cover routine wrecks, but if we have to take an officer out of the call rotation and put him out here directing traffic, then that leaves us short-handed."

Quote
DOTD put in the roundabouts in August to try and fix the traffic congestion of a growing city, but Walker PD says it's simply not working.

Quote
Captain Sharp says they average about 3 accidents a week on these things.  "This is a state highway. It's a state project. The city of Walker has no input. We have nothing to do with it," said Sharp.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 22, 2017, 08:39:24 AM
Carmel mayor says roundabouts contributing to fewer injury accidents

http://fox59.com/2017/12/21/carmel-mayor-says-roundabouts-contributing-to-fewer-injury-accidents/

The mayor of Carmel cites the reduction of citywide injury crash rates over the past 21 years as prove that roundabouts have made Carmel safer.  He argues that not much has changed in Carmel that would attribute to the reduction in injury crashes...

Quote
“The only big change is our roundabouts, because Indianapolis is about the same. Fishers is about the same. The other surrounding communities have stayed about the same over the last 20 years,”  Brainard said.

But a lot has changed since 1996.   

#1.  Nationwide there has been a 35% reduction in the fatal crash rate from 1996 to today.  Advancements in vehicle safety over the past 21 years has changed.

#2.  The population of Carmel was 31,808 in 1996 and 92,475 today.  With the population nearly tripling over the past 21 years, Carmel has turned less "rural" and more "urban".  Basically the old adage "there are safety in numbers" applies here. 

(https://i.imgur.com/dWt763M.png)

#3.  Two of the major roadways in Carmel (Meridian Street and Keystone Pkwy) were converted from surface streets to grade separated freeways over the past 21 years.  Freeways have lower fatality rates than surface streets, and when two heavily traveled surface streets in your city are converted to grade separated freeways, you should expect a reduction in injury crashes. 

Nowhere in this article does the Mayor mention that there have been 5 fatalities at Carmel roundabouts over the past decade.  Compare that to no known fatal crashes at Carmel traffic signals in the same time period (even as traffic signals in Carmel outnumbered the roundabouts a decade ago).  If traffic signals are so much more dangerous than roundabouts, why has there been an infinitely higher number of fatal crashes at Carmel's roundabouts?  The mayor rightfully says...

Quote
“That’s what it’s really about, building our roadways so they are as safe as possible,”  he said. “We know that humans are always going to error. We are all going to make mistakes. We all do it. The question is can we design our roadways in a safer manner so when that mistake is made it results in a fender bender, not a trip to the hospital or a fatality.”

It's a mistake when a driver blows through the middle of a roundabout.  Consider the fact that there have been 3 fatalities at the Westfield and 96th roundabout over the past decade - in each case the vehicle blew through the roundabout and struck a retaining wall in the central island.  The mayor acknowledges that we all make mistakes, but the roads should be designed so those mistakes results in a fender bender and not a trip to the hospital or morgue in a gurney.  If he really believed that then the retaining wall on the 96th and Westfield roundabout would have been torn down already (instead they doubled down and added some memorial "art" to the central island of the roundabout...the next driver to blow through the roundabout will potentially get speared to death).
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on December 22, 2017, 08:46:16 AM
yet another long post

(https://i.imgur.com/WTDnnwE.gif)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 22, 2017, 09:00:56 AM
It is beating a dead horse when roundabout proponents keep saying how safe roundabouts are.  Jim Brainard's posts would be about 3 words long - "roundabouts are safe" - and he has been mindlessly repeating that mantra for the past 21 years.  Using generic citywide injury crash data (that doesn't directly relate to intersection crashes) isn't a compelling argument.  But don't bother Jim with facts, he is meditating...

Roundabouts are safe...
Roundabouts are safe...
Roundabouts are safe...
Title: Re: Crash prone 'modern roundabouts'
Post by: AlexandriaVA on December 22, 2017, 09:14:46 AM
I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

That said, the data are abundantly clear about the utility of roundabouts, particularly in lower-density areas like Indiana etc.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on December 22, 2017, 09:22:04 AM
this is the worst thread on aaroads
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on December 22, 2017, 09:28:42 AM
No, it isn't the worst thread.  Not by a long shot.

That said, his assertion that increases in population means safer streets made me laugh

I am with the Mayor on this one.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 22, 2017, 09:33:02 AM
I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

That said, the data are abundantly clear about the utility of roundabouts, particularly in lower-density areas like Indiana etc.
Then why are you wasting your time on this (or any other) forum to begin with?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 22, 2017, 09:41:40 AM
That said, his assertion that increases in population means safer streets made me laugh
Can be zillion secondary effects.
More traffic means change in road design.  Tighter control, replacement of two-way stop with traffic lights, lightning, etc.
Reduced speeds.
Change in travel patterns.
Increased police presence and enforcement
Change in demographics (somehow leading to reduced drunk driving or better seatbelt use, for example)

Not sure how that would work for an area going from rural to suburban to urban in a same location, but difference between rural and urban accident rate is very real.
Title: Re: Crash prone 'modern roundabouts'
Post by: AlexandriaVA on December 22, 2017, 09:52:28 AM
I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

That said, the data are abundantly clear about the utility of roundabouts, particularly in lower-density areas like Indiana etc.
Then why are you wasting your time on this (or any other) forum to begin with?

Because I still enjoy the discussions. But I don't know why some people seem so inclined, almost to the point of pathology, to oppose the roundabouts. I think some people are just scared of change.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 22, 2017, 09:58:22 AM
I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

That said, the data are abundantly clear about the utility of roundabouts, particularly in lower-density areas like Indiana etc.
Then why are you wasting your time on this (or any other) forum to begin with?

Because I still enjoy the discussions. But I don't know why some people seem so inclined, almost to the point of pathology, to oppose the roundabouts. I think some people are just scared of change.
How can you enjoy if you yourself said that
I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.
You probably better off trying to ron for some office instead of wasting time on discussions with jockeys
Title: Re: Crash prone 'modern roundabouts'
Post by: AlexandriaVA on December 22, 2017, 10:11:42 AM
I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

That said, the data are abundantly clear about the utility of roundabouts, particularly in lower-density areas like Indiana etc.
Then why are you wasting your time on this (or any other) forum to begin with?

Because I still enjoy the discussions. But I don't know why some people seem so inclined, almost to the point of pathology, to oppose the roundabouts. I think some people are just scared of change.
How can you enjoy if you yourself said that
quote author=AlexandriaVA link=topic=15546.msg2285872#msg2285872 date=1513952086]
I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.
You probably better off trying to ron for some office instead of wasting time on discussions with jockeys
[/quote]

I don't religiously oppose roundabouts unlike some on here. Moreover, the data is pretty clear they work. If you parse anything long enough, you can find the results you want.

My point is that the mayor, as an elected official, has to balance the data, public opinion,internal politics, etc. There's more to road design than just engineering, after all. Given all that, the fact that he endorses them is more illuminating to me than some long-winded manifesto.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 22, 2017, 10:22:30 AM
My point is that the mayor, as an elected official, has to balance the data, public opinion,internal politics, etc. There's more to road design than just engineering, after all. Given all that, the fact that he endorses them is more illuminating to me than some long-winded manifesto.
Of course, that is a big part of entire picture. But given so many stupid things are done in the name of winning the next election, political support means pretty much nothing in technical terms.
 
Quote
. Moreover, the data is pretty clear they work.
It is not, but whatever - see above.
Title: Re: Crash prone 'modern roundabouts'
Post by: AlexandriaVA on December 22, 2017, 10:33:36 AM
My point is that the mayor, as an elected official, has to balance the data, public opinion,internal politics, etc. There's more to road design than just engineering, after all. Given all that, the fact that he endorses them is more illuminating to me than some long-winded manifesto.
Of course, that is a big part of entire picture. But given so many stupid things are done in the name of winning the next election, political support means pretty much nothing in technical terms.
 
Quote
. Moreover, the data is pretty clear they work.
It is not, but whatever - see above.

Then play Sim City. In the real world, political context is a major influence, always has been and always will be.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 22, 2017, 11:44:44 AM
I don't religiously oppose roundabouts unlike some on here. Moreover, the data is pretty clear they work. If you parse anything long enough, you can find the results you want.

I don't oppose all roundabouts.  I oppose roundabouts that have percentage increases in crashes that correlate to the bitcoin bubble. 

To expand on this, complex roundabouts with 2x2 and higher geometries have been shown time-and-time again not to reduce total crashes (in the case of Ann Arbor a complex roundabout saw a 1000% increase in crashes).  In fact, not one documented complex roundabout in America has seen a reduction in crashes when comparing the 3 years of before and after crash data.  But roundabout proponents are quick to point out that these complex roundabouts still reduce injuries.  But do they really?  Recently published research out of Minnesota found that complex roundabouts saw a 6% increase in injury crashes.  The Minnesota research is the first of its kind that specifically looks at the safety performance of complex roundabouts.  Anybody who claims that complex roundabouts reduce injury crashes can’t cite research to support their claims. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 22, 2017, 12:19:12 PM
I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

That said, the data are abundantly clear about the utility of roundabouts, particularly in lower-density areas like Indiana etc.
Then why are you wasting your time on this (or any other) forum to begin with?

Because I still enjoy the discussions. But I don't know why some people seem so inclined, almost to the point of pathology, to oppose the roundabouts. I think some people are just scared of change.

He seems more opposed than most people; I think most engineers would approach the issues raised in this thread with caution, rather than the definite conclusion that tradephoric seems to think he's reached. We can't deny that he's onto something, though. I love roundabouts, just from an aesthetic point of view. But if they aren't as safe as we all thought, why are we defending them?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 22, 2017, 12:33:25 PM
I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

That said, the data are abundantly clear about the utility of roundabouts, particularly in lower-density areas like Indiana etc.
Then why are you wasting your time on this (or any other) forum to begin with?

Because I still enjoy the discussions. But I don't know why some people seem so inclined, almost to the point of pathology, to oppose the roundabouts. I think some people are just scared of change.

He seems more opposed than most people; I think most engineers would approach the issues raised in this thread with caution, rather than the definite conclusion that tradephoric seems to think he's reached. We can't deny that he's onto something, though. I love roundabouts, just from an aesthetic point of view. But if they aren't as safe as we all thought, why are we defending them?
These days it is really hard to relay a message until it is delivered with a good dose of doom, hysteria and end of the world message. Looking at things from that perspective, Trade is fairly mild and tries to keep emphases on facts and statistics with just thin icing on his cake.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 22, 2017, 12:43:13 PM
I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

That said, the data are abundantly clear about the utility of roundabouts, particularly in lower-density areas like Indiana etc.
Then why are you wasting your time on this (or any other) forum to begin with?

Because I still enjoy the discussions. But I don't know why some people seem so inclined, almost to the point of pathology, to oppose the roundabouts. I think some people are just scared of change.

He seems more opposed than most people; I think most engineers would approach the issues raised in this thread with caution, rather than the definite conclusion that tradephoric seems to think he's reached. We can't deny that he's onto something, though. I love roundabouts, just from an aesthetic point of view. But if they aren't as safe as we all thought, why are we defending them?
These days it is really hard to relay a message until it is delivered with a good dose of doom, hysteria and end of the world message. Looking at things from that perspective, Trade is fairly mild and tries to keep emphases on facts and statistics with just thin icing on his cake.

But he's losing his credibility by posting these "think of the children" posts every other day. As I've mentioned before, you can't take traffic engineering personally. People will find a way to kill themselves using something you've designed. We need to be more rational. Trade isn't helping his cause by reporting on individual crashes. His whole point is how many crashes there are.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 22, 2017, 12:48:54 PM
I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

That said, the data are abundantly clear about the utility of roundabouts, particularly in lower-density areas like Indiana etc.
Then why are you wasting your time on this (or any other) forum to begin with?

Because I still enjoy the discussions. But I don't know why some people seem so inclined, almost to the point of pathology, to oppose the roundabouts. I think some people are just scared of change.

He seems more opposed than most people; I think most engineers would approach the issues raised in this thread with caution, rather than the definite conclusion that tradephoric seems to think he's reached. We can't deny that he's onto something, though. I love roundabouts, just from an aesthetic point of view. But if they aren't as safe as we all thought, why are we defending them?
These days it is really hard to relay a message until it is delivered with a good dose of doom, hysteria and end of the world message. Looking at things from that perspective, Trade is fairly mild and tries to keep emphases on facts and statistics with just thin icing on his cake.

But he's losing his credibility by posting these "think of the children" posts every other day. As I've mentioned before, you can't take traffic engineering personally. People will find a way to kill themselves using something you've designed. We need to be more rational. Trade isn't helping his cause by reporting on individual crashes. His whole point is how many crashes there are.
You didn't get it.
Then play Sim City. In the real world, political context is a major influence, always has been and always will be.
"Think about kids!" is one of those things which are perfectly winning cause for 90% of voters.  Trade uses that, but uses pretty mildly - that's my point.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 22, 2017, 01:14:24 PM
But he's losing his credibility by posting these "think of the children" posts every other day. As I've mentioned before, you can't take traffic engineering personally. People will find a way to kill themselves using something you've designed. We need to be more rational. Trade isn't helping his cause by reporting on individual crashes. His whole point is how many crashes there are.

You didn't get it.
Then play Sim City. In the real world, political context is a major influence, always has been and always will be.

"Think about kids!" is one of those things which are perfectly winning cause for 90% of voters.  Trade uses that, but uses pretty mildly - that's my point.

But this thread isn't a PR campaign. I'm influenced by facts. Hence why I'm not as pro-roundabout as I used to be. Lately I'm more anti-tradephoric.  :-D
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 22, 2017, 02:44:24 PM
(https://i.imgur.com/dWt763M.png)

In my opinion, this graph should be weighted to reflect the difference in total miles driven by rural and urban drivers (12,264 and 9,709 respectively).  The gap still exists either way, but it should be roughly 26% narrower.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 22, 2017, 02:57:28 PM
But he's losing his credibility by posting these "think of the children" posts every other day. As I've mentioned before, you can't take traffic engineering personally. People will find a way to kill themselves using something you've designed. We need to be more rational. Trade isn't helping his cause by reporting on individual crashes. His whole point is how many crashes there are.

You didn't get it.
Then play Sim City. In the real world, political context is a major influence, always has been and always will be.

"Think about kids!" is one of those things which are perfectly winning cause for 90% of voters.  Trade uses that, but uses pretty mildly - that's my point.

But this thread isn't a PR campaign. I'm influenced by facts. Hence why I'm not as pro-roundabout as I used to be. Lately I'm more anti-tradephoric.  :-D
and how many people are able to change their mind  to begin with? Usually it takes significant authority (boss, professor, president) for people to change their mind.  I remember when you started to turn roundabout-skeptical - and I was telling to myself "no way I witness THAT!" You really broke my perception of how these discussions work.   A more typical approach is
Moreover, the data is pretty clear they work. If you parse anything long enough, you can find the results you want.
This one is specifically interesting due to "data" statement.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 22, 2017, 03:01:14 PM
(https://i.imgur.com/dWt763M.png)

In my opinion, this graph should be weighted to reflect the difference in total miles driven by rural and urban drivers (12,264 and 9,709 respectively).  The gap still exists either way, but it should be roughly 26% narrower.
What is the reason for such weighting? You want to assign crash probabiluity to trip, as opposed to per-mile?
That may make sense if some trips are doomed to begin with, e.g. drunk trips. Which is entirely possible, quoting some random page:
Quote
Alcohol use — Drinking and driving is often a bigger problem in rural areas for several reasons. First, there are generally no taxicabs, subways, or other forms of public transportation to use as an alternative for driving while impaired. Also, because of the often large distance between homes and towns, having a designated driver often does not seem convenient in rural areas. For this reason, drunk driving occurs frequently and can result in serious accidents.
https://www.dolmanlaw.com/auto-accidents-common-rural-urban-areas/
But that justifies expected decrease of crash per-mile AND per-trip rate as population density goes up.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 22, 2017, 03:10:47 PM
I remember when you started to turn roundabout-skeptical - and I was telling to myself "no way I witness THAT!" You really broke my perception of how these discussions work.   A more typical approach is
Moreover, the data is pretty clear they work. If you parse anything long enough, you can find the results you want.
This one is specifically interesting due to "data" statement.

Yeah exactly.  They reference "data" that proves roundabouts work, only to not post any "data".  Of course if they did cite that 2000 IIHS study, which is seen as the authoritative study on roundabout safety in America, they would fail to see how flimsy that study is anyways.  Of the 24 roundabouts analyzed in the 2000 IIHS study, only 9 were double-lane roundabouts and they were all concentrated in the Colorado ski-resort towns of Avon and Vail.  Here are aerials of the 9 double-lane roundabouts analyzed in the study:

(2 roundabouts):  I-70 & Vail Road interchange roundabouts in Vail, CO
https://www.google.com/maps/@39.6444378,-106.3779447,18z/data=!3m1!1e3

(2 roundabouts): I-70 & Chamonix Rd interchange roundabouts in Vail, CO
https://www.google.com/maps/@39.6280191,-106.4215908,409m/data=!3m1!1e3

(5 roundabouts) 2500 ft section of Avon Road in Avon, CO (Avon Rd is signed for 25 mph):
https://www.google.com/maps/@39.63489,-106.52215,16z/data=!3m1!1e3

The perceived safety of double-lane roundabouts in America is based on a few interchange roundabouts in Vail and a corridor of 5 roundabouts along a 2500 feet section of Avon Road (signed for 25 mph).  Far from comprehensive (and the study itself is only 15 pages long).  Good thing double-lane roundabouts outside of ski-resort towns in Colorado were analyzed... ooh wait, they weren't.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 22, 2017, 03:48:57 PM
(https://i.imgur.com/dWt763M.png)

In my opinion, this graph should be weighted to reflect the difference in total miles driven by rural and urban drivers (12,264 and 9,709 respectively).  The gap still exists either way, but it should be roughly 26% narrower.
What is the reason for such weighting? You want to assign crash probabiluity to trip, as opposed to per-mile?

Because the graph was used in support of the assertion that the urbanization of Carmel has been the reason for its reduction in vehicle crash deaths as measured over a certain amount of time.  Injury crash rates are measured in incidents per year.  The number of crashes at a given intersection over the course of a given year is not related to the total number of miles the average vehicle through the intersection drives in a year.

Think about it this way.  If Bobby's daily commute in a rural area has him driving 10 miles each way, while Johnny's daily commute in an urban area has him driving 8 miles each way (I'm pulling those numbers out of my butt just because they're approximately 26% apart), and they each get into one accident over the course of ten years–who cares how many miles each one's commute was?  The rate as it relates to this thread topic would be 1 accident in 10 years for both drivers.  But, as represented on the graph provided by tradephoric, it would come out to something like 8 accidents per million miles for Bobby and 10 accidents per million miles for Freddy.  Same amount of time, same number of crashes, different rates.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 22, 2017, 03:50:57 PM
I remember when you started to turn roundabout-skeptical - and I was telling to myself "no way I witness THAT!" You really broke my perception of how these discussions work.   A more typical approach is
Moreover, the data is pretty clear they work. If you parse anything long enough, you can find the results you want.
This one is specifically interesting due to "data" statement.

Yeah exactly.  They reference "data" that proves roundabouts work, only to not post any "data".  Of course if they did cite that 2000 IIHS study, which is seen as the authoritative study on roundabout safety in America, they would fail to see how flimsy that study is anyways.  Of the 24 roundabouts analyzed in the 2000 IIHS study, only 9 were double-lane roundabouts and they were all concentrated in the Colorado ski-resort towns of Avon and Vail.  Here are aerials of the 9 double-lane roundabouts analyzed in the study:

(2 roundabouts):  I-70 & Vail Road interchange roundabouts in Vail, CO
https://www.google.com/maps/@39.6444378,-106.3779447,18z/data=!3m1!1e3

(2 roundabouts): I-70 & Chamonix Rd interchange roundabouts in Vail, CO
https://www.google.com/maps/@39.6280191,-106.4215908,409m/data=!3m1!1e3

(5 roundabouts) 2500 ft section of Avon Road in Avon, CO (Avon Rd is signed for 25 mph):
https://www.google.com/maps/@39.63489,-106.52215,16z/data=!3m1!1e3

The perceived safety of double-lane roundabouts in America is based on a few interchange roundabouts in Vail and a corridor of 5 roundabouts along a 2500 feet section of Avon Road (signed for 25 mph).  Far from comprehensive (and the study itself is only 15 pages long).  Good thing double-lane roundabouts outside of ski-resort towns in Colorado were analyzed... ooh wait, they weren't.

Roundabouts "working" and roundabouts being safe aren't the same thing, are they?  I interpreted the statement "the data is pretty clear they work" as meaning "the data is pretty clear they're efficient."
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 22, 2017, 03:59:38 PM

Think about it this way.  If Bobby's daily commute in a rural area has him driving 10 miles each way, while Johnny's daily commute in an urban area has him driving 8 miles each way (I'm pulling those numbers out of my butt just because they're approximately 26% apart), and they each get into one accident over the course of ten years–who cares how many miles each one's commute was?  The rate as it relates to this thread topic would be 1 accident in 10 years for both drivers.  But, as represented on the graph provided by tradephoric, it would come out to something like 8 accidents per million miles for Bobby and 10 accidents per million miles for Freddy.  Same amount of time, same number of crashes, different rates.
I have hard time buying that logic.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 22, 2017, 04:01:39 PM

Roundabouts "working" and roundabouts being safe aren't the same thing, are they?  I interpreted the statement "the data is pretty clear they work" as meaning "the data is pretty clear they're efficient."
Then what do you mean by "work"? Have some throughput? Yes, they do. So does an all-way stop and traffic light and grade-separated intersection.
So what?
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 22, 2017, 04:10:55 PM

Think about it this way.  If Bobby's daily commute in a rural area has him driving 10 miles each way, while Johnny's daily commute in an urban area has him driving 8 miles each way (I'm pulling those numbers out of my butt just because they're approximately 26% apart), and they each get into one accident over the course of ten years–who cares how many miles each one's commute was?  The rate as it relates to this thread topic would be 1 accident in 10 years for both drivers.  But, as represented on the graph provided by tradephoric, it would come out to something like 8 accidents per million miles for Bobby and 10 accidents per million miles for Freddy.  Same amount of time, same number of crashes, different rates.
I have hard time buying that logic.

I'm not a statistician.  Please point out my flaw.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 22, 2017, 04:28:46 PM
But he's losing his credibility by posting these "think of the children" posts every other day. As I've mentioned before, you can't take traffic engineering personally. People will find a way to kill themselves using something you've designed. We need to be more rational. Trade isn't helping his cause by reporting on individual crashes. His whole point is how many crashes there are.

You didn't get it.
Then play Sim City. In the real world, political context is a major influence, always has been and always will be.

"Think about kids!" is one of those things which are perfectly winning cause for 90% of voters.  Trade uses that, but uses pretty mildly - that's my point.

But this thread isn't a PR campaign. I'm influenced by facts. Hence why I'm not as pro-roundabout as I used to be. Lately I'm more anti-tradephoric.  :-D

and how many people are able to change their mind  to begin with? Usually it takes significant authority (boss, professor, president) for people to change their mind.  I remember when you started to turn roundabout-skeptical - and I was telling to myself "no way I witness THAT!" You really broke my perception of how these discussions work.   A more typical approach is

Short of Jim Brainard becoming dictator of the US, and forcing all intersections to become roundabouts, people are able to think freely. Most people are fine with signals because they're used to them. And just as many are fine with roundabouts after getting used to them.

Most engineers are easily persuaded by facts. They're mostly all math geeks anyway. They live day to day based on logic and reason. It's when they start playing with roundabouts and DDIs that their emotions get involved ("less conflict points!"). The problem, as I've pointed out previously, is that not all engineers are privy to the same data. Hence why I wish tradephoric would start working on an independent report that he could present at a TRB conference (pay someone under the table to let you speak), instead of posting these meaningless stories about one-off crashes.

You can tell how much I like good-old signals by how often I use them in Cities: Skylines. Many of my old cities had roundabouts all over the place, but they often got backed up, so my current city only has two (although both are 2x2).
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 22, 2017, 04:38:06 PM

Roundabouts "working" and roundabouts being safe aren't the same thing, are they?  I interpreted the statement "the data is pretty clear they work" as meaning "the data is pretty clear they're efficient."
Then what do you mean by "work"? Have some throughput? Yes, they do. So does an all-way stop and traffic light and grade-separated intersection.
So what?

I'm not the one who made the original statement.  But "working" could mean increasing throughput over a four-way stop, reducing tailbacks, etc.  You should ask AlexandriaVA what he meant, not me.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 22, 2017, 04:49:05 PM

Roundabouts "working" and roundabouts being safe aren't the same thing, are they?  I interpreted the statement "the data is pretty clear they work" as meaning "the data is pretty clear they're efficient."
Then what do you mean by "work"? Have some throughput? Yes, they do. So does an all-way stop and traffic light and grade-separated intersection.
So what?

I'm not the one who made the original statement.  But "working" could mean increasing throughput over a four-way stop, reducing tailbacks, etc.  You should ask AlexandriaVA what he meant, not me.
again, basic Trade's message is that it is OK to replace 4-way with roundabout, it is not OK to replace a traffic light with one (rephrasing a bit - 2x2 lane arrangement not working with stop signs)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 22, 2017, 04:51:29 PM

Short of Jim Brainard becoming dictator of the US, and forcing all intersections to become roundabouts, people are able to think freely.
:bigass: :bigass: :bigass: :bigass: :bigass: :bigass:
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 22, 2017, 04:55:15 PM
^^
Laughs aside, he's basically dictator of the public works department in Carmel, IN. There's very little free thinking in that office, me thinks.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 22, 2017, 04:59:51 PM
^^
Laughs aside, he's basically dictator of the public works department in Carmel, IN. There's very little free thinking in that office, me thinks.
Laughing aside, it takes a bit of an effort to get some understanding of a topic. Granted, any driver has at least some understanding how standard traffic control arrangements work - but you need a better idea about underlying concepts to develop opinion going beyond "i like/don't like it"
Especially visible on politically charged topics - and roundabouts also slowly drift into that category.
As for other examples... "Zisis sajens" mobs are probably latest one.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 27, 2017, 11:11:01 AM
I wish tradephoric would start working on an independent report that he could present at a TRB conference (pay someone under the table to let you speak), instead of posting these meaningless stories about one-off crashes.

This would probably be the first slide in my TRB presentation.  The average crash rate of complex roundabouts in America is about 4 MEV.  This is looking at crash rates of complex roundabouts throughout the entire country, not JUST ski resort towns in Colorado.  Conversely, the average crash rate of a typical signalized intersection is below 1 MEV.  When crashes at complex roundabouts are about 4x higher than comparable signalized intersections, there is no guarantee there will be a reduction in injury crashes.  Put another way the big increase in total crashes offsets the fact that roundabouts have a lower crash severity.  Recently published research supports this, and found that injury crashes increased by 6% at complex roundabouts in Minnesota. 

(https://i.imgur.com/6WNy8fs.png)

Is it worth building these complex roundabouts when you see a big increase in total crashes and a wash in injury crashes?  I would point out all the roundabouts highlighted in yellow have been reconfigured to eliminate circulating lanes to simplify the configuration.  Communities are having to deal with these crash prone complex roundabouts.... Raleigh, Woodbury, Bloomfield, Farmington, Tri-Cities, Venice, Kitchener, Gahanna, and De Pere to name a few.  The roundabouts that haven’t been downsized still experience significantly high crash rates.  Case in point M-5 & Pontiac Trail… constructed in 2011 it is consistently near the top of Michigan’s annual top crash intersections list.   By the way 116th and Illinois should no longer be highlighted yellow… that roundabout was temporarily downsized for a construction project on 116th but it has been resized back to a 2x2.

Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 27, 2017, 11:43:49 AM
I wish tradephoric would start working on an independent report that he could present at a TRB conference (pay someone under the table to let you speak), instead of posting these meaningless stories about one-off crashes.

This would probably be the first slide in my TRB presentation.  The average crash rate of complex roundabouts in America is about 4 MEV.  This is looking at crash rates of complex roundabouts throughout the entire country, not JUST ski resort towns in Colorado.  Conversely, the average crash rate of a typical signalized intersection is below 1 MEV.  When crashes at complex roundabouts are about 4x higher than comparable signalized intersections, there is no guarantee there will be a reduction in injury crashes.  Put another way the big increase in total crashes offsets the fact that roundabouts have a lower crash severity.  Recently published research supports this, and found that injury crashes increased by 6% at complex roundabouts in Minnesota. 

(https://i.imgur.com/6WNy8fs.png)

This is a hilariously incomplete list of 2x2 or greater roundabouts in the country.  Apparently the 'average' takes into account just high-crash roundabouts, and weeds out anything without a large crash rate.  That's like saying I was an A student in high school if you don't count any grades of B and below.

I'm especially amused that this list of American roundabouts includes Quebec and Ontario.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 27, 2017, 12:40:21 PM
I still want to know about the closest 2x2 roundabout to me that I'm aware of:  Sheridan/Ridgeview/Rogers in Olathe, KS.  This was constructed at least 13 years ago, because I can find mention of it from 2004.  That year, its max vehicle/hour count was 1784 in the afternoon rush.  I can't find any reports of an accident there at all, but I know my sleuthing skills don't match tradephoric's.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 27, 2017, 03:18:41 PM
This is a hilariously incomplete list of 2x2 or greater roundabouts in the country.  Apparently the 'average' takes into account just high-crash roundabouts, and weeds out anything without a large crash rate.  That's like saying I was an A student in high school if you don't count any grades of B and below.

You were an “F”  grade student because you didn’t show your work.  You could easily prove I ignore low-crash rate complex roundabouts by simply citing them.  Let’s say any roundabout with a crash rate below 0.8 MEV is considered low (that is about the average crash rate for a signalized intersection).  You yourself said my list was hilariously incomplete.  Then there must be a hilariously high number of complex roundabouts with low-crash rates i ignored.  Humor me.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 27, 2017, 03:48:23 PM
This is a hilariously incomplete list of 2x2 or greater roundabouts in the country.  Apparently the 'average' takes into account just high-crash roundabouts, and weeds out anything without a large crash rate.  That's like saying I was an A student in high school if you don't count any grades of B and below.

You were an “F” grade student because you didn’t show your work.  You could easily prove I ignore low-crash rate complex roundabouts by simply citing them.  Let’s say any roundabout with a crash rate below 0.8 MEV is considered low (that is about the average crash rate for a signalized intersection).  You yourself said my list was hilariously incomplete.  Then there must be a hilariously high number of complex roundabouts with low-crash rates i ignored.  Humor me.

We'll start with this one, which is your own posting: https://www.aaroads.com/forum/index.php?topic=15546.msg2223079#msg2223079

Don't like that one?  Then choose any of the other dozen or so 2x2 roundabouts that exist around The Villages, FL.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 27, 2017, 04:32:26 PM
^I fail to see how a post about a driver crashing through a building in the middle of a roundabout in The Villages is proof that the roundabout has a low-crash rate.  I asked you a specific request -  to cite a complex roundabout that has a crash rate below 0.8 MEV.  You failed to do that.

Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on December 27, 2017, 10:19:31 PM
Shouldn't that be .8 per MEV?
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 27, 2017, 10:22:57 PM
And I said your list is incomplete. You provided a minimal list and then claimed the average of ALL complex roundabouts is computed based on that list.

I don't need to show a single one...not that it matters because I don't know where you get your data from. I quickly and easily proved You didn't list all complex roundabouts. Since we all know you have the data, just provide the list.

And I noticed you failed to address the fact you included Canadian roundabouts on your American list.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on December 27, 2017, 10:26:58 PM
I'm also wondering about more recent data on the NY 85/140 roundabout in Slingerlands, NY.  Crash rates must have plummeted there.
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on December 27, 2017, 11:49:53 PM
To begin with, we would need a number of the number of complex roundabouts in the US, in order to determine what a representative sample size would be.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 27, 2017, 11:58:52 PM
To begin with, we would need a number of the number of complex roundabouts in the US, in order to determine what a representative sample size would be.

I think the bigger issue is that none of us have access to the data required to do a comprehensive study on the matter.
Title: Re: Crash prone 'modern roundabouts'
Post by: US 89 on December 28, 2017, 12:29:42 AM
This is a hilariously incomplete list of 2x2 or greater roundabouts in the country.  Apparently the 'average' takes into account just high-crash roundabouts, and weeds out anything without a large crash rate.  That's like saying I was an A student in high school if you don't count any grades of B and below.

You were an “F” grade student because you didn’t show your work.  You could easily prove I ignore low-crash rate complex roundabouts by simply citing them.  Let’s say any roundabout with a crash rate below 0.8 MEV is considered low (that is about the average crash rate for a signalized intersection).  You yourself said my list was hilariously incomplete.  Then there must be a hilariously high number of complex roundabouts with low-crash rates i ignored.  Humor me.

Uh, you’re the one who didn’t show your work. You cherry picked 40 or so roundabouts that you could find that had very high crash rates, and found the average crash rate for only those, and you’re saying that applies to all multilane roundabouts. That makes your stats invalid. It’s like a poll where they tell you only negative things about a politician and then ask what your opinion on that politician is now.

Also, it looks like you ran out of roundabouts in the US with high enough crash rates, so you decided to pull a few out of Canada to help prove your point.



To begin with, we would need a number of the number of complex roundabouts in the US, in order to determine what a representative sample size would be.

I think the bigger issue is that none of us have access to the data required to do a comprehensive study on the matter.

I’m sure tradephoric could find that data somewhere, but he wouldn’t want to dig into it because of fear that it wouldn’t prove his point.
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on December 28, 2017, 12:43:01 AM
To begin with, we would need a number of the number of complex roundabouts in the US, in order to determine what a representative sample size would be.

I think the bigger issue is that none of us have access to the data required to do a comprehensive study on the matter.

It could probably be acquired through creative FOIA requests, but doing so would require a lot of time and effort.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 28, 2017, 01:24:34 AM
To begin with, we would need a number of the number of complex roundabouts in the US, in order to determine what a representative sample size would be.

I think the bigger issue is that none of us have access to the data required to do a comprehensive study on the matter.

It could probably be acquired through creative FOIA requests, but doing so would require a lot of time and effort.

And Trade has come out and admitted before that he piecemeal's his data, but only because so many transport departments don't publish crash numbers. He's lucky to find any numbers to work with. Further in his defence, it's rather interesting that the only intersections he can find information for, almost universally perform poorly.

FOIA requests are a sure-fire way of getting data, but would indeed by time consuming. Our best hope would be for the FHWA to perform a comprehensive study, since (AFAIK) they don't need to go down the FOIA trail.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on December 28, 2017, 07:50:27 AM
The fact that FOIA or state-equivalent requests (e.g., NY's FOIL) are required does not negate the fact that Tradephoric's sample of data is probably biased and unrepresentative of the population.  Count me with those that consider him a data cherry picker.  Coming to conclusions based upon biased data is still inappropriate when proper data is just harder to get than a Google search.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 28, 2017, 08:16:33 AM
The fact that FOIA or state-equivalent requests (e.g., NY's FOIL) are required does not negate the fact that Tradephoric's sample of data is probably biased and unrepresentative of the population.  Count me with those that consider him a data cherry picker.  Coming to conclusions based upon biased data is still inappropriate when proper data is just harder to get than a Google search.
Everyone has an agenda today, but very few have an idea about statistics - so good dataset is not expected until FHWA gets a good shock (like a major school bus accident on a roundabout)
Within this forum, other side didn't present any dataset from past 10 years, so there is no logical choice other than taking trade's data at face value. Any other opinion is uneducated guesswork at best. But of course, First Amendment protects religious believes - so feel free...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 28, 2017, 09:16:49 AM
Uh, you’re the one who didn’t show your work. You cherry picked 40 or so roundabouts that you could find that had very high crash rates, and found the average crash rate for only those, and you’re saying that applies to all multilane roundabouts. That makes your stats invalid. It’s like a poll where they tell you only negative things about a politician and then ask what your opinion on that politician is now.

Or like how the IIHS only tells you positive things about roundabouts and then ask you what your opinion on that roundabout is.  The IIHS national study analyzed 9 multi-lane roundabouts in Colorado.  What about the other 49 states?  Cherry picking!  Of the 9 multi-lane roundabouts, 6 of them serviced interchanges along I-70.  Interchange roundabouts historically have lower crash rates when compared to non-interchange roundabouts.  Cherry picking!  Of the 3 non-interchange roundabouts analyzed, they were all along Avon Road which is signed for 25 mph.  The safety statistics of non-interchange multi-lane roundabouts are based on a 1500 foot section of Avon Road where drivers are traveling at subdivision street speeds.  Cherry picking! 

More recently the IIHS acknowledged that people are having difficulty navigating two-lane roundabouts.  Even then they only analyzed two multi-lane roundabouts near Bellingham, Washington (and only one of them was a true balanced 2x2 roundabout).  Cherry picking!  In addition, the 2x2 roundabout picked for the analysis has a very low AADT compared to other multi-lane roundabouts in the country.  At a low volume 2x2 roundabout there are more gaps in traffic and it’s less likely that a vehicle entering the roundabout will even encounter another vehicle.  Cherry picking!  Even with the favorable analysis, the IIHS acknowledged that noninjury crashes were 6 times as high at the Wiser Lake intersection as they would have been without the roundabout conversions.  Based on a single 2x2 roundabout analyzed, the Insurance Institute’s senior vice president Anne McCartt states the following:

Quote
"We don't know why noninjury crashes are so much higher than expected, but it may be related to confusion about right-of-way rules and other issues that drivers reported to us," McCartt says. "Nevertheless, these roundabouts are making travelers safer by reducing injury crashes."
http://www.iihs.org/iihs/sr/statusreport/article/48/2/3

Good thing the IIHS cherry picked one the most favorable 2x2 roundabout to come to the conclusion that injury crashes are being reduced (not to mention a 2x1 roundabout was thrown in with their analysis for good measure).   The IIHS doesn’t seem to understand the problem if they think it’s appropriate to lump the crash data of unbalanced 2x1 and balanced 2x2 roundabouts together.  They are just looking for a result they want.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 28, 2017, 09:32:44 AM
Uh, you’re the one who didn’t show your work. You cherry picked 40 or so roundabouts that you could find that had very high crash rates, and found the average crash rate for only those, and you’re saying that applies to all multilane roundabouts. That makes your stats invalid. It’s like a poll where they tell you only negative things about a politician and then ask what your opinion on that politician is now.

Or like how the IIHS only tells you positive things about roundabouts and then ask you what your opinion on that roundabout is.  The IIHS national study analyzed 9 multi-lane roundabouts in Colorado.  What about the other 49 states?  Cherry picking!  Of the 9 multi-lane roundabouts, 6 of them serviced interchanges along I-70.  Interchange roundabouts historically have lower crash rates when compared to non-interchange roundabouts.  Cherry picking!  Of the 3 non-interchange roundabouts analyzed, they were all along Avon Road which is signed for 25 mph.  The safety statistics of non-interchange multi-lane roundabouts are based on a 1500 foot section of Avon Road where drivers are traveling at subdivision street speeds.  Cherry picking! 

More recently the IIHS acknowledged that people are having difficulty navigating two-lane roundabouts.  Even then they only analyzed two multi-lane roundabouts near Bellingham, Washington (and only one of them was a true balanced 2x2 roundabout).  Cherry picking!  In addition, the 2x2 roundabout picked for the analysis has a very low AADT compared to other multi-lane roundabouts in the country.  At a low volume 2x2 roundabout there are more gaps in traffic and it’s less likely that a vehicle entering the roundabout will even encounter another vehicle.  Cherry picking!  Even with the favorable analysis, the IIHS acknowledged that noninjury crashes were 6 times as high at the Wiser Lake intersection as they would have been without the roundabout conversions.  Based on a single 2x2 roundabout analyzed, the Insurance Institute’s senior vice president Anne McCartt states the following:

Quote
"We don't know why noninjury crashes are so much higher than expected, but it may be related to confusion about right-of-way rules and other issues that drivers reported to us," McCartt says. "Nevertheless, these roundabouts are making travelers safer by reducing injury crashes."
http://www.iihs.org/iihs/sr/statusreport/article/48/2/3

Good thing the IIHS cherry picked one the most favorable 2x2 roundabout to come to the conclusion that injury crashes are being reduced (not to mention a 2x1 roundabout was thrown in with their analysis for good measure).   The IIHS doesn’t seem to understand the problem if they think it’s appropriate to lump the crash data of unbalanced 2x1 and balanced 2x2 roundabouts together.  They are just looking for a result they want.


If you're aware of these roundabouts and their MEV rates, why aren't they included in your table?

If you are looking at American roundabouts, why did you lump poorly performing Canadian roundabouts in your table?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 28, 2017, 09:50:40 AM

If you're aware of these roundabouts and their MEV rates, why aren't they included in your table?

If you are looking at American roundabouts, why did you lump poorly performing Canadian roundabouts in your table?
Well, maybe because IIHS has their agenda and reported injury crush rate only? Everything else is in relative terms, which is a common way to obscure data presenter wants to withhold. I can understand when that happens to proprietary data, but for IIHS it is what it is.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 28, 2017, 10:13:34 AM
If you're aware of these roundabouts and their MEV rates, why aren't they included in your table?

If you are looking at American roundabouts, why did you lump poorly performing Canadian roundabouts in your table?

The crash rate is the number of crashes per million entering vehicle.  That is listed on my table (the very last column).  OTOH, injury crashes are a lot harder to come by and those are not listed.  I know that leads to "well roundabouts are safer.. who cares about total crashes.. injuries are what matters". But there has to be some understanding that there is a percentage of injury crashes that occur at roundabouts.  When total crashes spike, that increases the opportunity for injury crashes as well.  In the case of the Minnesota research, an over 200% increase in total crashes at complex roundabouts led to a 6% increase in injury crashes as well.

(https://i.imgur.com/6WNy8fs.png)

Would ignoring the few Canadian roundabouts listed on this chart really change anything?  There is still a crash problem at these complex roundabouts.  Canadian drivers don't drive on the opposite side of the road or drive much differently than American drivers.  But if you think there is an abundance of complex Canadian roundabouts that have a low crash rate that I'm simply ignoring, you are welcome to cite them.  If you do find them, let me know because i would be interested in reviewing their design.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 28, 2017, 11:33:01 AM
Would ignoring the few Canadian roundabouts listed on this chart really change anything?  There is still a crash problem at these complex roundabouts.  Canadian drivers don't drive on the opposite side of the road or drive much differently than American drivers.  But if you think there is an abundance of complex Canadian roundabouts that have a low crash rate that I'm simply ignoring, you are welcome to cite them.  If you do find them, let me know because i would be interested in reviewing their design.

What does driving on the other side of the road matter, except allow you to ignore 2x2 roundabouts in England that have low crash rates?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 28, 2017, 03:53:53 PM
Canada does have a lower deaths-per-100k-inhabitants rate than the US:

https://en.m.wikipedia.org/wiki/List_of_countries_by_traffic-related_death_rate

Canada: 6.0
USA: 10.6

As far as I can tell, Canadian provinces do have more thorough driving exams than most US states (BC even uses rear decals like the UK and Australia).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 28, 2017, 04:08:20 PM
Canada does have a lower deaths-per-100k-inhabitants rate than the US:

https://en.m.wikipedia.org/wiki/List_of_countries_by_traffic-related_death_rate

Canada: 6.0
USA: 10.6

As far as I can tell, Canadian provinces do have more thorough driving exams than most US states (BC even uses rear decals like the UK and Australia).
US range of numbers if from 4.0 (DC) to 23.1 (MS) vs 6.0 in Canada.
Normalized to 1B km travel, Canada is 6.2, US 7.1 (range 10.6 KY to 4.1 in MA, MN).
US (and Canada, for that matter) is big and diverse. I would say comparing US as a whole to Canada as a whole is better than comparing Northeast to mid-south. Is it valid to put US and Canada into same statistical bucket? Probably better that US and China... 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 29, 2017, 08:33:00 AM
I don't need to show a single one...not that it matters because I don't know where you get your data from. I quickly and easily proved You didn't list all complex roundabouts. Since we all know you have the data, just provide the list.

You believe I have a secret list of crash rates for hundreds of complex roundabouts and I'm only listing the worst ones.  J&N, let me help you out.  I’m sure there is a developer out there that has built a grandiose 2x2 roundabout at the entrance of their subdivision.  Since a complex roundabout in the middle of a subdivision where drivers are already traveling at about 25 mph isn’t going to do much to enhance safety, it would be mainly for aesthetics.  Of course, don’t tell the IIHS that - the only non-interchange multi-lane roundabouts analyzed in their “national”  study were 3 multi-lane roundabouts along a 25 mph section of Avon Road in Colorado.  The point is if you found the grandiose subdivision entrance has a low crash rate, you could "prove" that all my data is biased.  To a rational person you wouldn’t have proven much, but at least you could convince yourself.  Come to think of it you could convince the IIHS pretty easily too.  They love focusing on the safety of complex roundabouts along 25 mph roads.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on December 29, 2017, 08:44:17 AM
The IIHS' bias, if any, does not justify your own.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 29, 2017, 08:52:38 AM
I don't need to show a single one...not that it matters because I don't know where you get your data from. I quickly and easily proved You didn't list all complex roundabouts. Since we all know you have the data, just provide the list.

You believe I have a secret list of crash rates for hundreds of complex roundabouts and I'm only listing the worst ones.  J&N, let me help you out.  I’m sure there is a developer out there that has built a grandiose 2x2 roundabout at the entrance of their subdivision.  Since a complex roundabout in the middle of a subdivision where drivers are already traveling at about 25 mph isn’t going to do much to enhance safety, it would be mainly for aesthetics.  Of course, don’t tell the IIHS that - the only non-interchange multi-lane roundabouts analyzed in their “national”  study were 3 multi-lane roundabouts along a 25 mph section of Avon Road in Colorado.  The point is if you found the grandiose subdivision entrance has a low crash rate, you could "prove" that all my data is biased.  To a rational person you wouldn’t have proven much, but at least you could convince yourself.  Come to think of it you could convince the IIHS pretty easily too.  They love focusing on the safety of complex roundabouts along 25 mph roads.

I already proved your data is biased by referring you to your own posting.  But since you don't have data for that particular roundabout (or so you claim), it was magically left off your list of ALL complex roundabouts from of all the states and provinces in America.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 29, 2017, 10:29:55 AM
If you remember my original query of roundabouts to analyze was based on a comment you had made.  This crash analysis of complex roundabouts is largely thanks to you J&N.

It would probably be fair to see a longer list, which will show both 100' diameter roundabouts that don't have high crash frequencies, and roundabouts with larger diameters and how they rank. 

Here is a list of 40 multi-lane roundabouts that I think could be meaningful to this conversation.  This was queried from a database of over 5,100 modern roundabouts.  This was the criteria used to query out the list:

-roundabouts constructed within the last 10 years
-all approaches have 2 entry lanes
-roundabouts have 4-legs
-main & side streets are major state or county routes (ie. likely high AADT roundabouts)
-interchange roundabouts (and frontage road roundabouts) not included

(https://image.ibb.co/kcS9pw/RBdata.png)

Now the hard part is finding accurate before/after crash data to make any type of analysis.  Here is a google KMZ file that includes the 40 roundabouts in the chart above:
http://www.mediafire.com/download/cd570rarros2c3g/Multi-Lane+Roundabouts+%28with+high+AADT%29.kmz

I queried out 40 roundabouts from a comprehensive database of over 5,100 roundabouts.  At the time, I readily acknowledged that the “hard part”  would be to find accurate before/after crash data for the list of roundabouts.  Now that original list has evolved to the Critical Crash Roundabouts posted above.  There are things you can criticize me on, but the list includes a large sample size of complex roundabouts and it pretty clearly shows they experience high crash rates.

But don't worry, even if there is a massive increase in crashes there will still be a reduction in injury crashes.  But what about the research that found a 6% increase in injury crashes at complex roundabouts in Minnesota?  And ignore the fact that the national IIHS study so often cited to make the claim that roundabouts reduce injury crashes by 76% is based on analyzing just 3 non-interchange multi-lane roundabouts in Colorado... built in 1997 or earlier... along a road signed for 25 mph... talk about a comprehensive "national" study.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 29, 2017, 11:14:21 AM
The IIHS' bias, if any, does not justify your own.
Too bad those agencies living on my tax dollars for supporting the road system -  FHWA and NYSDOT - don't bother presenting unbiased and complete dataset to clarify the issue.
While I am on the fence regarding FHWA capability of doing so, our state DOT - with at least one major roundabout being on independently compiled "most dangerous local intersections" list - would probably be unable to understand what we're talking about...
Title: Re: Crash prone 'modern roundabouts'
Post by: Hurricane Rex on December 30, 2017, 05:09:56 AM
If the IIHS was smart, they'd start a new study with different variables and at different speed limits.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 30, 2017, 07:58:15 AM
If the IIHS was smart, they'd start a new study with different variables and at different speed limits.
IIHS (like everyone else) also have their agenda. And it is not clear for me what drives their logic in different situations. For example, they are adamantly opposed to any speed limit increases or higher speeds on the roads - including support for automated speed enforcement. However it appears matter is far from black and white, and such adamant position doesn't mean advocating safety (but does mean advocating higher premiums - they are insurance institute, after all). Their research team is psychology-heavy, which makes some sense; and crash tests and related issues are a big part of their work. I am really not sure if traffic control is their strong point...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 30, 2017, 01:17:08 PM
^Apart from the RV blowing through the middle of that Worthington Minnesota roundabout, there has been two other pretty major events at the roundabout over the past couple weeks.

Tanker hauling cream overturns in Worthington roundabout
(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/111117.N.DG_.TANKERCREAM%20rgb_0.jpg?itok=rxMKiQ4I)
http://www.dglobe.com/news/accidents/4356792-tanker-hauling-cream-overturns-worthington-roundabout


These little piggies almost didn't make it to market when a Minn. hog truck rolled

(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/102817.N.DG_.ROLLOVER%203.jpg?itok=DOQatmVs)
http://www.agweek.com/news/4350581-these-little-piggies-almost-didnt-make-it-market-when-minn-hog-truck-rolled

Cream trucks rolling over, hogs running around the highway, some RV driver thinking they are Bo Duke... these roundabouts really give the good people of Worthington Minnesota something to talk about!


Another vehicle vaulted over the Worthington roundabout on Sunday.  The driver sustained non-life threatening injuries.  This comes a month after an RV was videotaped launching over the roundabout in early November.

Minivan vaults over roundabout Sunday
https://www.dglobe.com/news/accidents/4375814-minivan-vaults-over-roundabout-sunday

There have been 2 truck tip-over crashes, an RV flying through the middle of the roundabout captured on video, a driver sustaining non life-sustaining injuries after his min-van flew through the middle of the roundabout, and now 4 reported crashes over a few hour period on Friday.  The roundabouts are doing a stellar job at reducing crashes in Worthington.. or maybe they are doing a worthless job.

Snowpacked roundabouts result in four crashes reported Friday
https://www.dglobe.com/news/4380839-snowpacked-roundabouts-result-four-crashes-reported-friday
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on December 30, 2017, 01:38:14 PM
^Apart from the RV blowing through the middle of that Worthington Minnesota roundabout, there has been two other pretty major events at the roundabout over the past couple weeks.

Tanker hauling cream overturns in Worthington roundabout
(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/111117.N.DG_.TANKERCREAM%20rgb_0.jpg?itok=rxMKiQ4I)
http://www.dglobe.com/news/accidents/4356792-tanker-hauling-cream-overturns-worthington-roundabout


These little piggies almost didn't make it to market when a Minn. hog truck rolled

(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/102817.N.DG_.ROLLOVER%203.jpg?itok=DOQatmVs)
http://www.agweek.com/news/4350581-these-little-piggies-almost-didnt-make-it-market-when-minn-hog-truck-rolled

Cream trucks rolling over, hogs running around the highway, some RV driver thinking they are Bo Duke... these roundabouts really give the good people of Worthington Minnesota something to talk about!


Another vehicle vaulted over the Worthington roundabout on Sunday.  The driver sustained non-life threatening injuries.  This comes a month after an RV was videotaped launching over the roundabout in early November.

Minivan vaults over roundabout Sunday
https://www.dglobe.com/news/accidents/4375814-minivan-vaults-over-roundabout-sunday

There have been 2 truck tip-over crashes, an RV flying through the middle of the roundabout captured on video, a driver sustaining non life-sustaining injuries after his min-van flew through the middle of the roundabout, and now 4 reported crashes over a few hour period on Friday.  The roundabouts are doing a stellar job at reducing crashes in Worthington.. or maybe they are doing a worthless job.

Snowpacked roundabouts result in four crashes reported Friday
https://www.dglobe.com/news/4380839-snowpacked-roundabouts-result-four-crashes-reported-friday

Here's another crash.

   (https://youtu.be/tUYl1FqeBlA) [/URL]

SM-T230NU

Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 30, 2017, 01:44:15 PM
Here's another crash.

   (https://youtu.be/tUYl1FqeBlA) [/URL]

SM-T230NU

OK...but this has nothing to do with a roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on December 30, 2017, 01:49:32 PM
No, it has to do with showing random crashes that prove absolutely nothing about the engineering of an intersection.

SM-T230NU

Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 30, 2017, 02:10:43 PM
No, it has to do with showing random crashes that prove absolutely nothing about the engineering of an intersection.

SM-T230NU



Very true.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on December 30, 2017, 02:56:13 PM
snip

I don't think the idiocy of morons is enough to rule against the installation of roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 30, 2017, 03:10:00 PM
snip

I don't think the idiocy of morons is enough to rule against the installation of roundabouts.
Of course not. But when those morons have jobs in DOT and "certified engineer" seals, things become a bit worse.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on December 30, 2017, 03:25:25 PM
snip
I don't think the idiocy of morons is enough to rule against the installation of roundabouts.
Of course not. But when those morons have jobs in DOT and "certified engineer" seals, things become a bit worse.

Sure. Roundabouts get installed in the wrong places. I'll give you that, but it's the same with any traffic control device: it gets used and misused. What tradephoric argues is way over the line (not to mention cherry-picked) with what reality brings.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on December 30, 2017, 04:25:05 PM
If the IIHS was smart, they'd start a new study with different variables and at different speed limits.
IIHS (like everyone else) also have their agenda. And it is not clear for me what drives their logic in different situations. For example, they are adamantly opposed to any speed limit increases or higher speeds on the roads - including support for automated speed enforcement. However it appears matter is far from black and white, and such adamant position doesn't mean advocating safety (but does mean advocating higher premiums - they are insurance institute, after all). Their research team is psychology-heavy, which makes some sense; and crash tests and related issues are a big part of their work. I am really not sure if traffic control is their strong point...

Seems like they follow a pattern. IIHS is opposed to anything that increases speed. Higher speeds = greater risk of death. They're all about anything that lowers high-cost risks. High-speed roadways = higher insurance payouts. Similar with roundabouts. It takes a lot of PDO crashes to equal one fatality payout.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 30, 2017, 04:34:40 PM
Sure. Roundabouts get installed in the wrong places. I'll give you that, but it's the same with any traffic control device: it gets used and misused. What tradephoric argues is way over the line (not to mention cherry-picked) with what reality brings.

Roundabout proponents say that roundabouts reduce injury crashes by 76% but that just doesn't apply when looking at the crash statistics of complex 2x2 roundabouts.  That's the reality.  A large sample size of complex roundabouts in Minnesota found that there was a 6% increase in injury crashes... a lot different than a 76% reduction.  A lot of mindless people will continue to believe that roundabouts reduce injuries at these complex roundabouts simply because that is what the IIHS told us 17 years ago.  But how accurate is that IIHS study?  Of the 9 multi-lane roundabouts analyzed, 4 of them didn't even have before injury crash data to analyze.  The 5 remaining double-lane roundabouts with before/after injury crash data were all along a 2500 foot section of Avon Road in Avon, Colorado.  Good thing the "national" IIHS roundabout study determined the safety statistics of double-lane roundabouts in America based on a 2500 foot section of Avon Road in Colorado (signed for 25 mph).  GMAFB.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on December 30, 2017, 04:47:23 PM
Sure. Roundabouts get installed in the wrong places. I'll give you that, but it's the same with any traffic control device: it gets used and misused. What tradephoric argues is way over the line (not to mention cherry-picked) with what reality brings.
Roundabout proponents say that roundabouts reduce injury crashes by 76% but that just doesn't apply when looking at the crash statistics of complex 2x2 roundabouts.  That's the reality.  A large sample size of complex roundabouts in Minnesota found that there was a 6% increase in injury crashes... a lot different than a 76% reduction.  A lot of mindless people will continue to believe that roundabouts reduce injuries at these complex roundabouts simply because that is what the IIHS told us 17 years ago.  But how accurate is that IIHS study?  Of the 9 multi-lane roundabouts analyzed, 4 of them didn't even have before injury crash data to analyze.  The 5 remaining double-lane roundabouts with before/after injury crash data were all along a 2500 foot section of Avon Road in Avon, Colorado.  Good thing the "national" IIHS roundabout study determined the safety statistics of double-lane roundabouts in America based on a 2500 foot section of Avon Road in Colorado (signed for 25 mph).  GMAFB.

Well, good thing you simplified it for me! I'm clearly too stupid to figure it out on my own without your own complex analysis making it simple for me to understand!
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 30, 2017, 05:02:32 PM
Sure. Roundabouts get installed in the wrong places. I'll give you that, but it's the same with any traffic control device: it gets used and misused. What tradephoric argues is way over the line (not to mention cherry-picked) with what reality brings.

Roundabout proponents say that roundabouts reduce injury crashes by 76% but that just doesn't apply when looking at the crash statistics of complex 2x2 roundabouts.  That's the reality.  A large sample size of complex roundabouts in Minnesota found that there was a 6% increase in injury crashes... a lot different than a 76% reduction.  A lot of mindless people will continue to believe that roundabouts reduce injuries at these complex roundabouts simply because that is what the IIHS told us 17 years ago.  But how accurate is that IIHS study?  Of the 9 multi-lane roundabouts analyzed, 4 of them didn't even have before injury crash data to analyze.  The 5 remaining double-lane roundabouts with before/after injury crash data were all along a 2500 foot section of Avon Road in Avon, Colorado.  Good thing the "national" IIHS roundabout study determined the safety statistics of double-lane roundabouts in America based on a 2500 foot section of Avon Road in Colorado (signed for 25 mph).  GMAFB.

You complain about a national study consisting of limited data in Colorado, then argue that against your national study consisting of limited data in Minnesota.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 30, 2017, 05:28:35 PM
^I understand the point you are making J&N.  But the Minnesota research analyzes 3X more complex roundabouts than the IIHS study.  Also, the Minnesota research analyzes complex roundabouts on roadways with higher than 25 mph speed limits.  Not to mention the Minnesota research isn't analyzing crash data from the previous century.  And the Minnesota study does exactly what it claims.. it analyzes roundabouts in the state of Minnesota.  I'm not going to fault Minnesota for not analyzing double-lane roundabouts in Texas.  OTOH, the national IIHS study only analyzes double-lane roundabouts in Colorado.  Unless if we are living in the United States of Colorado, that doesn't sound too national to me.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 30, 2017, 05:39:18 PM
snip
I don't think the idiocy of morons is enough to rule against the installation of roundabouts.
Of course not. But when those morons have jobs in DOT and "certified engineer" seals, things become a bit worse.

Sure. Roundabouts get installed in the wrong places. I'll give you that, but it's the same with any traffic control device: it gets used and misused. What tradephoric argues is way over the line (not to mention cherry-picked) with what reality brings.
Yes, and you don't want to give complex tool to morons. They - at least at NYSDOT - struggle with regular traffic lights, and fail at synchronized traffic light stage.
Roundabouts are complex devices which need to be used with some understanding - which is currently missing. You end up with wrong people using wrong kind of stuff - and being perfectly happy about results.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 30, 2017, 06:38:14 PM
Roundabouts are complex devices

Just the geometry, really.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 30, 2017, 06:50:35 PM
Roundabouts are complex devices

Just the geometry, really.
Sure, just the geometry. But many geometrical problems are more difficult that they sound. Classic ones - squaring the circle, doubling the cube - are plainly unsolvable..
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on December 30, 2017, 07:55:49 PM
Roundabouts are complex devices
Just the geometry, really.
Classic ones - squaring the circle

Isn't that what we're doing with roundabouts? :bigass:
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 30, 2017, 08:01:21 PM
Roundabouts are complex devices
Just the geometry, really.
Classic ones - squaring the circle

Isn't that what we're doing with roundabouts? :bigass:
Sure, that is called one-way streets... Look at NYC, downtown manhattan is a bunch of squared and packed, traffic light controlled roundabouts...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 30, 2017, 09:53:12 PM
In the 1950s, the City of Edmonton, Alberta built 12, two-lane traffic circles along major arterial roads. Seven were subsequently replaced with intersections (two with grade-separated junctions) but five remain, mostly untouched (except for modern markings). Lucky for us, the city compiles their crash data throughout the year, and puts it into a report (read here (https://www.edmonton.ca/transportation/RoadsTraffic/2016MVCAnnualReportsm.pdf)). Here are the top ten intersections in the city for number of collisions:

1) 107 Ave @ 142 St (a traffic circle) -- 134
2) Yellowhead Trail @ 127 St -- 83
3) Yellowhead Trail @ 149 St -- 76
4) Yellowhead Trail @ 121 St -- 72
5) 118 Ave @ Groat Road (a signalised, squared-off traffic circle -- see below) -- 62
6) 34 Ave @ Calgary Trail (NB) -- 60
7) 167 Ave @ 97 St -- 58
8) 34 Ave @ 91 St -- 58
9) 137 Ave @ 97 St -- 57
10) 34 Ave @ Calgary Trail (SB) -- 56

Of the 23,139 collisions in the city in 2016, the top causes of collisions were following too closely (38.6%, 8,928 collisions); struck parked vehicle (13.0%, 3,019); changing lanes improperly (10.8%, 2,497); left turn across path (6.9%, 1,593); and ran off road (6.4%, 1,483).

Interestingly, only two of the original five traffic circles in the city make the top ten. The rest are all (what I assume to be) very high-volume signalised intersections. Though it's possible the other three traffic circles make up spots 11-13.

Number 5 on the list above is a signalised, squared-off traffic circle (https://goo.gl/BLK3vM). There's no way to know what's causing the collisions at this intersection, nor what the numbers were prior to signalisation, but it still doesn't seem to be performing that well, even with the decidedly square layout.

(https://i.imgur.com/GtvcI54.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 03, 2018, 10:43:04 AM
^Good info Jake.  By far the most crash prone intersection in Edmonton is the un-signalized 2x2 traffic circle at 107 Ave & 142 Street.  It experienced 134 crashes in 2016, a full 51 more crashes than the next crash prone intersection in the city.  Edmonton drivers have had 50 years to learn how to drive through the traffic circle, and it still experienced well over 100 crashes in 2016.  Here is GE imagery of the #1 and #2 most crash prone intersections in Edmonton:
 
#1: 132 crashes (107 @ 142 St) traffic circle: 
https://www.google.com/maps/@53.5510288,-113.5656331,265m/data=!3m1!1e3

#2: 83 crashes (Yellowhead Trail @ 127 St) signalized intersection: 
https://www.google.com/maps/@53.5807075,-113.5412952,229m/data=!3m1!1e3

(https://i.imgur.com/GtvcI54.png)

Regards to 118 Ave & Groat Rd, the squared off corners makes it resemble a Town Center Intersection to me.  However, it’s a very tight TCI and the curves through the intersection may be leading to increases in crashes.  Of course 62 crashes is a lot less than 134 crashes.... 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 03, 2018, 02:55:10 PM
Seems like they follow a pattern. IIHS is opposed to anything that increases speed. Higher speeds = greater risk of death. They're all about anything that lowers high-cost risks. High-speed roadways = higher insurance payouts. Similar with roundabouts. It takes a lot of PDO crashes to equal one fatality payout.

If we use FHWA’s comprehensive crash costs by injury severity level, the social costs of a fatal crash is estimated to be $4,008,900 and the cost of a PDO crash is $7,400.  It would take 541 PDO crashes to equal the cost of 1 fatal crash.  But what we aren’t considering is the probability of a fatal crash at an intersection.  The FHWA reported there were 2,924 fatal crashes at the roughly 300,000 signalized intersections in 2007.  Extrapolating those numbers, the average signalized intersection in America averages a fatal crash about every 100 years.  Looking at a more localized example, the top 20 most crash prone intersections in SE Michigan experienced 3 fatalities over the past 10 years.  Extrapolating those numbers, that equates to a fatality every 66.7 years (200 years of crash data / 3 fatalities).   Let’s assume a signalized intersection averages a fatal crash every 50 years.  The average “fatal”  payout per year would be $4,008,900/50 years… or $80,178.  Now it only takes 11 PDO crashes at $7,400 a pop to equal the average “fatal”  crash payout. 

When doing a cost/benefit analysis for the 2x2 roundabouts analyzed in the Minnesota study, the 2x2 roundabouts have a higher crash cost than the signalized intersections they replaced (by $1,664,300).  Remember it only takes 11 PDO crashes to equal the average "fatal" crash payout, yet the roundabouts in Minnesota had a whopping 270 more PDO crashes.

MnDOT releases a detailed study claiming massive decreases in both fatal and non-fatal incidents at intersections where roundabouts have been installed (this includes both state and non-state-built projects).

http://www.dot.state.mn.us/trafficeng/safety/docs/roundaboutstudy.pdf

There were 6 full dual-lane roundabouts analyzed in that Minnesota study (ie. 2x2 roundabouts).  Here is a table of the dual-lane roundabouts with before construction and after construction crash data based on crash severity:

(https://i.imgur.com/D77VC6z.png)

If we use FHWA’s comprehensive crash costs by injury severity level to perform a cost/benefit analysis, we see that these dual-lane Minnesota roundabouts increased crash costs by $1,664,300.  Even though there were 3 less A-level crashes at the roundabouts, there were 7 more C-level crashes and a whopping 270 more PDO crashes.

BEFORE ROUNDABOUT CRASH COSTS = $4,882,600
Fatality (K)           0 X $4,008,900 = $0
Disabling Injury (A)   3 X  $216,000 = $648,000
Evident Injury (B)   15 X $79,000 = $1,185,000
Possible Injury (C)   46 X $44,900 = $2,065,400
PDO (O)          133 X $7,400 =  $984,200

AFTER ROUNDABOUT CRASH COSTS = $6,546,900
Fatality (K)           0 X $4,008,900 = $0
Disabling Injury (A)   0 X  $216,000 = $0
Evident Injury (B)   15 X $79,000 = $1,185,000
Possible Injury (C)   53 X $44,900 = $2,379,700
PDO (O)          403 X $7,400 =  $2,982,200

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 05, 2018, 12:05:48 PM
News reports for fatal roundabout crashes that occurred in 2017. 

http://www.sun-sentinel.com/local/broward/fl-boca-man-dies-in-parkland-crash-20170117-story.html
http://www.theledger.com/news/20170208/teen-faces-manslaughter-charge-after-girl-dies-in-crash-following-chase-with-lpd-officer
http://www.wdbj7.com/content/news/60-year-old-Roanoke-County-woman-dies-in-motorcycle-crash-413537653.html
http://www.fox9.com/news/unbelted-man-dies-in-chisago-county-crash-friday-afternoon
http://www.wcsh6.com/news/local/fatal-crash-closes-rte-114-bypass-in-gorham/433810393
http://www.toledoblade.com/Police-Fire/2017/04/30/Alcohol-believed-to-be-factor-in-fatal-Springfield-Twp-crash.html
http://www.gainesville.com/news/20170502/roundabout-crash-kills-two-police-say
http://www.bellinghamherald.com/news/local/article153269789.html
http://www.cecildaily.com/police_and_fire_beat/article_bed6099c-45a6-5be5-b61d-ec91d893631b.html
http://www.wpta21.com/story/35827071/coroner-identifies-motorcyclist-involved-in-thursday-morning-fatal-crash
http://www.prescottenews.com/index.php/news/current-news/item/30613-37-year-old-man-from-page-dies-in-crash-at-roundabout
http://www.startribune.com/driver-in-st-cloud-roundabout-fatally-hits-pedestrian/453113583/
http://www.lasvegasnow.com/news/one-killed-in-overnight-crash/859083995

This was based on about an hour of google searches and based on this limited research, there were at least 13 fatal roundabouts crashes in 2017 resulting in 14 fatalities.   According to the latest 2013 FHWA estimates, there are roughly 3200 roundabouts in the United States.  I personally have compiled a database of over 5200 roundabouts in America, but I don’t know the exact methodology used to compile the FHWA database.  Let’s split the difference and say there are about 4200 roundabouts in America.   In 2017 each modern roundabout averaged 0.0033 fatal crashes (14 fatalities / 4200 roundabouts).  This ratio is comparable to previous years based on data compiled by the FHWA:
(https://i.imgur.com/6lWCWUu.png)
https://safety.fhwa.dot.gov/intersection/innovative/roundabouts/docs/fhwasa15072.pdf

So how does this ratio compare to signalized intersections?  Based on FHWA data there were 2,924 fatalities at approximately 311,000 signalized intersections in 2007.  Each signal averaged 0.0094 fatal crashes (2,924 fatalities / 311,000 signals). 
https://safety.fhwa.dot.gov/intersection/other_topics/fhwasa10005/brief_2.cfm

Now we can use these ratios to get a sense of how much roundabouts are reducing fatal crashes.  Is it really 90% as the IIHS claims?  To me it looks to be closer to 65% (1-(0.0033/0.0094)).  That’s still a big reduction, but it's not 90%.  And consider that the IIHS claims that roundabouts reduce injury crashes by 76%.  However, Minnesota research found that complex roundabouts in that state actually saw a 6% increase in injury crashes.  The point is there is potentially a subset of modern roundabouts that are increasing fatal crashes, not reducing them.  I'll tell you one subset of roundabouts that are potentially increasing fatal crashes... roundabouts that have retaining walls in the central island.  Do you think it's a coincidence there have been 3 fatalities in the past 10 years at the 96th and Westfield Blvd roundabout in Carmel?  Every time a driver misjudges the roundabout and drive through the middle of it, they smack into a concrete wall.  Boom!  Dead!
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on January 05, 2018, 08:51:12 PM
Stop blaming the roundabout and start blaming the person driving drunk at high speed.  The Carmel roundabouts have been a wonderful improvement to traffic flow in the area.   A driver going far in excess of speed limits and driving impaired is not an indictment of the roundabout, it's a failure of personal responsibility.  Get over it.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 06, 2018, 03:32:11 AM
Stop blaming the roundabout and start blaming the person driving drunk at high speed.  The Carmel roundabouts have been a wonderful improvement to traffic flow in the area.   A driver going far in excess of speed limits and driving impaired is not an indictment of the roundabout, it's a failure of personal responsibility.  Get over it.

While that's true, and I largely agree that personal responsibility is the problem, we (as a society) have a responsibility to create an environment whereby screwing up doesn't kill you. Roundabouts are great, as long as everyone is looking at the road, and no one has any health problems. But, we both know that both of those things aren't the reality. So, we shouldn't be creating an environment where these things, combined with the operation of a motor vehicle, create a dangerous situation.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on January 06, 2018, 08:35:01 PM
Based on the Google Maps measurement tool, the retaining wall is a full 45 feet away from the inner curb of the roundabout.   The probability of screwing up and ending up against the retaining wall at normal speeds is extremely unlikely.  (The posted warning sign has an advisory speed of 15 mph, even at double that speed you would have to really work at it to end up in the center of the roundabout.  At least one of the fatal crashes that he quotes involved an intoxicated driver at extremely high speeds.  Normal drivers are not as risk here. 

https://www.google.com/maps/@39.9280968,-86.1268644,3a,75y,183.26h,90.9t/data=!3m6!1e1!3m4!1sZtBXbeeSszxK9vR7zeH4Vg!2e0!7i13312!8i6656
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 08, 2018, 12:19:34 PM
Stop blaming the roundabout and start blaming the person driving drunk at high speed.  The Carmel roundabouts have been a wonderful improvement to traffic flow in the area.   A driver going far in excess of speed limits and driving impaired is not an indictment of the roundabout, it's a failure of personal responsibility.  Get over it.

According to Jim Brainard, if you straightened all of the roundabouts in Carmel and strung them together, you’d have to drive about 10 ½ miles to reach the end…. or a little over 4 laps around Indianapolis Motor Speedway.  That’s 10 ½ miles where drivers are not traveling in a straight line to get to their destination.  Also, according to the IIHS drivers encountering a roundabout are FORCED to slow down.  So even if nobody else is in the roundabout, Carmel drivers are guaranteed to experience several seconds of delays as they slow down to traverse the circle.  And we aren’t even considering the “problem”  roundabouts that can take several minutes to traverse during rush hour.  CJW is conveniently ignoring those.  Drivers collectively driving 10 ½ miles out of their way… guaranteed delays at every roundabout drivers traverse… that doesn’t sound like improved traffic flow. 

To be honest, I’m sure there was an improvement in traffic flow in Carmel after the roundabouts were built.   But could that be because the intersections the roundabouts replaced were woefully inadequate to carry the capacity of a ballooning Carmel population?  Here are some before/after pictures of roundabout location in Carmel.  Not surprising traffic flow improved when you compare these pictures… not to mention the fact the two major surface streets in Carmel were converted to grade-separated freeways over the past decade.

(https://i.imgur.com/14wCyqy.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 08, 2018, 01:48:56 PM
Stop blaming the roundabout and start blaming the person driving drunk at high speed.  The Carmel roundabouts have been a wonderful improvement to traffic flow in the area.   A driver going far in excess of speed limits and driving impaired is not an indictment of the roundabout, it's a failure of personal responsibility.  Get over it.

According to Jim Brainard, if you straightened all of the roundabouts in Carmel and strung them together, you’d have to drive about 10 ½ miles to reach the end…. or a little over 4 laps around Indianapolis Motor Speedway.  That’s 10 ½ miles where drivers are not traveling in a straight line to get to their destination.  Also, according to the IIHS drivers encountering a roundabout are FORCED to slow down.  So even if nobody else is in the roundabout, Carmel drivers are guaranteed to experience several seconds of delays as they slow down to traverse the circle.  And we aren’t even considering the “problem” roundabouts that can take several minutes to traverse during rush hour.  CJW is conveniently ignoring those.  Drivers collectively driving 10 ½ miles out of their way… guaranteed delays at every roundabout drivers traverse… that doesn’t sound like improved traffic flow. 

To be honest, I’m sure there was an improvement in traffic flow in Carmel after the roundabouts were built.   But could that be because the intersections the roundabouts replaced were woefully inadequate to carry the capacity of a ballooning Carmel population?  Here are some before/after pictures of roundabout location in Carmel.  Not surprising traffic flow improved when you compare these pictures… not to mention the fact the two major surface streets in Carmel were converted to grade-separated freeways over the past decade.

And here you're not quite right. Roundabouts should be compared not with straight road, but either with 4-way stops or traffic signals. Both of those options include delays. You may include grade separated intersections as a no-delay option, but then you're talking about entirely different price range.

And yes, throughput of roundabouts at high traffic rate are yet another question waiting to be addressed.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 08, 2018, 03:19:23 PM
we (as a society) have a responsibility to create an environment whereby screwing up doesn't kill you.

Disagree.

I'd say we as a society have a responsibility to create an environment in which people don't assume that screwing up won't kill them.



Roundabouts should be compared ... with 4-way stops or traffic signals. Both of those options include delays.

Agree.

And yes, throughput of roundabouts at high traffic rate are yet another question waiting to be addressed.

Also agree.
Title: Re: Crash prone 'modern roundabouts'
Post by: intelati49 on January 08, 2018, 03:37:11 PM
we (as a society) have a responsibility to create an environment whereby screwing up doesn't kill you.

Disagree.

I'd say we as a society have a responsibility to create an environment in which people don't assume that screwing up won't kill them.



Roundabouts should be compared ... with 4-way stops or traffic signals. Both of those options include delays.

Agree.

And yes, throughput of roundabouts at high traffic rate are yet another question waiting to be addressed.

Also agree.

I'll take the middle road (heh, unintentional) on this one. Yes, having a concrete wall unprotected in the middle of the road is dumb. :banghead: But no, if you have good signage and clear sightlines it isn't much of a problem. (Don't have a reference to check the clear space numbers.)

Yes

Yes

I love this topic from a theoretical standpoint, but not every rollover crash and accident is a mark on roundabouts in general. The rash of crashes after the construction should be grounds for the engineer to go "Whoa, hold up, what's going on." Just don't call for the removal of everything at once. :pan:
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 08, 2018, 03:44:50 PM

I love this topic from a theoretical standpoint, but not every rollover crash and accident is a mark on roundabouts in general. The rash of crashes after the construction should be grounds for the engineer to go "Whoa, hold up, what's going on." Just don't call for the removal of everything at once. :pan:
Another way of looking at it (and it is called "statistics") is to assume that shit happens, and crashes -  horrible or mundane - can happen at any point of the road, and are even more likely at the intersection.
However if some of those locations (or type of locations) stands out in terms of number of events, then...
Title: Re: Crash prone 'modern roundabouts'
Post by: intelati49 on January 08, 2018, 03:54:49 PM

I love this topic from a theoretical standpoint, but not every rollover crash and accident is a mark on roundabouts in general. The rash of crashes after the construction should be grounds for the engineer to go "Whoa, hold up, what's going on." Just don't call for the removal of everything at once. :pan:
Another way of looking at it (and it is called "statistics") is to assume that shit happens, and crashes -  horrible or mundane - can happen at any point of the road, and are even more likely at the intersection.
However if some of those locations (or type of locations) stands out in terms of number of events, then...

Quote
Whoa, hold up

Get more data and start looking at it.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 08, 2018, 05:30:48 PM
I love this topic from a theoretical standpoint, but not every rollover crash and accident is a mark on roundabouts in general.

When you crash head on into a retaining wall at 62 mph you are pretty much a goner - which is the circumstances behind the 2007 double-fatality crash at the 96th and Westfield roundabout.  At least you can survive a spectacular rollover crash.  Case in point watch this video of 100 spectacular NASCAR flips.  All of these drivers have one thing in common… they walked away from the crash.  And a lot of these crashes were from the early days of NASCAR where safety wasn’t where it is today.

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 08, 2018, 06:51:40 PM
I love this topic from a theoretical standpoint, but not every rollover crash and accident is a mark on roundabouts in general.

When you crash head on into a retaining wall at 62 mph you are pretty much a goner - which is the circumstances behind the 2007 double-fatality crash at the 96th and Westfield roundabout.  At least you can survive a spectacular rollover crash.  Case in point watch this video of 100 spectacular NASCAR flips.  All of these drivers have one thing in common… they walked away from the crash.  And a lot of these crashes were from the early days of NASCAR where safety wasn’t where it is today.
If you enter an traffic light controlled intersection at 62 MPH at a wrong time and live to tell that story - you may also buy a couple of lottery tickets.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 09, 2018, 02:54:38 AM
we (as a society) have a responsibility to create an environment whereby screwing up doesn't kill you.

Disagree.

I'd say we as a society have a responsibility to create an environment in which people don't assume that screwing up won't kill them.

I think both go hand in hand. Improve driver confidence by creating a safer environment.

Of course, I wish that weren't true. I'd rather drivers were confident because they were well-taught, but the US seems incapable of implementing even a slightly difficult driving exam.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 09, 2018, 10:09:41 AM
$1.1M project will change crash-prone Lee Road roundabout
(https://www.gannett-cdn.com/-mm-/61725f1fcb90c33af9f292aa68f9a0b9d628a8c4/c=1-0-851-639&r=x408&c=540x405/local/-/media/2016/06/09/MIGroup/Livingston/636010728590503440-Option-2.jpg)
A rendering GHD Incorporated created for the Livingston County Road Commission shows how the roundabout at Lee and Whitmore Lake roads in Green Oak Township will be reduced from three lanes to two lanes. (Photo: Submitted)

Quote
“We need to reduce the number of conflict points where people wander into other lanes and make quick adjustments inside the roundabout, because people turning from the wrong lane causes the majority of the crashes,”  Livingston County Road Commission Manager Mike Craine said.

Quote
"We are also improving pavement markings and signs, because it's a little confusing," Craine said.

Quote
“Most of the crashes on Lee Road happen in this roundabout, usually between 40 to 60 a year,”  traffic and safety engineer Mike Goryl said. “More lanes means more problems. Across the state, when you have three lanes in a roundabout, we see similar crash patterns.”

http://www.livingstondaily.com/story/news/local/community/livingston-county/2018/01/08/1-1-m-project-change-crash-prone-lee-road-shrinking-3-lane-roundabout-lee-road-reduce-crashes-confus/988173001/

Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on January 09, 2018, 10:19:34 AM
we (as a society) have a responsibility to create an environment whereby screwing up doesn't kill you.

Disagree.

I'd say we as a society have a responsibility to create an environment in which people don't assume that screwing up won't kill them.

I think both go hand in hand. Improve driver confidence by creating a safer environment.

Of course, I wish that weren't true. I'd rather drivers were confident because they were well-taught, but the US seems incapable of implementing even a slightly difficult driving exam.

The US has done a lot to eliminate distractions, including limiting the number of people permitted in a car with a new driver, longer probationary periods, etc.

But, if a 16 year old is taught to stop before entering the highway, immediately get in the left lane going 20 below the limit, or they don't have to slow down at a yield sign, they're still not going to be good drivers.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 09, 2018, 02:04:41 PM
I love this topic from a theoretical standpoint, but not every rollover crash and accident is a mark on roundabouts in general.

When you crash head on into a retaining wall at 62 mph you are pretty much a goner - which is the circumstances behind the 2007 double-fatality crash at the 96th and Westfield roundabout.  At least you can survive a spectacular rollover crash.  Case in point watch this video of 100 spectacular NASCAR flips.  All of these drivers have one thing in common… they walked away from the crash.  And a lot of these crashes were from the early days of NASCAR where safety wasn’t where it is today.
If you enter an traffic light controlled intersection at 62 MPH at a wrong time and live to tell that story - you may also buy a couple of lottery tickets.

But the probability of entering a traffic light-controlled intersection at a wrong time is less than 100%.  The point is that the probability or hitting a retaining wall at a wrong time is exactly 100%.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 09, 2018, 04:03:53 PM
I love this topic from a theoretical standpoint, but not every rollover crash and accident is a mark on roundabouts in general.

When you crash head on into a retaining wall at 62 mph you are pretty much a goner - which is the circumstances behind the 2007 double-fatality crash at the 96th and Westfield roundabout.  At least you can survive a spectacular rollover crash.  Case in point watch this video of 100 spectacular NASCAR flips.  All of these drivers have one thing in common… they walked away from the crash.  And a lot of these crashes were from the early days of NASCAR where safety wasn’t where it is today.
If you enter an traffic light controlled intersection at 62 MPH at a wrong time and live to tell that story - you may also buy a couple of lottery tickets.

But the probability of entering a traffic light-controlled intersection at a wrong time is less than 100%.  The point is that the probability or hitting a retaining wall at a wrong time is exactly 100%.

My message is somewhat different - sometimes you cannot avoid a problem when someone is determined to get into trouble. As someone said,
 
Quote
... a race between engineers striving to build bigger and better idiot-proof things, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning.
Sometimes you cannot avoid a problem when someone is determined to get into trouble. But minimizing consequences is another possible strategy. No need to put a hard stop where it is less than needed, but sometimes running against concrete wall is better than flying over the edge into an abyss.
Roundabouts with all their "calming"  approaches, "visibility control", etc do not have room for adjustments and they remove many traditional hints for drivers helping them to become idiots. In other words, sometimes universe wins by coming up with idiots in engineering positions.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 10, 2018, 09:02:58 PM
^^
Laughs aside, he's (Jim Brainard) basically dictator of the public works department in Carmel, IN. There's very little free thinking in that office, me thinks.

Wow you aren't kidding about not much free thinking.  A Carmel city counsel meeting has recently surfaced on youtube.

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 10, 2018, 10:10:43 PM
^^
Laughs aside, he's (Jim Brainard) basically dictator of the public works department in Carmel, IN. There's very little free thinking in that office, me thinks.

Wow you aren't kidding about not much free thinking.  A Carmel city counsel meeting has recently surfaced on youtube.

https://youtu.be/a3Cla9t9UZk

HA! Credit where credit's due...that's hilarious. :-D Probably accurate too.
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on January 10, 2018, 10:48:45 PM
I would be interested in a brief summary of what, exactly, has kept this thread going for over 60 pages.
It's not a bad topic, but after a while, you'd have to start going in circles  :-D
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 11, 2018, 12:27:46 AM
I would be interested in a brief summary of what, exactly, has kept this thread going for over 60 pages.
It's not a bad topic, but after a while, you'd have to start going in circles  :-D

We do start to go in circles, but each time we do, some new piece of information comes up, or one of us changes their mind about something, etc. Keeps the conversation going.

Personally, in the roadgeek spectrum, traffic control is my main interest, so naturally, I could endlessly debate the pros and cons of roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on January 11, 2018, 12:59:35 AM
I would be interested in a brief summary of what, exactly, has kept this thread going for over 60 pages.
It's not a bad topic, but after a while, you'd have to start going in circles  :-D

Some think roundabouts are evil and all should be tore out asap. Some think engineers who design them should lose their license to practice. Some think roundabouts are the only intersection control device modern traffic engineers/DOTs will consider. Some multilane roundabouts have seen a sharp increase in minor injury/fender-bender crashes for various reasons, including but not limited to: poor geometric design, improper signing/marking, over-designed/under-capacity (too many lanes), poor driving habits, lax driver education, too many drunks. Fatalities have occurred, but the overwhelming majority have been attributed to OWI, operating too fast, or a fixed object in the central island. For the past several (tens of?) pages, the only new "information" being posted in this thread is another report of a crash at a roundabout.

I think that about sums it up.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on January 11, 2018, 07:05:58 AM
I would be interested in a brief summary of what, exactly, has kept this thread going for over 60 pages.
It's not a bad topic, but after a while, you'd have to start going in circles  :-D

Tradephoric hates multi-lane roundabouts.

Kalvado hates all roundabouts.

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 11, 2018, 08:03:44 AM

Kalvado hates all roundabouts.
You're cutting a corner here.
Kalvado hates, when things are done just for sake of doing it "cool" without understanding. Most roundabouts I saw are built because they are cool, without underlying understanding. Hence...
 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 11, 2018, 11:23:32 AM
I would be interested in a brief summary of what, exactly, has kept this thread going for over 60 pages.
It's not a bad topic, but after a while, you'd have to start going in circles  :-D

Simple really.  Agencies continue to build complex modern roundabouts.  As long as agencies continue to build them there will inevitably be more crash prone modern-roundabouts to cite.  To the chagrin of DaBigE, I’ll continue to cite them.  Maybe if a roundabout hits 1,000 crashes in a year, people will finally start to question if these roundabouts are working. To get that number of crashes, they would probably have to design a 4x3 roundabout… but knowing the ignorance of these agencies they might just try to do it.  It will be the most crash prone intersection in the world, yet they will be claiming how safe it is! 
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on January 11, 2018, 12:06:38 PM
After a while, you'd have to start going in circles  :-D
We do start to go in circles, but each time we do, some new piece of information comes up, or one of us changes their mind about something, etc. Keeps the conversation going.

Good response to a good pun :D
How, then, does reading this thread compare to continuously circling a roundabout?


Simple really.  Agencies continue to build complex modern roundabouts.  As long as agencies continue to build them there will inevitably be more crash prone modern-roundabouts to cite.  To the chagrin of DaBigE, I’ll continue to cite them.  Maybe if a roundabout hits 1,000 crashes in a year, people will finally start to question if these roundabouts are working. To get that number of crashes, they would probably have to design a 4x3 roundabout… but knowing the ignorance of these agencies they might just try to do it.  It will be the most crash prone intersection in the world, yet they will be claiming how safe it is! 


Are all of your 1300 posts in this thread? It is theoretically possible, since there are 1600 replies  :D

Though multi-lane roundabouts can be annoying due to driver ignorance and hesitation, I fail to see how they are, functionally, any different from a standard one-lane roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on January 11, 2018, 12:35:51 PM
I fail to see how they are, functionally, any different from a standard one-lane roundabout.

I suspect you will learn, here, within the next day.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 11, 2018, 12:46:45 PM

Though multi-lane roundabouts can be annoying due to driver ignorance and hesitation
Quote
Age: 18
I hate to ask, but how long do you have your license, Mr. Experienced Driver?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 11, 2018, 01:52:45 PM
Are all of your 1300 posts in this thread? It is theoretically possible, since there are 1600 replies  :D

Though multi-lane roundabouts can be annoying due to driver ignorance and hesitation, I fail to see how they are, functionally, any different from a standard one-lane roundabout.

Some people here are fascinated with control cities and sign shields.  Those threads aren't for me but i don't go out of my way to post on them saying i wish they would stop talking about those things.  It doesn't matter to me.  Yet i post some roundabout crash results and some people seem to get extremely defensive. 

In general, multi-lane roundabouts have higher crash rates than single-lane roundabouts.  There are a lot of explanations as to why this is the case, but quite simply there are more ways for drivers to screw up at multi-lane roundabouts (especially multi-lane roundabouts with 2x2 geometries).  I am also concerned about single-lane roundabouts that have fixed objects in the central island.  My belief is that roundabouts (whether single or double lane) should be designed with the assumption that drivers will blow through the middle of it.   This is an especially important consideration at suburban and/or rural roundabouts where link speeds are generally higher.
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on January 11, 2018, 02:26:07 PM
I fail to see how they are, functionally, any different from a standard one-lane roundabout.
I suspect you will learn, here, within the next day.

Smart thing to suspect. In fact, that's part of the reason I made that statement  :D

Though multi-lane roundabouts can be annoying due to driver ignorance and hesitation
Quote
Age: 18
I hate to ask, but how long do you have your license, Mr. Experienced Driver?

15 months, to be exact. I'm not calling myself experienced by any stretch of the imagination; however it is possible to by annoyed (and rightly so) when you are not the driver yourself. This roundabout in particular (https://www.google.com/maps/@43.0814207,-79.0506355,16.75z) I travel through frequently and find myself annoyed with traffic flow on the approach, even from the backseat.

I should also add that despite my inexperience, I am a roadgeek, after all, and just may know more about roundabouts than some supposedly more seasoned drivers (though still less so than others here).
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 11, 2018, 02:27:55 PM
Though multi-lane roundabouts can be annoying due to driver ignorance and hesitation, I fail to see how they are, functionally, any different from a standard one-lane roundabout.

I used to think that too.  However, I figured out a functional difference several months ago.  All of a single-lane roundabout's conflict points are side-swipe, the result of merging into a lane where there's already a car.  However, in a multi-lane roundabout, straight-through traffic can actually conflict in a more catastrophic way.

In order to avoid the green star conflict point illustrated below, the right lane of the approaches would need to be right-turn-only–effectively making it a single-lane roundabout with slip lanes.

(https://i.imgur.com/SLCiqgK.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 11, 2018, 02:46:07 PM
Though multi-lane roundabouts can be annoying due to driver ignorance and hesitation, I fail to see how they are, functionally, any different from a standard one-lane roundabout.

I used to think that too.  However, I figured out a functional difference several months ago.  All of a single-lane roundabout's conflict points are side-swipe, the result of merging into a lane where there's already a car.  However, in a multi-lane roundabout, straight-through traffic can actually conflict in a more catastrophic way.

In order to avoid the green star conflict point illustrated below, the right lane of the approaches would need to be right-turn-only–effectively making it a single-lane roundabout with slip lanes.


This is still a low-angle conflict, not exactly sidesweep - but closer to sidesweep than to right angle or head-on.
Bigger problem here is that driver of "blue" car has potential conflict with cars on multipe different trajectories - both lanes on the left (but maybe lower lane turns right), and car  continuing on the circle. While still making sure conflicting traffic from the right actually yields, and there is no pedestrian or bicycle.
Hazard wise, this is a RTOR into the third lane on the regular intersection. .
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 11, 2018, 02:56:47 PM
Though multi-lane roundabouts can be annoying due to driver ignorance and hesitation
Quote
Age: 18
I hate to ask, but how long do you have your license, Mr. Experienced Driver?

15 months, to be exact. I'm not calling myself experienced by any stretch of the imagination; however it is possible to by annoyed (and rightly so) when you are not the driver yourself. This roundabout in particular (https://www.google.com/maps/@43.0814207,-79.0506355,16.75z) I travel through frequently and find myself annoyed with traffic flow on the approach, even from the backseat.

I should also add that despite my inexperience, I am a roadgeek, after all, and just may know more about roundabouts than some supposedly more seasoned drivers (though still less so than others here).
Did it ever occur to you that if specific structure causes more problems than others, it may be problem of the structure?
I understand it is easy to blame others while considering yourself a much better driver - especially from the backseat. But, as some wise guy told me when I was learning to drive: "always remember that you're not the only idiot on this road"
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on January 11, 2018, 03:17:40 PM
Though multi-lane roundabouts can be annoying due to driver ignorance and hesitation
Quote
Age: 18
I hate to ask, but how long do you have your license, Mr. Experienced Driver?

15 months, to be exact. I'm not calling myself experienced by any stretch of the imagination; however it is possible to by annoyed (and rightly so) when you are not the driver yourself. This roundabout in particular (https://www.google.com/maps/@43.0814207,-79.0506355,16.75z) I travel through frequently and find myself annoyed with traffic flow on the approach, even from the backseat.

I should also add that despite my inexperience, I am a roadgeek, after all, and just may know more about roundabouts than some supposedly more seasoned drivers (though still less so than others here).
Did it ever occur to you that if specific structure causes more problems than others, it may be problem of the structure?
I understand it is easy to blame others while considering yourself a much better driver - especially from the backseat. But, as some wise guy told me when I was learning to drive: "always remember that you're not the only idiot on this road"

Well, while Trade tends to be very specific in the roundabouts he identifies as being problematic, you tend to treat them all as bad guys.  If one has a problem, they al don't necessarily have a problem.

And web's age shouldn't have anything to do with it, because it's not just 18 year olds getting into accidents in roundabouts. If someone gets their license at 40, they may be a little more mature *in general* than 18 year olds, but they aren't any more experienced driving than an 18 year old.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 11, 2018, 03:45:03 PM

Well, while Trade tends to be very specific in the roundabouts he identifies as being problematic, you tend to treat them all as bad guys.  If one has a problem, they al don't necessarily have a problem.

And web's age shouldn't have anything to do with it, because it's not just 18 year olds getting into accidents in roundabouts. If someone gets their license at 40, they may be a little more mature *in general* than 18 year olds, but they aren't any more experienced driving than an 18 year old.
I tend to believe that roundabouts are sort of "cargo cult" as it stands. Some may work, but that seems a minority from my experience. Even fewer of them are actually better that other possible arrangements.

As for age - there are statistical reasons why Web's insurance premium should be 3x higher than mine. It is entirely possible that Web himself is a Nascar-grade driver with exceptional abilities.. But he talks as a literally backseat driver criticizing those who are actually behind the wheel.
Which is perfectly normal for 18 year old  - I think I was even bigger pain in the rear at that age. And I wouldn't even bother if that was something benign - but such approach can easily translate into cavalier attitude on the road. Hence my usual "idiot" comment.  And yes, I do remember that I am probably an average driver surrounded by average drivers - and we all prone to mistakes.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 11, 2018, 04:19:42 PM
I tend to believe that roundabouts are sort of "cargo cult" as it stands. Some may work, but that seems a minority from my experience.

I know we kind of had this discussion earlier, but what do you mean by "work"?  What roundabouts in your experience don't work and why?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 11, 2018, 04:21:51 PM

Kalvado hates all roundabouts.

You're cutting a corner here.
Kalvado hates, when things are done just for sake of doing it "cool" without understanding. Most roundabouts I saw are built because they are cool, without underlying understanding. Hence...

So, you hate the engineers? The roundabouts didn't build themselves...

Roundabouts are not built because they're "cool". They're built because the engineers think they'll improve things.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 11, 2018, 04:30:31 PM

Kalvado hates all roundabouts.

You're cutting a corner here.
Kalvado hates, when things are done just for sake of doing it "cool" without understanding. Most roundabouts I saw are built because they are cool, without underlying understanding. Hence...

So, you hate the engineers? The roundabouts didn't build themselves...

Roundabouts are not built because they're "cool". They're built because the engineers think they'll improve things.

Looks like a lot of folks are hired to build roads, not to think about it...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 11, 2018, 04:49:24 PM

Kalvado hates all roundabouts.

You're cutting a corner here.
Kalvado hates, when things are done just for sake of doing it "cool" without understanding. Most roundabouts I saw are built because they are cool, without underlying understanding. Hence...

So, you hate the engineers? The roundabouts didn't build themselves...

Roundabouts are not built because they're "cool". They're built because the engineers think they'll improve things.

Looks like a lot of folks are hired to build roads, not to think about it...

As I've mentioned up-thread several times, not all engineers are privy to data we might think they are. There are conferences from time to time, but not all engineers attend them.

Here's a new way of looking at things: consider all the cities, towns, and counties across the US that have zero roundabouts. Are the engineers who run them on top of the recent data, and have decided not to build any roundabouts? Have they thought about building them, but don't have the money? Are they even familiar with roundabouts?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 11, 2018, 05:02:55 PM

Kalvado hates all roundabouts.

You're cutting a corner here.
Kalvado hates, when things are done just for sake of doing it "cool" without understanding. Most roundabouts I saw are built because they are cool, without underlying understanding. Hence...

So, you hate the engineers? The roundabouts didn't build themselves...

Roundabouts are not built because they're "cool". They're built because the engineers think they'll improve things.

Looks like a lot of folks are hired to build roads, not to think about it...

As I've mentioned up-thread several times, not all engineers are privy to data we might think they are. There are conferences from time to time, but not all engineers attend them.

Here's a new way of looking at things: consider all the cities, towns, and counties across the US that have zero roundabouts. Are the engineers who run them on top of the recent data, and have decided not to build any roundabouts? Have they thought about building them, but don't have the money? Are they even familiar with roundabouts?

Yes of course, that is a part of it.
However back in 5000 BC people invented a cool thing called "writing". That allows a person - "reader" - to get a message from a "writer" far away, and possibly years later.. Over time, that was perfected into "books", "magazines", "guidelines", "laws", "manuals", "journals" - and many other forms. There is plenty of data going around.
However some things lost over time are "common sense" and "critical thinking" - sometimes not replaces by proper "reading" skills, as you mentioned. And that creates some interesting situations as you described.

But overall I can see significant number of design flaws around. For example - I can think of at least 4 issues on local divided highways where stripping is apparently flawed- but is not fixed for many years. I am not talking about expensive projects where funding may be an issue, but about simple lines on a pavement.
So I have to remind myself, as I did above - most professionals around are about average, and half of them are worse than average. And person with lowest passing grade in medical school is still called a "doctor". But I don't have to be happy about overall outcome.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 11, 2018, 05:04:54 PM
For example - I can think of at least 4 issues on local divided highways where stripping is apparently flawed- but is not fixed for many years. I am not talking about expensive projects where funding may be an issue, but about simple lines on a pavement.

If it's a minor error, then it's easy for me to imagine it being far down the list of projects.  Basically in the "if money flies through the window" category.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 11, 2018, 05:10:15 PM
For example - I can think of at least 4 issues on local divided highways where stripping is apparently flawed- but is not fixed for many years. I am not talking about expensive projects where funding may be an issue, but about simple lines on a pavement.

If it's a minor error, then it's easy for me to imagine it being far down the list of projects.  Basically in the "if money flies through the window" category.
Is daily traffic jam because of that stripping is a good enough reason to move things up the list?
Somehow roundabouts do get funding - including funding under "reducing air pollution" category...
Or, even better, a full rebuild of a road exactly according decades old blueprints - without taking into account new traffic distribution, but carefully replicating decades old flaw which caused 2 fatal accident just over past 2 years? 
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on January 11, 2018, 05:44:33 PM
Did it ever occur to you that if specific structure causes more problems than others, it may be problem of the structure?

Of course, but I fail to see the relevance of that question.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 11, 2018, 06:09:11 PM
Did it ever occur to you that if specific structure causes more problems than others, it may be problem of the structure?

Of course, but I fail to see the relevance of that question.
Because you squarely attributed the problem to
driver ignorance and hesitation
Looking at the "age" field, I suspect that your driving experience is not sufficient to realize that roads are less than perfect, that another explanation to "hesitation" is envisioning hazard you are not seeing and so on. Hence my question.
More than a year seem to be sufficient experience to recognize those things - of course if you were actively driving during that time.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on January 11, 2018, 06:24:04 PM
Did it ever occur to you that if specific structure causes more problems than others, it may be problem of the structure?

Of course, but I fail to see the relevance of that question.


Agreed. He seems way overfocused on your age. No clue what "structures" he's referring to. And unless it's a bunch of 18 year olds having accidents on those structures, age doesn't matter.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 11, 2018, 07:43:08 PM
Did it ever occur to you that if specific structure causes more problems than others, it may be problem of the structure?

Of course, but I fail to see the relevance of that question.


Agreed. He seems way overfocused on your age. No clue what "structures" he's referring to. And unless it's a bunch of 18 year olds having accidents on those structures, age doesn't matter.

(https://res.cloudinary.com/value-penguin/image/upload/f_auto,q_auto/v1499958838/how-age-affects-auto-insurance_nusnsz.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 11, 2018, 08:09:33 PM
Looking at the "age" field, I suspect that your driving experience is not sufficient to realize that roads are less than perfect, that another explanation to "hesitation" is envisioning hazard you are not seeing and so on. Hence my question.
More than a year seem to be sufficient experience to recognize those things - of course if you were actively driving during that time.

Wait...so he's not experienced enough to realise that experience isn't necessarily important?
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on January 11, 2018, 08:35:20 PM
Did it ever occur to you that if specific structure causes more problems than others, it may be problem of the structure?
Of course, but I fail to see the relevance of that question.
Because you squarely attributed the problem to
driver ignorance and hesitation
I meant drivers are hesitant and ignorant when using roundabouts, and especially new ones. It doesn't mean there's a problem with the roundabout, it's just a fact of life that change takes some getting used to, especially on the road. Roundabouts are, after all, a relatively new concept.
Quote
Looking at the "age" field, I suspect that your driving experience is not sufficient to realize that roads are less than perfect,
You really went there?  :-D I've been dreaming up road improvements longer than I can remember. I'm the first to notice glitches or imperfections :meh:
Quote
that another explanation to "hesitation" is envisioning hazard you are not seeing and so on. Hence my question.
Hesitation comes from lack of experience making a movement, or uncertainty as to what to expect from other drivers. It mellows with time.
Quote
More than a year seem to be sufficient experience to recognize those things - of course if you were actively driving during that time.
I actively drive every day, and go out of my way to drive extra miles, too.

Agreed. He seems way overfocused on your age. No clue what "structures" he's referring to. And unless it's a bunch of 18 year olds having accidents on those structures, age doesn't matter.
Agreed. With age comes experience, so of course learners are slightly more of a risk on the road. But:
1] I'm no longer a learner.
2] in the case of a roadgeek, knowledge comes many years before experience.
3] My age has no bearing on this particular knowledge-based discussion whatsoever.

(Oh, and I assumed "structures" = roundabouts  :hmmm:)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 12, 2018, 12:54:38 PM
I can think of at least 4 issues on local divided highways where stripping is apparently flawed- but is not fixed for many years ... simple lines on a pavement.

If it's a minor error, then it's easy for me to imagine it being far down the list of projects.  Basically in the "if money flies through the window" category.
Is daily traffic jam because of that stripping is a good enough reason to move things up the list?

Where the heck are these four places where "simple lines on a pavement" are causing "daily traffic jam"?  Have you brought them up with the appropriate agency?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 16, 2018, 02:35:14 AM
Title: Re: Crash prone 'modern roundabouts'
Post by: Hurricane Rex on January 16, 2018, 02:42:16 AM

Kalvado hates all roundabouts.

You're cutting a corner here.
Kalvado hates when things are done just for sake of doing it "cool" without understanding. Most roundabouts I saw are built because they are cool, without underlying understanding. Hence...

So, you hate the engineers? The roundabouts didn't build themselves...

Roundabouts are not built because they're "cool". They're built because the engineers think they'll improve things.

Looks like a lot of folks are hired to build roads, not to think about it...

Trying to be humorous and serious but may fail miserably: And if they don't what then?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 16, 2018, 10:05:44 AM

I knew that Washington compact roundabout design looked familiar to me.  This fatal crash happened at the Badger Rd & Northwood Rd roundabout near Lynden less than a year after the roundabout was completed. 

(http://www.bellinghamherald.com/news/local/8vi2jz/picture153280689/alternates/LANDSCAPE_1140/crash1)
(http://www.bellinghamherald.com/news/local/b5a695/picture153280694/alternates/FREE_1140/crash2)
http://www.bellinghamherald.com/news/local/article153269789.html
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 16, 2018, 04:00:58 PM
https://youtu.be/UWqzmVGKDNk

I knew that Washington compact roundabout design looked familiar to me.  This fatal crash happened at the Badger Rd & Northwood Rd roundabout near Lynden less than a year after the roundabout was completed. 

http://www.bellinghamherald.com/news/local/article153269789.html

I don't know why they opted for a mini rounbabout at Northwood, when the preceding roundabouts at Bender and Depot were full-scale roundabouts. Nonetheless, the crash pictured was a classic T-bone possible at all roundabouts.

From the perspective of someone who passes by the Slater Rd roundabouts on a decently frequent basis, the roundabouts do seem to have been a smart choice for the ramp terminals, even if those terrible side-impact crashes are still a possibility.

IIRC, you don't really have a problem with single-lane roundabouts, right?
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 16, 2018, 04:30:55 PM
IIRC, you don't really have a problem with single-lane roundabouts, right?

Obviously I can't speak for tradephoric, but that seems to be what others have said about him, not necessarily what he's stated in so many words.  What he has said is that it seems multi-lane roundabouts generate more frequent and more severe accidents and so he has a problem with them–unless there are steps to be taken to reduce the frequency and severity of those crashes, one of which steps might be restricting the flow of the circulating roadway down to a mix of one and two lanes.  My own reading of tradephoric is that he's willing to base his opinions on what the data suggest, which may or may not fall squarely along the single-/multi-lane divide.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 16, 2018, 06:56:45 PM
I can think of at least 4 issues on local divided highways where stripping is apparently flawed- but is not fixed for many years ... simple lines on a pavement.

If it's a minor error, then it's easy for me to imagine it being far down the list of projects.  Basically in the "if money flies through the window" category.
Is daily traffic jam because of that stripping is a good enough reason to move things up the list?

Where the heck are these four places where "simple lines on a pavement" are causing "daily traffic jam"?  Have you brought them up with the appropriate agency?
AT least some of those points were brought up here when people working for local DOT were participating in discussion.
Best response I got (I can look it up, quote is approximate) - departments have a lot of people who counter any change with "it worked for 20 years, why do you want to change it?". That inhibits any meaningful changes.
Why roundabouts do get built in such environment? I don't know; I suspect numbers on the contracts are too attractive - unlike low profile restripping.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 16, 2018, 07:06:17 PM

2] in the case of a roadgeek, knowledge comes many years before experience.
3] My age has no bearing on this particular knowledge-based discussion whatsoever.

OK, let's talk knowledge. What can you tell us about roundabouts - beyond what DOT says in driver's manual and advertizing materials?
FOr example, how does throughput of roundabout changes with number of circulating lanes?
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on January 16, 2018, 07:52:34 PM
Going there not going there. Sorry not sorry.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 17, 2018, 09:42:00 AM

2] in the case of a roadgeek, knowledge comes many years before experience.
3] My age has no bearing on this particular knowledge-based discussion whatsoever.

OK, let's talk knowledge. What can you tell us about roundabouts - beyond what DOT says in driver's manual and advertizing materials?
FOr example, how does throughput of roundabout changes with number of circulating lanes?

That doesn't actually negate his statements.  But it doesn't finally get us off the topic of age, at least.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 17, 2018, 10:49:49 AM

2] in the case of a roadgeek, knowledge comes many years before experience.
3] My age has no bearing on this particular knowledge-based discussion whatsoever.

OK, let's talk knowledge. What can you tell us about roundabouts - beyond what DOT says in driver's manual and advertizing materials?
FOr example, how does throughput of roundabout changes with number of circulating lanes?

That doesn't actually negate his statements.  But it doesn't finally get us off the topic of age, at least.
Yes, to the questions where roadgeek hobby wouldn't help to find an answer. It is not about counting exits and shaming other drivers, you know...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 18, 2018, 02:59:54 PM
One of the last major roundabouts in Doha, Qatar has been converted to an at-grade signalized intersection.  Looking at historical imagery of Doha, it’s quite amazing just how many major-roundabouts have been converted to signalized intersections in a short period of time.  According to Salem Al-Shawai, Assistant Director of the Roads Projects Department at the Public Works Authority, converting roundabouts to signal-controlled intersections has greatly enhances traffic-flow in the city.

https://www.thepeninsulaqatar.com/article/15/06/2017/Qatar-residents-bid-goodbye-to-Sports-Roundabout

The deal with Doha is the roundabouts there were massive.  I remember first encountering Doha roundabouts several years ago when researching if any 3x3 geometry roundabouts in America existed.  While I couldn’t find any in America, many examples existed in Doha.  The problem is roundabouts break down when traffic volumes get too high and that is seemingly what happened in Doha (the population went from 500,000 in 2004 to over 1.3 million people today).  The roundabouts simply couldn't handle the influx of traffic.  I’ll tell you one thing for sure… Jim Brainard is not the mayor of Doha.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 18, 2018, 04:44:39 PM
  I’ll tell you one thing for sure… Jim Brainard is not the mayor of Doha.
C'mon, a dream situation for any executive/official: first you get funding to build something, run a big project, everyone is happy - jobs, cash flow, visible progress
Then you discover things do not work as expected, get more funding to redo things, everyone is happy again  - jobs, cash flow, visible progress.
Those who pay for it may get upset eventually, but you just need to manage expectations correctly
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 19, 2018, 10:41:33 AM
A partial triple-lane roundabout is being proposed in Greenwood, Indiana.  The  roundabout at Madison Ave & Smith Valley Road will be about 250 feet from the traffic signal at Smith Valley Road and US 31 (roundabout traffic will routinely queue up through the US31 signal).  Even in the model pictured you have a queue of cars at the roundabout with US31 SBLT traffic being released into the queue... rear end accidents anyone?  Here is a link to the public open house presentation given.  In it they state that roundabouts reduce total crashes by 44% compared to traditional intersections.  Crashes are more likely to increase 444% if this triple-lane roundabout is built, but whatever.  By then it will be built and the promises of how well this roundabout will work will be forgotten.

(http://www.greenwood.in.gov/egov/images/1477908383_84238.jpg)
http://www.greenwood.in.gov/egov/documents/1512413834_41847.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on January 19, 2018, 10:45:03 AM
A partial triple-lane roundabout is being proposed in Greenwood, Indiana.  The  roundabout at Madison Ave & Smith Valley Road will be about 250 feet from the traffic signal at Smith Valley Road and US 31 (roundabout traffic will routinely queue up through the US31 signal).  Even in the model pictured you have a queue of cars at the roundabout with US31 SBLT traffic being released into the queue... rear end accidents anyone?  Here is a link to the public open house presentation given.  In it they state that roundabouts reduce total crashes by 44% compared to traditional intersections.  Crashes are more likely to increase 444% if this triple-lane roundabout is built, but whatever.  By then it will be built and the promises of how well this roundabout will work will be forgotten.

(http://www.greenwood.in.gov/egov/images/1477908383_84238.jpg)
http://www.greenwood.in.gov/egov/documents/1512413834_41847.pdf

I see traffic stopped at 3 out of the 4 legs of the standard intersection.  Rear end accidents anyone?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 19, 2018, 10:50:29 AM
A partial triple-lane roundabout is being proposed in Greenwood, Indiana.  The  roundabout at Madison Ave & Smith Valley Road will be about 250 feet from the traffic signal at Smith Valley Road and US 31 (roundabout traffic will routinely queue up through the US31 signal).  Even in the model pictured you have a queue of cars at the roundabout with US31 SBLT traffic being released into the queue... rear end accidents anyone?  Here is a link to the public open house presentation given.  In it they state that roundabouts reduce total crashes by 44% compared to traditional intersections.  Crashes are more likely to increase 444% if this triple-lane roundabout is built, but whatever.  By then it will be built and the promises of how well this roundabout will work will be forgotten.


I see traffic stopped at 3 out of the 4 legs of the standard intersection.  Rear end accidents anyone?
You know, that is one of the things that causes concerns when red light cameras are installed. Managing the expectations. I am fairly used to waiting in line at roundabout entry, but that is not what is advertised as the way they operate.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 19, 2018, 11:01:02 AM
Considering that no triple lane roundabout built in America has ever seen a reduction in crashes, it's laughable to think that the Greenwood roundabout is going to be the first one that does.  A recent triple lane roundabout at 14 Mile & Orchard Lake was built about 200 feet from a signalized intersection in Michigan.  It had the most crashes in the entire state of Michigan last year.  You really think Indiana drivers are going to flow through this roundabout just fine?   Yep J&N, just rip on how bad Michigan drivers are then... until there are like 130 crashes at that Indiana roundabout when the year before the roundabout there was like 13.  Yep, Indiana drivers are great.

Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 19, 2018, 02:18:43 PM
The  roundabout ... will be about 250 feet from the traffic signal ...

Yuck.  No.  Bad.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on January 19, 2018, 02:22:53 PM
Also...how many at-grade jughandles are in Indiana, such as the one in the graphic above?  That in itself is a learning experience for those that want to turn left, but need to from the right lane.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on January 19, 2018, 09:12:35 PM
The  roundabout ... will be about 250 feet from the traffic signal ...

Yuck.  No.  Bad.
And the existing traffic signal being replaced is the same distance away.  Traffic isn't suddenly going to backup in greater numbers by replacing one intersection type with another.

I drive through this intersection a few times a year when I go to my car dealer.   There is much more turning traffic than thru traffic at this intersection, and a roundabout should be an improvement for turning traffic vs the current intersection.

Also the diagram posted by trade doesn't show the additional connectivity to US 31 just to the south.  A good portion of the volume through this intersection is either coming from or going to the intersection of Madison Ave with US 31 further south:  https://www.google.com/maps/@39.6056363,-86.1070826,321m/data=!3m1!1e3    Due to all the turning traffic coming from or going to the intersection to the south the short segment between US 31 and Madison on Smith Valley has lower traffic volume.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on January 19, 2018, 09:31:20 PM
Yep, Indiana drivers are great.
Feel free to make a field trip to Carmel and watch the experienced Indiana drivers navigating over 105 roundabouts with ease on a daily basis.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 19, 2018, 10:47:28 PM
I can tell by the setup that the Greenwood roundabout will likely need box markings to prevent blocking. Doesn't mean it's a bad place for a roundabout, though.

Will any city build a signalised roundabout at some point?
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on January 19, 2018, 11:37:45 PM
Will any city build a signalised roundabout at some point?

I think that's called a traffic circle  :D
Title: Re: Crash prone 'modern roundabouts'
Post by: kj3400 on January 19, 2018, 11:42:48 PM
Will any city build a signalised roundabout at some point?

I think that's called a traffic circle  :D

The UK's signalized roundabouts would like to have a word.
Title: Re: Crash prone 'modern roundabouts'
Post by: Brian556 on January 20, 2018, 12:30:15 AM
I can tell by the setup that the Greenwood roundabout will likely need box markings to prevent blocking. Doesn't mean it's a bad place for a roundabout, though.

Will any city build a signalised roundabout at some point?

There is one. Columbus Cir in NYC
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 20, 2018, 02:08:06 AM
I can tell by the setup that the Greenwood roundabout will likely need box markings to prevent blocking. Doesn't mean it's a bad place for a roundabout, though.

Will any city build a signalised roundabout at some point?

There is one. Columbus Cir in NYC

That's more of a signalised traffic circle. I'm talking about a roundabout laid out in a "modern roundabout" way with deflection and whatnot, but with signals.

Carmel's metered roundabouts along the Keystone Parkway are sort of up this alley, but aren't quite fully signalised.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 22, 2018, 10:39:33 AM
The  roundabout ... will be about 250 feet from the traffic signal ...

Yuck.  No.  Bad.
And the existing traffic signal being replaced is the same distance away.  Traffic isn't suddenly going to backup in greater numbers by replacing one intersection type with another.

You are ignoring the fact that closely spaced traffic signals can be coordinated so that the main platoon clears both intersections.  You lose that coordination when one of the signals is converted to a roundabout.  CJW, you really can’t see the potential of EB Smith Valley Road traffic backing up through the U.S. 31 intersection once the roundabout is complete?   A triple-lane roundabout within 250 feet of a major signalized intersection along U.S. 31…. I don’t care how you want to spin it… that’s no bueno.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 22, 2018, 02:09:59 PM
The  roundabout ... will be about 250 feet from the traffic signal ...

Yuck.  No.  Bad.
And the existing traffic signal being replaced is the same distance away.  Traffic isn't suddenly going to backup in greater numbers by replacing one intersection type with another.

You are ignoring the fact that closely spaced traffic signals can be coordinated so that the main platoon clears both intersections.  You lose that coordination when one of the signals is converted to a roundabout.

↑  Exactly.  No possibility of coordination.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on January 22, 2018, 10:37:44 PM
The  roundabout ... will be about 250 feet from the traffic signal ...

Yuck.  No.  Bad.
And the existing traffic signal being replaced is the same distance away.  Traffic isn't suddenly going to backup in greater numbers by replacing one intersection type with another.

You are ignoring the fact that closely spaced traffic signals can be coordinated so that the main platoon clears both intersections.  You lose that coordination when one of the signals is converted to a roundabout.  CJW, you really can’t see the potential of EB Smith Valley Road traffic backing up through the U.S. 31 intersection once the roundabout is complete?   A triple-lane roundabout within 250 feet of a major signalized intersection along U.S. 31…. I don’t care how you want to spin it… that’s no bueno.

I understand the concern, I just don't believe the traffic is that heavy on that short east/west segment.   There is far more traffic turning onto US 31 north or south than there is crossing US 31.  Now I could be wrong as my personal experience is limited to making trips on Smith Valley through that area only a few times each year (usually during weekday traffic), but every time I've been in that area there has been no signs of heavy east/west traffic on that short segment.  Southbound traffic on US 31 has minimal reason to turn left as that route would soon take them back north (the direction they came from).  Northbound traffic on US 31 has virtually no reason to turn right on Smith Valley as anyone that wants to go east has already turned off at the Madison intersection just to the south and would approach the roundabout from the south and not the east.   That leaves only what limited eastbound traffic would be crossing US 31 on Smith Valley and I simply don't expect much volume there.

For westbound traffic on Smith Valley, most traffic turns left on Madison to get to US 31 southbound via the next intersection to the south, they don't go straight to turn left on US 31.  There is minimal traffic that continues on Smith Valley with the intention to cross US 31.

I don't have actual traffic counts but would expect that the engineers did have that info and took it into account before deciding on this design.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 23, 2018, 08:26:38 AM
The  roundabout ... will be about 250 feet from the traffic signal ...

Yuck.  No.  Bad.
And the existing traffic signal being replaced is the same distance away.  Traffic isn't suddenly going to backup in greater numbers by replacing one intersection type with another.

You are ignoring the fact that closely spaced traffic signals can be coordinated so that the main platoon clears both intersections.  You lose that coordination when one of the signals is converted to a roundabout.  CJW, you really can’t see the potential of EB Smith Valley Road traffic backing up through the U.S. 31 intersection once the roundabout is complete?   A triple-lane roundabout within 250 feet of a major signalized intersection along U.S. 31…. I don’t care how you want to spin it… that’s no bueno.

I understand the concern, I just don't believe the traffic is that heavy on that short east/west segment.   There is far more traffic turning onto US 31 north or south than there is crossing US 31.  Now I could be wrong as my personal experience is limited to making trips on Smith Valley through that area only a few times each year (usually during weekday traffic), but every time I've been in that area there has been no signs of heavy east/west traffic on that short segment.  Southbound traffic on US 31 has minimal reason to turn left as that route would soon take them back north (the direction they came from).  Northbound traffic on US 31 has virtually no reason to turn right on Smith Valley as anyone that wants to go east has already turned off at the Madison intersection just to the south and would approach the roundabout from the south and not the east.   That leaves only what limited eastbound traffic would be crossing US 31 on Smith Valley and I simply don't expect much volume there.

For westbound traffic on Smith Valley, most traffic turns left on Madison to get to US 31 southbound via the next intersection to the south, they don't go straight to turn left on US 31.  There is minimal traffic that continues on Smith Valley with the intention to cross US 31.

I don't have actual traffic counts but would expect that the engineers did have that info and took it into account before deciding on this design.
There is no data for that specific segment; 27.5 and 36k on US 31 north and south of intersection respectively; 14 and 19 on Smith Valley and 17k on Madison.
Seems like there is a good chunk of local traffic..
http://indot.ms2soft.com/tcds/tsearch.asp?loc=Indot&mod=
Title: Re: Crash prone 'modern roundabouts'
Post by: tdindy88 on January 23, 2018, 09:17:54 PM
I think traffic's a little heavy going west on Smith Valley around rush hours based on my experiences there but the rest of the time the setup should be okay, I think. The loop ramp from EB Smith Valley to NB 31 is what irks me a little, I don't know if there's any advantage to having them use the roundabout to do a u-turn to turn head back west on Smith Valley and north on 31 but I suppose it may be to eliminate more people from having to use the roundabout. That or they could have traffic turn south onto Madison and then loop back up to US 31 at the light down there.

Fun fact about the area, the road just east of the roundabout is Meridian Street, but it's not the same Meridian Street as in Indianapolis. Sometimes it is called Old Meridian to differentiate the two. My travels through the area usually involve Old Meridian, Smith Valley and Madison to get to US 31.

I took a look at the plans for this roundabout online and saw that they are adding some things around it to beautify the area including what I believe to be a small column with the letter G (for Greenwood) in the middle of the roundabout. So when the first death occurs here we now know who to blame.

Note, I don't believe turning every road into Woodward Avenue or Telegraph Road is the way to go, I certainly believe these roundabouts to work most of the time and seem to be fine in Carmel, there's a one-lane roundabout very close to my residence on the southside of Indy that has really helped traffic flow in that area.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 02, 2018, 10:37:59 AM
The Northland and Richmond roundabout in Appleton opened on September 1.  According to Appleton Police there have been 25 reported crashes between August 31st and October 10th.  At the current crash rate, there will be 228 crashes at the roundabout in the first year of operation.  Compare that to 27 crashes in all of 2014 when it was a signalized intersection (the highest crash intersection in Appleton that year).  On the project website, the stated reason the roundabout was selected was to address the high rate of crashes that were occurring at the signaled intersection.  This is the design they came up with.

(http://static-20.sinclairstoryline.com/resources/media/e5ea2b53-be3b-4ca3-96c9-6ef588ec9840-large16x9_47ooRab.jpg)

So after 25 crashes in just 40 days, does anyone still think the roundabout will do a good job at reducing crashes at the intersection moving forward?  While there probably won't be 228 crashes per year, this roundabout could easily see 100+ crashes per year.  Their baseline is 27 crashes, and 100+ crashes is about 4X worse than that.  As long as this roundabout remains a complex 3x2 roundabout next to a busy commercial district, crashes will remain a problem.  But fear not, they will study the roundabout and throw hundreds of thousands of additional dollars to “fix”  the roundabout that they just completed.  Good job.

Crash numbers increase in new roundabout
http://fox11online.com/news/local/crash-numbers-increase-in-new-roundabout


After 155 days of opening, there have been 77 crashes at the new Northland and Richmond roundabout in Appleton (compared to 27 crashes/yr before the roundabout).  At the current crash rate there will be 181 crashes in the first year of operation.  The city is already attempting to "fix" the 155 day old roundabout by adding new signage.  Doubt it will be too effective...my prediction is that in a year or two, the city will eliminate a circulating lane inside the roundabout at a significant cost to the people of Appleton. 

Crashes continue in Appleton roundabout
http://fox11online.com/news/local/crashes-continue-in-appleton-roundabout
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 02, 2018, 10:50:06 AM
^In 2014 the top 10 highest crash intersections in Appleton experienced a combined 182 crashes.  At it's current crash rate, the crashes at the new roundabout will be equivalent to the sum of the crashes of the ten worst intersections in the city. 

Link to the 2014 Appleton Annual Crash overview:
http://fox11digital.com//news/PDFs/Appleton-Annual-Crash-Overview-2014.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on February 02, 2018, 06:50:40 PM
Quote from: Sgt. Dave Lund, APD
"The reality is roundabouts aren't supposed to be the cure to eliminate all crashes. They're supposed to do exactly what this roundabout is doing, which is eliminating the serious, injury-causing accidents"

Interesting quote from further down in the news story.

After 155 days of opening, there have been 77 crashes at the new Northland and Richmond roundabout in Appleton (compared to 27 crashes/yr before the roundabout).  At the current crash rate there will be 181 crashes in the first year of operation.  The city is already attempting to "fix" the 155 day old roundabout by adding new signage.  Doubt it will be too effective...my prediction is that in a year or two, the city will eliminate a circulating lane inside the roundabout at a significant cost to the people of Appleton. 

You assume the crash rate is going to increase, but in actuality, from those I've heard from in the Appleton-area, the rate is currently decreasing. And the project had significant funding from the state, meaning the city of Appleton would likely contribute a very small percentage IF design changes are deemed necessary.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 02, 2018, 07:03:55 PM
The city is already attempting to "fix" the 155 day old roundabout by adding new signage.
did they bill whoever designed the thing for new signage and 100 crashes due to poor design work? Companies - and engineers - should go out of business for such type of things. Or personal responsibility is so non-democratic?....
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on February 02, 2018, 07:15:53 PM
The city is already attempting to "fix" the 155 day old roundabout by adding new signage.
did they bill whoever designed the thing for new signage and 100 crashes due to poor design work? Companies - and engineers - should go out of business for such type of things. Or personal responsibility is so non-democratic?....

Yes, let's bill WisDOT...there's a smart idea.  :rolleyes:  That's like giving a police car a parking ticket. How about billing the drivers crashing because they can't follow a yield sign? Or get into the proper lane before entering? As other articles have said, the overwhelming majority of crashes at this site have been caused by drivers not yielding properly. The roundabout is not causing people to crash, poor driving habits is.

And why only hold the engineers accountable? You do realize construction projects get approved by politicians. They knew what they were getting into. In the case of this intersection, the choice was either this roundabout or an expanded signalized intersection, which would do nothing about fatal crashes, and would have been at the cost of at least 3 of the four businesses on that corner. These things are not as black and white as some would like to think they are.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 02, 2018, 08:16:54 PM
The city is already attempting to "fix" the 155 day old roundabout by adding new signage.
did they bill whoever designed the thing for new signage and 100 crashes due to poor design work? Companies - and engineers - should go out of business for such type of things. Or personal responsibility is so non-democratic?....

Yes, let's bill WisDOT...there's a smart idea.  :rolleyes:  That's like giving a police car a parking ticket. How about billing the drivers crashing because they can't follow a yield sign? Or get into the proper lane before entering? As other articles have said, the overwhelming majority of crashes at this site have been caused by drivers not yielding properly. The roundabout is not causing people to crash, poor driving habits is.

And why only hold the engineers accountable? You do realize construction projects get approved by politicians. They knew what they were getting into. In the case of this intersection, the choice was either this roundabout or an expanded signalized intersection, which would do nothing about fatal crashes, and would have been at the cost of at least 3 of the four businesses on that corner. These things are not as black and white as some would like to think they are.

Oh yes! Blame the victim!
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on February 03, 2018, 05:08:32 AM
Oh yes! Blame the victim!

"I was assaulted by that roundabout! It's time we stood up and talked about roundabout harassment in this country! #metoo"
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 03, 2018, 02:20:15 PM
Oh yes! Blame the victim!

"I was assaulted by that roundabout! It's time we stood up and talked about roundabout harassment in this country! #metoo"

I'm not sure where you were going with that sarcasm, but these large roundabouts do indeed seem to be the problem in the equation.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on February 03, 2018, 02:29:19 PM
Oh yes! Blame the victim!
"I was assaulted by that roundabout! It's time we stood up and talked about roundabout harassment in this country! #metoo"
I'm not sure where you were going with that sarcasm, but these large roundabouts do indeed seem to be the problem in the equation.

My point was that there seems to be an awful lot of blaming the engineer and/or politician who designed or approved, respectively, of these roundabouts, and not the idiots who drive through them and cause accidents.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 03, 2018, 02:56:24 PM
Oh yes! Blame the victim!
"I was assaulted by that roundabout! It's time we stood up and talked about roundabout harassment in this country! #metoo"
I'm not sure where you were going with that sarcasm, but these large roundabouts do indeed seem to be the problem in the equation.

My point was that there seems to be an awful lot of blaming the engineer and/or politician who designed or approved, respectively, of these roundabouts, and not the idiots who drive through them and cause accidents.
For some of us those idiots are primarily taxpayers, who  fund all that construction, as well as provide the paycheck for engineers and politicians via their taxes; and citizens, most of them are also  dully licensed drivers. Please try to re-read your post with that in mind.

And a definition from Miriam-Webster dictionary.

snob:    
3 a : one who tends to rebuff, avoid, or ignore those regarded as inferior
3 b : one who has an offensive air of superiority in matters of knowledge or taste

Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on February 03, 2018, 04:22:28 PM
and citizens, most of them are also  dully licensed drivers.

I'll give you that, ironic misspelling or not.

Quote
And a definition from Miriam-Webster dictionary[…]

And now a definition from Merriam-Webster:

irony

1. a pretense of ignorance and of willingness to learn from another assumed in order to make the other's false conceptions conspicuous by adroit questioning – called also Socratic irony

2. a : the use of words to express something other than and especially the opposite of the literal meaning
b : a usually humorous or sardonic literary style or form characterized by irony
c : an ironic expression or utterance
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on February 03, 2018, 09:12:59 PM
Oh yes! Blame the victim!

Yup. And I'm going to sleep just fine doing so. Just the same if someone crashes after blowing a red light or a stop sign. If someone does either of those, 99% of the time it's not the traffic signals' fault, nor the stop sign.*

As I've said before, there are bad roundabout designs/designers out there (I've reviewed some of their work and tried to make corrections - sometimes to no avail, unfortunately), but I'm not going to chalk up failure to yield on a poor design or file them into the 'all roundabouts are bad/a waste of time' category, at least not in this case. I've been through the site many times. The signs and markings are clear as day. Even a good number of the Facebook comments from the Fox 11 story wonder [paraphrasing] 'what kind of idiot can't negotiate that intersection without crashing'.

* Now if the signal was malfunctioning (e.g., displaying opposing greens at the same time) or the stop sign was missing/vandalized, that's a different situation.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 04, 2018, 11:40:00 AM
You assume the crash rate is going to increase, but in actuality, from those I've heard from in the Appleton-area, the rate is currently decreasing. And the project had significant funding from the state, meaning the city of Appleton would likely contribute a very small percentage IF design changes are deemed necessary.

On October 13th 2008 the DJIA had it's largest daily points increase on record rising 936 points.  Sounds great right?  Well considering the DJIA had plunged 3,000 points in the previous 8 trading days, that rise wasn't really that impressive.  The 936 rise was nothing more than a dead cat bounce as the DJIA continued to trend downward before bottoming out in March 2009.  The point is you got to look at the context of any event.  Should we be impressed that the latest data shows a slight reduction in the crash rate at the roundabout when compared to the crash rate when the roundabout first opened - even though the current roundabout crash rate is still several times higher than the signalized intersection it replaced?  You are focusing on the "dead cat bounce" and ignoring the overall failure of the roundabout in reducing the crash rate.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on February 04, 2018, 02:45:58 PM
You assume the crash rate is going to increase, but in actuality, from those I've heard from in the Appleton-area, the rate is currently decreasing. And the project had significant funding from the state, meaning the city of Appleton would likely contribute a very small percentage IF design changes are deemed necessary.

On October 13th 2008 the DJIA had it's largest daily points increase on record rising 936 points.  Sounds great right?  Well considering the DJIA had plunged 3,000 points in the previous 8 trading days, that rise wasn't really that impressive.  The 936 rise was nothing more than a dead cat bounce as the DJIA continued to trend downward before bottoming out in March 2009.  The point is you got to look at the context of any event.  Should we be impressed that the latest data shows a slight reduction in the crash rate at the roundabout when compared to the crash rate when the roundabout first opened - even though the current roundabout crash rate is still several times higher than the signalized intersection it replaced?  You are focusing on the "dead cat bounce" and ignoring the overall failure of the roundabout in reducing the crash rate.

Careful, your bias is sticking out again...please try to tuck it in a little.

Congrats on the talent of being able to see the future. Any stock tips you'd like to share? Winning lotto numbers? Hindsight is always 20/20. Frankly, your assumptions aren't much different. You're declaring failure after only five months and a very small data set. Any one of these months could end up being statistical outlier. A typical crash analysis needs at least 3 years of before and after data to be given serious consideration. Even the APD officer knows you won't eliminate accidents. As the APD officer also said, there's only been ONE injury crash out of 77. No fatalities. The same could not have been said had the signal remained. Am I saying it's a great situation? Am I saying I'm happy to see any accidents, let alone an increase? No, not even close, but so far it's better than the alternative was.

Quote
Lund told the silver lining is that only one of those crashes resulted in an injury.

"The reality is roundabouts aren't supposed to be the cure to eliminate all crashes. They're supposed to do exactly what this roundabout is doing, which is eliminating the serious, injury-causing accidents," he explained.

What would you have done differently at this site to solve the serious/fatal injury problem this intersection had? Not to mention the capacity issues it was also suffering from. An interchange is out of the question, as is closing the intersection. A larger circle wouldn't solve the failure to yield problems. Wisconsin already has a yielding to trucks law on the books. Any signal-related improvements would have cost the taxpayers the added expense of at least 3 viable commercial businesses. And don't feed the same tired IIHS crap again; we are all well-aware that the data is out of date. Any engineer worth their salt is not using that data anymore.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 04, 2018, 03:39:34 PM
What would you have done differently at this site to solve the serious/fatal injury problem this intersection had? Not to mention the capacity issues it was also suffering from. An interchange is out of the question, as is closing the intersection. A larger circle wouldn't solve the failure to yield problems. Wisconsin already has a yielding to trucks law on the books. Any signal-related improvements would have cost the taxpayers the added expense of at least 3 viable commercial businesses. And don't feed the same tired IIHS crap again; we are all well-aware that the data is out of date. Any engineer worth their salt is not using that data anymore.
Each concept has its limitations. At some point in this thread I compared roundabout with a turn on red (mandatory RTOR, not optional as it is in most cases)- which I still think to be a good comparison. You also need to yield to traffic on the left before taking off.
Now, 3-lane roundabouts are equivalent to making RTOR from third lane - and many states don't allow RTOR even from the second lane - for safety reasons. So even 2-lane roundabouts seems to be pushing established safety limits.
As for throughput, a german guideline showing maximum roundabout traffic at 30k/day was referenced in this thread (and everyone reference european roundabouts as example). I myself had to commute through a 50k/day traffic light intersection for a few years. It was pushing in terms of throughput - but not in terms of safety...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 04, 2018, 03:42:03 PM
What would you have done differently at this site to solve the serious/fatal injury problem this intersection had?

What serious/fatal injury problem?  I have not once heard officials cite how many injury crashes there were at the Northland and Richmond intersection before the roundabout was built.  The 2014 Appleton Annual Crash overview only lists the total number of crashes per intersection and doesn’t break it down by injury crashes.  All I gather is there were 27 total crashes at the Nothland and Richmond intersection in 2014…. zero could have involved injuries or all 27 could have involved injuries.  It's pure speculation that the roundabout has helped reduce injury crashes at the intersection.  What I do know is city officials kept highlighting that Northland and Richmond was the most crash prone intersection in their city and they alluded that the proposed roundabout would help fix the high crash rate.  Here are snippets from an article before the roundabout was built:

Quote
Mike Hardy, Asst. Traffic Director with the City of Appleton, said, "[The intersection has a] very high accident rate, a lot of crashes compared to the amount of traffic that's going through there."  To fix the issues, the city, county, and state are working together to build a roundabout. But not before some bumps in the road-- starting this week with utility work, causing some lane closures.
http://fox11online.com/news/local/fox-cities/first-phase-of-new-roundabout-construction-at-northlandrichmond-starts-in-appleton

If Mike was so concerned about the high crash rate at the Northland and Richmond intersection, he didn’t do a very good job fixing the problem.  The city took the most crash prone intersection in their city and magnified the problem several fold.  Now there is a VERY VERY VERY VERY VERY VERY high crash rate at the new roundabout.  Great job Mike.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on February 04, 2018, 05:12:07 PM
What would you have done differently at this site to solve the serious/fatal injury problem this intersection had?

What serious/fatal injury problem?  I have not once heard officials cite how many injury crashes there were at the Northland and Richmond intersection before the roundabout was built.  The 2014 Appleton Annual Crash overview only lists the total number of crashes per intersection and doesn’t break it down by injury crashes.  All I gather is there were 27 total crashes at the Nothland and Richmond intersection in 2014…. zero could have involved injuries or all 27 could have involved injuries.  It's pure speculation that the roundabout has helped reduce injury crashes at the intersection.  What I do know is city officials kept highlighting that Northland and Richmond was the most crash prone intersection in their city and they alluded that the proposed roundabout would help fix the high crash rate.

Thank you for cherry-picking what you will answer. How about tackling the rest of my question:
What would you have done differently at this site to solve the serious/fatal injury problem this intersection had? Not to mention the capacity issues it was also suffering from. An interchange is out of the question, as is closing the intersection. A larger circle wouldn't solve the failure to yield problems. Wisconsin already has a yielding to trucks law on the books. Any signal-related improvements would have cost the taxpayers the added expense of at least 3 viable commercial businesses.

As for "what serious/fatal injury problem," you have been privy to the same information I have had access to. I was going based on what APD has said in various comments, as well comments from the locals in this and previous stories that have run in the media. You have no problem speculating future crash rates, but have issues speculating their severity??
Title: Re: Crash prone 'modern roundabouts'
Post by: Hurricane Rex on February 05, 2018, 01:17:19 AM
And In my humble opinion, this is turning into a back and forth argument. :ded:
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 10, 2018, 09:19:08 PM
On October 13th 2008 the DJIA had it's largest daily points increase on record rising 936 points.  Sounds great right?  Well considering the DJIA had plunged 3,000 points in the previous 8 trading days, that rise wasn't really that impressive.  The 936 rise was nothing more than a dead cat bounce as the DJIA continued to trend downward before bottoming out in March 2009.  The point is you got to look at the context of any event.  Should we be impressed that the latest data shows a slight reduction in the crash rate at the roundabout when compared to the crash rate when the roundabout first opened - even though the current roundabout crash rate is still several times higher than the signalized intersection it replaced?  You are focusing on the "dead cat bounce" and ignoring the overall failure of the roundabout in reducing the crash rate.

Congrats on the talent of being able to see the future. Any stock tips you'd like to share?

I made that DJIA analogy the day BEFORE it dropped 1,175 points on February 5th, the largest points drop in the markets 122 year history.  Maybe i have a pulse on the markets more than you realize.  Similarly, i'm making these roundabout crash predictions BEFORE the roundabouts open.  Admit that Appleton city leaders claimed that the roundabout would reduce the number of crashes at the intersection.  Now that the roundabout is open and there is insanely high number of crashes, they change the argument and say that the roundabout has reduced the number of injury crashes - even though they provide no proof that this is true.  To date nobody has detailed the number of injury crashes at the intersection BEFORE the roundabout opened.  Until you can do that, i don't know that the roundabout is safer.  Ultimately the roundabout has failed to do what it was suppose to do.. and there are more crashes now than ever before.

Was traffic really backing up that badly before the Appleton roundabout and has the roundabout really helped improve traffic flow?  Maybe the roundabout is helping push traffic through better than the traffic signal but it comes at a tremendous cost.  Agencies don't want to see an intersection go from 27 crashes per year to 127 crashes per year.  But the only way they will be able to fix the crash problem is by downsizing the roundabout.. then the roundabout is moving less traffic through it and causing more backups.  It's a catch 22.  Case in point the Jacaranda roundabout in Venice, Florida.  To solve a crash problem they removed circulating lanes inside the roundabout.  Now that the circulating lanes have been removed, there is question to how much traffic volumes the roundabout can handle.  That roundabout has been a thorn in the side of that community for years.. and the problems it has caused isn't going away anytime soon.  I highly doubt they will be redesigning that roundabout again... they are just going to rip it out eventually.  I wouldn't be surprised if the Appleton roundabout shares the same history as the Jacaranda roundabout... where they fumble and F#$@ around with it for years to try to fix a crash problem... only to have to rip it out once it becomes ineffective at pushing traffic through it. 

Is it the end of the road for Venice's Jacaranda roundabout?
http://www.mysuncoast.com/news/is-it-the-end-of-the-road-for-venice-s/article_cb365e96-0c5e-11e8-ae2c-4be135dac9d0.html
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 15, 2018, 05:31:32 PM
Does anyone have any info on the Clearwater Beach roundabout? It was constructed in the late 90s, originally with a water feature. But the water feature was replaced by open grass in late 2002:

(http://www.k-state.edu/roundabouts/ada/photos/clearwater1.jpg) (http://www.tbo.com/storyimage/TB/20151115/ARTICLE/151119449/AR/0/AR-151119449.jpg)

This article (http://www.sptimes.com/2002/12/26/NorthPinellas/In_roundabout_way__fo.shtml) indicates that it was removed due to maintenance costs (something that roundabouts tend to have very little of), but I don't see why it was that big of a deal. The whole point of the fountain was to create a greeting to Clearwater Beach; was the price of welcoming guests really $250k/year?

To be honest, I'm wondering if they removed it because people kept driving into it. I'm skeptical that maintenance was the only reason.

Also wouldn't mind knowing why the roundabout is still marked in such a way that the left approach lane is only a U-turn (even though markings indicate both lanes head towards South Beach).

Here's a photo of the roundabout under construction in 1999. Not much of an apron, here:

(http://www.tbo.com/storyimage/TB/20151115/ARTICLE/151119449/EP/1/1/EP-151119449.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 15, 2018, 06:00:16 PM
Does anyone have any info on the Clearwater Beach roundabout? It was constructed in the late 90s, originally with a water feature. But the water feature was replaced by open grass in late 2002:
Some quite harsh words in this article:
https://www.abcactionnews.com/news/region-north-pinellas/clearwater/project-aims-to-ease-traffic-nightmare-heading-to-clearwater-beach
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 15, 2018, 06:17:57 PM
Does anyone have any info on the Clearwater Beach roundabout? It was constructed in the late 90s, originally with a water feature. But the water feature was replaced by open grass in late 2002:

Some quite harsh words in this article:
https://www.abcactionnews.com/news/region-north-pinellas/clearwater/project-aims-to-ease-traffic-nightmare-heading-to-clearwater-beach

I'm not sure this is related.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on February 15, 2018, 10:57:37 PM
Does anyone have any info on the Clearwater Beach roundabout? It was constructed in the late 90s, originally with a water feature. But the water feature was replaced by open grass in late 2002:

This article (http://www.sptimes.com/2002/12/26/NorthPinellas/In_roundabout_way__fo.shtml) indicates that it was removed due to maintenance costs (something that roundabouts tend to have very little of), but I don't see why it was that big of a deal. The whole point of the fountain was to create a greeting to Clearwater Beach; was the price of welcoming guests really $250k/year?

To be honest, I'm wondering if they removed it because people kept driving into it. I'm skeptical that maintenance was the only reason.

I seem to recall hearing that winds tended to blow water across the roundabout, causing vision and traction issues.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 16, 2018, 01:29:02 AM
Does anyone have any info on the Clearwater Beach roundabout? It was constructed in the late 90s, originally with a water feature. But the water feature was replaced by open grass in late 2002:

This article (http://www.sptimes.com/2002/12/26/NorthPinellas/In_roundabout_way__fo.shtml) indicates that it was removed due to maintenance costs (something that roundabouts tend to have very little of), but I don't see why it was that big of a deal. The whole point of the fountain was to create a greeting to Clearwater Beach; was the price of welcoming guests really $250k/year?

To be honest, I'm wondering if they removed it because people kept driving into it. I'm skeptical that maintenance was the only reason.

I seem to recall hearing that winds tended to blow water across the roundabout, causing vision and traction issues.

That seems like a legitimate concern, especially since the fountain was raised above street level. I know of one other roundabout with a lake/water feature in Florida (not sure of exact location) but the water level is well below street level, so blowing water wouldn't be an issue.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 16, 2018, 04:21:55 PM
I heard there are upwards to 60,000 vehicles per day driving through the Clearwater Beach roundabout during spring break.  That's entirely too much traffic to push through a roundabout in my humble opinion.  You are asking 60,000 drivers to find a safe gap in traffic to enter the roundabout and not screw up.  Here is some great high definition drone footage of the heavily traveled Clearwater Beach roundabout.

Not a valid vimeo URL
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 16, 2018, 04:31:22 PM
I heard there are upwards to 60,000 vehicles per day driving through the Clearwater Beach roundabout during spring break. That's entirely too much traffic to push through a roundabout in my humble opinion.  You are asking 60,000 drivers to find a safe gap in traffic to enter the roundabout and not screw up.  Here is some great high definition drone footage of the heavily traveled Clearwater Beach roundabout.

https://player.vimeo.com/video/210932002

There are times when a roundabout may not seem to be a great idea (such as from a technical standpoint), but is the best decision for other reasons. In the case of the Clearwater Beach roundabout, the alternative would be a large signalised intersection that would have to include U-turns (due to the various two-lane intersecting roads). You'd have several signals strung or mounted overhead, creating overhead "visual pollution", and it wouldn't be particularly inviting for pedestrians (not without grade-separated crossings at least).

This may all sound like total rubbish, but when your city exists because of tourism, you have to consider more than just the technical operations of an intersection.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 16, 2018, 04:50:17 PM
There are times when a roundabout may not seem to be a great idea (such as from a technical standpoint), but is the best decision for other reasons. In the case of the Clearwater Beach roundabout, the alternative would be a large signalised intersection that would have to include U-turns (due to the various two-lane intersecting roads). You'd have several signals strung or mounted overhead, creating overhead "visual pollution", and it wouldn't be particularly inviting for pedestrians (not without grade-separated crossings at least).

This may all sound like total rubbish, but when your city exists because of tourism, you have to consider more than just the technical operations of an intersection.

Yeah that's true.  The city was probably more concerned about creating a grandiose entrance to their beach than anything else.  It's just ironic that within a few years of building that grandiose statue in the middle of the roundabout they ripped it out.  While the city may lack foresight, they definitely don't lack money if they can afford to keep revamping the roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 16, 2018, 05:00:54 PM
This may all sound like total rubbish, but when your city exists because of tourism, you have to consider more than just the technical operations of an intersection.
As if half a mile of traffic backup is a better welcome..
Quote
creating overhead "visual pollution",
(http://gifimage.net/wp-content/uploads/2017/10/bullshit-meter-gif-4.gif)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 16, 2018, 05:39:26 PM
This may all sound like total rubbish, but when your city exists because of tourism, you have to consider more than just the technical operations of an intersection.

As if half a mile of traffic backup is a better welcome..

Well, last I checked, most signalised intersections have at least one approach stopped at all times, so a signal wouldn't necessarily be a massive improvement. A major issue here is the number of vehicles, period. There isn't a visually-appropriate option for this junction that would also improve traffic flow. My suggestion? Improve non-vehicle access (being done right now with bus lanes).

At least, with the roundabout, the line of cars is always moving. And, since all the cars (that aren't crashing) are moving relatively slow, you don't have vehicles very loudly pulling away from an intersection (when the light turns from red to green).

There are times when a roundabout may not seem to be a great idea (such as from a technical standpoint), but is the best decision for other reasons. In the case of the Clearwater Beach roundabout, the alternative would be a large signalised intersection that would have to include U-turns (due to the various two-lane intersecting roads). You'd have several signals strung or mounted overhead, creating overhead "visual pollution", and it wouldn't be particularly inviting for pedestrians (not without grade-separated crossings at least).

This may all sound like total rubbish, but when your city exists because of tourism, you have to consider more than just the technical operations of an intersection.

Yeah that's true.  The city was probably more concerned about creating a grandiose entrance to their beach than anything else.  It's just ironic that within a few years of building that grandiose statue in the middle of the roundabout they ripped it out.  While the city may lack foresight, they definitely don't lack money if they can afford to keep revamping the roundabout.

Well, if their statement about maintenance costs is to be believed (fountain being too expensive), that may not necessarily be true. And all things considered, not much has changed at this roundabout for over a decade. Even the out-of-date markings remain from the early 2000s. I see some new signalised pedestrian crossings. Perhaps this may help meter the entrances.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 16, 2018, 06:00:25 PM

Well, last I checked, most signalised intersections have at least one approach stopped at all times, so a signal wouldn't necessarily be a massive improvement. A major issue here is the number of vehicles, period. There isn't a visually-appropriate option for this junction that would also improve traffic flow. My suggestion? Improve non-vehicle access (being done right now with bus lanes).

At least, with the roundabout, the line of cars is always moving. And, since all the cars (that aren't crashing) are moving relatively slow, you don't have vehicles very loudly pulling away from an intersection (when the light turns from red to green).
Looking at things from the other perspective - with traffic light, you have a guaranteed time to go through the intersection in terms of queue length and cars per cycle - if there are no downstream problems. Roundabout has no guarantee whatsoever. You can end up waiting tens of minutes (my personal record is 15 minutes being 3 car in line ).  And from my experience , traffic lights handle high traffic better than roundabouts.
Alternatives - I have no idea about traffic pattern, so no opinion about bus lanes. But looking at the satellite photos, sardines in a can have plenty of space compared to that area. My only drive around Tampa area was... well, NYC can be worse on a bad day...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 16, 2018, 06:23:00 PM
Well, last I checked, most signalised intersections have at least one approach stopped at all times, so a signal wouldn't necessarily be a massive improvement. A major issue here is the number of vehicles, period. There isn't a visually-appropriate option for this junction that would also improve traffic flow. My suggestion? Improve non-vehicle access (being done right now with bus lanes).

At least, with the roundabout, the line of cars is always moving. And, since all the cars (that aren't crashing) are moving relatively slow, you don't have vehicles very loudly pulling away from an intersection (when the light turns from red to green).

Looking at things from the other perspective - with traffic light, you have a guaranteed time to go through the intersection in terms of queue length and cars per cycle - if there are no downstream problems. Roundabout has no guarantee whatsoever. You can end up waiting tens of minutes (my personal record is 15 minutes being 3 car in line ).  And from my experience , traffic lights handle high traffic better than roundabouts.

Traffic lights handle high volumes better than roundabouts. I agree with that. But, you can improve the flow of a high-volume roundabout by changing a few things, like metering an entrance.
Title: Re: Crash prone 'modern roundabouts'
Post by: Tarkus on February 17, 2018, 06:58:55 PM
The geniuses behind the MLK Pkwy/Hayden Bridge Road roundabout in Springfield, Oregon that averages ~40 wrecks per year are back at it . . . they're stuffing 5 roundabouts (http://newfranklinblvd.org/wp-content/uploads/2014/02/Franklin_Display-Aerial-4-12-16.jpg) on Franklin Boulevard between I-5 and the Willamette--a road they appear to have cherry-stem annexed.   :ded:

On the plus side, they're only 2x1s, unlike MLK/Hayden Bridge, but that second one that seems to intersect absolutely nothing next to the easternmost one (McVay Highway) seems completely pointless.
Title: Re: Crash prone 'modern roundabouts'
Post by: ftballfan on February 19, 2018, 01:04:46 PM
This three-roundabout system at US-23, Old US-23, and Lee Rd in Brighton, MI looks like an accident waiting to happen: https://www.google.com/maps/@42.5062722,-83.7593041,941m/data=!3m1!1e3?hl=en
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 19, 2018, 03:57:44 PM
This three-roundabout system at US-23, Old US-23, and Lee Rd in Brighton, MI looks like an accident waiting to happen: https://www.google.com/maps/@42.5062722,-83.7593041,941m/data=!3m1!1e3?hl=en

We've posted about this one before. They're scaling it back, if I recall correctly. One of the older 3-lane roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 19, 2018, 05:24:04 PM
This three-roundabout system at US-23, Old US-23, and Lee Rd in Brighton, MI looks like an accident waiting to happen: https://www.google.com/maps/@42.5062722,-83.7593041,941m/data=!3m1!1e3?hl=en

Those roundabouts are accidents that have already happened.  The Lee Road roundabouts had 40 injury crashes from 2011-2016, which is the most injury crashes of any intersection in Livingston County during that six-year time period.  As a comparison, the SPUI at US-23/M-59 carries more traffic than the Lee Road roundabouts yet that intersection didn't even crack the top 5 worst intersections for injury crashes.  As Jake alluded to, they are going to downscale the Lee Road roundabout at a cost of $1.1 million.  Let's just hope the reduced roundabout capacity doesn't cause traffic to back up onto the freeway.

Livingston County's worst intersections for injury crashes
https://www.livingstondaily.com/story/news/local/community/livingston-county/2017/02/10/livingston-countys-worst-intersections-injury-crashes/97607006/

$1.1M project will change crash-prone Lee Road roundabout
https://www.livingstondaily.com/story/news/local/community/livingston-county/2018/01/08/1-1-m-project-change-crash-prone-lee-road-shrinking-3-lane-roundabout-lee-road-reduce-crashes-confus/988173001/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 23, 2018, 12:48:01 PM
The geniuses behind the MLK Pkwy/Hayden Bridge Road roundabout in Springfield, Oregon that averages ~40 wrecks per year are back at it . . . they're stuffing 5 roundabouts (http://newfranklinblvd.org/wp-content/uploads/2014/02/Franklin_Display-Aerial-4-12-16.jpg) on Franklin Boulevard between I-5 and the Willamette--a road they appear to have cherry-stem annexed.   :ded:

On the plus side, they're only 2x1s, unlike MLK/Hayden Bridge, but that second one that seems to intersect absolutely nothing next to the easternmost one (McVay Highway) seems completely pointless.

This is somebody getting a hard on for roundabouts and trying to stuff as many as possible in their project.  I agree with you that the roundabout just west of the McVay roundabout seems totally unnecessary.  In the concept picture the roundabout doesn't service any drives so I'm really at a loss the purpose of that roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 02, 2018, 03:29:01 PM
The Northland and Richmond roundabout in Appleton opened on September 1.  According to Appleton Police there have been 25 reported crashes between August 31st and October 10th.  At the current crash rate, there will be 228 crashes at the roundabout in the first year of operation.  Compare that to 27 crashes in all of 2014 when it was a signalized intersection (the highest crash intersection in Appleton that year).  On the project website, the stated reason the roundabout was selected was to address the high rate of crashes that were occurring at the signaled intersection.  This is the design they came up with.

(http://static-20.sinclairstoryline.com/resources/media/e5ea2b53-be3b-4ca3-96c9-6ef588ec9840-large16x9_47ooRab.jpg)

So after 25 crashes in just 40 days, does anyone still think the roundabout will do a good job at reducing crashes at the intersection moving forward?  While there probably won't be 228 crashes per year, this roundabout could easily see 100+ crashes per year.  Their baseline is 27 crashes, and 100+ crashes is about 4X worse than that.  As long as this roundabout remains a complex 3x2 roundabout next to a busy commercial district, crashes will remain a problem.  But fear not, they will study the roundabout and throw hundreds of thousands of additional dollars to “fix”  the roundabout that they just completed.  Good job.

Crash numbers increase in new roundabout
http://fox11online.com/news/local/crash-numbers-increase-in-new-roundabout


After 155 days of opening, there have been 77 crashes at the new Northland and Richmond roundabout in Appleton (compared to 27 crashes/yr before the roundabout).  At the current crash rate there will be 181 crashes in the first year of operation.  The city is already attempting to "fix" the 155 day old roundabout by adding new signage.  Doubt it will be too effective...my prediction is that in a year or two, the city will eliminate a circulating lane inside the roundabout at a significant cost to the people of Appleton. 

Crashes continue in Appleton roundabout
http://fox11online.com/news/local/crashes-continue-in-appleton-roundabout

Here is drone footage of the newly opened Richmond/Northland roundabout in Appleton.  The complexity of crossing through this roundabout might be equivalent to completing level 1 of Frogger.  Ask 40-50k people (roughly the traffic volume of this roundabout) to complete level 1 of Frogger and see how many misjudge the "gap" and end up with a dead frog.

Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on March 02, 2018, 08:45:50 PM
What's to learn?  Yield to traffic to left.  Simple as that.   The video shows smoothly flowing traffic.
Title: Re: Crash prone 'modern roundabouts'
Post by: Brian556 on March 02, 2018, 10:55:04 PM
Notice the strange yellow markings in this roundabout:
https://www.google.com/maps/place/Weeki+Wachee,+FL/@28.8433589,-82.0165501,93m/data=!3m1!1e3!4m5!3m4!1s0x88e820349a7e9b51:0x3ee81b3447a5426c!8m2!3d28.5155513!4d-82.5728769 (https://www.google.com/maps/place/Weeki+Wachee,+FL/@28.8433589,-82.0165501,93m/data=!3m1!1e3!4m5!3m4!1s0x88e820349a7e9b51:0x3ee81b3447a5426c!8m2!3d28.5155513!4d-82.5728769)
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on March 02, 2018, 11:37:47 PM
Looks like the roundabout itself was built for two lanes east/west, but that's it. The western approach definitely can only fit a single lane.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on March 03, 2018, 12:28:30 AM
Notice the strange yellow markings in this roundabout:
https://www.google.com/maps/place/Weeki+Wachee,+FL/@28.8433589,-82.0165501,93m/data=!3m1!1e3!4m5!3m4!1s0x88e820349a7e9b51:0x3ee81b3447a5426c!8m2!3d28.5155513!4d-82.5728769 (https://www.google.com/maps/place/Weeki+Wachee,+FL/@28.8433589,-82.0165501,93m/data=!3m1!1e3!4m5!3m4!1s0x88e820349a7e9b51:0x3ee81b3447a5426c!8m2!3d28.5155513!4d-82.5728769)
Looks like an older roundabout design (or a newer roundabout created by an inexperienced designer), where the central island is kept perfectly circular, despite having an unbalanced number of lanes. The paint is there to [awkwardly] take up the extra space. Here's one of a similar design -- one that falls into the older roundabout category: https://goo.gl/maps/Eq6FqzdHn1K2 (https://goo.gl/maps/Eq6FqzdHn1K2).

If they were adamant about keeping a perfectly circular central island, they should have left the yellow hatching off and instead pulled the splitter islands inward, creating a more natural path for the single-lane entries.

This is more like what an unbalanced 2x1 should look like: https://goo.gl/maps/C8MFZxqwzaE2 (https://goo.gl/maps/C8MFZxqwzaE2)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on March 03, 2018, 03:28:01 AM
This is more like what an unbalanced 2x1 should look like: https://goo.gl/maps/C8MFZxqwzaE2 (https://goo.gl/maps/C8MFZxqwzaE2)

Of course, if enough asphalt was laid to support a 2x2 layout, marking styles like this would also be appropriate:

(https://i.imgur.com/GlYjP2o.png) (https://i.imgur.com/9V1u4JQ.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: Brian556 on March 03, 2018, 08:03:12 AM
Notice the strange yellow markings in this roundabout:
https://www.google.com/maps/place/Weeki+Wachee,+FL/@28.8433589,-82.0165501,93m/data=!3m1!1e3!4m5!3m4!1s0x88e820349a7e9b51:0x3ee81b3447a5426c!8m2!3d28.5155513!4d-82.5728769 (https://www.google.com/maps/place/Weeki+Wachee,+FL/@28.8433589,-82.0165501,93m/data=!3m1!1e3!4m5!3m4!1s0x88e820349a7e9b51:0x3ee81b3447a5426c!8m2!3d28.5155513!4d-82.5728769)
Looks like an older roundabout design (or a newer roundabout created by an inexperienced designer), where the central island is kept perfectly circular, despite having an unbalanced number of lanes. The paint is there to [awkwardly] take up the extra space. Here's one of a similar design -- one that falls into the older roundabout category: https://goo.gl/maps/Eq6FqzdHn1K2 (https://goo.gl/maps/Eq6FqzdHn1K2).

If they were adamant about keeping a perfectly circular central island, they should have left the yellow hatching off and instead pulled the splitter islands inward, creating a more natural path for the single-lane entries.

This is more like what an unbalanced 2x1 should look like: https://goo.gl/maps/C8MFZxqwzaE2 (https://goo.gl/maps/C8MFZxqwzaE2)
Its relatively new. I'd say it no more than 10 years old
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 09, 2018, 10:44:13 AM
Quote
Studies of single-lane roundabouts reported reductions in injury and overall crashes, which typically occur at a slow speed and include side swipes and fender benders and greatly reduce the chance of deadly head-on or T-bone accidents. However, non-injury crashes are sometimes more frequent on multi-lane roundabouts, due in part to driver confusion.
https://www.lmtonline.com/local/article/Statistics-show-roundabouts-safer-than-12816432.php

More fake news.  It's not just about what they report, but what they decide to leave out.  When looking at available crash data, every 2x2 or higher roundabout constructed in America has seen increases in total crashes.  And many of these complex multi-lane roundabouts have also seen increases in INJURY crashes!  Several Dual Lane Roundabouts analyzed in a recent Minnesota study found a 6% increase in injury crashes.  This sentence would have been less propaganda, and more reality. 

“However, non-injury crashes are oftentimes more frequent on multi-lane roundabouts, and sometimes lead to increases in injury crashes” .
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 13, 2018, 02:54:31 AM
Smelly incident in Lacey, WA today. Manure truck tipped over in the Pacific Ave/Marvin Road roundabout. Apparently there was a mechanical failure which, combined with the G-forces of the roundabout, caused it to lose its load.

(https://i.imgur.com/jd3eTzw.png)

https://twitter.com/theolympian/status/984547950561902592
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 13, 2018, 10:04:48 AM
A motorcyclist was killed in Lawrence, Indiana early today after failing to negotiate a roundabout.

Motorcyclist killed in roadway roundabout traffic accident
http://fox59.com/2018/04/13/motorcyclist-killed-in-east-side-roundabout-traffic-accident/
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 13, 2018, 11:24:42 AM
A motorcyclist was killed in Lawrence, Indiana early today after failing to negotiate a roundabout.

Motorcyclist killed in roadway roundabout traffic accident
http://fox59.com/2018/04/13/motorcyclist-killed-in-east-side-roundabout-traffic-accident/
Seriously, this is just one of 100 fatal accidents which happened yesterday.
Posting statistics makes sense; somewhat special accidents (like manure truck  :awesomeface:) make some sense. Routine crashes... we know that they happen..
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on April 13, 2018, 11:58:40 AM
Posting statistics makes sense; somewhat special accidents (like manure truck  :awesomeface:) make some sense.

It took shitting on roundabouts to a whole new, literal level. :bigass: :awesomeface:
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 13, 2018, 12:03:43 PM
Posting statistics makes sense; somewhat special accidents (like manure truck  :awesomeface:) make some sense.

It took shitting on roundabouts to a whole new, literal level. :bigass: :awesomeface:
Actually an idea - how about "unusual accidents" thread?
Two candidates in this thread - manure and tar spill; I vague remember accidents involving lots of bees; pigs; coins....
Title: Re: Crash prone 'modern roundabouts'
Post by: Mr_Northside on April 13, 2018, 03:48:18 PM
Posting statistics makes sense; somewhat special accidents (like manure truck  :awesomeface:) make some sense.

It took shitting on roundabouts to a whole new, literal level. :bigass: :awesomeface:

(https://metaldetectingforum.com/attachment.php?attachmentid=382457&d=1492041723)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 13, 2018, 04:30:56 PM
Posting statistics makes sense; somewhat special accidents (like manure truck  :awesomeface:) make some sense.

It took shitting on roundabouts to a whole new, literal level. :bigass: :awesomeface:

(https://metaldetectingforum.com/attachment.php?attachmentid=382457&d=1492041723)

The facebook comments on the crash were full of BTTF references. Hell, I'm pretty sure that's the only reason it's funny.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 16, 2018, 03:18:45 PM
A motorcyclist was killed in Lawrence, Indiana early today after failing to negotiate a roundabout.

Motorcyclist killed in roadway roundabout traffic accident
http://fox59.com/2018/04/13/motorcyclist-killed-in-east-side-roundabout-traffic-accident/
Seriously, this is just one of 100 fatal accidents which happened yesterday.
Posting statistics makes sense; somewhat special accidents (like manure truck  :awesomeface:) make some sense. Routine crashes... we know that they happen..

Another fatal motorcycle crash at a Delaware roundabout just two days after the Lawrence, Indiana fatality.  I wouldn't say fatal crashes at intersections are routine.  According to the FHWA there were 2,924 fatal crashes at roughly 300,000 signalized intersections in 2007.  If you believe those FHWA’s stats, traffic signals average a fatal crash about every 100 years.  Here's the Delaware news story...

Motorcyclist killed in roundabout near Bear
https://www.delawareonline.com/story/news/crime/2018/04/15/motorcyclist-killed-roundabout-near-bear/518767002/

Now we are told that roundabouts reduce fatalities by 90%.  Believing those stats, if all 300,000 traffic signals in America were converted to roundabouts, we would see about 300 deaths per year (as opposed to 3000 deaths if they remained signalized intersections).   If that’s the case, a roundabout would average a fatal crash about every 1,000 years.  The Delaware roundabout where the fatal motorcyclist crash occurred was constructed last year.  Do we expect not to see another fatal crash at this roundabout for the next 999 years?  The IIHS claim that roundabouts reduce fatalities by 90% is a fabrication.  While i do believe roundabouts reduce fatalities overall compared to signalized intersections, i don't think it's anywhere near the 90% the IIHS has claimed.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 16, 2018, 03:41:59 PM
A motorcyclist was killed in Lawrence, Indiana early today after failing to negotiate a roundabout.

Motorcyclist killed in roadway roundabout traffic accident
http://fox59.com/2018/04/13/motorcyclist-killed-in-east-side-roundabout-traffic-accident/
Seriously, this is just one of 100 fatal accidents which happened yesterday.
Posting statistics makes sense; somewhat special accidents (like manure truck  :awesomeface:) make some sense. Routine crashes... we know that they happen..

Another fatal motorcycle crash at a Delaware roundabout just two days after the Lawrence, Indiana fatality.  I wouldn't say fatal crashes at intersections are routine.  According to the FHWA there were 2,924 fatal crashes at roughly 300,000 signalized intersections in 2007.  If you believe those FHWA’s stats, traffic signals average a fatal crash about every 100 years.  Here's the Delaware news story...

Motorcyclist killed in roundabout near Bear
https://www.delawareonline.com/story/news/crime/2018/04/15/motorcyclist-killed-roundabout-near-bear/518767002/

Now we are told that roundabouts reduce fatalities by 90%.  Believing those stats, if all 300,000 traffic signals in America were converted to roundabouts, we would see about 300 deaths per year (as opposed to 3000 deaths if they remained signalized intersections).   If that’s the case, a roundabout would average a fatal crash about every 1,000 years.  The Delaware roundabout where the fatal motorcyclist crash occurred was constructed last year.  Do we expect not to see another fatal crash at this roundabout for the next 999 years?  The IIHS claim that roundabouts reduce fatalities by 90% is a fabrication.  While i do believe roundabouts reduce fatalities overall compared to signalized intersections, i don't think it's anywhere near the 90% the IIHS has claimed.
To properly answer your question, a total number of roundabouts in US would be useful. It is always about numbers - and properly dealing with them.
(https://imgs.xkcd.com/comics/extrapolating.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 16, 2018, 04:38:00 PM
In a previous post, I attempted to estimate the number of fatal crashes per roundabout in the US for 2017.  My estimate came to 0.0033 fatalities per roundabout.  This is comparable to FHWA published data for the number of fatalities per roundabout in the U.S. between 2005 and 2013.  Keep in mind the IIHS made the claim that roundabouts reduce fatal crash by 90% way back in 2000.  There is a lot more data available today to sift through that proves the IIHS claim back then was wrong.  You just aren’t seeing 90% reductions in fatalities at roundabouts in America.

News reports for fatal roundabout crashes that occurred in 2017. 

http://www.sun-sentinel.com/local/broward/fl-boca-man-dies-in-parkland-crash-20170117-story.html
http://www.theledger.com/news/20170208/teen-faces-manslaughter-charge-after-girl-dies-in-crash-following-chase-with-lpd-officer
http://www.wdbj7.com/content/news/60-year-old-Roanoke-County-woman-dies-in-motorcycle-crash-413537653.html
http://www.fox9.com/news/unbelted-man-dies-in-chisago-county-crash-friday-afternoon
http://www.wcsh6.com/news/local/fatal-crash-closes-rte-114-bypass-in-gorham/433810393
http://www.toledoblade.com/Police-Fire/2017/04/30/Alcohol-believed-to-be-factor-in-fatal-Springfield-Twp-crash.html
http://www.gainesville.com/news/20170502/roundabout-crash-kills-two-police-say
http://www.bellinghamherald.com/news/local/article153269789.html
http://www.cecildaily.com/police_and_fire_beat/article_bed6099c-45a6-5be5-b61d-ec91d893631b.html
http://www.wpta21.com/story/35827071/coroner-identifies-motorcyclist-involved-in-thursday-morning-fatal-crash
http://www.prescottenews.com/index.php/news/current-news/item/30613-37-year-old-man-from-page-dies-in-crash-at-roundabout
http://www.startribune.com/driver-in-st-cloud-roundabout-fatally-hits-pedestrian/453113583/
http://www.lasvegasnow.com/news/one-killed-in-overnight-crash/859083995

This was based on about an hour of google searches and based on this limited research, there were at least 13 fatal roundabouts crashes in 2017 resulting in 14 fatalities.   According to the latest 2013 FHWA estimates, there are roughly 3200 roundabouts in the United States.  I personally have compiled a database of over 5200 roundabouts in America, but I don’t know the exact methodology used to compile the FHWA database.  Let’s split the difference and say there are about 4200 roundabouts in America.   In 2017 each modern roundabout averaged 0.0033 fatal crashes (14 fatalities / 4200 roundabouts).  This ratio is comparable to previous years based on data compiled by the FHWA:
(https://i.imgur.com/6lWCWUu.png)
https://safety.fhwa.dot.gov/intersection/innovative/roundabouts/docs/fhwasa15072.pdf

So how does this ratio compare to signalized intersections?  Based on FHWA data there were 2,924 fatalities at approximately 311,000 signalized intersections in 2007.  Each signal averaged 0.0094 fatal crashes (2,924 fatalities / 311,000 signals). 
https://safety.fhwa.dot.gov/intersection/other_topics/fhwasa10005/brief_2.cfm

Now we can use these ratios to get a sense of how much roundabouts are reducing fatal crashes.  Is it really 90% as the IIHS claims?  To me it looks to be closer to 65% (1-(0.0033/0.0094)).  That’s still a big reduction, but it's not 90%.  And consider that the IIHS claims that roundabouts reduce injury crashes by 76%.  However, Minnesota research found that complex roundabouts in that state actually saw a 6% increase in injury crashes.  The point is there is potentially a subset of modern roundabouts that are increasing fatal crashes, not reducing them.  I'll tell you one subset of roundabouts that are potentially increasing fatal crashes... roundabouts that have retaining walls in the central island.  Do you think it's a coincidence there have been 3 fatalities in the past 10 years at the 96th and Westfield Blvd roundabout in Carmel?  Every time a driver misjudges the roundabout and drive through the middle of it, they smack into a concrete wall.  Boom!  Dead!
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on April 16, 2018, 04:56:35 PM
To continue to say the IIHS data is wrong is disingenuous. The data is outdated, as just about anyone here can agree. It was accurate at the time it was published, given the data available. Can we quit beating this dead horse already? It'd be like Toyota continuing to advertise having the 2000 Truck of the Year.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on April 16, 2018, 06:01:59 PM
To continue to say the IIHS data is wrong is disingenuous. The data is outdated, as just about anyone here can agree. It was accurate at the time it was published, given the data available. Can we quit beating this dead horse already? It'd be like Toyota continuing to advertise having the 2000 Truck of the Year.

As long as this thread remains not locked, the dead horse beating will continue.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 17, 2018, 02:45:02 AM
To continue to say the IIHS data is wrong is disingenuous. The data is outdated, as just about anyone here can agree. It was accurate at the time it was published, given the data available. Can we quit beating this dead horse already? It'd be like Toyota continuing to advertise having the 2000 Truck of the Year.

As long as this thread remains not locked, the dead horse beating will continue.

I don't think locking this thread would be smart. It's become a dumping ground for roundabout news, and any other roundabout threads would almost certainly become a discussion on safety anyways.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on April 17, 2018, 06:00:31 AM
To continue to say the IIHS data is wrong is disingenuous. The data is outdated, as just about anyone here can agree. It was accurate at the time it was published, given the data available. Can we quit beating this dead horse already? It'd be like Toyota continuing to advertise having the 2000 Truck of the Year.
As long as this thread remains not locked, the dead horse beating will continue.
I don't think locking this thread would be smart. It's become a dumping ground for roundabout news, and any other roundabout threads would almost certainly become a discussion on safety anyways.

Right, and I actually agree, for the reasons you stated. All I'm saying is that this thread will always have a component of deceased equine assault in and among the news and actually useful discussion.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 17, 2018, 10:49:18 AM
To continue to say the IIHS data is wrong is disingenuous. The data is outdated, as just about anyone here can agree. It was accurate at the time it was published, given the data available. Can we quit beating this dead horse already? It'd be like Toyota continuing to advertise having the 2000 Truck of the Year.

The IIHS study was never accurate, even at the time of publication.  When nearly half of the multi-lane roundabouts analyzed in the study didn't even have before injury crash data, how can it be taken seriously?  The few remaining multi-lane roundabouts with before injury crash data were along a 25 mph roadway through a ski-resort in Colorado.  It's a joke.  Of course that hasn't stopped agencies from citing the safety statistics found in that IIHS study to gain public support for roundabouts.  Anytime you hear that roundabouts reduce fatalities by 90%, just know you are being lied to.   The study basically admits that the 90% reduction in fatalities number is a WAG...  a Wild Ass Guess.

Quote
Effects on fatal crashes and those causing incapacitating injuries are more difficult to measure due to the small samples, but indications are that such crashes were substantially reduced. For the 20 converted intersections with injury data, there were 3 fatal crashes during the before period and none during the after period. The fatal crashes may have contributed to the fact that the roundabouts were constructed and may therefore contribute to the regression-to-the-mean phenomenon.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on April 17, 2018, 11:39:51 AM
To continue to say the IIHS data is wrong is disingenuous. The data is outdated, as just about anyone here can agree. It was accurate at the time it was published, given the data available. Can we quit beating this dead horse already? It'd be like Toyota continuing to advertise having the 2000 Truck of the Year.

As long as this thread remains not locked, the dead horse beating will continue.

I don't think locking this thread would be smart. It's become a dumping ground for roundabout news, and any other roundabout threads would almost certainly become a discussion on safety anyways.

Agree, there's no reason to lock the thread, and it has become a dumping ground lately...for one-off news reports of fatal crashes. Anyone with a Google news subscription to the term 'roundabout' can get the same info. I'd argue that just seeing that kind of new post dilutes the value of the thread, since we all know these crashes happen on occasion. Where's the thread devoted to reporting crashes at signals, stop signs, or grade crossings? Or are roundabouts the only horse in the race?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 17, 2018, 02:39:29 PM
Over the past week two motorcyclist have been killed in separate roundabout crashes.  At this rate, each roundabout in America would average 0.0208 fatal crashes per year (104 fatalities / 5000 roundabouts).  How does that compare to the number of fatalities at traffic signals?  According to FHWA data, there were 2,924 fatalities at approximately 311,000 signalized intersections in 2007.  This equates to 0.0094 fatal crashes per traffic signal.  So, I could publish a report that concludes that the estimated number of fatal crashes per roundabout in the U.S. is about twice as high as the number of fatal crashes per traffic signal in the U.S.  (0.0208 fatal crashes per roundabout vs. 0.0094 fatal crashes per signal).   
 
DabigE, you would bash me for making safety conclusions based on one week of crash data.   The scope is way too narrow.  But you fail to acknowledge the narrow scope of the 2000 IIHS study.  The only multi-lane roundabouts analyzed in that study (with before/after injury data) was along a 25 mph roadway through a ski-resort in Colorado.  Your only criticism of the 2000 IIHS study is that it’s outdated.  At least my report would only be about a week old.  It's amazing that the safety conclusions from such a weak study could be perpetuated for the next 20 years in an attempt to gain public support for roundabouts in this country, and seemingly smart people like yourself never question it.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on April 17, 2018, 02:59:51 PM
DabigE, you would bash me for making safety conclusions based on one week of crash data.   The scope is way too narrow.  But you fail to acknowledge the narrow scope of the 2000 IIHS study.  The only multi-lane roundabouts analyzed in that study (with before/after injury data) was along a 25 mph roadway through a ski-resort in Colorado.  Your only criticism of the 2000 IIHS study is that it’s outdated.  At least my report would only be about a week old.  It's amazing that the safety conclusions from such a weak study could be perpetuated for the next 20 years in an attempt to gain public support for roundabouts in this country, and seemingly smart people like yourself never question it.

OMFG...I can't tell if you're that dense or just have that selective of a memory. I haven't treated the 2000 IIHS study as the gospel of roundabouts, nor have I thrown the baby out with the bath water. Frankly, I have yet to see a study on roundabouts that doesn't have some level of significant flaw to it, including the recent ones from Wisconsin and Minnesota. Being old is far from my only criticism of the IIHS study; however, that is one of the main reasons why I believe it should stop being quoted...a concept which you can't seem to grasp.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 17, 2018, 04:13:05 PM
So DaBigE, now you do think the 2000 IIHS study is flawed?  Not only flawed, but significantly flawed.  Good to hear you came around from earlier today when you said the study was "accurate".  That was a good laugh. 
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on April 17, 2018, 06:23:58 PM
So DaBigE, now you do think the 2000 IIHS study is flawed?  Not only flawed, but significantly flawed.  Good to hear you came around from earlier today when you said the study was "accurate".  That was a good laugh.

Back to our selective reading and quote twisting once again, I see. And glad I could provide you a laugh...it's probably about time, since you've been making my stomach hurt from laughing so hard lately.

It was accurate at the time it was published, given the data available.

Note the text that was already italicized. In hindsight, I probably should have said "given the data that was used". In any case, at the time, how many roundabouts had fatalities in the US at the time the study was done? How many roundabouts were studied? Given the data the IIHS included, the results of the study were accurate. But that is also how it is flawed...using a limited data set. That is how something can be both accurate and flawed at the same time. :-o

But to one of your other points: If you're going to do a comprehensive study of roundabouts, there's going to be a few which will not have any before crash data, since not all roundabouts are built purely for safety benefits. Unfortunately, that doesn't fit the broad picture you've been attempting to paint for the last 68+ pages. This is when comparing the expected number of crashes vs the actual number of crashes would come into play.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 17, 2018, 07:20:27 PM
The notorious M-5 and Pontiac Trail roundabout has been the most crash prone intersection in Michigan for several years.  Now they are planning a $100 million retail center along the vacant land right next to the roundabout.  I love how Commerce Township supervisor David Scott cites a traffic study stating "This project, surprisingly, creates no traffic problems that didn't already exist."   :-D :awesomeface:  :biggrin:   

Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on April 21, 2018, 10:21:35 AM
It should be noted the motorcyclist who died in Bear, Del was not wearing a helmet. I realize it's always the roundabout's fault. I just thought I'd put it in the permanent record.

Pixel 2

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 23, 2018, 11:47:53 AM
There are calls for a roundabout to be built at Highway 35 and Highway 335 in Saskatchewan, which was the site of the Humboldt Broncos bus tragedy that killed 16 on April 6th.  A flashing light was added to the stop sign in 1997, after a pickup blew through the stop sign into the path of a semi-truck and killed 6 people.  So at least 22 people have died at the stop-controlled intersection over the past 21 years.  That’s obviously a horrible result. 

https://globalnews.ca/news/4156114/highway-roundabouts-alberta-humboldt-broncos-bus-crash/

But adding a sharp curve in the middle of a high-speed rural roadway (ie. a roundabout) is not the way to make the roadway safer IMO.  There are other ways to prevent drivers from crashing into each other beyond adding sharp curves along a rural roadways.  What if the bus driver isn’t paying attention as they approach the rural roundabout, takes the roundabout too fast and flips the bus on its side?  Worse yet.. what if there is a big retaining wall in the middle of the roundabout, and the bus experiences brake failure and strikes the retaining wall head on at 80kph?  OTOH, if it remains a straight section of rural-road, and the bus experiences brake failure, it could fly through the “straight”  intersection at 80kph with no harm, unless if there is another vehicle in the direct path of the bus.  If there is another vehicle in the buses direct path, it can instantly kill 16 people which obviously is a massive tragedy.  So the question becomes how do you prevent the semi-truck from being in the path of the bus at that rural intersection in Saskatchewan?

The answer to the problem, IMO, is connected vehicles.  If the bus driver was warned that a vehicle was approaching the intersection at high speed and a collision avoidance warning was displayed, the driver could have taken evasive action to avoid this deadly crash.  The semi-truck was approaching from the west where there is a line of trees that would have obstructed the bus-drivers view of the approaching semi-truck.  The only way for the bus driver to know that a semi-truck was approaching the intersection is if the two vehicles were communicating with each other.  This connected vehicle technology is already available in some luxtury vehicles, most notably Cadillac’s CTS sedan.  GM is dedicated to advancing this technology, regardless of government mandates (i believe the Trump administration recently reversed the Obama administration's decision that would have mandated auto-makers to include vehicle-2-vehicle communications in new vehicles).
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on April 23, 2018, 02:04:27 PM
There are calls for a roundabout to be built at Highway 35 and Highway 335 in Saskatchewan, which was the site of the Humboldt Broncos bus tragedy that killed 16 on April 6th.  A flashing light was added to the stop sign in 1997, after a pickup blew through the stop sign into the path of a semi-truck and killed 6 people.  So at least 22 people have died at the stop-controlled intersection over the past 21 years.  That’s obviously a horrible result. 

https://globalnews.ca/news/4156114/highway-roundabouts-alberta-humboldt-broncos-bus-crash/

But adding a sharp curve in the middle of a high-speed rural roadway (ie. a roundabout) is not the way to make the roadway safer IMO.  There are other ways to prevent drivers from crashing into each other beyond adding sharp curves along a rural roadways.  What if the bus driver isn’t paying attention as they approach the rural roundabout, takes the roundabout too fast and flips the bus on its side?  Worse yet.. what if there is a big retaining wall in the middle of the roundabout, and the bus experiences brake failure and strikes the retaining wall head on at 80kph?  OTOH, if it remains a straight section of rural-road, and the bus experiences brake failure, it could fly through the “straight”  intersection at 80kph with no harm, unless if there is another vehicle in the direct path of the bus.  If there is another vehicle in the buses direct path, it can instantly kill 16 people which obviously is a massive tragedy.  So the question becomes how do you prevent the semi-truck from being in the path of the bus at that rural intersection in Saskatchewan?

The answer to the problem, IMO, is connected vehicles.  If the bus driver was warned that a vehicle was approaching the intersection at high speed and a collision avoidance warning was displayed, the driver could have taken evasive action to avoid this deadly crash.  The semi-truck was approaching from the west where there is a line of trees that would have obstructed the bus-drivers view of the approaching semi-truck.  The only way for the bus driver to know that a semi-truck was approaching the intersection is if the two vehicles were communicating with each other.  This connected vehicle technology is already available in some luxtury vehicles, most notably Cadillac’s CTS sedan.  GM is dedicated to advancing this technology, regardless of government mandates (i believe the Trump administration recently reversed the Obama administration's decision that would have mandated auto-makers to include vehicle-2-vehicle communications in new vehicles).

That's one hell of a slippery slope and a lot of 'what ifs', yet you forget one big one: What if the connected vehicle technology fails?

What if there's a bus full of little kids coming from all directions and all electronic devices fail, and they're in dense fog?

There is no perfect solution that will prevent every conceivable method of tragedy. A properly designed roundabout is arguably the best low-tech solution, with somewhat-reasonable costs. A grade-separated interchange would be the ultimate solution, but comes at price that likely fails to achieve a reasonable cost-benefit ratio. Connected vehicle technology is only viable once there is significant market saturation. And with the current price of vehicles and how long the average person keeps their car nowadays, that's going to take a long time.

There are many rural, high-speed roundabouts that have achieved their goal of reducing serious-injury and fatal crash events. Most of them fall off your radar since they're single-lane roundabouts. But they also employ sound design practices: physical upstream guidance, approach signing, transitional lighting, and forgiving landscape design.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 23, 2018, 03:56:45 PM
There are calls for a roundabout to be built at Highway 35 and Highway 335 in Saskatchewan, which was the site of the Humboldt Broncos bus tragedy that killed 16 on April 6th.  A flashing light was added to the stop sign in 1997, after a pickup blew through the stop sign into the path of a semi-truck and killed 6 people.  So at least 22 people have died at the stop-controlled intersection over the past 21 years.  That’s obviously a horrible result. 

https://globalnews.ca/news/4156114/highway-roundabouts-alberta-humboldt-broncos-bus-crash/

But adding a sharp curve in the middle of a high-speed rural roadway (ie. a roundabout) is not the way to make the roadway safer IMO.  There are other ways to prevent drivers from crashing into each other beyond adding sharp curves along a rural roadways.  What if the bus driver isn’t paying attention as they approach the rural roundabout, takes the roundabout too fast and flips the bus on its side?  Worse yet.. what if there is a big retaining wall in the middle of the roundabout, and the bus experiences brake failure and strikes the retaining wall head on at 80kph?  OTOH, if it remains a straight section of rural-road, and the bus experiences brake failure, it could fly through the “straight”  intersection at 80kph with no harm, unless if there is another vehicle in the direct path of the bus.  If there is another vehicle in the buses direct path, it can instantly kill 16 people which obviously is a massive tragedy.  So the question becomes how do you prevent the semi-truck from being in the path of the bus at that rural intersection in Saskatchewan?

The answer to the problem, IMO, is connected vehicles.  If the bus driver was warned that a vehicle was approaching the intersection at high speed and a collision avoidance warning was displayed, the driver could have taken evasive action to avoid this deadly crash.  The semi-truck was approaching from the west where there is a line of trees that would have obstructed the bus-drivers view of the approaching semi-truck.  The only way for the bus driver to know that a semi-truck was approaching the intersection is if the two vehicles were communicating with each other.  This connected vehicle technology is already available in some luxtury vehicles, most notably Cadillac’s CTS sedan.  GM is dedicated to advancing this technology, regardless of government mandates (i believe the Trump administration recently reversed the Obama administration's decision that would have mandated auto-makers to include vehicle-2-vehicle communications in new vehicles).

That's one hell of a slippery slope and a lot of 'what ifs', yet you forget one big one: What if the connected vehicle technology fails?

What if there's a bus full of little kids coming from all directions and all electronic devices fail, and they're in dense fog?

There is no perfect solution that will prevent every conceivable method of tragedy. A properly designed roundabout is arguably the best low-tech solution, with somewhat-reasonable costs. A grade-separated interchange would be the ultimate solution, but comes at price that likely fails to achieve a reasonable cost-benefit ratio. Connected vehicle technology is only viable once there is significant market saturation. And with the current price of vehicles and how long the average person keeps their car nowadays, that's going to take a long time.

There are many rural, high-speed roundabouts that have achieved their goal of reducing serious-injury and fatal crash events. Most of them fall off your radar since they're single-lane roundabouts. But they also employ sound design practices: physical upstream guidance, approach signing, transitional lighting, and forgiving landscape design.
There is another option on the table, it is called "traffic light".
We are talking about a situation where vehicle has to slow down - and possibly come to a stop - to negotiate the intersection. For both roundabout and traffic light (and for a stop sign, for that matter) an advance warning has to be given - and received! - by a driver in order to achieve safe outcome. Failure to do so can - and in some designs will, cause a significant accident. That is pretty much all you need to know talking about fog or anything. Properly designed roundabout is probably worse than properly designed traffic light for this situation, as it falls under "will" part of it..
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 24, 2018, 12:08:09 AM
Connected vehicle technology is only viable once there is significant market saturation. And with the current price of vehicles and how long the average person keeps their car nowadays, that's going to take a long time.

V2V is included as a standard feature on 2017 Cadillac CTS’s sold in the U.S. and Canada.  It does take time for standard features in luxury models to trickle down to the compact car segment, but it will come.  I mean, is ABS only a standard option in Cadillac’s today?

What if there's a bus full of little kids coming from all directions and all electronic devices fail, and they're in dense fog?

In that case all the safety layers have broken down, and all that’s left to do is cross your fingers that the buses don’t end up in the intersection at the exact same time.  But if it’s so foggy that the driver can’t see the traffic signal, what makes you think they would be able to safely navigate through the sharp curves of a roundabout?  Below are two videos; one is a driver blowing through a red light and one blowing through a roundabout.  No harm, no foul with the red light runner!  Apparently that blue SUV had V2V in their vehicle, because they slammed on his brakes avoiding t-boning that vehicle.  Amazing...



There will be growing pains with connected vehicles, and there are a lot of issues to sort out still.  But in 10 years, you can't see a world where drivers approaching an intersection will be warned of red light runners?  That’s what GM has in mind when they included V2V technology in their 2017 CTS model.  Here is an excerpt from their press release:

Quote
Cadillac's V2V solution uses Dedicated Short-Range Communications (DSRC) and GPS and can handle 1,000 messages per second from vehicles up to nearly 1,000 feet away. For example, when a car approaches an urban intersection, the technology scans the vicinity for other vehicles and tracks their positions, directions and speeds, warning the driver of potential hazards that might otherwise be invisible.
http://media.cadillac.com/media/us/en/cadillac/news.detail.html/content/Pages/news/us/en/2017/mar/0309-v2v.html

If connected vehicles are successful and widespread adaptation takes place, there could be a day where it becomes very difficult to get t-boned by a red-light runner.  At that point, roundabouts may become more dangerous than signalized intersections.  Think about it,  mechanical failures will still happen and any bus that loses their brakes approaching a roundabout is going to FLY over the roundabout dukes of hazard style… much like the video above... HOLD ON KIDS!!!  In theory, with connected vehicles the only way two vehicles would get in a t-bone accident is if both vehicles lost their brakes, and end up entering the intersection at the exact same time.  The connected vehicles will know that there is about to be an imminent crash, but won’t be able to prevent it because the brakes are unable to be applied.  But then again, maybe the connected vehicles can determine that if one vehicle speeds up by 5 mph, it will be able to clear the intersection before the other “out of control”  vehicle enters the intersection.  It will give the warning “SPEED UP!”  in an attempt to prevent a deadly t-bone crash.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on April 24, 2018, 11:48:06 AM
Connected vehicle technology is only viable once there is significant market saturation. And with the current price of vehicles and how long the average person keeps their car nowadays, that's going to take a long time.

V2V is included as a standard feature on 2017 Cadillac CTS’s sold in the U.S. and Canada.  It does take time for standard features in luxury models to trickle down to the compact car segment, but it will come.  I mean, is ABS only a standard option in Cadillac’s today?

Again, you missed the point. Yes, the technology will eventually reach every car in every showroom. I recently sat in on a CV presentation, where it was said that VW promises to have the capability to send V2V data across its lineup within the next 2 model years. BUT IT STILL HAS TO REACH THE CONSUMER. Unless Oprah plans on several mass car giveaways, there will still be a large number of vehicles on the road still living in the technological dark ages. The average age of a car on the road is 11.5 years and trends shows signs of that growing older, especially as new car prices continue to increase and wages have not kept up (not to mention the elephant of health care costs). That also does not address the population of classic car collectors. The future of car tech looks very promising, but we still have to work with what is out there today and will be tomorrow. Further, as Uber has recently taught us, technology isn't infallible.

What if there's a bus full of little kids coming from all directions and all electronic devices fail, and they're in dense fog?

In that case all the safety layers have broken down, and all that’s left to do is cross your fingers that the buses don’t end up in the intersection at the exact same time.  But if it’s so foggy that the driver can’t see the traffic signal, what makes you think they would be able to safely navigate through the sharp curves of a roundabout?

Headlights, streetlights, and street signs still work in fog. Throw in a power outage for good measure, and you still have headlights and retroreflective signs and pavement markings. No different than a car negotiating tight mountain pass curves.

There is another option on the table, it is called "traffic light".

I never said it wasn't an option. It's just not an option that is designed to prevent high-speed t-bone crashes.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 24, 2018, 12:36:47 PM


There is another option on the table, it is called "traffic light".

I never said it wasn't an option. It's just not an option that is designed to prevent high-speed t-bone crashes.
Apparently, you're doing same thing Trade is criticizing in FHWA report throughout this thread (with little understanding from the rest of the gang)  : you assume roundabout forces drivers to slow down. Nope, in your "dense fog" scenario roundabout as prone to t-bone as traffic lights are. Driver has to get a "slow down" message in advance, something coming out of the fog will only make them die confused.. 
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on April 24, 2018, 12:47:49 PM
So a curve (https://goo.gl/maps/ezCm35BFVq22) can't force you to slow down. Gotcha. Shall I start finding mountain roads for you?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 24, 2018, 12:56:48 PM
So a curve (https://goo.gl/maps/ezCm35BFVq22) can't force you to slow down. Gotcha. Shall I start finding mountain roads for you?
A sharp curve in a fog - and remember, we're talking about
 
What if there's a bus full of little kids coming from all directions and all electronic devices fail, and they're in dense fog?
can easily be a cause for a crash if driver doesn't see it in advance.
Remember, you brought up dense fog as a situation we're talking about. And deliberately introduced extra curves - on roundabout approach and the circle itself - do increase probability of a serious accident.   And there was an example of such accident somewhere upstream in the thread..
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on April 24, 2018, 03:46:14 PM
can easily be a cause for a crash if driver doesn't see it in advance.

That can be said for most any collision, whether a roundabout is involved or not: debris in the road, lane closure due to construction, a bridge abutment, or a building at the end of a T-intersection. Most roundabouts, especially those on higher-speed facilities don't just pop up out of nowhere. And if the driver misses all the cues, whether is numerous signs or via GPS, the type of intersection isn't going to matter. At least the curbing of a roundabout provides a better chance of the crash only involving a single vehicle, at a lower speed, and at an indirect angle, versus full-speed at a blunt angle.

The mentioning of fog wasn't intended to be in support of a roundabout vs. a signalized intersection, rather it was to emphasize how silly Trade's slippery-slope/what-if arguments are. That said, the roundabout at least has the potential for redirecting the vehicles into deviating paths, rather than all to a single point.

Showing a vehicle "threading the needle" while running a red light is just proving one thing: luck. Showing a drunken driver vaulting over a roundabout is all about location...a more serious crash could have occurred had that same drunk driver plowed through a traffic signal or a DDI, or smack into a bridge pier.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 24, 2018, 04:35:54 PM
can easily be a cause for a crash if driver doesn't see it in advance.

That can be said for most any collision, whether a roundabout is involved or not: debris in the road, lane closure due to construction, a bridge abutment, or a building at the end of a T-intersection. Most roundabouts, especially those on higher-speed facilities don't just pop up out of nowhere. And if the driver misses all the cues, whether is numerous signs or via GPS, the type of intersection isn't going to matter. At least the curbing of a roundabout provides a better chance of the crash only involving a single vehicle, at a lower speed, and at an indirect angle, versus full-speed at a blunt angle.

The mentioning of fog wasn't intended to be in support of a roundabout vs. a signalized intersection, rather it was to emphasize how silly Trade's slippery-slope/what-if arguments are. That said, the roundabout at least has the potential for redirecting the vehicles into deviating paths, rather than all to a single point.

Showing a vehicle "threading the needle" while running a red light is just proving one thing: luck. Showing a drunken driver vaulting over a roundabout is all about location...a more serious crash could have occurred had that same drunk driver plowed through a traffic signal or a DDI, or smack into a bridge pier.
OK, we're closer in opinions  :bigass:
And "threading the needle" is about traffic volume after all. Randomly shooting through an intersection handling 50 thousand cars a day... I've seen bicyclist doing that - and that bastard lived to try that again! For 1000 cars a day - that is a much better chance than playing russian roulette.

One thing I would argue regarding roundabouts on a long stretch of a highway - driver can expect  minimal maneuvering knowing it is 100 rural miles along state rt. XXX - an expectation made unreasonable by roundabout  (but, to be fair, also by deer, broken car or farmer's tractor relocating to a different field)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 25, 2018, 10:53:36 AM
Showing a vehicle "threading the needle" while running a red light is just proving one thing: luck. Showing a drunken driver vaulting over a roundabout is all about location...a more serious crash could have occurred had that same drunk driver plowed through a traffic signal or a DDI, or smack into a bridge pier.

In the future, connected vehicles will make it increasingly difficult to get t-boned by red-light runners.  At that point, it has less to do about "luck", and more to do with technology.  I'm not saying connected vehicles will stop every potential crash, but if new car tech can drastically reduce t-bone crashes at intersections then what becomes the safety benefit of roundabouts?    It becomes a big dumb circle in the middle of the road that is potentially hazardous to anyone approaching it too fast (this is your captain speaking… prepare for takeoff).  Considering connected vehicles is already a standard option on some vehicles on the road today, it’s likely that widespread adaptation is coming.  Do you really think roundabouts are going to be hailed for their safety benefits in 20 years?
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on April 25, 2018, 01:46:54 PM
In the future, connected vehicles will make it increasingly difficult to get t-boned by red-light runners.  At that point, it has less to do about "luck", and more to do with technology.  I'm not saying connected vehicles will stop every potential crash, but if new car tech can drastically reduce t-bone crashes at intersections then what becomes the safety benefit of roundabouts?    It becomes a big dumb circle in the middle of the road that is potentially hazardous to anyone approaching it too fast (this is your captain speaking… prepare for takeoff).  Considering connected vehicles is already a standard option on some vehicles on the road today, it’s likely that widespread adaptation is coming.  Do you really think roundabouts are going to be hailed for their safety benefits in 20 years?

I can't believe that you think CV technology will only have an impact on signalized intersections. (Your bias is peaking out once again.) One would also expect CV technology to make roundabouts safer and more efficient as well (think microsimulation models). "You're approaching this roundabout too fast, you must reduce your speed." Further, if vehicles were computer controlled, headways at roundabout could be tightened as they could be at traffic signals, thereby increasing the capacities from current calculations. Likewise, at some point, technology should make safety a moot point for all intersection control types. Technology could also render all intersection controls as we know them today useless...stop signs, yield signs, traffic signals, etc... as everything will be in-car.

Not all roundabouts are constructed for safety reasons. They have been proven to have higher capacity than other intersection controls, to a point, then they begin to break down. As for 20 years from now? WHO THE HELL KNOWS??? Twenty years ago, roundabouts were barely present in the US. At one point, it was thought we'd have flying cars by now...maybe we'll have them then. This whole discussion could be moot 2 years from now.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on April 25, 2018, 02:31:50 PM
Showing a vehicle "threading the needle" while running a red light is just proving one thing: luck. Showing a drunken driver vaulting over a roundabout is all about location...a more serious crash could have occurred had that same drunk driver plowed through a traffic signal or a DDI, or smack into a bridge pier.

In the future, connected vehicles will make it increasingly difficult to get t-boned by red-light runners.  At that point, it has less to do about "luck", and more to do with technology.  I'm not saying connected vehicles will stop every potential crash, but if new car tech can drastically reduce t-bone crashes at intersections then what becomes the safety benefit of roundabouts?    It becomes a big dumb circle in the middle of the road that is potentially hazardous to anyone approaching it too fast (this is your captain speaking… prepare for takeoff).  Considering connected vehicles is already a standard option on some vehicles on the road today, it’s likely that widespread adaptation is coming.  Do you really think roundabouts are going to be hailed for their safety benefits in 20 years?

We won't need guardrails and signs and billions of dollars of other safety enhancements either.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 25, 2018, 02:59:06 PM
Technology could also render all intersection controls as we know them today useless...stop signs, yield signs, traffic signals, etc... as everything will be in-car.

As for 20 years from now? WHO THE HELL KNOWS??? Twenty years ago, roundabouts were barely present in the US. At one point, it was thought we'd have flying cars by now...maybe we'll have them then. This whole discussion could be moot 2 years from now.

When I initially brought up connected vehicles you suggested that implementation by the consumer would be slow, pointing out that the average age of a car on the road is 11.5 years.  Now, just a few posts later, you are talking about flying cars and connected vehicles eliminating the need for traffic signals and stop signs…. and citing that this whole discussion could be moot “2 years from now” .   What happens in 2 years exactly?
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on April 25, 2018, 03:37:20 PM
Technology could also render all intersection controls as we know them today useless...stop signs, yield signs, traffic signals, etc... as everything will be in-car.

As for 20 years from now? WHO THE HELL KNOWS??? Twenty years ago, roundabouts were barely present in the US. At one point, it was thought we'd have flying cars by now...maybe we'll have them then. This whole discussion could be moot 2 years from now.

When I initially brought up connected vehicles you suggested that implementation by the consumer would be slow, pointing out that the average age of a car on the road is 11.5 years.  Now, just a few posts later, you are talking about flying cars and connected vehicles eliminating the need for traffic signals and stop signs…. and citing that this whole discussion could be moot “2 years from now” .   What happens in 2 years exactly?

I was responding directly to your latest post/question, and that one only, and you know that. Apparently you are the only one who can live in Hypothetical What-If Land. Grow up and cut the BS. It's not cute or funny any more (not that it ever was to begin with).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 25, 2018, 04:50:16 PM
What if there's a bus full of little kids coming from all directions and all electronic devices fail, and they're in dense fog?

I legitimately responded to your hypothetical what-if land scenario.  Keeping it in context, I had just said that connected vehicles could dramatically reduce crashes at signalized intersections.  Seemingly you were suggesting that the buses full of little kids would get t-boned in the dense fog if the V2V fails (ie. all electronic devices fail).   I simply asked “if it’s so foggy that the driver can’t see the traffic signal, what makes you think they would be able to safely navigate through the sharp curves of a roundabout?”   In which you replied…

Headlights, streetlights, and street signs still work in fog. Throw in a power outage for good measure, and you still have headlights and retroreflective signs and pavement markings. No different than a car negotiating tight mountain pass curves.
   
Why would a driver approaching a traffic signal in dense fog have so much trouble seeing it, while a driver approaching a roundabout in dense fog could navigate through it just fine... like a car negotiating tight mountain pass curves as you put it?  You give this dense fog scenario, but the outcome changes whether the driver is approaching a traffic signal or a roundabout.  This is undeniable... if you take a roundabout too fast, it's a guaranteed crash.  When you blow through a red light you might get "lucky" as you put it and not get in a crash.... but in the future with connected vehicles, it won't be "luck" that the red-light runner didn't cause a crash.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on April 26, 2018, 01:44:21 AM
What if there's a bus full of little kids coming from all directions and all electronic devices fail, and they're in dense fog?

I legitimately responded to your hypothetical what-if land scenario.  Keeping it in context, I had just said that connected vehicles could dramatically reduce crashes at signalized intersections.  Seemingly you were suggesting that the buses full of little kids would get t-boned in the dense fog if the V2V fails (ie. all electronic devices fail).   I simply asked “if it’s so foggy that the driver can’t see the traffic signal, what makes you think they would be able to safely navigate through the sharp curves of a roundabout?”   In which you replied…

Headlights, streetlights, and street signs still work in fog. Throw in a power outage for good measure, and you still have headlights and retroreflective signs and pavement markings. No different than a car negotiating tight mountain pass curves.
   
Why would a driver approaching a traffic signal in dense fog have so much trouble seeing it, while a driver approaching a roundabout in dense fog could navigate through it just fine... like a car negotiating tight mountain pass curves as you put it?  You give this dense fog scenario, but the outcome changes whether the driver is approaching a traffic signal or a roundabout.

Similar the mountain pass, a properly designed, higher-speed roundabout will have several more cues as the driver approaches: at least one warning sign, diagrammed guide sign(s), and transitional lighting, all of which spaced far enough away for the driver to react. Better designs also employ curbing along the approach, well before any curves begin, including the splitter island. Just of a lighting standpoint, higher-speed traffic signals rarely have transitional lighting, relying instead on lights at the actual intersection - too late for a driver to react if still at full speed. At a traffic signal, you're lucky if there's a Signal Ahead warning sign. Even if one is posted, it's a guessing game for the driver as to how far downstream the signal actually is...even worse if the signals are not working.

When you blow through a red light you might get "lucky" as you put it and not get in a crash.... but in the future with connected vehicles, it won't be "luck" that the red-light runner didn't cause a crash.

And as I eluded to earlier, in the future technologically-rich environment we all are waiting for, the driver will also be warned on approach to roundabout, and whether their speed is prudent, and how much conflicting traffic may be approaching from the left.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 27, 2018, 10:18:07 AM
And as I eluded to earlier, in the future technologically-rich environment we all are waiting for, the driver will also be warned on approach to roundabout, and whether their speed is prudent, and how much conflicting traffic may be approaching from the left.

Really?  When the scenario was buses approaching a signalized intersection in dense-fog, you alluded to the V2V tech failing and NOT warning drivers of the approaching light.  Only when the drivers are approaching a roundabout do you suggest that the V2V technology would actually work.  Then you claim that my bias is peaking, when you are the one giving roundabouts every benefit of the doubt and assume the worst at signals.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on April 27, 2018, 11:08:05 AM
And as I eluded to earlier, in the future technologically-rich environment we all are waiting for, the driver will also be warned on approach to roundabout, and whether their speed is prudent, and how much conflicting traffic may be approaching from the left.

Really?  When the scenario was buses approaching a signalized intersection in dense-fog, you alluded to the V2V tech failing and NOT warning drivers of the approaching light.  Only when the drivers are approaching a roundabout do you suggest that the V2V technology would actually work.  Then you claim that my bias is peaking, when you are the one giving roundabouts every benefit of the doubt and assume the worst at signals.

No where, did I say that (referring to the part in bold). You provided several what-if scenarios, so I did one as well. No electronic device is immune to faults and failures from time to time, so that's what I based my scenario on. No where did I ever suggest V2V would not help traffic signal operations. You're the one who keeps implying that traffic signals are the only places that will benefit from V2V technology. I'm trying to keep an open and objective mind to all intersection control options. You, OTOH, try to find every minute opportunity to slam the door on roundabouts. I said it before, but your selective memory/reading makes it apparent that I need to say it again:
Roundabouts are not a silver-bullet traffic solution (nor a faultless solution), but they are a viable option in many circumstances.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 05, 2018, 01:44:26 AM
A new interchange along the 405 @ NE 85th St near Kirkland, WA is planned to be redeveloped from a cloverleaf into a multi-level roundabout interchange. The lower level multi-lane roundabout is to be for general purpose traffic, the middle level single-lane roundabout for buses and toll users, and the upper level for the 405 (no roundabout of course).

An additional roundabout is planned for Kirkland Way to the west.

https://seattletransitblog.com/2018/04/30/kirklands-ne-85th-brt-station/

(https://i2.wp.com/s3.amazonaws.com/stb-wp/wp-content/uploads/2018/04/21184209/Separated_Transit_Interchange_Concept_01.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 07, 2018, 01:23:08 PM
A new interchange along the 405 @ NE 85th St near Kirkland, WA is planned to be redeveloped from a cloverleaf into a multi-level roundabout interchange. The lower level multi-lane roundabout is to be for general purpose traffic, the middle level single-lane roundabout for buses and toll users, and the upper level for the 405 (no roundabout of course).

An additional roundabout is planned for Kirkland Way to the west.

https://seattletransitblog.com/2018/04/30/kirklands-ne-85th-brt-station/

(https://i2.wp.com/s3.amazonaws.com/stb-wp/wp-content/uploads/2018/04/21184209/Separated_Transit_Interchange_Concept_01.png)

Isn't this off-topic?  If it hasn't even been built yet, it's neither crash-prone nor...well, not crash-prone.

Well, I guess if tradephoric had posted the article, it would have been accompanied by something like, I wonder how many toddlers and puppy dogs will die a terrible and painful death.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 07, 2018, 01:56:12 PM
A new interchange along the 405 @ NE 85th St near Kirkland, WA is planned to be redeveloped from a cloverleaf into a multi-level roundabout interchange. The lower level multi-lane roundabout is to be for general purpose traffic, the middle level single-lane roundabout for buses and toll users, and the upper level for the 405 (no roundabout of course).

An additional roundabout is planned for Kirkland Way to the west.

https://seattletransitblog.com/2018/04/30/kirklands-ne-85th-brt-station/

(https://i2.wp.com/s3.amazonaws.com/stb-wp/wp-content/uploads/2018/04/21184209/Separated_Transit_Interchange_Concept_01.png)

Isn't this off-topic?  If it hasn't even been built yet, it's neither crash-prone nor...well, not crash-prone.

Well, I guess if tradephoric had posted the article, it would have been accompanied by something like, I wonder how many toddlers and puppy dogs will die a terrible and painful death.
It may be an interesting case to discuss. Roundabout highway interchange are topologically equal to good old diamond interchanges with some right-of-way tweaking added.
This is an entire new level of complexity with express/transit added into the sandwich. Cost of $300M is.... quite impressive, to say the least.
I don't know what are the traffic counts, bus passenger counts are relatively low according to the link.

So we may talk about:
-appropriate spending margins and who is getting kickbacks
-expected functionality of roundabouted diamond (and I suspect flyover ramps are not out of question given the cost)
-expected driver confusion level (looks like medium-raw cluster-k to me with those predominantly left exits, maybe I could get used to that after few weeks) and associated accident rate (whoa, finally back on topic!)
 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 07, 2018, 02:34:38 PM
Well, I guess if tradephoric had posted the article, it would have been accompanied by something like, I wonder how many toddlers and puppy dogs will die a terrible and painful death.

Don't forget the little piggies!  Remember that roundabout in Worthington, Minnesota?  Not only have there been multiple truck rollovers at the roundabout, other vehicles have flown straight over it Dukes of Hazzard style. 


These little piggies almost didn't make it to market when a Minn. hog truck rolled[/b][/size]
(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/102817.N.DG_.ROLLOVER%203.jpg?itok=DOQatmVs)
http://www.agweek.com/news/4350581-these-little-piggies-almost-didnt-make-it-market-when-minn-hog-truck-rolled
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 07, 2018, 02:45:11 PM
This is an entire new level of complexity with express/transit added into the sandwich. Cost of $300M is.... quite impressive, to say the least.
I don't know what are the traffic counts, bus passenger counts are relatively low according to the link.

That cost is quite impressive.  With the likely overruns, it will equate to about $1 for every American citizen to build this thing.  Of course that's not that bad considering the debt per American citizen in this country is $64,632 (and debt per taxpayer is $174,408).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 07, 2018, 02:50:03 PM
This is an entire new level of complexity with express/transit added into the sandwich. Cost of $300M is.... quite impressive, to say the least.
I don't know what are the traffic counts, bus passenger counts are relatively low according to the link.

That cost is quite impressive.  With the likely overruns, it will equate to about $1 for every American citizen to build this thing.  Of course that's not that bad considering the debt per American citizen in this country is $64,632 (and debt per taxpayer is $174,408).
We are talking about Seattle, a rich city with city budget of $10k per resident. I would still call it a bit pricey one, but they have Boeing and Amazon, they can afford spending few extra (billion) bucks..
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 07, 2018, 03:21:25 PM
Don't forget the little piggies!  Remember that roundabout in Worthington, Minnesota? 

Yep, I remember it.  The only roundabout where I've genuinely been worried the person next to me was going to bang into the side of my car.  Two consecutive roundabouts in Worthington, as a matter of fact.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on May 07, 2018, 03:31:22 PM
Don't forget the little piggies!  Remember that roundabout in Worthington, Minnesota? 
Yep, I remember it.  The only roundabout where I've genuinely been worried the person next to me was going to bang into the side of my car.  Two consecutive roundabouts in Worthington, as a matter of fact.

There's actually three roundabouts on MN-60 in Worthington, though I'm not sure you'd call them "consecutive," per se. And coincidentally, I drove through two of them on Saturday and didn't find anything out of the ordinary or "scary."
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 07, 2018, 03:40:40 PM
Don't forget the little piggies!  Remember that roundabout in Worthington, Minnesota? 
Yep, I remember it.  The only roundabout where I've genuinely been worried the person next to me was going to bang into the side of my car.  Two consecutive roundabouts in Worthington, as a matter of fact.

There's actually three roundabouts on MN-60 in Worthington, though I'm not sure you'd call them "consecutive," per se. And coincidentally, I drove through two of them on Saturday and didn't find anything out of the ordinary or "scary."

Well, the menace was no longer next to me by the time I got to the third roundabout that day.  See below for my original account.

Worthington Minnesota roundabout

It was only due to my attentiveness that I didn't get side-swiped at two of Worthington's roundabouts last month.  In fact, the experience made me think of this thread at the time.  But, since they are 2x1 rather than full 2x2, I didn't bring it up.

The main road (MN-60) is striped as two lanes in each direction through the roundabouts.  The driver next to me didn't seem to be the most capable, and seemed like the kind who drives as if she's the only one on the road.  So I decided to lag behind just a little bit as we drove through–which was fortunate, because she took both lanes and would have run into me if I hadn't lagged behind.  At the next roundabout, it was the same thing.  Good thing for me, she was getting off the highway at that second roundabout–turning left, I might add, from the right entry lane.  I can understand trucks and buses taking two lanes through a roundabout, but pure disregard for other drivers is just really irritating to me.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 07, 2018, 03:43:06 PM
By the way the pig slaughtering roundabouts aren't limited to America.  A lorry carrying 200 pigs overturned at a roundabout on the A68 near Darlington just hours ago. It injured the driver and killed several of the pigs.  Good thing the lorry didn't catch fire after it tipped over as it was reported the driver was trapped inside the vehicle.  That situation does sound "scary" to me.

Pigs killed after lorry carrying 200 animals overturns on roundabout
https://www.gazettelive.co.uk/news/teesside-news/pigs-killed-after-lorry-carrying-14626787

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 07, 2018, 04:28:21 PM
By the way the pig slaughtering roundabouts aren't limited to America.  A lorry carrying 200 pigs overturned at a roundabout on the A68 near Darlington just hours ago. It injured the driver and killed several of the pigs.  Good thing the lorry didn't catch fire after it tipped over as it was reported the driver was trapped inside the vehicle.  That situation does sound "scary" to me.

Pigs killed after lorry carrying 200 animals overturns on roundabout
https://www.gazettelive.co.uk/news/teesside-news/pigs-killed-after-lorry-carrying-14626787
We need a new sign to be added to MUTCD..
(https://orig00.deviantart.net/7714/f/2010/343/8/6/beat_up_pig_by_decor8rgirl-d34k4f9.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 09, 2018, 10:08:48 PM
I originally posted the story on the 405/Kirkland roundabouts because I thought it would piss tradephoric off. An interchange that could easily be reconfigured into a Parclo B4, instead becoming a three level roundabout?! Oh the horror. Also, it's another new dual lane roundabout, which this thread has become a dumping ground for.



This is an entire new level of complexity with express/transit added into the sandwich. Cost of $300M is.... quite impressive, to say the least.
I don't know what are the traffic counts, bus passenger counts are relatively low according to the link.

That cost is quite impressive.  With the likely overruns, it will equate to about $1 for every American citizen to build this thing.  Of course that's not that bad considering the debt per American citizen in this country is $64,632 (and debt per taxpayer is $174,408).

We are talking about Seattle, a rich city with city budget of $10k per resident. I would still call it a bit pricey one, but they have Boeing and Amazon, they can afford spending few extra (billion) bucks..

To be fair, the citizens in the Sound Transit taxing district are paying for the interchange, not just the local cities. The interchange is funded as part of ST3, a $50B+ taxing package to expand transit across the Seattle region. The BRT line along the 405 is part of that package.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 11, 2018, 01:08:57 PM
Also, it's another new dual lane roundabout, which this thread has become a dumping ground for.

My one takeaway from this whole thread is that there are problems inherent in full dual-lane roundabouts:  specifically that there are non-glancing conflict points.  And that statistics for both single-lane roundabouts (with no such non-glancing conflict points) and dual-lane roundabouts should not be combined, lest the results be misleading.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 11, 2018, 02:39:06 PM
Also, it's another new dual lane roundabout, which this thread has become a dumping ground for.

My one takeaway from this whole thread is that there are problems inherent in full dual-lane roundabouts:  specifically that there are non-glancing conflict points.  And that statistics for both single-lane roundabouts (with no such non-glancing conflict points) and dual-lane roundabouts should not be combined, lest the results be misleading.
If you will, I have a slightly wider version of this. What is the role of roundabouts in a grand scheme of things in terms of throughput? Where would you put roundabout in a list of intersection designs with increasing throughput - that is: 4-way stop, traffic light, grade separated?
I would say that roundabouts belong to busy 4-way stop/not-so-busy traffic light interval. We had some european guidelines here showing a 30K/daily limit for complex roundabout, which seems reasonable to slightly optimistic; and I know a (very busy) traffic light controlled intersection with 50k+ daily traffic.
Now you can increase traffic light throughput quite a bit by adding components, such as dedicated turn lanes or slip ramps - of course at a cost of footprint. And those upgrades can be fairly seamless, you don't have to bulldoze entire thing for an extra lane (although imminent domain of land is a pain..)
You can also upgrade stop signals to a traffic light.
Roundabout, however, is a solution with limited throughput which can NOT be easily upgraded to next tier - which is complex traffic light.
And that can easily become a problem: no upgrade short of increasing complexity beyond the reason OR total rebuild.... Or continue funneling traffic through intersection above design limit - and pretend problem doesn't exist.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 11, 2018, 03:16:11 PM
Also, it's another new dual lane roundabout, which this thread has become a dumping ground for.

My one takeaway from this whole thread is that there are problems inherent in full dual-lane roundabouts:  specifically that there are non-glancing conflict points.  And that statistics for both single-lane roundabouts (with no such non-glancing conflict points) and dual-lane roundabouts should not be combined, lest the results be misleading.
If you will, I have a slightly wider version of this. What is the role of roundabouts in a grand scheme of things in terms of throughput? Where would you put roundabout in a list of intersection designs with increasing throughput - that is: 4-way stop, traffic light, grade separated?
I would say that roundabouts belong to busy 4-way stop/not-so-busy traffic light interval. We had some european guidelines here showing a 30K/daily limit for complex roundabout, which seems reasonable to slightly optimistic; and I know a (very busy) traffic light controlled intersection with 50k+ daily traffic.
Now you can increase traffic light throughput quite a bit by adding components, such as dedicated turn lanes or slip ramps - of course at a cost of footprint. And those upgrades can be fairly seamless, you don't have to bulldoze entire thing for an extra lane (although imminent domain of land is a pain..)
You can also upgrade stop signals to a traffic light.
Roundabout, however, is a solution with limited throughput which can NOT be easily upgraded to next tier - which is complex traffic light.
And that can easily become a problem: no upgrade short of increasing complexity beyond the reason OR total rebuild.... Or continue funneling traffic through intersection above design limit - and pretend problem doesn't exist.

This is a good point.  And I agree with your placement of roundabouts on the throughput continuum.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 11, 2018, 03:37:04 PM
I visually attempted to make kalvado’s excellent point in another post.   CJW2001 kept banging on about how much roundabouts have improved traffic flow in Carmel, ignoring the fact that traffic flow could have been improved by simply adding turn lanes to the signalized intersections that the roundabouts replaced.  And kalvado is right in pointing out that roundabouts have a limited throughput…. there reaches a point where roundabouts just don’t work well.  So is it any surprise that traffic flow improved in Carmel after these intersections pictured below were upgraded?  An intersection is upgraded that probably hasn't been touched since the 60s... and we are surprised that traffic flow improves?  Let's just give all the credit to the roundabouts :crazy:

To be honest, I’m sure there was an improvement in traffic flow in Carmel after the roundabouts were built.   But could that be because the intersections the roundabouts replaced were woefully inadequate to carry the capacity of a ballooning Carmel population?  Here are some before/after pictures of roundabout location in Carmel.  Not surprising traffic flow improved when you compare these pictures… not to mention the fact the two major surface streets in Carmel were converted to grade-separated freeways over the past decade.

(https://i.imgur.com/14wCyqy.jpg)

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 11, 2018, 03:54:28 PM
But the most drastic improvement in traffic flow of any roundabout project I've seen was at Maple & Drake in West Bloomfield, Michigan.  Here are the before/after pictures.  The signalized intersection the roundabout replaced didn't even have dedicated right turn lanes.  Is it any wonder that traffic cleared up after this massive 3x2 roundabout was completed? 

(https://i.imgur.com/KRTavlx.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 11, 2018, 04:03:21 PM
I get it that adding a right-turn lane to a stoplight approach can reduce the number of cars that have to stop at the light:  at least some right-turning traffic will be taken out of the queue.  But I imagine less of an improvement due to the addition of more left-turn storage.  Sure, dual turn lanes require a shorter arrow phase, but how much time savings are we really talking about there?  All that is to say, traffic might not have "cleared up" to the same extent with the mere addition of lanes as it did with the removal of red lights altogether.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 11, 2018, 04:19:38 PM
I get it that adding a right-turn lane to a stoplight approach can reduce the number of cars that have to stop at the light:  at least some right-turning traffic will be taken out of the queue.  But I imagine less of an improvement due to the addition of more left-turn storage.  Sure, dual turn lanes require a shorter arrow phase, but how much time savings are we really talking about there?  All that is to say, traffic might not have "cleared up" to the same extent with the mere addition of lanes as it did with the removal of red lights altogether.
Depends on traffic pattern and design. If left turn and straight through are squeezed into a single lane (very common on low-traffic roads), and there is enough of oncoming traffic - a single turning car can block a lot of flow. Or you need a very restrictive phasing of traffic light. Or extra footprint for a long left turn lane.
Widening roads to add extra lane - not just to intersection, but entire road - apparently adds throughput. And looks like that is the case for most pictures trade shows.
Eliminating red lights may help if there is significant dead time in a cycle, that is no sensors and a very short timing cycle ANd interestingly enough, longer cycle of light increases average wait time - but also increases peak throughput.
Actually one can take beloved "fewer conflict points in roundabout" picture and explain how roundabout peak throughput is lower if traffic doesn't come from one side of intersection, and why traffic light is better and safer..
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 11, 2018, 04:36:48 PM
All that is to say, traffic might not have "cleared up" to the same extent with the mere addition of lanes as it did with the removal of red lights altogether.

I’ll concede that point.  The congestion really has disappeared ever since the Maple & Drake roundabout was built (and it was built over a decade ago now).  By the way the 3x2 roundabout pictured above has since been converted to a 2x2 roundabout.  The roundabout had a crash rate of 4.43 MEV when it was a triple-lane roundabout, but my guess is it has dropped since the conversion to a 2x2. 

As much as I have focused on 2x2 roundabouts having high crash rates, I think they can work OK when there is a limited capacity upstream/downstream of the roundabout (ie. a two-lane road).  The limited roadway capacity can help create natural gaps in traffic, reducing the likelihood of drivers entering the roundabout side-by-side.  Drivers would theoretically only enter the roundabout side-by-side if a driver had to yield for a vehicle already inside the roundabout.  But if the upstream geometry is such that you are driving along a 4-lane boulevard approaching a roundabout, drivers can very easily enter a roundabout side-by-side (increasing the likelihood of sideswipe crashes and/or crashes when people don’t follow the guide arrows).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 24, 2018, 01:49:44 PM
They are planning to build a complex elevated roundabout in Lincoln.  Below the elevated roundabout there will be a standard signalized intersection with direct left turn movements (you know, the dangerous turning movements that roundabouts are designed to prevent in the first place).  Now Lincoln drivers will get to enjoy the crash prone multi-lane elevated roundabout with less frequent deadly crashes below it.   Great design!   Lincoln just doesn’t have a good track record when it comes to roundabouts.  The triple-lane 14th Street and Superior lane roundabout was a mess from day one.  The only way to reduce the number of crashes was by downsizing it and reducing the number of circulating lanes.  Just recently the city built a retaining wall/sculpture in the middle of the 14th/Superior roundabout so any out of control driver will potentially crash dead on into a retaining wall.   Sounds safe…. of course what’s going to happen when a driver blows through an elevated roundabout?

Elevated roundabout design for 14th, Old Cheney gets final public scrutiny
http://journalstar.com/news/local/govt-and-politics/elevated-roundabout-design-for-th-old-cheney-gets-final-public/article_1de51613-002b-51e7-ba08-d85ebaffc3eb.html

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 24, 2018, 01:57:43 PM
Quote
The intersection, which has garnered quite a reputation for being Australia's most hated over the years, is a particularly gnarly mix of heavy traffic, confusion and chaos.

The multi-lane nightmare even scored the dubious title of the state's most complained about roundabout in 2015, according to Transport for NSW records.

And just a few hundred metres away from the roundabout is a spot that's been named the worst merging location for accidents in NSW - the intersection of Homebush Bay Drive and the M4 Motorway. That's according to data from NSW insurance claims in 2016.

Is this Australia’s worst roundabout?
https://www.centraltelegraph.com.au/news/is-this-australias-worst-roundabout/3423161/
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 24, 2018, 02:00:56 PM
They are planning to build a complex elevated roundabout in Lincoln.  Below the elevated roundabout there will be a standard signalized intersection with direct left turn movements (you know, the dangerous turning movements that roundabouts are designed to prevent in the first place).  Now Lincoln drivers will get to enjoy the crash prone multi-lane elevated roundabout with less frequent deadly crashes below it.   Great design!   Lincoln just doesn’t have a good track record when it comes to roundabouts.  The triple-lane 14th Street and Superior lane roundabout was a mess from day one.  The only way to reduce the number of crashes was by downsizing it and reducing the number of circulating lanes.  Just recently the city built a retaining wall/sculpture in the middle of the 14th/Superior roundabout so any out of control driver will potentially crash dead on into a retaining wall.   Sounds safe…. of course what’s going to happen when a driver blows through an elevated roundabout?

Elevated roundabout design for 14th, Old Cheney gets final public scrutiny
http://journalstar.com/news/local/govt-and-politics/elevated-roundabout-design-for-th-old-cheney-gets-final-public/article_1de51613-002b-51e7-ba08-d85ebaffc3eb.html
Would be interesting to see what kind of traffic distribution prompted such layout. Must be something quite funny and pretty heavy...
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 24, 2018, 04:24:24 PM
Lincoln drivers will get to enjoy the crash prone multi-lane elevated roundabout[citation needed]

Because I'm sick of this thread being a dumping ground for every roundabout project you think might become crash-prone.  If all you want to do is be cynical and snarky about whatever roundabout project comes across your radar that you don't like, then just change the thread title to "tradephoric dumps on roundabouts" or something along those lines.

You spent the first who knows how many pages of this thread tenaciously convincing us that there is actually a subset of roundabouts that are inherently more crash-prone than others and discussing possible reasons for that.  You've hung onto this thread for around two years, slowly but surely gaining the respect and changing the minds of many of us–even if only to a small degree.  But now you've devolved into blasting roundabout projects as "crash-prone" before they've even been constructed.  And because of that, frankly, you're losing my respect in the process.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 25, 2018, 10:25:16 AM
But now you've devolved into blasting roundabout projects as "crash-prone" before they've even been constructed.  And because of that, frankly, you're losing my respect in the process.

Making predictions about crash prone multi-lane roundabouts is almost as easy as predicting that the sun will rise in the east tomorrow.  I’ve stated this before, but there hasn’t been a documented 2x2 multi-lane roundabout with a crash rate below 2.0 MEV.  Many agencies are required to undergo safety audits when a signalized intersection has a crash rate over 2.0 MEV.  Constructing a 2x2 modern roundabout will almost ensure that the crash rate will exceed this “critical”  crash rate.  I have made predictions about the number of roundabout crashes in the past, and you can even bash me for betting the over on my prediction and I won’t take offense.

Prediction:
Here’s a traffic simulation of a roundabout currently under construction in Farmington Hills, Michigan at 14 Mile & Orchard Lake.  Over the last 5 years, the intersection has averaged 46 crashes per year.  This roundabout could experience a significant number of crashes once completed.  Does anybody want to wager how many crashes this roundabout will experience in FY2016?  The over/under is 180 crashes (I’ll bet the over). 


Reality:
Quote
14-Orchard roundabout is tops for accidents, but is it really dangerous?
http://www.freep.com/story/news/local/michigan/oakland/2017/04/04/orchard-roundabout-tops-accidents-really-dangerous/100046220/

Turns out there were 163 crashes at the Orchard Lake/M-5 roundabout in 2016.  That’s a 232% increase in total crashes compared to the pre-roundabout condition when it averaged 49 crashes per year (look at the chart below for pre-roundabout crash data).  Worse yet, there were 27 injury crashes at the roundabout compared to an average of 9.5 injury crashes/year before the roundabout - a 184% increase in injury crashes.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/untitled232_zps21amc2ug.png)
http://semcog.org/Data-and-Maps/High-Frequency-Crash-Locations/Point_Id/63052513/view/RoadIntersectionCrashDetail
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 25, 2018, 11:22:34 AM
Carmel’s Police Department recently released it’s 2017 annual report.  In previous reports the Police Department would always show a map of the top 20 accident locations in Carmel during the year and would list the total number of crashes that occurred.  That all changed in 2014, when the top accident location map was suddenly omitted from their annual report.  There was a sudden lack of transparency, and now there is no easy way for the public to see what locations in Carmel are experiencing the most crashes (put another way the mayor doesn't want any bad PR for his precious roundabouts).

Carmel’s non-transparent 2017 annual report:
http://www.carmel.in.gov/home/showdocument?id=10651
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 25, 2018, 01:04:53 PM
there hasn’t been a documented 2x2 multi-lane roundabout with a crash rate below 2.0 MEV. 

In all countries of the world?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 25, 2018, 03:11:17 PM
there hasn’t been a documented 2x2 multi-lane roundabout with a crash rate below 2.0 MEV. 

In all countries of the world?

I can't speak for some of the European countries, but I believe some of the worst intersections (in terms of pure collisions) in Australia are also roundabouts. There was a news article posted somewhere back on this thread about a very bad intersection in Australia that was basically like a double roundabout. To my knowledge, roundabouts have been built in Australia for a long time, and many people in Australia are also British, so, really, everyone should be used to them by now. Oddly enough, Australia's roundabouts are also very reminiscent of American roundabouts. To my knowledge, American roundabouts were originally based on British designs, just reflected, but then switched to the Australian style, which is how they are still designed today. The big giveaway is the chicanes that are used approaching roundabouts, which is a chiefly Australian design (at least originally), as well as the large truck apron. Many European countries do not use truck aprons, or at least large ones like those in the US, or at least large ones like those in the US.

tl;dr -- I'm not 100% sure, but there are definitely other crash-prone roundabouts outside of the US.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on May 25, 2018, 03:25:44 PM
there hasn’t been a documented 2x2 multi-lane roundabout with a crash rate below 2.0 MEV. 

In all countries of the world?

The key is "documented".

He's prone to find information regarding roundabouts where a serious or fatal crash has occurred. He recently brought up a news story about a crash at a roundabout in The Villages, FL.  The Villages have at least 31 roundabouts, most 2x2, on their two main roads (Morse Blvd & Buena Vista Blvd). He's yet to reveal a story involving any of the other 30.  I would be absolutely shocked that every single one of them had MEVs above 2. 
Title: Re: Crash prone 'modern roundabouts'
Post by: johndoe on May 28, 2018, 08:24:21 PM
As I saw some "failure to yield" mistakes today I thought about this thread... I know I've seen studies where different pavement markings, signs, and fewer lanes are used to encourage proper yielding (and as I recall most don't have optimistic conclusions).  I'm assuming there is a correlation between higher speeds and yielding violations (just a guess...has a study looked at this?)

I was wondering about two other options: speed tables and stop signs.  Speed tables have been discussed as a way to control speeds at entry/ped crossings, are DOTs starting to build these now?  Regarding stop signs, I remember someone earlier in the thread talking about replacing yield signs with stop signs.  Although it would drastically lower the capacity, does anyone know if DOTs have done this on particularly problematic approaches?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 28, 2018, 08:50:07 PM
As I saw some "failure to yield" mistakes today I thought about this thread... I know I've seen studies where different pavement markings, signs, and fewer lanes are used to encourage proper yielding (and as I recall most don't have optimistic conclusions).  I'm assuming there is a correlation between higher speeds and yielding violations (just a guess...has a study looked at this?)

I was wondering about two other options: speed tables and stop signs.  Speed tables have been discussed as a way to control speeds at entry/ped crossings, are DOTs starting to build these now?  Regarding stop signs, I remember someone earlier in the thread talking about replacing yield signs with stop signs.  Although it would drastically lower the capacity, does anyone know if DOTs have done this on particularly problematic approaches?
This all would ultimately defeat the purpose of roundabout as a higher throughput traffic control device. Is there a reason even to consider stop signs at the entering lanes when that degrades entire system to a glorified 4-way stop?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 29, 2018, 03:26:56 AM
As I saw some "failure to yield" mistakes today I thought about this thread... I know I've seen studies where different pavement markings, signs, and fewer lanes are used to encourage proper yielding (and as I recall most don't have optimistic conclusions).  I'm assuming there is a correlation between higher speeds and yielding violations (just a guess...has a study looked at this?)

I was wondering about two other options: speed tables and stop signs.  Speed tables have been discussed as a way to control speeds at entry/ped crossings, are DOTs starting to build these now?  Regarding stop signs, I remember someone earlier in the thread talking about replacing yield signs with stop signs.  Although it would drastically lower the capacity, does anyone know if DOTs have done this on particularly problematic approaches?

This all would ultimately defeat the purpose of roundabout as a higher throughput traffic control device. Is there a reason even to consider stop signs at the entering lanes when that degrades entire system to a glorified 4-way stop?

I would be extremely hesitant to install stop signs, but its capacity could still be higher than a 4-way stop because multiple vehicles could occupy the circle at once.

Still, it should be a last resort. I would love to see speed tables used. They are used frequently in the Netherlands, and I don't see why they wouldn't work here, especially at intersections where vehicles must yield to pedestrians, such as at roundabouts or slip lanes. The latter situation is a frequent use-case in Boulder, CO: https://goo.gl/Q9SV8V & https://goo.gl/B9ybvs.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 29, 2018, 08:23:32 AM

I would be extremely hesitant to install stop signs, but its capacity could still be higher than a 4-way stop because multiple vehicles could occupy the circle at once.

Still, it should be a last resort. I would love to see speed tables used. They are used frequently in the Netherlands, and I don't see why they wouldn't work here, especially at intersections where vehicles must yield to pedestrians, such as at roundabouts or slip lanes. The latter situation is a frequent use-case in Boulder, CO: https://goo.gl/Q9SV8V & https://goo.gl/B9ybvs.
Multiple vehicles occupying circle for capacity boost is a... khm ....  interesting argument.
Pretty much as saying that you can enjoy your beverage faster if you use a longer straw which would holds more liquid. In both situations, however, it is the bottleneck - in case of roundabout being the entry rate - which defines total throughput.
Slowing down to 20 mph means average car takes about 0.5 second to travel its length, and that directly cuts into 2 second interval. So same story - decreasing throughput and killing suspension.
You see, this is why  traffic lights are so great - they move 2D space conflict into a time domain separation. Resolving the conflict in third dimension is still more efficient, but much more expensive.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on May 29, 2018, 08:29:36 AM
I'll take the roundabouts on NY 85 south of Albany over the former traffic lights any day.  I'd imagine a poll would result in most citizens if Bethlehem, NY saying they are more efficient that the lights that preceded them.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 29, 2018, 08:58:17 AM
I'll take the roundabouts on NY 85 south of Albany over the former traffic lights any day.  I'd imagine a poll would result in most citizens if Bethlehem, NY saying they are more efficient that the lights that preceded them.
Yep, those roundabouts actually helped. Probably building up from 2-lane undivided to 4-lane divided also added some minor improvements in traffic, though. Bypassing a chunk of New Scotland road could also contribute a bit.
But the last one out is a father, you know...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 29, 2018, 11:15:53 AM
A Canadian report discussing some potential solutions to driver errors at multi-lane roundabouts…

SOLUTIONS TO DRIVER ERRORS AT MULTI-LANE ROUNDABOUTS
http://www.tac-atc.ca/sites/default/files/conf_papers/weber_p_-_solutions_to_driver_errors_at_multi-lane_roundabouts.pdf

The case study that interested me was the St. Joseph Boulevard and Jeanne D’Arc Boulevard roundabout in Ottawa.  The design is similar to the crash-prone 2x2 State and Ellsworth roundabout in Ann Arbor, Michigan (the very first roundabout discussed in this thread).  Each roundabout has roughly the same traffic volumes, roughly the same ICD, both are about 2000 feet from a freeway, both have commercial developments along all 4-corners, the link speeds approaching each roundabout are roughly the same… yet the Ann Arbor roundabout has historically double the number of crashes as the Ottawa roundabout.  Maybe the reporting requirements between American and Canadian agencies are different, and that can explain the discrepancy between the crashes, but I thought the comparison was interesting nonetheless.

(https://i.imgur.com/BY2tiB7.jpg)


(https://i.imgur.com/f8LG6Gv.png)

Agencies seem too quick to attribute reductions in accidents to whatever new “fix”  they are testing out at the roundabout.  Time-and-time again there is an initial spike in crashes at these new roundabouts only for the numbers to level off over the next few years.  Apart from whatever “fix”  they are pushing now, I’m more interested in why the initial crash numbers at the Ottawa roundabout were so much lower than the initial crash numbers at the Ann Arbor roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on May 29, 2018, 12:29:03 PM
I’m more interested in why the initial crash numbers at the Ottawa roundabout were so much lower than the initial crash numbers at the Ann Arbor roundabout.

Much better markings.
Also, the one approach to the Ann Arbor one (bottom left in the image) comes in at an angle, meaning traffic entering from that approach has a harder turn into the roundabout and probably sub-optimal visibility.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 29, 2018, 01:25:27 PM
Much better markings.
Also, the one approach to the Ann Arbor one (bottom left in the image) comes in at an angle, meaning traffic entering from that approach has a harder turn into the roundabout and probably sub-optimal visibility.

Another noticeable difference is the plantings (or lack thereof) in the central islands.  The Ann Arbor roundabout just has a patch of grass in the central island while the Ottawa roundabout has tall plantings and 3 pine trees. Shrubs in the central island are cool...  they help the driver realize that they better start turning soon because it's no longer a paved road infront of them.  I just don't like plantings in the central island that will kill you if you strike them at high speeds.

(https://i.imgur.com/8gYJVTv.jpg)

If you notice there is also a lot more side-friction at the Ottawa roundabout.  There are several poles with flags on them along the splitter island and the sidewalks are right up against the travel lane.  OTOH, in the Ann Arbor roundabout the splitter islands are pretty bare and the sidewalks are set back several feet from the travel lane.  You could make the argument that drivers would be more likely to drive cautiously through the Ottawa roundabout since there is so much more side-friction.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 29, 2018, 01:34:59 PM
Much better markings.
Also, the one approach to the Ann Arbor one (bottom left in the image) comes in at an angle, meaning traffic entering from that approach has a harder turn into the roundabout and probably sub-optimal visibility.

Another noticeable difference is the plantings (or lack thereof) in the central islands.  The Ann Arbor roundabout just has a patch of grass in the central island while the Ottawa roundabout has tall plantings and 3 pine trees. Shrubs in the central island are cool...  they help the driver realize that they better start turning soon because it's no longer a paved road infront of them.  I just don't like plantings in the central island that will kill you if you strike them at high speeds.

If you notice there is also a lot more side-friction at the Ottawa roundabout.  There are several poles with flags on them along the splitter island and the sidewalks are right up against the travel lane.  OTOH, in the Ann Arbor roundabout the splitter islands are pretty bare and the sidewalks are set back several feet from the travel lane.  You could make the argument that drivers would be more likely to drive cautiously through the Ottawa roundabout since there is so much more side-friction.

another big factor in roundabout performance is number of cars doing left turns. Hard to say without knowing local traffic patterns
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 29, 2018, 02:12:19 PM
another big factor in roundabout performance is number of cars doing left turns. Hard to say without knowing local traffic patterns

Yeah, it reaches the point where it becomes a big guessing game.  Based on the crash statistics of that Ottawa roundabout, people may convince themselves that a central island needs to have a big mound of dirt and shrubs to obstruct drivers view from seeing across the roundabout.  But then you look at the most crash prone roundabout in Michigan in 2017, and it was a roundabout with a big mound of dirt and shrubs to obstruct the drivers view from seeing across the roundabout.  The 18 1/2 Mile and Van Dyke Ave roundabout had 165 crashes in 2017 and was constructed way back in 2005.  Here's the central island view of the Van Dyke roundabout...

(https://i.imgur.com/i9CnNUs.jpg)



Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 29, 2018, 06:41:53 PM

I would be extremely hesitant to install stop signs, but its capacity could still be higher than a 4-way stop because multiple vehicles could occupy the circle at once.

Still, it should be a last resort. I would love to see speed tables used. They are used frequently in the Netherlands, and I don't see why they wouldn't work here, especially at intersections where vehicles must yield to pedestrians, such as at roundabouts or slip lanes. The latter situation is a frequent use-case in Boulder, CO: https://goo.gl/Q9SV8V & https://goo.gl/B9ybvs.
Multiple vehicles occupying circle for capacity boost is a... khm ....  interesting argument.
Pretty much as saying that you can enjoy your beverage faster if you use a longer straw which would holds more liquid. In both situations, however, it is the bottleneck - in case of roundabout being the entry rate - which defines total throughput.
Slowing down to 20 mph means average car takes about 0.5 second to travel its length, and that directly cuts into 2 second interval. So same story - decreasing throughput and killing suspension.
You see, this is why  traffic lights are so great - they move 2D space conflict into a time domain separation. Resolving the conflict in third dimension is still more efficient, but much more expensive.

I'm not trying to compare a roundabout with stop signs to a signal. A roundabout with stop signs will have similar throughput to a 4-way stop. I would much prefer a signal than a roundabout with stop signs.

The "more can occupy the intersection at once" argument is based on drivers who approach on opposite angles being able to enter at the same time, regardless of which direction they are going. This is possible at a four-way stop, as long as no one is turning left.
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on May 29, 2018, 07:57:17 PM
The "more can occupy the intersection at once" argument is based on drivers who approach on opposite angles being able to enter at the same time, regardless of which direction they are going. This is possible at a four-way stop, as long as no one is turning left.

"No one turning left" seems like a pretty big caveat. Not only that, though: traffic at a four-way stop can't proceed straight at the same time as perpendicular traffic. The only possible way four cars can all go through a four way stop at once is if they're all turning right, which renders your last point moot.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 30, 2018, 01:10:58 AM
The "more can occupy the intersection at once" argument is based on drivers who approach on opposite angles being able to enter at the same time, regardless of which direction they are going. This is possible at a four-way stop, as long as no one is turning left.

"No one turning left" seems like a pretty big caveat. Not only that, though: traffic at a four-way stop can't proceed straight at the same time as perpendicular traffic. The only possible way four cars can all go through a four way stop at once is if they're all turning right, which renders your last point moot.

Allow me to clarify. If two cars arrive at a four way stop at the same time, their paths will not conflict unless one of them turns left (going straight or right obviously doesn't involve crossing paths). So, four way stops can be efficient if each car that arrives can immediately proceed without having to wait for someone else. The problem is when two cars arrive at the same time, and one of them has to turn left (not both). The car going straight (or the car waiting to turn) must wait for the other to proceed before going. At a four way stop roundabout (lol), four cars can all arrive at the same time and (in theory) perform simultaneous maneuvers (in any direction), because the area between each entry and exit leg is long enough for a vehicle. A standard roundabout with four legs is therefore capable of handling at least four cars at a time. This is difficult to describe without a diagram.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 30, 2018, 06:43:09 AM
The "more can occupy the intersection at once" argument is based on drivers who approach on opposite angles being able to enter at the same time, regardless of which direction they are going. This is possible at a four-way stop, as long as no one is turning left.

"No one turning left" seems like a pretty big caveat. Not only that, though: traffic at a four-way stop can't proceed straight at the same time as perpendicular traffic. The only possible way four cars can all go through a four way stop at once is if they're all turning right, which renders your last point moot.

Allow me to clarify. If two cars arrive at a four way stop at the same time, their paths will not conflict unless one of them turns left (going straight or right obviously doesn't involve crossing paths). So, four way stops can be efficient if each car that arrives can immediately proceed without having to wait for someone else. The problem is when two cars arrive at the same time, and one of them has to turn left (not both). The car going straight (or the car waiting to turn) must wait for the other to proceed before going. At a four way stop roundabout (lol), four cars can all arrive at the same time and (in theory) perform simultaneous maneuvers (in any direction), because the area between each entry and exit leg is long enough for a vehicle. A standard roundabout with four legs is therefore capable of handling at least four cars at a time. This is difficult to describe without a diagram.

Nice try, but nope, cars do NOT arrive simultaneously, there is an asynchronous flow.
A better way to look at it is for how long entering car blocks other entrances. For roundabout, it is probably 2 seconds for any entrance it passes plus 1 second for first downstream entrance. For a  4-way stop things are a bit more confusing since all other legs are affected to some extent - but effect may not be 100%. E.g car going east-west fully blocks north approach for maybe 3 seconds (wait + accelerate and pass), blocks 1 out of 3 moves(left turn) for west approach and 2 out of 3 (straight+left turn) for southern approach.
But in general, if move is affected for roundabout, it will be affected in a 4-way stop as well - EXCEPT for two oncoming lefts, which can proceed simultaneously on 4-way stop, but interfere TWICE in roundabout.
Advantage of roundabout is that duration of each conflict is less, so throughput for location with few left turns can benefit compared to a 4-way stop.
That was all for a single lane circle, 2 lanes are a bit more tricky.
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on May 30, 2018, 12:28:06 PM
Allow me to clarify.
Likewise.

If two cars arrive at a four way stop at the same time, their paths will not conflict unless one of them turns left (going straight or right obviously doesn't involve crossing paths).

My whole point is that going straight does involve crossing paths; if someone else approaches on the opposite road (perpendicular to you, as I said), then your paths most definitely cross. You'd T-bone each other if you both attempted to go through the four-way stop at once.
This actually adds to your argument that roundabouts have higher capacity, because at a roundabout, both cars can theoretically go at once, due to the increased distance (around the circle) and no requirement to stop.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 30, 2018, 12:55:04 PM
Allow me to clarify.
Likewise.

If two cars arrive at a four way stop at the same time, their paths will not conflict unless one of them turns left (going straight or right obviously doesn't involve crossing paths).

My whole point is that going straight does involve crossing paths; if someone else approaches on the opposite road (perpendicular to you, as I said), then your paths most definitely cross. You'd T-bone each other if you both attempted to go through the four-way stop at once.
This actually adds to your argument that roundabouts have higher capacity, because at a roundabout, both cars can theoretically go at once, due to the increased distance (around the circle) and no requirement to stop.
If paths would cross in the intersection, paths would also cross in roundabout (reverse is not true, by the way). It may be a conflict between cars arriving at slightly different points in time, but it is conflict nonetheless.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 30, 2018, 02:47:05 PM
If two cars arrive at a four way stop at the same time, their paths will not conflict unless one of them turns left (going straight or right obviously doesn't involve crossing paths).

My whole point is that going straight does involve crossing paths; if someone else approaches on the opposite road (perpendicular to you, as I said), then your paths most definitely cross. You'd T-bone each other if you both attempted to go through the four-way stop at once.

I should have been more specific. I was only talking about two cars approaching from opposite angles, not right angles. I see now that I failed to mention that in either of my posts. My bad.

This actually adds to your argument that roundabouts have higher capacity, because at a roundabout, both cars can theoretically go at once, due to the increased distance (around the circle) and no requirement to stop.

Yes, exactly. I've illustrated as much below.

Advantage of roundabout is that duration of each conflict is less, so throughput for location with few left turns can benefit compared to a 4-way stop.
That was all for a single lane circle, 2 lanes are a bit more tricky.

This is all that I'm trying to say. I'm not trying to suggest that there's zero conflict points. Roundabouts just have less period of conflict because the intersection is just bigger.

To better illustrate what I'm trying to say about the simultaneous left turns, here's a diagram using an old roundabout that I designed. All of these cars can turn left at the same time, as long as they all enter at the same time, because there is significant distance between each entry point. In practice, this wouldn't work quite as well, because four cars all arriving at once is pretty unusual, and that kind of throws things off. But the point is still there:

(https://i.imgur.com/ceWzUbA.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 30, 2018, 03:26:33 PM
Jake, i was about to post this picture last night because i thought it was exactly what you were describing.  It looks oddly familiar to your picture lol.  I don't think the red car entered the roundabout from the northern leg... but 3 out of 4 legs with vehicles entering the roundabout simultaneously ain't bad

(https://i.imgur.com/P4I3NaZ.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 30, 2018, 03:40:02 PM
Jake, i was about to post this picture last night because i thought it was exactly what you were describing.  It looks oddly familiar to your picture lol.  I don't think the red car entered the roundabout from the northern leg... but 3 out of 4 legs with vehicles entering the roundabout simultaneously ain't bad

https://i.imgur.com/P4I3NaZ.jpg

:-D No kidding! Very similar. My diagram comes from a redesign of this intersection (https://goo.gl/EvPF2Y), which I had originally designed (https://i.imgur.com/yUml2wb.png) as a signal.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 30, 2018, 04:36:08 PM

This is all that I'm trying to say. I'm not trying to suggest that there's zero conflict points. Roundabouts just have less period of conflict because the intersection is just bigger.

To better illustrate what I'm trying to say about the simultaneous left turns, here's a diagram using an old roundabout that I designed. All of these cars can turn left at the same time, as long as they all enter at the same time, because there is significant distance between each entry point. In practice, this wouldn't work quite as well, because four cars all arriving at once is pretty unusual, and that kind of throws things off. But the point is still there:
/me starts thinking this guy is not joking....
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 30, 2018, 04:54:52 PM

This is all that I'm trying to say. I'm not trying to suggest that there's zero conflict points. Roundabouts just have less period of conflict because the intersection is just bigger.

To better illustrate what I'm trying to say about the simultaneous left turns, here's a diagram using an old roundabout that I designed. All of these cars can turn left at the same time, as long as they all enter at the same time, because there is significant distance between each entry point. In practice, this wouldn't work quite as well, because four cars all arriving at once is pretty unusual, and that kind of throws things off. But the point is still there:

/me starts thinking this guy is not joking....

I am describing a theory, not something that necessarily happens in practice. You don't seem to be understanding that. Obviously what happens in practice is more important, but that doesn't negate the point behind my theory. Which is, four cars can enter a roundabout simultaneously and leave without conflicting, no matter which direction they are going. Even if that's difficult in practice.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 30, 2018, 05:02:56 PM

This is all that I'm trying to say. I'm not trying to suggest that there's zero conflict points. Roundabouts just have less period of conflict because the intersection is just bigger.

To better illustrate what I'm trying to say about the simultaneous left turns, here's a diagram using an old roundabout that I designed. All of these cars can turn left at the same time, as long as they all enter at the same time, because there is significant distance between each entry point. In practice, this wouldn't work quite as well, because four cars all arriving at once is pretty unusual, and that kind of throws things off. But the point is still there:

/me starts thinking this guy is not joking....

I am describing a theory, not something that necessarily happens in practice. You don't seem to be understanding that. Obviously what happens in practice is more important, but that doesn't negate the point behind my theory. Which is that, for cars can enter a roundabout simultaneously and leave without conflicting. Even if that's difficult in practice.
You are not describing theory. You are considering a very special relative timing which turns out to be beneficial in one case and not in the other. There are other special timings, which will play it out opposite.

As a result, you are narrowing down your scope to some very narrow detail instead of looking at a bigger picture. Which includes, at the very least, considering all sorts of relative timings.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 30, 2018, 06:18:37 PM

This is all that I'm trying to say. I'm not trying to suggest that there's zero conflict points. Roundabouts just have less period of conflict because the intersection is just bigger.

To better illustrate what I'm trying to say about the simultaneous left turns, here's a diagram using an old roundabout that I designed. All of these cars can turn left at the same time, as long as they all enter at the same time, because there is significant distance between each entry point. In practice, this wouldn't work quite as well, because four cars all arriving at once is pretty unusual, and that kind of throws things off. But the point is still there:

/me starts thinking this guy is not joking....

I am describing a theory, not something that necessarily happens in practice. You don't seem to be understanding that. Obviously what happens in practice is more important, but that doesn't negate the point behind my theory. Which is that, for cars can enter a roundabout simultaneously and leave without conflicting. Even if that's difficult in practice.
You are not describing theory. You are considering a very special relative timing which turns out to be beneficial in one case and not in the other. There are other special timings, which will play it out opposite.

As a result, you are narrowing down your scope to some very narrow detail instead of looking at a bigger picture. Which includes, at the very least, considering all sorts of relative timings.

The theory goes, "if four cars arrive at once, they can all proceed at once assuming no other traffic is in the circle". I don't care how rare it is. That wasn't my point. I guess it was more of an observation. Of course, if it's a line of cars all intending to turn left, then disaster. :-D --> I think this is what you've been alluding to?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 30, 2018, 07:06:11 PM

The theory goes, "if four cars arrive at once, they can all proceed at once assuming no other traffic is in the circle". I don't care how rare it is. That wasn't my point. I guess it was more of an observation. Of course, if it's a line of cars all intending to turn left, then disaster. :-D --> I think this is what you've been alluding to?
No, I am just trying to press you into describing a bigger picture. Something I often try to do while dealing with students - it just sometimes show up when I am  off campus... :ded:
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 30, 2018, 08:08:00 PM

The theory goes, "if four cars arrive at once, they can all proceed at once assuming no other traffic is in the circle". I don't care how rare it is. That wasn't my point. I guess it was more of an observation. Of course, if it's a line of cars all intending to turn left, then disaster. :-D --> I think this is what you've been alluding to?

No, I am just trying to press you into describing a bigger picture. Something I often try to do while dealing with students - it just sometimes show up when I am  off campus... :ded:

It's not that I didn't see the bigger picture. It's just that my example didn't pertain to a bigger picture. My example was somewhat narrow: four cars arriving at an intersection to turn left at the same time could all proceed at the same time at a roundabout (this is only true for left-turning traffic at a traditional intersection if two cars arrive at the same time to turn left). No other intersection design permits this behavior. The problem, of course, is that there are more than four cars on the road. I think this is where we get into your point about the bigger picture.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 01, 2018, 09:31:13 AM
New data released and the most crash prone roundabout in Michigan last year was at Van Dyke Avenue (M-53) and 18 1/2 Mile Road in Sterling Heights.  There was an incredible 80% spike in crashes from the previous year (going from 92 crashes in 2016 to 165 in 2017).  The three-lane roundabout was constructed in 2005 and i can't explain the massive increase in year-over-year crashes.  Injury crashes also tripled, from 4 in 2016 to 13 in 2017.

There were 3 other roundabouts that had over 100 crashes in 2017 (State & Ellsworth = 110; Martin Pkwy & Pontiac Trail = 142; and Orchard Lake & 14 Mile = 144).  The roundabout with the most injury crashes was at Orchard Lake & 14 mile with 24 injury crashes.  These crash-prone roundabouts aren't getting any better evidenced by the fact that a 13 year old roundabout had 165 crashes last year.
 
Where were the most Michigan roundabout accidents in 2017?
https://www.michiganautolaw.com/blog/2018/05/24/most-michigan-roundabout-accidents-in-2017/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 01, 2018, 11:19:16 AM
Here's an aerial of the Van Dyke and 18 1/2 Mile with a proposed redesign. 

(https://i.imgur.com/WZGr4OQ.jpg)

Having a straight shot exiting the roundabout could simplify the roundabout operation IMO.  Drivers circulating the roundabout who drive over a "straight only" arrow pavement marking would actually continue to drive "straight" as oppose to weave through the roundabout.  The green path in the picture is simply easier to drive than the blue path.   Notice that the blue path hugs the inside of the roundabout for much longer than the green path, so a driver who wishes to enter the roundabout doesn't know the circulating drivers intention till much later on.  With the blue path it's a guessing game if the vehicle is about to exit the roundabout or continue circulating through it.  Makes it much more likely a driver pulls out infront of someone because they "guessed" wrong.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 01, 2018, 02:41:50 PM
I've read that straight exit paths aren't good for pedestrian crossings (higher exit speed). But I would think visibility would be better not having a curve. I like what I see. Are they considering any actual revisions?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 01, 2018, 02:51:34 PM
I've read that straight exit paths aren't good for pedestrian crossings (higher exit speed). But I would think visibility would be better not having a curve. I like what I see. Are they considering any actual revisions?

I haven't heard of any official plans to upgrade the roundabout.  I'm just playing around with some ideas i have.  Hey Jake, what program did you use to create the rendering of the roundabout in reply #1782?  I wanted to mess around with the Van Dyke roundabout some more but don't have a good program to use.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 03, 2018, 11:05:52 PM
(https://i.imgur.com/OsKh4no.jpg)

Here's a redesign for the Van Dyke roundabout.  Three main changes...

1.  Straight out exits. 
2.  Arrows in circulating lanes moved farther up to the entry legs.
3.  Central island reconfigured to be more rectangular than circular. 



Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 04, 2018, 12:55:08 AM
I've read that straight exit paths aren't good for pedestrian crossings (higher exit speed). But I would think visibility would be better not having a curve. I like what I see. Are they considering any actual revisions?

I haven't heard of any official plans to upgrade the roundabout.  I'm just playing around with some ideas i have.  Hey Jake, what program did you use to create the rendering of the roundabout in reply #1782?  I wanted to mess around with the Van Dyke roundabout some more but don't have a good program to use.

Sorry for the delay in response. My above diagram was created with Adobe Illustrator, which I've been using off-and-on for about ten years. It's one of my favorite computer programs. Most of what I design in that program is built to the scale of a background image.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 04, 2018, 09:21:31 AM
I've read that straight exit paths aren't good for pedestrian crossings (higher exit speed). But I would think visibility would be better not having a curve. I like what I see. Are they considering any actual revisions?

I haven't heard of any official plans to upgrade the roundabout.  I'm just playing around with some ideas i have.  Hey Jake, what program did you use to create the rendering of the roundabout in reply #1782?  I wanted to mess around with the Van Dyke roundabout some more but don't have a good program to use.

Sorry for the delay in response. My above diagram was created with Adobe Illustrator, which I've been using off-and-on for about ten years. It's one of my favorite computer programs. Most of what I design in that program is built to the scale of a background image.

No problem Jake.  I used (fumbled) with Photoshop to make the overlay design above but I'm just not very good with that program.  I'll take a look at Adobe Illustrator.   
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on June 04, 2018, 04:24:07 PM
No problem Jake.  I used (fumbled) with Photoshop to make the overlay design above but I'm just not very good with that program.  I'll take a look at Adobe Illustrator.   

Or if you're unwilling to pay Adobe the unreasonable prices they charge to use their software, Inkscape is the free and open-source alternative to Adobe Illustrator. It's what I use, and is more than good enough to create sign graphics (or things like roundabout layouts), even if it lacks a lot of the fancier features Illustrator has.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 04, 2018, 04:43:35 PM
No problem Jake.  I used (fumbled) with Photoshop to make the overlay design above but I'm just not very good with that program.  I'll take a look at Adobe Illustrator.   

Or if you're unwilling to pay Adobe the unreasonable prices they charge to use their software, Inkscape is the free and open-source alternative to Adobe Illustrator. It's what I use, and is more than good enough to create sign graphics (or things like roundabout layouts), even if it lacks a lot of the fancier features Illustrator has.

Adobe's CC programs are expensive if you're a non-vocational user, but they're dirt cheap for those who use them professionally. That doesn't necessarily describe me, but $50/month for Adobe's entire suite is a bargain if you want my opinion.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on June 04, 2018, 06:24:13 PM
No problem Jake.  I used (fumbled) with Photoshop to make the overlay design above but I'm just not very good with that program.  I'll take a look at Adobe Illustrator.   
Or if you're unwilling to pay Adobe the unreasonable prices they charge to use their software, Inkscape is the free and open-source alternative to Adobe Illustrator. It's what I use, and is more than good enough to create sign graphics (or things like roundabout layouts), even if it lacks a lot of the fancier features Illustrator has.
Adobe's CC programs are expensive if you're a non-vocational user, but they're dirt cheap for those who use them professionally. That doesn't necessarily describe me, but $50/month for Adobe's entire suite is a bargain if you want my opinion.

Or $0 forever for CS6 if you're willing to put in a bit of effort to visit sites of slight ill-repute. ;-)

(Not that I've done that, no… Totally not.)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 04, 2018, 09:33:20 PM
No problem Jake.  I used (fumbled) with Photoshop to make the overlay design above but I'm just not very good with that program.  I'll take a look at Adobe Illustrator.   
Or if you're unwilling to pay Adobe the unreasonable prices they charge to use their software, Inkscape is the free and open-source alternative to Adobe Illustrator. It's what I use, and is more than good enough to create sign graphics (or things like roundabout layouts), even if it lacks a lot of the fancier features Illustrator has.
Adobe's CC programs are expensive if you're a non-vocational user, but they're dirt cheap for those who use them professionally. That doesn't necessarily describe me, but $50/month for Adobe's entire suite is a bargain if you want my opinion.
Or $0 forever for CS6 if you're willing to put in a bit of effort to visit sites of slight ill-repute. ;-)

(Not that I've done that, no… Totally not.)

Oh I did when I was younger! But the subscription model is much easier to manage (financially), and I always have the latest updates so I'm happy to being doing it legally now.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 13, 2018, 03:30:32 PM
Another fatal Summerlin roundabout crash just happened.  This comes 7 months after a fatal crash at the Village Center Dr and Meadow Hills Drive roundabout in Summerlin back in November.  The very first modern roundabouts built in America haven't done a very good job at preventing fatalities lately.

Motorcyclist killed in crash at roundabout in west Las Vegas
https://www.reviewjournal.com/local/summerlin/motorcyclist-killed-in-crash-at-roundabout-in-west-las-vegas/
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 13, 2018, 03:55:29 PM
Hmm. He hit the curb going right? I'm guessing that means he misjudged the curb between the right turn slip lane and the circulating lanes? Hard to say, but I know those slip lanes haven't always been there.
Title: Re: Crash prone 'modern roundabouts'
Post by: roadfro on June 16, 2018, 05:12:42 PM
Another fatal Summerlin roundabout crash just happened.  This comes 7 months after a fatal crash at the Village Center Dr and Meadow Hills Drive roundabout in Summerlin back in November.  The very first modern roundabouts built in America haven't done a very good job at preventing fatalities lately.

Motorcyclist killed in crash at roundabout in west Las Vegas
https://www.reviewjournal.com/local/summerlin/motorcyclist-killed-in-crash-at-roundabout-in-west-las-vegas/
Hmm. He hit the curb going right? I'm guessing that means he misjudged the curb between the right turn slip lane and the circulating lanes? Hard to say, but I know those slip lanes haven't always been there.

The "first modern roundabouts" built in America are the two north of Summerlin Pkwy, on Village Center Circle at Town Center Dr and at Hills Center Dr/Meadow Hills Dr, both constructed circa 1990.

This particular crash happened at Town Center Dr & Hualapai Way, constructed circa 1995 and modified to include the right turn slip lane islands between 2000 and 2004 (according to Historic Aerials imagery).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 25, 2018, 07:51:11 AM
They just can't seem to fix the notorious Britannia roundabout in Adelaide.  Even after a major $3.2 million reconfiguration of the roundabout in 2013 that converted it from a single roundabout to a double roundabout, casualty crashes are the exact same as before the reconfiguration (at the time experts said the reconfiguration would 'reduce casualty crashes by up to 23 per cent').   The troubled intersection is going to be discussed at an upcoming Adelaide's City Counsel Meeting and the new option on the table is grade-separation. 

Traffic experts float new Britannia roundabout overhaul

https://indaily.com.au/news/2018/06/25/traffic-experts-float-new-britannia-roundabout-overhaul/
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on June 25, 2018, 08:03:49 AM
I mean this in the sincerest way possible, but: do you search for news about roundabouts every morning, or something? I'm curious how it is you find all these news articles all the time.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 25, 2018, 08:39:04 AM
I mean this in the sincerest way possible, but: do you search for news about roundabouts every morning, or something? I'm curious how it is you find all these news articles all the time.

The very first reply on this thread was made after I linked a news article about an Ann Arbor roundabout that experienced 170 crashes in 2013, which was the most crash prone intersection in Michigan.

Speaks more to the (in)flexibility of Michigan drivers than it does any inherent safety risk with roundabouts.  New roundabouts elsewhere have seen major drops in the number of crashes.

I wanted to see if froggie was right.  While some roundabouts have certainly seen major drops in the number of crashes, froggie failed to mention all the examples of roundabouts that have seen major increases in the number of crashes.  I think this thread has done a good job highlighting which types of roundabouts are likely to see big increases in crashes, but that does take a lot of research.  It’s not enough just to show that there have been big increases in crashes at 2x2 and 2x3 roundabouts in Michigan, but when you can show that this is a pattern nationwide I think it’s more effective.  To answer your question no I don’t search for news stories about roundabouts every morning, but it’s not that hard to keep track of the known problem roundabouts if you really want to.  I’d argue that many supposed roundabout experts have an affinity for roundabouts, and don’t want to highlight the problematic ones as this could erode public support for their beloved roundabouts!  I don't care about that.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on June 25, 2018, 09:29:24 AM
...To answer your question no I don’t search for news stories about roundabouts every morning, but it’s not that hard to keep track of the known problem roundabouts if you really want to...

Being that you have a tendency to write posts about roundabouts that have no known history of problems and happen to have a single fatal accident, and your posts are filled with links to newspaper and TV news websites, your answer seems to be a non-answer.  Or are you saying you look for stories in the afternoon or evening, so "I don't search every morning" is technically correct?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 25, 2018, 09:57:29 AM
Being that you have a tendency to write posts about roundabouts that have no known history of problems and happen to have a single fatal accident...

A single fatal crash is a significant event.  According to published data, signalized intersections in America average a fatal crash about every 100 years and drivers have only been driving through modern roundabouts in this country for 27 years.    Considering there have been 2 fatal crashes at Summerlin Nevada roundabouts over the past several months - the first community in America to build modern roundabouts — they instantly become fatality prone intersections.  Supposedly roundabouts reduce fatal crashes by 90% when compared to signalized intersections.  If that's the case, I'd expect a fatal crash at a roundabout once every 862 years or something insane like that.. not 2 fatal Summerlin roundabout crashes (the birthplace of the modern roundabout) in just 27 years. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 25, 2018, 01:30:14 PM
Supposedly roundabouts reduce fatal crashes by 90% when compared to signalized intersections.  If that's the case, I'd expect a fatal crash at a roundabout once every 862 years or something insane like that

Yes, if that 90% was compared to any old signal. But to the best of my knowledge, that data was based on roundabouts which replaced crash-prone signals. I don't think there's any expectation that all roundabouts reduce fatal crashes by 90%, since not every intersection experiences that many fatalities.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 25, 2018, 01:40:01 PM
Supposedly roundabouts reduce fatal crashes by 90% when compared to signalized intersections.  If that's the case, I'd expect a fatal crash at a roundabout once every 862 years or something insane like that

Yes, if that 90% was compared to any old signal. But to the best of my knowledge, that data was based on roundabouts which replaced crash-prone signals. I don't think there's any expectation that all roundabouts reduce fatal crashes by 90%, since not every intersection experiences that many fatalities.
Another common narration for roundabouts is that due to lower traffic speeds and more favorable collision angles (no high speed t-bones), fatal accident rate drops way way down, as well as serious injury ones - even if property-only go up. 90% seems very conservative number with such a narration... 
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on June 25, 2018, 01:55:02 PM
I mean this in the sincerest way possible, but: do you search for news about roundabouts every morning, or something? I'm curious how it is you find all these news articles all the time.

Being that you have a tendency to write posts about roundabouts that have no known history of problems and happen to have a single fatal accident...

A single fatal crash is a significant event.  According to published data, signalized intersections in America average a fatal crash about every 100 years and drivers have only been driving through modern roundabouts in this country for 27 years.    Considering there have been 2 fatal crashes at Summerlin Nevada roundabouts over the past several months - the first community in America to build modern roundabouts — they instantly become fatality prone intersections.  Supposedly roundabouts reduce fatal crashes by 90% when compared to signalized intersections.  If that's the case, I'd expect a fatal crash at a roundabout once every 862 years or something insane like that.. not 2 fatal Summerlin roundabout crashes (the birthplace of the modern roundabout) in just 27 years. 

Followup question: Are you a politician?  Because you never actually answer the questions posted.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 09, 2018, 03:24:26 PM
I love it.  La Crosse's first roundabout replaced a signalized intersection that didn't have any crashes the year before the roundabout was built.  It's really hard to improve on ZERO crashes.  What would a 35% reduction of zero crashes be?  The real question is why did the city pick an already safe intersection to construct a roundabout?  Admittedly the previous intersection was an odd staggered four-way intersection, so that probably had something to do with it, but it doesn't appear to have been picked based on its safety record.  Days before the official opening of the roundabout in 2017, a motorcylist nearly killed himself after plowing through the roundabout at high speed.  But... but... but... we were told roundabouts reduce total crashes by 35%!  Tell that to the people of Ann Arbor, where a double-lane roundabout there saw a 10 fold increase in crashes.  But how gullible do you have to be to believe that ZERO crashes will be reduced by 35%.  Silly headline indeed!  According to the article there were 7 crashes last year at the roundabout (defies expectations.. shocking that there would be more than ZERO crashes!). 

First year roundabout accident totals on Cass Street defy expectations
http://www.1410wizm.com/index.php/home-m/item/34063-first-year-roundabout-accident-totals-on-cass-street-defy-expectations
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 09, 2018, 03:35:46 PM
Here's hoping those seven collisions are just a first year thing.

I just drove through a brand new (two week old-ish) roundabout near Anacortes, WA yesterday, and there were plenty of horns. No accidents, though. I don't know if there were any accidents before the roundabout, but I drove through this roundabout (the Sharpes Corner Roundabout) and it's brother to the south (the Howards Corner Roundabout) seven times in a very short amount of time. So I give it a thumbs up. The old signalized intersection was just overloaded. No traffic issues when I approached any of the seven times.

The only issue I see is the path overlap along the southern edge of the roundabout (left entry in the photo below). Drivers were negotiating it fine, since both lanes had drivers entering simultaneously, preventing drivers from just ignoring the lane lines. But some drivers do let their guard down, and might just go from the right lane to the inner circulating lane if they're not paying attention.

https://twitter.com/wsdot_north/status/1012706908422062088

Video from WSDOT:

https://twitter.com/wsdot_north/status/1011630333807112192

Note the link in the tweet; there are live cameras of both roundabouts online: http://www.wsdot.com/traffic/cameras/OakHarbor.aspx?cam=9498
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 09, 2018, 03:55:31 PM


I just drove through a brand new (two week old-ish) roundabout near Anacortes, WA yesterday, and there were plenty of horns. No accidents, though. I don't know if there were any accidents before the roundabout, but I drove through this roundabout (the Sharpes Corner Roundabout) and it's brother to the south (the Howards Corner Roundabout) seven times in a very short amount of time. So I give it a thumbs up. The old signalized intersection was just overloaded. No traffic issues when I approached any of the seven times.

The only issue I see is the path overlap along the southern edge of the roundabout (left entry in the photo below). Drivers were negotiating it fine, since both lanes had drivers entering simultaneously, preventing drivers from just ignoring the lane lines. But some drivers do let their guard down, and might just go from the right lane to the inner circulating lane if they're not paying attention.

Looking at old Google maps images, conversion of southbound exit from the intersection to 2 lanes is the trick. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 09, 2018, 04:10:12 PM
Here's hoping those seven collisions are just a first year thing.

I just drove through a brand new (two week old-ish) roundabout near Anacortes, WA yesterday, and there were plenty of horns. No accidents, though. I don't know if there were any accidents before the roundabout, but I drove through this roundabout (the Sharpes Corner Roundabout) and it's brother to the south (the Howards Corner Roundabout) seven times in a very short amount of time. So I give it a thumbs up. The old signalized intersection was just overloaded. No traffic issues when I approached any of the seven times.

The only issue I see is the path overlap along the southern edge of the roundabout (left entry in the photo below). Drivers were negotiating it fine, since both lanes had drivers entering simultaneously, preventing drivers from just ignoring the lane lines. But some drivers do let their guard down, and might just go from the right lane to the inner circulating lane if they're not paying attention.

Looking at the aerial of the old intersection it does appear vehicles traveling WB turning left onto SR20 were nearly backing up onto the through lanes of traffic.  The increased capacity of the roundabout with the double left turns now should clear out those left turners, which is a great thing.

My concern is traffic traveling the other direction.  Here is a streetview of the road about 1,000 feet from the roundabout.  Traffic approaching the roundabout is traveling downhill through a curve in what resembles a limited access highway.  Now the same arguments can be made when the intersection was a traffic signal, but in the scenario where an out of control truck loses his brakes, the trucker approaching a traffic signal at least has the chance of blowing through a green light (and if he does blow through a red light, an observant left-turner who has a green may yield to the multi-ton truck, because they don’t want to die).  Now as the out of control truck with no brakes approaches the sharp curves of a roundabout… well good luck slowing down to 25 mph so you don’t tip your load over.  This roundabout just seems tailor made to be a truck rollover hotspot (and I do see a fair share of 18-wheelers in the google earth aerial).   Will I be at all surprised if I hear about a truck rolling over at this roundabout within 6 months?  Not at all.

(https://i.imgur.com/GtNpUu5.jpg)

EDIT: I may be exaggerating how big a downhill grade it is approaching the roundabout.  It looks like it's going downhill, but i'm sure you have a better idea about that.  Even still, a truck just traveling along what appears to be a limited access highway isn't necessarily going to be expecting to see a roundabout pop up in the middle of the road.  Hopefully there are a LOT of advanced warning signs for this roundabout in particular. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 09, 2018, 05:27:47 PM
Here's hoping those seven collisions are just a first year thing.

I just drove through a brand new (two week old-ish) roundabout near Anacortes, WA yesterday, and there were plenty of horns. No accidents, though. I don't know if there were any accidents before the roundabout, but I drove through this roundabout (the Sharpes Corner Roundabout) and it's brother to the south (the Howards Corner Roundabout) seven times in a very short amount of time. So I give it a thumbs up. The old signalized intersection was just overloaded. No traffic issues when I approached any of the seven times.

The only issue I see is the path overlap along the southern edge of the roundabout (left entry in the photo below). Drivers were negotiating it fine, since both lanes had drivers entering simultaneously, preventing drivers from just ignoring the lane lines. But some drivers do let their guard down, and might just go from the right lane to the inner circulating lane if they're not paying attention.

Looking at the aerial of the old intersection it does appear vehicles traveling WB turning left onto SR20 were nearly backing up onto the through lanes of traffic.  The increased capacity of the roundabout with the double left turns now should clear out those left turners, which is a great thing.

My concern is traffic traveling the other direction.  Here is a streetview of the road about 1,000 feet from the roundabout.  Traffic approaching the roundabout is traveling downhill through a curve in what resembles a limited access highway.  Now the same arguments can be made when the intersection was a traffic signal, but in the scenario where an out of control truck loses his brakes, the trucker approaching a traffic signal at least has the chance of blowing through a green light (and if he does blow through a red light, an observant left-turner who has a green may yield to the multi-ton truck, because they don’t want to die).  Now as the out of control truck with no brakes approaches the sharp curves of a roundabout… well good luck slowing down to 25 mph so you don’t tip your load over.  This roundabout just seems tailor made to be a truck rollover hotspot (and I do see a fair share of 18-wheelers in the google earth aerial).   Will I be at all surprised if I hear about a truck rolling over at this roundabout within 6 months?  Not at all.

https://i.imgur.com/GtNpUu5.jpg

EDIT: I may be exaggerating how big a downhill grade it is approaching the roundabout.  It looks like it's going downhill, but i'm sure you have a better idea about that.  Even still, a truck just traveling along what appears to be a limited access highway isn't necessarily going to be expecting to see a roundabout pop up in the middle of the road.  Hopefully there are a LOT of advanced warning signs for this roundabout in particular. 

In my limited experience, a truck without any brakes going down that hill (not a steep hill, but a long hill nevertheless) would have crashed long before reaching the roundabout, either into the accompanying forest or a barrier. There's too many curves for something that heavy to not have already tipped over. The roundabout is basically in the middle of a curve. If it did make it to the roundabout, certainly that would be quite a show, but I doubt it would. A good trucker would try and bail before that, I hope.

Regardless, a truck without any brakes could slam into anything in its path, be it other cars or barriers. Sure, they could make it through that green light, assuming other waiting cars in either lane could somehow react to a truck approaching them at 80+, but that's not like a final checkpoint. There's a constant merge on the right they'd have to deal with, plus a pretty strong curve after the signal. Then another curve not long after that, with a signal, and then another two signals with curves beyond that. If they somehow made it through all that without crashing or stopping, there's a very steep bridge over the Swinomish that would have stopped them.

With that said, might there be a tip over at this new roundabout? It's possible, but only because a driver missed the signs, not because it's out of control.

FWIW, a truck would tip over in a roundabout for the same reason that one might tip over on a freeway clover: inattentive driving. But sometimes, it's just the best option for traffic flow. This area is rural with mostly random arrivals. It's brilliant.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 09, 2018, 06:04:03 PM
Truck without brakes is an elephant in the room, and it is pretty much a given that someone will have a bad day over that...

Brilliant.. Would just expanding left turn from east to south to 2 lanes be an adequate solution? Or circular motion (reduced wait time at low traffic, reduced maximum throughput compared to light controlled motion) is a crucial part of improvement?   

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 09, 2018, 06:22:18 PM
Brilliant.. Would just expanding left turn from east to south to 2 lanes be an adequate solution? Or circular motion (reduced wait time at low traffic, reduced maximum throughput compared to light controlled motion) is a crucial part of improvement?

The key modification was making SR 20 between Sharpes Corner and Howards Corner right-in right-out only, which required implementing some sort of U-turn situation at both intersections. Roundabouts were the obvious solution.

FWIW, here's an image uploaded to WSDOT Flickr ten years ago (two years after intersection improvements were considered here) that shows the types of collisions that occurred at the signal:

(https://c2.staticflickr.com/4/3245/2890432178_2eef70e996_b.jpg)

The original design actually included a southern underpass for eastbound traffic, but this was scrapped at some point:

(https://c2.staticflickr.com/4/3103/2868373895_2c642b6852_b.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 10, 2018, 07:34:33 AM


The key modification was making SR 20 between Sharpes Corner and Howards Corner right-in right-out only, which required implementing some sort of U-turn situation at both intersections. Roundabouts were the obvious solution.
That explains a few things, although dumping turning traffic into a historically problematic intersection is an interesting solution.
I wonder if there was a significant development to the south of that area and corresponding traffic increase?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 10, 2018, 02:11:59 PM
The key modification was making SR 20 between Sharpes Corner and Howards Corner right-in right-out only, which required implementing some sort of U-turn situation at both intersections. Roundabouts were the obvious solution.
That explains a few things, although dumping turning traffic into a historically problematic intersection is an interesting solution.

Well, you could say the same thing about freeways. They localize most of the conflict points at interchanges. If you reduce the number of cars going through a specific intersection, you might reduce the chance of collisions at said intersection. But the benefits of doing so may be outweighed by the negatives of allowing added freedom of movement in other areas.

WSDOT typically studies these things to death, so I'm sure they considered the increased traffic at the roundabouts from all the U-turning traffic. If anything, it just stops traffic from entering from one of the sides that might flood the roundabout, allowing traffic to enter freely on the other side for a few moments. This is not really a major issue, but the U-turning traffic does provide a small benefit in this way.

I wonder if there was a significant development to the south of that area and corresponding traffic increase?

SR-20 to the south is the only road access to Whidbey Island, in addition to a couple ferries. 80k people live on Whidbey, and there's major shopping in Burlington, Arlington, and Mount Vernon to the north and east. It's very likely that congestion has gotten much worse in the last 10 or 20 years.

According to Historic Aerials, the intersection was changed from a Y-intersection to a T-intersection in the 70s when SR-20 and SR-20 Spur were widened to dual carriageway. No idea how long the Seagull intersection had been in place, but since at least the 90s (though probably since it was built).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 10, 2018, 02:44:05 PM
That explains a few things, although dumping turning traffic into a historically problematic intersection is an interesting solution.

Well, you could say the same thing about freeways. They localize most of the conflict points at interchanges. If you reduce the number of cars going through a specific intersection, you might reduce the chance of collisions at said intersection. But the benefits of doing so may be outweighed by the negatives of allowing added freedom of movement in other areas.

WSDOT typically studies these things to death, so I'm sure they considered the increased traffic at the roundabouts from all the U-turning traffic. If anything, it just stops traffic from entering from one of the sides that might flood the roundabout, allowing traffic to enter freely on the other side for a few moments. This is not really a major issue, but the U-turning traffic does provide a small benefit in this way.
Sure, there is such a thing as free lunch - but often in a form of cheese in a mousetrap. I wonder if right of way was an issue in setting up 2+1+2 road with a turning lane. Given it was 2 lanes to begin with - I can easily see that being a no-go.. A lot of local variables, as always..
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 10, 2018, 04:28:36 PM
That explains a few things, although dumping turning traffic into a historically problematic intersection is an interesting solution.

Well, you could say the same thing about freeways. They localize most of the conflict points at interchanges. If you reduce the number of cars going through a specific intersection, you might reduce the chance of collisions at said intersection. But the benefits of doing so may be outweighed by the negatives of allowing added freedom of movement in other areas.

WSDOT typically studies these things to death, so I'm sure they considered the increased traffic at the roundabouts from all the U-turning traffic. If anything, it just stops traffic from entering from one of the sides that might flood the roundabout, allowing traffic to enter freely on the other side for a few moments. This is not really a major issue, but the U-turning traffic does provide a small benefit in this way.

Sure, there is such a thing as free lunch - but often in a form of cheese in a mousetrap. I wonder if right of way was an issue in setting up 2+1+2 road with a turning lane. Given it was 2 lanes to begin with - I can easily see that being a no-go.. A lot of local variables, as always..

For sure. WSDOT is not quick to acquire ROW unless it's absolutely necessary. Land prices are very high in the Pacific Northwest, even out in the boonies. As the project was already delayed almost ten years, they decided to take the money they had and do what they could. Almost certainly the reason a southern under-crossing wasn't included.

A five lane road with a center turn lane might have worked (would have been tight), but you'd still have traffic turning left into the center turn lane to merge. Which is fine, but there's still that whole "turning across traffic" thing. This is obviously standard stuff on virtually all roads, but WSDOT had the opportunity to eliminate (or minimize) those left turn conflicts without harming the overall flow.

This is how the road looks now. Classic 2+1 road with a C-curb down the middle. There's room to expand on either side (if ROW were purchased), but I don't know if it would have helped the situation here. Based on the design of the southern roundabout, it looks like WSDOT has designed the project to accommodate an additional northbound lane in the future.

(https://i.imgur.com/ZSAI01h.jpg)

(https://c2.staticflickr.com/2/1759/41012956270_c81e3bf31d_b.jpg)

No idea what's going on in that second photo, BTW.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 10, 2018, 05:03:06 PM

(https://c2.staticflickr.com/2/1759/41012956270_c81e3bf31d_b.jpg)

No idea what's going on in that second photo, BTW.
Traffic wise? Truck in a roundabout, nothing to see. Tandem can probably go 3 MPH on such a roundabout - and possibly up to 5 MPH if driver is in a rush and willing to take some risk...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 10, 2018, 05:06:15 PM
(https://c2.staticflickr.com/2/1759/41012956270_c81e3bf31d_b.jpg)

No idea what's going on in that second photo, BTW.

Traffic wise? Truck in a roundabout, nothing to see. Tandem can probably go 3 MPH on such a roundabout - and possibly up to 5 MPH if driver is in a rush and willing to take some risk...

My concern was with the person standing in the roundabout (look to the right of the rear trailer). Also, there's two cars in one lane.

There appears to be a police vehicle in the median south (top side here) of the roundabout.

EDIT: I don't know if three to five miles per hour is accurate. That is walking pace, to just above walking pace. and I definitely don't think I could walk as fast as a truck maneuvers through a roundabout. It's not a fast process, but it's not walking pace.
Title: Re: Crash prone 'modern roundabouts'
Post by: skluth on July 10, 2018, 10:41:38 PM

(https://c2.staticflickr.com/2/1759/41012956270_c81e3bf31d_b.jpg)

No idea what's going on in that second photo, BTW.
Traffic wise? Truck in a roundabout, nothing to see. Tandem can probably go 3 MPH on such a roundabout - and possibly up to 5 MPH if driver is in a rush and willing to take some risk...

As someone who doesn't like tandems in the first place, I don't care if they are inconvenienced by roundabouts
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 11, 2018, 12:29:06 AM
https://c2.staticflickr.com/2/1759/41012956270_c81e3bf31d_b.jpg

No idea what's going on in that second photo, BTW.
Traffic wise? Truck in a roundabout, nothing to see. Tandem can probably go 3 MPH on such a roundabout - and possibly up to 5 MPH if driver is in a rush and willing to take some risk...

As someone who doesn't like tandems in the first place, I don't care if they are inconvenienced by roundabouts

I don't think they are. I don't even think the tandem truck has something wrong with it. Besides it's a shorter tandem.

Have you been threatened by them in the past? What's the issue with tandems?
Title: Re: Crash prone 'modern roundabouts'
Post by: davmillar on July 16, 2018, 12:45:16 AM
Still going through the thread but jumped ahead to post this. Earlier this year there was a post on the Fort Worth subreddit about some of the changes forthcoming to our road system. One is that this situation (https://goo.gl/maps/5E9vZToYnV42) around the corner from where I live is going to be replaced with a roundabout. If and when that happens I'll try to get some pics during construction and after.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 16, 2018, 01:45:20 AM
Still going through the thread but jumped ahead to post this. Earlier this year there was a post on the Fort Worth subreddit about some of the changes forthcoming to our road system. One is that this situation (https://goo.gl/maps/5E9vZToYnV42) around the corner from where I live is going to be replaced with a roundabout. If and when that happens I'll try to get some pics during construction and after.

Seems like the kind of intersection that would be prime for a roundabout. Single lane or multi lane? Street view seems to suggest that single-lane would be fine, with a couple slip lanes to maintain the multi-lane LV Trail.
Title: Re: Crash prone 'modern roundabouts'
Post by: davmillar on July 16, 2018, 08:51:13 AM
Still going through the thread but jumped ahead to post this. Earlier this year there was a post on the Fort Worth subreddit about some of the changes forthcoming to our road system. One is that this situation (https://goo.gl/maps/5E9vZToYnV42) around the corner from where I live is going to be replaced with a roundabout. If and when that happens I'll try to get some pics during construction and after.

Seems like the kind of intersection that would be prime for a roundabout. Single lane or multi lane? Street view seems to suggest that single-lane would be fine, with a couple slip lanes to maintain the multi-lane LV Trail.
Looks like 2-lane, according to the document linked from NBC DFW (https://www.nbcdfw.com/traffic/stories/Love-Them-or-Hate-Them-More-Roundabouts-Coming-to-North-Fort-Worth-476714353.html).
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 16, 2018, 01:51:00 PM
Still going through the thread but jumped ahead to post this. Earlier this year there was a post on the Fort Worth subreddit about some of the changes forthcoming to our road system. One is that this situation (https://goo.gl/maps/5E9vZToYnV42) around the corner from where I live is going to be replaced with a roundabout. If and when that happens I'll try to get some pics during construction and after.

Seems like the kind of intersection that would be prime for a roundabout. Single lane or multi lane? Street view seems to suggest that single-lane would be fine, with a couple slip lanes to maintain the multi-lane LV Trail.

Looks like 2-lane, according to the document linked from NBC DFW (https://www.nbcdfw.com/traffic/stories/Love-Them-or-Hate-Them-More-Roundabouts-Coming-to-North-Fort-Worth-476714353.html).

Very well. Here's hoping there's not too many vehicle crashes! This thread has not been too kind to multi-lane roundabouts.

If pedestrian safety improvements is the main goal, I can see the point of the roundabout. As it is, the intersection appears to be rather confusing to cross on foot, especially if someone is blind. A simplified situation could help.
Title: Re: Crash prone 'modern roundabouts'
Post by: davmillar on July 16, 2018, 08:06:08 PM
Very well. Here's hoping there's not too many vehicle crashes! This thread has not been too kind to multi-lane roundabouts.

If pedestrian safety improvements is the main goal, I can see the point of the roundabout. As it is, the intersection appears to be rather confusing to cross on foot, especially if someone is blind. A simplified situation could help.

Pedestrians are pretty used to it but there's a lot of confusion around right of way and a lot of people take the sharp right off of LVT really fast and cause near misses. A realignment and coping down those big bushes or trees would probably make it less confusing and a bit safer. Only time will tell...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 21, 2018, 02:00:34 PM
^Apart from the RV blowing through the middle of that Worthington Minnesota roundabout, there has been two other pretty major events at the roundabout over the past couple weeks.

Tanker hauling cream overturns in Worthington roundabout
(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/111117.N.DG_.TANKERCREAM%20rgb_0.jpg?itok=rxMKiQ4I)
http://www.dglobe.com/news/accidents/4356792-tanker-hauling-cream-overturns-worthington-roundabout


These little piggies almost didn't make it to market when a Minn. hog truck rolled

(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/102817.N.DG_.ROLLOVER%203.jpg?itok=DOQatmVs)
http://www.agweek.com/news/4350581-these-little-piggies-almost-didnt-make-it-market-when-minn-hog-truck-rolled

Cream trucks rolling over, hogs running around the highway, some RV driver thinking they are Bo Duke... these roundabouts really give the good people of Worthington Minnesota something to talk about!


Another vehicle vaulted over the Worthington roundabout on Sunday.  The driver sustained non-life threatening injuries.  This comes a month after an RV was videotaped launching over the roundabout in early November.

Minivan vaults over roundabout Sunday
https://www.dglobe.com/news/accidents/4375814-minivan-vaults-over-roundabout-sunday

There have been 2 truck tip-over crashes, an RV flying through the middle of the roundabout captured on video, a driver sustaining non life-sustaining injuries after his min-van flew through the middle of the roundabout, and now 4 reported crashes over a few hour period on Friday.  The roundabouts are doing a stellar job at reducing crashes in Worthington.. or maybe they are doing a worthless job.

Snowpacked roundabouts result in four crashes reported Friday
https://www.dglobe.com/news/4380839-snowpacked-roundabouts-result-four-crashes-reported-friday

Yet another semi-rollover happened at the Worthington roundabout Friday morning.

A roundabout rollover
(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/072118.N.DG_.%20Round%20about%20roll%202%20web.jpg?itok=ia9BHMPT)
http://dglobe.com/news/accidents/4475427-roundabout-rollover
Title: Re: Crash prone 'modern roundabouts'
Post by: Bruce on July 29, 2018, 10:29:26 PM
I wonder how crash-prone this roundabout is.

https://twitter.com/Streetfilms/status/1023739247826632705
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 30, 2018, 07:57:03 AM
I wonder how crash-prone this roundabout is.

https://twitter.com/Streetfilms/status/1023739247826632705
Depends on how slippery that green paint gets when it rains...
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on July 30, 2018, 08:11:20 AM
I wonder how crash-prone this roundabout is.

https://twitter.com/Streetfilms/status/1023739247826632705

The Villages, FL has some roundabouts on their golf-cart paths, two of which are https://goo.gl/maps/4rHP9DCNCLK2 and https://goo.gl/maps/5Xoxh38ThJQ2
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on July 30, 2018, 08:24:03 AM
Man, golf cart bloodbaths must be very common down there. :D
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 30, 2018, 10:17:40 AM
Can we find any pedestrian-only roundabouts?
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on July 30, 2018, 10:43:18 AM
Can we find any pedestrian-only roundabouts?

Do revolving doors count?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 30, 2018, 10:47:16 AM
(http://www.supergang.co.uk/wp-content/uploads/2013/01/roundabout.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 30, 2018, 11:03:46 AM
Can we find any pedestrian-only roundabouts?

Do revolving doors count?
Probably not as there are only 2 approaches to that traffic feature.  If revolving door is installed at the intersection of two corridors... I still have to see such an installation, though.

PS neither is a regular turnstile
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 30, 2018, 05:11:34 PM
The Villages, FL has some roundabouts on their golf-cart paths, two of which are https://goo.gl/maps/4rHP9DCNCLK2 and https://goo.gl/maps/5Xoxh38ThJQ2

Some of the nearby vehicle roundabouts have some seriously dumb striping. Mainly the three-leg roundabouts with the slip lanes.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 01, 2018, 01:50:07 PM
^Apart from the RV blowing through the middle of that Worthington Minnesota roundabout, there has been two other pretty major events at the roundabout over the past couple weeks.

Tanker hauling cream overturns in Worthington roundabout
(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/111117.N.DG_.TANKERCREAM%20rgb_0.jpg?itok=rxMKiQ4I)
http://www.dglobe.com/news/accidents/4356792-tanker-hauling-cream-overturns-worthington-roundabout


These little piggies almost didn't make it to market when a Minn. hog truck rolled

(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/102817.N.DG_.ROLLOVER%203.jpg?itok=DOQatmVs)
http://www.agweek.com/news/4350581-these-little-piggies-almost-didnt-make-it-market-when-minn-hog-truck-rolled

Cream trucks rolling over, hogs running around the highway, some RV driver thinking they are Bo Duke... these roundabouts really give the good people of Worthington Minnesota something to talk about!


Another vehicle vaulted over the Worthington roundabout on Sunday.  The driver sustained non-life threatening injuries.  This comes a month after an RV was videotaped launching over the roundabout in early November.

Minivan vaults over roundabout Sunday
https://www.dglobe.com/news/accidents/4375814-minivan-vaults-over-roundabout-sunday

There have been 2 truck tip-over crashes, an RV flying through the middle of the roundabout captured on video, a driver sustaining non life-sustaining injuries after his min-van flew through the middle of the roundabout, and now 4 reported crashes over a few hour period on Friday.  The roundabouts are doing a stellar job at reducing crashes in Worthington.. or maybe they are doing a worthless job.

Snowpacked roundabouts result in four crashes reported Friday
https://www.dglobe.com/news/4380839-snowpacked-roundabouts-result-four-crashes-reported-friday

Yet another semi-rollover happened at the Worthington roundabout Friday morning.

A roundabout rollover
(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/072118.N.DG_.%20Round%20about%20roll%202%20web.jpg?itok=ia9BHMPT)
http://dglobe.com/news/accidents/4475427-roundabout-rollover

Another semi loses his load at the Worthington roundabout on Tuesday.  This is at least the 4th semi to tip over/lose their load since October, 2017. 

Spilled grain in Worthington roundabout
(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/073118.N.TG_.%20Semi%20roll%20over%20of%20the%20week%20web.jpg?itok=uZyr2Bsy)
http://www.dglobe.com/news/accidents/4479958-spilled-grain-worthington-roundabout
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 01, 2018, 03:01:15 PM
Admittedly a poor record for such a short amount of time.

How do you find these articles? I'm not going to be condescending like others here; I'm genuinely curious.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 01, 2018, 03:47:32 PM
How do you find these articles? I'm not going to be condescending like others here; I'm genuinely curious.

Good Luck.  This question was posed just a month or so ago:  https://www.aaroads.com/forum/index.php?topic=15546.msg2337304#msg2337304 .  If you read his answer, he simply states that someone responded to his original post in this thread.  The next few posts after the question was posed (including by me), he gave some really evasive answers, then moved on to another incident.

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 01, 2018, 04:20:26 PM
I will google "roundabout" to find the latest roundabout news.  Not only is it a good way to keep track of problematic roundabouts but it also allows me to keep track of newly built roundabouts.  Doing this has allowed me to compile a roundabout database of over 5,100 modern roundabouts in America - likely one of the most comprehensive roundabout databases out there.  Since it was last updated in May 2015, I've probably compiled a couple hundred additional roundabouts.  At some point I'll clean up the data and repost the database in the thread below.   

https://www.aaroads.com/forum/index.php?topic=13278.msg2067259#msg2067259


Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 01, 2018, 06:11:18 PM
How do you find these articles? I'm not going to be condescending like others here; I'm genuinely curious.

Good Luck.  This question was posed just a month or so ago:  https://www.aaroads.com/forum/index.php?topic=15546.msg2337304#msg2337304 .  If you read his answer, he simply states that someone responded to his original post in this thread.  The next few posts after the question was posed (including by me), he gave some really evasive answers, then moved on to another incident.

I think I hit the jackpot!

I will google "roundabout" to find the latest roundabout news.  Not only is it a good way to keep track of problematic roundabouts but it also allows me to keep track of newly built roundabouts.  Doing this has allowed me to compile a roundabout database of over 5,100 modern roundabouts in America - likely one of the most comprehensive roundabout databases out there.  Since it was last updated in May 2015, I've probably compiled a couple hundred additional roundabouts.  At some point I'll clean up the data and repost the database in the thread below.   

https://www.aaroads.com/forum/index.php?topic=13278.msg2067259#msg2067259

Makes sense. Google has a great news search function, which I have used myself before many times. Though still interesting that you somehow managed to stumble upon crashes at the same roundabout over and over again. You must be searching for "Worthington roundabout" to get such specific results? Also interesting that they keep writing up stories. Not every crash makes the news, yet these roundabout crashes seem to quite often.

At the rate we're proceeding, we may overtake France and become the world's #1 builder of roundabouts at some point. While multi-lane roundabouts may lose steam, I see no sign of single-lane roundabouts dying.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on August 01, 2018, 11:14:01 PM
Though still interesting that you somehow managed to stumble upon crashes at the same roundabout over and over again. You must be searching for "Worthington roundabout" to get such specific results? Also interesting that they keep writing up stories. Not every crash makes the news, yet these roundabout crashes seem to quite often.

I think part of it is observation bias. Crashes at the roundabouts in Worthington are probably the most interesting news items in that city on a regular basis.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 02, 2018, 07:46:14 AM
Though still interesting that you somehow managed to stumble upon crashes at the same roundabout over and over again. You must be searching for "Worthington roundabout" to get such specific results? Also interesting that they keep writing up stories. Not every crash makes the news, yet these roundabout crashes seem to quite often.

I think part of it is observation bias. Crashes at the roundabouts in Worthington are probably the most interesting news items in that city on a regular basis.
More like a smaller municipality news outlet is not flooded by other news and provides a clear view of disastrous design.
 It is almost impossible to compile full crash statistics without requesting information from local authorities (police?) - and being an out-of-area activist (as opposed to someone with @fhwa.gov e-mail) makes that difficult. News don't cover each and every accident, apparently.
An intersection like one we're talking about (and looks like all 4 are on the same one, second roundabout is on a smaller road) should be in ballpark of 1 (one) crash a month. And we're told most of such accidents are property-only fender benders.
While these  may still go into property-only column, those are clearly major accidents, and having 4 in half a year is way above any statistical deviation or any justifiable range. It is a design problem.
We may go into details, but I think things are pretty clear once you look at the map, and few people from DOT should be looking for a janitorial jobs at WalMart. Would never happens, though - times of engineers standing under the new bridge are long since gone.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 02, 2018, 08:40:29 AM
More like a smaller municipality news outlet is not flooded by other news and provides a clear view of disastrous design.

In my local paper, they would print about one accident a day somewhere in the county, usually something real minor.  You know, to make it 'local'.  A crash that takes down a traffic light?  Eh, maybe it gets mentioned.  A crash on the highway shutting it down causing thousands of people to congest all the side streets, delaying everyone for an hour?  You'll never read about it.  So, it's a little funny what newspapers decide to print on.  Something that affected thousands is overlooked; something that 10 people saw as they passed by gets mentioned in the paper.

The paper did write this story one time:  A young 20-something year old was in an accident and arrested for DUI.  She wrote the reporter most likely to write something about it, begging him not to write anything so she wouldn't be embarrassed for family reasons, had a new job, etc.  So the reporter wrote a column about this request.  He looked up the accident, and admitted that even though it involved an arrest for DUI, it was otherwise a very run-of-the-mill incident that he otherwise wouldn't have even taken a second glance at.  The reporter was nice though and never mentioned the name of the person or where the incident occurred.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 02, 2018, 08:53:00 AM
More like a smaller municipality news outlet is not flooded by other news and provides a clear view of disastrous design.

In my local paper, they would print about one accident a day somewhere in the county, usually something real minor.  You know, to make it 'local'.  A crash that takes down a traffic light?  Eh, maybe it gets mentioned.  A crash on the highway shutting it down causing thousands of people to congest all the side streets, delaying everyone for an hour?  You'll never read about it.  So, it's a little funny what newspapers decide to print on.  Something that affected thousands is overlooked; something that 10 people saw as they passed by gets mentioned in the paper.

The paper did write this story one time:  A young 20-something year old was in an accident and arrested for DUI.  She wrote the reporter most likely to write something about it, begging him not to write anything so she wouldn't be embarrassed for family reasons, had a new job, etc.  So the reporter wrote a column about this request.  He looked up the accident, and admitted that even though it involved an arrest for DUI, it was otherwise a very run-of-the-mill incident that he otherwise wouldn't have even taken a second glance at.  The reporter was nice though and never mentioned the name of the person or where the incident occurred.
I wouldn't be surprised if DWI reports are viewed as a way to keep people aware of the issue and send "you will be caught, and it will be nasty" message. Makes at least some sense...
An accident that backed up highway in NJ must be a daily thing, and there is a traffic report section for that
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on August 02, 2018, 08:55:36 AM
Difficulty in acquiring the actual data does not legitimize conclusions drawn from anecdotal or incomplete data.  If you want your research to be taken seriously, do what real researchers do and jump through the hoops to get real data.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 02, 2018, 09:15:21 AM
Difficulty in acquiring the actual data does not legitimize conclusions drawn from anecdotal or incomplete data.  If you want your research to be taken seriously, do what real researchers do and jump through the hoops to get real data.
At least our truck rollovers in a same location within less than a year is NOT anecdotal data, it is clearly poor design. 
You cannot give exact numbers from this dataset - but you must admit that is is way above any expected number. In such a case case you don't need more data, you need to fire people and bulldoze the structure and work out details as reckless endagerment case is filed in a court.
I am a bit exaggerating - not too much, though. But you don't need to be a chef to tell that the steak on your plate is made from rotten meat. Nor you need bacterial DNA analysis before throwing it away.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 02, 2018, 10:27:50 AM
According to the article linked below, the 3 most crash prone intersections in Carmel are all at roundabouts along 116th Street.  Based on the data taken directly from the article I calculated the crash rates at each roundabout:

(https://i.imgur.com/oUB0vjy.png)

The average crash rate at signalized intersections is about 0.8 crashes per MEV.  The crash rate of these Carmel roundabouts are 6 to 20 times higher than the average crash rate of a standard signalized intersection.  This fact doesn’t prevent the Carmel Police Department from trying to attribute the high number of accidents at these roundabouts to the high volume of traffic going through them. 

Top 4 intersections for accidents all in Hamilton County
https://www.wishtv.com/news/i-team-8/top-four-intersections-for-accidents-all-in-hamilton-county/1273973180
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 02, 2018, 10:32:16 AM
I wouldn't be surprised if DWI reports are viewed as a way to keep people aware of the issue and send "you will be caught, and it will be nasty" message. Makes at least some sense...
An accident that backed up highway in NJ must be a daily thing, and there is a traffic report section for that

It's more like an hourly thing.  It's just expected.   They're rarely reported on.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 02, 2018, 10:47:49 AM
I wouldn't be surprised if DWI reports are viewed as a way to keep people aware of the issue and send "you will be caught, and it will be nasty" message. Makes at least some sense...
An accident that backed up highway in NJ must be a daily thing, and there is a traffic report section for that

It's more like an hourly thing.  It's just expected.   They're rarely reported on.
What I am saying is more that it may be a good idea to report a DWI in the news once in a while - preferably ones where driver faces something really nasty. You know, just to keep kids aware that it's not worth it.  Not necessarily all of those, just to keep issue on the radar.
Can be used to fill gaps on a slow day, and hopefully may be coming with return of investment via DWI rate reduction.
Same for cell phone distracted driving accident, possibly.
But overscaring the public is not worth it, so serious accidents without underlying hot issues... FOIL police reports if desired, or leave it to professionals  :pan:


Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 02, 2018, 10:49:01 AM
I wouldn't be surprised if DWI reports are viewed as a way to keep people aware of the issue and send "you will be caught, and it will be nasty" message. Makes at least some sense...
An accident that backed up highway in NJ must be a daily thing, and there is a traffic report section for that

It's more like an hourly thing.  It's just expected.   They're rarely reported on.
What I am saying is more that it may be a good idea to report a DWI in the news once in a while - preferably ones where driver faces something really nasty. You know, just to keep kids aware that it's not worth it.  Not necessarily all of those, just to keep issue on the radar.
Can be used to fill gaps on a slow day, and hopefully may be coming with return of investment via DWI rate reduction.
Same for cell phone distracted driving accident, possibly.
But overscaring the public is not worth it, so serious accidents without underlying hot issues... FOIL police reports if desired, or leave it to professionals  :pan:

Ah!  Yeah, they're definitely reported on, especially those that cause injury or death. 
Title: Re: Crash prone 'modern roundabouts'
Post by: Mr. Matté on August 02, 2018, 07:25:40 PM
I wonder how crash-prone this roundabout is.

https://twitter.com/Streetfilms/status/1023739247826632705

Can we find any pedestrian-only roundabouts?

Of course New Jersey would have a bike lane with a jughandle:
(https://i.imgur.com/MkSQWNf.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: plain on August 10, 2018, 01:58:57 AM
Of course New Jersey would have a bike lane with a jughandle:
(https://i.imgur.com/MkSQWNf.jpg)


That's the New Jerseyest thing I've seen yet.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 10, 2018, 06:15:34 AM
Of course New Jersey would have a bike lane with a jughandle:
(https://i.imgur.com/MkSQWNf.jpg)


That's the New Jerseyest thing I've seen yet.

That. Is. Awesome.

Where is this?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 13, 2018, 04:23:23 PM
^Only in New Jersey!  While we are on the topic of oddities, are these roundabout guide markings found in the MUTCD anywhere?

(https://i.imgur.com/qeGjQ4j.jpg)
https://www.google.com/maps/@41.3343067,-75.7346423,80m/data=!3m1!1e3
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 13, 2018, 04:46:58 PM
A "divergabout" opened in Lee's Summit, MO in May of this year.  It combines the complexities of a dual lane-roundabout with that of DDI.  Whoever designed this interchanges must hate me  :ded:
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 13, 2018, 05:36:54 PM
While we are on the topic of oddities, are these roundabout guide markings found in the MUTCD anywhere?

https://i.imgur.com/qeGjQ4j.jpg
https://www.google.com/maps/@41.3343067,-75.7346423,80m/data=!3m1!1e3

I have only seen them one time, and that was the Pat Bay Hwy @ McTavish Road near Sidney, BC, also a roundabout interchange:

(https://c1.staticflickr.com/7/6233/6377789351_4b9426e521_b.jpg)

A "divergabout" opened in Lee's Summit, MO in May of this year.  It combines the complexities of a dual lane-roundabout with that of DDI.  Whoever designed this interchanges must hate me  :ded:
https://www.youtube.com/watch?v=zH5EfvCdPQQ
https://www.youtube.com/watch?v=Xd4-gt9VBeI

The most revolting part about this is the mayor's insistence that the new interchange will somehow attract more retail to the area. What attracts retail is people, and I don't see how people will be attracted to a "divergabout". If they're attracted to areas with little congestion, I doubt this will somehow be the first interchange in the area without any congestion issues. And unless there's significant evidence that rebuilt interchanges routinely attract new retail, nothing will happen here anytime soon. Except maybe some new warehouses (which is fine and sort of expected when interchanges are rebuilt -- that seems to be the only part of his statement I agree with).

I am surprised how complex some interchange designs are, now. Even France, with its bizarre intersection layouts, doesn't have anything like this (though there is a close one in Versailles, with the ramps switching back right before a roundabout -- A13 @ D182).
Title: Re: Crash prone 'modern roundabouts'
Post by: skluth on August 13, 2018, 11:28:23 PM
I wonder how crash-prone this roundabout is.

https://twitter.com/Streetfilms/status/1023739247826632705

Can we find any pedestrian-only roundabouts?

Of course New Jersey would have a bike lane with a jughandle:
(https://i.imgur.com/MkSQWNf.jpg)

There's also this cycling roundabout in the Netherlands.
(https://skoda-wlc.s3.amazonaws.com/2/2016/11/worlds-first-suspended-bicycle-roundabout-hovenring-by-ipv-delft-netherlands-1.jpg)
https://www.welovecycling.com/wide/2016/11/02/dutch-built-elevated-roundabout-just-bikes/ (https://www.welovecycling.com/wide/2016/11/02/dutch-built-elevated-roundabout-just-bikes/)
[/url]
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 14, 2018, 12:30:41 PM
Since 2005, 7 triple-lane roundabouts have been built in Michigan.  Many of these have since been downsized to double-lane roundabouts and only 3 triple-lane roundabouts remain (18 ½ Mile & Van Dyke; Orchard Lake @ 14 Mile; Martin Pkwy/M-5 @ Pontiac Trail).  Of these 3 triple-lane roundabouts they all made it in the top 5 most crash prone intersections in Michigan for 2017.  Collectively these 3 triple-lane roundabouts experienced 451 crashes last year including 46 injury crashes.  With safety statistics like that, is it any wonder that over half of the triple-lane roundabouts built in Michigan since 2005 have already been downsized?
 
(https://i.imgur.com/eMBYNl5.png)
https://www.michiganautolaw.com/blog/2018/05/07/top-20-most-dangerous-mi-intersections/

Another complex triple-lane roundabout at Richmond & Northland in Appleton, Wisconsin was built last year and is approaching one full year of operation.  An article reporting on the early crash data back in February found that there had already been 77 crashes since opening on September 1st.  At that pace the roundabout was on track to experience 181 crashes.  Considering the intersection averaged about 27 crashes/year before the roundabout was built, that's a pretty massive jump (even if the crashes remained at 77).  Now people will say "yeah, but it's only the first year and crashes will go down moving forward".  But just consider that the roundabout at 18 1/2 Mile and Van Dyke was built in 2005 and still experienced 165 crashes last year (including 13 injury crashes).  I wouldn't be at all surprised if the Richmond & Northland roundabout experiences 100+ crashes/year for the foreseeable future.
Title: Re: Crash prone 'modern roundabouts'
Post by: Brian556 on August 14, 2018, 01:05:20 PM
Of course New Jersey would have a bike lane with a jughandle:
(https://i.imgur.com/MkSQWNf.jpg)


That's the New Jerseyest thing I've seen yet.

Is that stop sign for vehicular traffic or is it improperly used the mark the end of the wider pavement? The lack of a stop bar, along with its far-forward placement in the intersection makes this situation very unclear
Title: Re: Crash prone 'modern roundabouts'
Post by: plain on August 14, 2018, 01:37:20 PM
Of course New Jersey would have a bike lane with a jughandle:
(https://i.imgur.com/MkSQWNf.jpg)


That's the New Jerseyest thing I've seen yet.

Is that stop sign for vehicular traffic or is it improperly used the mark the end of the wider pavement? The lack of a stop bar, along with its far-forward placement in the intersection makes this situation very unclear

Definitely for bicyclists, not motorists. Basically it's a way to get bicyclists to stop and look before crossing the street here. May would help somewhat if this had a "bicycle" sign or something mounted here too though.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 14, 2018, 02:13:43 PM
Now people will say "yeah, but it's only the first year and crashes will go down moving forward".  But just consider that the roundabout at 18 1/2 Mile and Van Dyke was built in 2005 and still experienced 165 crashes last year (including 13 injury crashes).

It is rather embarrassing that drivers still have such a hard time figuring it out. Maybe if there were more of them? I know Carmel still has a hard time, but one could easily just blame tourists for all the crashes.

I still think the only realistic option to improve roundabout safety is to just put them in everywhere. Of course, if that's actually rather unrealistic, we should probably give up.

What's going on at that Van Dyke/I-696 intersection? Looks pretty well designed to me. I would have to assume side-swipe crashes where the off-ramps meet 11 Mile are the main issue.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 14, 2018, 02:15:55 PM
^Only in New Jersey!  While we are on the topic of oddities, are these roundabout guide markings found in the MUTCD anywhere?

(https://i.imgur.com/qeGjQ4j.jpg)
https://www.google.com/maps/@41.3343067,-75.7346423,80m/data=!3m1!1e3
Probably would fall under Section 3B.20. Symbol marks are permitted, with no closed list of symbols. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 14, 2018, 02:31:02 PM
Now people will say "yeah, but it's only the first year and crashes will go down moving forward".  But just consider that the roundabout at 18 1/2 Mile and Van Dyke was built in 2005 and still experienced 165 crashes last year (including 13 injury crashes).

It is rather embarrassing that drivers still have such a hard time figuring it out. Maybe if there were more of them? I know Carmel still has a hard time, but one could easily just blame tourists for all the crashes.

I still think the only realistic option to improve roundabout safety is to just put them in everywhere. Of course, if that's actually rather unrealistic, we should probably give up.

What's going on at that Van Dyke/I-696 intersection? Looks pretty well designed to me. I would have to assume side-swipe crashes where the off-ramps meet 11 Mile are the main issue.

(repeating same old tune) general purpose roads are built to be used by regular folks - not by NASCAR drivers, not by roadgeeks, not top 5% drivers exclusively. If road design cannot accommodate 70 year old uncle Tom, then it is a design problem - not uncle Tom's problem. Putting them everywhere is exactly the problem - your doctor doesn't prescribe insulin to every patient. Insulin can be a lifesaver, or a killer, you need to THINK, not blindly build roundabout as a first choice.

I don't like roundabouts, as you may notice. You may blame me for lack of experience - I don't drive them a lot, just through 7 on my daily commute and another 5-6 when I do grocery shopping, and a few on errands. Total of only 50-70, at most 100 passes a week over past few years. Still think most of them are poorly designed.... Maybe I need more practice?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 14, 2018, 03:08:16 PM
(repeating same old tune) general purpose roads are built to be used by regular folks - not by NASCAR drivers, not by roadgeeks, not top 5% drivers exclusively. If road design cannot accommodate 70 year old uncle Tom, then it is a design problem - not uncle Tom's problem. Putting them everywhere is exactly the problem - your doctor doesn't prescribe insulin to every patient. Insulin can be a lifesaver, or a killer, you need to THINK, not blindly build roundabout as a first choice.

I don't like roundabouts, as you may notice. You may blame me for lack of experience - I don't drive them a lot, just through 7 on my daily commute and another 5-6 when I do grocery shopping, and a few on errands. Total of only 50-70, at most 100 passes a week over past few years. Still think most of them are poorly designed.... Maybe I need more practice?

If you hate them because of your experience with other drivers, that's fair. If you hate them because you don't understand them... that's an issue.

I personally like them only where their use makes sense. Just recently, we talked about the WA-20 (Sharpes Corner) roundabouts, and how they were installed to facilitate U-turn maneuvers along a newly-divided stretch of road. They make sense in a situation like this, and from my experience driving them, anything else would have taken up too much room or wouldn't work as well (rural traffic is more random arrival, which is better for roundabouts or fully permissive signals). Compared to the old signal, traffic was moving much better. But, driving around (between the two 7 times in about 20 minutes), I did notice a few close calls. Not collisions, just close calls. This could indicate that actual collisions will be an issue, but we'll have to wait and see. One of the roundabouts is along a popular road linking I-5 to a ferry, with lots of tourists.

Not disagreeing that intersections should be designed to facilitate the movement of driver's of all backgrounds. But drivers of all backgrounds are more readily familiar with the most common types of intersections, of which the roundabout is not one. Signals are a part of nearly all communities across the US, so pretty much all licensed American drivers know how they work because they see one every day. That is not true for roundabouts. Carmel has tons of roundabouts, but Indianapolis has almost none. Any non-Carmel-based driver in Carmel is going to drive through a roundabout, and for our sake, let's hope they can figure out how they work. They'd understand them better if they were used to seeing them. It doesn't take a genius to work that out.

And as I said in my post, roundabouts may not be a realistic solution for all intersections. And if the plan is to slow down how many roundabouts are being installed, we should probably abandon the concept altogether. There are still too many Americans who never see them, and who might be confused or just unphased by the intersection style (and enter in such a way as to unintentionally cause as much carnage as possible -- drifting across lanes, failing to yield, etc). Signals generally work well because they are familiar. Not straightforward. Plenty of signals have bizarre layouts or curves. DDIs, for instance, or Michigan Lefts, but most work OK because drivers are familiar with RYG indications.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 14, 2018, 03:16:32 PM
Now people will say "yeah, but it's only the first year and crashes will go down moving forward".  But just consider that the roundabout at 18 1/2 Mile and Van Dyke was built in 2005 and still experienced 165 crashes last year (including 13 injury crashes).

It is rather embarrassing that drivers still have such a hard time figuring it out. Maybe if there were more of them? I know Carmel still has a hard time, but one could easily just blame tourists for all the crashes.

I still think the only realistic option to improve roundabout safety is to just put them in everywhere. Of course, if that's actually rather unrealistic, we should probably give up.

What's going on at that Van Dyke/I-696 intersection? Looks pretty well designed to me. I would have to assume side-swipe crashes where the off-ramps meet 11 Mile are the main issue.

(repeating same old tune) general purpose roads are built to be used by regular folks - not by NASCAR drivers, not by roadgeeks, not top 5% drivers exclusively. If road design cannot accommodate 70 year old uncle Tom, then it is a design problem - not uncle Tom's problem. Putting them everywhere is exactly the problem - your doctor doesn't prescribe insulin to every patient. Insulin can be a lifesaver, or a killer, you need to THINK, not blindly build roundabout as a first choice.

I don't like roundabouts, as you may notice. You may blame me for lack of experience - I don't drive them a lot, just through 7 on my daily commute and another 5-6 when I do grocery shopping, and a few on errands. Total of only 50-70, at most 100 passes a week over past few years. Still think most of them are poorly designed.... Maybe I need more practice?

It helps to know why you think they're poorly designed.  If you're getting thru them unscathed, doesn't sound like you're doing anything wrong.  If you are getting honked yet, then you're probably doing something wrong!
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 14, 2018, 03:22:50 PM


If you hate them because of your experience with other drivers, that's fair. If you hate them because you don't understand them... that's an issue.

I personally like them only where their use makes sense.
shaking your hand without reading any further. That is exactly my issue, roundabouts built just because - even where adding a turn lane would make things work nicely for a much smaller amount of money (money coming from my taxes after all).
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 14, 2018, 04:06:22 PM
If you hate them because of your experience with other drivers, that's fair. If you hate them because you don't understand them... that's an issue.

I personally like them only where their use makes sense.
shaking your hand without reading any further. That is exactly my issue, roundabouts built just because - even where adding a turn lane would make things work nicely for a much smaller amount of money (money coming from my taxes after all).

My bolded point was an attempt to find middle ground. I don't think roundabouts are appropriate for all intersections, but we'd both agree that signals are not appropriate for all either.

You know as well as I do that roundabouts are usually installed to "improve safety", not flow (although I view it as the main benefit, as collisions do seem to become an issue). Improving the signal, as far as some DOTs are concerned, is "putting lipstick on a pig". The argument is not usually "add a turn lane here, or build a roundabout". It's "this signal has a poor safety record, let's install a roundabout".

Now, are these DOT's going off false information? It certainly seems that way! But to tie into my previous post (most of which you seem to have ignored), the safety records of roundabouts could very well be tied to driver unfamiliarity. Of the 165 crashes at the Sterling Heights roundabout (above), how do we know they weren't all drivers who had never seen a roundabout? Your argument is that signals work well because drivers understand them. My argument is (potentially) the same for roundabouts: they would work well if more drivers were familiar with them. Not just the ones who use it every day: all drivers. That's only conceivable if roundabouts become as common as signals. If that's not conceivable, we need to stop installing them immediately.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 14, 2018, 04:40:09 PM

Not disagreeing that intersections should be designed to facilitate the movement of driver's of all backgrounds. But drivers of all backgrounds are more readily familiar with the most common types of intersections, of which the roundabout is not one. Signals are a part of nearly all communities across the US, so pretty much all licensed American drivers know how they work because they see one every day. That is not true for roundabouts. Carmel has tons of roundabouts, but Indianapolis has almost none. Any non-Carmel-based driver in Carmel is going to drive through a roundabout, and for our sake, let's hope they can figure out how they work. They'd understand them better if they were used to seeing them. It doesn't take a genius to work that out.

And as I said in my post, roundabouts may not be a realistic solution for all intersections. And if the plan is to slow down how many roundabouts are being installed, we should probably abandon the concept altogether. There are still too many Americans who never see them, and who might be confused or just unphased by the intersection style (and enter in such a way as to unintentionally cause as much carnage as possible -- drifting across lanes, failing to yield, etc). Signals generally work well because they are familiar. Not straightforward. Plenty of signals have bizarre layouts or curves. DDIs, for instance, or Michigan Lefts, but most work OK because drivers are familiar with RYG indications.

You know, there is one fundamental difference between roundabouts and traffic lights: traffic lights mostly provide positive right of way for most traffic. Left turns or rights on red is when you don't have positive right of way - and both are moves that are associated with elevated risk. Mostly because those require quick analysis of oncoming traffic and a quick action. I saw drivers who refuse to turn on red, and many of them have gray hair.  Moreover,  multilane roundabouts, ones which our friend Trade really hates, require looking at multiple lanes of traffic, which can flow out of tune. Possibility of a costly mistake becomes even higher... 

There are other situations where drivers have to yield without an option - stop signs, highway entrances - but stops are usually associated with low speed and/or low traffic volume, and same people who avoid turns on red also responsible for "avoid freeways" option in Waze. Roundabouts are often hard to avoid.

So, where I was heading? Ah, ok, the message is: roundabout brings yield issues and associated stress and possibility of mistake where design can eliminate those issues, especially on busy roads. And, if you ask me, it is often too much stress for too little gain overall.
 Roundabouts, by design, are a gamble - would that car exit? Would this car stop (as it should, or driver assumed I am exiting)? Do I have enough room? Is there a pedestrian behind that nicely obscuring vegetation on the island (obscuring the view by design)? THis is all OK with 5 cars a minute intersection, but roundabouts a build to handle 10x that traffic.
I would say I am in my best years right now, and I can handle the issue - but I still don't like it. Would I be able to handle this when I am in same age group as uncle Tom currently is? We will see. I would be swearing even more than today, that's for sure.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 14, 2018, 04:55:46 PM

Now, are these DOT's going off false information? It certainly seems that way! But to tie into my previous post (most of which you seem to have ignored), the safety records of roundabouts could very well be tied to driver unfamiliarity. Of the 165 crashes at the Sterling Heights roundabout (above), how do we know they weren't all drivers who had never seen a roundabout? Your argument is that signals work well because drivers understand them. My argument is (potentially) the same for roundabouts: they would work well if more drivers were familiar with them. Not just the ones who use it every day: all drivers. That's only conceivable if roundabouts become as common as signals. If that's not conceivable, we need to stop installing them immediately.
Frankly speaking, who would work as an engineer who's biggest achievement in a career is rebuilding an intersection according to 50 year old buleprints? That seems to be the case for many NYSDOT folks. I suspect there are few, if any, people able to design things based on knowledge and experience, not on "just because".

As for drivers.. assuming a newcomer has 100x higher chance  of crashing (which is generous), and a ballpark design target of 1 crash per 1 million vehicles, those 1000 crashes in Trade's table should be enough to ensure that 10 million drivers are now familiar with roundabouts. Since it one year data only, this thread goes on for a few years, and there are few more states having high event count on roundabouts - there should be no problems effective tomorrow as everyone in US now had a chance to meet the miracle and narrowly avoid an accident - or participate in one....  Would you bet $20 on that?
Title: Re: Crash prone 'modern roundabouts'
Post by: skluth on August 14, 2018, 05:12:53 PM

But drivers of all backgrounds are more readily familiar with the most common types of intersections, of which the roundabout is not one.

I deleted the rest of the quote because this line stuck out like a DDI in rural Kansas.

Why do you think roundabouts are an uncommon intersection? I've seen them since I was a kid and I'm 62. I didn't see them often when I was first driving, but I had seen a few, mostly in parks and bigger cities. I thought they were fun when my dad drove through them and loved how easy they were from the first time I used one. I enjoyed their utility when I was stationed in Spain. I think most of the people who hate them are the same get-off-my-lawn types who don't turn right on red even if you can see no vehicles for blocks.

Are there badly designed or misplaced roundabouts? Sure. I've been on a few. But they're common enough that people need to accept that knowing how to drive in one should be a requirement for driving. They're far more common now and when properly done greatly improve both safety and traffic throughput. I think the main problem is some whiny drivers don't want to think at all when driving or are too busy doing something else, and roundabouts aren't very forgiving of those types.

The only reason you might think they're uncommon is they aren't around you. By that logic, a citizen of Houghton MI could claim freeways were uncommon because the nearest is about 200 miles distant. But there's a roundabout in Marquette. Not close, but a lot closer than any freeway. You can go a lot of places and find roundabouts. Not any less uncommon than freeways.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 15, 2018, 11:44:48 AM
According to data from the Indiana State Police included in the article below, the Carmel roundabouts at 116th @ Illinois and 116th @ Pennsylvania have crash rates of 13.5 MEV and 16.28 MEV respectively.  Considering the average crash rate of signalized intersections is about 0.8 MEV, these Carmel roundabouts are seeing 16x to 20x more crashes than that what a typical signalized intersection would.  In addition, these roundabouts are well inside the city limits of Carmel meaning that drivers would have had to circulate through other Carmel roundabouts before circulating through the crash prone roundabouts along 116th.  I don't believe the high number of crashes at these Carmel roundabouts can be excused away by driver unfamiliarity.  Maybe some drivers in Carmel still don't know what the hell they are doing even after driving through hundreds of roundabouts in the city, but i don't believe they are unfamiliar with them (ie. never drive through them).  Even Indianapolis residents who rarely visit Carmel should have some experience driving through roundabouts as there are currently about 10 modern roundabouts in Marion County (including a multi-lane roundabout right next to Indianapolis Motor Speedway). 

Quote
Top 4 intersections for accidents all in Hamilton County
https://www.wishtv.com/news/i-team-8/top-four-intersections-for-accidents-all-in-hamilton-county/1273973180

I do think driver education is needed.  When you think about it, it's actually pretty complicated to teach drivers how to properly drive through a roundabout, especially for east coast drivers who are use to driving around large traffic circles.  In a traffic circle the circle is the main roadway and a "straight arrow" would mean to continue around the circle... in a modern roundabout the circle acts as an intersection, and a straight arrow means to exit the circle.  To most drivers a circle is a circle.. and some modern roundabouts have large diameters that mimic large traffic circles.  In that case how is a driver to know when they are driving through a modern roundabout and when they are driving a traffic circle?  As long as drivers get confused with the meaning of something as simple as a "straight arrow" sign, crashes will inevitably continue.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 15, 2018, 03:22:43 PM
Below is an updated roundabout database which includes roughly 6,000 roundabouts in America.  There will be 10,000 roundabouts in America within 10 years assuming they continue to be built at their current pace (ie. about 400-500 per year).

http://www.mediafire.com/file/ashf2dt18zac1ly/Modern_Roundabouts_%282018-Aug%29.kmz/file
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 15, 2018, 05:09:54 PM
So, where I was heading? Ah, ok, the message is: roundabout brings yield issues and associated stress and possibility of mistake where design can eliminate those issues, especially on busy roads. And, if you ask me, it is often too much stress for too little gain overall.

Yielding is still an inherent part of traffic lights. The flashing yellow arrow has become immensely popular over the last ten years, due to its ability to reduce wait times and reduce collisions associated with those long waits. I'm sure if you asked Trade, he would not be for protected-only left and right turns across our road network (if yielding is too much for drivers to handle).

I would not say that they're a useless feature, but sometimes, black-and-white road regulations can create disobedient drivers who feel like the government is trying too hard to control them, or that the government doesn't know what's best. California has by far the worst red-light-runners that I've ever seen, and it just so happens that virtually all left turns in California are protected only. Coincidence? I think not.

But drivers of all backgrounds are more readily familiar with the most common types of intersections, of which the roundabout is not one.

Why do you think roundabouts are an uncommon intersection?

I don't know how many traffic lights there are in the US. The only way I could figure it out was guessing based on the limited data I have available:

There are 3035 signalized intersections in Chicago proper, with its population of 2.705 million. That works out to one traffic light for every 891 residents. Dividing that by the population of the US (325.7 million), and you get 365,544 signals. That's very sketchy math, but it's the best I can do right now. According to Trade, there are about 6000 roundabouts in the US.

So,

365,544/6000 = 60.7 signals per roundabout. I think a fair conclusion, from that very basic math, is that roundabouts are nowhere near as common as signals. Obviously, the most common intersection is the stop sign, but at intersections that warrant a some form of four-way traffic control beyond stop signs, you're far more likely to encounter a signal than a roundabout.

Of course, in some states, some cities over-represent roundabouts. I don't know how many roundabouts are in Indiana, but I bet about 90% of them are in Carmel. If roundabouts were spread out a bit more, there might be better opportunity for drivers to practice them.

As it just so happens, you are correct: I have very few roundabouts near me. But I live in a metro area with a population of 3.7 million. How many of us never regularly encounter a roundabout? Probably most. When we do run into one, usually out in the country, we don't have much of any practice or experience to go off. So we just have to do our best. Sometimes, that is asking a lot of drivers.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 15, 2018, 06:16:58 PM
So, where I was heading? Ah, ok, the message is: roundabout brings yield issues and associated stress and possibility of mistake where design can eliminate those issues, especially on busy roads. And, if you ask me, it is often too much stress for too little gain overall.

Yielding is still an inherent part of traffic lights. The flashing yellow arrow has become immensely popular over the last ten years, due to its ability to reduce wait times and reduce collisions associated with those long waits. I'm sure if you asked Trade, he would not be for protected-only left and right turns across our road network (if yielding is too much for drivers to handle).

I would not say that they're a useless feature, but sometimes, black-and-white road regulations can create disobedient drivers who feel like the government is trying too hard to control them, or that the government doesn't know what's best. California has by far the worst red-light-runners that I've ever seen, and it just so happens that virtually all left turns in California are protected only. Coincidence? I think not.

Of course, there are yields around, and we do fine with them. 
Basically the question is when yield-controlled option  is feasible, and when mandatory yield-controlled move is feasible.
Trade's message effectively is that yield to 1 lane is OK,  yield to 2 lanes is acceptable, yield to 3 lanes is a no-go. Do you think there are any FYAs with 3 lanes of oncoming traffic?

My message is a bit more tricky. For an intersection with unequal arms (What I have in mind is a pair of circles on a local  EW arterial near interstate exit, circles are placed  where NS side collectors join arterial) yielding becomes unnecessary more involved. Let me try to elaborate....
With light (or side road stop) controlled  intersection, through traffic (WE and EW) clearly goes into separate no-yield group. And that EW is a majority group given the traffic distribution. Any yielding/yield to traffic is clearly identified by position on the road (and blinkers, although that is less certain); especially with dedicated turn lanes.
In case of roundabout, separation becomes much less certain - and through EW traffic  should be prepared to yield to oncoming through WE traffic. I am actually somewhat a victim of this, as I make a left turn (Westbound>south) on one of those circles - and invariably oncoming WE drivers expect me to continue straight like 95% of traffic does. At least twice a week someone has to step on brakes to let me use my right of way - and I slow down in case their brakes  are not as good as they think. I really think that is the highest accident probability on my commute.
Opposite problem - but another side of the same coin - is WE drivers stopping and yielding to straight-through EW traffic when there is no conflict. But there is a 5% chance that driver is making a turn... 

This wouldn't be an issue on a bigger circle, but intense desire to shoehorn them everywhere is also a part of a problem. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 15, 2018, 07:25:03 PM
Of course, there are yields around, and we do fine with them. 
Basically the question is when yield-controlled option  is feasible, and when mandatory yield-controlled move is feasible.
Trade's message effectively is that yield to 1 lane is OK,  yield to 2 lanes is acceptable, yield to 3 lanes is a no-go. Do you think there are any FYAs with 3 lanes of oncoming traffic?

Oh my god, yes. They're everywhere around here. More than a few across four lanes (such as here: northbound WA-99 @ WA-509 (https://goo.gl/8oAYUX)). Kennewick, WA has a double left FYA against three lanes (here: Hildebrand Blvd @ Plaza Way (https://goo.gl/4HAEPR)). From the data I've read (I can provide links), they both work very well. Vancouver (BC) also has one identical to the Kennewick intersection (here: northbound Main St onto the Dunsmuir Viaduct (https://goo.gl/hPNWVw)). BC is full of permissive lefts across three lanes, many without any protected phasing.

Part of the reason these seem to work well is that they reduce overall delay, so drivers aren't as pushy or risky as they might otherwise be. Another part, at least compared to roundabouts, is that drivers have seen permissive left turns before, so they usually have a good idea of what to do. Not everyone, obviously, as crashes are a part of all intersections, but overall available data seems to suggest fairly high levels of understanding (particularly in the case of the FYA, which apparently is so well understood, the FHWA didn't see the need for a nationwide supplemental sign).

My message is a bit more tricky. For an intersection with unequal arms (What I have in mind is a pair of circles on a local  EW arterial near interstate exit, circles are placed  where NS side collectors join arterial) yielding becomes unnecessary more involved. Let me try to elaborate....
[clipped]

This is a serious issue with small roundabouts. Roundabout traffic models, from the few I've seen, show drivers entering and exiting the roundabouts along the arterial, having barely slowed down at all (seemingly knowing exactly what every other car is going to do), but when a car actually does turn left, suddenly that entry leg slows down to allow them to make their left turn, before proceeding again at-speed. The problem, of course, is that drivers don't actually do that; everybody looks left, I think, but perhaps are caught off-guard when a car actually starts to head towards them, since they (apparently) weren't expecting it. So drivers sometimes have to brake hard or awkwardly (certainly not smoothly). I could see collisions happening this way, especially outside lane vs circulating traffic, since the outside lane's visibility of the circle is worse than the inside lane, and drivers might be tempted to just follow drivers through (also an issue at permissive left turns, but I can think of several ways to fix this).

This wouldn't be an issue on a bigger circle, but intense desire to shoehorn them everywhere is also a part of a problem.

True. If circles were larger, it would be very clear who you are supposed to yield to. You could basically ignore all traffic on the other side, since they're 5+ seconds away from being a worry. But for some strange reason, agencies seem hell-bent on these tiny roundabouts with low speeds. We should really consider dropping the "low speed" requirement for "modern roundabouts".
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 16, 2018, 08:16:33 AM
Quote from: jakeroot link=topic=15546.msg2349683#msg2349683
(clipped with huge scissors)
My impression is that the main difference between us here is that a glass is half-empty for me, but half full for you. You believe yield issues can be resolved - I believe they shouldn't be created to begin with; you believe that small roundabouts are a problem of agencies - I think the problem lies with the concept of rebuilding smaller intersections where there is not enough footprint available (and I mentioned few pages back how roundabouts are a dead end in reconstruction sequence)...

As for FYAs and multilanes.. WOuld be interesting to see how things would look like once there is more statistical data...
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on August 16, 2018, 09:05:06 AM
We should really consider dropping the "low speed" requirement for "modern roundabouts".

I can almost guarantee that will never happen. There is a direct relationship between speed and amount of injury. Lower speeds and traffic "calming" have been high on the list of benefits of modern roundabouts since the beginning. Raise the speeds and your pretty-damn close to the rotaries that many are trying get rid of.

Overall, there's still a huge educational gap with roundabouts, especially multilane versions. FYAs aren't much different in that regard, but are arguably more intuitive to the new user. Consider this: there are 19 states that do not require formal driver education, according to the Washington State Legislature (http://leg.wa.gov/JTC/Documents/Studies/Driver%20Education_Beth/SummaryStateTable.pdf). We have new drivers in 19 states largely basing their driving habits on their parents or guardians and what they see in GTA. Even in the states that do require formal driver education, roundabouts still aren't necessarily part of their DE's manuals.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 16, 2018, 09:30:59 AM


Overall, there's still a huge educational gap with roundabouts, especially multilane versions. FYAs aren't much different in that regard, but are arguably more intuitive to the new user. Consider this: there are 19 states that do not require formal driver education, according to the Washington State Legislature (http://leg.wa.gov/JTC/Documents/Studies/Driver%20Education_Beth/SummaryStateTable.pdf). We have new drivers in 19 states largely basing their driving habits on their parents or guardians and what they see in GTA. Even in the states that do require formal driver education, roundabouts still aren't necessarily part of their DE's manuals.
I don't buy that. I am from the state where pre-license course is mandatory. Roundabouts were discussed in my class, which was way before current construction fever. As I said, I have about 2-3k/year, or a total of 10,000+ passes through roundabouts as a driver by now; I have seen 1 (one) total screwup. No accident, though. Most cases of confusion are with people who err on the side of undue caution (yielding while in circulating lane, mostly) and would not lead to accidents. There is a noticeable amount of "f#ck you and your right of way" folks - but that is more or less consistent with what I see on busy stop signs in quantity and driving style. Overall you may assume that drivers know the rules, but sometimes caught with unexpected traffic. Local media also did its part in educating drivers,
Yet we do have some accident prone roundabouts, though... 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 16, 2018, 11:18:29 AM
There are 3035 signalized intersections in Chicago proper, with its population of 2.705 million. That works out to one traffic light for every 891 residents. Dividing that by the population of the US (325.7 million), and you get 365,544 signals. That's very sketchy math, but it's the best I can do right now. According to Trade, there are about 6000 roundabouts in the US.

Your estimate sounds pretty close Jake.  In 2007 the FHWA estimated that there were about 311,000 traffic signals in America and at that time there were about 301 million people in America.  That turns out to be one traffic light for every 967 residents.  Assuming that same ratio, at 325 million people there would be about 336,000 traffic signals today.  The FHWA might estimate the total number of roundabouts at 4000-4500 as they probably wouldn't consider all the private subdivision roundabouts in that database i linked; and rather focus on city, county, and state roundabouts.  Out of 100 traffic signals, if one or two of them are converted to roundabouts that seems reasonable and nationally that's the ratio we are seeing.  But you look at a place like Carmel, where 90% of the traffic signals are being converted to roundabouts, they are coo coo for cocoa puffs. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 16, 2018, 09:23:31 PM
Saying that a roundabout forces drivers to slow down is as silly as saying that a red light forces drivers to stop.  Yes, someone can post videos of drivers blowing through red lights too, but a driver blowing through a roundabout without slowing can be extremely dangerous.  WARNING!  These are graphic videos of serious roundabout crashes.


Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 16, 2018, 10:15:45 PM
Saying that a roundabout forces drivers to slow down is as silly as saying that a red light forces drivers to stop.  Yes, someone can post videos of drivers blowing through red lights too, but a driver blowing through a roundabout without slowing can be extremely dangerous.  WARNING!  These are graphic videos of serious roundabout crashes.



Looks like everyone walked away from the truck accident.

You're seriously trying too hard now to posts these accidents.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 16, 2018, 11:43:06 PM
Saying that a roundabout forces drivers to slow down is as silly as saying that a red light forces drivers to stop.  Yes, someone can post videos of drivers blowing through red lights too, but a driver blowing through a roundabout without slowing can be extremely dangerous.  WARNING!  These are graphic videos of serious roundabout crashes.



Looks like everyone walked away from the truck accident.

You're seriously trying too hard now to posts these accidents.

You are right Jeff, it was reported that nobody was seriously injured in the accident and the victims were taken to hospital with only cuts and bruises. 
https://www.newsflare.com/video/206128/crime-accidents/motorcyclists-escape-death-after-truck-smashes-into-traffic-island-and-flattens-them

In researching the crash i had accidentally typed "May 15 2008 Cambodia roundabout crash" (instead of May 15, 2018 which is the timestamp in the video).   The first google result was a news headline about a bus in Hong Kong that lost control in a roundabout in 2008 and killed 18 people.  According to the article it was the worst traffic accident in Hong Kong in 5 years.

Quote
A bus driver was being held for questioning by police last night after Hong Kong's worst traffic accident in five years left 18 people dead and 44 injured - including a dozen who were fighting for their lives.  The bus, carrying worshippers to the monthly gathering of a religious sect, went out of control at a Sai Kung roundabout, flipped on its side and rammed into a noise barrier. The roof was crushed and seats bent, trapping the dead and injured.
https://www.scmp.com/article/636047/speeding-blamed-bus-crash-kills-18

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 16, 2018, 11:55:21 PM
To summarise the two sides here:

- You can fuck up at a signal and get away unscathed, but
- You can't fuck up at a roundabout and get away without at least some property damage.

There are 3035 signalized intersections in Chicago proper, with its population of 2.705 million. That works out to one traffic light for every 891 residents. Dividing that by the population of the US (325.7 million), and you get 365,544 signals. That's very sketchy math, but it's the best I can do right now. According to Trade, there are about 6000 roundabouts in the US.

Your estimate sounds pretty close Jake.  In 2007 the FHWA estimated that there were about 311,000 traffic signals in America and at that time there were about 301 million people in America.  That turns out to be one traffic light for every 967 residents.  Assuming that same ratio, at 325 million people there would be about 336,000 traffic signals today.  The FHWA might estimate the total number of roundabouts at 4000-4500 as they probably wouldn't consider all the private subdivision roundabouts in that database i linked; and rather focus on city, county, and state roundabouts.  Out of 100 traffic signals, if one or two of them are converted to roundabouts that seems reasonable and nationally that's the ratio we are seeing.  But you look at a place like Carmel, where 90% of the traffic signals are being converted to roundabouts, they are coo coo for cocoa puffs. 

Rarely is my "estimation" math correct, so I'm glad I was on the right track here.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 17, 2018, 06:56:35 AM
To summarise the two sides here:

- You can fuck up at a signal and get away unscathed, but
- You can't fuck up at a roundabout and get away without at least some property damage.
The main selling point is different, though
- You can fuck up at a signal and get away unscathed, or your dead body may be hauled from the accident scene. but
- You can't fuck up at a roundabout and get away without at least some property damage, but chances are you will live to report that to your insurance
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 17, 2018, 01:33:30 PM
To summarise the two sides here:

- You can fuck up at a signal and get away unscathed, but
- You can't fuck up at a roundabout and get away without at least some property damage.
The main selling point is different, though
- You can fuck up at a signal and get away unscathed, or your dead body may be hauled from the accident scene. but
- You can't fuck up at a roundabout and get away without at least some property damage, but chances are you will live to report that to your insurance

Very true.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on August 17, 2018, 02:04:12 PM
The main selling point is different, though
- You can fuck up at a signal and get away unscathed, or your dead body may be hauled from the accident scene. but
- You can't fuck up at a roundabout and get away without at least some property damage, but chances are you will live to report that to your insurance

Depends on your definition of fuck up. Is fucking up using the incorrect lane or is it attempting to go straight thru the central island? Can "near misses" be classified as fuck ups? Based on those definitions, I'd say it is possible to fuck up at a roundabout and get out unscathed.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 17, 2018, 02:07:24 PM
The main selling point is different, though
- You can fuck up at a signal and get away unscathed, or your dead body may be hauled from the accident scene. but
- You can't fuck up at a roundabout and get away without at least some property damage, but chances are you will live to report that to your insurance

Depends on your definition of fuck up. Is fucking up using the incorrect lane or is it attempting to go straight thru the central island? Can "near misses" be classified as fuck ups? Based on those definitions, I'd say it is possible to fuck up at a roundabout and get out unscathed.

If you don't live, tradephoric will find the news story and publish it here!
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 17, 2018, 02:34:27 PM
To summarise the two sides here:

- You can fuck up at a signal and get away unscathed, but
- You can't fuck up at a roundabout and get away without at least some property damage.
The main selling point is different, though
- You can fuck up at a signal and get away unscathed, or your dead body may be hauled from the accident scene. but
- You can't fuck up at a roundabout and get away without at least some property damage, but chances are you will live to report that to your insurance

Very true.

Maybe yes, maybe no. Roundabout under my window had 0 fatalities in 10 years before being built, and 1 - or may be 2 - in 10 years since built.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 17, 2018, 07:36:24 PM
To summarise the two sides here:

- You can fuck up at a signal and get away unscathed, but
- You can't fuck up at a roundabout and get away without at least some property damage.
The main selling point is different, though
- You can fuck up at a signal and get away unscathed, or your dead body may be hauled from the accident scene. but
- You can't fuck up at a roundabout and get away without at least some property damage, but chances are you will live to report that to your insurance

Very true.

Maybe yes, maybe no. Roundabout under my window had 0 fatalities in 10 years before being built, and 1 - or may be 2 - in 10 years since built.

I'm just saying, that is indeed the reasoning. The "few" crashes that would potentially occur, would be relatively low impact. Just seems that, there weren't many fatal crashes at most signals before anyway. And roundabouts are by no means immune for fatalities.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 17, 2018, 08:52:35 PM
The main selling point is different, though
- You can fuck up at a signal and get away unscathed, or your dead body may be hauled from the accident scene. but
- You can't fuck up at a roundabout and get away without at least some property damage, but chances are you will live to report that to your insurance

Depends on your definition of fuck up. Is fucking up using the incorrect lane or is it attempting to go straight thru the central island? Can "near misses" be classified as fuck ups? Based on those definitions, I'd say it is possible to fuck up at a roundabout and get out unscathed.

(Didn't see this)

Fucking up, in my context, was not being aware of one's surroundings while approaching a junction. If you don't take evasive maneuvers when approaching a roundabout, it's nearly impossible to avoid hitting the central island. Even if you walk away without injuries, there's a good chance you car will have sustained a least a few scuffs. Or you could hit one of those statues like they have in Europe, and be guaranteed a collision. With a signal, you could (theoretically) pass through the junction, just like you would any unsigned/unsignalized junction, without hitting anything or anyone.

We should really consider dropping the "low speed" requirement for "modern roundabouts".

I can almost guarantee that will never happen. There is a direct relationship between speed and amount of injury. Lower speeds and traffic "calming" have been high on the list of benefits of modern roundabouts since the beginning. Raise the speeds and your pretty-damn close to the rotaries that many are trying get rid of.

Overall, there's still a huge educational gap with roundabouts, especially multilane versions. FYAs aren't much different in that regard, but are arguably more intuitive to the new user. Consider this: there are 19 states that do not require formal driver education, according to the Washington State Legislature (http://leg.wa.gov/JTC/Documents/Studies/Driver%20Education_Beth/SummaryStateTable.pdf). We have new drivers in 19 states largely basing their driving habits on their parents or guardians and what they see in GTA. Even in the states that do require formal driver education, roundabouts still aren't necessarily part of their DE's manuals.

How solid is the evidence that rotaries are more dangerous than modern roundabouts? I keep seeing this comparison, between rotaries of yore and modern roundabouts, but the biggest issue with so many of those was the lack of [good] lane markings, poor signage, weaving, and uneven yielding (sometimes yielding in circle, usually not). Besides, even the largest rotaries (like the one in Revere, Mass) only allow maybe 55 mph (speeds could be reduced there by signalizing it). And that's at the top end. One of the better rotary-turned-roundabout's is certainly Latham Circle, in NY. Great markings certainly make it operate much more safely than before, even though it's still quite large.

Perhaps more importantly, how many rotary crashes are/were related to speed?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 18, 2018, 11:37:15 AM
Perhaps more importantly, how many rotary crashes are/were related to speed?
Any flipped truck within roundabout is a combination of uneven surface and speed - albeit possibly very low - being too high.
Title: Re: Crash prone 'modern roundabouts'
Post by: ET21 on August 20, 2018, 10:48:59 AM
What is known as the Suicide Circle, this roundabout is currently undergoing a big face-lift. I drive through it everyday now since I moved and this project is pretty expansive. It involves completely redoing the roundabout to more safer standards, turning a local business street (Broadway) into a boulevard, and redoing the intersection of Broadway street with Northwest Highway (US-14) to the south.

OG roads before construction: https://www.google.com/maps/@42.0527219,-87.9097305,376m/data=!3m1!1e3 (https://www.google.com/maps/@42.0527219,-87.9097305,376m/data=!3m1!1e3)

Plan for the circle (Before and after): http://hbmengineering.com/blog/transportation-design/cumberland-circle-roundabout/ (http://hbmengineering.com/blog/transportation-design/cumberland-circle-roundabout/)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 20, 2018, 11:51:09 AM
What is known as the Suicide Circle, this roundabout is currently undergoing a big face-lift. I drive through it everyday now since I moved and this project is pretty expansive. It involves completely redoing the roundabout to more safer standards, turning a local business street (State) into a boulevard, and redoing the intersection of State street with Northwest Highway (US-14) to the south.

OG roads before construction: https://www.google.com/maps/@42.0527219,-87.9097305,376m/data=!3m1!1e3 (https://www.google.com/maps/@42.0527219,-87.9097305,376m/data=!3m1!1e3)

Plan for the circle (Before and after): http://hbmengineering.com/blog/transportation-design/cumberland-circle-roundabout/ (http://hbmengineering.com/blog/transportation-design/cumberland-circle-roundabout/)
I suspect when you have a five-way busy spot, you only choose between bad and worse..
An interesting thing, though is that northbound N. Wolf to southbound north Broadway used to have a separate slip lane, but no such lane and only high angle turn in a new design.. If traffic along that movement warranted extra lane, it may become a hot spot.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 20, 2018, 01:33:29 PM
According to the article below there have been 421 accidents at the Cumberland Circle between 2005 and 2011, with 10% of them involving injury.  So the circle has averaged about 60 total crashes and 6 injury crashes per year. 

Cumberland Circle reconstruction in Des Plaines beginning soon
https://www.dailyherald.com/news/20180330/cumberland-circle-reconstruction-in-des-plaines-beginning-soon

It will be interesting to see if the new roundabout design will help reduce the total number of crashes at the circle.  One of the biggest changes to the operation is that the circle will go from stop controlled at all legs to yield-control.   In addition, it appears the central island will have a larger diameter with the addition of the truck apron.  Will the larger diameter of the circle be beneficial or not?  I know some people on this thread have suggested that modern roundabouts should be stop controlled and that the circle itself should be largely void of pavement markings so that the drivers regulate themselves through the circle.  This is largely what you see at the Cumberland Circle yet it appears to have a significant number of crashes each year. 

I'm of the mindset that it doesn't seem to matter what design is tried at these multi-lane circles... big vs. small... pavement markings vs. no markings... stop controlled vs. yield controlled... drivers just seem to have trouble negotiating through these multi-lane circles without crashing into each other.  One of the biggest reasons i feel this way is because i have yet to find a 2x2 multi-lane roundabout in America that has a crash rate below 1.0 MEV (which is still higher than the average crash rate of a signalized intersection).  There are plenty of different multi-lane roundabout designs out there, yet the best performing multi-lane roundabouts in this country still have higher crash rates than just an average signalized intersection.  Then you have multi-lane roundabouts like the ones along 116th in Carmel that have crash rates 20x higher than a typical signalized intersection.    Multi-lane roundabouts just seem to equate to lots of crashes,  no matter what is tried.
Title: Re: Crash prone 'modern roundabouts'
Post by: ET21 on August 20, 2018, 02:58:09 PM
The larger apron could be a result of the increased truck and bus usage on this circle. Dayton Freight Lines has a terminal just on the other side of Northwest Highway and Pace's north suburban garage is right down from the circle on Northwest Highway. Large semis tended to have to use both lanes to navigate the original circle. Plus the circle is one of two ways to access Golf Road, a busy east-west roadway.

I never had issues with the circle before construction began as I already knew how to use roundabouts as I always have to use one going over to a friends house in Sugar Grove on Dugan Road. But I can definitely say that drivers do not know how to use this circle. They'd dart last minute from the left lane to their exit which could either cause or almost cause accidents. They never understood to just make the circle again to come back around.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 20, 2018, 03:55:54 PM
The larger apron could be a result of the increased truck and bus usage on this circle. Dayton Freight Lines has a terminal just on the other side of Northwest Highway and Pace's north suburban garage is right down from the circle on Northwest Highway. Large semis tended to have to use both lanes to navigate the original circle. Plus the circle is one of two ways to access Golf Road, a busy east-west roadway.

I never had issues with the circle before construction began as I already knew how to use roundabouts as I always have to use one going over to a friends house in Sugar Grove on Dugan Road. But I can definitely say that drivers do not know how to use this circle. They'd dart last minute from the left lane to their exit which could either cause or almost cause accidents. They never understood to just make the circle again to come back around.
Are you sure you actually understand roundabout operation if you complain about traffic exiting from left lane?
Title: Re: Crash prone 'modern roundabouts'
Post by: ET21 on August 20, 2018, 04:41:52 PM
The larger apron could be a result of the increased truck and bus usage on this circle. Dayton Freight Lines has a terminal just on the other side of Northwest Highway and Pace's north suburban garage is right down from the circle on Northwest Highway. Large semis tended to have to use both lanes to navigate the original circle. Plus the circle is one of two ways to access Golf Road, a busy east-west roadway.

I never had issues with the circle before construction began as I already knew how to use roundabouts as I always have to use one going over to a friends house in Sugar Grove on Dugan Road. But I can definitely say that drivers do not know how to use this circle. They'd dart last minute from the left lane to their exit which could either cause or almost cause accidents. They never understood to just make the circle again to come back around.
Are you sure you actually understand roundabout operation if you complain about traffic exiting from left lane?

I'm not complaining.... I'm just stating what I see when I enter it and it is one of the main causes of accidents with it
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 20, 2018, 04:47:43 PM
The larger apron could be a result of the increased truck and bus usage on this circle. Dayton Freight Lines has a terminal just on the other side of Northwest Highway and Pace's north suburban garage is right down from the circle on Northwest Highway. Large semis tended to have to use both lanes to navigate the original circle. Plus the circle is one of two ways to access Golf Road, a busy east-west roadway.

I never had issues with the circle before construction began as I already knew how to use roundabouts as I always have to use one going over to a friends house in Sugar Grove on Dugan Road. But I can definitely say that drivers do not know how to use this circle. They'd dart last minute from the left lane to their exit which could either cause or almost cause accidents. They never understood to just make the circle again to come back around.
Are you sure you actually understand roundabout operation if you complain about traffic exiting from left lane?

I'm not complaining.... I'm just stating what I see when I enter it and it is one of the main causes of accidents with it

What I am specifically referring to is this phrase
But I can definitely say that drivers do not know how to use this circle. They'd dart last minute from the left lane to their exit which could either cause or almost cause accidents. They never understood to just make the circle again to come back around.
From the look at the map, it is pretty obvious that exiting  from left lane is a standard way of using this circle, look at traces from 5o'clock to 12 o'clock position on the image below. Many roundabouts are actually designed that way; new design renderings show just that as well.
(https://www.dailyherald.com/storyimage/DA/20180330/NEWS/180339898/AR/0/AR-180339898.jpg)

So my question still stands - why do you think you  know how to use this circle?
Title: Re: Crash prone 'modern roundabouts'
Post by: ET21 on August 21, 2018, 08:48:36 AM
Because I haven't been involved in such an accident after witnessing a few happen right in front of me due to this very movement. It's not rocket science to use a roundabout, but unfortunately it is to many motorists I encounter on my daily commute.

If you're assuming I'm full of shit why would I lie about something as trivial as knowledge of roundabout movements on an internet forum  :hmmm: 
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 21, 2018, 09:24:46 AM
Because I haven't been involved in such an accident after witnessing a few happen right in front of me due to this very movement. It's not rocket science to use a roundabout, but unfortunately it is to many motorists I encounter on my daily commute.

If you're assuming I'm full of shit why would I lie about something as trivial as knowledge of roundabout movements on an internet forum  :hmmm: 

It's pretty clear you do not understand how a roundabout works.

Once you've entered a roundabout, you're not supposed to change lanes.  Signage prior to the roundabout is supposed to inform you which lane you're in for the exit you want.  In many cases, on 2 lane roundabouts, the left lane entering the roundabout places you on the inside of the roundabout, but will guide you out of the roundabout at the appropriate time. 

For roundabouts such as the one pictured, it's not really a modern roundabout, but rather a traffic circle.  And honestly, they tend to have their own rules that aren't going to be found in any rulebook.  For those, you just do what the Romans do, rather than trying to inflict your opinion of how the circle should operate on everyone else.
Title: Re: Crash prone 'modern roundabouts'
Post by: ET21 on August 21, 2018, 09:38:13 AM
Because I haven't been involved in such an accident after witnessing a few happen right in front of me due to this very movement. It's not rocket science to use a roundabout, but unfortunately it is to many motorists I encounter on my daily commute.

If you're assuming I'm full of shit why would I lie about something as trivial as knowledge of roundabout movements on an internet forum  :hmmm: 

It's pretty clear you do not understand how a roundabout works.

Once you've entered a roundabout, you're not supposed to change lanes.  Signage prior to the roundabout is supposed to inform you which lane you're in for the exit you want.  In many cases, on 2 lane roundabouts, the left lane entering the roundabout places you on the inside of the roundabout, but will guide you out of the roundabout at the appropriate time. 

For roundabouts such as the one pictured, it's not really a modern roundabout, but rather a traffic circle.  And honestly, they tend to have their own rules that aren't going to be found in any rulebook.  For those, you just do what the Romans do, rather than trying to inflict your opinion of how the circle should operate on everyone else.

Thank you for clearing that up  :cool: I always just treated it as a roundabout, but your explanation makes sense. Long story short, hope this construction project will improve the flow 
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 21, 2018, 10:18:53 AM
Because I haven't been involved in such an accident after witnessing a few happen right in front of me due to this very movement. It's not rocket science to use a roundabout, but unfortunately it is to many motorists I encounter on my daily commute.

If you're assuming I'm full of shit why would I lie about something as trivial as knowledge of roundabout movements on an internet forum  :hmmm:
Why, there is no lies. I am treating this as an honest mistake on your side. Fact that you didn't get into an accident doesn't tell you know the drill - it may also be your luck and skill of people around you..
But back to technical matters:
Exit from inner lanes is an essencial design feature of roundabouts.
Old facioned circles can be different, though. Still the circle we're talking about, while not a "modern roundabout", but it is clearly setup to allow exit from left lane on 2 out of 5 legs.
A such, I would take your complain for "exit from no-exit lane", or "exit from left lane where that is not allowed" - but a plain "exit from left lane", combined with confusion between traffic circle and roundabout (later is a special case of a circle in common terminology) raises some red flags.
I never had issues with the circle before construction began as I already knew how to use roundabouts as I always have to use one going over to a friends house in Sugar Grove on Dugan Road. But I can definitely say that drivers do not know how to use this circle. They'd dart last minute from the left lane to their exit which could either cause or almost cause accidents. They never understood to just make the circle again to come back around.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 21, 2018, 11:42:33 AM
Because I haven't been involved in such an accident after witnessing a few happen right in front of me due to this very movement. It's not rocket science to use a roundabout, but unfortunately it is to many motorists I encounter on my daily commute.

If you're assuming I'm full of shit why would I lie about something as trivial as knowledge of roundabout movements on an internet forum  :hmmm: 

It's pretty clear you do not understand how a roundabout works.

Once you've entered a roundabout, you're not supposed to change lanes.  Signage prior to the roundabout is supposed to inform you which lane you're in for the exit you want.  In many cases, on 2 lane roundabouts, the left lane entering the roundabout places you on the inside of the roundabout, but will guide you out of the roundabout at the appropriate time. 

For roundabouts such as the one pictured, it's not really a modern roundabout, but rather a traffic circle.  And honestly, they tend to have their own rules that aren't going to be found in any rulebook.  For those, you just do what the Romans do, rather than trying to inflict your opinion of how the circle should operate on everyone else.

The old circle seems to be primarily driven between N. Wolf and Golf roads, and pavement marks - both white lines and tire wear lines - show that inner lane exits at those arm. Poor souls trying to take a different trajectory.. Indeed they have a choice of either suddenly exiting from left lane, or having their path crossed by someone exiting from inner lane (as designed). No surprise about nickname!
What is known as the Suicide Circle,
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 31, 2018, 10:21:16 AM
This newly built Walker roundabout has been a problem from day one.  Traffic backing up onto the freeway worse than before the roundabout was built has been reported by the Walker Police.  And according to the police there has been an average of 1 crash every 1.7 days since the roundabout opened.

See Walker's new I-12 roundabout in action; residents, police call it 'confusing'
https://www.theadvocate.com/baton_rouge/news/communities/livingston_tangipahoa/article_6d52d828-d611-11e7-9582-8f8dcc4fe95f.html

IT'S A TRAP | Walker roundabouts recording an accident once every two days

https://www.livingstonparishnews.com/news/it-s-a-trap-walker-roundabouts-recording-an-accident-once/article_9d856868-ac70-11e8-a38d-a7be895c7bfd.html

Looking at the aerial of the roundabout there are significant problems with the lane markings.  If they can't get simple pavement markings right my confidence of this roundabout design is low. 
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBWalker_zpssewoa8qo.png)


   
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 31, 2018, 10:30:21 AM
This newly built Walker roundabout has been a problem from day one.  Traffic backing up onto the freeway worse than before the roundabout was built has been reported by the Walker Police.  And according to the police there has been an average of 1 crash every 1.7 days since the roundabout opened.

See Walker's new I-12 roundabout in action; residents, police call it 'confusing'
https://www.theadvocate.com/baton_rouge/news/communities/livingston_tangipahoa/article_6d52d828-d611-11e7-9582-8f8dcc4fe95f.html

IT'S A TRAP | Walker roundabouts recording an accident once every two days

https://www.livingstonparishnews.com/news/it-s-a-trap-walker-roundabouts-recording-an-accident-once/article_9d856868-ac70-11e8-a38d-a7be895c7bfd.html

Looking at the aerial of the roundabout there are significant problems with the lane markings.  If they can't get simple pavement markings right my confidence of this roundabout design is low. 
 
Well, the top image in a first link shows something that looks like a roadwork on one of erroneous arrows. Maybe they will paint in over?....
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 31, 2018, 10:46:38 AM
This newly built Walker roundabout has been a problem from day one.  Traffic backing up onto the freeway worse than before the roundabout was built has been reported by the Walker Police.  And according to the police there has been an average of 1 crash every 1.7 days since the roundabout opened.

See Walker's new I-12 roundabout in action; residents, police call it 'confusing'
https://www.theadvocate.com/baton_rouge/news/communities/livingston_tangipahoa/article_6d52d828-d611-11e7-9582-8f8dcc4fe95f.html

IT'S A TRAP | Walker roundabouts recording an accident once every two days

https://www.livingstonparishnews.com/news/it-s-a-trap-walker-roundabouts-recording-an-accident-once/article_9d856868-ac70-11e8-a38d-a7be895c7bfd.html

Looking at the aerial of the roundabout there are significant problems with the lane markings.  If they can't get simple pavement markings right my confidence of this roundabout design is low. 
(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBWalker_zpssewoa8qo.png)

In this case, it's just a bad design all the way around.  Bad design, bad land markings, bad striping. Coming from the south, the lane marking show that you should use the left land going into the roundabout to make a left turn.  Except, there's no reason to make a left turn.  Most roundabouts aren't signed to show how to make a U-turn, which would be the only reason one would turn left in the roundabout from the south in this case.  In fact, there doesn't seem to be much need for a roundabout design at all, because the top loop doesn't serve any purpose expect to make that U-turn, which doesn't appear to be necessary.

The newspaper story's excuse that traffic will be better once the other roundabout is open doesn't seem very factual either, because there's no congestion going across the bridge.

Since this story was from 2017, I'd think the other roundabout has been opened by now.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 31, 2018, 10:52:35 AM
The satellite imagery probably shows a point in time where the right lane was not open, so the left lane was painted to indicate that continuing back onto the freeway, as well as turning left, was permitted from that lane (whereas, in normal operation, only a left turn should be permitted, since that's supposed to be a double left).

That all said, the "path overlap" appears to be a pretty serious issue. Perhaps reducing the left turns to one lane instead of two would be better. Ultimately, the engineers should have aligned that off-ramp better. Or, they should have moved the roundabouts closer to the bridge, allowing the off-ramps to point straight at the roundabout, instead of coming in at an angle.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 05, 2018, 02:47:56 PM
Minnesota truck drivers reveal their thoughts about the notorious roundabouts in Worthington, which has been the site of at least four confirmed truck tip-overs over the past year (all of which have been documented in this thread).  It just doesn't seem roundabout designers consider all the factors that truck drivers must deal with:

Risky roundabouts? Area truck drivers share thoughts about circular junctions
https://www.dglobe.com/news/traffic-and-construction/4494568-risky-roundabouts-area-truck-drivers-share-thoughts-about
Quote
“You’re top heavy, so you hit that impact curb and it tips the truck,”  Schutte said.

Add in heavy winds, and these combined factors could easily cause the trailer to roll over, said Gary Abels, a Brewster semi driver and owner of Abels Transport. In addition to tipping, the truck apron can cause hang-up issues if the trailer has low ground clearance.

“My trailer is only four inches off the ground when it’s heavy, so then I have to avoid the apron,”  Abels said.

On one occasion, Abels was forced to avoid Worthington roundabouts entirely. Delivering a planter to Worthington Ag Parts, he was not allowed to travel through the roundabout due to an oversized load, per state law.

“That’s another issue,”  Abels said. “Trucks with oversized trailers can make normal turns, but they can’t go through roundabouts, so how are we supposed to get into town if they build even more roundabouts?”
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on September 05, 2018, 03:28:19 PM
This roundabout in Trenton, NJ has a flat apron. https://goo.gl/maps/9AcB1PdPNa12  The result is that many people drive straight across it rather than properly go around it.

A long-time issue with truckers at normal intersections is they can't make the turn without cutting out into a same-direction lane or opposing lane of traffic.  Accidents have resulted with this as well. 

Oversized trailers must receive a permit and routing information prior to travel, so any issues with obstructions, including undersized height bridges, weight restricted bridges, and other obstacles, like roundabouts, are taken into account with the routing.  If these truckers are in areas where bridges aren't an issue, they're lucky.  Truckers in the NYC area will laugh at their issue with a little roundabout when they're dealing nonstop with the obstructions they face everyday.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 05, 2018, 04:34:02 PM
This roundabout in Trenton, NJ has a flat apron. https://goo.gl/maps/9AcB1PdPNa12  The result is that many people drive straight across it rather than properly go around it.

A long-time issue with truckers at normal intersections is they can't make the turn without cutting out into a same-direction lane or opposing lane of traffic.  Accidents have resulted with this as well. 

Oversized trailers must receive a permit and routing information prior to travel, so any issues with obstructions, including undersized height bridges, weight restricted bridges, and other obstacles, like roundabouts, are taken into account with the routing.  If these truckers are in areas where bridges aren't an issue, they're lucky.  Truckers in the NYC area will laugh at their issue with a little roundabout when they're dealing nonstop with the obstructions they face everyday.
After all it is about roundabouts niche.
They are not for truck-heavy roads, that's what you're saying. That actually came up a few times upstream - roundabouts good for cars, not for something bigger.
Fine with me.  That would quickly exclude any moderately busy road  - US/state fall out automatically, as well as anything close to freeway exits. Two lane to two lane at most...
If that is the limitation to be imposed on any roundabout construction - I think there is no need to ban them through act of Congress..
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 14, 2018, 03:05:19 PM
Van FLIES over roundabout in shocking video - three injured as police launch probe
https://www.express.co.uk/news/uk/1017199/norfolk-news-attleborough-a11-van-roundabout-video-norfolk-police

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 14, 2018, 03:23:14 PM
Van FLIES over roundabout in shocking video - three injured as police launch probe
https://www.express.co.uk/news/uk/1017199/norfolk-news-attleborough-a11-van-roundabout-video-norfolk-police

This is what happens when stupid american drivers try to drive in UK! [ /irony]
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on September 17, 2018, 03:58:19 PM


Van FLIES over roundabout in shocking video - three injured as police launch probe

He was clearly driving at a safe and proper speed when the roundabout came out of nowhere and attacked him.

Pixel 2

Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on September 17, 2018, 05:40:58 PM
Happy national Roundabout week!  best intersection type around!  :clap:
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 17, 2018, 09:10:53 PM
Happy national Roundabout week!  best intersection type around!  :clap:
Why do you care? You should be taking a bus, or even better a train - the best transportation mode around!
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 02, 2018, 11:58:05 AM
The Pennsylvania Department of Transportation reviewed data for 11 roundabouts on state routes at intersections that were previously stop or signal controlled.  The results looked very good:

-   Fatalities were reduced by 100 percent (from two to zero);
-   Serious injuries were reduced by 100 percent (from seven to zero);
-   Minor injuries were reduced by 95 percent (from 19 to one);
-   Possible/unknown severity injuries were reduced by 92 percent (from 49 to four);
-   Crashes causing only property damage decreased by 2 percent (from 49 to 48); and
-   The total number of crashes dropped 47 percent (from 101 to 54).

PennDOT Data Shows Pennsylvania Roundabouts Reducing Crashes, Injuries and Fatalities
https://www.penndot.gov/pages/all-news-details.aspx?newsid=536[/quote]

The problem with the study is of the 11 roundabouts analyzed, all were simple single-lane roundabouts.  The fact is Pennsylvania hasn’t built many multi-lane roundabouts.  I just hope the state doesn’t fool themselves into thinking “multi-lane”  roundabouts will see similar crash reductions based on the results of 11 single-lane roundabouts.  The state just recently constructed one of the first multi-lane roundabout in Pennsylvania on State 222 and… surprise, surprise… it’s seeing a lot more crashes than they expected.  Of course, the State 222 multi-lane roundabout wasn’t included in their study since it just opened this year.  But based on the great results of the “single-lane”  roundabout study, officials have downplayed the increases in crashes on State 222, stating that “accidents will wane as people learn to navigate the new circle” .  I just feel like we have been here before… Pennsylvania should look closely at states like Michigan and Wisconsin if they want to see how large complex multi-lane roundabouts fair.  Here is a statement from PennDOT Secretary Leslie S. Richards:

"Our data shows that modern-day roundabouts reduce crash severity and injuries while improving traffic flow,"

No Leslie, your data shows that single-lane modern-day roundabouts reduce crash severity and injuries while improving traffic flow. It tells us nothing about how multi-lane roundabouts will perform in your state. PennDOT, don't start building complex multi-lane roundabouts willy-nilly based on the results of your little "single-lane" roundabout study. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on October 02, 2018, 12:15:32 PM
Pennsylvanians only drive in the left lane anyway.  It could be a 10 lane roundabout and they'll all be stacked in the left lane!

 :-D :-D :-D
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 02, 2018, 12:46:24 PM
The Pennsylvania Department of Transportation reviewed data for 11 roundabouts on state routes at intersections that were previously stop or signal controlled.  The results looked very good:

-   Fatalities were reduced by 100 percent (from two to zero);
-   Serious injuries were reduced by 100 percent (from seven to zero);
-   Minor injuries were reduced by 95 percent (from 19 to one);
-   Possible/unknown severity injuries were reduced by 92 percent (from 49 to four);
-   Crashes causing only property damage decreased by 2 percent (from 49 to 48); and
-   The total number of crashes dropped 47 percent (from 101 to 54).

PennDOT Data Shows Pennsylvania Roundabouts Reducing Crashes, Injuries and Fatalities
https://www.penndot.gov/pages/all-news-details.aspx?newsid=536

The problem with the study is of the 11 roundabouts analyzed, all were simple single-lane roundabouts.  The fact is Pennsylvania hasn’t built many multi-lane roundabouts.  I just hope the state doesn’t fool themselves into thinking “multi-lane”  roundabouts will see similar crash reductions based on the results of 11 single-lane roundabouts.  The state just recently constructed one of the first multi-lane roundabout in Pennsylvania on State 222 and… surprise, surprise… it’s seeing a lot more crashes than they expected.  Of course, the State 222 multi-lane roundabout wasn’t included in their study since it just opened this year.  But based on the great results of the “single-lane”  roundabout study, officials have downplayed the increases in crashes on State 222, stating that “accidents will wane as people learn to navigate the new circle” .  I just feel like we have been here before… Pennsylvania should look closely at states like Michigan and Wisconsin if they want to see how large complex multi-lane roundabouts fair.  Here is a statement from PennDOT Secretary Leslie S. Richards:

"Our data shows that modern-day roundabouts reduce crash severity and injuries while improving traffic flow,"

No Leslie, your data shows that single-lane modern-day roundabouts reduce crash severity and injuries while improving traffic flow. It tells us nothing about how multi-lane roundabouts will perform in your state. PennDOT, don't start building complex multi-lane roundabouts willy-nilly based on the results of your little "single-lane" roundabout study. 

Once again, in defence of the agency, how many other traffic control devices have remarkable safety records when only being one lane each direction, but totally fall apart when adding a second lane in each direction? Virtually all types of traffic control work regardless of the number of lanes (though four-way stops with a lot of lanes can break down pretty quickly). Generally, the deciding factor in safety is the overall control: stop, yield, signal etc. Geometry also plays a role, but I guess it's not entirely obvious that the geometry of a multi lane roundabout really screws things up.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 02, 2018, 01:12:47 PM
Time and time again the crash rates of multi-lane roundabouts (specifically 2x2 multi-lane roundabouts) are abnormally high.  You start to wonder if multi-lane roundabouts are the best choice when they have average crash rates of 4.0 MEV compared to a typical signalized intersection which only averages about 0.8 MEV.  Like i have said, when you have 4x more crashes at a roundabout there's no guarantee there is going to be a drop in injury crashes.  All i know is for the next decade we will hear how safe roundabouts are in Pennsylvania based on PennDot's "single-lane roundabout study"... even when they are proposing to build a complex 3x2 monstrosity.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 02, 2018, 02:36:16 PM
Back to the party a little late.....




Here's an aerial of the Van Dyke and 18 1/2 Mile with a proposed redesign. 

(https://i.imgur.com/WZGr4OQ.jpg)

Having a straight shot exiting the roundabout could simplify the roundabout operation IMO.  Drivers circulating the roundabout who drive over a "straight only" arrow pavement marking would actually continue to drive "straight" as oppose to weave through the roundabout.  The green path in the picture is simply easier to drive than the blue path.   Notice that the blue path hugs the inside of the roundabout for much longer than the green path, so a driver who wishes to enter the roundabout doesn't know the circulating drivers intention till much later on.  With the blue path it's a guessing game if the vehicle is about to exit the roundabout or continue circulating through it.  Makes it much more likely a driver pulls out infront of someone because they "guessed" wrong.

Ten or twenty years ago, I was seeing design guides out there on the internet saying the approach to a roundabout should be curved (to "force" slowing) but the departure should be straight.  And that's exactly what you have pictured.  But I believe the change in mindset is as was mentioned earlier:  a straight-shot departure means more trouble for pedestrians crossing nearby.



A single fatal crash is a significant event.  According to published data, signalized intersections in America average a fatal crash about every 100 years and drivers have only been driving through modern roundabouts in this country for 27 years.    Considering there have been 2 fatal crashes at Summerlin Nevada roundabouts over the past several months - the first community in America to build modern roundabouts — they instantly become fatality prone intersections.

If Wichita Falls, TX (a city with approximately the same population as Summerlin), were to have 2 fatal crashes at signalized intersections over the past several months, then would those instantly become fatality-prone intersections in your estimation?  If not, then you're applying a double standard.



Because I haven't been involved in such an accident after witnessing a few happen right in front of me due to this very movement. It's not rocket science to use a roundabout, but unfortunately it is to many motorists I encounter on my daily commute.

If you're assuming I'm full of shit why would I lie about something as trivial as knowledge of roundabout movements on an internet forum  :hmmm:
Why, there is no lies. I am treating this as an honest mistake on your side. Fact that you didn't get into an accident doesn't tell you know the drill - it may also be your luck and skill of people around you..
But back to technical matters:
Exit from inner lanes is an essencial design feature of roundabouts.
Old facioned circles can be different, though. Still the circle we're talking about, while not a "modern roundabout", but it is clearly setup to allow exit from left lane on 2 out of 5 legs.
A such, I would take your complain for "exit from no-exit lane", or "exit from left lane where that is not allowed" - but a plain "exit from left lane", combined with confusion between traffic circle and roundabout (later is a special case of a circle in common terminology) raises some red flags.

Indeed, if traffic were not allowed to exit from the inner lane of a roundabout, then why would there even be an inner lane?  If nobody were allowed to exit from it, then any driver foolish enough to end up there would just have to drive round and round in circles all day.



Minnesota truck drivers reveal their thoughts about the notorious roundabouts in Worthington, which has been the site of at least four confirmed truck tip-overs over the past year (all of which have been documented in this thread).  It just doesn't seem roundabout designers consider all the factors that truck drivers must deal with:

Risky roundabouts? Area truck drivers share thoughts about circular junctions
https://www.dglobe.com/news/traffic-and-construction/4494568-risky-roundabouts-area-truck-drivers-share-thoughts-about
Quote
“You’re top heavy, so you hit that impact curb and it tips the truck,”  Schutte said.

Add in heavy winds, and these combined factors could easily cause the trailer to roll over, said Gary Abels, a Brewster semi driver and owner of Abels Transport. In addition to tipping, the truck apron can cause hang-up issues if the trailer has low ground clearance.

“My trailer is only four inches off the ground when it’s heavy, so then I have to avoid the apron,”  Abels said.

On one occasion, Abels was forced to avoid Worthington roundabouts entirely. Delivering a planter to Worthington Ag Parts, he was not allowed to travel through the roundabout due to an oversized load, per state law.

“That’s another issue,”  Abels said. “Trucks with oversized trailers can make normal turns, but they can’t go through roundabouts, so how are we supposed to get into town if they build even more roundabouts?”

Worthington is in the middle of huge agriculture.  When I was up there about a year ago, it was unbelievable how many trains and trucks were being filled up with corn and soybeans.  Heavy-laden trucks with inexperienced drivers behind the wheel is, frankly, the reality of life in farm country.  I know this because I grew up in farm country.  The Worthington roundabouts are also right on the primary route from the Twin Cities to Sioux City and the #2 route from the Twin Cities to Omaha.  Failing to account for heavy and/or oversize truck loads on that corridor is inexcusable.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 02, 2018, 09:57:29 PM
A single fatal crash is a significant event.  According to published data, signalized intersections in America average a fatal crash about every 100 years and drivers have only been driving through modern roundabouts in this country for 27 years.    Considering there have been 2 fatal crashes at Summerlin Nevada roundabouts over the past several months - the first community in America to build modern roundabouts — they instantly become fatality prone intersections.

If Wichita Falls, TX (a city with approximately the same population as Summerlin), were to have 2 fatal crashes at signalized intersections over the past several months, then would those instantly become fatality-prone intersections in your estimation?  If not, then you're applying a double standard.

I think any intersection with fatalities is fatality-prone, at least retrospectively. His argument isn't that signals are safer. It's that multi-lane roundabouts aren't necessarily better.
Title: Re: Crash prone 'modern roundabouts'
Post by: ScottRAB on October 04, 2018, 04:12:58 PM
Total crashes at any intersection, regardless of traffic control, are not particularly relevant. 

People using the road make mistakes (like running stop signs and red lights), always have and always will. Crashes will always be with us, but they need not result in fatalities or serious injury.

Modern roundabouts are the safest form of intersection in the world - the intersection type with the lowest risk of fatal or serious injury crashes - (much more so than comparable signals).  Modern roundabouts require a change in speed and alter the geometry of one of the most dangerous parts of the system - intersections. 

The reduction in speed to about 20 mph and sideswipe geometry mean that, when a crash does happen at a modern roundabout, you usually need a tow truck, not an ambulance.  Visit the Insurance Institute for Highway Safety for modern roundabout FAQs and safety facts.  Roundabouts are one of several proven road safety features (FHWA). 
The life saved may be your own.
https://safety.fhwa.dot.gov/provencountermeasures/roundabouts/
https://safety.fhwa.dot.gov/intersection/innovative/roundabouts/
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 04, 2018, 04:27:07 PM
^^
You should probably read the thread. Tradephoric and the rest of us have very carefully dissected the data behind roundabouts; it's not that cut and dry.

Consider this: the only thing forcing a driver to turn left or right is the steering wheel, not the geography surrounding the car.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 04, 2018, 04:43:08 PM
The reduction in speed to about 20 mph and sideswipe geometry mean that, when a crash does happen at a modern roundabout, you usually need a tow truck, not an ambulance.  Visit the Insurance Institute for Highway Safety for modern roundabout FAQs and safety facts. 

These "20 mph" roundabout crashes look so safe... 




Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 04, 2018, 05:46:44 PM

Hey, this one's cheating. The roundabout is still another 5 metres away.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 04, 2018, 09:39:14 PM
I'm not sure if it's been mentioned or not, but in Carmel, the 116th/Hazel Dell Pkwy signal has been reconfigured (https://goo.gl/G7jYLv) into this behemoth. We have a solid object in the middle, just in case someone forgets to turn their wheel on approach, and a third lane going southbound, for no obvious reason (2 lanes before and after, and northbound is only two lanes).

A simpler design with a flat center (with some bushes) might be prove safer long term, if tradephoric's data is to be believed.

The double right turn yield is pretty cool, though!

(https://www.dronegenuity.com/wp-content/uploads/2018/03/carmel-IN-roundabout-10.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 04, 2018, 09:57:24 PM

Hey, this one's cheating. The roundabout is still another 5 metres away.
I would include approach geometry into roundabout statistics.
Same as rear ends (e.g. at red light cameras) are assigned to an intersection while they are still way outside the intersection box.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 04, 2018, 10:54:58 PM
https://www.youtube.com/watch?v=dYtmnzwJ4Cw

Hey, this one's cheating. The roundabout is still another 5 metres away.

I would include approach geometry into roundabout statistics.
Same as rear ends (e.g. at red light cameras) are assigned to an intersection while they are still way outside the intersection box.

Actually, I agree. I was being sarcastic but forgot to include the obligatory "/s".
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 05, 2018, 12:55:22 PM
A single fatal crash is a significant event.  According to published data, signalized intersections in America average a fatal crash about every 100 years and drivers have only been driving through modern roundabouts in this country for 27 years.    Considering there have been 2 fatal crashes at Summerlin Nevada roundabouts over the past several months - the first community in America to build modern roundabouts — they instantly become fatality prone intersections.

If Wichita Falls, TX (a city with approximately the same population as Summerlin), were to have 2 fatal crashes at signalized intersections over the past several months, then would those instantly become fatality-prone intersections in your estimation?  If not, then you're applying a double standard.

I think any intersection with fatalities is fatality-prone, at least retrospectively. His argument isn't that signals are safer. It's that multi-lane roundabouts aren't necessarily better.

I drove to my parents' house yesterday evening, 7 miles away, and then back again 1½ hours later.  I saw one wreck in each direction; one was at a business entrance crossing, and the other was at a stoplight.  The former was so severe that they were still cleaning up the scene 1½ hours later on my return trip.  So now both that stoplight and that business entrance crossing automatically become "crash prone"?

¼ mile in another direction from my house, there's another stoplight where I've seen two wrecks within a year's span.  Nothing weird about the intersection, just four-lane roads in each direction and a three-section signal.  But it must somehow be "crash prone".
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 05, 2018, 03:03:07 PM
A single fatal crash is a significant event.  According to published data, signalized intersections in America average a fatal crash about every 100 years and drivers have only been driving through modern roundabouts in this country for 27 years.    Considering there have been 2 fatal crashes at Summerlin Nevada roundabouts over the past several months - the first community in America to build modern roundabouts — they instantly become fatality prone intersections.

If Wichita Falls, TX (a city with approximately the same population as Summerlin), were to have 2 fatal crashes at signalized intersections over the past several months, then would those instantly become fatality-prone intersections in your estimation?  If not, then you're applying a double standard.

I think any intersection with fatalities is fatality-prone, at least retrospectively. His argument isn't that signals are safer. It's that multi-lane roundabouts aren't necessarily better.

I drove to my parents' house yesterday evening, 7 miles away, and then back again 1½ hours later.  I saw one wreck in each direction; one was at a business entrance crossing, and the other was at a stoplight.  The former was so severe that they were still cleaning up the scene 1½ hours later on my return trip.  So now both that stoplight and that business entrance crossing automatically become "crash prone"?

¼ mile in another direction from my house, there's another stoplight where I've seen two wrecks within a year's span.  Nothing weird about the intersection, just four-lane roads in each direction and a three-section signal.  But it must somehow be "crash prone".
You may divide any road areas into two groups: ones where fatal accident already occurred and those where it didn' happen yet.
However any serious crash, or repeat crashes, does require investigation of whether it is statistical fluctuation or a road issue. In the ideal world, at least. As a rule of thumb nobody cares until there is a fatality anyway.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 05, 2018, 03:05:41 PM
A single fatal crash is a significant event.  According to published data, signalized intersections in America average a fatal crash about every 100 years and drivers have only been driving through modern roundabouts in this country for 27 years.    Considering there have been 2 fatal crashes at Summerlin Nevada roundabouts over the past several months - the first community in America to build modern roundabouts — they instantly become fatality prone intersections.

If Wichita Falls, TX (a city with approximately the same population as Summerlin), were to have 2 fatal crashes at signalized intersections over the past several months, then would those instantly become fatality-prone intersections in your estimation?  If not, then you're applying a double standard.

I think any intersection with fatalities is fatality-prone, at least retrospectively. His argument isn't that signals are safer. It's that multi-lane roundabouts aren't necessarily better.

I drove to my parents' house yesterday evening, 7 miles away, and then back again 1½ hours later.  I saw one wreck in each direction; one was at a business entrance crossing, and the other was at a stoplight.  The former was so severe that they were still cleaning up the scene 1½ hours later on my return trip.  So now both that stoplight and that business entrance crossing automatically become "crash prone"?

¼ mile in another direction from my house, there's another stoplight where I've seen two wrecks within a year's span.  Nothing weird about the intersection, just four-lane roads in each direction and a three-section signal.  But it must somehow be "crash prone".

Technically, every intersections is "crash prone"; what matters is how crash prone they are. Though, various agencies around the country (and the FHWA) would like you to believe that roundabouts, of any size or variety, are relatively less prone. And that does seem to be true at single-lane roundabouts, but at multi-lane roundabouts, they appear to be far more crash prone.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on October 05, 2018, 03:45:39 PM
A single fatal crash is a significant event.  According to published data, signalized intersections in America average a fatal crash about every 100 years and drivers have only been driving through modern roundabouts in this country for 27 years.    Considering there have been 2 fatal crashes at Summerlin Nevada roundabouts over the past several months - the first community in America to build modern roundabouts – they instantly become fatality prone intersections.

If Wichita Falls, TX (a city with approximately the same population as Summerlin), were to have 2 fatal crashes at signalized intersections over the past several months, then would those instantly become fatality-prone intersections in your estimation?  If not, then you're applying a double standard.

I think any intersection with fatalities is fatality-prone, at least retrospectively. His argument isn't that signals are safer. It's that multi-lane roundabouts aren't necessarily better.

I drove to my parents' house yesterday evening, 7 miles away, and then back again 1½ hours later.  I saw one wreck in each direction; one was at a business entrance crossing, and the other was at a stoplight.  The former was so severe that they were still cleaning up the scene 1½ hours later on my return trip.  So now both that stoplight and that business entrance crossing automatically become "crash prone"?

¼ mile in another direction from my house, there's another stoplight where I've seen two wrecks within a year's span.  Nothing weird about the intersection, just four-lane roads in each direction and a three-section signal.  But it must somehow be "crash prone".

If a tree cutter fell a tree, and it happened to fall the wrong way on a car at an intersection killing someone inside, does that make the intersection crash prone?

Trade's never really been interested in reasoning behind something...he just looks at very basic info.  Fatal at intersection = crash prone.
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on October 05, 2018, 04:04:26 PM
High speed, driver feel asleep, drink driver, truck with no brakes.... What a joke! That's an argument against 'something' but it has f#@$ all to do with roundabouts.

Pixel 2

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 05, 2018, 04:21:27 PM
High speed, driver feel asleep, drink driver, truck with no brakes.... What a joke! That's an argument against 'something' but it has f#@$ all to do with roundabouts.

But they all hit something related to the design of the roundabout. Either a sign leading up to it, or the central island.

Would some of them have eventually crashed? Perhaps, but roundabouts create geographical hazards, which make them hard to navigate if you didn't notice them.

You can run a signal. You can't run a roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on October 05, 2018, 05:02:25 PM
High speed, driver feel asleep, drink driver, truck with no brakes.... What a joke! That's an argument against 'something' but it has f#@$ all to do with roundabouts.

But they all hit something related to the design of the roundabout. Either a sign leading up to it, or the central island.

Would some of them have eventually crashed? Perhaps, but roundabouts create geographical hazards, which make them hard to navigate if you didn't notice them.

You can run a signal. You can't run a roundabout.
Please. A truck with no brakes? When are you guys going to start a "crash prone curves" topic. It won't be the dangerous truck, it'll be the curve that was in its way, a poor design.  This thread has become farce.

Pixel 2
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on October 05, 2018, 05:05:02 PM
High speed, driver feel asleep, drink driver, truck with no brakes.... What a joke! That's an argument against 'something' but it has f#@$ all to do with roundabouts.

But they all hit something related to the design of the roundabout. Either a sign leading up to it, or the central island.

Would some of them have eventually crashed? Perhaps, but roundabouts create geographical hazards, which make them hard to navigate if you didn't notice them.

You can run a signal. You can't run a roundabout.

Based on the opinions of some in this thread, roundabouts need to be made idiot-proof, just because there's a good chance a law-breaker will be able to screw-up at a traffic light and make it through unscathed. What next, do we need to make electric fences that don't shock someone if they decide to pee on it? Lawyers and politicians are killing our society and whatever is left of "common sense".
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 05, 2018, 06:26:07 PM
High speed, driver feel asleep, drink driver, truck with no brakes.... What a joke! That's an argument against 'something' but it has f#@$ all to do with roundabouts.

But they all hit something related to the design of the roundabout. Either a sign leading up to it, or the central island.

Would some of them have eventually crashed? Perhaps, but roundabouts create geographical hazards, which make them hard to navigate if you didn't notice them.

You can run a signal. You can't run a roundabout.

Based on the opinions of some in this thread, roundabouts need to be made idiot-proof, just because there's a good chance a law-breaker will be able to screw-up at a traffic light and make it through unscathed. What next, do we need to make electric fences that don't shock someone if they decide to pee on it? Lawyers and politicians are killing our society and whatever is left of "common sense".

As long as speeding, driving drunk, and inattentiveness aren't punishable by death, we should be trying to design for everyone, even morons. I fucking hate it. I'd rather we designed roads for only those with the intelligence to know how to properly operate vehicles, but that's not good PR. The best thing we can do? Make it a bit harder to get a licence. In the mean time, we can't seem to handle multi-lane roundabouts, or roundabouts with large objects in the middle.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 05, 2018, 07:07:27 PM
\
As long as speeding, driving drunk, and inattentiveness aren't punishable by death, we should be trying to design for everyone, even morons. I fucking hate it. I'd rather we designed roads for only those with the intelligence to know how to properly operate vehicles, but that's not good PR. The best thing we can do? Make it a bit harder to get a licence. In the mean time, we can't seem to handle multi-lane roundabouts, or roundabouts with large objects in the middle.
And then someday it happens to you. You are not feeling well, didn't sleep last night, quarreled with your significant other... You make a small tiny little mistake. And now rescue has to cut you out of a wreck. And at the hospital doctor looks skeptical. ANd nurse doesn't look into your eyes....
And you think - if only that curve was a bit more sha.... and then the darkness falls on you.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on October 06, 2018, 11:13:20 AM
I'm not sure if it's been mentioned or not, but in Carmel, the 116th/Hazel Dell Pkwy signal has been reconfigured (https://goo.gl/G7jYLv) into this behemoth. We have a solid object in the middle, just in case someone forgets to turn their wheel on approach, and a third lane going southbound, for no obvious reason (2 lanes before and after, and northbound is only two lanes).

A simpler design with a flat center (with some bushes) might be prove safer long term, if tradephoric's data is to be believed.

The double right turn yield is pretty cool, though!

(https://www.dronegenuity.com/wp-content/uploads/2018/03/carmel-IN-roundabout-10.jpg)

The third lane going southbound helps with traffic volume during the morning rush hour.   The physical separation of the third lane by a median helps keep people in the appropriate lane.    This roundabout works very well to keep traffic moving.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 06, 2018, 11:38:47 AM
Based on the opinions of some in this thread, roundabouts need to be made idiot-proof, just because there's a good chance a law-breaker will be able to screw-up at a traffic light and make it through unscathed. What next, do we need to make electric fences that don't shock someone if they decide to pee on it? Lawyers and politicians are killing our society and whatever is left of "common sense".

I think it's reasonable to design roundabouts with the assumption that a vehicle, at some point in the roundabouts useful life, will plow through the central island at high speed.  Sure, it may be a rare event, but when someone flies through the middle of a roundabout at high speed do we want a retaining wall built in the central island to become a near certain death warrant?  And you can't argue that it's a money issue.  Unlike a runaway truck ramp that adds more money to the design of a freeway, designing a roundabout that's void of fixed objects in the central island would be less expensive than adding a retaining wall or massive palm trees or some ornate statue to the central island.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 06, 2018, 11:47:01 AM
Based on the opinions of some in this thread, roundabouts need to be made idiot-proof, just because there's a good chance a law-breaker will be able to screw-up at a traffic light and make it through unscathed. What next, do we need to make electric fences that don't shock someone if they decide to pee on it? Lawyers and politicians are killing our society and whatever is left of "common sense".

I think it's reasonable to design roundabouts with the assumption that a vehicle, at some point in the roundabouts useful life, will plow through the central island at high speed.  Sure, it may be a rare event, but when someone flies through the middle of a roundabout at high speed do we want a retaining wall built in the central island to become a near certain death warrant?  And you can't argue that it's a money issue.  Unlike a runaway truck ramp that adds more money to the design of a freeway, designing a roundabout that's void of fixed objects in the central island would be less expensive than adding a retaining wall or massive palm trees or some ornate statue to the central island.
This is an interesting dilemma. You can design roundabout so that a car can fly through and possibly crash head-on or T-bone on the other side - or catch it in the center, even at a cost to a runaway vehicle. Non-injuring catcher is the best of both worlds, but I am not sure how to achieve that in a footprint of tiny circles squeezed into urban surroundings.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 06, 2018, 12:18:50 PM
I'm not sure if it's been mentioned or not, but in Carmel, the 116th/Hazel Dell Pkwy signal has been reconfigured (https://goo.gl/G7jYLv) into this behemoth. We have a solid object in the middle, just in case someone forgets to turn their wheel on approach, and a third lane going southbound, for no obvious reason (2 lanes before and after, and northbound is only two lanes).

A simpler design with a flat center (with some bushes) might be prove safer long term, if tradephoric's data is to be believed.

The double right turn yield is pretty cool, though!

https://www.dronegenuity.com/wp-content/uploads/2018/03/carmel-IN-roundabout-10.jpg

The third lane going southbound helps with traffic volume during the morning rush hour.   The physical separation of the third lane by a median helps keep people in the appropriate lane.    This roundabout works very well to keep traffic moving.

I think I get it now. There's so much traffic coming from the east, there has to be a triple lane entrance going south, because there are less gaps. Going north, there isn't as much traffic coming from the west, so traffic is able to enter more often without stopping.

Does that line up with your experience?
Title: Re: Crash prone 'modern roundabouts'
Post by: skluth on October 06, 2018, 05:15:42 PM
^^
You should probably read the thread. Tradephoric and the rest of us have very carefully dissected the data behind roundabouts; it's not that cut and dry.

Consider this: the only thing forcing a driver to turn left or right is the steering wheel, not the geography surrounding the car.

"Carefully dissected" - Others might call it cherry-picked
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 06, 2018, 06:04:47 PM
The City of Dublin is making changes to the 161/Riverside Drive roundabout in mid-October.  The triple-lane roundabout has been plagued with a high number of crashes since it opened in August 2016.  A full year before the roundabout opened i had my doubts that the roundabout would be a success...

I have my doubts that the triple-lane roundabout currently under construction in Dublin, Ohio will see a reduction in total crashes (even though this is what the engineering manager of Dublin is predicting). Instead of learning from others mistakes, the City will forge ahead and construct it as a triple-lane roundabout.  A year later, the City will be perplexed why there are so many crashes at the roundabouts and hire a consultant to perform a safety audit.  The consultant, after being handed a big bag of money, will come to the conclusion that the roundabout should be reconfigured to a two-lane roundabout to reduce the total number of crashes.

Shortly after the roundabout opened the City of Dublin contracted Wisconsin firm MTJ Engineering for $29,046 to study the 161/Riverside roundabout.  After analyzing the roundabout they determined that a circulating lane should be removed on the northbound approach.  One report estimated the changes to the roundabout will cost the city $260,000 (that's in addition to the $29,046 contact with MTJ Engineering).  So all told, a few years after the roundabout opened, the city is spending nearly $300,000 to "fix" it.  Sounds like what i predicted would happen back in May 2015. 

(https://dublinohiousa.gov/dev/dev/wp-content/uploads/2018/09/lane-assignments-10-5-18.png)

Changes Scheduled for S.R. 161/Riverside Drive Roundabout
https://dublinohiousa.gov/construction-updates/changes-scheduled-for-s-r-161-riverside-drive-roundabout/
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 06, 2018, 10:57:24 PM
^^
You should probably read the thread. Tradephoric and the rest of us have very carefully dissected the data behind roundabouts; it's not that cut and dry.

Consider this: the only thing forcing a driver to turn left or right is the steering wheel, not the geography surrounding the car.

"Carefully dissected" - Others might call it cherry-picked

That might be a legitimate argument, if someone else would present some data. The only one doing that is Tradephoric. And he's limited to the cities that actually publish data and have roundabouts.

You're not the first person to accuse him of cherry-picking, but no one seems to be interested in actually disputing his data. The fact is that multi-lane roundabouts have a lot of crashes, and although they are not worse than signals, they don't seem to be any better at preventing serious injuries.

There's also a remarkable number of multi lane roundabouts that have had lanes removed (see above post); further evidence that they are not exactly good at preventing crashes when equipped with a lot of lanes.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on October 07, 2018, 10:33:25 PM
Ive been reading this thread for a few years, but only just decided to sign up.

I used to be big on "team roundabout" but frankly, it feels like American traffic engineers have ruined them. They're supposed to be safer, but when you add more and more lanes, bypasses, and exits that allow 40mph+ movement, all those safety benefits evaporate.

That being said there is one roundabout project I am in favor of.

This monster near Trenton, NJ has just been replaced a modern version. Frankly, I don't understand how a licensed engineer could look at this and think "yes, this is safe."

(https://i.imgur.com/w6GCKoy.jpg)

Google:
https://goo.gl/maps/H393MejJZhp

Streetview has a mix of new and old, but you can move the slider around to find some gems.

Old:
https://goo.gl/maps/ZRXeQwYBvX52

New:
https://goo.gl/maps/BnKaRToQBzK2
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 08, 2018, 12:30:57 AM
Ahh, the hamburger roundabout. One of my favorites! Only driven through them in DC (the one by the Watergate, to be specific). They are still quite popular in the UK (and are still being built, eg. the Headington Roundabout near Oxford), though all examples I'm familiar with are signalized.

Any idea what the crash numbers were at that old intersection?

My only issue with the old intersection was the tiny waiting areas between carriageways. Wouldn't surprise me if a few crashes occurred when vehicles that were too long to fit in the waiting area blocked the prior intersection, causing a T-bone collision. Probably why so many of these were eventually signalized.
Title: Re: Crash prone 'modern roundabouts'
Post by: johndoe on October 08, 2018, 03:04:59 PM
That Carmel example where a through lane proceeds on the right of the bypass splitter made me wonder about speed control (narrowing the entry paths to discourage speeding and hopefully encourage yielding). 
Here are examples in Conway, Arkansas:
(https://garverusa.com/assets/images/project-photos/transportation/highway-286-arkansas/highway-286-widening-and-interchange-improvements-4.JPG)
see more here: https://garverusa.com/services/transportation/projects/highway-286-widening-and-interchange-improvements

Here is an example in Victoria, B.C.:  https://goo.gl/maps/hDyb6ARYccM2

Has anyone seen other examples like this in North America?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 08, 2018, 03:12:23 PM
That Carmel example where a through lane proceeds on the right of the bypass splitter made me wonder about speed control (narrowing the entry paths to discourage speeding and hopefully encourage yielding). 
Here are examples in Conway, Arkansas:
(https://garverusa.com/assets/images/project-photos/transportation/highway-286-arkansas/highway-286-widening-and-interchange-improvements-4.JPG)
see more here: https://garverusa.com/services/transportation/projects/highway-286-widening-and-interchange-improvements

Here is an example in Victoria, B.C.:  https://goo.gl/maps/hDyb6ARYccM2

Has anyone seen other examples like this in North America?
I hope if there are som - it is only in the south. A bit of snow, and you may kiss goodbye to the suspension... And plows would have hard time with those features as well - on top of the fact that roundabouts are rarely fully cleaned up anyway.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 08, 2018, 05:18:46 PM
Here is an example in Victoria, B.C.:  https://goo.gl/maps/hDyb6ARYccM2

For what it's worth, the TAC (Transportation Association of Canada) considers that to be the first true turbo roundabout in North America.

Here's a short PDF chronicling its creation: https://goo.gl/6Hi1Qi

Note that the divider is flush with the ground, unlike the Arkansas example.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 08, 2018, 05:42:03 PM
Ive been reading this thread for a few years, but only just decided to sign up.

I used to be big on "team roundabout" but frankly, it feels like American traffic engineers have ruined them. They're supposed to be safer, but when you add more and more lanes, bypasses, and exits that allow 40mph+ movement, all those safety benefits evaporate.

That being said there is one roundabout project I am in favor of.

This monster near Trenton, NJ has just been replaced a modern version. Frankly, I don't understand how a licensed engineer could look at this and think "yes, this is safe."

(https://i.imgur.com/w6GCKoy.jpg)

Google:
https://goo.gl/maps/H393MejJZhp

Streetview has a mix of new and old, but you can move the slider around to find some gems.

Old:
https://goo.gl/maps/ZRXeQwYBvX52

New:
https://goo.gl/maps/BnKaRToQBzK2


Welcome to the forums James.  I agree that American traffic engineers have over-complicated the modern roundabout by trying to add more and more circulating lanes.  Take Michigan for example... of the 7 triple-lane roundabouts constructed in the state since 2005; 4 of them have already been downsized to double-lane roundabouts (mainly due to the high number of crashes).  The three triple-lane roundabouts that remain are the #2, #4, and #5 most crash prone intersections in Michigan for 2017.  All told, the three triple-lane roundabouts accounted for 451 total crashes including 46 injury crashes last year.  It's one thing if these roundabouts were the #2, #4, and #5 most heavily traveled intersections in the state, but they aren't by a long shot. 

The fact that so many triple-lane roundabouts are downsized shortly after being constructed is evidence that something is wrong.  A few of them don't get downsized, and those are the ones where you see 150 crashes/year with exceedingly high crash rates.  I'm sure we've all heard that insanity is doing the same thing over and over again and expecting a different result... we gotta question why triple-lane roundabouts are still being constructed in this country when nearly every one turns into an unmitigated disaster! 

Top 5 crash prone intersections in Michigan (2017)
#1. 11 Mile Road/I-696 at Van Dyke Avenue in Warren/Center Line, Macomb County
194 total crashes, 32 injury crashes

#2. 18 ½ Mile Road at Van Dyke Avenue in Sterling Heights, Macomb County
165 total crashes, 13 injury crashes (triple-lane roundabout constructed in 2005)

#3. Telegraph Road at 12 Mile Road in Southfield, Oakland County
150 Total Crashes, 23 Injury Crashes

#4. Orchard Lake Road at 14 Mile road in Farmington Hills/West Bloomfield Township, Oakland County
144 total crashes, 24 Injury crashes (triple-lane roundabout constructed in 2015)

#5. Martin Parkway at Pontiac Trail in Commerce Township, Oakland County
142 total crashes, 9 injury crashes (triple-lane roundabout constructed in 2011)
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on October 08, 2018, 06:15:52 PM
From the previous page, this looks incredibly dangerous.

A pedestrian standing at the star needs to monitor 4 lanes of traffic before they can cross safely. Worse, the drivers at 1 and 2 will be looking only left and will take the first clear slot the accelerate straight into the crosswalk before confirming it is clear.

The crosswalk with the arrow has a triple threat, and the straight exit means vehicles will be accelerating quickly out of the circle.

Worse, the roundabout is designed so bicyclists exit the lane and use the crosswalks (note the ramps). Thats incredibly dangerous at the speeds this is designed for.

Incredibly irresponsible design.

(https://i.imgur.com/f7Y3jLB.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: 6a on October 08, 2018, 06:22:17 PM
The City of Dublin is making changes to the 161/Riverside Drive roundabout in mid-October.  The triple-lane roundabout has been plagued with a high number of crashes since it opened in August 2016.  A full year before the roundabout opened i had my doubts that the roundabout would be a success...

I have my doubts that the triple-lane roundabout currently under construction in Dublin, Ohio will see a reduction in total crashes (even though this is what the engineering manager of Dublin is predicting). Instead of learning from others mistakes, the City will forge ahead and construct it as a triple-lane roundabout.  A year later, the City will be perplexed why there are so many crashes at the roundabouts and hire a consultant to perform a safety audit.  The consultant, after being handed a big bag of money, will come to the conclusion that the roundabout should be reconfigured to a two-lane roundabout to reduce the total number of crashes.

Shortly after the roundabout opened the City of Dublin contracted Wisconsin firm MTJ Engineering for $29,046 to study the 161/Riverside roundabout.  After analyzing the roundabout they determined that a circulating lane should be removed on the northbound approach.  One report estimated the changes to the roundabout will cost the city $260,000 (that's in addition to the $29,046 contact with MTJ Engineering).  So all told, a few years after the roundabout opened, the city is spending nearly $300,000 to "fix" it.  Sounds like what i predicted would happen back in May 2015. 

(https://dublinohiousa.gov/dev/dev/wp-content/uploads/2018/09/lane-assignments-10-5-18.png)

Changes Scheduled for S.R. 161/Riverside Drive Roundabout
https://dublinohiousa.gov/construction-updates/changes-scheduled-for-s-r-161-riverside-drive-roundabout/
I am not the least bit shocked by this development. While I generally don’t mind roundabouts, this particular one is a pain in the ass. I’ve attached a visual representation of going through it during rush hour:

(https://uploads.tapatalk-cdn.com/20181008/505c5dcbd29f61bee2a8c7a865de8ec6.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: NoGoodNamesAvailable on October 08, 2018, 07:08:42 PM
From the previous page, this looks incredibly dangerous.

A pedestrian standing at the star needs to monitor 4 lanes of traffic before they can cross safely. Worse, the drivers at 1 and 2 will be looking only left and will take the first clear slot the accelerate straight into the crosswalk before confirming it is clear.

The crosswalk with the arrow has a triple threat, and the straight exit means vehicles will be accelerating quickly out of the circle.

Worse, the roundabout is designed so bicyclists exit the lane and use the crosswalks (note the ramps). Thats incredibly dangerous at the speeds this is designed for.

Incredibly irresponsible design.

(https://i.imgur.com/f7Y3jLB.jpg)

Yeah, that is seriously awful. Not only is it a triple threat, but approaching drivers would have to stop in the roundabout, blocking both crossing lanes to be a safe distance from the crosswalk.

I don't understand why we accept things like this. It's borderline negligent. Considering how sparse the area looks, I'm sure setting the crosswalks a bit farther back and signalizing them wouldn't significantly disrupt traffic. Or if you're set on a design like this at least use raised crosswalks. Or literally any other treatment beyond the bare minimum.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 08, 2018, 10:01:50 PM
Worse, the roundabout is designed so bicyclists exit the lane and use the crosswalks (note the ramps). Thats incredibly dangerous at the speeds this is designed for.

Some would say that bikes shouldn't be using the roundabouts to begin with. But that sets a dangerous precedent. Streets should be designed for everybody, not cars first and everybody else last (as is clearly the case here).

Is there accommodation? Yes, they didn't leave anyone out, but there has to be something better. I love underpasses for pedestrians and cyclists, but I'm not sure if that would work here given the water table. Overpasses are rather unsightly. Perhaps raising the roundabout and keeping the trails at ground level would have been an option. Yes that would be expensive, but cities have a duty to design an environment that is relatively equal to all modes. This is not an equal design.

Are there a lot of pedestrians in the area? Probably not, but who can blame them? I certainly wouldn't wanna walk through that mess.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on October 09, 2018, 09:04:10 AM
Worse, the roundabout is designed so bicyclists can exit the lane and use the crosswalks (note the ramps).

Fixed that for you. Frankly, I don't know of a roundabout that has or can force a bicyclist to do anything except to make their own decision. As protected by most state laws, bicyclists have the right to "take the lane" and remain as a part of the motorized traffic flow or they can exit the roundabout and cross the approaches as a pedestrian.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 09, 2018, 10:46:53 AM
That Carmel example where a through lane proceeds on the right of the bypass splitter made me wonder about speed control (narrowing the entry paths to discourage speeding and hopefully encourage yielding). 
Here are examples in Conway, Arkansas:
(https://garverusa.com/assets/images/project-photos/transportation/highway-286-arkansas/highway-286-widening-and-interchange-improvements-4.JPG)
see more here: https://garverusa.com/services/transportation/projects/highway-286-widening-and-interchange-improvements

Here is an example in Victoria, B.C.:  https://goo.gl/maps/hDyb6ARYccM2

Has anyone seen other examples like this in North America?
I hope if there are som - it is only in the south. A bit of snow, and you may kiss goodbye to the suspension... And plows would have hard time with those features as well - on top of the fact that roundabouts are rarely fully cleaned up anyway.

There is already a disproportionately high number of fatal crashes at roundabouts involving motorcyclists and i question if this type of design with all that raised curbing would make things safer for them.  An interesting thing about the Conway roundabouts is that they were designed to accommodate three lanes of circulating traffic, yet they are initially stripped for two lanes.  Other triple-lane roundabouts that have been downsized to two-lanes often have their splitter islands modified as part of the reconfiguration to prevent the roundabout from being expanded to a triple-lane roundabout in the future (at least not without a tremendous cost).  After dealing with a triple-lane roundabout, some communities just know that they aren't going to try it again.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on October 09, 2018, 11:11:39 AM
High speed, driver feel asleep, drink driver, truck with no brakes.... What a joke! That's an argument against 'something' but it has f#@$ all to do with roundabouts.

But they all hit something related to the design of the roundabout. Either a sign leading up to it, or the central island.

Would some of them have eventually crashed? Perhaps, but roundabouts create geographical hazards, which make them hard to navigate if you didn't notice them.

You can run a signal. You can't run a roundabout.

Based on the opinions of some in this thread, roundabouts need to be made idiot-proof, just because there's a good chance a law-breaker will be able to screw-up at a traffic light and make it through unscathed. What next, do we need to make electric fences that don't shock someone if they decide to pee on it? Lawyers and politicians are killing our society and whatever is left of "common sense".

As long as speeding, driving drunk, and inattentiveness aren't punishable by death, we should be trying to design for everyone, even morons. I fucking hate it. I'd rather we designed roads for only those with the intelligence to know how to properly operate vehicles, but that's not good PR. The best thing we can do? Make it a bit harder to get a licence. In the mean time, we can't seem to handle multi-lane roundabouts, or roundabouts with large objects in the middle.

Remember, roundabout and road designs aren't designed for just morons, but for those that become entangled with those morons.

Let's take the guardrail for example:  You are on a road.  You are driving perfectly fine.  Suddenly, someone T-bones you.  You hit the guardrail, which stops you from going down an embankment.  You were an innocent victim in the accident, but without that guardrail, you would've been a dead victim.  Thus, roads are designed not just to stop morons to fly off the road; they're designed to save the innocent victims as well.



Ive been reading this thread for a few years, but only just decided to sign up.

I used to be big on "team roundabout" but frankly, it feels like American traffic engineers have ruined them. They're supposed to be safer, but when you add more and more lanes, bypasses, and exits that allow 40mph+ movement, all those safety benefits evaporate.

That being said there is one roundabout project I am in favor of.

This monster near Trenton, NJ has just been replaced a modern version. Frankly, I don't understand how a licensed engineer could look at this and think "yes, this is safe."

(https://i.imgur.com/w6GCKoy.jpg)

Google:
https://goo.gl/maps/H393MejJZhp

Streetview has a mix of new and old, but you can move the slider around to find some gems.

Old:
https://goo.gl/maps/ZRXeQwYBvX52

New:
https://goo.gl/maps/BnKaRToQBzK2


Welcome!

To answer the question: Different times, and traffic was much lighter.  NJDOT did this a lot.  Along with this intersection, NJ 70/73 had a cut-thru, US 1 has a cut thru, etc.  And they still do it, such as with the Atlantic City Airport Circle.  Granted, this one was a bit different, but it worked surprisingly ok!
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 09, 2018, 01:00:47 PM
NJDOT did this a lot.  Along with this intersection, NJ 70/73 had a cut-thru, US 1 has a cut thru, etc.  And they still do it, such as with the Atlantic City Airport Circle.  Granted, this one was a bit different, but it worked surprisingly ok!

I was reading a story that locals already want the intersection modified to improve flow or something? I thought that was the point of the change?
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 09, 2018, 01:04:58 PM
From the previous page, this looks incredibly dangerous.

A pedestrian standing at the star needs to monitor 4 lanes of traffic before they can cross safely. Worse, the drivers at 1 and 2 will be looking only left and will take the first clear slot the accelerate straight into the crosswalk before confirming it is clear.

The crosswalk with the arrow has a triple threat, and the straight exit means vehicles will be accelerating quickly out of the circle.

Worse, the roundabout is designed so bicyclists exit the lane and use the crosswalks (note the ramps). Thats incredibly dangerous at the speeds this is designed for.

Incredibly irresponsible design.

(https://i.imgur.com/f7Y3jLB.jpg)

[in reply to the highlighted portion]

Then they are terrible drivers.  At one-way intersections (which is sort of what a roundabout entrance is), you should always look both ways for pedestrians.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on October 09, 2018, 01:19:32 PM
NJDOT did this a lot.  Along with this intersection, NJ 70/73 had a cut-thru, US 1 has a cut thru, etc.  And they still do it, such as with the Atlantic City Airport Circle.  Granted, this one was a bit different, but it worked surprisingly ok!

I was reading a story that locals already want the intersection modified to improve flow or something? I thought that was the point of the change?

Which one?  The AC Airport circle definitely had some operational issues when it first opened, mostly due to traffic light timing.  I believe that was resolved.  As far as the Whitehorse Circle goes, I haven't heard of any issues, although I'm sure those that were used to having the right-of-way when entering the roundabout are peeved they now have to yield to those already in the roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 09, 2018, 02:23:33 PM
Then they are terrible drivers.  At one-way intersections (which is sort of what a roundabout entrance is), you should always look both ways for pedestrians.
How often you go through roundabouts?
If traffic is moderate or worse, you often have to take that gap - or wait till next gap shows up. Maybe.
A very quick glance right is the most you can do, often while already accelerating.
THat is what happens when you create race conditions, no protected phases whatsoever - and if you're in disadvantaged downstream position... Use it or loose it.

That is exactly why roundabouts may be a good idea for LIGHT traffic areas ONLY. 
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on October 09, 2018, 04:43:43 PM
those crosswalks are far enough back where that issue wouldnt likely happen.  anyway, here is a new beauty in greenwood, in

https://www.indystar.com/story/news/2018/10/09/greenwoods-new-roundabout-one-ups-carmel-adding-jug-handle/1565465002/
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on October 09, 2018, 06:15:39 PM
From the previous page, this looks incredibly dangerous.

A pedestrian standing at the star needs to monitor 4 lanes of traffic before they can cross safely. Worse, the drivers at 1 and 2 will be looking only left and will take the first clear slot the accelerate straight into the crosswalk before confirming it is clear.

The crosswalk with the arrow has a triple threat, and the straight exit means vehicles will be accelerating quickly out of the circle.

Worse, the roundabout is designed so bicyclists exit the lane and use the crosswalks (note the ramps). Thats incredibly dangerous at the speeds this is designed for.

Incredibly irresponsible design.

(https://i.imgur.com/f7Y3jLB.jpg)

[in reply to the highlighted portion]

Then they are terrible drivers.  At one-way intersections (which is sort of what a roundabout entrance is), you should always look both ways for pedestrians.

Aren't you supposed to design for how people actually behave, and not how in a perfect world you would want them to behave?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 09, 2018, 07:47:34 PM
here is a new beauty in greenwood, in

https://www.indystar.com/story/news/2018/10/09/greenwoods-new-roundabout-one-ups-carmel-adding-jug-handle/1565465002/

(https://interactives.indystar.com/gifs/greenwood_roundabout.gif)

The pedestrian crosswalk crossing the south leg of Smith Valley Road and U.S. 31 is 180 feet long.  Assuming they are following MUTCD guidelines, when a pedestrian actuation occurs Smith Valley thru phase would need to run a minimum of 56 seconds to fit the pedestrian times.  That's just one phase... you still got to run U.S. 31 thru and U.S. 31 left turn phases.  The point is the cycle length at U.S. 31 and Smith Valley Road is going to be running pretty high.  I can't see how this triple-lane roundabout is going to function well when it's just a few hundred feet away from a major signalized intersection running a high cycle length.  Sure, the jug handle eliminates a dedicated left turn phase on Smith Valley Road, but it's still a 3-phase signal.  They design this complex intersection with bypasses, jug handles, and a complex triple-lane roundabout.. yet they still haven't eliminated dangerous left-turn movements at the U.S. 31/Smith Valley intersection?  With that much real estate to work with you think they could have come up with a better design. 

Silverback1065, do you live close to this intersection?   I'm really curious how long the Smith Valley thru phase runs when a pedestrian actuation occurs along that 180 foot crosswalk.  Maybe you could put a stopwatch to it!   :D
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on October 09, 2018, 08:34:45 PM
Haha I don't live too far from it.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 10, 2018, 01:26:21 AM
NJDOT did this a lot.  Along with this intersection, NJ 70/73 had a cut-thru, US 1 has a cut thru, etc.  And they still do it, such as with the Atlantic City Airport Circle.  Granted, this one was a bit different, but it worked surprisingly ok!

I was reading a story that locals already want the intersection modified to improve flow or something? I thought that was the point of the change?

Which one?  The AC Airport circle definitely had some operational issues when it first opened, mostly due to traffic light timing.  I believe that was resolved.  As far as the Whitehorse Circle goes, I haven't heard of any issues, although I'm sure those that were used to having the right-of-way when entering the roundabout are peeved they now have to yield to those already in the roundabout.

The AC Airport Circle. Here's the story (from 2014): https://goo.gl/dypsJT



The pedestrian crosswalk crossing the south leg of Smith Valley Road and U.S. 31 is 180 feet long.  Assuming they are following MUTCD guidelines, when a pedestrian actuation occurs Smith Valley thru phase would need to run a minimum of 56 seconds to fit the pedestrian times...Silverback1065, do you live close to this intersection?   I'm really curious how long the Smith Valley thru phase runs when a pedestrian actuation occurs along that 180 foot crosswalk.  Maybe you could put a stopwatch to it!   :D

That would be beneficial for the roundabout right? Surprised you'd bring that up.

FWIW, I've seen four lane crossings here in WA that run 15-second walk cycles (3 walk, 12 don't walk), but sometimes extend if pedestrians are present. No idea how it knows. This is the intersection: https://goo.gl/hRkvAk (FYA-lockout when ped signal is active).
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on October 10, 2018, 09:44:50 AM
Then they are terrible drivers.  At one-way intersections (which is sort of what a roundabout entrance is), you should always look both ways for pedestrians.
How often you go through roundabouts?
If traffic is moderate or worse, you often have to take that gap - or wait till next gap shows up. Maybe.
A very quick glance right is the most you can do, often while already accelerating.
THat is what happens when you create race conditions, no protected phases whatsoever - and if you're in disadvantaged downstream position... Use it or loose it.

That is exactly why roundabouts may be a good idea for LIGHT traffic areas ONLY.
Concord Rotary works pretty well, despite the heavy traffic.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 10, 2018, 10:13:19 AM
Then they are terrible drivers.  At one-way intersections (which is sort of what a roundabout entrance is), you should always look both ways for pedestrians.
How often you go through roundabouts?
If traffic is moderate or worse, you often have to take that gap - or wait till next gap shows up. Maybe.
A very quick glance right is the most you can do, often while already accelerating.
THat is what happens when you create race conditions, no protected phases whatsoever - and if you're in disadvantaged downstream position... Use it or loose it.

That is exactly why roundabouts may be a good idea for LIGHT traffic areas ONLY.
Concord Rotary works pretty well, despite the heavy traffic.
Works pretty well meaning no fatal accidents this year?
Problem is simple: you need pretty exhaustive statistics to say "it works well". Fact that traffic is normally flowing means NOTHING in terms of safety - it takes one rare event to ruin the safety record.
Second issue is my pet issue - regular driving through smallish roundabout necessarily means you need to reduce your safety margins. Which may show up elsewhere.
Same story as posting highway at 30 MPH - and then wondering why nobody cares about any speed limits.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 10, 2018, 10:14:41 AM
The pedestrian crosswalk crossing the south leg of Smith Valley Road and U.S. 31 is 180 feet long.  Assuming they are following MUTCD guidelines, when a pedestrian actuation occurs Smith Valley thru phase would need to run a minimum of 56 seconds to fit the pedestrian times...

That would be beneficial for the roundabout right? Surprised you'd bring that up.

Yes, when Smith Valley Road is green it would allow the roundabout traffic to clear which would be beneficial.  But if Smith Valley Road requires 56 seconds to run it's thru phase, then U.S. 31 (which i would consider the main-street at this intersection) would likely require the same amount of time for it's thru phase, if not more.  Add to that the NB/SB US31 left turn phase and you are looking at Smith Valley Road being red for ~90 seconds while traffic queues up between the roundabout and US 31.

It reminds me of the roundabout at 14 Mile & Orchard Lake.  It too is a triple-lane roundabout just a few hundred feet from a signalized intersection and I've often observed Orchard Lake Road traffic backing up through the roundabout as they hit a red light at the signal just north of the roundabout.  The signals surrounding that roundabout are simple 2-phase signals and only run max 70 second cycle lengths.  The cycle length at the new Greenwood, Indiana roundabout would likely have to run 140 second cycles just to fit the peds. 

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 10, 2018, 11:09:59 AM
Greenwood roundabout at Smith Valley and Madison Ave opens early
https://www.wthr.com/article/greenwood-roundabout-smith-valley-and-madison-ave-opens-early

Looks like they are opening the roundabout early.  Here is a simulation of the roundabout in action.  If you notice in the model, WB Smith Valley Road is utilizing all 3-lanes equally as traffic queues up between U.S. 31 and the roundabout.  Even with traffic utilizing all 3-lanes perfectly, traffic is not that far from queuing up through the roundabout.  But in the real world drivers aren't going to want to utilize that far right lane.  Smith Valley Road merges back down to 2-lanes just past the intersection and unless if you are entering a drive just past the intersection, there's no reason to get over into the far right lane.  The first 8 or 9 vehicle who queue up between U.S. 31 and the roundabout have no incentive to get over because they know they will easily make it through the green light.  Drivers are selfish... as long as they aren't the ones queuing up through the roundabout, they aren't going to pull into that far right lane and force themselves to merge over past the intersection.  No, only when you are the driver blocking the roundabout would you want to get over into that third lane and at that point you can't because the road only widens out to 3 lanes just past the roundabout.  This model clearly doesn't come close to matching real-world conditions and traffic backing up through the roundabout will be a real problem.
 

EDIT:  There will be some selfish drivers who get into that right most lane who want to be that first car in line and gun it when the light turns green, but that's only the case with a couple cars.  The next selfish driver who was thinking of doing the same thing already sees a few cars in that right most lane, and may assume they are going to be turning into a drive past the intersection - so they don't bother getting over (since by doing so it would quite possibly slow down their drive, not make it faster.. they don't want to get stuck behind that guy turning into a driveway past the intersection). 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 10, 2018, 01:01:45 PM
From the previous page, this looks incredibly dangerous.

A pedestrian standing at the star needs to monitor 4 lanes of traffic before they can cross safely. Worse, the drivers at 1 and 2 will be looking only left and will take the first clear slot the accelerate straight into the crosswalk before confirming it is clear.

The crosswalk with the arrow has a triple threat, and the straight exit means vehicles will be accelerating quickly out of the circle.

Worse, the roundabout is designed so bicyclists exit the lane and use the crosswalks (note the ramps). Thats incredibly dangerous at the speeds this is designed for.

Incredibly irresponsible design.

(https://i.imgur.com/f7Y3jLB.jpg)

[in reply to the highlighted portion]

Then they are terrible drivers.  At one-way intersections (which is sort of what a roundabout entrance is), you should always look both ways for pedestrians.

Aren't you supposed to design for how people actually behave, and not how in a perfect world you would want them to behave?

By your logic, then, all one-way roads should be eliminated because cross-traffic won't be looking for pedestrians in the other direction.  But that's ludicrous.  In the roundabout example pictured above, a pedestrian wouldn't even be out the side window but rather in full view of the windshield.

Then they are terrible drivers.  At one-way intersections (which is sort of what a roundabout entrance is), you should always look both ways for pedestrians.
How often you go through roundabouts?
If traffic is moderate or worse, you often have to take that gap - or wait till next gap shows up. Maybe.
A very quick glance right is the most you can do, often while already accelerating.
THat is what happens when you create race conditions, no protected phases whatsoever - and if you're in disadvantaged downstream position... Use it or loose it.

That is exactly why roundabouts may be a good idea for LIGHT traffic areas ONLY. 

I go through roundabouts somewhat regularly, although there aren't any multi-lane ones in my area.

And no, you never "have to take that gap" with disregard for any pedestrians.  It's the same as if you're waiting to turn right on a red light (or a slip lane with a YIELD sign, to be more comparable) with steady traffic from your left.  You don't get to just GO when a short break in traffic appears without first checking for pedestrians on your right.  If there are pedestrians crossing the street, then there is no gap.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 10, 2018, 01:07:08 PM
selfish responsible drivers who get into that right most lane who want to be that first car in line and gun it when the light turns green understand the importance of not letting a whole lane of storage space lie empty

FTFY.

Of course, that doesn't actually negate your assertion, because I agree that a large majority of driver's won't use the lane for precisely the reason you've outlined.  I just think it's foolish to call people who use a road as it was designed to be used, thereby helping to avoid the exact tailback situation you've described, as "selfish".
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 10, 2018, 01:13:07 PM

I go through roundabouts somewhat regularly, although there aren't any multi-lane ones in my area.

And no, you never "have to take that gap" with disregard for any pedestrians.  It's the same as if you're waiting to turn right on a red light (or a slip lane with a YIELD sign, to be more comparable) with steady traffic from your left.  You don't get to just GO when a short break in traffic appears without first checking for pedestrians on your right.  If there are pedestrians crossing the street, then there is no gap.
I do also compare roundabouts with right on red. And while similarity is clear, there is one fundamental difference: if the traffic is heavy, you can wait for green - but at roundabout you cannot just wait until protected phase. That basically reduces the threshold of what is acceptable and what is not - it is not MAY turn on red, it is MUST turn on red. That, of course, affects overall safety. In this case, pedestrians are just least visible and most vulnerable road users. I do not advocate running over them or demanding right of way on a crosswalk, I just say that probability of accident is at stake.
And apparently you don't see the fun of driving through complex roundabouts and roundabout clusters. I do 7 circles per round trip commute - and 4 of those are multilanes, so I have my opinion based on my own experience.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 10, 2018, 01:35:42 PM
it is not MAY turn on red, it is MUST turn on red.

FYI, New Jersey is literally a "MUST turn on red" state.

Quote from: 2016 New Jersey Revised Statutes
39:4-115
Making right or left turn

The driver of a vehicle or the motorman of a streetcar ... intending to turn right at an intersection where traffic is controlled by a traffic control signal shall, unless an official sign of the State, municipality, or county authority having jurisdiction over the intersection prohibits the same, proceed to make the turn upon a "stop" or "caution" signal with proper care to avoid accidents after coming to a full stop, observing traffic in all directions, yielding to other vehicular traffic traveling in a direction in which the turn will be made, and stopping and remaining stopped for pedestrians crossing the roadway within a marked crosswalk, or at an unmarked crosswalk, into which the driver is turning.

Therefore, every stoplight intersection in New Jersey is just like a roundabout during its red phase wrt the situation you describe.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 10, 2018, 02:12:02 PM
it is not MAY turn on red, it is MUST turn on red.

FYI, New Jersey is literally a "MUST turn on red" state.

Quote from: 2016 New Jersey Revised Statutes
39:4-115
Making right or left turn

The driver of a vehicle or the motorman of a streetcar ... intending to turn right at an intersection where traffic is controlled by a traffic control signal shall, unless an official sign of the State, municipality, or county authority having jurisdiction over the intersection prohibits the same, proceed to make the turn upon a "stop" or "caution" signal with proper care to avoid accidents after coming to a full stop, observing traffic in all directions, yielding to other vehicular traffic traveling in a direction in which the turn will be made, and stopping and remaining stopped for pedestrians crossing the roadway within a marked crosswalk, or at an unmarked crosswalk, into which the driver is turning.

Therefore, every stoplight intersection in New Jersey is just like a roundabout during its red phase wrt the situation you describe.
I wonder if that "shall" is ever enforced...
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on October 10, 2018, 02:14:00 PM
it is not MAY turn on red, it is MUST turn on red.

FYI, New Jersey is literally a "MUST turn on red" state.

Quote from: 2016 New Jersey Revised Statutes
39:4-115
Making right or left turn

The driver of a vehicle or the motorman of a streetcar ... intending to turn right at an intersection where traffic is controlled by a traffic control signal shall, unless an official sign of the State, municipality, or county authority having jurisdiction over the intersection prohibits the same, proceed to make the turn upon a "stop" or "caution" signal with proper care to avoid accidents after coming to a full stop, observing traffic in all directions, yielding to other vehicular traffic traveling in a direction in which the turn will be made, and stopping and remaining stopped for pedestrians crossing the roadway within a marked crosswalk, or at an unmarked crosswalk, into which the driver is turning.

Therefore, every stoplight intersection in New Jersey is just like a roundabout during its red phase wrt the situation you describe.
I wonder if that "shall" is ever enforced...

I recall one news story from years ago where someone was pulled over for failing to turn right on red, and it was upheld in court.

Why was it newsworthy?  Because it was basically the only ticket ever written for it.  I seriously doubt if anyone else has been pulled over for failing to turn right on red.  If anything, it appears people tense up and won't turn right on red when there's a cop behind them.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 10, 2018, 08:11:33 PM
I wonder if that "shall" is ever enforced...

Though I think we're on the same side here, this is the first time I've seen you unable to come up with a proper response.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 10, 2018, 08:45:33 PM
I wonder if that "shall" is ever enforced...

Though I think we're on the same side here, this is the first time I've seen you unable to come up with a proper response (no matter how badly worded they often are lol).
Thing is, the way I read NJ law it indeed requires a turn on red. No common prohibitions like hazmat or school bus as well.
I suspect it was supposed to be "driver making such turn SHALL exercise caution etc", but it morphed into SHALL turn.

My root argument still holds, IF you feel unsafe, you can (should) wait until green light - the option which is not available for roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 11, 2018, 01:09:15 PM
I wonder if that "shall" is ever enforced...

Though I think we're on the same side here, this is the first time I've seen you unable to come up with a proper response (no matter how badly worded they often are lol).
Thing is, the way I read NJ law it indeed requires a turn on red. No common prohibitions like hazmat or school bus as well.
I suspect it was supposed to be "driver making such turn SHALL exercise caution etc", but it morphed into SHALL turn.

My root argument still holds, IF you feel unsafe, you can (should) wait until green light - the option which is not available for roundabouts.

I've been thinking about this, and I thought it would be easy to discredit by posting an example of a stoplight intersection with splitter islands and YIELD signs controlling right turns.  However, all the examples I can find of that setup have the pedestrian crossing through the slip lanes onto the splitter islands themselves–not downstream of the intersection, which is where they are typically placed at roundabouts.  Contrast this pedestrian crossing at such a stoplight intersection (https://goo.gl/maps/TXpmzEg1ZZG2) with this pedestrian crossing at a multi-lane roundabout (https://goo.gl/maps/FwLWoukihis).  In essence, by putting the routing pedestrians through the splitter islands, the stoplight configuration presents right-turning traffic with only one crosswalk instead of the two crosswalks said traffic encounters at a roundabout:  the upstream and downstream crosswalks are combined into one midpoint crosswalk.  Furthermore, that midpoint crosswalk is no less visible than the upstream one at a roundabout, and it is arguably more visible than the downstream one.  Exactly how much more visible would be speculation, and I still assert that those pedestrians would still be quite visible through the windshield.  But I concede that there is certainly a disadvantage, however small, to the roundabout setup.

By the way...  The below relates to this sub-topic.
Click on the GSV link and zoom in on the sign

I suppose when you really get down to it, not making the turn if you have any doubt is the prudent way to proceed, especially if there's a cop around and you're concerned that he might ticket you if you turn and it's not allowed.

In other words, you're never required to turn on red if you don't want to do so, even if it bugs the crap out of the people waiting on line behind you. I can think of times when I haven't turned on red simply because I felt I couldn't see well enough to be able to determine whether the road was clear.
Something I've wondered: can you wait here for eight hours until the light turns green? http://maps.google.com/maps?ll=35.218759,-80.835364&spn=0.007284,0.020599&t=k&z=17&layer=c&cbll=35.218616,-80.835317&panoid=XtfTmHxSq9fhdRrxL_1Luw&cbp=12,280.33,,1,-6.94
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 11, 2018, 02:37:02 PM
I wonder if that "shall" is ever enforced...

Though I think we're on the same side here, this is the first time I've seen you unable to come up with a proper response (no matter how badly worded they often are lol).
Thing is, the way I read NJ law it indeed requires a turn on red. No common prohibitions like hazmat or school bus as well.
I suspect it was supposed to be "driver making such turn SHALL exercise caution etc", but it morphed into SHALL turn.

My root argument still holds, IF you feel unsafe, you can (should) wait until green light - the option which is not available for roundabouts.

I've been thinking about this, and I thought it would be easy to discredit by posting an example of a stoplight intersection with splitter islands and YIELD signs controlling right turns.  However, all the examples I can find of that setup have the pedestrian crossing through the slip lanes onto the splitter islands themselves–not downstream of the intersection, which is where they are typically placed at roundabouts.  Contrast this pedestrian crossing at such a stoplight intersection (https://goo.gl/maps/TXpmzEg1ZZG2) with this pedestrian crossing at a multi-lane roundabout (https://goo.gl/maps/FwLWoukihis).  In essence, by putting the routing pedestrians through the splitter islands, the stoplight configuration presents right-turning traffic with only one crosswalk instead of the two crosswalks said traffic encounters at a roundabout:  the upstream and downstream crosswalks are combined into one midpoint crosswalk.  Furthermore, that midpoint crosswalk is no less visible than the upstream one at a roundabout, and it is arguably more visible than the downstream one.  Exactly how much more visible would be speculation, and I still assert that those pedestrians would still be quite visible through the windshield.  But I concede that there is certainly a disadvantage, however small, to the roundabout setup.

By the way...  The below relates to this sub-topic.
Click on the GSV link and zoom in on the sign

I suppose when you really get down to it, not making the turn if you have any doubt is the prudent way to proceed, especially if there's a cop around and you're concerned that he might ticket you if you turn and it's not allowed.

In other words, you're never required to turn on red if you don't want to do so, even if it bugs the crap out of the people waiting on line behind you. I can think of times when I haven't turned on red simply because I felt I couldn't see well enough to be able to determine whether the road was clear.
Something I've wondered: can you wait here for eight hours until the light turns green? http://maps.google.com/maps?ll=35.218759,-80.835364&spn=0.007284,0.020599&t=k&z=17&layer=c&cbll=35.218616,-80.835317&panoid=XtfTmHxSq9fhdRrxL_1Luw&cbp=12,280.33,,1,-6.94

If you will, you're looking for some rare and marginal examples to counter comparison of mainstream design features. Which would only mean that fundamentally good designs can be ruined - which is often not that difficult to achieve.
Since there are many situations where some adjustment of baseline is required, you can find examples of anything designed well and poorly - even when it seems impossible to mess things up. Add individual designer's preferences, non-trivial streets layout, poorly worded laws... All that doesn't change basic principles, though.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 11, 2018, 04:23:50 PM
Thanks for bring up slip lanes, kphoger. One of the reasons those are so often failures when it comes to pedestrians is that, much like at roundabouts, drivers know that the movement does not require waiting for a green light, or stopping and giving way due to a red light (slip lanes with stop signs (https://goo.gl/3t9vAa), from my experience, have high rates of disobedience, so I prefer not to mention them differently than slip lanes with yield signs). When drivers approach a road situation in which they are able to keep going without stopping, they will look for other cars, and keep going.

Most of the roads in this country simply don't have enough pedestrian activity for the idea of "yield to pedestrian" to be an active, continuous thought for most drivers. At roundabouts, it's like having 8 different slip lanes, each requiring drivers to watch for pedestrians. If slip lanes don't work, I don't see how roundabouts could possibly be any good at accommodating pedestrians. At least modern slip lanes, like those used in Australia, have changed the design to be more of a right-angle turn, to improve pedestrian visibility, and cut-down on drivers just flying through the turn without yielding at all. Many new roundabouts have angles like this (the one above in Carmel has it for the right turns), but the real issue is when peds are crossing the exit legs.
Title: Re: Crash prone 'modern roundabouts'
Post by: NoGoodNamesAvailable on October 11, 2018, 05:18:29 PM
Most of the roads in this country simply don't have enough pedestrian activity for the idea of "yield to pedestrian" to be an active, continuous thought for most drivers. At roundabouts, it's like having 8 different slip lanes, each requiring drivers to watch for pedestrians. If slip lanes don't work, I don't see how roundabouts could possibly be any good at accommodating pedestrians. At least modern slip lanes, like those used in Australia, have changed the design to be more of a right-angle turn, to improve pedestrian visibility, and cut-down on drivers just flying through the turn without yielding at all. Many new roundabouts have angles like this (the one above in Carmel has it for the right turns), but the real issue is when peds are crossing the exit legs.

It is definitely easy to understate the importance of basic geometry decisions on driver behavior, e.g. pedestrian yield rates. Putting multilane monstrosities aside, look at the Dutch (https://i.imgur.com/ykQbvZe.png) best practice for roundabout geometry compared to the FHWA (https://i.imgur.com/qUSzal9.png) best practice, which would be considered unacceptable in the Netherlands.

The radial Dutch design uses just as sharp an angle for exits as in does for entrances, where the more tangential American design prioritizes maximum exit speed. Add raised crosswalks to the Dutch design and you will get excellent safety results anywhere, regardless of pedestrian volumes.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 11, 2018, 06:39:09 PM
Most of the roads in this country simply don't have enough pedestrian activity for the idea of "yield to pedestrian" to be an active, continuous thought for most drivers. At roundabouts, it's like having 8 different slip lanes, each requiring drivers to watch for pedestrians. If slip lanes don't work, I don't see how roundabouts could possibly be any good at accommodating pedestrians. At least modern slip lanes, like those used in Australia, have changed the design to be more of a right-angle turn, to improve pedestrian visibility, and cut-down on drivers just flying through the turn without yielding at all. Many new roundabouts have angles like this (the one above in Carmel has it for the right turns), but the real issue is when peds are crossing the exit legs.

It is definitely easy to understate the importance of basic geometry decisions on driver behavior, e.g. pedestrian yield rates. Putting multilane monstrosities aside, look at the Dutch (https://i.imgur.com/ykQbvZe.png) best practice for roundabout geometry compared to the FHWA (https://i.imgur.com/qUSzal9.png) best practice, which would be considered unacceptable in the Netherlands.

The radial Dutch design uses just as sharp an angle for exits as in does for entrances, where the more tangential American design prioritizes maximum exit speed. Add raised crosswalks to the Dutch design and you will get excellent safety results anywhere, regardless of pedestrian volumes.

You're comparing apples with oranges in many aspects. Dutch structure is an old-style traffic circle, FHWA is more like what we call "modern roundabout".
Those "modern" ones are seriously optimized for vehicle throughput - well, at a cost for other users.
Now second apple to orange comparison is Dutch to US.
Not sure where dutch example would be located, likely a street with 40 km/h speed limit and 2-3k daily traffic.  US example is likely on a minor arterial with 10k+ traffic count and 45-50 MPH speeds, and throttling that street with Dutch style feature would kill the commute flow.
There is a lot one can say about general traffic architecture in US, but moral of the story is that dutch-style circles are appropriate where 2-way stop or simple 2-phase traffic light would work fine.
Extending the concept of circle to higher volumes, beyond the usable range, is the key problem. But looks like its a much deeper problem with traffic engineering workforce in US.  So it wouldn't be any better until it becomes much worse.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 11, 2018, 06:51:40 PM
Even the Dutch provide multi-lane roundabouts with right-angle entries: https://goo.gl/6bQDGN. They do prefer signals though.

I don't necessarily see how these are worse than American roundabouts. They slow the speed of entering vehicles but could seriously improve crosswalk obedience.

(https://i.imgur.com/4yaL90U.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 12, 2018, 01:24:05 PM
the real issue is when peds are crossing the exit legs.

That sums up what I was getting at.  For a stoplight or STOP-controlled intersection with slip lanes, there is no "exit leg" crosswalk because both entry and exit leg crossings are combined into one.  kalvado seems to have missed that I was generally agreeing with him about that, but it's probably because I was so wordy.

One solution to that is to use mid-block crosswalks near roundabouts rather than crosswalks nearer the roundabout.  However, assuming that pedestrians will walk half a block to cross a street when no actual law prohibits them from doing so nearer the roundabout is... unrealistic and would require fencing.  (The states whose laws I'm familiar with only prohibit crossing the street outside of crosswalks if there is a stoplight within a block of that location.)
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on October 12, 2018, 01:32:19 PM
the real issue is when peds are crossing the exit legs.

That sums up what I was getting at.  For a stoplight or STOP-controlled intersection with slip lanes, there is no "exit leg" crosswalk because both entry and exit leg crossings are combined into one.  kalvado seems to have missed that I was generally agreeing with him about that, but it's probably because I was so wordy.

One solution to that is to use mid-block crosswalks near roundabouts rather than crosswalks nearer the roundabout.  However, assuming that pedestrians will walk half a block to cross a street when no actual law prohibits them from doing so nearer the roundabout is... unrealistic and would require fencing.  (The states whose laws I'm familiar with only prohibit crossing the street outside of crosswalks if there is a stoplight within a block of that location.)

Many people are going to walk wherever they feel like walking.  Fencing definitely helps prevent people from walking where they shouldn't.

You mention will pedestrians walk a half-block to the midblock crosswalk.  Well, let's look at it another way: They're probably already walking down the block towards the roundabout, so they're going to pass that crosswalk enroute.  It may actually be more convenient for them. Or, maybe they have to walk past that one, around the corner, go a half block, and then cross at the next one because they were walking straight to the next block.  It pretty much depends where their origin and destination is as to whether the midblock crosswalk is more or less convenient.

Whenever I read about a ped accident in the news I wonder about that.  If they crossed away from the light, often times people say that the crosswalk is too far away and there's too few intersections.  But...if the jaywalker had passed the intersection, or would be passing the intersection anyway, then it's a moot point because the jaywalker wasn't taking a shortcut...he/she was just crossing where he/she shouldn't have been crossing in the first place.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 12, 2018, 01:55:59 PM
Many people are going to walk wherever they feel like walking.  Fencing definitely helps prevent people from walking where they shouldn't.

You mention will pedestrians walk a half-block to the midblock crosswalk.  Well, let's look at it another way: They're probably already walking down the block towards the roundabout, so they're going to pass that crosswalk enroute.  It may actually be more convenient for them. Or, maybe they have to walk past that one, around the corner, go a half block, and then cross at the next one because they were walking straight to the next block.  It pretty much depends where their origin and destination is as to whether the midblock crosswalk is more or less convenient.

Whenever I read about a ped accident in the news I wonder about that.  If they crossed away from the light, often times people say that the crosswalk is too far away and there's too few intersections.  But...if the jaywalker had passed the intersection, or would be passing the intersection anyway, then it's a moot point because the jaywalker wasn't taking a shortcut...he/she was just crossing where he/she shouldn't have been crossing in the first place.

If I'm simply walking down the street for a mile, and there's a roundabout along my path, then I sure won't feel like walking a half-block out of my way to a crosswalk, then a half-block  back again just to pick up my original course.

↓↓  Like hell I'm going to walk the path shown below if I've got a train to catch.  ↓↓

(https://i.imgur.com/fmJXKhX.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 12, 2018, 03:04:26 PM
The number one traffic congested area in Brown County, Wisconsin is the roundabout on the east side of the Claude Allouez bridge in De Pere.   This federally mandated study into congestion found that the De Pere roundabout was the biggest problem for motorists back in 2013.  The roundabout was originally constructed as a 2x2 roundabout in 2007 but was reconfigured and had a circulating lane removed back in August, 2012.  Crashes did go down… from 89 between 2007-2009 to 45 between 2013-2015... but now congestion is a problem.  There’s really no fix... add more lanes to the roundabout and you have an excessive number of crashes… take lanes out and you have excessive congestion.
 
FOX 11 Investigates: Traffic congestion in Brown County
https://fox11online.com/news/fox-11-investigates/fox11-investigates-traffic-congestion-in-brown-county
Title: Re: Crash prone 'modern roundabouts'
Post by: NoGoodNamesAvailable on October 12, 2018, 04:09:13 PM
Whenever I read about a ped accident in the news I wonder about that.  If they crossed away from the light, often times people say that the crosswalk is too far away and there's too few intersections.  But...if the jaywalker had passed the intersection, or would be passing the intersection anyway, then it's a moot point because the jaywalker wasn't taking a shortcut...he/she was just crossing where he/she shouldn't have been crossing in the first place.

There are thousands of sections of arterial highways in dense areas of the US with mile-long or greater distances between marked crosswalks; i.e., a pedestrian in the middle of this section would have to make a .5 mile or ~20 minute detour each way to get to the direct opposite side of the highway using marked crosswalks. It is not an uncommon sight in the least to see housing developments and grocery stores (or really usually convenience stores in food deserts) divided this way.

Could you imagine if we routinely forced drivers to make a similarly inconvenient detour for short trips like this for a tiny improvement in service for other modes? Keep in mind, not only are pedestrians inconvenienced by the increased trip distance, but they are actually put in danger when they are forced to cross many times more side streets and driveways than they would have to if a more direct route were available.

Walking should be the most convenient for short trips, not the least.

"Jaywalker" is also an imprecise and legally meaningless term that is easily thrown around by police departments and local media to shift blame onto the pedestrian. We frequently hear people who cross midblock or outside marked crosswalks called "jaywalkers," where these actions are usually completely legal, and in the case of unmarked crosswalks, where pedestrians actually have the right of way.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 12, 2018, 04:44:36 PM
You mention will pedestrians walk a half-block to the midblock crosswalk.  Well, let's look at it another way: They're probably already walking down the block towards the roundabout, so they're going to pass that crosswalk enroute.  It may actually be more convenient for them. Or, maybe they have to walk past that one, around the corner, go a half block, and then cross at the next one because they were walking straight to the next block.  It pretty much depends where their origin and destination is as to whether the midblock crosswalk is more or less convenient.

There are thousands of sections of arterial highways in dense areas of the US with mile-long or greater distances between marked crosswalks; i.e., a pedestrian in the middle of this section would have to make a .5 mile or ~20 minute detour each way to get to the direct opposite side of the highway using marked crosswalks. It is not an uncommon sight in the least to see housing developments and grocery stores (or really usually convenience stores in food deserts) divided this way.

Could you imagine if we routinely forced drivers to make a similarly inconvenient detour for short trips like this for a tiny improvement in service for other modes? Keep in mind, not only are pedestrians inconvenienced by the increased trip distance, but they are actually put in danger when they are forced to cross many times more side streets and driveways than they would have to if a more direct route were available.

Walking should be the most convenient for short trips, not the least.

I'm still trying to picture an example of how a mid-block crosswalk could be more convenient than one at the intersection itself.  Other than, of course, merely crossing the street mid-block (say from a restaurant to a laundromat across the street).  In my thinking, any walking trajectory either straight through or turning at an intersection would either be more convenient with the crosswalk as near the intersection as possible or else not affected by its placement.

If I'm going straight through and staying on my side of the street, then a mid-block crossing point to the right of the intersection is less convenient:  a total of one extra block I have to walk.  If I'm going straight through and then crossing to the other side of my street later, then it's just as inconvenient.

If I'm turning right and staying on my side of that street, then my route is not affected at all.  If I'm turning right and then crossing to the other side of that street later, then the location of the crosswalk doesn't affect me:  I have to cross the street at some point anyway.

If I'm turning left and staying on my side of that street, then I have to know in advance to cross the first street a half-block early but my route is otherwise unaffected.  If I'm turning left and then crossing to the other side of that street later, then I still have to know in advance to cross the first street a half-block early but then the location of the second crosswalk doesn't affect me:  I have to cross the street at some point anyway.



Whenever I read about a ped accident in the news I wonder about that.  If they crossed away from the light, often times people say that the crosswalk is too far away and there's too few intersections.  But...if the jaywalker had passed the intersection, or would be passing the intersection anyway, then it's a moot point because the jaywalker wasn't taking a shortcut...he/she was just crossing where he/she shouldn't have been crossing in the first place.

"Jaywalker" is also an imprecise and legally meaningless term that is easily thrown around by police departments and local media to shift blame onto the pedestrian. We frequently hear people who cross midblock or outside marked crosswalks called "jaywalkers," where these actions are usually completely legal, and in the case of unmarked crosswalks, where pedestrians actually have the right of way.

For reference, here is what the Uniform Vehicle Code says on the matter.  (Not all states use the UVC wording, including jeffandnicole's state, but many states do.)

Quote from: Millennium Edition of the Uniform Vehicle Code
§ 11-503–Crossing at other than crosswalks

(c) Between adjacent intersections at which traffic-control signals are in operation pedestrians shall not cross at any place except in a marked crosswalk.

In NJ, I don't even see such a restriction codified at all:  just that you have to use the crosswalk if there is one, nothing mentioned about proximity.  It's possible I missed something.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 12, 2018, 05:11:29 PM

In NJ, I don't even see such a restriction codified at all:  just that you have to use the crosswalk if there is one, nothing mentioned about proximity.  It's possible I missed something.
https://law.justia.com/codes/new-jersey/2013/title-39/section-39-4-33/
https://law.justia.com/codes/new-jersey/2013/title-39/section-39-4-34/
https://law.justia.com/codes/new-jersey/2013/title-39/section-39-4-36/
Something similar to NY. Right of way within crosswalk, yield to vehicles elsewhere - but otherwise cross anywhere except if explicitly prohibited.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 12, 2018, 05:26:53 PM
WSDOT is installing ramp meters at the Steptoe roundabout in Richland. Instead of HAWK signals like those in Carmel, these will be traditional ramp meter signals.

it's only a matter of time before we have four lane signalized roundabouts.

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 12, 2018, 05:36:33 PM
the real issue is when peds are crossing the exit legs.

That sums up what I was getting at.  For a stoplight or STOP-controlled intersection with slip lanes, there is no "exit leg" crosswalk because both entry and exit leg crossings are combined into one.  kalvado seems to have missed that I was generally agreeing with him about that, but it's probably because I was so wordy.

One solution to that is to use mid-block crosswalks near roundabouts rather than crosswalks nearer the roundabout.  However, assuming that pedestrians will walk half a block to cross a street when no actual law prohibits them from doing so nearer the roundabout is... unrealistic and would require fencing.  (The states whose laws I'm familiar with only prohibit crossing the street outside of crosswalks if there is a stoplight within a block of that location.)
I really misunderstood you, sorry about that. Doesn't change my reply too much, though. I am trying to talk facts, not personal arguments. :bigass:

Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 12, 2018, 06:07:36 PM
Yeah, I was too lazy to actually post the codes.  Thanks for linking to them.

https://law.justia.com/codes/new-jersey/2013/title-39/section-39-4-33/
First two words:  "At intersections".
Does not apply to crossing the street mid-block.

https://law.justia.com/codes/new-jersey/2013/title-39/section-39-4-34/
Specifically states:  "in the absence of a crosswalk, and where not otherwise prohibited, at right angles to the roadway."
As long as you don't cross diagonally, then does not apply to crossing mid-block.

https://law.justia.com/codes/new-jersey/2013/title-39/section-39-4-36/
Laws pertaining to drivers, not to pedestrians.

Right of way within crosswalk, yield to vehicles elsewhere - but otherwise cross anywhere except if explicitly prohibited.

Precisely.



it's only a matter of time before we have four lane signalized roundabouts.

ick!
Title: Re: Crash prone 'modern roundabouts'
Post by: johndoe on October 12, 2018, 08:36:11 PM
WSDOT is installing ramp meters at the Steptoe roundabout in Richland.

In the Google imagery you can tell they used to have multilane approaches: https://goo.gl/maps/vNEEKYYPKgM2
Sure enough: https://www.tri-cityherald.com/latest-news/article32210604.html
http://www.au2pb.com/steptoe/


I wonder if the queue reached the freeway with two westbound lanes. Interesting the DOT decided to meter it rather than any other multilane option (different signs, markings, speed table).

Also interesting that the movement from westbound Columbia Park Trail to eastbound 240 has required a lane change in both striping layouts....not a fan of that.  I wonder why they didn't stripe the westbound lane to the left rather than right circulating lane.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 12, 2018, 08:52:48 PM
WSDOT is installing ramp meters at the Steptoe roundabout in Richland.

In the Google imagery you can tell they used to have multilane approaches: https://goo.gl/maps/vNEEKYYPKgM2
Sure enough: https://www.tri-cityherald.com/latest-news/article32210604.html
http://www.au2pb.com/steptoe/

I wonder if the queue reached the freeway with two westbound lanes. Interesting the DOT decided to meter it rather than any other multilane option (different signs, markings, speed table).

It's one of only a couple roundabouts in WA where lane modifications have taken place. The Steptoe Roundabout has gone through three (maybe four) changes to its markings. I guess they got fed up. Lots of collisions, apparently.

I am wondering if the single lane approach makes it so there's a near-constant flow of cars from the east, rather than two or four at a time with two lanes. The occasional breaks would have made it easier for traffic from 240 to enter the roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 13, 2018, 01:52:38 AM
Yeah, I was too lazy to actually post the codes.  Thanks for linking to them.

https://law.justia.com/codes/new-jersey/2013/title-39/section-39-4-33/
First two words:  "At intersections".
Does not apply to crossing the street mid-block.

https://law.justia.com/codes/new-jersey/2013/title-39/section-39-4-34/
Specifically states:  "in the absence of a crosswalk, and where not otherwise prohibited, at right angles to the roadway."
As long as you don't cross diagonally, then does not apply to crossing mid-block.

https://law.justia.com/codes/new-jersey/2013/title-39/section-39-4-36/
Laws pertaining to drivers, not to pedestrians.

Right of way within crosswalk, yield to vehicles elsewhere - but otherwise cross anywhere except if explicitly prohibited.

Precisely.


Problem is, that on one hand pedestrians are a part of traffic flow with well-defined rights and responsibilities; but on the other hand, they are rarely, if ever, held responsible for ignoring those responsibilities. 
Jaywalking - as in crossing outside marked or unmarked crosswalk - but press (often) and insurance (always) consider vehicle-pedestrian accidents outside crosswalk as driver's responsibility. Since there is normally no criminal charges for accidents where drivers act in good faith, that pretty much means the concept of right of way is non-existent for pedestrians.
I do see some good reasons for that, considering person outside crosswalk as an open season game is a bad idea. But sometimes I feel things are going too far.

Back to roundabouts: there are some nice examples in posts above with grade-separated walkways, either to the center island or under the arms of roundabout. Rainwater drainage is, apparently, one of the technical problems which can be dealt with. However, I was told - on multiple occasions! - that US public is unable to deal with underground crosswalks until there is an armed cop stationed there 24/7...
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 14, 2018, 04:06:04 PM
Back to roundabouts: there are some nice examples in posts above with grade-separated walkways, either to the center island or under the arms of roundabout. Rainwater drainage is, apparently, one of the technical problems which can be dealt with. However, I was told - on multiple occasions! - that US public is unable to deal with underground crosswalks until there is an armed cop stationed there 24/7...

The underground passageways I've used could be made a LOT more inviting with better lighting and maybe some art along the walls.  But bare concrete with cobwebbed dingy lights or no lights at all is more common: not exactly what inspires confidence in your personal security.  Interestingly, my mother was once assaulted on a pedestrian overpass back in the 1970s on her way to work.  It was this one over I-64. (https://goo.gl/maps/unNvRGGcJBr)  She fought him off with her purse.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 14, 2018, 05:13:15 PM
Back to roundabouts: there are some nice examples in posts above with grade-separated walkways, either to the center island or under the arms of roundabout. Rainwater drainage is, apparently, one of the technical problems which can be dealt with. However, I was told - on multiple occasions! - that US public is unable to deal with underground crosswalks until there is an armed cop stationed there 24/7...

The underground passageways I've used could be made a LOT more inviting with better lighting and maybe some art along the walls.  But bare concrete with cobwebbed dingy lights or no lights at all is more common: not exactly what inspires confidence in your personal security.  Interestingly, my mother was once assaulted on a pedestrian overpass back in the 1970s on her way to work.  It was this one over I-64. (https://goo.gl/maps/unNvRGGcJBr)  She fought him off with her purse.
A vicious circle - they are not used because they are scary, and once they are not used - they grow scary, including higher risk of meeting with someone with bad intentions.
Punishing ADA requirements really don't help the case.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 14, 2018, 05:19:22 PM
Back to roundabouts: there are some nice examples in posts above with grade-separated walkways, either to the center island or under the arms of roundabout. Rainwater drainage is, apparently, one of the technical problems which can be dealt with. However, I was told - on multiple occasions! - that US public is unable to deal with underground crosswalks until there is an armed cop stationed there 24/7...

The underground passageways I've used could be made a LOT more inviting with better lighting and maybe some art along the walls.  But bare concrete with cobwebbed dingy lights or no lights at all is more common: not exactly what inspires confidence in your personal security.  Interestingly, my mother was once assaulted on a pedestrian overpass back in the 1970s on her way to work.  It was this one over I-64. (https://goo.gl/maps/unNvRGGcJBr)  She fought him off with her purse.

A vicious circle - they are not used because they are scary, and once they are not used - they grow scary, including higher risk of meeting with someone with bad intentions.
Punishing ADA requirements really don't help the case.

Lighting and width are key. Both are problems with modern attempts. Even Dutch underpasses are too narrow, and they're probably the best around.

That I-64 overpass shows exactly why overpasses are not always better. They usually require massive fences to prevent jumping and throwing, and always end up too narrow, more than likely due to budget constraints. Underpasses that are wide are really the best option, although wide pedestrian overpasses are okay too. If it's a freeway, an overpass is really the only option (not enough light seepage for an underpass, even a wide one), so making it wide and/or using a bit more glass are options.
Title: Re: Crash prone 'modern roundabouts'
Post by: mrsman on October 14, 2018, 08:43:29 PM
From the previous page, this looks incredibly dangerous.

A pedestrian standing at the star needs to monitor 4 lanes of traffic before they can cross safely. Worse, the drivers at 1 and 2 will be looking only left and will take the first clear slot the accelerate straight into the crosswalk before confirming it is clear.

The crosswalk with the arrow has a triple threat, and the straight exit means vehicles will be accelerating quickly out of the circle.

Worse, the roundabout is designed so bicyclists exit the lane and use the crosswalks (note the ramps). Thats incredibly dangerous at the speeds this is designed for.

Incredibly irresponsible design.

(https://i.imgur.com/f7Y3jLB.jpg)

WIth many of these larger roundabouts, especially the one pictured above, there seems to be little merging and instead very dangerous crossing.  Assuming the top left corner is north, the northbound 2 lanes intersect the 3 eastbound lanes, make a slight bend around and then intersect the two westbound lanes before continuing out of the roundabout.  Essentially, 2 uncontrolled intersections face every thru direction.  Extremely dangerous.

The situation reminds me of Scott Circle in DC.  Ignoring 16th street which goes underneath the circle, you have Mass Ave and RI Ave meeting in the circle, but the circle is so elongated that it is as though the two streams of streets meet at near-right angles, signalized intersections.  While the extra traffic signals do cause delay, at least there is no need to provide left turn phasing and the signals do increase safety.  The current layout is probably about equal in delay to a 6-point signalized intersection that you'd commonly see in Chicago.

https://www.google.com/maps/place/Scott+Cir+NW,+Washington,+DC/@38.907165,-77.0364776,18z/data=!4m5!3m4!1s0x89b7b7c0896e870b:0xf7c64d55f17ac8e3!8m2!3d38.9070139!4d-77.0365426

I am extremely worried about these multilane circles and roundabouts without traffic direction.  There does not seem to be any control and just letting drivers do what they want is chaotic.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 15, 2018, 01:35:41 PM
WIth many of these larger roundabouts, especially the one pictured above, there seems to be little merging and instead very dangerous crossing.  Assuming the top left corner is north, the northbound 2 lanes intersect the 3 eastbound lanes, make a slight bend around and then intersect the two westbound lanes before continuing out of the roundabout.  Essentially, 2 uncontrolled intersections face every thru direction.  Extremely dangerous.

This is a problem inherent in the design of a multi-lane roundabout.  No amount of flaring the lanes or expanding the circle will eliminate the conflict points.  The key reason given for roundabouts' reduction in collision severity is that it substitutes side-swipe accidents for T-bone accidents.  With multi-lane roundabouts, however, some of the T-bone possibility remains, except that the angle of collision is reduced somewhat.

See my post below:

Though multi-lane roundabouts can be annoying due to driver ignorance and hesitation, I fail to see how they are, functionally, any different from a standard one-lane roundabout.

I used to think that too.  However, I figured out a functional difference several months ago.  All of a single-lane roundabout's conflict points are side-swipe, the result of merging into a lane where there's already a car.  However, in a multi-lane roundabout, straight-through traffic can actually conflict in a more catastrophic way.

In order to avoid the green star conflict point illustrated below, the right lane of the approaches would need to be right-turn-only–effectively making it a single-lane roundabout with slip lanes.

(https://i.imgur.com/SLCiqgK.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on October 15, 2018, 02:13:35 PM

Assuming the top left corner is north, ...

The top left corner is east.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 15, 2018, 02:56:44 PM
In order to avoid the green star conflict point illustrated below, the right lane of the approaches would need to be right-turn-only–effectively making it a single-lane roundabout with slip lanes.

https://i.imgur.com/SLCiqgK.png

It could remain as-is. Many multi-lane "modern roundabouts" have this path overlap issue, it just requires drivers to be aware of the origin of the vehicles around them. The blue line should have recognized that the red line entered from a different point, so the red line won't necessarily keep going around. If drivers stagger their positioning in a roundabout, there would be less chance for conflict. But that's asking a lot.

Of course, this puts great trust in drivers, and lacking that trust, we usually avoid path overlap. But a lot of countries do design roundabouts with path overlaps, intentionally or otherwise. This eastbound movement (https://goo.gl/nCiozj) in Melbourne, Australia, for example. Many roundabouts in the UK feature "path overlap" in the strictest sense, but they usually don't have lane markings, so nobody assumes anything.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 15, 2018, 02:58:43 PM
Many multi-lane "modern roundabouts" have this path overlap issue

My point was that all multi-lane roundabouts have path overlap.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on October 15, 2018, 03:27:45 PM
From the previous page, this looks incredibly dangerous.

A pedestrian standing at the star needs to monitor 4 lanes of traffic before they can cross safely. Worse, the drivers at 1 and 2 will be looking only left and will take the first clear slot the accelerate straight into the crosswalk before confirming it is clear.

The crosswalk with the arrow has a triple threat, and the straight exit means vehicles will be accelerating quickly out of the circle.

Worse, the roundabout is designed so bicyclists exit the lane and use the crosswalks (note the ramps). Thats incredibly dangerous at the speeds this is designed for.

Incredibly irresponsible design.

(https://i.imgur.com/f7Y3jLB.jpg)

WIth many of these larger roundabouts, especially the one pictured above, there seems to be little merging and instead very dangerous crossing.  Assuming the top left corner is north, the northbound 2 lanes intersect the 3 eastbound lanes, make a slight bend around and then intersect the two westbound lanes before continuing out of the roundabout.  Essentially, 2 uncontrolled intersections face every thru direction.  Extremely dangerous.

The situation reminds me of Scott Circle in DC.  Ignoring 16th street which goes underneath the circle, you have Mass Ave and RI Ave meeting in the circle, but the circle is so elongated that it is as though the two streams of streets meet at near-right angles, signalized intersections.  While the extra traffic signals do cause delay, at least there is no need to provide left turn phasing and the signals do increase safety.  The current layout is probably about equal in delay to a 6-point signalized intersection that you'd commonly see in Chicago.

https://www.google.com/maps/place/Scott+Cir+NW,+Washington,+DC/@38.907165,-77.0364776,18z/data=!4m5!3m4!1s0x89b7b7c0896e870b:0xf7c64d55f17ac8e3!8m2!3d38.9070139!4d-77.0365426

I am extremely worried about these multilane circles and roundabouts without traffic direction.  There does not seem to be any control and just letting drivers do what they want is chaotic.

Very good point.

By making the exits a straight-through movement, youre getting very close to creating a t-bone scenario. This is in contrast to the Dutch model where exiting vehicles are turning left then right, thus allowing more of a sideswipe.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 15, 2018, 03:36:06 PM
Many multi-lane "modern roundabouts" have this path overlap issue

My point was that all multi-lane roundabouts have path overlap.

Path overlap technically only exists when drivers are required to follow an invisible line after entering the roundabout, in order to go straight or turn right. Roundabout markings help guide traffic out of roundabouts, not into them, so most roundabouts are designed so that entering traffic does not need to turn their steering wheel to cross over the path of exiting traffic.

In the image above, the entries don't require traffic to do anything except except proceed straight across the path of exiting traffic. At the intersection below, the entrances from the top-bottom have very little path overlap, but the left-right entries have a massive path overlap (so they have to follow their own invisible line around the roundabout, not the one painted on the ground, which is for traffic that is exiting -- yes that's confusing).

(https://i.imgur.com/BEnSScs.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on October 15, 2018, 03:45:49 PM
Behold the Infinitybout! https://www.google.com/maps/@41.2744657,-95.9903372,194m/data=!3m1!1e3
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 15, 2018, 04:49:27 PM
Many multi-lane "modern roundabouts" have this path overlap issue

My point was that all multi-lane roundabouts have path overlap.

Path overlap technically only exists when drivers are required to follow an invisible line after entering the roundabout, in order to go straight or turn right. Roundabout markings help guide traffic out of roundabouts, not into them, so most roundabouts are designed so that entering traffic does not need to turn their steering wheel to cross over the path of exiting traffic.

In the image above, the entries don't require traffic to do anything except except proceed straight across the path of exiting traffic. At the intersection below, the entrances from the top-bottom have very little path overlap, but the left-right entries have a massive path overlap (so they have to follow their own invisible line around the roundabout, not the one painted on the ground, which is for traffic that is exiting -- yes that's confusing).

(https://i.imgur.com/BEnSScs.png)

Sorry, I must have misunderstood what you meant by "overlap."
What I mean to say is that all mutli-lane roundabouts have paths that cross each other, not just paths that merge and diverge.

By my count, at a typical double-lane roundabout, left turning traffic crosses paths (not just merges or diverges) with four separate lane movements.
In the roundabout below, red traffic coming from the left crosses paths at the four triangles.

(https://i.imgur.com/AGlBYQc.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 15, 2018, 05:18:57 PM

What I mean to say is that all mutli-lane roundabouts have paths that cross each other, not just paths that merge and diverge.

By my count, at a typical double-lane roundabout, left turning traffic crosses paths (not just merges or diverges) with four separate lane movements.
In the roundabout below, red traffic coming from the left crosses paths at the four triangles.

(https://i.imgur.com/AGlBYQc.png)
And here is a standard "roundabout is better - it has less conflict points" pic:
(https://nextstl.com/wp-content/uploads/9577583353_3c13fe8144_o-1.jpg)
Roundabouts are sold as having single merge/diverge point... Which is a bit dishonest from my perspective.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 15, 2018, 08:13:41 PM
And here is a standard "roundabout is better - it has less conflict points" pic:
(https://nextstl.com/wp-content/uploads/9577583353_3c13fe8144_o-1.jpg)
Roundabouts are sold as having single merge/diverge point... Which is a bit dishonest from my perspective.

Roundabouts do approach that ideal if they are single-lane roundabouts.  Once you start adding lanes, it gets a whole lot messier wrt conflict points.  I'm convinced this has something to do with the heretofore unexpectedly high number of accidents at multi-lane roundabouts that tradephoric has so dogmatically highlighted throughout the life of this thread.

(There have now been more replies to this thread than years since B.C.)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 18, 2018, 10:35:56 AM
The SR 161 / Riverside intersection averaged 20 crashes per year before a roundabout was constructed in 2016.  When a complex triple-lane roundabout was being proposed, Jeannie Willis (engineering manager for the City of Dublin) said that the roundabout would reduce crashes.
Quote
https://vimeo.com/127607639
“They improve safety.  We will reduce crashes.  It won’t eliminate crashes.  The frequency of the crashes will be reduced and the severity will be reduced, of the crashes, meaning the number of injury related type crashes will be substantially reduced.”

-Jeannie Willis, Engineering Manager, City of Dublin

Turns out the S.R.161/ Riverside Drive roundabout has averaged 2.5 crashes per week since the roundabout opened in August 2016.  That comes to 130 crashes/year compared to just 20 crashes/year before the roundabout.  That’s over a 6X increase in crashes.  This upcoming weekend the roundabout will be closed as the city makes changes and eliminates a circulating lane in the roundabout to simplify operations.  This is what Jeannie Willis is saying about the proposed changes.

Quote
"We do anticipate that the decision making for our drivers will get simpler and easier, which should help ease that confusion approaching the intersection… this will improve safety, help improve traffic operations and make the roundabout a little simpler for our northbound drivers,”

-Jeannie Willis, Engineering Manager, City of Dublin
 
https://abc6onyourside.com/news/local/changes-coming-to-dublin-roundabout-after-several-crashes

I hate to harp on Jeannie Willis, but she hasn’t been effective at anticipating crash rates at this intersection in the past.  Will Jeannie Willis claim that the changes are a success if crashes drop from 130 crashes/year down to 80 crashes/year?  She might, but considering that there was only 20 crashes/year before the roundabout was built, crashes have a LONG way to drop to return to pre-roundabout levels.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 18, 2018, 07:28:47 PM
The 121st roundabout just opened in Carmel at Carmel Drive and Old Meridian Road.  The city posted a youtube video of the grand opening and i decided to leave a comment.  We will see if the City can answer my request or if they just delete the comment.

Quote
Three people have been killed at the 96th and Westfield Blvd roundabout in Carmel over a 10 year period (2 killed on October 1, 2007 and 1 killed on March 17, 2016).  Has there been a signalized intersection in Carmel that has had 3 fatalities over a 10 year period?  I don't care if you got to go back to the 1970s to cite an example... just cite one signalized intersection in Carmel that has had 3 fatalities over a 10 year period.

 
Title: Re: Crash prone 'modern roundabouts'
Post by: mrsman on October 18, 2018, 08:11:21 PM
And here is a standard "roundabout is better - it has less conflict points" pic:
(https://nextstl.com/wp-content/uploads/9577583353_3c13fe8144_o-1.jpg)
Roundabouts are sold as having single merge/diverge point... Which is a bit dishonest from my perspective.

Roundabouts do approach that ideal if they are single-lane roundabouts.  Once you start adding lanes, it gets a whole lot messier wrt conflict points.  I'm convinced this has something to do with the heretofore unexpectedly high number of accidents at multi-lane roundabouts that tradephoric has so dogmatically highlighted throughout the life of this thread.

(There have now been more replies to this thread than years since B.C.)
I agree.  Just like 4 way stops, they work fine in low traffic, but break down in high traffic.  A signal or grade separation is necessary.

Nexus 5X

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 18, 2018, 08:12:37 PM
The 121st roundabout just opened in Carmel at Carmel Drive and Old Meridian Road.  The city posted a youtube video of the grand opening and i decided to leave a comment.  We will see if the City can answer my request or if they just delete the comment.

They won't delete it but they won't answer it. You'd be better off emailing the city or mayor directly.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 19, 2018, 08:59:42 PM

Remember this roundabout being proposed for I-35 and 51st Street in Austin?  Well the roundabout fully opened to traffic on June 14, 2018 and TxDOT released a video showing traffic circulating the new circle.  On August 1, 2018 TxDOT released another video of the roundabout in action and it appears that it has already been downsized from a 3x2 roundabout to a 2x2 roundabout (the spiral inner lane has been striped out).  I couldn't find any articles explaining why the roundabout was restriped but here are the videos TxDOT released:


Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 20, 2018, 12:05:01 AM

Remember this roundabout being proposed for I-35 and 51st Street in Austin?  Well the roundabout fully opened to traffic on June 14, 2018 and TxDOT released a video showing traffic circulating the new circle.  On August 1, 2018 TxDOT released another video of the roundabout in action and it appears that it has already been downsized from a 3x2 roundabout to a 2x2 roundabout (the spiral inner lane has been striped out).  I couldn't find any articles explaining why the roundabout was restriped but here are the videos TxDOT released:



Interesting that they used used edge markings across that single-lane exit leg on the right. I've only seen that at this roundabout in Federal Way, WA: https://goo.gl/gsYTM9

As it exists now, the right lane to the approach is useless to do anything besides re-enter the frontage road. Which is odd, since they built a ramp for that already. At least before, the two lanes could go left at the roundabout. Now it's, effectively, a single-lane approach.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on October 22, 2018, 05:11:38 PM

Remember this roundabout being proposed for I-35 and 51st Street in Austin?  Well the roundabout fully opened to traffic on June 14, 2018 and TxDOT released a video showing traffic circulating the new circle.  On August 1, 2018 TxDOT released another video of the roundabout in action and it appears that it has already been downsized from a 3x2 roundabout to a 2x2 roundabout (the spiral inner lane has been striped out).  I couldn't find any articles explaining why the roundabout was restriped but here are the videos TxDOT released:



Every driver in the first video is using that 3rd lane incorrectly, so it makes a lot of sense that they killed it.

Crosswalks look good too. This is an example of a good roundabout Id say
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 22, 2018, 05:54:09 PM
^I personally don't foresee a high crash rage at that roundabout especially now that they removed that 3rd lane.  The benefit of the way they got it striped is that trucks can use that pavement area as a truck apron and drivers won't be forced to hop the curbing with their trailer... making it less likely you will see a truck tip-over at this roundabout.  Also interchange roundabouts naturally have simpler turning movements.  If you are exiting the freeway waiting to enter the roundabout, you know that any driver circulating the roundabout is going to continue circulating around it (since drivers can't exit the roundabout at that off-ramp leg... it's one-way).  This prevents the scenario where someone pulls out into the roundabout mistakenly believing that a circulating vehicle was about to exit the roundabout.   In addition, the leg servicing the freeway on-ramp has no drivers entering the roundabout... they can only exit on that leg greatly simplifying operations.  Really high crash rates just aren't seen at interchange roundabout very often (unless if there's some complexity involved like a service drive incorporated into the roundabout design). 

The only thing i don't like about the design is there is a damn retaining wall in the central island.  That wall could easily lead to a fatal crash if someone attempts to blow through the circle at high speed (this picture was obviously taken before the 3rd lane was striped out).  I would not be surprised if in a few years i'm posting a picture of a vehicle that plowed through that retaining wall...
(https://www.txdot.gov/content/dam/txdot/asset_collection/inside-txdot/media-room/news-release/austin/015-2018/roundabout.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 22, 2018, 09:05:48 PM
I personally don't foresee a high crash rage at that roundabout

None of us knows how to respond to this......
Title: Re: Crash prone 'modern roundabouts'
Post by: Tonytone on October 22, 2018, 09:24:24 PM
https://www.google.com/maps/@39.5168107,-75.6803003,1135a,35y,39.2t/data=!3m1!1e3 (https://www.google.com/maps/@39.5168107,-75.6803003,1135a,35y,39.2t/data=!3m1!1e3)

How will these roundabouts do when heavy traffic occurs? I have drove thru these roundabouts while the highway is not done yet and it's a little tight IMO,
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 22, 2018, 11:08:57 PM
https://www.google.com/maps/@39.5168107,-75.6803003,1135a,35y,39.2t/data=!3m1!1e3 (https://www.google.com/maps/@39.5168107,-75.6803003,1135a,35y,39.2t/data=!3m1!1e3)

How will these roundabouts do when heavy traffic occurs? I have drove thru these roundabouts while the highway is not done yet and it's a little tight IMO,

Those roundabouts have central island diameters of roughly 110 feet.  That doesn't seem that tight as there are many examples of single-lane interchange roundabouts with smaller central island diameters.  For example here is a single-lane roundabout off I-64 near Saint Louis with a central island diameter of just 65 feet:

https://www.google.com/maps/@38.6254184,-90.1345388,64m/data=!3m1!1e3
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 22, 2018, 11:44:49 PM
^Apart from the RV blowing through the middle of that Worthington Minnesota roundabout, there has been two other pretty major events at the roundabout over the past couple weeks.

Tanker hauling cream overturns in Worthington roundabout
(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/111117.N.DG_.TANKERCREAM%20rgb_0.jpg?itok=rxMKiQ4I)
http://www.dglobe.com/news/accidents/4356792-tanker-hauling-cream-overturns-worthington-roundabout


These little piggies almost didn't make it to market when a Minn. hog truck rolled

(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/102817.N.DG_.ROLLOVER%203.jpg?itok=DOQatmVs)
http://www.agweek.com/news/4350581-these-little-piggies-almost-didnt-make-it-market-when-minn-hog-truck-rolled

Cream trucks rolling over, hogs running around the highway, some RV driver thinking they are Bo Duke... these roundabouts really give the good people of Worthington Minnesota something to talk about!


Another vehicle vaulted over the Worthington roundabout on Sunday.  The driver sustained non-life threatening injuries.  This comes a month after an RV was videotaped launching over the roundabout in early November.

Minivan vaults over roundabout Sunday
https://www.dglobe.com/news/accidents/4375814-minivan-vaults-over-roundabout-sunday

There have been 2 truck tip-over crashes, an RV flying through the middle of the roundabout captured on video, a driver sustaining non life-sustaining injuries after his min-van flew through the middle of the roundabout, and now 4 reported crashes over a few hour period on Friday.  The roundabouts are doing a stellar job at reducing crashes in Worthington.. or maybe they are doing a worthless job.

Snowpacked roundabouts result in four crashes reported Friday
https://www.dglobe.com/news/4380839-snowpacked-roundabouts-result-four-crashes-reported-friday

Yet another semi-rollover happened at the Worthington roundabout Friday morning.

A roundabout rollover
(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/072118.N.DG_.%20Round%20about%20roll%202%20web.jpg?itok=ia9BHMPT)
http://dglobe.com/news/accidents/4475427-roundabout-rollover

Another semi loses his load at the Worthington roundabout on Tuesday.  This is at least the 4th semi to tip over/lose their load since October, 2017. 

Spilled grain in Worthington roundabout
(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/073118.N.TG_.%20Semi%20roll%20over%20of%20the%20week%20web.jpg?itok=uZyr2Bsy)
http://www.dglobe.com/news/accidents/4479958-spilled-grain-worthington-roundabout

Another semi rolled over at a Worthington roundabout today (October 22, 2018).  One person was taken to the hospital with non-life threatening injuries.  In the past year there has been 5 documented cases of semi trucks tipping over/losing their load in Worthington roundabouts.  Maybe it's time for Worthington to consider ripping these roundabouts out as they just don't seem to be working out too well in their community!

Semi rollover in Worthington injures one
http://www.kkoj.com/news/local-news/semi-rollover-in-worthington-injures-one/
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 22, 2018, 11:49:50 PM
For example here is a single-lane roundabout off I-64 near Saint Louis with a central island diameter of just 65 feet:

https://www.google.com/maps/@38.6254184,-90.1345388,64m/data=!3m1!1e3

I can do you one slightly better. This new slightly-oval-ish roundabout in Kelso, WA with an average diameter of 63 feet: https://goo.gl/7sqJHC -- involves three separate freeway ramps.

There is also the Slater Road roundabouts in Ferndale, WA, built within the former grounds of the original freeway ramp terminii. Diameter of ~50-55 feet. They are mountable, near-mini roundabouts though: https://goo.gl/5oHxZQ

Both of these are actually quite nice because, in the event you miss them, you can mostly just sail right over them without hitting anything. Assuming you can maintain control after hitting a curb.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 23, 2018, 12:59:46 PM
average circumference

Never heard this term before.

Diameter 63 feet = ICD 20 feet
Am I doing my math right?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 23, 2018, 04:45:05 PM
average circumference

Never heard this term before.

Diameter 63 feet = ICD 20 feet
Am I doing my math right?

*average diameter. Sorry. :pan:
Title: Re: Crash prone 'modern roundabouts'
Post by: UCFKnights on October 29, 2018, 07:02:42 PM
So I was debating where to put this post, but Universal Orlando is building new theme parks and the roadway/drainage plans were just released, indicating 2 multi lane roundabouts are going to be built. This obviously will get a load of tourists, tons from out of country, who seem to barely be able to drive as is. Wanted to see what people thought of the 2 roundabouts. One of them is elevated, and only connects 2 roads with the rest of the turning movements being at a signalized intersection below the roundabout, and even includes a bypass ramp to avoid the roundabout in one direction, so a simple ramp would have done a better job for sure, but I guess they want to look fancy?

The other seems to be a more traditional multilane roundabout, here's the plans released so far:
(https://www.themeparkinsider.com/art/2018/universal_orlando_expansion_plan.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 29, 2018, 07:45:02 PM
That is a very strange elevated structure. Since it only appears to be for one direction, I'm not sure it needs that 3/4-circle look to it; need to see other bits of the plan to be sure.

I see that Universal isn't necessarily going full-Disney and building interchanges at every single node.
Title: Re: Crash prone 'modern roundabouts'
Post by: UCFKnights on October 29, 2018, 07:58:30 PM
Universal doesn't have enough land to do that, there campus has generally been the "urban" version of suburban Disney.

I found a zoomed in image of the "elevated roundabout" and it turns out its not a roundabout at all, just an unneccessarily roundabout shaped ramp where not even all of it is usable. I think the northeast corner of it might be for buses only. Looking for one of the normal roundabout in the plans as well.
(http://forums.insideuniversal.net/attachments/screen-shot-2018-10-29-at-12-08-47-pm-2-png.8283/)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 30, 2018, 12:58:15 PM
tourists, tons from out of country, who seem to barely be able to drive as is.

In my experience, Americans are generally the least capable drivers on the road.
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on October 30, 2018, 08:07:12 PM
tourists, tons from out of country, who seem to barely be able to drive as is.
In my experience, Americans are generally the least capable drivers on the road.

I'd say laziest, which isn't quite synonymous with least capable. It's not that American drivers can't keep right on freeways, they just don't. It's not that they can't figure out how roundabouts work most efficiently, they just don't bother. And so on. Our culture is one that encourages laziness and in no place is that more evident than on the road (IMO).
Title: Re: Crash prone 'modern roundabouts'
Post by: UCFKnights on October 30, 2018, 09:04:16 PM
tourists, tons from out of country, who seem to barely be able to drive as is.

In my experience, Americans are generally the least capable drivers on the road.
Perhaps its not entirely based on capability, but the signs and markings are different so their muscle memory will be "wrong". Plus urban American drivers surely have a very different style from rural drivers, which are different from international drivers, creating tons of confusion and a terrible situation.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 30, 2018, 09:41:32 PM
tourists, tons from out of country, who seem to barely be able to drive as is.

In my experience, Americans are generally the least capable drivers on the road.
Perhaps its not entirely based on capability, but the signs and markings are different so their muscle memory will be "wrong". Plus urban American drivers surely have a very different style from rural drivers, which are different from international drivers, creating tons of confusion and a terrible situation.

I'd agree. The lack of markings is definitely odd, especially compared to European countries. We rely heavily on signs, especially text-based ones, whereas Europeans will put a lot of stuff on the pavement (give way triangles, dashed lines for yielding or where to diverge or merge, destinations, etc). There's also right and left on red, which is definitely a foreign concept to everyone not from North America (and also really against all muscle memory). Being able to pass in any lane is also weird, as are the speed limits (usually too low); low limits are OK but seem odd when everyone is ignoring them.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 31, 2018, 12:49:00 PM
tourists, tons from out of country, who seem to barely be able to drive as is.

In my experience, Americans are generally the least capable drivers on the road.
Perhaps its not entirely based on capability, but the signs and markings are different so their muscle memory will be "wrong". Plus urban American drivers surely have a very different style from rural drivers, which are different from international drivers, creating tons of confusion and a terrible situation.

I'd agree. The lack of markings is definitely odd, especially compared to European countries. We rely heavily on signs, especially text-based ones, whereas Europeans will put a lot of stuff on the pavement (give way triangles, dashed lines for yielding or where to diverge or merge, destinations, etc). There's also right and left on red, which is definitely a foreign concept to everyone not from North America (and also really against all muscle memory). Being able to pass in any lane is also weird, as are the speed limits (usually too low); low limits are OK but seem odd when everyone is ignoring them.

American drivers disregard striping at a roundabout, or they flat out stop at one until there's nobody even remotely close to possibly heading towards them, because they are incapable of using common sense when confronted with something out of the ordinary.  Send an average American driver around the Arc d'Triomphe (which lacks striping, BTW) and it's a recipe for disaster.  I still maintain that foreign drivers are better equipped to handle unusual circumstances and make a good judgment call than we American drivers are.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 31, 2018, 02:44:14 PM
I was referring to all roads, not roundabouts. In fact, roundabouts are typically the most well striped of any intersection type in the country. Many new striping standards were introduced with roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on October 31, 2018, 03:33:02 PM
We do have very lazy striping standards in much of the US. Roundabouts are the exception. But in many areas lines just 'end' at intersections, only to resume on the other side.
Lane assignments often come with painted arrows in turning lanes but are blank for lanes where you continue straight ahead.
Some highway exit neutral zones are filled in with chevrons, many are not, who knows what the reason is from one example to the next.

Pixel 2

Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 31, 2018, 03:40:24 PM
My observation is based on drivers from both countries with better signage (Mexico) and striping standards than ours and those with worse standards (western Europe).
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on October 31, 2018, 07:37:19 PM
I still maintain that foreign drivers are better equipped to handle unusual circumstances and make a good judgment call than we American drivers are.

I actually fully agree, but that isn't because we're incapable. Rather, it's because of the abundance of rules and standards governing our road network mean there rarely is any unusual circumstances. That is to say, the average driver probably won't encounter anything on their commute today they didn't encounter yesterday. Which makes them a bit inattentive after a while. Not so much in other countries, where standards are more lax and you're expected to make decisions on the fly. We don't have to do that here, largely because of the higher standards and very well-established expectations (probably too much so - leading to perceived inability to handle unique situations).
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on November 08, 2018, 11:24:43 AM
Just came back from Amman, which is packed to the brim with roundabouts...

American drivers are angels and scholars
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 08, 2018, 12:59:36 PM
Just came back from Amman, which is packed to the brim with roundabouts...

American drivers are angels and scholars

Perfect addition to the discussion!
If you plopped 200 American drivers down in Amman, how many of them do you think would have a traffic accident within the first week?
That's what I mean by incapable.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 08, 2018, 01:20:19 PM
Just came back from Amman, which is packed to the brim with roundabouts...

American drivers are angels and scholars

Perfect addition to the discussion!
If you plopped 200 American drivers down in Amman, how many of them do you think would have a traffic accident within the first week?
That's what I mean by incapable.
If you plopped 200 off-the-street americans into an every day life of third world country, how many of them would make it till the end of the week? Doesn't make people incapable or unfit for life.

Jordan has 151 accident/year  per 100k vehicles vs 13 in US - about 12 times higher accident rate. Of course, NASCAR would have an even higher accident rate - and even more skilled drivers.. But for last  10 year I mostly drive to get from point A to point B in one piece...
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 08, 2018, 01:33:41 PM
Just came back from Amman, which is packed to the brim with roundabouts...

American drivers are angels and scholars

Perfect addition to the discussion!
If you plopped 200 American drivers down in Amman, how many of them do you think would have a traffic accident within the first week?
That's what I mean by incapable.
If you plopped 200 off-the-street americans into an every day life of third world country, how many of them would make it till the end of the week? Doesn't make people incapable or unfit for life.

Jordan has 151 accident/year  per 100k vehicles vs 13 in US - about 12 times higher accident rate. Of course, NASCAR would have an even higher accident rate - and even more skilled drivers.. But for last  10 year I mostly drive to get from point A to point B in one piece...

Perhaps 'incapable' is the wrong word.  Inept.  Incompetent.  I don't mean to imply that we Americans can't learn how to drive in unusual circumstances.  Just that we don't know how to do so.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on November 08, 2018, 02:16:26 PM
Just came back from Amman, which is packed to the brim with roundabouts...

American drivers are angels and scholars

Perfect addition to the discussion!
If you plopped 200 American drivers down in Amman, how many of them do you think would have a traffic accident within the first week?
That's what I mean by incapable.

We had a car and did not have a collision.

However, the local drivers did their best to hit us.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 08, 2018, 03:20:33 PM
Just came back from Amman, which is packed to the brim with roundabouts...

American drivers are angels and scholars

Perfect addition to the discussion!
If you plopped 200 American drivers down in Amman, how many of them do you think would have a traffic accident within the first week?
That's what I mean by incapable.
If you plopped 200 off-the-street americans into an every day life of third world country, how many of them would make it till the end of the week? Doesn't make people incapable or unfit for life.

Jordan has 151 accident/year  per 100k vehicles vs 13 in US - about 12 times higher accident rate. Of course, NASCAR would have an even higher accident rate - and even more skilled drivers.. But for last  10 year I mostly drive to get from point A to point B in one piece...

Perhaps 'incapable' is the wrong word.  Inept.  Incompetent.  I don't mean to imply that we Americans can't learn how to drive in unusual circumstances.  Just that we don't know how to do so.
People learn to respond to issues they face. If you don't expect F-16s dropping payload on you, you don't learn to duck and cover when you hear a jet coming. If the roads are plowed, you don't need to keep your ice driving techniques top notch. If the roads are maintained, you may forget what you do if a wheel explodes at high speed. All of these "don't need" may cost you a life elsewhere - or occasionally even closer to home.

US has a crash rate which is not impressive on EU standards, but pretty good on worldwide scale. That tells me that there is a certain ecosystem which keeps travel conditions - combination of roads and road conditions, control systems, vehicle conditions, driver training, enforcement and so on - on some level which allows for a reasonably safe environment. Not ideal, maybe - but given car-oriented design driving in US has to be a learnable  skill, not a rare talent.

All the complains  about "how bad other drivers are!" to me sound as if it is the complainer who need a refresher course. Yes, average driver in US is not a NASCAR driver. But when someone starts feeling NASCAR star on a general purpose interstate, they become the trouble, not mere mortals around
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 16, 2018, 04:33:51 AM
A few pages ago, I talked about a ramp meter that WSDOT was installing at the endlessly-modified Steptoe Roundabout (https://goo.gl/8YXTVo) in Richland, WA. It finally went live on Tuesday the 13th. Image of the meter below. Perhaps the only ramp meter in Eastern Washington. Funny thing is, it's not a ramp at all, just a random approach to a roundabout that's bogging the roundabout down during rush hour.

https://www.tri-cityherald.com/news/local/article221355170.html

(https://www.tri-cityherald.com/latest-news/412jnt/picture221436740/alternates/FREE_1140/traffic%20meter.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 10, 2018, 12:46:01 PM
Reports that a woman was struck as she attempted to cross a roundabout near St. Cloud State University on Saturday.  I knew this roundabout sounded familiar as another pedestrian was struck and killed at the roundabout in October 2017:

SUV Collides With St. Cloud Woman In Roundabout
http://www.kvsc.org/news-detail/suv-collides-with-st-cloud-woman-in-roundabout-12-10-2018/10218/

Driver in St. Cloud roundabout fatally hits pedestrian
http://www.startribune.com/driver-in-st-cloud-roundabout-fatally-hits-pedestrian/453113583/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 13, 2018, 12:44:58 PM
Crazy video: Semi truck speeds straight through roundabout, slams into fountain
https://www.4029tv.com/article/crazy-video-semi-truck-speeds-strait-through-roundabout-slams-into-fountain/25570757
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 13, 2018, 12:47:22 PM
Reports that a woman was struck as she attempted to cross a roundabout near St. Cloud State University on Saturday.  I knew this roundabout sounded familiar as another pedestrian was struck and killed at the roundabout in October 2017:

SUV Collides With St. Cloud Woman In Roundabout
http://www.kvsc.org/news-detail/suv-collides-with-st-cloud-woman-in-roundabout-12-10-2018/10218/

Driver in St. Cloud roundabout fatally hits pedestrian
http://www.startribune.com/driver-in-st-cloud-roundabout-fatally-hits-pedestrian/453113583/

And this is what crosswalks are for.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 13, 2018, 12:49:24 PM
Crazy video: Semi truck speeds straight through roundabout, slams into fountain
https://www.4029tv.com/article/crazy-video-semi-truck-speeds-strait-through-roundabout-slams-into-fountain/25570757

No injuries, good.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 13, 2018, 12:51:11 PM
The safest roundabout in America?  I believe this is on 350th street outside Brayton, Iowa:
(https://images.fineartamerica.com/images-medium-large-5/tree-in-the-middle-of-the-road-christopher-l-nelson.jpg)
https://www.google.com/maps/place/Tree+in+the+Road/@41.5044893,-94.8350544,114m/data=!3m1!1e3!4m5!3m4!1s0x87ecc76137280403:0xdd4c86f84005c37!8m2!3d41.5044189!4d-94.8350472
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 13, 2018, 12:53:59 PM
If that snow freezes over, I could see problems for downhill drivers trying to avoid the tree.
Title: Re: Crash prone 'modern roundabouts'
Post by: US71 on December 13, 2018, 12:54:28 PM
Crazy video: Semi truck speeds straight through roundabout, slams into fountain
https://www.4029tv.com/article/crazy-video-semi-truck-speeds-strait-through-roundabout-slams-into-fountain/25570757

Amity isn't very friendly to semi trucks to begin with (road wise).
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 13, 2018, 12:57:20 PM
Crazy video: Semi truck speeds straight through roundabout, slams into fountain
https://www.4029tv.com/article/crazy-video-semi-truck-speeds-strait-through-roundabout-slams-into-fountain/25570757

Amity isn't very friendly to semi trucks to begin with.

I like the implication:  the driver was taking out his frustration on the town.
Title: Re: Crash prone 'modern roundabouts'
Post by: US71 on December 13, 2018, 12:58:40 PM
If that snow freezes over, I could see problems for downhill drivers trying to avoid the tree.

WATCH OUT FOR THAT (AHH-AHH-AHH *THUD* ) TREE!
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 13, 2018, 01:00:39 PM
While that massive tree looks like it's in the middle of nowhere, 350th Street is only 0.5 mile from I-80.  If there is a major accident on I-80 between 690th St and 750th Street, then 350th Street would be a natural detour around it.
Title: Re: Crash prone 'modern roundabouts'
Post by: US 89 on December 13, 2018, 01:03:12 PM
All four entrances are controlled by stop signs. Might as well ditch the whole thing for a 4-way stop anyway. :pan:
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on December 13, 2018, 01:08:14 PM
The safest roundabout in America?

I'll do you one better. This is the safest roundabout in America.

(https://i.imgur.com/La9LCze.jpg)

(Not my picture.)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 13, 2018, 01:09:57 PM
All four entrances are controlled by stop signs. Might as well ditch the whole thing for a 4-way stop anyway. :pan:
Yeah, island is too small anyway, and in case of crash that tree may create an issue...
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 13, 2018, 01:12:00 PM
While that massive tree looks like it's in the middle of nowhere, 350th Street is only 0.5 mile from I-80.  If there is a major accident on I-80 between 690th St and 750th Street, then 350th Street would be a natural detour around it.

For the roughly three drivers who would be (a) within reach of the previous exit, (b) able to look up an alternate route on their cell phone while stuck in traffic, and (c) willing to drive 7 miles down dirt and gravel?  Yeah, OK, sure, you betcha.



Also note the severe lack of roadway illumination. 
Carnage will ensue!!!

(https://scontent-frt3-2.cdninstagram.com/vp/09077419be29568ec78f95e66f0c290e/5C3C0ED4/t51.2885-15/e35/20065534_776524685806171_5484105120192921600_n.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on December 13, 2018, 01:25:46 PM
Also note the severe lack of roadway illumination. 
Carnage will ensue!!!

Can you imagine if a semi went too fast through that stop sign and tipped over? We better put in a signal there instead.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 13, 2018, 03:16:37 PM
Seattle has traffic circles at probably 30-40% of all otherwise-unsigned intersections, many at the bottom of very steep streets: http://bit.ly/2QO05cK  --  At least those intersections don't have to deal with too many large vehicles (which usually end up going over the middle or turning left against traffic at these circles instead).

Luckily for Seattle, snow isn't that common. But it does happen, and as virtually any google search can turn up, there are lots of crashes when it does. Usually into parked cars and fences. Lots of streets are fenced off. Probably the one I linked above would be, if I had to guess.
Title: Re: Crash prone 'modern roundabouts'
Post by: Hot Rod Hootenanny on December 13, 2018, 09:10:56 PM
Meanwhile, back in the real world....
https://www.10tv.com/article/osu-study-roundabouts-could-be-key-stopping-distracted-driving
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 13, 2018, 09:24:54 PM
Meanwhile, back in the real world....
https://www.10tv.com/article/osu-study-roundabouts-could-be-key-stopping-distracted-driving

Quote
he university research group studied driver response and behaviors and found no fatalities within Ohio roundabouts.
https://www.13abc.com/content/news/One-dead-two-seriously-hurt-in-Springfield-Twp-crash-420839683.html

High quality study with results disproved within 2 minutes.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 13, 2018, 10:31:11 PM
Yeah I'm not sure where they were going with that study. I'm sure they found some reason to ignore the fatalities they did find.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 14, 2018, 08:31:59 AM
Yeah I'm not sure where they were going with that study. I'm sure they found some reason to ignore the fatalities they did find.
Looks like an MBA-type person lost someone in a distracted driving crash and now has an agenda.
They have a lot of media publications on distracted topic:
https://www.bloomberg.com/news/articles/2018-04-23/texting-and-driving-is-still-a-minor-ding-with-car-insurers
https://www.businessinsurance.com/article/20181120/NEWS08/912325218/Road-design-can-combat-distracted-driving-crashes-Ohio-State-University-Fisher-C?utm_campaign=BI20181120BreakingNewsAlert&utm_medium=email&utm_source=ActiveCampaign&utm_campaign=BI2018112
https://fisher.osu.edu/news/risk-institute-leads-nationwide-initiative-curb-distracted-driving

But I cannot find a single recent peer-reviewed publication from  Phil Renaud. Overall IMHO this is something like bad PR by a c-suit manager and borderline academic fraud. 
Title: Re: Crash prone 'modern roundabouts'
Post by: ErmineNotyours on December 26, 2018, 11:26:51 PM
Sage advice.  SR 203 and NE 124th St, Duvall, Washington.

(https://farm5.staticflickr.com/4811/45567960325_ac3058e01e_z.jpg) (https://flic.kr/p/2cqFH3n)Traffic roundabout near Duvall, WA (https://flic.kr/p/2cqFH3n) by Arthur Allen (https://www.flickr.com/photos/116988743@N07/), on Flickr
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 27, 2018, 06:24:47 AM
Sage advice.  SR 203 and NE 124th St, Duvall, Washington.

(https://farm5.staticflickr.com/4811/45567960325_ac3058e01e_z.jpg) (https://flic.kr/p/2cqFH3n)Traffic roundabout near Duvall, WA (https://flic.kr/p/2cqFH3n) by Arthur Allen (https://www.flickr.com/photos/116988743@N07/), on Flickr
definitely something not unique to roundabouts:
(https://www.mysafetysign.com/img/lg/S/vehicle-caution-sign-s-4467.png)
Although this one is even better: https://www.google.com/maps/@43.3097114,-73.6443655,3a,75y,149.05h,66.41t/data=!3m5!1e1!3m3!1scMVP6fQnoyfxnLVQ1h1vLA!2e0!6s%2F%2Fgeo1.ggpht.com%2Fcbk%3Fpanoid%3DcMVP6fQnoyfxnLVQ1h1vLA%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D349.61212%26pitch%3D0%26thumbfov%3D100
Overall, designing tight interections into truck routes is a bad idea - but sometimes there is just not enough room for something better.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 10, 2019, 03:29:42 PM
County Crash Report: Wrecks Spike Near One New Roundabout
http://www.wbaa.org/post/county-crash-report-wrecks-spike-near-one-new-roundabout#stream/0

According to the article, the roundabout at Tapawingo Drive and River Road saw 73 'nearby crashes' in 2017.  The 2x2 roundabout was constructed in 2016.  From 2013 to 2015, the intersection saw just 17 accidents (or 5.66 average crashes per year).
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 10, 2019, 04:11:23 PM
Quote
That’s kind of a general pattern you see with roundabouts
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 10, 2019, 07:34:52 PM
Quote
That’s kind of a general pattern you see with roundabouts

That crashes go down over time? I'm not sure we've seen that.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 11, 2019, 01:47:42 PM
Quote
That’s kind of a general pattern you see with roundabouts

That crashes go down over time? I'm not sure we've seen that.

Well, that was only half of his point.  Let's not miss the fact that he publicly admitted new roundabouts see high crash rates in the beginning.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 11, 2019, 03:10:49 PM
Quote
That’s kind of a general pattern you see with roundabouts

That crashes go down over time? I'm not sure we've seen that.

Well, that was only half of his point.  Let's not miss the fact that he publicly admitted new roundabouts see high crash rates in the beginning.

Indeed. And I'm not sure we've seen such mentions on the FHWA websites. Something smells fishy here.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 25, 2019, 10:57:35 AM
Crashes have nearly tripled at the Sharpes Corner roundabout in Anacortes, Washington.  According to the article there have been 47 vehicle collisions in the Sharpes Corner roundabout from when it opened June 23 to March 19 compared to 17 collisions during the same time period before the roundabout.  That's not as bad as it sounds though, considering it is a new roundabout and the first few months of crashes should be largely overlooked.  I'm still concerned that it's only a matter of time before a truck going eastbound rolls over and ends up on laying on its side near the southern leg of the roundabout.  The eastbound geometry leading up to that roundabout is concerning to me still.  This was taken directly from the article:

Quote
Ron Davis, owner of Anacortes Flea Market and Ron’s Produce, said many motorists don’t know how to drive in a roundabout or drive too fast.

“The speed limit in the roundabout is 15 mph, and there’s a truck right now going through there at 25 and he’s leaning,”  Davis said early Tuesday. “Collisions are going to continue if (police) don’t slow them down. I hear screeching tires all day long.”

This guy's Flea Market is right at the corner of the new roundabout.  He's concerned with how fast trucks are driving through the roundabout and sees them leaning as they drive through.  It seems like a matter of time before one tips over.

Crashes piling up in newest roundabouts
https://www.goskagit.com/anacortes/crashes-piling-up-in-newest-roundabouts/article_6590d32e-4a9b-11e9-9d84-37afd04670c2.html#comments
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on March 25, 2019, 11:03:10 AM
That's not as bad as it sounds though, considering it is a new roundabout and the first few months of crashes should be largely overlooked.

Still gotta post about it though! Can't let anyone miss this crucial news!

I'm still concerned that it's only a matter of time before a truck going eastbound rolls over and ends up on laying on its side near the southern leg of the roundabout.

And aliens might land on the middle island and vaporize the surrounding neighborhood.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 25, 2019, 11:19:47 AM
That's not as bad as it sounds though, considering it is a new roundabout and the first few months of crashes should be largely overlooked.

Still gotta post about it though! Can't let anyone miss this crucial news!

I'm still concerned that it's only a matter of time before a truck going eastbound rolls over and ends up on laying on its side near the southern leg of the roundabout.

And aliens might land on the middle island and vaporize the surrounding neighborhood.

There are well documented roundabouts that are prone to truck tip-overs. The roundabouts in Worthington, MN and the Howard Avenue Diversion roundabout outside Windsor, Ontario has had a significant number of truck tip-overs.  The Sharpes Corner roundabout is another good candidate for becoming a truck tip-over hot spot.  Look at the streetview image of EB traffic approaching the Shapres Corner roundabout.  Before the roundabout traffic is likely cruising at 55-60 mph and it just seems like the roundabout could up on you fast.  There is no overhead signage that traffic is approaching a roundabout.  I could definitely see a truck driver not paying close enough attention as they cruise down that limited access highway and all of a sudden they are face to face with a massive curve in the road (aka a roundabout).

https://www.google.com/maps/@48.4643916,-122.5838762,3a,60y,120.35h,90t/data=!3m6!1e1!3m4!1s4Y818I69qnBH6bjeVkx_QQ!2e0!7i13312!8i6656
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 25, 2019, 11:32:26 AM
That's not as bad as it sounds though, considering it is a new roundabout and the first few months of crashes should be largely overlooked.

Still gotta post about it though! Can't let anyone miss this crucial news!

I'm still concerned that it's only a matter of time before a truck going eastbound rolls over and ends up on laying on its side near the southern leg of the roundabout.

And aliens might land on the middle island and vaporize the surrounding neighborhood.

There is another way of looking at it. Basically we're talking about a roundabout eating up 27 months worth of crashes quota in first 9 months. If there is 0 accidents from March 20th and on for the next two years, construction costs are not bringing any safety improvement for at least another 1.5 years.
If accident rate settles down to 50% of pre-construction value (still quite optimistic prediction given the rough start), it will be 4 years from the day construction was completed until total  number of crashes breaks even. I am not sure what is the lifetime of this installation, 10 years? 25 years?
So safety improvement will be 20 to 50% lower that what is going to be reported few years down the line just due to initial overhead. Numbers would be even worse if those funds could be spent on some safety-critical work elsewhere.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on March 25, 2019, 11:40:25 AM
WSDOT doesn't usually over-post anything; as it relates to this roundabout, though there are signs approaching the junction warning of the circle, it's only a few.

Have you seen a correlation between signage and crashes?

Driving through that Anacortes roundabout myself more than a few times, the issue spot seems to be the eastbound entry. The occasional car would go into the wrong lane.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 07, 2019, 08:25:11 PM

(https://i.imgur.com/0Sr2PD4.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: BrianP on May 08, 2019, 09:59:43 AM
I agree completely.  The drivers are the problem. If they can't drive correctly then take away their licenses. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 08, 2019, 10:11:13 AM
I agree completely.  The drivers are the problem. If they can't drive correctly then take away their licenses.
Put your money where your mouth is - surrender your license today!
Title: Re: Crash prone 'modern roundabouts'
Post by: BrianP on May 08, 2019, 10:51:12 AM
Your statement makes no sense.  Who anything about surrendering? Surrender is voluntary.  This would compulsory for things like reckless driving. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 08, 2019, 01:20:26 PM
Your statement makes no sense.  Who anything about surrendering? Surrender is voluntary.  This would compulsory for things like reckless driving. 

If you are so concerned that drivers are the problem at these roundabouts, then maybe they should take your license away Brian.  Before you resist, studies have found that drivers believe they are better drivers than they are.  When asked to rate their driving skills, 93% of Americans say they are above average drivers.  In other news 72% of all statistics are made up, so maybe your license is safe.  But to suggest kalvado's statement made no sense.. you must not be thinking that hard.  Now i really am part of the 7% of GREAT drivers.  If they take away the licenses of all the bad drivers like you, the roads would free up space for me!   See what i did there?  I turned myself into a pretentious A-Hole driver just like you! 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 08, 2019, 02:15:07 PM

(https://i.imgur.com/0Sr2PD4.png)

Because roundabouts are curvy.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 16, 2019, 03:07:09 PM
Michigan’s Most Dangerous Intersections: Top 20 in 2018
https://www.michiganautolaw.com/blog/2019/05/15/michigans-most-dangerous-intersections-top-20-2018/

The annual list of most dangerous intersections in Michigan just came out.  The Orchard Lake @ 14 Mile roundabout (constructed in 2015) ranked #2 on the list with 144 total crashes and 20 injury crashes.  According to SEMCOG, the intersection had just 20 total crashes and 2 injury crashes in 2014 (the last year before the roundabout was constructed).  After 4 years of operation, the roundabout is seeing a 10-fold increase in injury crashes and a 7-fold increase in PDO crashes when compared to the pre-roundabout condition.

Other roundabouts that made the list of most dangerous intersections in Michigan in 2018 include the 18 1/2 Mile Road @ Van Dyke roundabout (ranked #3 w/141 crashes, 12 injuries), the M-5 @ Pontiac Trail roundabout (ranked #4 w/138 crashes, 9 injuries), and the State Street @ Ellsworth roundabout (ranked #8 w/123 crashes, 6 injuries).
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 16, 2019, 03:12:12 PM
What the hell is up with 12-Mile / Telegraph? Lots of crashes for an intersection without any left turns, and regular-ol' traffic lights. Not saying left turns are bad, but there are fewer conflict points without them.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 16, 2019, 04:05:02 PM
What the hell is up with 12-Mile / Telegraph? Lots of crashes for an intersection without any left turns, and regular-ol' traffic lights. Not saying left turns are bad, but there are fewer conflict points without them.

Probably the biggest problem is the intersection is about 2000 feet north of the US-24 / M-10 / I-696 "mixing bowl".  Driving going SB Telegraph taking 696 or the Lodge are all fighting to get over to the right lane to take the ramps while drivers continuing on Telegraph are trying to merge over to the left lane (as the right lanes always get backed up during rush hour).  Then on the SE corner you have a large shopping center with a busy exit that conflicts with Michigan Left turnaround traffic.  Then on the SW corner there are more office and commercial buildings with numerous drives that conflict with all the traffic trying to enter onto the freeways.  On top of that 3 of the 4 corners at the intersection are gas stations.  For at least 20 years that intersection has been notorious in the region for having lots of crashes and it's just a cluster driving through it. 

Also, when compiling the crash data at these Michigan left intersections they are looking at crashes occurring 250 feet from the main signal and 250 feet from the crossover signals.  What would otherwise be categorized as a mid-block crash may be categorized as an intersection crash at these Median U-turn intersections. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 29, 2019, 03:27:58 PM
^Apart from the RV blowing through the middle of that Worthington Minnesota roundabout, there has been two other pretty major events at the roundabout over the past couple weeks.

Tanker hauling cream overturns in Worthington roundabout
(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/111117.N.DG_.TANKERCREAM%20rgb_0.jpg?itok=rxMKiQ4I)
http://www.dglobe.com/news/accidents/4356792-tanker-hauling-cream-overturns-worthington-roundabout


These little piggies almost didn't make it to market when a Minn. hog truck rolled

(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/102817.N.DG_.ROLLOVER%203.jpg?itok=DOQatmVs)
http://www.agweek.com/news/4350581-these-little-piggies-almost-didnt-make-it-market-when-minn-hog-truck-rolled

Cream trucks rolling over, hogs running around the highway, some RV driver thinking they are Bo Duke... these roundabouts really give the good people of Worthington Minnesota something to talk about!


Another vehicle vaulted over the Worthington roundabout on Sunday.  The driver sustained non-life threatening injuries.  This comes a month after an RV was videotaped launching over the roundabout in early November.

Minivan vaults over roundabout Sunday
https://www.dglobe.com/news/accidents/4375814-minivan-vaults-over-roundabout-sunday

There have been 2 truck tip-over crashes, an RV flying through the middle of the roundabout captured on video, a driver sustaining non life-sustaining injuries after his min-van flew through the middle of the roundabout, and now 4 reported crashes over a few hour period on Friday.  The roundabouts are doing a stellar job at reducing crashes in Worthington.. or maybe they are doing a worthless job.

Snowpacked roundabouts result in four crashes reported Friday
https://www.dglobe.com/news/4380839-snowpacked-roundabouts-result-four-crashes-reported-friday

Yet another semi-rollover happened at the Worthington roundabout Friday morning.

A roundabout rollover
(http://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/072118.N.DG_.%20Round%20about%20roll%202%20web.jpg?itok=ia9BHMPT)
http://dglobe.com/news/accidents/4475427-roundabout-rollover

Another semi loses his load at the Worthington roundabout on Tuesday.  This is at least the 4th semi to tip over/lose their load since October, 2017. 

Spilled grain in Worthington roundabout
(https://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/073118.N.TG_.%20Semi%20roll%20over%20of%20the%20week%20web.jpg?itok=uZyr2Bsy)
http://www.dglobe.com/news/accidents/4479958-spilled-grain-worthington-roundabout

Another semi rolled over at a Worthington roundabout today (October 22, 2018).  One person was taken to the hospital with non-life threatening injuries.  In the past year there has been 5 documented cases of semi trucks tipping over/losing their load in Worthington roundabouts.  Maybe it's time for Worthington to consider ripping these roundabouts out as they just don't seem to be working out too well in their community!

Semi rollover in Worthington injures one
http://www.kkoj.com/news/local-news/semi-rollover-in-worthington-injures-one/

Yet more problems at Worthington's roundabouts.  This time a drunk woman with a 7-year old child passenger vaulted over a roundabout on Minnesota 60. 

Sioux Falls woman faces charges after vaulting over roundabout
https://www.dglobe.com/news/crime-and-courts/4618742-sioux-falls-woman-faces-charges-after-vaulting-over-roundabout

And a semi tipped over at the 59/60 roundabout way back in 2015, but i don't believe it was reported on this thread so i'll just add it for good measure.

Names released in semi roundabout accident
https://www.dglobe.com/news/3813093-names-released-semi-roundabout-accident
(https://www.dglobe.com/sites/default/files/styles/16x9_620/public/field/image/TruckFlippedRGB.jpg?itok=72jStMgL)
Title: Re: Crash prone 'modern roundabouts'
Post by: TheHighwayMan394 on May 29, 2019, 03:32:37 PM
Here we are again. It’s the roundabout’s fault the woman was drunk and speeding.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 29, 2019, 04:16:03 PM
Here we are again. It’s the roundabout’s fault the woman was drunk and speeding.

With your logic there is no need to convert traffic signals to roundabouts in the first place.  When a drunk driver blows through a red light it's not the red lights fault they were drunk and speeding.  Why are we worried about fatal t-bone accidents at traffic signals when alcohol was a factor?  After all, you can't stop stupid. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 29, 2019, 04:35:12 PM
Geez, there are a lot of truck tip-overs in Worthington!
Title: Re: Crash prone 'modern roundabouts'
Post by: TheHighwayMan394 on May 29, 2019, 04:36:52 PM
Here we are again. It’s the roundabout’s fault the woman was drunk and speeding.

With your logic there is no need to convert traffic signals to roundabouts in the first place.  When a drunk driver blows through a red light it's not the red lights fault they were drunk and speeding.  Why are we worried about fatal t-bone accidents at traffic signals when alcohol was a factor?  After all, you can't stop stupid. 

With the roundabout that dramatically minimizes the chances this lady would have plowed into someone else.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 29, 2019, 04:43:20 PM


Here we are again. It’s the roundabout’s fault the woman was drunk and speeding.

With your logic there is no need to convert traffic signals to roundabouts in the first place.  When a drunk driver blows through a red light it's not the red lights fault they were drunk and speeding.  Why are we worried about fatal t-bone accidents at traffic signals when alcohol was a factor?  After all, you can't stop stupid. 

With the roundabout that dramatically minimizes the chances this lady would have plowed into someone else.

How?  A driver crossing her path in the roundabout is (roughly) no less at a 90° angle to the other driver than one crossing a stoplighted intersection.  I guess she was less likely to hit someone on the far side of the roundabout...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 29, 2019, 05:06:03 PM
With the roundabout that dramatically minimizes the chances this lady would have plowed into someone else.

Have you heard the story about the guy in Raleigh where his house has been hit 6 times?  His house has become the ultimate “bad driver”  magnet.  While the lives of him and his family are in danger, he is doing a public service by stopping all those impaired drivers before they get a chance to hurt anybody else on the road.  If drivers can hit this poor guy's house 6 times, it's not surprising that some drivers can blow straight through the center of a roundabout.

Raleigh man fed up after house hit by car for 6th time
https://abc11.com/news/raleigh-man-fed-up-after-house-hit-by-car-for-6th-time/1469768/
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 29, 2019, 05:14:40 PM
^^
I notice from Street View that access to his neighborhood was cut-off, and the guardrail extended, since that story was posted:

https://goo.gl/maps/jWucN8h47GAoaqtC9
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 29, 2019, 05:22:18 PM
Here we are again. It’s the roundabout’s fault the woman was drunk and speeding.

With your logic there is no need to convert traffic signals to roundabouts in the first place.  When a drunk driver blows through a red light it's not the red lights fault they were drunk and speeding.  Why are we worried about fatal t-bone accidents at traffic signals when alcohol was a factor?  After all, you can't stop stupid. 

With the roundabout that dramatically minimizes the chances this lady would have plowed into someone else.
Probably increases those chances, actually.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 29, 2019, 05:24:27 PM
WSDOT is building two new roundabouts near Camas (just north of the Columbia River) along WA-14. Construction started today (http://wsdot.wa.gov/news/2019/05/23/two-new-roundabouts-coming-sr-14-washougal). The two intersections are roughly at either end of this Maps link (https://www.google.com/maps/@45.5759382,-122.3466372,1375m/data=!3m1!1e3) (15 St/Washougal River Rd, and 32 St).

These are relatively simple one-lane roundabouts (with one extra lane at 32 St), but what is more worrisome for me, is that they're being built just east of a brand new freeway interchange (https://goo.gl/maps/xtK2kpAJWbDYhXf9A). WA-14 is basically a freeway or Super-2 from I-5 (16 miles away), all the way to this point. This would not be the first roundabout at the terminus of a freeway, but it doesn't seem like that great of an idea to me. WA-14 is either 55 or 60 from I-5, up to 15 St (the first roundabout).

I'm not trying to imply that a signal would absolutely be better. But I would assume that a signal, with a flashing "prepare to stop" message and rumble strips perpendicular to the lanes, would be better than a roundabout, as those really can sneak up on you, if you're not expecting them (which people may not be, after driving along 16 miles worth of divided highway).

(https://www.wsdot.wa.gov/sites/default/files/2016/10/26/SR14_AccessImprov_15th_Roundabout_510x324px.png) (https://www.wsdot.wa.gov/sites/default/files/2016/10/26/SR14_AccessImprov_32nd_Roundabout_510x324px.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 29, 2019, 05:40:21 PM
WSDOT is building two new roundabouts near Camas (just north of the Columbia River) along WA-14. Construction started today (http://wsdot.wa.gov/news/2019/05/23/two-new-roundabouts-coming-sr-14-washougal). The two intersections are roughly at either end of this Maps link (https://www.google.com/maps/@45.5759382,-122.3466372,1375m/data=!3m1!1e3) (15 St/Washougal River Rd, and 32 St).

These are relatively simple one-lane roundabouts (with one extra lane at 32 St), but what is more worrisome for me, is that they're being built just east of a brand new freeway interchange (https://goo.gl/maps/xtK2kpAJWbDYhXf9A). WA-14 is basically a freeway or Super-2 from I-5 (16 miles away), all the way to this point. This would not be the first roundabout at the terminus of a freeway, but it doesn't seem like that great of an idea to me. WA-14 is either 55 or 60 from I-5, up to 15 St (the first roundabout).

I'm not trying to imply that a signal would absolutely be better. But I would assume that a signal, with a flashing "prepare to stop" message and rumble strips perpendicular to the lanes, would be better than a roundabout, as those really can sneak up on you, if you're not expecting them (which people may not be, after driving along 16 miles worth of divided highway).

(https://www.wsdot.wa.gov/sites/default/files/2016/10/26/SR14_AccessImprov_15th_Roundabout_510x324px.png) (https://www.wsdot.wa.gov/sites/default/files/2016/10/26/SR14_AccessImprov_32nd_Roundabout_510x324px.png)
You can definitely supplement roundabout with any kind of warning that can be used for a traffic light. I thought I had an example of rumble strip before roundabout - but google maps don't show that. Hard to tell if that is my memory issue or old map data. The only thing positively unavailable is traffic light itself being located above the road right in front of the driver. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 29, 2019, 06:19:59 PM
You can definitely supplement roundabout with any kind of warning that can be used for a traffic light. I thought I had an example of rumble strip before roundabout - but google maps don't show that. Hard to tell if that is my memory issue or old map data. The only thing positively unavailable is traffic light itself being located above the road right in front of the driver.

For sure. I see plenty of warning devices used at roundabouts (WI seems to be the king of this...WSDOT is pretty bad at advanced roundabout warning signage), though I find the "when flashing" warning devices at signals to be especially effective because they aren't always flashing. They catch your eye, especially if they start flashing only as you approach the sign. With a roundabout, it would have to be constantly flashing, and I'm not certain how effective those are.

Granted, if you're not aware of the approaching roundabout, a constant flashing orb might catch your attention. So perhaps not all is lost.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on May 29, 2019, 09:41:06 PM
You can definitely supplement roundabout with any kind of warning that can be used for a traffic light. I thought I had an example of rumble strip before roundabout - but google maps don't show that. Hard to tell if that is my memory issue or old map data. The only thing positively unavailable is traffic light itself being located above the road right in front of the driver.

For sure. I see plenty of warning devices used at roundabouts (WI seems to be the king of this...WSDOT is pretty bad at advanced roundabout warning signage), though I find the "when flashing" warning devices at signals to be especially effective because they aren't always flashing.

Effective until the light burns out or the flasher malfunctions. When that happens you get a bunch of blissfully ignorant drivers heading for a rude awakening. A few areas ban those kind of advanced signals because that potential.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 29, 2019, 10:43:05 PM
You can definitely supplement roundabout with any kind of warning that can be used for a traffic light. I thought I had an example of rumble strip before roundabout - but google maps don't show that. Hard to tell if that is my memory issue or old map data. The only thing positively unavailable is traffic light itself being located above the road right in front of the driver.

For sure. I see plenty of warning devices used at roundabouts (WI seems to be the king of this...WSDOT is pretty bad at advanced roundabout warning signage), though I find the "when flashing" warning devices at signals to be especially effective because they aren't always flashing.

Effective until the light burns out or the flasher malfunctions. When that happens you get a bunch of blissfully ignorant drivers heading for a rude awakening. A few areas ban those kind of advanced signals because that potential.

That's why you install two sets of signs on either side of the carriageway, each with two lights. What are the chances that the entire assembly is going to break? And if one bulb burns out, there's still three left.

(https://i.imgur.com/awFcnKA.png)

Which areas ban them? Never heard of such lunacy. BC requires them on all roads with a 70+ km/h limit.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on May 29, 2019, 11:41:37 PM
You can definitely supplement roundabout with any kind of warning that can be used for a traffic light. I thought I had an example of rumble strip before roundabout - but google maps don't show that. Hard to tell if that is my memory issue or old map data. The only thing positively unavailable is traffic light itself being located above the road right in front of the driver.

For sure. I see plenty of warning devices used at roundabouts (WI seems to be the king of this...WSDOT is pretty bad at advanced roundabout warning signage), though I find the "when flashing" warning devices at signals to be especially effective because they aren't always flashing.

Effective until the light burns out or the flasher malfunctions. When that happens you get a bunch of blissfully ignorant drivers heading for a rude awakening. A few areas ban those kind of advanced signals because that potential.

That's why you install two sets of signs on either side of the carriageway, each with two lights. What are the chances that the entire assembly is going to break? And if one bulb burns out, there's still three left.

Which areas ban them? Never heard of such lunacy. BC requires them on all roads with a 70+ km/h limit.

Let me rephrase that, some ban the concept of "when flashing" text being associated with an advanced traffic signal or railroad warning sign. WisDOT is one of them*. They will allow the phase on signs of lesser importance, like highway advisory radio signs (https://goo.gl/maps/uErgLPcNYuJTKa29A). They allow flashing beacons (https://goo.gl/maps/sEfNAmTSMTfUNbfx8) to be associated with intersection control warning signs, but they have to flash 24/7.

*Note, I was told this many years ago by a former state signalling engineer; however, I have not been able to find the supporting text in their guides and manuals beyond ties to railroad crossings. It may have been another 'verbal policy' that has sticking power among the decision makers.

You also have to remember that many of these systems, despite being on both sides of the carriageway, are fed by a common power conduit. One short upstream of the beacons, and neither one of them work.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 30, 2019, 02:10:55 AM
You also have to remember that many of these systems, despite being on both sides of the carriageway, are fed by a common power conduit. One short upstream of the beacons, and neither one of them work.

That seems like it would be unusual, but I'll give you the benefit of the doubt. But consider this: how are we to say that the net-negative effects of an inoperable PTSWF sign are of greater significance than the net-positive effects of an operable PTSWF sign? Both in contrast to not having a sign at all.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on May 30, 2019, 09:20:10 AM
You also have to remember that many of these systems, despite being on both sides of the carriageway, are fed by a common power conduit. One short upstream of the beacons, and neither one of them work.

That seems like it would be unusual, but I'll give you the benefit of the doubt. But consider this: how are we to say that the net-negative effects of an inoperable PTSWF sign are of greater significance than the net-positive effects of an operable PTSWF sign? Both in contrast to not having a sign at all.

I think you're making this a lot more complicated than it needs to be. Just let them flash constantly. What does it hurt? It also simplifies the wiring and programming needs. Having 24/7 flash and no sign has a better/safer driver default response than with the PTSWF. One could also say the part-time flash and sign is not necessary, as being prepared to possibly have to stop should be assumed with the Signal Ahead warning sign.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 30, 2019, 10:57:12 AM
You can definitely supplement roundabout with any kind of warning that can be used for a traffic light. I thought I had an example of rumble strip before roundabout - but google maps don't show that. Hard to tell if that is my memory issue or old map data. The only thing positively unavailable is traffic light itself being located above the road right in front of the driver.

For sure. I see plenty of warning devices used at roundabouts (WI seems to be the king of this...WSDOT is pretty bad at advanced roundabout warning signage), though I find the "when flashing" warning devices at signals to be especially effective because they aren't always flashing.

Effective until the light burns out or the flasher malfunctions. When that happens you get a bunch of blissfully ignorant drivers heading for a rude awakening. A few areas ban those kind of advanced signals because that potential.

That's why you install two sets of signs on either side of the carriageway, each with two lights. What are the chances that the entire assembly is going to break? And if one bulb burns out, there's still three left.

(https://i.imgur.com/awFcnKA.png)

Which areas ban them? Never heard of such lunacy. BC requires them on all roads with a 70+ km/h limit.
This is actually an install which I find a bit prone to specific problem:
in case of larger-scale power outage, a driver who is not aware of the situation would assume that traffic light is off by design and they don't need to stop - and end up running inop light assuming they have right of the way. So power outage creates a significantly difficult situation
Rewording "prepare to stop" with light just to attract attention eliminates that scenario.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on May 30, 2019, 11:00:45 AM
in case of larger-scale power outage, a driver who is not aware of the situation would assume that traffic light is off by design and they don't need to stop

This seems like a bit of a reach. (Edit: Normal) traffic signals are never "off by design," so I find it improbable that any driver would ever think this.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on May 30, 2019, 11:03:01 AM
in case of larger-scale power outage, a driver who is not aware of the situation would assume that traffic light is off by design and they don't need to stop

This seems like a bit of a reach. Traffic signals are never "off by design," so I find it improbable that any driver would ever think this.

Thanks to the wonders of the HAWK, this is not true!
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on May 30, 2019, 11:39:01 AM
in case of larger-scale power outage, a driver who is not aware of the situation would assume that traffic light is off by design and they don't need to stop

This seems like a bit of a reach. (Edit: Normal) traffic signals are never "off by design," so I find it improbable that any driver would ever think this.

Years ago, I would agree with you, but you can't assume common sense with most of today's drivers.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 30, 2019, 11:48:07 AM
in case of larger-scale power outage, a driver who is not aware of the situation would assume that traffic light is off by design and they don't need to stop

This seems like a bit of a reach. (Edit: Normal) traffic signals are never "off by design," so I find it improbable that any driver would ever think this.

Years ago, I would agree with you, but you can't assume common sense with most of today's drivers.
You cannot assume common sense in design either.
 If speed limit can be changed with illuminated sign - higher limit when dark; HAWK mentioned above; FYA which is in a class of its own... Traffic light only active during rush hour is easy to envision.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 30, 2019, 02:05:13 PM
Studies have found that HAWK signals at roundabouts have a high non-compliance rate among drivers.  Based on a 2011 HAWK study (https://www.rcocweb.org/DocumentCenter/View/99/HAWK-and-RRFB-study-2011-PDF) done by Western Michigan University, 12.9% of drivers exiting the roundabout proceeded through the crosswalk when the HAWK signal was displaying a Steady Red/Walk and 24.4% of exiting drivers proceeded through the crosswalk when the HAWK was displaying Flashing Red/Flashing Don’t Walk.  Not only can HAWK signals be ineffective at roundabouts, they add additional poles in the vicinity of the roundabout that an out of control driver may strike.  Here is an aerial of the 14 Mile & Orchard Lake roundabout and the roughly 20 poles surrounding it.

(https://www.mtjengineering.com/wp-content/uploads/2014/10/OLR-3.jpg)

Driving through street-view, you can see a steel light pole laying on the ground next to the roundabout (presumably to replace a light pole that had previously been taken out)
(https://i.imgur.com/mT4FBR5.png)

And a few weeks ago a driver struck a mast-arm pole 300 feet north of the roundabout.  The impact nearly split the car in two.   While it was initially reported that the crash occurred at the roundabout itself, the driver did not drive through the roundabout before striking the pole.  However, it does show the potential dangers of striking a solid steel pole which this roundabout is littered with.  If you lose control near this roundabout you would be hard pressed not to strike a steel pole. 
(https://media.clickondetroit.com/photo/2019/05/08/1_dead_1_injured_after_crash_at_14_Mile_Orchard_Lake_roads_1557312211635_21828621_ver1.0_640_360.jpg)

1 dead, 1 injured in crash at Northwestern Highway, Orchard Lake Road following chase
https://www.clickondetroit.com/news/1-dead-1-injured-in-crash-at-northwestern-highway-orchard-lake-road-following-chase


Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 30, 2019, 02:20:33 PM
You can definitely supplement roundabout with any kind of warning that can be used for a traffic light. I thought I had an example of rumble strip before roundabout - but google maps don't show that.

Oh yeah, I've definitely seen advance warnings for roundabouts.  Here is a set of rumble strips (https://goo.gl/maps/a9bthxoAeodnrmjv7) on US-50 approaching US-77.  Here's one (https://goo.gl/maps/iTeLGwGLbU9TUHiH9) on US-400 approaching KS-47.  Here's one (https://goo.gl/maps/shAVYhNaMDe34MDA6) on US-60 approaching MO-43.  And, after doing some internet searching, here's a flashing beacon (https://goo.gl/maps/HhVYpAgRvfPC6uMe7) on CA-246 approaching Purisima Road
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on May 30, 2019, 02:43:25 PM
Studies have found that HAWK signals at roundabouts have a high non-compliance rate among drivers.  Based on a 2011 HAWK study (https://www.rcocweb.org/DocumentCenter/View/99/HAWK-and-RRFB-study-2011-PDF) done by Western Michigan University, 12.9% of drivers exiting the roundabout proceeded through the crosswalk when the HAWK signal was displaying a Steady Red/Walk and 24.4% of exiting drivers proceeded through the crosswalk when the HAWK was displaying Flashing Red/Flashing Don’t Walk.  Not only can HAWK signals be ineffective at roundabouts, they add additional poles in the vicinity of the roundabout that an out of control driver may strike.  Here is an aerial of the 14 Mile & Orchard Lake roundabout and the roughly 20 poles surrounding it.

(https://www.mtjengineering.com/wp-content/uploads/2014/10/OLR-3.jpg)

Driving through street-view, you can see a steel light pole laying on the ground next to the roundabout (presumably to replace a light pole that had previously been taken out)
(https://i.imgur.com/mT4FBR5.png)

And a few weeks ago a driver struck a mast-arm pole 300 feet north of the roundabout.  The impact nearly split the car in two.   While it was initially reported that the crash occurred at the roundabout itself, the driver did not drive through the roundabout before striking the pole.  However, it does show the potential dangers of striking a solid steel pole which this roundabout is littered with.  If you lose control near this roundabout you would be hard pressed not to strike a steel pole. 
(https://media.clickondetroit.com/photo/2019/05/08/1_dead_1_injured_after_crash_at_14_Mile_Orchard_Lake_roads_1557312211635_21828621_ver1.0_640_360.jpg)

1 dead, 1 injured in crash at Northwestern Highway, Orchard Lake Road following chase
https://www.clickondetroit.com/news/1-dead-1-injured-in-crash-at-northwestern-highway-orchard-lake-road-following-chase

HAWK compliance aside, updated signalized intersections aren't much less dangerous with regard to non-breakaway steel poles. This one (https://goo.gl/maps/MiCNuETGa3kRozYC8) has 9 such poles (not including those used for overhead lane control signs) on a high-speed corridor.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on May 30, 2019, 03:04:50 PM
  Here is an aerial of the 14 Mile & Orchard Lake roundabout and the roughly 20 poles surrounding it.

(https://www.mtjengineering.com/wp-content/uploads/2014/10/OLR-3.jpg)

Garbage roundabout. Note the lack of deflection on exit, so drivers are accelerating rapidly into the crosswalk.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 30, 2019, 03:19:42 PM
  Here is an aerial of the 14 Mile & Orchard Lake roundabout and the roughly 20 poles surrounding it.

(https://www.mtjengineering.com/wp-content/uploads/2014/10/OLR-3.jpg)

Garbage roundabout. Note the lack of deflection on exit, so drivers are accelerating rapidly into the crosswalk.
Garbage roundabout sounds like dirty trash or wet water to me.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on May 30, 2019, 03:27:59 PM
  Here is an aerial of the 14 Mile & Orchard Lake roundabout and the roughly 20 poles surrounding it.

(https://www.mtjengineering.com/wp-content/uploads/2014/10/OLR-3.jpg)

Garbage roundabout. Note the lack of deflection on exit, so drivers are accelerating rapidly into the crosswalk.

Isn't that how a roundabout is properly designed, with less deflection on exit?

The problem with roundabout crosswalks is that it only leaves room for a car or two to stop, before traffic behind them would be stopped within the crosswalk.  It also created a sight-hazard - as motorists are looking left for traffic coming into the roundabout, a motorist probably isn't looking to the right where the stopped traffic would be located.

Note to the left of the picture.  Those crosswalks are much further away from the roundabout. Much better location there.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on May 30, 2019, 03:48:21 PM
  Here is an aerial of the 14 Mile & Orchard Lake roundabout and the roughly 20 poles surrounding it.

(https://www.mtjengineering.com/wp-content/uploads/2014/10/OLR-3.jpg)

Garbage roundabout. Note the lack of deflection on exit, so drivers are accelerating rapidly into the crosswalk.

Isn't that how a roundabout is properly designed, with less deflection on exit?

The problem with roundabout crosswalks is that it only leaves room for a car or two to stop, before traffic behind them would be stopped within the crosswalk.  It also created a sight-hazard - as motorists are looking left for traffic coming into the roundabout, a motorist probably isn't looking to the right where the stopped traffic would be located.

Note to the left of the picture.  Those crosswalks are much further away from the roundabout. Much better location there.

Properly designed depends on what standard youre using.

If youre US highway metrics like "vehicles per hour", then yes, the straighter the better.

If your metric is safety, than no. Compare to a European roundabout, where the deflection to exit is similar as the one to enter

(https://i.ytimg.com/vi/FR5l48_h5Eo/maxresdefault.jpg)

In the Michigan example, they had to add a HAWK because clearly compliance at the crosswalk was minimal.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 30, 2019, 04:55:16 PM
Properly designed depends on what standard youre using.

If youre US highway metrics like "vehicles per hour", then yes, the straighter the better.

If your metric is safety, than no. Compare to a European roundabout, where the deflection to exit is similar as the one to enter
Problem is that to put pedestrian safety first you need to put roundabouts in spots with traffic low enough to sustain reduced roundabout performance. THis is where US engineering performs.. well, performs normally poor. There are many contradicting requirements which are supposed to be met - and one can expect to fail on all of them. You cannot have the cake and eat it too; but it is easy to have no cake and still be hungry.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on May 30, 2019, 05:37:46 PM
A problem with the 14 Mile & Orchard Lake roundabout is that the traffic signal north of the roundabout is only 200 feet away.  This causes traffic to routinely queue up through the roundabout.

(https://i.imgur.com/r87XR3x.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 30, 2019, 06:45:23 PM
You also have to remember that many of these systems, despite being on both sides of the carriageway, are fed by a common power conduit. One short upstream of the beacons, and neither one of them work.

That seems like it would be unusual, but I'll give you the benefit of the doubt. But consider this: how are we to say that the net-negative effects of an inoperable PTSWF sign are of greater significance than the net-positive effects of an operable PTSWF sign? Both in contrast to not having a sign at all.

I think you're making this a lot more complicated than it needs to be. Just let them flash constantly. What does it hurt? It also simplifies the wiring and programming needs. Having 24/7 flash and no sign has a better/safer driver default response than with the PTSWF. One could also say the part-time flash and sign is not necessary, as being prepared to possibly have to stop should be assumed with the Signal Ahead warning sign.

I don't fully understand the point of a constant flashing yellow light, with regards to warning of an upcoming signal. Signals should be fairly obvious, as long as the heads are placed adequately well. Plus, a constant flashing yellow light doesn't tell you anything about the state of the signal. On high-speed roads, which is really the only place where these are even remotely useful, it would be nice to know if you have to prepare to stop from 50 or 60 miles per hour.

The primary argument I see against PTSWF signs is that drivers speed up when they see them. I'm not going to question whether or not that's accurate, but here's another metric to consider: are there more accidents caused by speeding up to make a light, then there are because of drivers making a "poor decision" while in the dilemma zone? Such as slamming on the brakes, and causing a rear-end collision.

I'm not sure it's fair to say that I'm being pedantic or something. Well-engineered highways can easily be measured not just by how many cars they push through, but by how safe they are. There are positives and negatives to every decision. It's not black and white. A good engineer will consider every outcome, and the positives and negatives of each of those outcomes.

For the record, I wouldn't say that the jury is out on these types of signs. There are plenty of areas that use them, and justify them on account of improved safety.
Title: Re: Crash prone 'modern roundabouts'
Post by: ScottRAB on May 31, 2019, 01:44:22 PM


Here we are again. It’s the roundabout’s fault the woman was drunk and speeding.

With your logic there is no need to convert traffic signals to roundabouts in the first place.  When a drunk driver blows through a red light it's not the red lights fault they were drunk and speeding.  Why are we worried about fatal t-bone accidents at traffic signals when alcohol was a factor?  After all, you can't stop stupid. 

With the roundabout that dramatically minimizes the chances this lady would have plowed into someone else.

How?  A driver crossing her path in the roundabout is (roughly) no less at a 90° angle to the other driver than one crossing a stoplighted intersection.  I guess she was less likely to hit someone on the far side of the roundabout...

Modern roundabouts force drivers to slow down and change the angle of interaction.  It is no longer 90 degrees at a modern roundabout, but usually about 60 degrees. 
Modern Roundabouts are one of several proven road safety features (FHWA). 
The life saved may be your own.
https://safety.fhwa.dot.gov/provencountermeasures/roundabouts/
https://safety.fhwa.dot.gov/intersection/innovative/roundabouts/
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 31, 2019, 02:37:18 PM
Modern roundabouts force drivers to slow down and change the angle of interaction.

You're new, so we can forgive you.  But this has been hashed to death already.

Here is an example post. (https://www.aaroads.com/forum/index.php?topic=15546.msg2349926;topicseen#msg2349926)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 31, 2019, 03:20:14 PM
I wish we'd stop this notion of "force". You can't force drivers to go around in a circle, if they don't want to.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 31, 2019, 04:10:27 PM
Modern roundabouts force drivers to slow down and change the angle of interaction.  It is no longer 90 degrees at a modern roundabout, but usually about 60 degrees. 
Modern Roundabouts are one of several proven road safety features (FHWA). 
The life saved may be your own.
https://safety.fhwa.dot.gov/provencountermeasures/roundabouts/
https://safety.fhwa.dot.gov/intersection/innovative/roundabouts/
Oh, duckspeak... Something I was really missing... not.
Modern roundabout encourage slowdown when driver is in full control; making consequences worse when driver is not prepared or not acting (drunk, sleepy, inattentive, drives in reduced visibility, runaway car etc). Impact would no longer be 90 degree side, but vehicle will be pushed up by curbs, helping it to  roll-off or impact higher on cross traffic, creating potential of high level impact, for which most vehicles are not tested or certified.
Modern Roundabouts are great when not designed by idiots.
The life lost may be your own.

Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on May 31, 2019, 04:20:37 PM

A driver crossing her path in the roundabout is (roughly) no less at a 90° angle to the other driver than one crossing a stoplighted intersection.  I guess she was less likely to hit someone on the far side of the roundabout...

Modern roundabouts force drivers to slow down and change the angle of interaction.  It is no longer 90 degrees at a modern roundabout, but usually about 60 degrees. 

Let me try this again.  My post was in reply to a comment made about an news article shared by tradephoric.  Did you read that article?  In that article, it was stated that a drunk driver vaulted over the center of a roundabout and landed on the other side.  My point is that her vehicle–which apparently didn't undergo much deflection–was indeed at roughly a 90° angle to any vehicle crossing her immediate path.  Below is the specific roundabout at which this crash happened.  That ain't no 60° impact point.

(https://i.imgur.com/YoqILxe.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: ErmineNotyours on June 01, 2019, 12:10:12 AM
Flashing beacon at roundabout in Duvall, WA. (https://goo.gl/maps/oFmEUuZkGDQLpLHX6)
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on June 03, 2019, 01:56:19 AM
You also have to remember that many of these systems, despite being on both sides of the carriageway, are fed by a common power conduit. One short upstream of the beacons, and neither one of them work.

That seems like it would be unusual, but I'll give you the benefit of the doubt. But consider this: how are we to say that the net-negative effects of an inoperable PTSWF sign are of greater significance than the net-positive effects of an operable PTSWF sign? Both in contrast to not having a sign at all.

I think you're making this a lot more complicated than it needs to be. Just let them flash constantly. What does it hurt? It also simplifies the wiring and programming needs. Having 24/7 flash and no sign has a better/safer driver default response than with the PTSWF. One could also say the part-time flash and sign is not necessary, as being prepared to possibly have to stop should be assumed with the Signal Ahead warning sign.

I don't fully understand the point of a constant flashing yellow light, with regards to warning of an upcoming signal. Signals should be fairly obvious, as long as the heads are placed adequately well.

Based on the bolded statement, the advanced warning should not even be necessary then. And if the traffic signal uses LEDs, unless the intersection is at the end of a long, sweeping curve, you should be able to see the signal before you even reach the advanced warning sign.

Quote
Plus, a constant flashing yellow light doesn't tell you anything about the state of the signal. On high-speed roads, which is really the only place where these are even remotely useful, it would be nice to know if you have to prepare to stop from 50 or 60 miles per hour.

Why do you need to know this? If that was indeed true, it should be used on every rural railroad crossing warning sign as well. One of the points of posting the Signal Ahead warning sign is to indicate that the driver may need to prepare to stop. Meaning: You might want to take your foot off the gas and hover over the brake so you can react appropriately. Unless you're going uphill, (which would work in your favor anyway), momentum loss will be minimal. In any case, as I said above, with LED indications, the state of the signal is known before the motorist even reaches the sign, as long as the driver's head isn't buried in their smartphone.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 03, 2019, 07:50:54 AM
^There are some examples of "Prepare To Stop When Flashing" signs along high speed arterials in Metro Detroit.  They can definitely be useful to truckers to let them know when to let off the gas so they don't get stuck in the "dilemma zone".  You most often see this when the approaching light is obscured and/or when there is a steep downhill grade at the signal.

https://www.google.com/maps/@42.52658,-83.2852535,3a,75y,5.79h,90.72t/data=!3m6!1e1!3m4!1sC-LKWk2JpmHjJf0ZQxloQQ!2e0!7i16384!8i8192

https://www.google.com/maps/@42.505621,-83.3168609,3a,75y,311.39h,89.76t/data=!3m6!1e1!3m4!1s-yO0DtGscg9Qb9P6nmCMng!2e0!7i16384!8i8192

Here's a location that could really use an advanced flasher.  There is a sign at the top of the hill that states "SIGNAL AHEAD WATCH FOR STOPPED TRAFFIC" but it doesn't give drivers any advanced warning when the signal is going to change to red. 
https://www.google.com/maps/@42.7055439,-83.2426771,3a,75y,180.1h,86.94t/data=!3m6!1e1!3m4!1spJ2LL1OR31uawWNE16FNtQ!2e0!7i16384!8i8192
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on June 03, 2019, 08:39:49 AM
I don't fully understand the point of a constant flashing yellow light, with regards to warning of an upcoming signal. Signals should be fairly obvious, as long as the heads are placed adequately well.

Based on the bolded statement, the advanced warning should not even be necessary then. And if the traffic signal uses LEDs, unless the intersection is at the end of a long, sweeping curve, you should be able to see the signal before you even reach the advanced warning sign.

Here's an example of a signal that isn't seen from the normal distance of the sign. Plus, there's an overpass, and the light is located as one is going downhill.

https://goo.gl/maps/xFiQGnBsHzbDvTgVA

Otherside of the overpass: Still don't see the light.  https://goo.gl/maps/8nVnfqFxo8QkbLW88

Finally, as you moved around the curve: The light is now visible. https://goo.gl/maps/vB5J9wHBUt8GsP7FA

True, it would be more useful to have a 'Red Light When Flashing' type signage here, which they have at other places on the road, including just a mile or so away.  May have something to do with traffic volumes and such as well to determine what type of signage or beacon is warranted.

Quote
Plus, a constant flashing yellow light doesn't tell you anything about the state of the signal. On high-speed roads, which is really the only place where these are even remotely useful, it would be nice to know if you have to prepare to stop from 50 or 60 miles per hour.

50 mph is high speed?  Was this written by the IIHS?
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on June 03, 2019, 09:04:31 AM
There is a sign at the top of the hill that states "SIGNAL AHEAD WATCH FOR STOPPED TRAFFIC" but it doesn't give drivers any advanced warning when the signal is going to change to red
https://www.google.com/maps/@42.7055439,-83.2426771,3a,75y,180.1h,86.94t/data=!3m6!1e1!3m4!1spJ2LL1OR31uawWNE16FNtQ!2e0!7i16384!8i8192

Neither do the vast majority of traffic signals in the US. Heaven forbid a driver has to, gasp, pay attention. No warning? Last I saw, that was the whole reason why the yellow light was added to the traffic signal setup.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 03, 2019, 09:51:57 AM
Neither do the vast majority of traffic signals in the US. Heaven forbid a driver has to, gasp, pay attention. No warning? Last I saw, that was the whole reason why the yellow light was added to the traffic signal setup.

Just because there aren't advanced warning signs/flashers approaching the vast majority of traffic signals doesn't mean they are never warranted.  A gravel-hauler driver running up and down the road every day may realize they are approaching a traffic signal, but a static sign (or constant flashing beacon) won't tell them when that signal is about to turn red (which could be useful info as they are approaching the traffic signal cruising down a 10% downgrade at 50 mph with a loaded trailer).  I don't have a problem with having a handful of advanced warning flashers at traffic signals in a metro region of 4 million people, but apparently DaBigE doesn't like that. 
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on June 03, 2019, 11:47:59 AM
Neither do the vast majority of traffic signals in the US. Heaven forbid a driver has to, gasp, pay attention. No warning? Last I saw, that was the whole reason why the yellow light was added to the traffic signal setup.

Just because there aren't advanced warning signs/flashers approaching the vast majority of traffic signals doesn't mean they are never warranted.  A gravel-hauler driver running up and down the road every day may realize they are approaching a traffic signal, but a static sign (or constant flashing beacon) won't tell them when that signal is about to turn red (which could be useful info as they are approaching the traffic signal cruising down a 10% downgrade at 50 mph with a loaded trailer).  I don't have a problem with having a handful of advanced warning flashers at traffic signals in a metro region of 4 million people, but apparently DaBigE doesn't like that.

Surprise, surprise, you twist my words yet again. I didn't say they were never warranted. Approaches along horizontal curves? Likely needed. Vertical curves? Depends on the magnitude of the curve. On a straightaway with adequate sight distance? Shouldn't be needed, but would be a treatment to address higher than expected rear-end crash rates. Better? What I actually don't like is creating a nanny-state of drivers who are incapable of thinking for themselves because they only know how to act when told what to do. Don't know when/if a traffic light is going to change? Prepare for it. Did defensive driving go out the window with common sense? Worst case scenario, you loose a couple mph for a couple hundred feet.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 03, 2019, 11:00:01 PM
I don't fully understand the point of a constant flashing yellow light, with regards to warning of an upcoming signal. Signals should be fairly obvious, as long as the heads are placed adequately well.

Based on the bolded statement, the advanced warning should not even be necessary then. And if the traffic signal uses LEDs, unless the intersection is at the end of a long, sweeping curve, you should be able to see the signal before you even reach the advanced warning sign.

If there is a signal around a long, sweeping curve, certainly even the most well-placed signal will not do drivers any good. Unless the expectation is that drivers must proceed around a corner at such a stupidly-low speed as to be able to stop at a potential red light, drivers on high speed, sparsely-signalized roads should be able to proceed at-speed without needing to worry about a traffic light. The "prepare to stop when flashing" sign is very helpful in this scenario, as it permits drivers to focus more on other potential hazards, and not whether or not they'll need to suddenly make an emergency stop around the next bend.

Better? What I actually don't like is creating a nanny-state of drivers who are incapable of thinking for themselves because they only know how to act when told what to do. Don't know when/if a traffic light is going to change? Prepare for it. Did defensive driving go out the window with common sense? Worst case scenario, you loose a couple mph for a couple hundred feet.

We have to pander to that 1% of drivers who ruin it for the rest of us. Like those that push every single dilemma-zone situation, to the point where they consistently enter well after the yellow has expired (sometimes late enough to cause side-street drivers to delay movement).

Rant: The job of an engineer or designer is not to create situations where drivers have to put in a great deal of effort to avoid crashing. Fact is, at least in America, there are a lot of drivers who only drive because they have to, not because they want to. Those particular drivers likely have never heard of "defense driving". They don't expect lights to change. They don't even know why lights change. All they know is, they missed the light and now they're annoyed (or late). If you've ever driven with anyone who you'd categorize as someone who "doesn't like driving", they're probably the same people who consistently complain about everything on the road. Why? Because they don't understand how driving works. They don't know what a "stale green light" is; lights are either red, yellow, or green: green means go, yellow means "make a call", and red means stop. That's the extent of their knowledge for lights, other than "left turns yield" (which is still screwed up by fair number of drivers).

What's my point in all this? It's not completely pointless to offer drivers a hand. Most of them probably need it, anyhow.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on June 04, 2019, 08:58:05 AM
Rant: The job of an engineer or designer is not to create situations where drivers have to put in a great deal of effort to avoid crashing. Fact is, at least in America, there are a lot of drivers who only drive because they have to, not because they want to. Those particular drivers likely have never heard of "defense driving". They don't expect lights to change. They don't even know why lights change. All they know is, they missed the light and now they're annoyed (or late). If you've ever driven with anyone who you'd categorize as someone who "doesn't like driving", they're probably the same people who consistently complain about everything on the road. Why? Because they don't understand how driving works. They don't know what a "stale green light" is; lights are either red, yellow, or green: green means go, yellow means "make a call", and red means stop. That's the extent of their knowledge for lights, other than "left turns yield" (which is still screwed up by fair number of drivers).

Which also highlights how piss poor our driver's education is in the US. This is all stuff a good driver's education course should cover. I still have memories my old driver's ed teacher asking the question "is that green light stale?" He would do it before every traffic light we encountered. If I were king for a day, everyone would have to have training to the level of a CDL, at a minimum and would have to retest on a regular basis.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 04, 2019, 03:14:55 PM
Rant: The job of an engineer or designer is not to create situations where drivers have to put in a great deal of effort to avoid crashing. Fact is, at least in America, there are a lot of drivers who only drive because they have to, not because they want to. Those particular drivers likely have never heard of "defense driving". They don't expect lights to change. They don't even know why lights change. All they know is, they missed the light and now they're annoyed (or late). If you've ever driven with anyone who you'd categorize as someone who "doesn't like driving", they're probably the same people who consistently complain about everything on the road. Why? Because they don't understand how driving works. They don't know what a "stale green light" is; lights are either red, yellow, or green: green means go, yellow means "make a call", and red means stop. That's the extent of their knowledge for lights, other than "left turns yield" (which is still screwed up by fair number of drivers).

Which also highlights how piss poor our driver's education is in the US. This is all stuff a good driver's education course should cover. I still have memories my old driver's ed teacher asking the question "is that green light stale?" He would do it before every traffic light we encountered. If I were king for a day, everyone would have to have training to the level of a CDL, at a minimum and would have to retest on a regular basis.

Oh I know it. Our driver education is hilariously bad. Maybe not as bad as India, but complete shit compared to the UK, Australia, etc. Hell, Canada seems to have better education, by quite a bit. BC (ICBC) even requires those "L" and "N" stickers that you see in some other countries. Very comprehensive.

Problem is, the motorists lobbies will almost certainly push back, citing how reliant people are on cars, and how this is part of the "war on cars", that we can't expect people to operate to CDL-capacity, etc. All BS as far as I'm concerned, but that's the stand they'll take. They should be ignored, but, well, politics.
Title: Re: Crash prone 'modern roundabouts'
Post by: doorknob60 on June 04, 2019, 06:34:43 PM
WSDOT is building two new roundabouts near Camas (just north of the Columbia River) along WA-14. Construction started today (http://wsdot.wa.gov/news/2019/05/23/two-new-roundabouts-coming-sr-14-washougal). The two intersections are roughly at either end of this Maps link (https://www.google.com/maps/@45.5759382,-122.3466372,1375m/data=!3m1!1e3) (15 St/Washougal River Rd, and 32 St).

These are relatively simple one-lane roundabouts (with one extra lane at 32 St), but what is more worrisome for me, is that they're being built just east of a brand new freeway interchange (https://goo.gl/maps/xtK2kpAJWbDYhXf9A). WA-14 is basically a freeway or Super-2 from I-5 (16 miles away), all the way to this point. This would not be the first roundabout at the terminus of a freeway, but it doesn't seem like that great of an idea to me. WA-14 is either 55 or 60 from I-5, up to 15 St (the first roundabout).

I'm not trying to imply that a signal would absolutely be better. But I would assume that a signal, with a flashing "prepare to stop" message and rumble strips perpendicular to the lanes, would be better than a roundabout, as those really can sneak up on you, if you're not expecting them (which people may not be, after driving along 16 miles worth of divided highway).

(https://www.wsdot.wa.gov/sites/default/files/2016/10/26/SR14_AccessImprov_15th_Roundabout_510x324px.png) (https://www.wsdot.wa.gov/sites/default/files/2016/10/26/SR14_AccessImprov_32nd_Roundabout_510x324px.png)

I'm a fan of roundabouts generally (I used to live in Bend, so I'm very experienced to say the least), but that seems like a really bad place. I've driven on that section of SR-14 a handful of times, since I visit family in Trout Lake, WA a couple times a year usually. I always assumed they were planning on extending the freeway/super 2 through the rest of Washougal. This is a road where people are used to ~55 MPH free flowing traffic on both sides, so this seems like a mistake. The lights already there are not ideal, but can at least accommodate traffic at (or near) the speed limit most of the time.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on June 06, 2019, 10:17:52 AM
Well, besides causing crashes, apparently roundabouts are causing tornaders...er tornadoes: https://www.phillyvoice.com/pennsylvania-traffic-circles-causing-tornadoes-weather-2019/ (https://www.phillyvoice.com/pennsylvania-traffic-circles-causing-tornadoes-weather-2019/)  :hmmm:
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on June 06, 2019, 10:45:01 AM
Well, besides causing crashes, apparently roundabouts are causing tornaders...er tornadoes: https://www.phillyvoice.com/pennsylvania-traffic-circles-causing-tornadoes-weather-2019/ (https://www.phillyvoice.com/pennsylvania-traffic-circles-causing-tornadoes-weather-2019/)  :hmmm:

Now we know where tradephoric lives. :bigass:
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 06, 2019, 02:22:00 PM
Well, besides causing crashes, apparently roundabouts are causing tornaders...er tornadoes: https://www.phillyvoice.com/pennsylvania-traffic-circles-causing-tornadoes-weather-2019/ (https://www.phillyvoice.com/pennsylvania-traffic-circles-causing-tornadoes-weather-2019/)  :hmmm:

If you have watched any Nascar races you have probably heard Darrell Waltrip talking about the "vortex theory".  The theory goes that race cars racing around an oval track creates a "vortex" that repels approaching storms.  DW swears by it! 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 06, 2019, 02:55:59 PM
Quote
The segment picked up steam on social media Sunday, and then again Wednesday. Here's hoping the momentum from all those retweets doesn't start a tornado.

Well played, Mr Hermann. Well played....
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 17, 2019, 02:20:22 PM
A report from the Mid-Ohio Regional Planning Commission released in 2016 found that the Main Street and Cemetery roundabout (constructed in 2011) had the most reported accidents in Hilliard, 233, from 2013 through 2015.  Based on their report, the city of Hilliard approved a $160,000 contract with Burgess & Niple, the same company that originally designed the roundabout to begin with, to come up with solutions to reduce the high crash rate at that roundabout .  In March the city counsel approved a contract with Strawser Paving Co. for $544,000 to make modifications to the roundabouts along Main Street.  None of the changes listed in the article include eliminating circulating lanes of traffic so we will see how effective the changes will be. 

It must be nice working at Burgess & Niple, getting awarded a $160,000 contract to redesign a problem roundabout that they had originally designed years earlier.  And the firm didn't even come up with a design that eliminates circulating lanes inside the roundabouts, which has historically been the only long term fix to reducing the crash rates at these problem roundabouts.

Hilliard’s summer roadwork includes Main Street roundabouts
https://www.dispatch.com/news/20190611/hilliards-summer-roadwork-includes-main-street-roundabouts
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 17, 2019, 05:06:00 PM
And the firm didn't even come up with a design that eliminates circulating lanes inside the roundabouts, which has historically been the only long term fix to reducing the crash rates at these problem roundabouts.

If that has indeed been established by your own research in this thread, does the firm even know that's the case?
Title: Re: Crash prone 'modern roundabouts'
Post by: 6a on June 17, 2019, 06:39:42 PM
They’ve already started work in that area (I live in Hilliard) but I don’t know what good it would do to reduce the number of lanes in the roundabouts. Every road leading into them is 4 lanes; one of which (Cemetery) is a direct feed off I-270. I’ve never personally experienced any issue going through them, but stats are stats.

I have absolutely no citations to back this up, only word of mouth, but it was widely believed that when these roundabouts were designed, school bus traffic wasn’t taken into consideration.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 17, 2019, 10:40:53 PM
I have absolutely no citations to back this up, only word of mouth, but it was widely believed that when these roundabouts were designed, school bus traffic wasn’t taken into consideration.

Are there a lot of school buses going through that area? Even more than usual should be outweighed by the sheer number of cars. Unless the school buses are stopping immediately after exiting the roundabout. In that case, roundabouts are pretty annoying, as stopped cars tend to lock up the roundabout (as drivers seem to be less attentive to box-blocking at roundabouts compared to signals).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 18, 2019, 08:36:40 AM
I have absolutely no citations to back this up, only word of mouth, but it was widely believed that when these roundabouts were designed, school bus traffic wasn’t taken into consideration.

Are there a lot of school buses going through that area? Even more than usual should be outweighed by the sheer number of cars. Unless the school buses are stopping immediately after exiting the roundabout. In that case, roundabouts are pretty annoying, as stopped cars tend to lock up the roundabout (as drivers seem to be less attentive to box-blocking at roundabouts compared to signals).
Pretty often, drivers are not supposed to see what is going on on the other side - and that is done on purpose. It is fairly easy to find yourself in a situation when you don't see a problem before it is too late.
Another fine print issue is what "yield to traffic already in a circle" means. A  long and/or heavy vehicle which cannot accelerate like a car can easily end up blocking traffic even with ample space upstream. Not to mention that they also need to catch the smallest workable gap, meaning they are not too shy about blocking upstream traffic.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 18, 2019, 12:02:46 PM
And the firm didn't even come up with a design that eliminates circulating lanes inside the roundabouts, which has historically been the only long term fix to reducing the crash rates at these problem roundabouts.

If that has indeed been established by your own research in this thread, does the firm even know that's the case?

Here are some of the changes planned at the Hilliard roundabouts that are mentioned in the article. 

Quote
-Reshaping the central traffic island by installing temporary curbs.

-The traffic “islands”  in the roundabout will be modified.

-More changes are planned at Main and Cemetery, including resurfacing, revised markings, overhead lane-control signs and “Yield to both lanes”  signs.

-The flashing LED-bordered yield signs will be placed in the center island

Even if these changes help reduce the crash rate, it's hard to pinpoint what change actually made the difference.  Take the 14th Street and Superior roundabout in Lincoln as an example.  The 3x2 roundabout had a very high crash rate so the city downsized the roundabout to a 2x1 roundabout and the site distance was limited by constructing chain link fence running along the splitter islands with slats in the medians.  The result was a dramatic drop in crashes with the crash rate dropping below pre-roundabout levels.  Now a lot of the success was attributed to the fencing installed along the splitter islands to limit drivers views. 

IMO, the fact that the Lincoln roundabout was dramatically downsized (from a 3x2 to a 2x1 roundabout) was the reason there was such a dramatic reduction in crashes and the fencing had little to no effect.  The M-5 and Pontiac Trail roundabout is a 3x2 roundabout in Commerce Michigan and it too had fencing installed along the splitter islands in an attempt to reduce the high number of crashes occurring, but unlike the Lincoln roundabout the configuration of the roundabout wasn't touched (remained a 3x2).  When comparing the crashes from the 6 months before the fencing to the 6 months after, the crash rate was identical.

Whenever i've seen a dramatic drop in crashes at these problem roundabouts, it seems to always include a downsizing of the roundabout.  However, when the roundabout isn't downsized and other "safety features" are tried, it's often ineffective at reducing the crash rate.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 18, 2019, 02:22:12 PM
That still doesn't address the actual question part of my question:  "does the firm even know that's the case?"  Is anyone outside this forum aware of the statistical correlations you've been drawing?
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on June 18, 2019, 02:32:12 PM
That still doesn't address the actual question part of my question:  "does the firm even know that's the case?"  Is anyone outside this forum aware of the statistical correlations you've been drawing?

I would love to see a peer review of his data done by actual traffic engineers.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 18, 2019, 03:27:05 PM
I would love to see a peer review of his data done by actual traffic engineers.

Derek Leuer and John Hourdos out of Minnesota have done a lot of research specific to the safety of multi-lane roundabouts.  Based on their research there has been a 6% increase in total injury crashes at the full multi-lane roundabouts analyzed in Minnesota.  Here is a link to their study.  This study is unique in that it analyzes each type of roundabout separately and splits it up by single-lane, unbalanced multi-lane, and full multi-lane. 
 
A Study of the Traffic Safety at Roundabouts in Minnesota
http://www.dot.state.mn.us/trafficeng/safety/docs/roundaboutstudy.pdf

The good news is that Type-A crashes dropped from 3 to 0, a 100% reduction in serious injuries.  But if you plug in ALL the numbers into FHWA’s comprehensive crash costs by injury severity level it’s clear that the dual-lane roundabouts had a higher social cost than the intersections they replaced.

(https://i.imgur.com/D77VC6z.png)
http://www.dot.state.mn.us/trafficeng/safety/docs/roundaboutstudy.pdf

BEFORE ROUNDABOUT CRASH COSTS = $4,882,600
Fatality (K)           0 X $4,008,900 = $0
Disabling Injury (A)   3 X  $216,000 = $648,000
Evident Injury (B)   15 X $79,000 = $1,185,000
Possible Injury (C)   46 X $44,900 = $2,065,400
PDO (O)          133 X $7,400 =  $984,200

AFTER ROUNDABOUT CRASH COSTS = $6,546,900
Fatality (K)           0 X $4,008,900 = $0
Disabling Injury (A)   0 X  $216,000 = $0
Evident Injury (B)   15 X $79,000 = $1,185,000
Possible Injury (C)   53 X $44,900 = $2,379,700
PDO (O)          403 X $7,400 =  $2,982,200
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on June 18, 2019, 09:50:11 PM
So a reduction in actual disabling injuries, and an increase in what might be injuries. That's somehow worse than before?
Title: Re: Crash prone 'modern roundabouts'
Post by: TheHighwayMan394 on June 18, 2019, 09:59:28 PM
So a reduction in actual disabling injuries, and an increase in what might be injuries. That's somehow worse than before?

It’s like we’re trying to find the magic number of how much money a life is worth.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 18, 2019, 10:09:55 PM
So a reduction in actual disabling injuries, and an increase in what might be injuries. That's somehow worse than before?

It’s like we’re trying to find the magic number of how much money a life is worth.
Low values are $2M, high are $10M. Nothing magic, pretty well-known stuff.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 19, 2019, 01:46:38 PM
So a reduction in actual disabling injuries, and an increase in what might be injuries. That's somehow worse than before?

That's correct according to the FHWA.  If you really want to dive deep into how they come up with the numbers you should read the FHWA publication "Crash Costs for Highway Safety Analysis". 

https://safety.fhwa.dot.gov/hsip/docs/fhwasa17071.pdf

A few posts ago you are questioning the data i'm citing throughout this thread and wanted "real traffic engineers" to do a peer review of it.  Now i cite you a study looking at the safety of dual-lane roundabouts (which is a running theme throughout this thread) and now you seem to be questioning the FHWA's data too.  At this point i don't know what to tell you.

EDIT:  When i say "that is correct according to the FHWA" i'm speaking to this specific example of calculating the social crash costs of dual-lane roundabouts in Minnesota.  If you do the same analysis of single-lane roundabouts in Kansas, the roundabouts would probably fair quite well. 
Title: Re: Crash prone 'modern roundabouts'
Post by: 6a on June 19, 2019, 05:49:41 PM
I have absolutely no citations to back this up, only word of mouth, but it was widely believed that when these roundabouts were designed, school bus traffic wasn’t taken into consideration.

Are there a lot of school buses going through that area? Even more than usual should be outweighed by the sheer number of cars. Unless the school buses are stopping immediately after exiting the roundabout. In that case, roundabouts are pretty annoying, as stopped cars tend to lock up the roundabout (as drivers seem to be less attentive to box-blocking at roundabouts compared to signals).

It’s just the sheer number of schools in that immediate area. Each with its corresponding bus traffic. I’ve circled schools in blue, the roundabouts in question in red.

(https://uploads.tapatalk-cdn.com/20190619/1e7baffe5af8911362270cb39a187e38.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on June 19, 2019, 08:42:51 PM
So a reduction in actual disabling injuries, and an increase in what might be injuries. That's somehow worse than before?

That's correct according to the FHWA.  If you really want to dive deep into how they come up with the numbers you should read the FHWA publication "Crash Costs for Highway Safety Analysis". 

https://safety.fhwa.dot.gov/hsip/docs/fhwasa17071.pdf

A few posts ago you are questioning the data i'm citing throughout this thread and wanted "real traffic engineers" to do a peer review of it.  Now i cite you a study looking at the safety of dual-lane roundabouts (which is a running theme throughout this thread) and now you seem to be questioning the FHWA's data too.  At this point i don't know what to tell you.

EDIT:  When i say "that is correct according to the FHWA" i'm speaking to this specific example of calculating the social crash costs of dual-lane roundabouts in Minnesota.  If you do the same analysis of single-lane roundabouts in Kansas, the roundabouts would probably fair quite well.

Well, I guess I'm just confused about how it is they're valuing these different injuries. I'll take a look at that report, thanks.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 01, 2019, 07:49:15 AM
Here is a list of the 10 most dangerous roundabouts in Michigan for 2018.  Total crashes ranged from 49 crashes (Lee Road at Whitmore Lake Road roundabout) to 144 crashes (Orchard Lake Road at W 14 Mile Road roundabout). 

These are the top 10 most dangerous roundabouts in Michigan
https://www.wxyz.com/news/these-are-the-top-10-most-dangerous-roundabouts-in-michigan
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 01, 2019, 09:44:57 AM
Here is a list of the 10 most dangerous roundabouts in Michigan for 2018.  Total crashes ranged from 49 crashes (Lee Road at Whitmore Lake Road roundabout) to 144 crashes (Orchard Lake Road at W 14 Mile Road roundabout). 

These are the top 10 most dangerous roundabouts in Michigan
https://www.wxyz.com/news/these-are-the-top-10-most-dangerous-roundabouts-in-michigan
Proper way to present these news would be comparing with 10 most dangerous conventional intersections, or trying to normalize that per traffic counts and acceptable numbers (5 per million, if I remember correctly?) - or anything else to put numbers in context...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 12, 2019, 02:27:44 PM
The IIHS published a report looking at the long-term crash trends at single and double-lane roundabouts in Washington State.  They concluded that annual crash counts declined "significantly" by 8.8% at double-lane roundabouts and increased nonsignificantly over time at single-lane roundabouts.  Here is a link to the study:

Long-term crash trends at single-lane and double-lane roundabouts in Washington State
https://www.iihs.org/api/datastoredocument/bibliography/2180
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 12, 2019, 03:02:50 PM
The IIHS published a report looking at the long-term crash trends at single and double-lane roundabouts in Washington State.  They concluded that annual crash counts declined "significantly" by 8.8% at double-lane roundabouts and increased nonsignificantly over time at single-lane roundabouts.  Here is a link to the study:

Better link: https://www.iihs.org/news/detail/safety-at-two-lane-roundabouts-improves-over-time-new-study-shows

Are you going to request a copy? Would be nice to know if the crash rates, after so many years, are more or less than the intersection these roundabouts replaced.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 12, 2019, 03:25:00 PM
Are you going to request a copy? Would be nice to know if the crash rates, after so many years, are more or less than the intersection these roundabouts replaced.

That is the real question.  If you look back at the State & Ellsworth roundabout, the very first roundabout discussed on this thread, it has seen similar crash reductions to that IIHS report.  But the roundabout still had 123 crashes last year which is 6x higher than the pre-roundabout condition.  Also, after the initial drop in crashes between year 1 and year 2, the total number of crashes has appeared to have plateaued.  To me the IIHS study is just trying to put lipstick on a pig by saying "hey look, double-lane roundabouts are seeing 9% annual crash reductions!".   

(https://i.imgur.com/KDzw37p.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 12, 2019, 03:58:31 PM
The IIHS published a report looking at the long-term crash trends at single and double-lane roundabouts in Washington State.  They concluded that annual crash counts declined "significantly" by 8.8% at double-lane roundabouts and increased nonsignificantly over time at single-lane roundabouts.  Here is a link to the study:

Better link: https://www.iihs.org/news/detail/safety-at-two-lane-roundabouts-improves-over-time-new-study-shows

Are you going to request a copy? Would be nice to know if the crash rates, after so many years, are more or less than the intersection these roundabouts replaced.
Paper is not published yet; but looks like it will be an open access one once it goes through.
I do remember a paper from the same authors (on Boston lowering speed limit 30 -> 25 ); back then I was unimpressed with their data processing.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 12, 2019, 04:09:48 PM
And since my fishing expedition have started, here are some catches:
Master thesis on roundabouts in AZ: https://repository.asu.edu/attachments/170314/content/Souliman_asu_0010N_15713.pdf
Single lane ones are cool, double lanes significantly increase crash rates with some decrease in injuries.

https://www.tac-atc.ca/sites/default/files/conf_papers/weber_p_-_solutions_to_driver_errors_at_multi-lane_roundabouts.pdf - how to make roundabouts safer. I like their first suggestion:
Quote
A single-lane instead of a multi-lane roundabout

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 12, 2019, 04:27:40 PM
https://www.tac-atc.ca/sites/default/files/conf_papers/weber_p_-_solutions_to_driver_errors_at_multi-lane_roundabouts.pdf - how to make roundabouts safer. I like their first suggestion:
Quote
A single-lane instead of a multi-lane roundabout

Two suggestions I also like:

1) higher entry angles, so entry into roundabouts is more of a right turn. I can understand failing to yield when you can just drive straight across the roundabout, but if it becomes a sharp-right, and then a gradual left turn, there might be better safety numbers.

2) circulatory lines be removed or not installed. The paper suggests that the lines make roundabouts appear as having four (or more) individual intersections, and that removing the markings make the roundabouts appear as one large intersection, increasing driver hesitation. Makes total sense to me, even if it is counter-intuitive relative to typical North American marking practices.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 12, 2019, 05:03:05 PM
https://www.tac-atc.ca/sites/default/files/conf_papers/weber_p_-_solutions_to_driver_errors_at_multi-lane_roundabouts.pdf - how to make roundabouts safer. I like their first suggestion:
Quote
A single-lane instead of a multi-lane roundabout

Two suggestions I also like:

1) higher entry angles, so entry into roundabouts is more of a right turn. I can understand failing to yield when you can just drive straight across the roundabout, but if it becomes a sharp-right, and then a gradual left turn, there might be better safety numbers.

2) circulatory lines be removed or not installed. The paper suggests that the lines make roundabouts appear as having four (or more) individual intersections, and that removing the markings make the roundabouts appear as one large intersection, increasing driver hesitation. Makes total sense to me, even if it is counter-intuitive relative to typical North American marking practices.

Basically reduce throughput to improve safety. As traffic totals are not very elastic, for higher traffic cases this means deflecting traffic to other intersections (if possible); or creating backups.
So yes, looks like roundabouts are great in cases of low traffic, replacing 2-way stop. Over here in NY they are considered as high traffic solution for complex intersections. See why I don't like them? 
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on July 12, 2019, 05:03:50 PM
Driver hesitation = driver confusion.  That doesn't sound like a good thing.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 12, 2019, 06:06:23 PM
Driver hesitation = driver confusion.  That doesn't sound like a good thing.
welcome to The Brave Roundabout World.
Drivers must hesitate before entering the circulation.
Drivers should not see what is on the other side.
Ignorance Is Strength.
War is Peace.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 12, 2019, 06:57:26 PM
Driver hesitation = driver confusion.  That doesn't sound like a good thing.
welcome to The Brave Roundabout World.
Drivers must hesitate before entering the circulation.
Drivers should not see what is on the other side.
Ignorance Is Strength.
War is Peace.

Right. Some of the tactics seem (as I said) counter-intuitive, but a confused/hesitant driver is usually one that is slower and more observant. Last I checked, confused drivers weren't usually the ones flying up the right lane going 20 over the limit! Of course, slow driving is not always safe, but everyone (even confident drivers) have to slow down at a roundabout (assuming they see it coming), so that differential in speed is less of a concern.

This confused/hesitant tactic has been in place across Western Washington for decades. Many of our urban two-lane intersections are unsigned/unmarked. Drivers basically approach each one with hesitation; you don't stop unless necessary, but you slow down and quickly glance before moving on.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 12, 2019, 07:37:39 PM
Driver hesitation = driver confusion.  That doesn't sound like a good thing.
welcome to The Brave Roundabout World.
Drivers must hesitate before entering the circulation.
Drivers should not see what is on the other side.
Ignorance Is Strength.
War is Peace.

Right. Some of the tactics seem (as I said) counter-intuitive, but a confused/hesitant driver is usually one that is slower and more observant. Last I checked, confused drivers weren't usually the ones flying up the right lane going 20 over the limit! Of course, slow driving is not always safe, but everyone (even confident drivers) have to slow down at a roundabout (assuming they see it coming), so that differential in speed is less of a concern.

This confused/hesitant tactic has been in place across Western Washington for decades. Many of our urban two-lane intersections are unsigned/unmarked. Drivers basically approach each one with hesitation; you don't stop unless necessary, but you slow down and quickly glance before moving on.

At which point its a good idea to stop and think: what is the purpose? Why are we doing whatever we're doing?
The ultimate goal of road design is, from my perspective, is to move traffic safely, efficiently, without undue stress. There are other factors, like emergency vehicle access, but lets not go into that for now.
So, roundabouts bring:
-mixed results in terms of safety
-throughput? My impression is that it is reduced compared to alternatives
-now we need to cut throughput down even further to improve safety
-we need to increase the level of stress for safety at a roundabout (and whatever ripple effects result from that; the stressed driver is the bad driver)
-we lose intersection scalability; sort of OK in NY as the state seems to be planning for decline

And.. did we gain anything, other than a happy contractor with a great construction contract?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 13, 2019, 01:30:30 PM
And.. did we gain anything, other than a happy contractor with a great construction contract?

I'm not even sure if they're that great. One major benefit of the roundabout is the (usually) cheaper construction cost.

The ultimate goal of road design is, from my perspective, is to move traffic safely, efficiently, without undue stress. There are other factors, like emergency vehicle access, but lets not go into that for now.
So, roundabouts bring:
-mixed results in terms of safety
-throughput? My impression is that it is reduced compared to alternatives
-now we need to cut throughput down even further to improve safety
-we need to increase the level of stress for safety at a roundabout (and whatever ripple effects result from that; the stressed driver is the bad driver)
-we lose intersection scalability; sort of OK in NY as the state seems to be planning for decline

(https://media1.giphy.com/media/3oriffSiqReMsR48py/giphy.gif)



I do think roundabouts work well in areas with lots of medians. Never have been a big fan of U-turns at signals, as they limit the placement of right-turn overlap/filter arrows.
Title: Re: Crash prone 'modern roundabouts'
Post by: mrsman on July 14, 2019, 10:42:32 AM
https://www.tac-atc.ca/sites/default/files/conf_papers/weber_p_-_solutions_to_driver_errors_at_multi-lane_roundabouts.pdf - how to make roundabouts safer. I like their first suggestion:
Quote
A single-lane instead of a multi-lane roundabout

Two suggestions I also like:

1) higher entry angles, so entry into roundabouts is more of a right turn. I can understand failing to yield when you can just drive straight across the roundabout, but if it becomes a sharp-right, and then a gradual left turn, there might be better safety numbers.

2) circulatory lines be removed or not installed. The paper suggests that the lines make roundabouts appear as having four (or more) individual intersections, and that removing the markings make the roundabouts appear as one large intersection, increasing driver hesitation. Makes total sense to me, even if it is counter-intuitive relative to typical North American marking practices.


I think this is the proper approach.  If all of your entry roads are single lane (inbound direction), then a single lane roundabout is great.  It is reasonably safe.  It will also cause less delay than an all-way stop of signalized approach, especially if you are in a jurisdiction that will contemplate left turn signals.  And as said by others, the roundabout will take care of any left turn and u-turn movements.  But in no event should they be used in a pedestrian heavy area.

However, the multi-lane roundabouts are crash prone.  There are simply too much traffic to allow for the flow into the roundabout.  The only solution in this case would be a regular signalized intersection or a signalized traffic circle.

Signalized traffic circles are safe, but they are no picnic traffic-wise.  Usually only done in very busy areas where there are more than 4 directions coming to meet at a point.  (Think Columbus Circle in NYS or Dupont Circle in Washington DC).  The only benefit over a regular intersection, is that there is no need for separate phases for left turns.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on July 14, 2019, 03:39:50 PM
i wish this thread would die, I regret posting in it, now i'm stuck with the notifications  :banghead:
Title: Re: Crash prone 'modern roundabouts'
Post by: mrsman on July 14, 2019, 05:40:23 PM
The thread will only die when multi-lane roundabouts die.

Nexus 5X

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 15, 2019, 07:18:36 AM
The Veterans Memorial Dr and Greenwich Ave roundabout (https://www.google.com/maps/@41.7002966,-71.4605747,3a,48.8y,46.56h,94.48t/data=!3m7!1e1!3m5!1sPCW0DIJfW9l8a3sIaTdXPw!2e0!6s%2F%2Fgeo3.ggpht.com%2Fcbk%3Fpanoid%3DPCW0DIJfW9l8a3sIaTdXPw%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D79.516525%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656) in Warwick may be one of the most dangerous roundabouts in the country.  It's a full 2x2 roundabout with a large retaining wall in the central island and over the weekend a police officer crashed into the retaining wall and suffered several injuries.  The officer's name hasn't been released and no word yet if it's one of the LivePD officers out of Warwick.

Warwick police officer injured when SUV crashes at roundabout
https://www.providencejournal.com/news/20190714/warwick-police-officer-injured-when-suv-crashes-at-roundabout
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 16, 2019, 10:58:44 AM
I shared this in another thread but maybe these roundabout interchange designs would work well.  Would you still consider these roundabouts?


Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on July 16, 2019, 01:57:54 PM
No.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 16, 2019, 03:48:37 PM
I shared this in another thread but maybe these roundabout interchange designs would work well.  Would you still consider these roundabouts?

https://www.youtube.com/watch?v=W8k1acLeK7E

https://www.youtube.com/watch?v=zVcOUY6Zs7k

Seems like you could get the same benefits by having a regular left-side merge lane (https://goo.gl/maps/iiuDLSLjys3a91pB8). There could still be a yield sign for the off-ramp, assuming decent sight-lines.

Not sure your models fully take into account the slowdowns that would occur approaching the apex of the roundabout, as traffic along the arterial swings right, and then back left. They wouldn't have to yield, but they'd have to slow down to a reasonable speed. Seems like an annoyance along an otherwise high-speed arterial.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 16, 2019, 05:31:38 PM

Not sure your models fully take into account the slowdowns that would occur approaching the apex of the roundabout,
There will be no slowdowns, there will be full speed t-bones. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on July 16, 2019, 08:16:10 PM

Not sure your models fully take into account the slowdowns that would occur approaching the apex of the roundabout,

There will be no slowdowns, there will be full speed t-bones. 

Indeed, east-west traffic doesn't even yield at the supposed roundabouts.  Basically, it's just a glorified version of what jakeroot linked to.

Not a roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 16, 2019, 09:09:51 PM
Indeed, east-west traffic doesn't even yield at the supposed roundabouts.  Basically, it's just a glorified version of what jakeroot linked to.

Not a roundabout.


Teardrop roundabouts don't require traffic along the arterial to yield at the roundabout (specifically traffic along the arterial traveling away from the overpass/underpass and heading towards the roundabout... i hope that made sense!).  Here is a roundabout interchange that Calgary is proposing that is essentially the same design that i posted except that off-ramp traffic exiting the roundabout isn't merging onto the arterial street.

(https://www.calgary.ca/Transportation/TI/PublishingImages/Road-projects/14-St-NW-Stoney-Trail-Interchange-design-2048px.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 16, 2019, 10:09:59 PM
Indeed, east-west traffic doesn't even yield at the supposed roundabouts.  Basically, it's just a glorified version of what jakeroot linked to.

Not a roundabout.


Teardrop roundabouts don't require traffic along the arterial to yield at the roundabout (specifically traffic along the arterial traveling away from the overpass/underpass and heading towards the roundabout... i hope that made sense!).  Here is a roundabout interchange that Calgary is proposing that is essentially the same design that i posted except that off-ramp traffic exiting the roundabout isn't merging onto the arterial street.

(https://www.calgary.ca/Transportation/TI/PublishingImages/Road-projects/14-St-NW-Stoney-Trail-Interchange-design-2048px.jpg)
Parts of traffic pattern along the bottom segment of the tear are fully equivalent to a half of  2x2 roundabout. Given the speeds involved, I expect crash rate along the lines of a regular 2x2  roundabout (or worse).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 17, 2019, 08:34:25 AM
With some minor tweaks that Calgary interchange could look something like this.  I only modeled half of the interchange but the other half would basically be a mirror copy.  One advantage is that traffic entering the freeway doesn't have to circulate through any roundabouts.  The question is would one lane of free-flowing arterial traffic have the same capacity of two-lanes of traffic that has to yield at the roundabout? 

Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on July 17, 2019, 12:13:35 PM
I was just in Aruba, and thyve been adding a bunch of dutch-style roundabouts to their major roads and highways (makes sense, theyre part of the Netherlands). Went through 5 or 6 on their main highway, which is 80kph (50mph). The speeds slwos to 60 and then 40 as you near the roundabout.

Whats interesting is that there are concrete curbs between lanes. No confusion.

This made navigating even the 3 lane roundabout easy. You just stay in your lane, and you cant get out.

Island is loaded up with American tourists, and I didnt see any issues.


The Veterans Memorial Dr and Greenwich Ave roundabout (https://www.google.com/maps/@41.7002966,-71.4605747,3a,48.8y,46.56h,94.48t/data=!3m7!1e1!3m5!1sPCW0DIJfW9l8a3sIaTdXPw!2e0!6s%2F%2Fgeo3.ggpht.com%2Fcbk%3Fpanoid%3DPCW0DIJfW9l8a3sIaTdXPw%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D79.516525%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656) in Warwick may be one of the most dangerous roundabouts in the country.  It's a full 2x2 roundabout with a large retaining wall in the central island and over the weekend a police officer crashed into the retaining wall and suffered several injuries.  The officer's name hasn't been released and no word yet if it's one of the LivePD officers out of Warwick.

Warwick police officer injured when SUV crashes at roundabout
https://www.providencejournal.com/news/20190714/warwick-police-officer-injured-when-suv-crashes-at-roundabout

That looks dangerous. No deflection on entrance or exit.

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 17, 2019, 01:17:38 PM
With some minor tweaks that Calgary interchange could look something like this.  I only modeled half of the interchange but the other half would basically be a mirror copy.  One advantage is that traffic entering the freeway doesn't have to circulate through any roundabouts.  The question is would one lane of free-flowing arterial traffic have the same capacity of two-lanes of traffic that has to yield at the roundabout? 


So what exactly is your point? That uncontrolled high speed intersection can be made safe? With 2 lanes intersecting another 2 lanes?
It will if traffic is about 2-3 vehicles a minute in each direction. Anything above that is a bad design.
Think rural highways intersection controlled by a single yield sign as the baseline.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 17, 2019, 01:46:00 PM
So what exactly is your point? That uncontrolled high speed intersection can be made safe? With 2 lanes intersecting another 2 lanes?
It will if traffic is about 2-3 vehicles a minute in each direction. Anything above that is a bad design.
Think rural highways intersection controlled by a single yield sign as the baseline.


It's not that unusual to have two lanes of traffic merge back down to 1 shortly after exiting a roundabout.  Here's an example of this at a busy roundabout with an AADT of over 50,000 (definitely not just 2-3 vehicles per minute).  It handles it.  While this roundabout does have a high crash rate it isn't specific to the merging traffic.

https://www.google.com/maps/@42.5546443,-83.447316,137m/data=!3m1!1e3
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on July 17, 2019, 02:27:36 PM
I was just in Aruba, and thyve been adding a bunch of dutch-style roundabouts to their major roads and highways (makes sense, theyre part of the Netherlands). Went through 5 or 6 on their main highway, which is 80kph (50mph). The speeds slwos to 60 and then 40 as you near the roundabout.

Whats interesting is that there are concrete curbs between lanes. No confusion.

This made navigating even the 3 lane roundabout easy. You just stay in your lane, and you cant get out.

Island is loaded up with American tourists, and I didnt see any issues.


The Veterans Memorial Dr and Greenwich Ave roundabout (https://www.google.com/maps/@41.7002966,-71.4605747,3a,48.8y,46.56h,94.48t/data=!3m7!1e1!3m5!1sPCW0DIJfW9l8a3sIaTdXPw!2e0!6s%2F%2Fgeo3.ggpht.com%2Fcbk%3Fpanoid%3DPCW0DIJfW9l8a3sIaTdXPw%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D79.516525%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656) in Warwick may be one of the most dangerous roundabouts in the country.  It's a full 2x2 roundabout with a large retaining wall in the central island and over the weekend a police officer crashed into the retaining wall and suffered several injuries.  The officer's name hasn't been released and no word yet if it's one of the LivePD officers out of Warwick.

Warwick police officer injured when SUV crashes at roundabout
https://www.providencejournal.com/news/20190714/warwick-police-officer-injured-when-suv-crashes-at-roundabout

That looks dangerous. No deflection on entrance or exit.



I think you're too close to the roundabout.  GSV'ing back a little bit you can easily make out the deflection approaching the roundabout.  https://goo.gl/maps/qMdVZ4nVQCvF3wXLA  There isn't much deflection exiting the roundabout, but that's not extremely necessary either, and increases the visibility of pedestrians in the walkway.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on July 17, 2019, 03:01:17 PM
I was just in Aruba, and thyve been adding a bunch of dutch-style roundabouts to their major roads and highways (makes sense, theyre part of the Netherlands). Went through 5 or 6 on their main highway, which is 80kph (50mph). The speeds slwos to 60 and then 40 as you near the roundabout.

Whats interesting is that there are concrete curbs between lanes. No confusion.

This made navigating even the 3 lane roundabout easy. You just stay in your lane, and you cant get out.

Island is loaded up with American tourists, and I didnt see any issues.


The Veterans Memorial Dr and Greenwich Ave roundabout (https://www.google.com/maps/@41.7002966,-71.4605747,3a,48.8y,46.56h,94.48t/data=!3m7!1e1!3m5!1sPCW0DIJfW9l8a3sIaTdXPw!2e0!6s%2F%2Fgeo3.ggpht.com%2Fcbk%3Fpanoid%3DPCW0DIJfW9l8a3sIaTdXPw%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D79.516525%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656) in Warwick may be one of the most dangerous roundabouts in the country.  It's a full 2x2 roundabout with a large retaining wall in the central island and over the weekend a police officer crashed into the retaining wall and suffered several injuries.  The officer's name hasn't been released and no word yet if it's one of the LivePD officers out of Warwick.

Warwick police officer injured when SUV crashes at roundabout
https://www.providencejournal.com/news/20190714/warwick-police-officer-injured-when-suv-crashes-at-roundabout

That looks dangerous. No deflection on entrance or exit.



I think you're too close to the roundabout.  GSV'ing back a little bit you can easily make out the deflection approaching the roundabout.  https://goo.gl/maps/qMdVZ4nVQCvF3wXLA  There isn't much deflection exiting the roundabout, but that's not extremely necessary either, and increases the visibility of pedestrians in the walkway.

I dont think that deflection point makes much sense. Its too early, and actually makes the crosswalk harder to see.

Theres no streetview in Aruba, and with the disclaimer that Ive never driven in mainland Netherlands, their roundabouts had very steep entrance and exit points - youre literally turning on and off.

https://goo.gl/maps/UQkkkURo5k5BpgXv6

Made it seem safer from my experience.

In the US ones, drivers just gun it.
Title: Re: Crash prone 'modern roundabouts'
Post by: mrsman on July 17, 2019, 03:18:43 PM
Agreed on those points.

The Dutch roundabout you linked to is single lane and has a wide circumference.  For drivers, it has the feel of yielding (or even stopping) to make a right turn and then taking it to where you want.  Reasonably safe. 


The problem with many of the ones  in the US, is that by altering the geometry, the circumference, and the number of lanes, you basically are dealing with a manuever of handling 4 closely spaced one-way intersections.  (I.e. a town center intersection but where everything is really close.)  You yield to the first intersection and then you have the right of way in the others.  But the problem deals with that you don't know when it is safe, because you may misjudge if traffic on your left will exit or go straight or continue around the roundabout.*  And the straight move isn't such a great deflection, so some traffic isn't even adequately slowing down.

IMO, if traffic can be narrowed to single lane on all approaches, a roundabout could be an option that will eliminate delays from traffic signals.  if it doesn't and you need multi-lane, you also likely need a traffic signal.


* To some extent, you experience similar problems on multi-lane 4-way stop corners.  When those are busy, the only way of being safe is keeping track of which direction got to the intersection first.  But it is harder to do that for multi-lane approaches.  IMO, if a road is busy enough for multiple lanes, it's busy enough to require traffic signals.  If it isn't busy enough, then narrow the road.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on July 17, 2019, 09:15:24 PM



Not sure your models fully take into account the slowdowns that would occur approaching the apex of the roundabout,

There will be no slowdowns, there will be full speed t-bones. 

Indeed, east-west traffic doesn't even yield at the supposed roundabouts.  Basically, it's just a glorified version of what jakeroot linked to.

Not a roundabout.

Teardrop roundabouts don't require traffic along the arterial to yield at the roundabout (specifically traffic along the arterial traveling away from the overpass/underpass and heading towards the roundabout... i hope that made sense!).

A teardrop interchange, in my opinion, is just a single squished roundabout interchange–not a pair of roundabouts.  Take a huge circle, squish the middle in, and you end up with two teardrops.  With that in mind, traffic on the arterial does indeed yield upon entry to the roundabout; where you describe them not having to yield is, in my opinion, still the middle of a big roundabout.

In your models, unless I was seeing them incorrectly, traffic on the arterial does not yield at all.  The way I see it, you simply modeled a ParClo with some wide spots in the medians and curvy trajectories.  I'm not saying it's a bad idea, I'm just saying it has little to do with a roundabout.

Here is a roundabout interchange that Calgary is proposing that is essentially the same design that i posted except that off-ramp traffic exiting the roundabout isn't merging onto the arterial street.

(https://www.calgary.ca/Transportation/TI/PublishingImages/Road-projects/14-St-NW-Stoney-Trail-Interchange-design-2048px.jpg)

And that is a proper teardrop/dogbone interchange with some extra ramps thrown in.  All approaches appear to yield at entry.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 18, 2019, 01:43:10 AM
A teardrop interchange, in my opinion, is just a single squished roundabout interchange–not a pair of roundabouts.  Take a huge circle, squish the middle in, and you end up with two teardrops.  With that in mind, traffic on the arterial does indeed yield upon entry to the roundabout; where you describe them not having to yield is, in my opinion, still the middle of a big roundabout.

I'm very tempted to agree with you, although I think from most driver's perspective, it will appear as though they are travelling through two roundabouts. Drivers aren't looking at these things overhead, and I'm half-certain that most drivers, particularly out west, are not familiar with "roundabout interchanges" like those in the UK and parts of the northeast...they just see two roundabouts, although with the second not requiring a yield.

Just for the record, WA signs their teardrop interchanges with two separate roundabout warning signs: one for the first entry, and another for the second entry. There are some obvious issues with this, but, apparently, states seem to see two separate roundabouts as well (or at least that's common practice).
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on July 18, 2019, 06:13:37 AM
I was just in Aruba, and thyve been adding a bunch of dutch-style roundabouts to their major roads and highways (makes sense, theyre part of the Netherlands). Went through 5 or 6 on their main highway, which is 80kph (50mph). The speeds slwos to 60 and then 40 as you near the roundabout.

Whats interesting is that there are concrete curbs between lanes. No confusion.

This made navigating even the 3 lane roundabout easy. You just stay in your lane, and you cant get out.

Island is loaded up with American tourists, and I didnt see any issues.


The Veterans Memorial Dr and Greenwich Ave roundabout (https://www.google.com/maps/@41.7002966,-71.4605747,3a,48.8y,46.56h,94.48t/data=!3m7!1e1!3m5!1sPCW0DIJfW9l8a3sIaTdXPw!2e0!6s%2F%2Fgeo3.ggpht.com%2Fcbk%3Fpanoid%3DPCW0DIJfW9l8a3sIaTdXPw%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D79.516525%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656) in Warwick may be one of the most dangerous roundabouts in the country.  It's a full 2x2 roundabout with a large retaining wall in the central island and over the weekend a police officer crashed into the retaining wall and suffered several injuries.  The officer's name hasn't been released and no word yet if it's one of the LivePD officers out of Warwick.

Warwick police officer injured when SUV crashes at roundabout
https://www.providencejournal.com/news/20190714/warwick-police-officer-injured-when-suv-crashes-at-roundabout

That looks dangerous. No deflection on entrance or exit.



I think you're too close to the roundabout.  GSV'ing back a little bit you can easily make out the deflection approaching the roundabout.  https://goo.gl/maps/qMdVZ4nVQCvF3wXLA  There isn't much deflection exiting the roundabout, but that's not extremely necessary either, and increases the visibility of pedestrians in the walkway.

I dont think that deflection point makes much sense. Its too early, and actually makes the crosswalk harder to see.

Theres no streetview in Aruba, and with the disclaimer that Ive never driven in mainland Netherlands, their roundabouts had very steep entrance and exit points - youre literally turning on and off.

https://goo.gl/maps/UQkkkURo5k5BpgXv6

Made it seem safer from my experience.

In the US ones, drivers just gun it.

What?  There's no deflection in that GSV example whatsoever.  It's literally a straight line to the roundabout, and then a right turn.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 18, 2019, 07:50:38 AM
Here is one more model of the Calgary interchange design but with exiting roundabout traffic merging down to one lane before joining the arterial street.  I do find it ironic that I'm defending whether or not my design is a roundabout considering how many times i have been accused of hating roundabouts or something to that effect.  I just believe that the simpler a roundabout design is the less chances there are for accidents and with this design there is just not that many ways for cars to crash into each other.
   
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on July 18, 2019, 02:17:56 PM
I was just in Aruba, and thyve been adding a bunch of dutch-style roundabouts to their major roads and highways (makes sense, theyre part of the Netherlands). Went through 5 or 6 on their main highway, which is 80kph (50mph). The speeds slwos to 60 and then 40 as you near the roundabout.

Whats interesting is that there are concrete curbs between lanes. No confusion.

This made navigating even the 3 lane roundabout easy. You just stay in your lane, and you cant get out.

Island is loaded up with American tourists, and I didnt see any issues.


The Veterans Memorial Dr and Greenwich Ave roundabout (https://www.google.com/maps/@41.7002966,-71.4605747,3a,48.8y,46.56h,94.48t/data=!3m7!1e1!3m5!1sPCW0DIJfW9l8a3sIaTdXPw!2e0!6s%2F%2Fgeo3.ggpht.com%2Fcbk%3Fpanoid%3DPCW0DIJfW9l8a3sIaTdXPw%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D79.516525%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656) in Warwick may be one of the most dangerous roundabouts in the country.  It's a full 2x2 roundabout with a large retaining wall in the central island and over the weekend a police officer crashed into the retaining wall and suffered several injuries.  The officer's name hasn't been released and no word yet if it's one of the LivePD officers out of Warwick.

Warwick police officer injured when SUV crashes at roundabout
https://www.providencejournal.com/news/20190714/warwick-police-officer-injured-when-suv-crashes-at-roundabout

That looks dangerous. No deflection on entrance or exit.



I think you're too close to the roundabout.  GSV'ing back a little bit you can easily make out the deflection approaching the roundabout.  https://goo.gl/maps/qMdVZ4nVQCvF3wXLA  There isn't much deflection exiting the roundabout, but that's not extremely necessary either, and increases the visibility of pedestrians in the walkway.

I dont think that deflection point makes much sense. Its too early, and actually makes the crosswalk harder to see.

Theres no streetview in Aruba, and with the disclaimer that Ive never driven in mainland Netherlands, their roundabouts had very steep entrance and exit points - youre literally turning on and off.

https://goo.gl/maps/UQkkkURo5k5BpgXv6

Made it seem safer from my experience.

In the US ones, drivers just gun it.

What?  There's no deflection in that GSV example whatsoever.  It's literally a straight line to the roundabout, and then a right turn.

The right turn into and out of the roundabout is the deflection.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 18, 2019, 05:04:43 PM
I dont think that deflection point makes much sense. Its too early, and actually makes the crosswalk harder to see.

Theres no streetview in Aruba, and with the disclaimer that Ive never driven in mainland Netherlands, their roundabouts had very steep entrance and exit points - youre literally turning on and off.

https://goo.gl/maps/UQkkkURo5k5BpgXv6

Made it seem safer from my experience.

In the US ones, drivers just gun it.

What?  There's no deflection in that GSV example whatsoever.  It's literally a straight line to the roundabout, and then a right turn.

The right turn into and out of the roundabout is the deflection.

Exactly. American roundabouts are designed for speed: long gentle curves which eventually point you directly into the circulating lanes, with the exit often being in a straight line as well.

Dutch [turbo] roundabouts (and by extension, Aruban roundabouts), in comparison, are designed more around turns on-and-off a large circle, rather than around several different intersections/crossover points. Turbo roundabouts still (usually) use circulating markings, like the American roundabouts. This is why American roundabouts are often considered a hybrid between the original English roundabout (where our original roundabout designs came from), and Dutch turbo roundabouts, as unlike English roundabouts, we do include circulating lane lines.

Below, I've mocked up a comparison. The red line represents the American roundabout, and the curves that one might shall use through the roundabout. The blue lines are closer to how a Dutch roundabout might be designed: There is no deflection approaching the roundabout. Drivers simply come up to the circle, and turn right into it, with the sharp right turn being the deflection.

(https://i.imgur.com/LejnUYu.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 22, 2019, 01:51:43 PM
FDOT is going crazy building "large complex" roundabouts along US41 through Sarasota.  The double-lane roundabout at Venice & Jacaranda Blvd is currently the most crash prone intersection in Sarasota County but the triple-lane roundabout design they are planning at Gulf Stream & US-41 should take the cake.

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 22, 2019, 04:32:54 PM
FDOT is going crazy building "large complex" roundabouts along US41 through Sarasota.  The double-lane roundabout at Venice & Jacaranda Blvd is currently the most crash prone intersection in Sarasota County but the triple-lane roundabout design they are planning at Gulf Stream & US-41 should take the cake.

I don't understand some of these approach lane designs. Why are some lanes separated by an island, while others are not? I understand this design with a slip lane, but not for another lane that also goes straight. This roundabout in Carmel (https://goo.gl/maps/nZxuMYeQ2Xwv4qwv8) has an island for the southern approach, between two lanes that go the same place. I don't get it.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 22, 2019, 04:47:25 PM
FDOT is going crazy building "large complex" roundabouts along US41 through Sarasota.  The double-lane roundabout at Venice & Jacaranda Blvd is currently the most crash prone intersection in Sarasota County but the triple-lane roundabout design they are planning at Gulf Stream & US-41 should take the cake.

I don't understand some of these approach lane designs. Why are some lanes separated by an island, while others are not? I understand this design with a slip lane, but not for another lane that also goes straight. This roundabout in Carmel (https://goo.gl/maps/nZxuMYeQ2Xwv4qwv8) has an island for the southern approach, between two lanes that go the same place. I don't get it.

Adding an island one of the only ways to get speed control on a 3-lane approach. Without it, the fastest path measurement would basically be a straight line. It also adds another point of refuge for pedestrians.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on July 22, 2019, 05:14:05 PM
I do find it ironic that I'm defending whether or not my design is a roundabout considering how many times i have been accused of hating roundabouts or something to that effect.

If I hate Russians, then marry a Polish woman, is that ironic?

(For the record, I don't hate Russians, and my wife is part Polish.)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 23, 2019, 07:34:12 AM
If I hate Russians, then marry a Polish woman, is that ironic?

(For the record, I don't hate Russians, and my wife is part Polish.)

That all depends if you colluded with the Russians to get with the Polish woman!  If so well done.

I don't understand some of these approach lane designs. Why are some lanes separated by an island, while others are not? I understand this design with a slip lane, but not for another lane that also goes straight. This roundabout in Carmel (https://goo.gl/maps/nZxuMYeQ2Xwv4qwv8) has an island for the southern approach, between two lanes that go the same place. I don't get it.

Another interesting thing with that Carmel roundabout design is that it has double right turn lanes coming out of the roundabout at two of the approaches.  I don't remember seeing that before.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on July 23, 2019, 07:46:18 PM
FDOT is going crazy building "large complex" roundabouts along US41 through Sarasota.  The double-lane roundabout at Venice & Jacaranda Blvd is currently the most crash prone intersection in Sarasota County but the triple-lane roundabout design they are planning at Gulf Stream & US-41 should take the cake.

I don't understand some of these approach lane designs. Why are some lanes separated by an island, while others are not? I understand this design with a slip lane, but not for another lane that also goes straight. This roundabout in Carmel (https://goo.gl/maps/nZxuMYeQ2Xwv4qwv8) has an island for the southern approach, between two lanes that go the same place. I don't get it.

it's called deflection, it's necessary for large vehicles that need more room. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 24, 2019, 01:46:05 PM
I don't understand some of these approach lane designs. Why are some lanes separated by an island, while others are not? I understand this design with a slip lane, but not for another lane that also goes straight. This roundabout in Carmel (https://goo.gl/maps/nZxuMYeQ2Xwv4qwv8) has an island for the southern approach, between two lanes that go the same place. I don't get it.

Adding an island one of the only ways to get speed control on a 3-lane approach. Without it, the fastest path measurement would basically be a straight line. It also adds another point of refuge for pedestrians.

I see. Makes sense. If sharper entry angles were utilized, perhaps they wouldn't be necessary?

Another interesting thing with that Carmel roundabout design is that it has double right turn lanes coming out of the roundabout at two of the approaches.  I don't remember seeing that before.

Yeah, that is pretty unusual. Multi-lane roundabouts were the first widespread use of double (or even triple) lane yields, for most jurisdictions. It does not surprise me that at least one roundabout in the US implemented a double right turn with a yield. I bet there's more out there. Most double right turns at regular intersections are signalized, though there are many in Alberta that use yield signs (https://goo.gl/maps/5FeZaDh4Z4eTmkcq8), just like the Carmel roundabout. No idea how successful they are.

it's called deflection, it's necessary for large vehicles that need more room. 

No no, the small raised islands in between the approach lanes, not the curvature of the approach leg itself.
Title: Re: Crash prone 'modern roundabouts'
Post by: silverback1065 on July 24, 2019, 02:40:18 PM
If you're talking about the far ones on the right side, it's an added lane so they don't really have to stop.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 24, 2019, 04:50:31 PM
If you're talking about the far ones on the right side, it's an added lane so they don't really have to stop.

Look at the video at the top of the page. The right lane for the left and right approach has a small, mountable island, despite not being a slip lane. Those far-right lanes still have to yield.

DaBigE already answered my question:

Adding an island one of the only ways to get speed control on a 3-lane approach. Without it, the fastest path measurement would basically be a straight line. It also adds another point of refuge for pedestrians.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on July 24, 2019, 05:38:16 PM
I don't understand some of these approach lane designs. Why are some lanes separated by an island, while others are not? I understand this design with a slip lane, but not for another lane that also goes straight. This roundabout in Carmel (https://goo.gl/maps/nZxuMYeQ2Xwv4qwv8) has an island for the southern approach, between two lanes that go the same place. I don't get it.

Adding an island one of the only ways to get speed control on a 3-lane approach. Without it, the fastest path measurement would basically be a straight line. It also adds another point of refuge for pedestrians.

I see. Makes sense. If sharper entry angles were utilized, perhaps they wouldn't be necessary?

Maybe. Every adjustment comes with a trade-off; it's hard to say for sure without playing around with the design and knowing the design vehicles. A more likely possibility would be to have an approach that is more chicaned rather than a simple deflection. But I'd still recommend retaining the islands, to make the approach more pedestrian-friendly. Crossing two lanes of semi-regulated traffic is bad enough. Three is insanity if the vehicular traffic is present that warrants a 3-lane approach.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 28, 2019, 06:54:46 PM
2 dead after car hits boulders, catches fire in Little Rock traffic circle
https://katv.com/news/local/vehicle-catches-on-fire-after-hitting-boulder-in-little-rock-traffic-circle

Why do they have to put boulders in the central islands of these roundabouts?  Two are dead in Little Rock after their vehicle struck the boulders and caught fire.  What's so wrong with having a central island design void of fixed objects (especially outside of central business districts)?  Raised curbing in the central island would likely disable any "drunk driver" who blows through the central island but they wouldn't come to a "dead stop" by hitting a boulder.  Here's a good example of a grassy central island with a raised curb.   

https://www.google.com/maps/@44.8960769,-88.2470036,3a,75y,85.2h,85.59t/data=!3m6!1e1!3m4!1stPCaTkK119UNr9aElKmIkQ!2e0!7i13312!8i6656
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on July 29, 2019, 02:04:13 PM
I think they should make the boulders out of Nerf.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on July 29, 2019, 02:11:12 PM
I think they should make the boulders out of Nerf.

Or just make them explode. Would be way cooler.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 12, 2019, 08:16:29 AM
It would be interesting to see if this design would work or if the traffic volumes turning onto Berdan Ave are too high (requiring the dual circulating lanes).....

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/rbredesign_zpsbffmrhx1.png)



Looks like the city of Toledo will be redesigning the roundabout at Detroit, Berdan, and Cherry.  It sounds similar to the plan i had proposed over 3 years ago.  Ultimately they are reducing it from a 2x2 roundabout to a 1x2 roundabout, which is the quickest way to reduce the number of crashes occurring at these problematic roundabouts.

Changes coming to roundabout at Detroit, Berdan, and Cherry
https://www.toledoblade.com/local/transportation/2019/08/09/multilane-toledo-roundabout-modified-crash-problem-road-construction/stories/20190808124
Title: Re: Crash prone 'modern roundabouts'
Post by: JCinSummerfield on August 12, 2019, 01:46:14 PM
Hallelujah!  I wonder every time I go through there if someone next to me is going to turn right from the left lane.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 12, 2019, 02:09:39 PM
^Yep.  The geometry of that roundabout made it such that the pavement markings were ambiguous to drivers. I'm glad they are finally fixing the problem.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 12, 2019, 02:10:20 PM
Hallelujah!  I wonder every time I go through there if someone next to me is going to turn right from the left lane.
But wait, this is completely legal by design, and should have minimum effect on your actions - it matters only when you enter roundabout; further down the circle right lane should exit anyway
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on August 16, 2019, 04:55:02 PM
Wow, I fully expected this news article to appear in the thread...

Driver banned after dash cam footage shows van flying over a roundabout (https://www.express.co.uk/life-style/cars/1165184/dash-cam-car-driving-ban-roundabout-van)

Quote
Andy, of Hingham, Norwich said: “I was actually on my motorbike behind him so I saw it all.

"I pulled over along with some other drivers to see if he was OK.

“It is quite a bad roundabout, he just didn’t see what was coming because he was going so fast.

“The driver had a few cuts and bruises but the ambulance came straight away and took him to hospital.

“He just didn’t see the roundabout coming.”
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on August 16, 2019, 05:06:51 PM
Quote
“He just didn’t see the roundabout coming.”

Damn sneaky bastards. Never know when they'll jump up and overturn a truck or set a van in flight.
Title: Re: Crash prone 'modern roundabouts'
Post by: ET21 on August 18, 2019, 10:26:11 PM
Quote
“He just didn’t see the roundabout coming.”

Damn sneaky bastards. Never know when they'll jump up and overturn a truck or set a van in flight.

Curse those road circles
Title: Re: Crash prone 'modern roundabouts'
Post by: JCinSummerfield on August 20, 2019, 02:01:09 PM
Hallelujah!  I wonder every time I go through there if someone next to me is going to turn right from the left lane.
But wait, this is completely legal by design, and should have minimum effect on your actions - it matters only when you enter roundabout; further down the circle right lane should exit anyway

When entering the mentioned roundabout from Cherry Street, the straight through movement is to Berdan Ave.  many people believe the straight through movement is to NB US-24, when in fact that is a right turn.  If I'm in the right lane trying to get to Berdan, I stand probably a 50/50 chance of the guy on my left hitting me trying to turn right.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 20, 2019, 05:25:03 PM
Hallelujah!  I wonder every time I go through there if someone next to me is going to turn right from the left lane.
But wait, this is completely legal by design, and should have minimum effect on your actions - it matters only when you enter roundabout; further down the circle right lane should exit anyway

When entering the mentioned roundabout from Cherry Street, the straight through movement is to Berdan Ave.  many people believe the straight through movement is to NB US-24, when in fact that is a right turn.  If I'm in the right lane trying to get to Berdan, I stand probably a 50/50 chance of the guy on my left hitting me trying to turn right.
Well, you may do two things:
1. Thank those who designed nice and conspicious pavement markings
2. Apply some defencive driving concepts, and make sure you anticipate mistakes other motorists are making by using safer lane.

Last, but not the least: apparently, signs designating right lane on Cherry side for right and straight through are not compatible with NE-bound Detroit/24 approach, where both lanes are designated as through lanes. Eliminating straight through option for right lane on Cherry and removing a second lane between two legs of NE branch may be a good idea.
Title: Re: Crash prone 'modern roundabouts'
Post by: Chrispi on August 22, 2019, 07:25:11 PM
Using turn signals properly in a roundabout will help immensely.  Of course, some parts of the country have an even bigger problem with signalling!
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 22, 2019, 08:19:20 PM
Using turn signals properly in a roundabout will help immensely.  Of course, some parts of the country have an even bigger problem with signalling!
you mean turning on emergency flashes to indicate left and right turn at the same time?
Title: Re: Crash prone 'modern roundabouts'
Post by: Chrispi on August 22, 2019, 08:49:46 PM
Using turn signals properly in a roundabout will help immensely.  Of course, some parts of the country have an even bigger problem with signalling!
you mean turning on emergency flashes to indicate left and right turn at the same time?
Any signal would be good, for most of the morons seen on the road.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 22, 2019, 08:52:24 PM
Using turn signals properly in a roundabout will help immensely.  Of course, some parts of the country have an even bigger problem with signalling!
you mean turning on emergency flashes to indicate left and right turn at the same time?
Any signal would be good, for most of the morons seen on the road.
Don't look into the mirror while driving, look out!
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 22, 2019, 11:34:03 PM
Modifications, including blinky signs, have been made to Hilliard's Main Street and Cemetery Road roundabout.

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 23, 2019, 11:02:08 AM
A new roundabout is being proposed at Orchard Lake Road and Ludden St in Oakland County, Michigan just south of the accident-prone roundabout at Orchard Lake & 14 Mile (which saw 144 crashes including 20 injury crashes in 2018 alone).  One of the cited problems in the article is that there are a lot of accidents caused by people turning left out of the driveways just south of the roundabout.  Now they plan to convert Orchard Lake to a divided boulevard and force drivers to turn right out of the driveways and use the new proposed roundabout to make their U-turn.

New roundabout, boulevard planned for Orchard Lake Road in Farmington Hills
https://www.hometownlife.com/story/news/local/farmington-hills/2019/08/22/another-roundabout-planned-orchard-lake-road-farmington-hills/2083910001/


In the news report, I just noticed they recently added some massive boulders in the central island of the 14 Mile & Orchard Lake roundabout.  A lot of deaths that occur at roundabouts are associated with single-car fixed object accidents and a boulder is a pretty big-ass fixed object… apparently 144 crashes and 20 injury crashes just isn’t enough of a problem already.
Title: Re: Crash prone 'modern roundabouts'
Post by: thspfc on August 23, 2019, 08:54:39 PM
Not sure what the thought process is for MDOT on that one.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 31, 2019, 01:17:39 AM
I saw this aerial image of a new roundabout constructed in Spokane, WA, as part of a Costco development (original PDF here (https://chambermaster.blob.core.windows.net/userfiles/UserFiles/chambers/9465/File/Events/WSDOT.pdf)). What caught my eye was the median extensions visible on the bottom and right approaches (eastern and northern respectively), which are made of asphalt, plus the central island which was clearly extended after construction (notice the odd curving lines). It was clearly meant to incorporate additional circulating lanes; namely, a second eastern approach lane, and a third northern approach lane. While it was not constructed with such things, it clearly is meant to be modified as necessary for those things later on. If that third lane were built as (perhaps) originally planned, it would be the only roundabout in Washington with three circulating lanes.

There's no saying why it wasn't built this way to begin with, but I think WSDOT has had some issues with some of their larger roundabouts, in terms of crashes, so they might be trying to play more conservatively now than before.

(Google Maps location (https://goo.gl/maps/ioagfMyrde2LCrrQA))

(https://i.imgur.com/NjkrCcD.png)

Here's some aerial video as well:

Title: Re: Crash prone 'modern roundabouts'
Post by: motorola870 on August 31, 2019, 07:25:22 AM
I saw this aerial image of a new roundabout constructed in Spokane, WA, as part of a Costco development (original PDF here (https://chambermaster.blob.core.windows.net/userfiles/UserFiles/chambers/9465/File/Events/WSDOT.pdf)). What caught my eye was the median extensions visible on the bottom and right approaches (eastern and northern respectively), which are made of asphalt, plus the central island which was clearly extended after construction (notice the odd curving lines). It was clearly meant to incorporate additional circulating lanes; namely, a second eastern approach lane, and a third northern approach lane. While it was not constructed with such things, it clearly is meant to be modified as necessary for those things later on. If that third lane were built as (perhaps) originally planned, it would be the only roundabout in Washington with three circulating lanes.

There's no saying why it wasn't built this way to begin with, but I think WSDOT has had some issues with some of their larger roundabouts, in terms of crashes, so they might be trying to play more conservatively now than before.

(Google Maps location (https://goo.gl/maps/ioagfMyrde2LCrrQA))

(https://i.imgur.com/NjkrCcD.png)

Here's some aerial video as well:

If someone is going to design such a mess of a roundabout is it really saving over a standard traffic signal? this looks like someone wanted to get creative and waste tax payer money. This has way too much right of way wasted. As much ROW they used this intersection could be been completely grade seperated! This is a case of pork spending and not being reasonable. I am in area where traffic circles are becoming more common but they will not place them on major roads. They are used in roads adjoining new shopping areas or residential areas where it makes more sense to do a circle than putting in a full fledged signal. If it were my decision if they actually think they needed that much right of way it would have just been smarter to make a 4 lane overpass and make service ramps to the Costco. Like is the Costco going to go anywhere? This roundabout is eventually likely to be signalized anyways.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 31, 2019, 07:36:28 AM
If someone is going to design such a mess of a roundabout is it really saving over a standard traffic signal? this looks like someone wanted to get creative and waste tax payer money. This has way too much right of way wasted. As much ROW they used this intersection could be been completely grade seperated! This is a case of pork spending and not being reasonable.

It's not always about the money.  If so, we wouldn't even have interchanges or traffic lights to begin with.  As in most cases the cheapest option is the do nothing option, with the second option being a standard intersection with stop signs, they were willing to spend money.  Ultimately it comes down to what they believe will bring the most bang for the buck.

Also, if this is right outside a new shopping center, the developer may have paid to install the roundabout, which then IS the cheapest option long-term, because the town/city/county/state won't have to pay the electric for a traffic light in the future.
Title: Re: Crash prone 'modern roundabouts'
Post by: motorola870 on August 31, 2019, 07:42:41 AM
If someone is going to design such a mess of a roundabout is it really saving over a standard traffic signal? this looks like someone wanted to get creative and waste tax payer money. This has way too much right of way wasted. As much ROW they used this intersection could be been completely grade seperated! This is a case of pork spending and not being reasonable.

It's not always about the money.  If so, we wouldn't even have interchanges or traffic lights to begin with.  As in most cases the cheapest option is the do nothing option, with the second option being a standard intersection with stop signs, they were willing to spend money.  Ultimately it comes down to what they believe will bring the most bang for the buck.

Also, if this is right outside a new shopping center, the developer may have paid to install the roundabout, which then IS the cheapest option long-term, because the town/city/county/state won't have to pay the electric for a traffic light in the future.
The footprint of the circle is not reasonable. It is mind blowing they actually thought a 3 lane inner circle would solve issues.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on August 31, 2019, 10:36:05 AM
If someone is going to design such a mess of a roundabout is it really saving over a standard traffic signal? this looks like someone wanted to get creative and waste tax payer money. This has way too much right of way wasted. As much ROW they used this intersection could be been completely grade seperated! This is a case of pork spending and not being reasonable.

It's not always about the money.  If so, we wouldn't even have interchanges or traffic lights to begin with.  As in most cases the cheapest option is the do nothing option, with the second option being a standard intersection with stop signs, they were willing to spend money.  Ultimately it comes down to what they believe will bring the most bang for the buck.

Also, if this is right outside a new shopping center, the developer may have paid to install the roundabout, which then IS the cheapest option long-term, because the town/city/county/state won't have to pay the electric for a traffic light in the future.
The footprint of the circle is not reasonable. It is mind blowing they actually thought a 3 lane inner circle would solve issues.

With the amount of traffic that roundabout was designed to handle, a signalized option wouldn't be much smaller. Look at the impacts of an adjacent intersection (https://goo.gl/maps/BXkcVyrSsq4RHe7VA).
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 31, 2019, 02:21:29 PM
I don't think roundabouts really are too much larger than some regular signalized intersections, especially when you take into account the fewer number of required "turn only" lanes. Where they "getcha" is with the slip lanes. At the "node", roundabouts are almost always larger (their primary advantage being narrower approach roads); when they start adding in slip lanes for right turns, the width of the "node" does get quite wide, quite quickly.

The chicanes on the approach, which are certainly wise given the 55-mph limit on Newport Highway, could have probably dipped left towards the oncoming lanes, and then curved right into the roundabout, instead of right, then left, and then right again into the roundabout. That could have saved on some ROW too. If they removed the slip lanes, that could have helped too. Fewer crosswalks that way too.

Also, if this is right outside a new shopping center, the developer may have paid to install the roundabout, which then IS the cheapest option long-term, because the town/city/county/state won't have to pay the electric for a traffic light in the future.

It was indeed funded by the developer. There's another roundabout just to the east that currently serves no purpose, except to incorporate more legs for other development later on.
Title: Re: Crash prone 'modern roundabouts'
Post by: 6a on August 31, 2019, 04:07:55 PM
Modifications, including blinky signs, have been made to Hilliard's Main Street and Cemetery Road roundabout.


Yeah, they also put in speed bumps at the crosswalks. I always forget they’re there since there’s no warning whatsoever about their existence. Overall I’d say they did a decent job. The southern leg of the Scioto Darby one lost a lane, so eastbound traffic now has a dedicated right only lane.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on September 04, 2019, 11:56:28 AM
Recently drove through NJ and passed what appeared to be a brand new roundabout, but they still had the circle lanes yield to entering traffic. Come on!

This bad boy:

https://goo.gl/maps/ePJh6ZJoR4dBQKh17

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 04, 2019, 12:52:01 PM
^That's actually an old traffic circle but was reconfigured recently to include slip lanes and truck aprons.  Looks like yield operation is the same to the old circle with traffic inside the circle yielding to traffic entering the circle.  That is definitely a traffic circle and not a modern roundabout. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 04, 2019, 01:06:39 PM
^^
It's not a modern roundabout, but you have to give credit to New Jersey for excellence striping and markings. Compared to the old layout, this should produce far fewer accidents.

Of course, I don't have any idea what kind of accidents the intersection was experiencing before. But a lot of those old circles had almost no markings, and drivers just sort of flying all over the place. I assume this would be a little better**

**despite this, I do support the idea of regular roundabouts not having markings. I've never been convinced that they are necessary at traditional modern roundabouts. But with an intersection the size of what we see above, it might be necessary.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on September 04, 2019, 01:12:47 PM
Recently drove through NJ and passed what appeared to be a brand new roundabout, but they still had the circle lanes yield to entering traffic. Come on!

This bad boy:

https://goo.gl/maps/ePJh6ZJoR4dBQKh17



NJ has done this to a few traffic circles.  They incorporate many roundabout features but they stop short of calling it a roundabout.  Using the Brooklawn Circle for example, they go so far as to sign it as a traffic circle: https://goo.gl/maps/UpdFGGysnbbYS83T8 .

In response to Jackroot...I think the lane markings do help control traffic a bit more, and I imagine it does cut down on some sideswipe accidents.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on September 05, 2019, 10:11:47 AM
Recently drove through NJ and passed what appeared to be a brand new roundabout, but they still had the circle lanes yield to entering traffic. Come on!

This bad boy:

https://goo.gl/maps/ePJh6ZJoR4dBQKh17



NJ has done this to a few traffic circles.  They incorporate many roundabout features but they stop short of calling it a roundabout.  Using the Brooklawn Circle for example, they go so far as to sign it as a traffic circle: https://goo.gl/maps/UpdFGGysnbbYS83T8 .

In response to Jackroot...I think the lane markings do help control traffic a bit more, and I imagine it does cut down on some sideswipe accidents.

Oddly, the circle across the tracks has no indication as to who yields in this spot:

https://goo.gl/maps/P9Lxsw3hHVnfAqMd6
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on September 05, 2019, 10:31:26 AM
Recently drove through NJ and passed what appeared to be a brand new roundabout, but they still had the circle lanes yield to entering traffic. Come on!

This bad boy:

https://goo.gl/maps/ePJh6ZJoR4dBQKh17



NJ has done this to a few traffic circles.  They incorporate many roundabout features but they stop short of calling it a roundabout.  Using the Brooklawn Circle for example, they go so far as to sign it as a traffic circle: https://goo.gl/maps/UpdFGGysnbbYS83T8 .

In response to Jackroot...I think the lane markings do help control traffic a bit more, and I imagine it does cut down on some sideswipe accidents.

Oddly, the circle across the tracks has no indication as to who yields in this spot:

https://goo.gl/maps/P9Lxsw3hHVnfAqMd6

Correct - that's a traditional NJ Traffic Circle.  Most didn't have any traffic control whatsoever.  If you were to continue around the circle, the next merge point has no signage either.  However, the 3rd leg on this circle does - traffic entering the circle yields to those already in the circle.  https://goo.gl/maps/KocSdGEAHqkqqwoS6

The next question...why was this circle not modified the same time the other circle, just on the other side of the overpass, was modified?  I do know that in a future project that will replace the overpass over a river just before your link, they are going to see if they address the severe flooding that occurs here quite often; possibly with some sort of seawall. At that time, maybe they'll modernize this circle, Jersey style!
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 20, 2019, 05:53:09 PM
An elderly couple was killed after their Toyota Prius crashed into the concrete roundabout at Highway 12 and 113 near Suisun City, California.  Retaining walls in the the central islands of roundabouts... specifically roundabouts in rural/suburban locations... doesn't seem necessary.

(https://www.dailyrepublic.com/files/2019/09/20-hwy-12_113-intersection.jpg)

Crash at Highways 12/113 roundabout leaves 2 dead
https://www.dailyrepublic.com/all-dr-news/solano-news/suisun-city/crash-at-highways-12-113-roundabout-leaves-2-dead/comment-page-1/


Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 20, 2019, 10:56:25 PM
An elderly couple was killed after their Toyota Prius crashed into the concrete roundabout at Highway 12 and 113 near Suisun City, California.  Retaining walls in the the central islands of roundabouts... specifically roundabouts in rural/suburban locations... doesn't seem necessary.

Hell of a start. Decorations should not kill people.
Title: Re: Crash prone 'modern roundabouts'
Post by: Brian556 on September 21, 2019, 12:24:16 AM
An elderly couple was killed after their Toyota Prius crashed into the concrete roundabout at Highway 12 and 113 near Suisun City, California.  Retaining walls in the the central islands of roundabouts... specifically roundabouts in rural/suburban locations... doesn't seem necessary.

Hell of a start. Decorations should not kill people.

Decorations don't kill people. Dumb drivers kill themselves
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 21, 2019, 02:03:02 AM
An elderly couple was killed after their Toyota Prius crashed into the concrete roundabout at Highway 12 and 113 near Suisun City, California.  Retaining walls in the the central islands of roundabouts... specifically roundabouts in rural/suburban locations... doesn't seem necessary.

Hell of a start. Decorations should not kill people.

Decorations don't kill people. Dumb drivers kill themselves

Who's to say there wasn't a medical emergency? Fact is they'd still be alive if they didn't whack into that concrete median. Maybe another car could have killed them, but they didn't get far enough to find out.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on September 21, 2019, 06:07:43 AM
An elderly couple was killed after their Toyota Prius crashed into the concrete roundabout at Highway 12 and 113 near Suisun City, California.  Retaining walls in the the central islands of roundabouts... specifically roundabouts in rural/suburban locations... doesn't seem necessary.

Hell of a start. Decorations should not kill people.

Decorations don't kill people. Dumb drivers kill themselves

Who's to say there wasn't a medical emergency? Fact is they'd still be alive if they didn't whack into that concrete median. Maybe another car could have killed them, but they didn't get far enough to find out.
An elderly couple was killed after their Toyota Prius crashed into the concrete roundabout at Highway 12 and 113 near Suisun City, California.  Retaining walls in the the central islands of roundabouts... specifically roundabouts in rural/suburban locations... doesn't seem necessary.

Hell of a start. Decorations should not kill people.

Decorations don't kill people. Dumb drivers kill themselves

Who's to say there wasn't a medical emergency? Fact is they'd still be alive if they didn't whack into that concrete median. Maybe another car could have killed them, but they didn't get far enough to find out.

Or maybe they would've killed innocent people in that other car.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 21, 2019, 04:55:09 PM
An elderly couple was killed after their Toyota Prius crashed into the concrete roundabout at Highway 12 and 113 near Suisun City, California.  Retaining walls in the the central islands of roundabouts... specifically roundabouts in rural/suburban locations... doesn't seem necessary.

Hell of a start. Decorations should not kill people.

Decorations don't kill people. Dumb drivers kill themselves

Who's to say there wasn't a medical emergency? Fact is they'd still be alive if they didn't whack into that concrete median. Maybe another car could have killed them, but they didn't get far enough to find out.

What if they kept driving straight from the base approach of a T-intersection and ran into a building or the concrete stairs leading up to a building. Would you blame the building?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 21, 2019, 05:28:53 PM
Or maybe they would've killed innocent people in that other car.

Still didn't get to find out. Wouldn't you rather take a chance than just kill anyone who loses control?

What if they kept driving straight from the base approach of a T-intersection and ran into a building or the concrete stairs leading up to a building. Would you blame the building?

Buildings serve a purpose...fucking concrete central islands do what exactly? Kill people who lose control?
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 21, 2019, 11:47:05 PM
Or maybe they would've killed innocent people in that other car.

Still didn't get to find out. Wouldn't you rather take a chance than just kill anyone who loses control?

I'm not trying to defend the placement of the concrete, but in order for it to kill someone, it isn't just losing control. Excessive speed plays a significant role. Look at the photo... there's plenty of warning. For crying out loud, there's two sets of overhead flashing lights. Even if the concrete wasn't there, a basic mounded central island might not have changed the ultimate outcome. Depending on speed (which we still don't know), they could have been sent flying.

Given the age of the occupants, there's no guarantee they would have survived hitting a breakaway street light. With age comes added frailty. Until the full report comes out, it could have been a medical condition before they ever hit anything. It could have been a heart attack when they crashed. Until we know the medical report and the speed they were traveling at saying the concrete killed them is only one hypothesis. Is placing vertical concrete in that location advisable? No. But it's not like the concrete randomly decided to spring up and yell "boo!"

What if they kept driving straight from the base approach of a T-intersection and ran into a building or the concrete stairs leading up to a building. Would you blame the building?
Buildings serve a purpose...fucking concrete central islands do what exactly? Kill people who lose control?

Ok, don't like that scenario, how about a power pole on the outside of a curve. Or, a big 80-year old oak tree. Either of those items don't come with as much warning. When does it become the driver's fault?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 22, 2019, 05:03:29 PM
Or maybe they would've killed innocent people in that other car.

Still didn't get to find out. Wouldn't you rather take a chance than just kill anyone who loses control?

I'm not trying to defend the placement of the concrete, but in order for it to kill someone, it isn't just losing control. Excessive speed plays a significant role. Look at the photo... there's plenty of warning. For crying out loud, there's two sets of overhead flashing lights. Even if the concrete wasn't there, a basic mounded central island might not have changed the ultimate outcome. Depending on speed (which we still don't know), they could have been sent flying.

Given the age of the occupants, there's no guarantee they would have survived hitting a breakaway street light. With age comes added frailty. Until the full report comes out, it could have been a medical condition before they ever hit anything. It could have been a heart attack when they crashed. Until we know the medical report and the speed they were traveling at saying the concrete killed them is only one hypothesis. Is placing vertical concrete in that location advisable? No. But it's not like the concrete randomly decided to spring up and yell "boo!"

Fair enough. I shouldn't assume that the concrete killed them. But the part I bolded is basically my argument here: concrete central islands are a poor choice of decoration. If their plan is to build up a wall of bark or dirt around the concrete wall, that would be great (although not as good as flat with bushes...we don't need to be sending cars flying). Maybe they're making a hill here. In any case, even with everything else being up in the air, I'm sure you'd agree that the placement of that concrete island did not do the occupants of that car any favors. That is my only point here. Drivers f' up, a lot. I don't see why Caltrans (or any agency) needs to be throwing drivers additional curveballs. Roundabouts are hard enough for most people...

What if they kept driving straight from the base approach of a T-intersection and ran into a building or the concrete stairs leading up to a building. Would you blame the building?
Buildings serve a purpose...fucking concrete central islands do what exactly? Kill people who lose control?

Ok, don't like that scenario, how about a power pole on the outside of a curve. Or, a big 80-year old oak tree. Either of those items don't come with as much warning. When does it become the driver's fault?

Usually if they're placed in the middle of a road, there'd be some warning. Most freeways are lined with concrete barriers much like the central island of this roundabout, but importantly, they aren't directly in the path of drivers. Every now and then, someone spins out and whacks into one, but no one hits one head-on because they're on their phone or because they have a medical emergency. Usually a side-swipe. The central island of a roundabout is directly in the path of oncoming traffic. Yes, many roundabouts feature chicanes, but the lanes are so wide you can usually navigate it in a straight path anyways.

I can't recall for certain, but there' usually a clear path next to most roadways nowadays too, so that trees and power poles aren't directly adjacent to major highways (in case drivers run off the road). Then again, there'd be more of an argument for power poles and trees being adjacent to roads, since they at least have a purpose. I still don't know what that concrete island has done for anyone, besides look "pretty".
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 23, 2019, 02:09:25 PM
Here is a news report regarding the fatal crash Wednesday night of the elderly couple at the Highway 12 and Highway 113 roundabout.  In it, Caltrans spokeswoman Janis Mara defends the safety of roundabouts by citing 2000 IIHS safety statistics.  Lots has changed with roundabout design over the past 20 years in this country, but apparently citing a report with 20 year old data is good enough for Caltrans. This is what Janis had to say midway through the news report...

"The shape of the roundabout results in lower speeds, generally 15 to 25 miles per hour.  And as we all know, slower is safer." 

On the surface Janis' statement sounds reasonable, but just imagine if the safety of traffic signals was touted by saying "the red lights at a traffic signal results in drivers coming to a complete stop.  And as we all know, a stationary vehicle is safer than a moving vehicle." 

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 23, 2019, 02:59:48 PM
What truly bothers me is that a driver approaching that intersection at the speed limit has no chance of being able to navigate it properly. Slower is safer, sure, but what if someone isn't going slow? That's catastrophic, and it's a problem that roundabouts don't seem well-equipped to handle. Not least without a giant magnet in the central island to that can grab onto an out-of-control car.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on September 23, 2019, 04:07:37 PM
Features inside the central island have been advocated in the past as a way of making the roundabout more visible to drivers and therefore less likely to be hit.  Without some sort of retaining wall, wouldn't any built-up feature inside the island run the risk of having fill dirt and rainwater flow onto the circulating roadway and create hazardous conditions?
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on September 23, 2019, 04:08:21 PM
Here is a news report regarding the fatal crash Wednesday night of the elderly couple at the Highway 12 and Highway 113 roundabout.  In it, Caltrans spokeswoman Janis Mara defends the safety of roundabouts by citing 2000 IIHS safety statistics.  Lots has changed with roundabout design over the past 20 years in this country, but apparently citing a report with 20 year old data is good enough for Caltrans.

Well, at least that's better than what Bazoo used when trying to defend something.  His defense was utilizing data from 1979!

https://www.aaroads.com/forum/index.php?topic=17051.msg2443849#msg2443849


What truly bothers me is that a driver approaching that intersection at the speed limit has no chance of being able to navigate it properly. Slower is safer, sure, but what if someone isn't going slow? That's catastrophic, and it's a problem that roundabouts don't seem well-equipped to handle. Not least without a giant magnet in the central island to that can grab onto an out-of-control car.

No different than approaching a stop sign, a red light, a curve in the road, congestion, a person in a pedestrian crossing, etc.  The speed limit isn't a mandatory speed to drive, and a driver has a duty to exercise caution and slow down when necessary.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 23, 2019, 04:35:13 PM
Features inside the central island have been advocated in the past as a way of making the roundabout more visible to drivers and therefore less likely to be hit.  Without some sort of retaining wall, wouldn't any built-up feature inside the island run the risk of having fill dirt and rainwater flow onto the circulating roadway and create hazardous conditions?
Lots of collapsible energy absorbing systems have been developed.
Although, I keep enjoying all those attempts of resolving multiple issues caused by a single faulty design choice.  :popcorn:
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 23, 2019, 04:59:32 PM
What truly bothers me is that a driver approaching that intersection at the speed limit has no chance of being able to navigate it properly. Slower is safer, sure, but what if someone isn't going slow? That's catastrophic, and it's a problem that roundabouts don't seem well-equipped to handle. Not least without a giant magnet in the central island to that can grab onto an out-of-control car.

No different than approaching a stop sign, a red light, a curve in the road, congestion, a person in a pedestrian crossing, etc.  The speed limit isn't a mandatory speed to drive, and a driver has a duty to exercise caution and slow down when necessary.

Of course. But when drivers don't do their duty? Those other features tend to be more forgiving:

* stop signs can be run and you may not hit anything
* red lights are the same as stop signs
* curves often have guiderails to keep you on the road, especially on high-speed roads, that you generally won't T-bone.

Congestion and crossing pedestrians are generally not as forgiving, but are also features of roundabouts, so I'm not sure I understand your point.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 23, 2019, 05:05:00 PM
Features inside the central island have been advocated in the past as a way of making the roundabout more visible to drivers and therefore less likely to be hit.  Without some sort of retaining wall, wouldn't any built-up feature inside the island run the risk of having fill dirt and rainwater flow onto the circulating roadway and create hazardous conditions?

You can probably still use a small curb, or even some rocks. A two or three foot-tall barrier just seems silly.

It can also be designed like a bioswale, where there is a drop that collects dirt and rainwater (rather than having the roadway surface be the lowest part of the design):

(https://live.staticflickr.com/8740/16897791158_a19b22e549_o.jpg)
Image from Flickr -- Dianne Yee (https://www.flickr.com/photos/dianneyee/)
Title: Re: Crash prone 'modern roundabouts'
Post by: TEG24601 on September 23, 2019, 06:35:44 PM
It seems like Caltrans could have built their roundabout more like the ones WSDOT have built, with more nuanced approaches, and a mound in the middle.  If they want one at higher speeds, then maybe a rotary would more appropriate, just requires more land.  Then again, hearing what this road does, is seems asinine for Caltrans to keep the roadway 2 lane, and perhaps this intersection really should be grade separated.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 23, 2019, 06:58:32 PM
It seems like Caltrans could have built their roundabout more like the ones WSDOT have built, with more nuanced approaches, and a mound in the middle.

What exactly do you mean when you say "nuanced approaches"? I would agree that a mound in the middle might have been better, although that could have sent the car flying!
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 23, 2019, 08:45:13 PM
What if they kept driving straight from the base approach of a T-intersection and ran into a building or the concrete stairs leading up to a building. Would you blame the building?
Buildings serve a purpose...fucking concrete central islands do what exactly? Kill people who lose control?

Ok, don't like that scenario, how about a power pole on the outside of a curve. Or, a big 80-year old oak tree. Either of those items don't come with as much warning. When does it become the driver's fault?

Usually if they're placed in the middle of a road, there'd be some warning. Most freeways are lined with concrete barriers much like the central island of this roundabout, but importantly, they aren't directly in the path of drivers. Every now and then, someone spins out and whacks into one, but no one hits one head-on because they're on their phone or because they have a medical emergency. Usually a side-swipe. The central island of a roundabout is directly in the path of oncoming traffic. Yes, many roundabouts feature chicanes, but the lanes are so wide you can usually navigate it in a straight path anyways.

I can't recall for certain, but there' usually a clear path next to most roadways nowadays too, so that trees and power poles aren't directly adjacent to major highways (in case drivers run off the road). Then again, there'd be more of an argument for power poles and trees being adjacent to roads, since they at least have a purpose. I still don't know what that concrete island has done for anyone, besides look "pretty".

Reread what is bolded. I'm not talking about an object in the middle of a road. I'm referring to a rural two-lane highway with a curve, similar to something like this (https://goo.gl/maps/RQM1RWUHgtHia3dA8). Miss the one warning sign on a dark night, and you're going off-roading. Sure, the chances of hitting the pole are much less than hitting a wall, but the consequence is the same.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 23, 2019, 09:20:22 PM
What if they kept driving straight from the base approach of a T-intersection and ran into a building or the concrete stairs leading up to a building. Would you blame the building?
Buildings serve a purpose...fucking concrete central islands do what exactly? Kill people who lose control?

Ok, don't like that scenario, how about a power pole on the outside of a curve. Or, a big 80-year old oak tree. Either of those items don't come with as much warning. When does it become the driver's fault?

Usually if they're placed in the middle of a road, there'd be some warning. Most freeways are lined with concrete barriers much like the central island of this roundabout, but importantly, they aren't directly in the path of drivers. Every now and then, someone spins out and whacks into one, but no one hits one head-on because they're on their phone or because they have a medical emergency. Usually a side-swipe. The central island of a roundabout is directly in the path of oncoming traffic. Yes, many roundabouts feature chicanes, but the lanes are so wide you can usually navigate it in a straight path anyways.

I can't recall for certain, but there' usually a clear path next to most roadways nowadays too, so that trees and power poles aren't directly adjacent to major highways (in case drivers run off the road). Then again, there'd be more of an argument for power poles and trees being adjacent to roads, since they at least have a purpose. I still don't know what that concrete island has done for anyone, besides look "pretty".

Reread what is bolded. I'm not talking about an object in the middle of a road. I'm referring to a rural two-lane highway with a curve, similar to something like this (https://goo.gl/maps/RQM1RWUHgtHia3dA8). Miss the one warning sign on a dark night, and you're going off-roading. Sure, the chances of hitting the pole are much less than hitting a wall, but the consequence is the same.

Oh no, no, I got what you meant. What I was attempting to say that was, if a power pole or tree, hypothetically, ended up in the middle of a road (historic tree or impossible-to-move power structure), there might be some kind of warning because the object will likely require a driver to maneuver around it (going straight may end up causing a crash).

In the same manner, roundabouts have warning signs (W2-6) because drivers must take action to avoid a collision with the central island. You don't really have to take action to avoid a tree or power pole on the outside of a curve, assuming some sort of guiderail is in place along the curve. Yes, you'll still crash, but it won't be a head-on crash.
Title: Re: Crash prone 'modern roundabouts'
Post by: skluth on September 24, 2019, 02:37:54 AM
What truly bothers me is that a driver approaching that intersection at the speed limit has no chance of being able to navigate it dproperly. Slower is safer, sure, but what if someone isn't going slow? That's catastrophic, and it's a problem that roundabouts don't seem well-equipped to handle. Not least without a giant magnet in the central island to that can grab onto an out-of-control car.

And here we get to the root of the disagreement. Some of us actually expect people to be good drivers when driving. Others want all drivers but them to be in self-driving cars because others can't be trusted. Most drivers don't have a problem with non-roundabout driving challenges like stop lights and no passing zones. I don't get why roundabouts are any different.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 24, 2019, 03:57:21 AM
What truly bothers me is that a driver approaching that intersection at the speed limit has no chance of being able to navigate it dproperly. Slower is safer, sure, but what if someone isn't going slow? That's catastrophic, and it's a problem that roundabouts don't seem well-equipped to handle. Not least without a giant magnet in the central island to that can grab onto an out-of-control car.

And here we get to the root of the disagreement. Some of us actually expect people to be good drivers when driving. Others want all drivers but them to be in self-driving cars because others can't be trusted. Most drivers don't have a problem with non-roundabout driving challenges like stop lights and no passing zones. I don't get why roundabouts are any different.

Let's be real: humans are not good at operating cars. Despite cars having been around for over a hundred years, we still continue to kill each other with them every year, by the tens of thousands. Are deaths down from the 70s? Oh yeah, but are they continuing to drop? Not like they were, and 2018 apparently was the first drop in deaths since 2015, and it wasn't a big drop. For the record, I'm not part of the "everyone sucks but me" campaign. I regularly make small errors that really remind me to pay attention.

I'm not trying to use scare-tactics here, but there's very little reason to believe that, well, at least Americans, are capable of handling roundabouts. Engineers typically build things with multiple redundancies, to avoid catastrophic failure (look up all the redundancies for the Tower of Terror...really amazing stuff). Traffic lights technically have a fail-safe operation: if someone approaches an intersection without noticing the signal, they can, hypothetically, pass through it unharmed because there are no obstacles directly in front of them other than other cars (which there would be at roundabouts too, so it's still a fair comparison). Guiderailes are a very common safety/redundancy feature as well, and keep cars from flying off the road. They are mostly designed to deflect rather than absorb (except the end pieces), so vehicle occupants should survive. Another is breakaway sign posts, which give way with enough force, to avoid completely destroying whatever hits it.

Compare this to the Solano County roundabout. What is its failsafe? What if a driver doesn't notice the roundabout? There will absolutely be a crash. If not with another car, then with that stupid concrete island.

Honestly, if they removed the concrete island, I would be fine with this roundabout. If they installed a shit-ton of bushes in the middle, with the hope that they would absorb the energy of a car, that could be their redundancy feature.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 24, 2019, 09:16:13 AM
Let's be real: humans are not good at operating cars. Despite cars having been around for over a hundred years, we still continue to kill each other with them every year, by the tens of thousands. Are deaths down from the 70s? Oh yeah, but are they continuing to drop? Not like they were, and 2018 apparently was the first drop in deaths since 2015, and it wasn't a big drop.

One, IMO, big contributing factor in the lack of drops in crashes is the ever increasing amount of technological distractions. No matter how many crashes occur, too many drivers still feel a text message is more important than the vehicle they're operating.

Engineers typically build things with multiple redundancies, to avoid catastrophic failure (look up all the redundancies for the Tower of Terror...really amazing stuff). Traffic lights technically have a fail-safe operation: if someone approaches an intersection without noticing the signal, they can, hypothetically, pass through it unharmed because there are no obstacles directly in front of them other than other cars (which there would be at roundabouts too, so it's still a fair comparison).

Sorry, I have a hard time agreeing with the notion that traffic lights have fail-safe operation. Russian roulette-style fail-safe, maybe. Miss the signal and you are either really lucky, or fail in a really ugly fashion. At least with a roundabout, you have the chance the splitter island curb will slow-down or redirect a errant vehicle (granted, those chances decrease on multilane approaches).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 24, 2019, 10:23:23 AM
At least with a roundabout, you have the chance the splitter island curb will slow-down or redirect a errant vehicle (granted, those chances decrease on multilane approaches).
Bingo! Just make sure it is actually slowed down, not launched up by a truck apron; nor compacted by chunk of solid concrete. SOmething like soft soil, maybe with some vegetation?...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 24, 2019, 11:25:23 AM
Sorry, I have a hard time agreeing with the notion that traffic lights have fail-safe operation. Russian roulette-style fail-safe, maybe. Miss the signal and you are either really lucky, or fail in a really ugly fashion. At least with a roundabout, you have the chance the splitter island curb will slow-down or redirect a errant vehicle (granted, those chances decrease on multilane approaches).

Blowing through the middle of a roundabout with a concrete retaining wall in the central island is like playing Russian Roulette with 6 bullets in the chamber.  Fixed object fatalities at roundabouts is a real concern and here is what the FHWA had to say on the issue in its 2015 report “A Review of Fatal and Severe Injury Crashes at Roundabouts” .

Quote
Fixed-object crash types were the most common crash types among the Injury A and B crashes at roundabouts in Washington and Wisconsin and were involved in 85 percent of fatal crashes at roundabouts. Of the 39 fatal fixed object crashes at roundabouts, 35 involved vehicles striking the curb. In some cases, multiple fixed objects were involved in a single crash. For example, a vehicle may have struck the curb first and a sign post second.

Given that roundabouts rely on effective channelization using raised features such as splitter islands and central islands, as well as on signing to communicate legal movements and right-of-way to users, some fixed objects are inherent in the design of roundabouts and must be present in the design. Other objects that were hit, such as boulders, retaining walls, trees, and landscaping, may be optional at many roundabout locations. Based on these observations, the following sections summarize recommendations made about fixed objects…

Rigid Fixed Objects
Thoughtful placement of fixed objects is a basic principle of proper roadside design. In 2011, the American Association of State Highway and Transportation Officials (AASHTO) published an updated Roadside Design Guide (RDG), and the revisions to Chapter 10 on Roadside Safety in Urban or Restricted Environments represented a new perspective on roadside design in lower speed and urban contexts.(7) Roundabouts share many of the characteristics discussed in this chapter of the RDG, and hence the updated guidance may be of value for roundabout design as well. In particular, as described in the RDG, it could be worthwhile to consider what may be “high risk”  locations for fixed objects unique to roundabouts, given the movements of traffic approaching, circulating, and leaving the vicinity of a roundabout.

If you put that Solano County roundabout in context it’s just a really bad spot to have an unnecessary rigid fixed object.  Drivers traveling east on Highway 12 leaving Fairfield have been traveling down the rural highway for over 10 miles without so much as traveling through a traffic signal.  The posted speed limit is 55 mph and they are traveling at a downhill grade as they approach the Highway 12/Highway 113 roundabout.  For some drivers that roundabout could very easily sneak up on them which is a recipe for disaster once they encounter a concrete wall in the middle of the intersection. 
Title: Re: Crash prone 'modern roundabouts'
Post by: sparker on September 24, 2019, 06:21:17 PM
^^^^^^^^^^^
Unfortunately, Caltrans planning seems to be going through a prolonged phase of concept over reality; putting a roundabout on CA 12 anywhere between I-5 and I-80 -- a "shortcut" from the North Bay/"wine country" to Valley N-S arterials that avoids much of Bay traffic -- was and is a recipe for disaster, as evidenced by the fatality.  It's as if the prevailing "wisdom" (right!) is to attempt to micromanage rather than expedite open-road travel -- in this case, forcing high-speed through traffic into sporadic slowdowns to achieve -- well, what? -- a drop in the aggregate speed; a punitive measure for actually being out on the road to begin with!? -- the rationale, or lack thereof, behind putting obstacles in the way of rural through traffic is astonishing!  These are connecting corridors, folks, not parts of a miniature golf course!  I've been through 12/113 (pre-roundabout) numerous times; a channelized and signalized intersection -- with plenty of advance notice, particularly on 12 in both directions, would have been appropriate, not a center-of road structure.  I understand the desire of some planners to attempt to get folks out of their cars as much as possible -- but not through their windshields!
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 24, 2019, 07:14:14 PM
^^^^^^^^^^^
Unfortunately, Caltrans planning seems to be going through a prolonged phase of concept over reality; putting a roundabout on CA 12 anywhere between I-5 and I-80 -- a "shortcut" from the North Bay/"wine country" to Valley N-S arterials that avoids much of Bay traffic -- was and is a recipe for disaster, as evidenced by the fatality.  It's as if the prevailing "wisdom" (right!) is to attempt to micromanage rather than expedite open-road travel -- in this case, forcing high-speed through traffic into sporadic slowdowns to achieve -- well, what? -- a drop in the aggregate speed; a punitive measure for actually being out on the road to begin with!? -- the rationale, or lack thereof, behind putting obstacles in the way of rural through traffic is astonishing!  These are connecting corridors, folks, not parts of a miniature golf course!  I've been through 12/113 (pre-roundabout) numerous times; a channelized and signalized intersection -- with plenty of advance notice, particularly on 12 in both directions, would have been appropriate, not a center-of road structure.  I understand the desire of some planners to attempt to get folks out of their cars as much as possible -- but not through their windshields!

Based on your description, a signal is no better of a solution. Having people come to a complete stop in the middle of a rural 55-mph highway is no better than a roundabout. By your description, a grade separated interchange is the best solution, as any other form of intersection control has no choice but to negatively impact throughput on the mainline at some point.

I don't recall seeing one person defend the vertical concrete surface in the middle of the roundabout; can we finally move on?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 24, 2019, 09:02:22 PM
I don't recall seeing one person defend the vertical concrete surface in the middle of the roundabout; can we finally move on?

Your previous comment didn't sound like a ringing endorsement to get rid of retaining walls in the central islands of roundabouts.  Rather it sounded like you were questioning what would be a better way to go out...
 
Even if the concrete wasn't there, a basic mounded central island might not have changed the ultimate outcome. Depending on speed (which we still don't know), they could have been sent flying.

Of course if you catapult your vehicle high enough into the air, you may clear the dangerous fixed objects in the central island (boulders, retaining walls, trees, etc.).  Here's a few examples of this strategy (these are both non-fatal crashes):


Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on September 24, 2019, 09:06:13 PM
It's a new kind of runaway truck ramp.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 24, 2019, 09:38:11 PM
I don't recall seeing one person defend the vertical concrete surface in the middle of the roundabout; can we finally move on?

Your previous comment didn't sound like a ringing endorsement to get rid of retaining walls in the central islands of roundabouts.  Rather it sounded like you were questioning what would be a better way to go out...

How I missed tradephoric's cherry-picked commentary...said no one ever.  :rolleyes:

For your selective eyesight; the whole quote you selectively read (emphasis added):

Or maybe they would've killed innocent people in that other car.

Still didn't get to find out. Wouldn't you rather take a chance than just kill anyone who loses control?

I'm not trying to defend the placement of the concrete, but in order for it to kill someone, it isn't just losing control. Excessive speed plays a significant role. Look at the photo... there's plenty of warning. For crying out loud, there's two sets of overhead flashing lights. Even if the concrete wasn't there, a basic mounded central island might not have changed the ultimate outcome. Depending on speed (which we still don't know), they could have been sent flying.

Given the age of the occupants, there's no guarantee they would have survived hitting a breakaway street light. With age comes added frailty. Until the full report comes out, it could have been a medical condition before they ever hit anything. It could have been a heart attack when they crashed. Until we know the medical report and the speed they were traveling at saying the concrete killed them is only one hypothesis. Is placing vertical concrete in that location advisable? No. But it's not like the concrete randomly decided to spring up and yell "boo!"

The context was whether or not the concrete killed the occupants, not whether or not it should have been there in the first place.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 24, 2019, 11:52:02 PM
The word 'but' is used to nullify all words preceding it and implies the sentence said before it wasn't worth saying.  Someone's true feelings always comes after the word but, not before.
I'm not trying to defend the placement of the concrete, but in order for it to kill someone, it isn't just losing control. Excessive speed plays a significant role. Look at the photo... there's plenty of warning. For crying out loud, there's two sets of overhead flashing lights. Even if the concrete wasn't there, a basic mounded central island might not have changed the ultimate outcome. Depending on speed (which we still don't know), they could have been sent flying.

Given the age of the occupants, there's no guarantee they would have survived hitting a breakaway street light. With age comes added frailty. Until the full report comes out, it could have been a medical condition before they ever hit anything. It could have been a heart attack when they crashed. Until we know the medical report and the speed they were traveling at saying the concrete killed them is only one hypothesis. Is placing vertical concrete in that location advisable? No. But it's not like the concrete randomly decided to spring up and yell "boo!"
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 25, 2019, 12:30:10 AM
Tradephoric, you're taking the statements out of context regardless of the presence of the word 'but' and you know it. STFU with your word games. Whatever I say doesn't matter, since you only hear what you want to hear. Do yourself a favor and ignore my posts; I am done putting up with your BS.
Title: Re: Crash prone 'modern roundabouts'
Post by: sparker on September 25, 2019, 12:59:31 AM
^^^^^^^^^^^
Unfortunately, Caltrans planning seems to be going through a prolonged phase of concept over reality; putting a roundabout on CA 12 anywhere between I-5 and I-80 -- a "shortcut" from the North Bay/"wine country" to Valley N-S arterials that avoids much of Bay traffic -- was and is a recipe for disaster, as evidenced by the fatality.  It's as if the prevailing "wisdom" (right!) is to attempt to micromanage rather than expedite open-road travel -- in this case, forcing high-speed through traffic into sporadic slowdowns to achieve -- well, what? -- a drop in the aggregate speed; a punitive measure for actually being out on the road to begin with!? -- the rationale, or lack thereof, behind putting obstacles in the way of rural through traffic is astonishing!  These are connecting corridors, folks, not parts of a miniature golf course!  I've been through 12/113 (pre-roundabout) numerous times; a channelized and signalized intersection -- with plenty of advance notice, particularly on 12 in both directions, would have been appropriate, not a center-of road structure.  I understand the desire of some planners to attempt to get folks out of their cars as much as possible -- but not through their windshields!

Based on your description, a signal is no better of a solution. Having people come to a complete stop in the middle of a rural 55-mph highway is no better than a roundabout. By your description, a grade separated interchange is the best solution, as any other form of intersection control has no choice but to negatively impact throughput on the mainline at some point.

I don't recall seeing one person defend the vertical concrete surface in the middle of the roundabout; can we finally move on?

When it comes to a signalized intersection at the 12/113 junction, I clearly mentioned quite a bit of advance notice; previous Caltrans installations of this type have placed warnings of a red signal phase in the form of flashing notification to that effect at least 3/4 mile back from the interchange itself.  That has proven to be quite effective at getting traffic to slow down if and when a red signal is imminent; ample time & space to drop from 65-70 to zero.  I doubt whether advance notification of this sort is placed for a roundabout; the ones I've encountered simply have stepped speed drops.  I'm just questioning the appropriateness of this format in high-speed non-urban situations; it seems like the "garbage can" method -- a solution searching for a problem!
Title: Re: Crash prone 'modern roundabouts'
Post by: ET21 on September 25, 2019, 09:17:28 AM
 :popcorn:
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 25, 2019, 06:34:30 PM
Engineers typically build things with multiple redundancies, to avoid catastrophic failure (look up all the redundancies for the Tower of Terror...really amazing stuff). Traffic lights technically have a fail-safe operation: if someone approaches an intersection without noticing the signal, they can, hypothetically, pass through it unharmed because there are no obstacles directly in front of them other than other cars (which there would be at roundabouts too, so it's still a fair comparison).

Sorry, I have a hard time agreeing with the notion that traffic lights have fail-safe operation. Russian roulette-style fail-safe, maybe. Miss the signal and you are either really lucky, or fail in a really ugly fashion. At least with a roundabout, you have the chance the splitter island curb will slow-down or redirect a errant vehicle (granted, those chances decrease on multilane approaches).

But traffic lights aren't red all the time. The comparison is not red light vs roundabout. The comparison is traffic signal vs roundabout. At a roundabout, if you approach one without paying attention, you will crash, in some way. It is impossible not to. But at a traffic light, assuming you're approaching it without paying attention, there's a decent chance that either A) the signal will be green when you arrive, allowing you to pass through unharmed (assuming you can at least stay in your lane), or B) the light will be red but there won't be any cars in the intersection. On the flip side, C) the light could be red and you'll whack into the backside of waiting traffic, or D) the light is red and you T-bone another car.

Of course, scenarios C and D can be absolutely horrific crashes, usually the kind of crash when people end up either seriously injured or killed. And both are likely the reason that roundabouts became popular state-side (to curb those serious T-bone collisions). What I don't think roundabout engineers have fully considered, is how many people are distracted by something they're doing in the car (literally anything from adjusting the radio, to putting on makeup, or using their phone). More often than not, these people are not going to kill themselves approaching a roundabout, but they could by A) crashing into a concrete central island, B) T-boning a car going around the central island (assuming they don't make it to the central island), or C) taking last-second evasive action and rolling their car (also possible at a signal, to be fair, although more likely at roundabouts because one cannot simply drive through a central island without crashing).

Despite everything I've said, I'm actually still a proponent of roundabouts. But I feel there is good roundabout design, and bad roundabout design. I'm not trying to be Dieter Rams, and I'm certainly not an engineer with loads of evidence on my side, but hear me out: good roundabout design would be,

* large enough central island that could accommodate a crashing car
* approaches that do not feature chicanes (promotes lane drifting, side-swiping)
* right-angle approaches (approaches tangential to the circulating roadway promote failure to yield and high speeds, but still require driver action to avoid crashing...may as well require hard-right turns)

This roundabout in Federal Way, WA (https://goo.gl/maps/ZYNYfmGkPNsZvENB7) (opened 2004) fits my criteria pretty well; the historic trees in the middle are surrounded by bushes that might help slow approaching traffic, should someone approach at high speed; I would personally remove the trees in favor of dense, forgiving foliage, but it's otherwise quite good:

(https://i.imgur.com/zdVoRVp.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 25, 2019, 08:27:56 PM
Sorry, I have a hard time agreeing with the notion that traffic lights have fail-safe operation. Russian roulette-style fail-safe, maybe. Miss the signal and you are either really lucky, or fail in a really ugly fashion. At least with a roundabout, you have the chance the splitter island curb will slow-down or redirect a errant vehicle (granted, those chances decrease on multilane approaches).

There are lots of inaccuracies in this paragraph.  DaBigE compares 'missing the signal' (ie. blowing through a red light) to a game of Russian roulette.  In Russian roulette there is a 83% chance that you survive each pull of the trigger.  Using DaBigE's analogy, if a driver has an 83% chance of making it through a red light without getting hit, it would actually be 'really unlucky' if they got hit (which is opposite of what was being argued).  And who says that when a crash occurs that it will be a "fail in a really ugly fashion"?  I've witnessed a t-bone crash at a traffic signal that resulted in nothing more than a love tap.  I'll admit that horrendous accidents can occur at traffic signals, but it's foolish to suggest they always do.  Lastly, the curbing at roundabouts redirecting an errant vehicle isn't necessarily a safety feature... many motorcyclists have died after striking the curbing inside a roundabout. 
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 25, 2019, 08:34:57 PM
Engineers typically build things with multiple redundancies, to avoid catastrophic failure (look up all the redundancies for the Tower of Terror...really amazing stuff). Traffic lights technically have a fail-safe operation: if someone approaches an intersection without noticing the signal, they can, hypothetically, pass through it unharmed because there are no obstacles directly in front of them other than other cars (which there would be at roundabouts too, so it's still a fair comparison).

Sorry, I have a hard time agreeing with the notion that traffic lights have fail-safe operation. Russian roulette-style fail-safe, maybe. Miss the signal and you are either really lucky, or fail in a really ugly fashion. At least with a roundabout, you have the chance the splitter island curb will slow-down or redirect a errant vehicle (granted, those chances decrease on multilane approaches).

But traffic lights aren't red all the time. The comparison is not red light vs roundabout. The comparison is traffic signal vs roundabout. At a roundabout, if you approach one without paying attention, you will crash, in some way. It is impossible not to. But at a traffic light, assuming you're approaching it without paying attention, there's a decent chance that either A) the signal will be green when you arrive, allowing you to pass through unharmed (assuming you can at least stay in your lane), or B) the light will be red but there won't be any cars in the intersection. On the flip side, C) the light could be red and you'll whack into the backside of waiting traffic, or D) the light is red and you T-bone another car.

True, a traffic light isn't red all the time; however, that still does not eliminate the possibility of a fatal collision at a traffic light. You could have the green light and be the innocent victim of someone running the red light for the other roadway. Neither control is perfect, but I'd rather take my chances at a roundabout, where statistically, I am more likely to be able to walk away from a crash.

Despite everything I've said, I'm actually still a proponent of roundabouts. But I feel there is good roundabout design, and bad roundabout design. I'm not trying to be Dieter Rams, and I'm certainly not an engineer with loads of evidence on my side, but hear me out: good roundabout design would be,

* large enough central island that could accommodate a crashing car
* approaches that do not feature chicanes (promotes lane drifting, side-swiping)
* right-angle approaches (approaches tangential to the circulating roadway promote failure to yield and high speeds, but still require driver action to avoid crashing...may as well require hard-right turns)

Unfortunately, there is a finite limit to how large a central island can be and still have effective speed control. The larger the central island, the more distance circulating traffic has to speed up, the more severe a circulating crash can be. Likewise, while most good roundabout designers try to avoid chicanes, they may be a necessary element of approach speed control, due to site constraints. Hard right turns on the entry have the worst sight conditions for the yielding driver. Too flat of an entry promotes vehicles speeding up upon entering the circle (what some designers refer to as a 'hockey stick' design).

This story is floating around numerous engineering forums I follow as well. There is some discussion that the final design for the CA roundabout includes sloped soil/landscaping on the outside of the concrete ring, ultimately limiting the exposure of the concrete face. If that is true, and there was no medical event prior to the crash, we may be looking at a poor construction staging. There's the chance that the final design might have resulted in the vehicle only getting stuck in the central island; depending on the speed, it could result in someone vaulting. Until we know the results of the crash report, everything is pure speculation.

If this intersection was up to me (and I was told it had to be a roundabout), the use of concrete in the central island would limited to curb and gutter and the truck apron only.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 25, 2019, 08:49:06 PM
^^^^^^^^^^^
Unfortunately, Caltrans planning seems to be going through a prolonged phase of concept over reality; putting a roundabout on CA 12 anywhere between I-5 and I-80 -- a "shortcut" from the North Bay/"wine country" to Valley N-S arterials that avoids much of Bay traffic -- was and is a recipe for disaster, as evidenced by the fatality.  It's as if the prevailing "wisdom" (right!) is to attempt to micromanage rather than expedite open-road travel -- in this case, forcing high-speed through traffic into sporadic slowdowns to achieve -- well, what? -- a drop in the aggregate speed; a punitive measure for actually being out on the road to begin with!? -- the rationale, or lack thereof, behind putting obstacles in the way of rural through traffic is astonishing!  These are connecting corridors, folks, not parts of a miniature golf course!  I've been through 12/113 (pre-roundabout) numerous times; a channelized and signalized intersection -- with plenty of advance notice, particularly on 12 in both directions, would have been appropriate, not a center-of road structure.  I understand the desire of some planners to attempt to get folks out of their cars as much as possible -- but not through their windshields!

Based on your description, a signal is no better of a solution. Having people come to a complete stop in the middle of a rural 55-mph highway is no better than a roundabout. By your description, a grade separated interchange is the best solution, as any other form of intersection control has no choice but to negatively impact throughput on the mainline at some point.

I don't recall seeing one person defend the vertical concrete surface in the middle of the roundabout; can we finally move on?

When it comes to a signalized intersection at the 12/113 junction, I clearly mentioned quite a bit of advance notice; previous Caltrans installations of this type have placed warnings of a red signal phase in the form of flashing notification to that effect at least 3/4 mile back from the interchange itself.  That has proven to be quite effective at getting traffic to slow down if and when a red signal is imminent; ample time & space to drop from 65-70 to zero.  I doubt whether advance notification of this sort is placed for a roundabout; the ones I've encountered simply have stepped speed drops.  I'm just questioning the appropriateness of this format in high-speed non-urban situations; it seems like the "garbage can" method -- a solution searching for a problem!

With any rural roundabout projects that I've been involved with,* there is plenty of advanced warning. At the very least, there are two sets of warning signs, but depending on the site, flashing beacon lights and rumble strips are also used. That is in addition to the roadway geometry queues. While I cannot speak for Caltrans decision methods, I can say that the states I've worked in have formal decision reports (aka Intersection Control Evaluations: "ICE Reports"). The decision to install a roundabout is not as thoughtless as some believe it to be.

*none have been on a facility with speeds higher than 55 mph
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 25, 2019, 10:44:25 PM
While I cannot speak for Caltrans decision methods, I can say that the states I've worked in have formal decision reports (aka Intersection Control Evaluations: "ICE Reports"). The decision to install a roundabout is not as thoughtless as some believe it to be.

Regardless of the decision making process to install a roundabout, once installed agencies don't want to admit that it may have been the wrong decision.  I recently heard a presentation from Paul C. Ajegba, the director of MDOT, discussing the 14 Mile & Orchard Lake roundabout.  He actually admitted he was initially skeptical of the roundabout design but since it opened he has been impressed with how it has operated.  This is the same roundabout that saw a huge spike in total crashes with no significant drop in injury crashes when converted from a traffic signal to a roundabout in 2015.  In 2018 alone the roundabout saw 144 crashes including 20 injury crashes.  Yet you have the director of MDOT praising how well it's operating?  It's like he's willfully ignorant to the crash problem at the roundabout.  No mention of crashes at all.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on September 26, 2019, 12:38:21 PM
A couple of years ago, I ran a red light and crashed into a car going the other way.  We were both going less than 30 mph, I wasn't fiddling with the radio or using my cell phone or on medication or anything like that.  I was simply concerned that I had missed my turn and was looking the other way to confirm or deny my suspicion, rather than paying attention to the color of the stoplight.  Even at such a low speed, my car pushed his up onto the sidewalk, the whole side of his car was caved in, his airbag deployed, and he was having trouble breathing due to an apparent asthma attack.  The front end of my car's frame was bent and eventually ended up being totaled out by insurance.  Ultimately, both of us were OK, and I didn't even suffer any injury at all.  On the one hand, I'm glad I hit a car in motion rather than a concrete wall.  But on the other hand, I'm also glad we weren't going 45 mph instead of less than 30.

And who says that when a crash occurs that it will be a "fail in a really ugly fashion"?  I've witnessed a t-bone crash at a traffic signal that resulted in nothing more than a love tap.

I've never seen a T-bone crash result "in nothing more than a love tap", and I doubt many others have either.  But I've seen the aftermath of plenty of much more severe T-bone accidents, have witnessed a couple of them happen firsthand, and, as already stated, have been involved in one myself.

Nothing about a traditional stoplight does anything to slow a driver down.  There's a stoplight intersection between Andover and Augusta (KS), for example, on a four-lane US Route with a 65mph speed limit.  Drivers encounter two yellow warning signs in advance (one with a flashing yellow beacon that stays on all the time) but, other than that, there's nothing to slow a driver down.  Other than signs and lights, nothing about it encourages a driver to slow down at all.

In contrast, roundabouts on high-speed roads are commonly constructed to include (as DaBigE said, "two sets of warning signs … flashing beacon lights ... rumble strips … roadway geometry".  And that's not to mention the fact that there's something visible directly in front of you as you approach one.  Everything about a roundabout screams "SLOW DOWN".

the curbing at roundabouts redirecting an errant vehicle isn't necessarily a safety feature... many motorcyclists have died after striking the curbing inside a roundabout. 

You were replying to a post related to the curbing of a splitter island and then countered with a statement about the curbing inside a roundabout.  Which one are you talking about?  Also, just because some people wreck or die while striking a safety feature, that doesn't mean it isn't a safety feature.  If I run my car into a guardrail, roll my vehicle, break my neck, and die–that doesn't mean guardrails aren't "necessarily a safety feature".  It just means safety features don't save everyone, and every so often have the opposite effect.

Regardless of the decision making process to install a roundabout, once installed agencies don't want to admit that it may have been the wrong decision.

As opposed to how willing they are to admit they made the wrong decision with other types of installations?
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on September 26, 2019, 12:55:22 PM
If drivers are going to ignore or miss two sets of warning signs, other traffic control features, and the appearance of the roundabout itself, then fuck 'em. No DOT should be beholden to try to accommodate that level of obliviousness. I get that people want roads to "fail safe," but there's a certain level at which you just have to throw your hands up and say "I give up."
Title: Re: Crash prone 'modern roundabouts'
Post by: sparker on September 26, 2019, 09:19:51 PM
^^^^^^^^^^^
One of the basic differences between a signalized intersection and one that's been retrofitted with a roundabout is the fact that with the former -- depending, of course, on the traffic flow of each of the intersecting roads -- a signal can be set to normally display a green/through aspect for the roadway with the greatest traffic flow, with traffic either from the crossroad or a left-turning motion from that main road (which would generally entail only a traffic interruption for the opposite direction) triggering a red/"stop" signal aspect.  From my own experience with the CA 12/113 intersection, that would mean that about 75-80% of the time the traffic flow on CA 12 would not be impaired.  Contrast that to the roundabout, where 100% of the time through traffic on CA 12 is forced to a crawl in order to negotiate the configuration.  Caltrans has plenty of experience with installations with advance warnings of a stop aspect; installing one on CA 12 wouldn't be rocket science, just another application of a method they've used in the past (pioneered, in fact, on CA 99 in Merced and Stanislaus Counties prior to full freeway completion).  IMO, the concept of placing such installations on higher-speed rural routes is either (a) a "sop" to agency personnel (or political oversight) who have an inherent bias against automotive travel in general, or (b) an application of a temporal "one size fits all" approach to such issues -- with the current "fan favorite" being the roundabout.  It's one thing to attempt to make auto travel in the city a less favorable experience vis-à-vis non-automotive alternatives -- but to try to extend that rationale to the heretofore open road seems gratuitous at best and downright obnoxious at worst.  I say the following a bit jokingly -- but given the recent spate of mechanical failures of the lift mechanism of the CA 12 Rio Vista/Sacramento River bridge (which has caused a series of backups on that highway), perhaps the roundabout was considered a way to create a "holding pattern" in the EB direction to minimize the potential for rear-enders if and when a stationary line of cars in the travel lane is encountered.  If so, that seems to be similar to trying to install a picture-hanging hook on a wall with a sledgehammer!  CA 12 is the main artery from southward I-5 and CA 99 to the Napa Valley and other North Bay regional destinations for folks looking to bypass Bay Area congestion; dropping obstacles in that traffic path will just result in a number of folks looking to make up time by doing 75-80+ on that mostly two-lane road; turning it into a social experiment may not be the best use of scarce construction funds!
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 26, 2019, 11:14:21 PM
^^^^^^^^^^^
One of the basic differences between a signalized intersection and one that's been retrofitted with a roundabout is the fact that with the former -- depending, of course, on the traffic flow of each of the intersecting roads -- a signal can be set to normally display a green/through aspect for the roadway with the greatest traffic flow, with traffic either from the crossroad or a left-turning motion from that main road (which would generally entail only a traffic interruption for the opposite direction) triggering a red/"stop" signal aspect.  From my own experience with the CA 12/113 intersection, that would mean that about 75-80% of the time the traffic flow on CA 12 would not be impaired.  Contrast that to the roundabout, where 100% of the time through traffic on CA 12 is forced to a crawl in order to negotiate the configuration.  Caltrans has plenty of experience with installations with advance warnings of a stop aspect; installing one on CA 12 wouldn't be rocket science, just another application of a method they've used in the past (pioneered, in fact, on CA 99 in Merced and Stanislaus Counties prior to full freeway completion).  IMO, the concept of placing such installations on higher-speed rural routes is either (a) a "sop" to agency personnel (or political oversight) who have an inherent bias against automotive travel in general, or (b) an application of a temporal "one size fits all" approach to such issues -- with the current "fan favorite" being the roundabout.  It's one thing to attempt to make auto travel in the city a less favorable experience vis-à-vis non-automotive alternatives -- but to try to extend that rationale to the heretofore open road seems gratuitous at best and downright obnoxious at worst.  I say the following a bit jokingly -- but given the recent spate of mechanical failures of the lift mechanism of the CA 12 Rio Vista/Sacramento River bridge (which has caused a series of backups on that highway), perhaps the roundabout was considered a way to create a "holding pattern" in the EB direction to minimize the potential for rear-enders if and when a stationary line of cars in the travel lane is encountered.  If so, that seems to be similar to trying to install a picture-hanging hook on a wall with a sledgehammer!  CA 12 is the main artery from southward I-5 and CA 99 to the Napa Valley and other North Bay regional destinations for folks looking to bypass Bay Area congestion; dropping obstacles in that traffic path will just result in a number of folks looking to make up time by doing 75-80+ on that mostly two-lane road; turning it into a social experiment may not be the best use of scarce construction funds!

How can you make operational claims before the project is even completed? Have you seen any of the operational analyses? Do you know what the projected delays are for the roundabout? Does anyone have access to the traffic volumes for this intersection? If the approaches are fairly balanced, the roundabout generally will have better operations (to about 40K entering VPD); however, if one road is significantly heavier, then a signal typically will be the better operational choice.

Can you define what you mean by "impaired"? Dropping from 55 mph to 20 mph over the size of the roundabout adds a minuscule amount of travel time at free flow conditions (off-peak), while also significantly reducing (eliminating?) unnecessary side street control delay that would occur if the same intersection was signalized.

Being a rural intersection, trying to inhibit travel by auto doesn't seem to apply here. I don't think I've ever come across such perceived "benefit" of a rural intersection project. The fact that they're making any improvements contradicts the anti-car conspiracy theory. If they truly wanted to discourage travel by car, zero lane improvements would be made, except for a bus stop or bike lanes.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 27, 2019, 11:53:49 AM
If drivers are going to ignore or miss two sets of warning signs, other traffic control features, and the appearance of the roundabout itself, then fuck 'em. No DOT should be beholden to try to accommodate that level of obliviousness. I get that people want roads to "fail safe," but there's a certain level at which you just have to throw your hands up and say "I give up."
I understand the “I give up”  mindset when something bad happens at a roundabout.  We have been told that roundabouts reduce fatal crashes by 90% so when something bad happens many try to excuse it away and assume it was an outlier.   Overhead advanced warning flashers and warning signs existed at the flasher that preceded the roundabout yet the same “I give up”  mindset was absent then.
   
In contrast, roundabouts on high-speed roads are commonly constructed to include (as DaBigE said, "two sets of warning signs … flashing beacon lights ... rumble strips … roadway geometry".  And that's not to mention the fact that there's something visible directly in front of you as you approach one.  Everything about a roundabout screams "SLOW DOWN".
Having visible objects in the central island can be beneficial to reduce the likelihood of a vehicle plowing through the middle of a roundabout, but do those objects need to be rigid?  The 96th Street and Westfield Blvd roundabout in Carmel has been the site of multiple fatal crashes and in both cases the driver blew through the middle of the roundabout and crashed into a concrete retaining wall.  Instead of a concrete wall, why not just have some visible brush/plantings like this to alert the driver they got to slow down?  At least if they still don't slow down they only blow through some flower gardens...

(https://i.imgur.com/yeGNpGY.png)

EDIT:  The picture above was taken at the 96th Street and Westfield Blvd roundabout in Carmel.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 27, 2019, 02:23:01 PM
^^
Glad you brought up that 96th/Westfield roundabout. In this BBC article from 2011 (https://www.bbc.com/news/magazine-13863498), where they went to Carmel and interviewed the mayor and made comparisons to Milton Keynes, they drive through this roundabout (in the attached video, skip to 0:56):

"This used to be stoplight. This is actually one of the conversions. Someday we'll [put a] sculpture in the middle -- that's a budget item".

I've noticed that the roundabout does now indeed have  a sculpture in the middle. Because the concrete wall wasn't enough of an obstacle.

(https://i.imgur.com/5o1wg6a.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on September 27, 2019, 02:55:13 PM
Does anyone have access to the traffic volumes for this intersection? If the approaches are fairly balanced, the roundabout generally will have better operations (to about 40K entering VPD); however, if one road is significantly heavier, then a signal typically will be the better operational choice.

2017 numbers

(https://i.imgur.com/4nYvSzW.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 27, 2019, 04:18:48 PM
I was hoping to find some GIS data from Caltrans, which might help illustrate TOD operations, but their website is currently offline while they upgrade their systems.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 27, 2019, 04:20:26 PM
^^
Glad you brought up that 96th/Westfield roundabout. In this BBC article from 2011 (https://www.bbc.com/news/magazine-13863498), where they went to Carmel and interviewed the mayor and made comparisons to Milton Keynes, they drive through this roundabout (in the attached video, skip to 0:56):

"This used to be stoplight. This is actually one of the conversions. Someday we'll [put a] sculpture in the middle -- that's a budget item".

I've noticed that the roundabout does now indeed have  a sculpture in the middle. Because the concrete wall wasn't enough of an obstacle.

(https://i.imgur.com/5o1wg6a.png)

Thank you for this additional info Jake.  Designing the roundabout with a concrete retaining wall makes a little more sense assuming the city had always planned a sculpture there.  That being said, it took over a decade before the sculpture was added and both fatal crashes occurred before the sculpture was installed.  In the video you linked from that 2011 BBC article, the retaining wall is largely obscured by the foliage surrounding it (just like it is in the streetview image i linked).  The foliage hides the very real dangers of that fixed object retaining well.  At least with the large sculpture now installed it is much more prevalent that a fixed object exists in the central island.  I wish no fixed object existed in the central island but at least now it stands out.

BTW, i knew the city installed that sculpture in 2017 (it was discussed previously in this thread) i just didn't realize the mayor of Carmel was talking about it way back in 2011. 
Title: Re: Crash prone 'modern roundabouts'
Post by: sparker on September 28, 2019, 02:12:30 AM
Does anyone have access to the traffic volumes for this intersection? If the approaches are fairly balanced, the roundabout generally will have better operations (to about 40K entering VPD); however, if one road is significantly heavier, then a signal typically will be the better operational choice.

2017 numbers

(https://i.imgur.com/4nYvSzW.png)

I'd say that a 275% difference in traffic flow (derived from the smaller of the CA 12 numbers) qualifies as significant.   I'll simply reiterate that IMO the present Caltrans penchant for utilizing roundabouts as their default favored configuration is at best misguided and at worst gratuitous and potentially dangerous.   Let's just hope that common sense (and San Benito County residents) can convince D5 that installing one of these at the CA 25/156 intersection is not only wrongheaded but will likely produce a plethora of unintended consequences (and a spike in collisions in the process).   
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on September 28, 2019, 11:49:14 AM
Does anyone have access to the traffic volumes for this intersection? If the approaches are fairly balanced, the roundabout generally will have better operations (to about 40K entering VPD); however, if one road is significantly heavier, then a signal typically will be the better operational choice.

2017 numbers

(https://i.imgur.com/4nYvSzW.png)

Thanks for posting that. Any chance they have the turn movement counts? On the surface, it looks unbalanced, but since CA 12 intersects another state highway, the peak hour turning patterns may tell a slightly different story. If there are a significant number of left turns from CA 12 (EB?) to CA 113, that tends to create more gaps for traffic entering from CA 113, and offset some of the bias of CA 12 through traffic.
Title: Re: Crash prone 'modern roundabouts'
Post by: sparker on September 28, 2019, 12:39:50 PM
Does anyone have access to the traffic volumes for this intersection? If the approaches are fairly balanced, the roundabout generally will have better operations (to about 40K entering VPD); however, if one road is significantly heavier, then a signal typically will be the better operational choice.

2017 numbers

(https://i.imgur.com/4nYvSzW.png)

Thanks for posting that. Any chance they have the turn movement counts? On the surface, it looks unbalanced, but since CA 12 intersects another state highway, the peak hour turning patterns may tell a slightly different story. If there are a significant number of left turns from CA 12 (EB?) to CA 113, that tends to create more gaps for traffic entering from CA 113, and offset some of the bias of CA 12 through traffic.

CA 12, while mostly 2 lanes (with periodic passing lanes in both directions) is, except for one narrow bridge over the old Sacramento Northern railroad tracks (which can't be replaced without a far-flung bypass since it's on the grounds of the Bay Area Railroad Museum), a facility with wide banked curves designed for travel at the state 65mph surface-road speed limit.  OTOH, CA 113 is a narrow 2-lane rural facility with a couple of sharp right-angle curves that tend to inhibit travel by larger commercial vehicles.   Not much in the way of overall consistent volume south of the town of Dixon.  That being said, the primary use seems to be an ersatz "bypass" of Sacramento (which experiences "normal" commute congestion), particularly used by UC Davis students from points south (the sporadic mechanical failures of the CA 12 Rio Vista bridge notwithstanding!) -- but that traffic still doesn't come close to crowding the section of CA 113 from CA 12 to I-80.  Traffic using it as a bypass is relatively minimal (contained easily within that 5100 AADT); most of the consistent traffic is related to the agricultural area (CA's prime tomato-producing region) through which it passes.  Trust me on this one, you don't want to be behind an open-bed truck hauling tomatoes when it hits a bump or pothole; you'll get squashed tomatoes on your windshield and in your grill!  There is some tomato traffic heading south on 113 to east 12 (a few processing plants in the Lodi/Stockton area), but most transport the fruit from somewhere near 113 northward to I-80 to head for the major processors in SE Sacramento ("Sacramento" brand tomato juice, ubiqutous on the East Coast, hails from there, along with much of commercial/OEM juice production).   Maybe during next years' harvest season I'll get my ass out to the 12/113 roundabout to see if trucks negotiating that facility has resulted in squashed tomatoes either within the circle center or around the periphery!
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 29, 2019, 09:47:41 PM
For fun, I prepared a redesign of the intersection.

* traffic approaching from the south must turn right and then U-turn to continue onto northbound CA-113 or westbound CA-12;
* traffic approaching from the west must go straight and then U-turn to access northbound CA-113;
* traffic approaching from the north may go in any direction (left lane would be left turn only);
* traffic approaching from the east may go in any direction (changing one lane to the right to continue onto northbound CA-113 unimpeded).

Operational notes:

* traffic from the south would have a flashing right red arrow (except for the slip lane) during the oncoming green arrow phase, assuming this is allowed;
* the left turn from westbound CA-12 could operate with a flashing yellow arrow, if Caltrans were to be so bold (the visibility would be perfectly acceptable);
* the U-turn would operate as yield-only (it appears to be a quiet movement);
* the slip lanes in the SW and SE corners operate with yield signs;
* the slip lanes in the NW and NE corners would be free-flow maneuvers;
* I did not draw any pedestrian facilities, but could easily modify the design to incorporate these if so desired.

(https://i.imgur.com/B7kNAP3.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: sparker on September 30, 2019, 03:33:56 AM
For fun, I prepared a redesign of the intersection.

* traffic approaching from the south must turn right and then U-turn to continue onto northbound CA-113 or westbound CA-12;
* traffic approaching from the west must go straight and then U-turn to access northbound CA-113;
* traffic approaching from the north may go in any direction (left lane would be left turn only);
* traffic approaching from the east may go in any direction (changing one lane to the right to continue onto northbound CA-113 unimpeded).

Operational notes:

* traffic from the south would have a flashing right red arrow (except for the slip lane) during the oncoming green arrow phase, assuming this is allowed;
* the left turn from westbound CA-12 could operate with a flashing yellow arrow, if Caltrans were to be so bold (the visibility would be perfectly acceptable);
* the U-turn would operate as yield-only (it appears to be a quiet movement);
* the slip lanes in the SW and SE corners operate with yield signs;
* the slip lanes in the NW and NE corners would be free-flow maneuvers;
* I did not draw any pedestrian facilities, but could easily modify the design to incorporate these if so desired.

(https://i.imgur.com/B7kNAP3.png)

That is one nice design!  It keeps the most essential turning movements:  S>E and W>N intact as simple directional motions while addressing the less-utilized movements -- all while maintaining the primacy of through traffic on CA 12.  Much better than (a) the original or (b) the roundabout replacement.  Because of the slightly hilly terrain, which extends east along CA 12 for a mile or two, an advance safety indicator (signage + flashing yellow?) on WB CA 12 prior to the U-turn may be appropriate; otherwise, the cited measures should be sufficient 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 30, 2019, 01:43:01 PM
Good job Jake, that design of CA 12/CA 113 looks great.  I may not have extended the left turn lane through the intersection for traffic traveling EB CA 12 as that left-turning movement is likely pretty low, but at the same time I'd rather have too much queue space than not enough!  The safety benefits of innovative intersections that eliminate direct left turns often seems overlooked.  Past research has found 20-50% reductions in total crashes at Median U-Turn intersections compared to conventional intersections.  That's why i take issue with the IIHS blanket statement that "roundabouts are a safer alternative to traffic signals and stop signs".  That's the first thing you read when you go to the IIHS roundabout website.  Roundabouts may be a safer alternative to conventional traffic signals but not necessarily innovative intersections like what Jake drew up.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on September 30, 2019, 02:23:38 PM


Does anyone have access to the traffic volumes for this intersection? If the approaches are fairly balanced, the roundabout generally will have better operations (to about 40K entering VPD); however, if one road is significantly heavier, then a signal typically will be the better operational choice.

2017 numbers

(https://i.imgur.com/4nYvSzW.png)

Thanks for posting that. Any chance they have the turn movement counts? On the surface, it looks unbalanced, but since CA 12 intersects another state highway, the peak hour turning patterns may tell a slightly different story. If there are a significant number of left turns from CA 12 (EB?) to CA 113, that tends to create more gaps for traffic entering from CA 113, and offset some of the bias of CA 12 through traffic.

I didn't see any turning movement counts, but I did see peak counts.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 01, 2019, 01:17:55 AM
That is one nice design!  It keeps the most essential turning movements:  S>E and W>N intact as simple directional motions while addressing the less-utilized movements -- all while maintaining the primacy of through traffic on CA 12.  Much better than (a) the original or (b) the roundabout replacement.  Because of the slightly hilly terrain, which extends east along CA 12 for a mile or two, an advance safety indicator (signage + flashing yellow?) on WB CA 12 prior to the U-turn may be appropriate; otherwise, the cited measures should be sufficient
Good job Jake, that design of CA 12/CA 113 looks great.  I may not have extended the left turn lane through the intersection for traffic traveling EB CA 12 as that left-turning movement is likely pretty low, but at the same time I'd rather have too much queue space than not enough!  The safety benefits of innovative intersections that eliminate direct left turns often seems overlooked.  Past research has found 20-50% reductions in total crashes at Median U-Turn intersections compared to conventional intersections.  That's why i take issue with the IIHS blanket statement that "roundabouts are a safer alternative to traffic signals and stop signs".  That's the first thing you read when you go to the IIHS roundabout website.  Roundabouts may be a safer alternative to conventional traffic signals but not necessarily innovative intersections like what Jake drew up.

Thanks guys.

If I had to do the redesign again, I would have also opted for a U-turn lane that started after the intersection, rather than before, but I wasn't sure what the turning movements were, so I opted for a more liberal design. I think a warning sign for westbound traffic would certainly be warranted, as they might not be aware of that U-turning traffic. The U-turn could also be relocated if visibility concerns persist.

I do feel like more innovative intersections are what we need in this country. We seem to be applying roundabouts and DDI's far more than I think may be truly necessary. They both have their places, but I'm not 100% sure its where many of them are built, or are being built. Intersections that maybe combine a bit of everything really need more consideration, at least in areas where there is enough ROW.

For this intersection, I knew that the southbound to eastbound maneuver was really heavy, so I opted to design it as regular left turn. But due to the offset with the private road, this required some alternative considerations for the left turn from that road, as well as the left turns off CA-12. Combining a couple of those turns into the U-turn, and leaving two of the original left turns, got me to what you see above.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 14, 2019, 08:35:04 PM
Even if the concrete wasn't there, a basic mounded central island might not have changed the ultimate outcome. Depending on speed (which we still don't know), they could have been sent flying.

It seems like race car drivers have more common sense than some of the engineers designing these roundabouts.  After flipping wildly late in the race at Talladega today, Brendan Gaughan jumped out of his car unscathed and had this to say...

Quote
"The easiest thing you can do in a race car is go upside down... nothing hits hard.  So that's the nicest thing about it..."

While a wild flip may look spectacular, each impact is dissipating energy and you don't get that 'dead stop'.  That's not to say flipping can't be deadly (and Brendan was making a pretty big generalization) but I'd take my chances over hitting a wall.  If Brendan was designing a rural roundabout he wouldn't have designed it with a concrete wall in the central island... just asking to kill someone when struck.  Here is a video of 100 Nascar flips, none of which were fatal.


Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 14, 2019, 08:46:25 PM
A driver was killed last Tuesday at a roundabout in Liberty Lake, WA after striking a concrete retaining wall in the central island of a roundabout.  They should change the headline to read "Alcohol, speed, and a concrete retaining wall believed to be factor in man's fatal crash into Liberty Lake roundabout". 

Alcohol, speed believed to be factor in man's fatal crash into Liberty Lake roundabout
https://www.khq.com/news/police-alcohol-speed-believed-to-be-factor-in-man-s/article_a40e0da6-e9c4-11e9-af1e-d7c910840c47.html
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 15, 2019, 12:44:15 AM
A driver was killed last Tuesday at a roundabout in Liberty Lake, WA after striking a concrete retaining wall in the central island of a roundabout.  They should change the headline to read "Alcohol, speed, and a concrete retaining wall believed to be factor in man's fatal crash into Liberty Lake roundabout". 

Alcohol, speed believed to be factor in man's fatal crash into Liberty Lake roundabout
https://www.khq.com/news/police-alcohol-speed-believed-to-be-factor-in-man-s/article_a40e0da6-e9c4-11e9-af1e-d7c910840c47.html

God dammit. I thought my area was smarter than this. That's a brand new roundabout too.

The other roundabout, just a bit east at Harvard Road, has a brick retaining wall as well: https://goo.gl/maps/3TC5imWQiNZgNdL96  <-- this approach that I've linked is particularly bad. The brick "Welcome to Liberty Lake" sign is directly across from the approach from the westbound I-90 off-ramp. If drivers take this off-ramp, I shall hope they would continue paying enough attention to not hit the roundabout. But it sure would hurt if they did.
Title: Re: Crash prone 'modern roundabouts'
Post by: MNHighwayMan on October 15, 2019, 12:53:14 AM
Yep, let's go ahead and blame the roundabout again, and not the fact that the driver was intoxicated.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 15, 2019, 02:00:46 AM
Yep, let's go ahead and blame the roundabout again, and not the fact that the driver was intoxicated.

Imagine if retractable bollards were installed at signalized intersections that lift up when the light turns red to 'intercept' intoxicated drivers from blowing through the red light.  It might look something like this:



The retractable bollards would be a great safety feature as they would 'force' drivers to stop at the red light. If a bunch of intoxicated drivers are killed crashing into the retractable bollards, you can't blame that on the design.  After all, they shouldn't have run the red light.  But there you go blaming my new design.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 15, 2019, 02:10:23 AM
Yep, let's go ahead and blame the roundabout again, and not the fact that the driver was intoxicated.

Still dead thanks to intersection design, and nothing else. Plenty of people drive drunk all the time without killing themselves or others.

We might be able to sit here and say "well, it's good he killed himself before he killed someone else", but city officials have the duty to protect all citizens, both from each other and themselves, no matter their state of mind. It's why we have seatbelt laws and other shit like that. If you were driving drunk, god forbid, would you be glad that the city designed something that would almost certainly kill you? Last I checked, DUIs were not punishable by death.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on October 15, 2019, 07:10:23 AM
No, if he hadn't been drunk, he would have navigated the intersection safely.  The design is a minimal factor at best in his death.

I find driving drunk one of the most irresponsible activies one can engage in.  The idea that because some who drive drunk make it home in one piece means they are just as safe as any other driver is absurd.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on October 15, 2019, 08:27:43 AM
Yep, let's go ahead and blame the roundabout again, and not the fact that the driver was intoxicated.

Still dead thanks to intersection design, and nothing else. Plenty of people drive drunk all the time without killing themselves or others.

We might be able to sit here and say "well, it's good he killed himself before he killed someone else", but city officials have the duty to protect all citizens, both from each other and themselves, no matter their state of mind. It's why we have seatbelt laws and other shit like that. If you were driving drunk, god forbid, would you be glad that the city designed something that would almost certainly kill you? Last I checked, DUIs were not punishable by death.

Plenty of drunks crash into others at standard intersections.  Plenty of drunks navigate roundabouts without crashing into it.

Honestly, I'm surprised you're defending a drunk driver. A transportation department has a *reasonable* duty to protect drivers from deadly impacts. Which is in the form of speed limits, advisory speeds, etc. There are some things that are meant to protect, such as bollards in front of doors. On the other hand, we don't see guardrails at every telephone pole. Clearly if this guy managed to slam into this roundabout at such a high rate of speed to cause death, it probably saved an innocent life down the road.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 15, 2019, 09:58:49 AM
Yep, let's go ahead and blame the roundabout again, and not the fact that the driver was intoxicated.

Still dead thanks to intersection design, and nothing else. Plenty of people drive drunk all the time without killing themselves or others.

We might be able to sit here and say "well, it's good he killed himself before he killed someone else", but city officials have the duty to protect all citizens, both from each other and themselves, no matter their state of mind. It's why we have seatbelt laws and other shit like that. If you were driving drunk, god forbid, would you be glad that the city designed something that would almost certainly kill you? Last I checked, DUIs were not punishable by death.

Plenty of drunks crash into others at standard intersections.  Plenty of drunks navigate roundabouts without crashing into it.

Honestly, I'm surprised you're defending a drunk driver. A transportation department has a *reasonable* duty to protect drivers from deadly impacts. Which is in the form of speed limits, advisory speeds, etc. There are some things that are meant to protect, such as bollards in front of doors. On the other hand, we don't see guardrails at every telephone pole. Clearly if this guy managed to slam into this roundabout at such a high rate of speed to cause death, it probably saved an innocent life down the road.
Yet this is a count of a fatal accident for safety comparison of roundabout vs other designs.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on October 15, 2019, 10:14:41 AM
Yep, let's go ahead and blame the roundabout again, and not the fact that the driver was intoxicated.

Still dead thanks to intersection design, and nothing else. Plenty of people drive drunk all the time without killing themselves or others.

We might be able to sit here and say "well, it's good he killed himself before he killed someone else", but city officials have the duty to protect all citizens, both from each other and themselves, no matter their state of mind. It's why we have seatbelt laws and other shit like that. If you were driving drunk, god forbid, would you be glad that the city designed something that would almost certainly kill you? Last I checked, DUIs were not punishable by death.

Plenty of drunks crash into others at standard intersections.  Plenty of drunks navigate roundabouts without crashing into it.

Honestly, I'm surprised you're defending a drunk driver. A transportation department has a *reasonable* duty to protect drivers from deadly impacts. Which is in the form of speed limits, advisory speeds, etc. There are some things that are meant to protect, such as bollards in front of doors. On the other hand, we don't see guardrails at every telephone pole. Clearly if this guy managed to slam into this roundabout at such a high rate of speed to cause death, it probably saved an innocent life down the road.
Yet this is a count of a fatal accident for safety comparison of roundabout vs other designs.

Except I've yet to see a count of fatales at other intersection types in this discussion. There were approximately 10,800 fatal DUI crashes in 2018.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 15, 2019, 10:23:06 AM
Yep, let's go ahead and blame the roundabout again, and not the fact that the driver was intoxicated.

Still dead thanks to intersection design, and nothing else. Plenty of people drive drunk all the time without killing themselves or others.

We might be able to sit here and say "well, it's good he killed himself before he killed someone else", but city officials have the duty to protect all citizens, both from each other and themselves, no matter their state of mind. It's why we have seatbelt laws and other shit like that. If you were driving drunk, god forbid, would you be glad that the city designed something that would almost certainly kill you? Last I checked, DUIs were not punishable by death.

Plenty of drunks crash into others at standard intersections.  Plenty of drunks navigate roundabouts without crashing into it.

Honestly, I'm surprised you're defending a drunk driver. A transportation department has a *reasonable* duty to protect drivers from deadly impacts. Which is in the form of speed limits, advisory speeds, etc. There are some things that are meant to protect, such as bollards in front of doors. On the other hand, we don't see guardrails at every telephone pole. Clearly if this guy managed to slam into this roundabout at such a high rate of speed to cause death, it probably saved an innocent life down the road.
Yet this is a count of a fatal accident for safety comparison of roundabout vs other designs.

Except I've yet to see a count of fatales at other intersection types in this discussion. There were approximately 10,800 fatal DUI crashes in 2018.
ANY safety review of ANY intersection will consider a total number of crashes - fatal, injury, property-only - without separation into drunk/sober domain. Alcohol statistics is done only on a higher level, area-wise and not for specific locations.
Feel free to look up material on your state DOT site, you can usually find location-specific data published before major intersection reconstructions.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 15, 2019, 12:03:01 PM
Except I've yet to see a count of fatales at other intersection types in this discussion. There were approximately 10,800 fatal DUI crashes in 2018.

With so many drunk drivers on the road it should be assumed that a drunk is going to plow through the middle of a roundabout (specifically at rural and suburban roundabouts where approach speeds are higher).  The question is do we want that drunk driver to strike a 6 foot tall retaining wall (likely killing the driver & vehicle) or a 6 inch tall curb (likely killing just the vehicle).  In one scenario, the drunk driver is laying on a gurney and in the other they are sitting in the back of a cop car. 

When someone has a cavalier attitude when a drunk driver is killed at a roundabout, it gives them an excuse not to look at the overall roundabout design.  But these roundabout crashes aren’t limited to drunks.  News stories on this thread include an elderly couple in California plowing through the middle of a roundabout and a distracted teenager plowing through the middle of a roundabout while they were texting.  Maybe every time someone hears about a roundabout fatality, they should assume the driver was distracted and not drunk if it means they would consider the roundabout design and how it could be made safer.
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on October 15, 2019, 12:53:09 PM
Sure, the roundabout should have been designed differently, but undeniably, the driver was in the wrong for driving while intoxicated.
Those two are not mutually exclusive. It took both problems for this incident to occur.

However, imagine if someone had fainted or passed out while approaching the roundabout, with the same result. Then we would only be talking about the intersection design, and not the larger issue of whatever caused the person to be in the state they were in.
Long story short: both problems need to be addressed. But depending on the specifics of why the driver couldn't navigate properly, the intersection design could very well be the bigger problem at hand.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 15, 2019, 01:46:28 PM
Sure, the roundabout should have been designed differently, but undeniably, the driver was in the wrong for driving while intoxicated.
Those two are not mutually exclusive. It took both problems for this incident to occur.

However, imagine if someone had fainted or passed out while approaching the roundabout, with the same result. Then we would only be talking about the intersection design, and not the larger issue of whatever caused the person to be in the state they were in.
Long story short: both problems need to be addressed. But depending on the specifics of why the driver couldn't navigate properly, the intersection design could very well be the bigger problem at hand.
If you will, traffic control generally operates at amazing efficiency. accident count at regular intersection is something 1 crash in a million, no question about that.
Most of crashes are one-off events: drunk, tired, sleepy, lapse of attention, doing something stupid, mechanical failure...  And hence need to accommodate those, even if that looks excessive
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 15, 2019, 02:10:50 PM
For those who defend retaining walls in the central islands of roundabouts, I'm waiting for you to comment on my retractable bollard traffic signal design.  Any drunk driver who attempts to blow through a red light would be stopped "dead" in their tracks and be prevented from t-boning another vehicle within the intersection.  It would actually be more effective than a retaining wall in the central island of a roundabout as the bollards would protect both near-side and far-side vehicles from being t-boned (whereas the central island retaining wall would only protect far-side drivers at the roundabout).  My retractable bollard traffic signal design would be much safer than a conventional traffic signal, as the bollards would 'force' drivers to come to a stop at red lights!
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on October 15, 2019, 02:12:58 PM
Had the roundabout not been there, that driver could have t-boned a innocent car going across a standard intersection.

Im glad that roundabout was there to save innocent lives.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 15, 2019, 02:51:06 PM
For those who defend retaining walls in the central islands of roundabouts,

I don't think anyone is defending them.

Had the roundabout not been there, that driver could have t-boned a innocent car going across a standard intersection.

Im glad that roundabout was there to save innocent lives.

OK, scratch that...
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 15, 2019, 02:52:36 PM
Had the roundabout not been there, that driver could have t-boned a innocent car going across a standard intersection.

Im glad that roundabout was there to save innocent lives.
This is a good logic... at a first glance. Moral implication of such social Darwinism tend to become dire, though.
Just think that at some point you may become a target of such elimination process. For example, you get some infection - and instead of qualified medical help, you get euthanized to avoid infecting people around you.
Title: Re: Crash prone 'modern roundabouts'
Post by: sparker on October 15, 2019, 04:34:04 PM
Had the roundabout not been there, that driver could have t-boned a innocent car going across a standard intersection.

Im glad that roundabout was there to save innocent lives.
This is a good logic... at a first glance. Moral implication of such social Darwinism tend to become dire, though.
Just think that at some point you may become a target of such elimination process. For example, you get some infection - and instead of qualified medical help, you get euthanized to avoid infecting people around you.


Whole shitload of '70's films (mostly of the B or B+ grade variety) exploring (exploiting?) this concept (e.g. 1977's Cassandra Crossing).  Nothing like sending a whole trainload of probable infected persons off a trestle to the bottom of a canyon somewhere in Poland!
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 16, 2019, 11:33:04 AM
Had the roundabout not been there, that driver could have t-boned a innocent car going across a standard intersection.

Im glad that roundabout was there to save innocent lives.

The argument wasn’t whether the roundabout should be there or not but rather should retaining walls be included in the central islands of rural and suburban roundabouts.    A retaining wall does help protect innocent drivers who are circulating the roundabout on the far-side of the retaining wall from being struck when a driver blows straight through the middle of a roundabout.  The downside is any out of control driver who strikes the retaining wall in the central island at high speed is likely to die. 

The reality is fatal crashes at roundabouts involving 2 or more vehicles is rare despite the fact that there are thousands of roundabouts in this country without retaining walls in the central island to ”˜intercept’ out of control vehicles.  Of the 46 known fatal crashes at roundabouts that occurred from 2005 to 2013 reviewed by the FHWA, only 8 included multiple vehicles (and 5 of the 8 involved vulnerable road users riding motorcycles, bicycles, or golf carts).   https://safety.fhwa.dot.gov/intersection/innovative/roundabouts/docs/fhwasa15072.pdf  Here is one of the only news report I could find where an innocent driver who was correctly navigating through the roundabout was struck and killed by another vehicle.  In this case a retaining wall in the central island wouldn’t have saved the innocent driver, as the 'out of control' driver was driving the wrong way through the roundabout.
 
Wrong-way crash kills woman in Shiloh-Grand roundabout
https://billingsgazette.com/news/local/wrong-way-crash-kills-woman-in-shiloh-grand-roundabout/article_fce09623-e051-549d-af83-de7dfd4e28ad.html


Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 16, 2019, 12:13:09 PM
On April 2, 2006 during the morning daylight, a fatal crash occurred at the Douglas Ave/Sycamore St roundabout just outside of downtown Wichita when a driver struck the central island retaining wall.  The surrounding streets have low speed limits and there is on-street parking near by.  I'm not opposed to seeing this massive clock tower in the central island of this roundabout (if the city feels like this beautifies the area, go for it!).  This is an example of how you can't prevent all fatal crashes.  But this is a much different example than having a retaining wall at the Highways 12/113 roundabout in California that took the lives of an elderly couple a few weeks ago.

(https://i.imgur.com/HElCWUL.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 16, 2019, 02:16:45 PM
On April 2, 2006 during the morning daylight, a fatal crash occurred at the Douglas Ave/Sycamore St roundabout just outside of downtown Wichita when a driver struck the central island retaining wall.  The surrounding streets have low speed limits and there is on-street parking near by.  I'm not opposed to seeing this massive clock tower in the central island of this roundabout (if the city feels like this beautifies the area, go for it!).  This is an example of how you can't prevent all fatal crashes.  But this is a much different example than having a retaining wall at the Highways 12/113 roundabout in California that took the lives of an elderly couple a few weeks ago.

(https://i.imgur.com/HElCWUL.png)

That roundabout is my stomping grounds.  My church is one block away.  A person would have to be drunk to hit that central island.  Not only are the speed limits low, but the north-south street has very little traffic and practically nobody who isn't already familiar with the area, while the east-west street is a popular shopping/dining street with heavy foot traffic.  Furthermore, the giant clock tower and small diameter are huge cues to slow your speed way down, not to mention the fact that there's a pretty steady flow of traffic through the roundabout to watch out for too.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 25, 2019, 11:09:01 AM
Pretty insane video of a driver crashing and rolling their vehicle after flying over a roundabout in Dundee, Scottland:

Car flies over a roundabout and smashes to the ground before rolling three times in horror crash
https://www.dailymail.co.uk/news/article-7613113/Car-flies-roundabout-smashes-ground-rolling-three-times-horror-crash.html
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 25, 2019, 01:23:28 PM
Pretty insane video of a driver crashing and rolling their vehicle after flying over a roundabout in Dundee, Scottland:

Car flies over a roundabout and smashes to the ground before rolling three times in horror crash
https://www.dailymail.co.uk/news/article-7613113/Car-flies-roundabout-smashes-ground-rolling-three-times-horror-crash.html
Looking at the video and at the spot on google maps... Littered with 40 km/h speed limits and camera enforcement threats...
Are we sure this is an actual thing and not a stunt?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 04, 2019, 12:40:15 AM
Statues are being added to the WA-14 Washougal Roundabouts. Both are now open, and nearly complete.

This photo is from The Columbian newspaper:

(https://i.imgur.com/wNHzdBh.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 06, 2019, 07:30:43 AM
Quite an interesting roundabout design included as part of the new I-10 / Loop 1604 interchange in San Antonio, Texas:
(https://i.imgur.com/JvS9Mur.jpg)

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 07, 2019, 03:26:58 AM
I'm not usually one to get all riled up about path overlap. But, if I were, this proposed design would have me shaking in me boots!

OT: Only Texas would propose such a mind-boggling rebuild of a simple cloverleaf. Holy shit!
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on November 07, 2019, 10:14:08 AM
That seems like a case of too much money and finding new ways to spend it
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 19, 2019, 04:21:59 PM
The second most crash prone intersection in the region of Waterloo was the signalized intersection at Ottawa Street and Homer Watson.  It had 178 crashes over the past 5 years.  Well the city just finished converting the signalized intersection to a triple lane roundabout similar to the roundabout at Block Line Road.  The result has been 34 crashes in 29 days including 4 injury crashes.   A cyclist was struck by a minivan while she was cycling through the roundabout and is interviewed in the report below:

Ottawa/Homer Watson roundabout sees 34 collisions in 29 days
http://kitchener.ctvnews.ca/ottawa-homer-watson-roundabout-sees-34-collisions-in-29-days-1.3671232

The Region of Waterloo released its 2018 Collision Report and crash data is out for the Ottawa/Homer Watson roundabout.  There was 181 total crashes and 18 injury crashes at the triple-lane roundabout in 2018.  The five years before Ottawa/Homer Watson was converted to a roundabout, the traffic signal averaged just 35.6 total crashes and 10.4 injury crashes. 

2018 Collision Report (Region of Waterloo)
https://www.regionofwaterloo.ca/en/living-here/resources/Roads-and-Traffic/Collision-Reporting/2018-Annual-Collision-Report.pdf

An intersection having 18 crashes per year is significant... much less 18 injury crashes.  But for an intersection to experience 181 total crashes, there is something very wrong here.  This is the roundabout in question: https://www.google.com/maps?ll=43.42677,-80.48231&z=19&t=h
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 02, 2019, 04:23:42 PM
A list of problematic roundabouts in Carmel are highlighted in this Indy Star video.  It highlights the fact that the most crash prone intersection in Hamilton County in 2018 was the roundabout at 116th Street and Pennsylvania Street.  It also lists several intersections in Carmel that saw dramatic increases in crashes once they were converted to roundabouts. 

Have roundabouts made Carmel drivers safer? The data suggests 'no'
https://www.indystar.com/videos/news/local/hamilton-county/2019/12/01/have-roundabouts-made-carmel-drivers-safer-data-suggests-no/4300772002/
 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 03, 2019, 02:52:16 PM
A high number of property-damage crashes continue to plague Lakeville’s two-lane roundabout four years after its introduction
https://www.hometownsource.com/sun_thisweek/community/lakeville/at-lakeville-s-two-lane-roundabout-accidents-will-happen/article_ae025306-11f3-11ea-9c87-67acf8ebd5b3.html

-In 2014, the year before County Road 50 and County Road 60 was converted to a roundabout, the intersection experienced 10 crashes (none of them involving injury).

-A 2x2 roundabout was constructed in 2015.

-In 2018 there was 127 crashes including 4 injury crashes at the roundabout.  That equates to a crash rate of 8.65 MEV (or about 20x higher than the 0.44 crash rate they predicted when analyzing the roundabout design alternative back in 2011).

(https://i.imgur.com/irTe5ob.png)
https://www.co.dakota.mn.us/Transportation/TransportationStudies/Documents/CR50-CR60FullReport.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 06, 2019, 04:03:31 PM
Glastonbury roundabouts significantly reducing collisions after two years in operation
https://www.courant.com/community/glastonbury/hc-news-glastonbury-roundabouts-success-20191206-ydkwkd22gfgm7o6bznwfm2awlq-story.html

Two single-lane roundabouts were put in along Hebron Avenue a few years ago and now they are touting the crash reductions.  Averages crashes dropped from 5 to 3.5 and from 10 to 4.  It's great that these single-lane roundabouts are performing well, but now they will probably use these crash results to justify building some complex 3x2 roundabout next to a freeway thinking the same crash reductions will be seen.  But instead of 10 crashes dropping to 4, I'll be here to cite the fact that the complex roundabout went from 10 crashes before the roundabout to 127 after the roundabout (ie. County Road 50 and County Road 60 roundabout in Minnesota).  Let's hope city leaders don't get cocky just because their simple single-lane roundabouts are performing well. 
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on December 06, 2019, 06:15:03 PM
Success is not measured simply in crash rates.   Traffic throughput is an important factor.   In the age before roundabouts in Carmel there was terrible congestion during rush hours, now traffic flows smoothly during all but the most extreme congestion.   A few minor fender benders is a small price to pay for the improved traffic flow, better gas mileage and reduced travel times.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 06, 2019, 06:26:03 PM
Success is not measured simply in crash rates.   Traffic throughput is an important factor.   In the age before roundabouts in Carmel there was terrible congestion during rush hours, now traffic flows smoothly during all but the most extreme congestion.   A few minor fender benders is a small price to pay for the improved traffic flow, better gas mileage and reduced travel times.
Yep, especially when roundabouts are build with some extra lanes.
THroughput of roundabout is less than of traffic light
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 11, 2019, 02:03:51 PM
Success is not measured simply in crash rates.   Traffic throughput is an important factor.   In the age before roundabouts in Carmel there was terrible congestion during rush hours, now traffic flows smoothly during all but the most extreme congestion.

In the midst of Carmel’s roundabout blitz, two major routes in the city were converted from surface streets to grade separated freeways (Meridian St & Keystone Pkwy).  Also, several intersections in Carmel were nothing more than intersecting two-lane roads with no turn lanes before the roundabouts were built.   Roadways were widened and freeways were added in Carmel yet you only want to credit roundabouts for the improved traffic flow in the city.  Here are some before/after roundabout shots in Carmel:
(https://i.imgur.com/14wCyqy.jpg)

A few minor fender benders is a small price to pay for the improved traffic flow, better gas mileage and reduced travel times.

How do you know there are only a ”˜few’ minor fender benders at the Carmel roundabouts?  For years the Carmel Police Department would map out the top 20 crash intersections in the city in their annual report but that all changed in the 2014 report when the crash map was omitted.  By 2014 Carmel had complex 2x2 roundabouts and it was becoming increasingly apparent that many of these had crash problems.  Instead of being transparent and continuing to list these high crash roundabouts in their annual report, they decided to omit the high crash location map entirely.  Wouldn't surprise me if that directive came from the Mayor's office as Brainard is a total roundabout ideologue and wouldn't want to highlight data that is critical to roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 18, 2019, 05:41:51 PM
According to Delray Beach Fire Rescue, an elderly man trying to go around a roundabout lost control and plowed through a wall at Ebenezer Wesleyan Methodist Church, located at 201 SW 6th Avenue.

Driver loses control, crashes into Delray Beach church, officials say (https://www.wptv.com/news/region-s-palm-beach-county/delray-beach/driver-loses-control-crashes-into-delray-beach-church-officials-say)
(https://pbs.twimg.com/media/EMGKLEiXYAMAqve?format=jpg&name=360x360)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 18, 2019, 05:53:45 PM
More drama at The Villages roundabouts in Florida.  Patrick Henry O’Brien Jr. was knocked from his motorcycle after hitting the curb inside the Morse Boulevard at Deskin Lane roundabout.  He was transported to Ocala Regional Medical Center and is being treated in the ICU.

Motorcyclist lands in ICU after crash in roundabout in The Villages (https://www.villages-news.com/2019/12/12/motorcyclist-lands-in-icu-after-crash-in-roundabout-in-the-villages/)
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on December 18, 2019, 06:19:41 PM
Silly drivers.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 18, 2019, 07:59:48 PM
Silly drivers.
Silly drivers, idiotic engineers, stupid legislators, crazy world....
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on December 18, 2019, 10:14:27 PM
Why the US Hates Roundabouts (https://cheddar.com/media/why-the-u-s-hates-roundabouts)

Silly drivers.
Silly drivers, idiotic engineers poor design, stupid legislators, crazy world....

FIFY
Title: Re: Crash prone 'modern roundabouts'
Post by: ET21 on December 19, 2019, 08:36:38 AM
Why the US Hates Roundabouts (https://cheddar.com/media/why-the-u-s-hates-roundabouts)

Silly drivers.
Silly drivers, idiotic engineers poor design, stupid legislators, crazy world....

FIFY

Pretty much
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 19, 2019, 08:39:22 AM
Why the US Hates Roundabouts (https://cheddar.com/media/why-the-u-s-hates-roundabouts)

Silly drivers.
Silly drivers, idiotic engineers poor design, stupid legislators, crazy world....

FIFY

Pretty much
So you consider Chicago area highway network is well designed?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 19, 2019, 10:29:10 AM
They may not be idiotic engineers, maybe they are just insane.  The definition of insanity is doing the same thing over and over and expecting a different result.  When the Region of Waterloo found out that the Homer Watson and Block Line roundabout had experienced 435 crashes over a 5-year period (257 more crashes than the next closest intersection in the region) and that the roundabout was deemed the most dangerous intersection in the region with the highest average excess social cost of $271,780, what did they do?  They doubled down.  They built an even more complex roundabout just a mile up the road at Homer Watson and Ottawa Street.  Who in their right mind thought it was a good idea to build this thing?  It’s not like it couldn’t have been foreseen…

It's somewhat surprising they are going ahead with building a massive 3x2 roundabout at Ottawa Street & Homer Watson Blvd after all the issues with the Homer Watson Blvd & Block Road roundabout.  Based on your link, Ottawa Street & Homer Watson Blvd is the most crash prone intersection in the entire region.  Time will tell if the crash problem gets better or worse after the roundabout is completed. 

Well time has been told.  According to the Region of Waterloo annual crash reports, the Homer Watson and Ottawa Street intersection experienced 178 crashes in the 5 years before the roundabout was constructed (and it averaged 10.8 injury crashes/year).  In the first full year of operations, the roundabout has seen 181 crashes including 18 injury crashes.  So the roundabout is experiencing more crashes in one year that the previous signalized intersection experienced in 5 years.  Sounds insane to me, and you can’t really tout the safety of the roundabout when the average number of injury crashes has nearly doubled.  Again, insanity.  Hope the good people of Waterloo are enjoying their new roundabout, you got yourself a doozy.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 19, 2019, 10:35:31 AM
^Ottawa Street and Homer Watson was the most crash prone intersection in the entire region BEFORE the roundabout was constructed (aside from the Homer Watson & Block Line roundabout mentioned above with 435 total collisions over a 5 year period).  It's amazing that a roundabout being built can make the most crash prone intersection in the region 5X worse.
Title: Re: Crash prone 'modern roundabouts'
Post by: ET21 on December 19, 2019, 02:44:03 PM
Why the US Hates Roundabouts (https://cheddar.com/media/why-the-u-s-hates-roundabouts)

Silly drivers.
Silly drivers, idiotic engineers poor design, stupid legislators, crazy world....

FIFY

Pretty much
So you consider Chicago area highway network is well designed?

Not sure what that has to do with "Crash prone modern roundabouts"
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 19, 2019, 04:08:00 PM
Why the US Hates Roundabouts (https://cheddar.com/media/why-the-u-s-hates-roundabouts)

There is no acknowledgement of the failures of complex multi-lane roundabouts in this video.  The Region of Waterloo (population 500k) replaced the most crash prone signalized intersection with a roundabout and the result is crashes have quintupled... not doubled, not tripled, not quadrupled, but quintupled!  If you believe everything this video is saying then you ignore the failures that are taking place at these complex roundabouts.  Taking the most crash prone signalized intersection in your region and making it 5x more crash prone doesn't sound like a winning strategy.  Region of Waterloo is definitely not winning with this roundabout.   

(https://pbs.twimg.com/media/DNHF2ClWAAIzuzz.jpg:large)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 19, 2019, 05:49:40 PM
Why the US Hates Roundabouts (https://cheddar.com/media/why-the-u-s-hates-roundabouts)

Silly drivers.
Silly drivers, idiotic engineers poor design, stupid legislators, crazy world....

FIFY

Pretty much
So you consider Chicago area highway network is well designed?

Not sure what that has to do with "Crash prone modern roundabouts"
If you think engineering is good, it should be good across the board, not in a single tiny subset. Or, alternatively, if you're not happy with bigger picture what makes you think that an isolated problem type is being  solved properly?
Title: Re: Crash prone 'modern roundabouts'
Post by: ET21 on December 20, 2019, 08:40:06 AM
Why the US Hates Roundabouts (https://cheddar.com/media/why-the-u-s-hates-roundabouts)

Silly drivers.
Silly drivers, idiotic engineers poor design, stupid legislators, crazy world....

FIFY

Pretty much
So you consider Chicago area highway network is well designed?

Not sure what that has to do with "Crash prone modern roundabouts"
If you think engineering is good, it should be good across the board, not in a single tiny subset. Or, alternatively, if you're not happy with bigger picture what makes you think that an isolated problem type is being  solved properly?

You can skew the argument that way all you want, that's another whole topic on its own. The problem is how is that being communicated to the general public.

You can engineer it to be 100% but the public doesn't know any better on how it works. Signs and painted arrows can only do so much. We're seeing a lot of user error with these so maybe we need to start teaching people how to properly use these intersections.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on December 20, 2019, 08:55:36 AM
Why the US Hates Roundabouts (https://cheddar.com/media/why-the-u-s-hates-roundabouts)

Silly drivers.
Silly drivers, idiotic engineers poor design, stupid legislators, crazy world....

FIFY

Pretty much
So you consider Chicago area highway network is well designed?

Not sure what that has to do with "Crash prone modern roundabouts"
If you think engineering is good, it should be good across the board, not in a single tiny subset. Or, alternatively, if you're not happy with bigger picture what makes you think that an isolated problem type is being  solved properly?

Keep living in that dream world. Your "good" is someone else's "crap" and vise versa. If you expect everything to be absolute, you're setting yourself up for a lifetime of disappointment. Do you also have the same perspective on bridges, given the high-profile failures in the last few years?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 20, 2019, 12:11:24 PM
You can skew the argument that way all you want, that's another whole topic on its own. The problem is how is that being communicated to the general public.

You can engineer it to be 100% but the public doesn't know any better on how it works. Signs and painted arrows can only do so much. We're seeing a lot of user error with these so maybe we need to start teaching people how to properly use these intersections.
You stopped short of blaming public, which may save your day.
But anyway, a bit of harsh reminders:
Unlike college, real life doesn't give credit for the effort. No partial credit for good intentions. No extra point for beauty until core function is there.
Real life performance is a figure of merit; and if public (who is paying engineer's paycheck via taxes) is not good enough too achieve that - there is no way for engineer to get different public; but public can easily hire a different engineer.
Engineer who doesn't understand these things is an idiot. This is not an insult, this is a medical fact.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 20, 2019, 12:51:14 PM
You can engineer it to be 100% but the public doesn't know any better on how it works. Signs and painted arrows can only do so much. We're seeing a lot of user error with these so maybe we need to start teaching people how to properly use these intersections.

Short of mandating additional driver training every 5 or 10 years, there's not much that can be done to educate people beyond what's already out there.  You can't force people to look at websites and pamphlets.

When you have 40,000 people killed on the road each year, and roundabouts make up about a dozen of those deaths, there's a huge room for improvements on all types of roadways and intersections.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on December 20, 2019, 12:57:13 PM
But anyway, a bit of harsh reminders:
Unlike college, real life doesn't give credit for the effort. No partial credit for good intentions. No extra point for beauty until core function is there.
Real life performance is a figure of merit; and if public (who is paying engineer's paycheck via taxes) is not good enough too achieve that - there is no way for engineer to get different public; but public can easily hire a different engineer.

The flaw in your argument is how you define the "core function". By that metric, there are a lot of signalized intersections and for that matter, freeways that fail to meet your standards. It is impossible to engineer the risk out of everything. Thinking/expecting perfection at every turn is insanity.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 20, 2019, 01:15:50 PM
But anyway, a bit of harsh reminders:
Unlike college, real life doesn't give credit for the effort. No partial credit for good intentions. No extra point for beauty until core function is there.
Real life performance is a figure of merit; and if public (who is paying engineer's paycheck via taxes) is not good enough too achieve that - there is no way for engineer to get different public; but public can easily hire a different engineer.

The flaw in your argument is how you define the "core function". By that metric, there are a lot of signalized intersections and for that matter, freeways that fail to meet your standards. It is impossible to engineer the risk out of everything. Thinking/expecting perfection at every turn is insanity.
If you look at my writeup carefully, I never mentioned any safety parameter; I just massaged some butt for "stupid public" type comment.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 20, 2019, 01:17:15 PM
It is impossible to engineer the risk out of everything. Thinking/expecting perfection at every turn is insanity.

No way anyone expects perfection. But I would expect engineers to do at least a modicum of research on the crash rates at complex roundabouts. tradephoric's data is informal at best, but data is data. Places like Kitchener-Waterloo or Carmel should be well aware of the constant issues with their original complex roundabouts, but they continue to build more identical intersections. Expecting them to suddenly perform better than the old roundabouts is insane.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 20, 2019, 01:20:46 PM
You can engineer it to be 100% but the public doesn't know any better on how it works. Signs and painted arrows can only do so much. We're seeing a lot of user error with these so maybe we need to start teaching people how to properly use these intersections.

Short of mandating additional driver training every 5 or 10 years, there's not much that can be done to educate people beyond what's already out there.  You can't force people to look at websites and pamphlets.

When you have 40,000 people killed on the road each year, and roundabouts make up about a dozen of those deaths, there's a huge room for improvements on all types of roadways and intersections.
Even with extra training, excessive risk  is an unavoidable part of a  multilane roundabout concept. This is pretty obvious once you consider possible conflicts at roundabout entry; and those risks are actually well known and anticipated, as different localities ban RTOR from the second lane, not to mention third lane; or ban RTOR altogether. Conceptually those movements  are very similar to roundabout, if you think about it.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 23, 2019, 11:40:03 AM
It is impossible to engineer the risk out of everything. Thinking/expecting perfection at every turn is insanity.

The Region of Waterloo converted its most crash prone signalized intersection at Homer Watson and Ottawa Street to a roundabout.  The result has been a five-fold increase in crashes with 181 total crashes and 18 injury crashes.  It has been a complete failure at reducing accidents which was the main objective of building the roundabout to begin with.  I'd say that's the opposite of perfection.   
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 23, 2019, 12:00:37 PM
It is impossible to engineer the risk out of everything. Thinking/expecting perfection at every turn is insanity.

The Region of Waterloo converted its most crash prone signalized intersection at Homer Watson and Ottawa Street to a roundabout.  The result has been a five-fold increase in crashes with 181 total crashes and 18 injury crashes.  It has been a complete failure at reducing accidents which was the main objective of building the roundabout to begin with.  I'd say that's the opposite of perfection.   

I'd say that's taking a generalized statement and labeling it with something it wasn't intended to be labeled with.

You know, like every meme out there where people make up their own saying.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on December 23, 2019, 02:34:12 PM
It is impossible to engineer the risk out of everything. Thinking/expecting perfection at every turn is insanity.

The Region of Waterloo converted its most crash prone signalized intersection at Homer Watson and Ottawa Street to a roundabout.  The result has been a five-fold increase in crashes with 181 total crashes and 18 injury crashes.  It has been a complete failure at reducing accidents which was the main objective of building the roundabout to begin with.  I'd say that's the opposite of perfection.   

I'd say that's taking a generalized statement and labeling it with something it wasn't intended to be labeled with.

Without doing that, there'd be no point to this thread.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 23, 2019, 04:14:06 PM
I agree.  If engineers didn’t use generalized roundabout safety statistics as a rational for constructing complex roundabouts, there would be a lot less crash prone roundabouts to cite on this thread.  It’s great that roundabouts reduce total crashes by 38%, but that general statistic ignores the fact that there is a certain subset of roundabouts (complex roundabouts with 2x2 and 2x3 circulating lanes) that have unacceptably high crash rates.  Taking the most crash prone signalized intersection in a region of over 500k people and somehow, almost incredibly, making the crash problem 5 times worse is a failure.  Nowhere close to perfection.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 24, 2019, 12:03:19 AM
I don't really get the point of trying to shit on his data, or even his data collection methods.

It's almost certain that cities, counties, or states are going to great lengths to hide their actual roundabout crash data, because they know most of them don't perform well (or at least not to the touted levels prior to construction). Carmel seems to be a good example of this. The few roundabouts that actually have data, and are complex 2x1+ configurations, mostly seem to perform poorly. Yes, you can get an FOI request, but if these roundabouts are so damn good, why aren't municipalities going out of their way to mention as much? They build these things and then it's just radio silence (or until they announce a lane reduction or some other change to combat worsening conditions).

In terms of the "generalized statement", I've not yet seen a roundabout built where crash-reduction wasn't touted as a primary benefit.

I will give credit to anyone who can find a press-release about a new roundabout where improved safety wasn't mentioned.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on December 24, 2019, 12:52:29 AM
I don't really get the point of trying to shit on his data, or even his data collection methods.

No one is trying to "shit on his data" anymore. Many of us are just sick of the same old points being posted over and over and over again, mixed with selective quote wordplay to continue a point/agenda that was made tens of pages ago. We don't need a repeat news feed to announce every new crash; it's beating the same dead horse over and over again (kinda similar to someone's point about installing new multilane roundabouts and expecting crashes to vanish...pot meet kettle :hmmm: ).

I'd love to simply ignore this thread entirely, but I keep making the same mistake of coming back when there's a new post, in the [insane?] hopes there is going to be some new information that I could maybe use. But it looks like I am better-off sticking with my Google News feed and industry-supported sources. If I want crash reports, I'll just go straight to the source and cut out the snarky middleman.
Title: Re: Crash prone 'modern roundabouts'
Post by: US 89 on December 24, 2019, 01:07:29 AM
I will give credit to anyone who can find a press-release about a new roundabout any road project where improved safety wasn't mentioned.

FTFY
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on December 24, 2019, 01:14:21 AM
I don't really get the point of trying to shit on his data, or even his data collection methods.

It's almost certain that cities, counties, or states are going to great lengths to hide their actual roundabout crash data, because they know most of them don't perform well (or at least not to the touted levels prior to construction). Carmel seems to be a good example of this. The few roundabouts that actually have data, and are complex 2x1+ configurations, mostly seem to perform poorly. Yes, you can get an FOI request, but if these roundabouts are so damn good, why aren't municipalities going out of their way to mention as much? They build these things and then it's just radio silence (or until they announce a lane reduction or some other change to combat worsening conditions).

So now we're going to conspiracy theories? What actual (not hypothetical) evidence do you have to suggest agencies are "going to great lengths" to hide data? Many agencies (a few who have been reposted within this thread), publish annual crash reports. I have yet to see one of these reports with any roundabout-related crash information being redacted. The statement could also be reversed...if traffic signals are so damn good...

Why aren't they doing this? Because these same agencies don't have the manpower to waste on such an endeavor, and if they did, the public would start an outcry as to why their tax dollars are wasted on such things. Should the PD start putting out press releases as to why their Chevy squad cars are better than Dodge or Ford? Or is there a conspiracy with maintenance records and how much time the vehicles actually spend in the shop vs on the road?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 24, 2019, 02:47:41 AM
I will give credit to anyone who can find a press-release about a new roundabout any road project where improved safety wasn't mentioned.

FTFY

For sure. Safety really is the paramount issue facing transport agencies in the 21st century. But more to my point, there's no point in joking about trade's generalization about safety: every agency touts safety improvements as being a key part of road works.

I'd love to simply ignore this thread entirely, but I keep making the same mistake of coming back when there's a new post, in the [insane?] hopes there is going to be some new information that I could maybe use. But it looks like I am better-off sticking with my Google News feed and industry-supported sources. If I want crash reports, I'll just go straight to the source and cut out the snarky middleman.

Okay. So go to your sources and get some damn data. Instead, users keep coming back to this thread, telling trade to stop cherry-picking data, and then disappear again. Present some alternative data, have an actual discussion. You know, things engineers might do (although clearly don't do since they keep building these giant roundabouts, apparently thinking theirs will be different).

I don't really get the point of trying to shit on his data, or even his data collection methods.

It's almost certain that cities, counties, or states are going to great lengths to hide their actual roundabout crash data, because they know most of them don't perform well (or at least not to the touted levels prior to construction). Carmel seems to be a good example of this. The few roundabouts that actually have data, and are complex 2x1+ configurations, mostly seem to perform poorly. Yes, you can get an FOI request, but if these roundabouts are so damn good, why aren't municipalities going out of their way to mention as much? They build these things and then it's just radio silence (or until they announce a lane reduction or some other change to combat worsening conditions).

So now we're going to conspiracy theories? What actual (not hypothetical) evidence do you have to suggest agencies are "going to great lengths" to hide data? Many agencies (a few who have been reposted within this thread), publish annual crash reports. I have yet to see one of these reports with any roundabout-related crash information being redacted. The statement could also be reversed...if traffic signals are so damn good...

I don't have any; note my use of "almost certain" (i.e. not actually certain). I've based my assertion on how hard it has been for trade to find and organize data on these roundabouts.

Why aren't they doing this? Because these same agencies don't have the manpower to waste on such an endeavor, and if they did, the public would start an outcry as to why their tax dollars are wasted on such things. Should the PD start putting out press releases as to why their Chevy squad cars are better than Dodge or Ford? Or is there a conspiracy with maintenance records and how much time the vehicles actually spend in the shop vs on the road?

The "public would start an outcry" if their local municipalities took the time to analyze, organize, and publish crash data? That seems like a reach, unless your citizens were seriously hard-up. Personally, I think more people would start an outcry when they find out that their tax-funded ~$4M roundabouts (https://www.therecord.com/sports-story/2567746-twin-roundabouts-on-ottawa-st-s-face-public-critique/) have done nothing, except exchange slightly-worse traffic for an increase in collisions.
Title: Re: Crash prone 'modern roundabouts'
Post by: sparker on December 24, 2019, 05:04:19 AM
^^^^^^^^^^^
A main concern with all this is that roundabouts are just another example of what John Kingdon cited in his "garbage can" theory of general public policy -- a solution looking for a potential situation in which it can be applied.  Regardless of the data both before and after implementation, there's an institutional decision by the ranking jurisdiction (a DOT, city and/or county planners, etc.) concerning a decided preference for roundabouts.  The rash of deployment of such out here in CA by both Caltrans and local agencies seemingly at random points toward an adoption of a new "default" toward that configuration -- as the latest in a series of design "fads", placed in the field largely regardless of the specific situation.  A believer in conspiracies -- or deliberate coincidence -- might presume that there's a cross-agency goal to partially placate the naysayers of auto travel by placing these facilities where they create something of a disruption to continuous movement.  Personally, I do so hope that this isn't the case -- and that the agencies in question are continuing to engage in actual research and engineering rather than simple capitulation to some upper-level management whims!   :ded:
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 24, 2019, 06:11:49 AM
I think it's rare, if ever, when safety statistics are publicized long after any road project was completed.  I've seen numerous intersections get a traffic light, yet a year or two later there's no mention of crash data for those intersections either.  It's not like they're intentionally hiding data on roundabouts. 

And to that point - if there's 2 intersection improvements nearby; one getting a roundabout, one getting a traffic light, it would be hiding data if they only presented data on the traffic light intersection later on.  Unfortunately in this thread - and this is where the cherry-picking of data comes in - news only regarding the roundabout would be presented.  If there was 1 more crash at the roundabout, and 10 more crashes at the traffic light intersection, you can bet we'd only hear about the 1 at a roundabout.  Since we don't have a thread about Crash prone 'modern intersections', we are left to just get news on the roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 24, 2019, 08:39:55 AM
I don't really get the point of trying to shit on his data, or even his data collection methods.

It's almost certain that cities, counties, or states are going to great lengths to hide their actual roundabout crash data, because they know most of them don't perform well (or at least not to the touted levels prior to construction). Carmel seems to be a good example of this. The few roundabouts that actually have data, and are complex 2x1+ configurations, mostly seem to perform poorly. Yes, you can get an FOI request, but if these roundabouts are so damn good, why aren't municipalities going out of their way to mention as much? They build these things and then it's just radio silence (or until they announce a lane reduction or some other change to combat worsening conditions).

So now we're going to conspiracy theories? What actual (not hypothetical) evidence do you have to suggest agencies are "going to great lengths" to hide data? Many agencies (a few who have been reposted within this thread), publish annual crash reports. I have yet to see one of these reports with any roundabout-related crash information being redacted. The statement could also be reversed...if traffic signals are so damn good...

Why aren't they doing this? Because these same agencies don't have the manpower to waste on such an endeavor, and if they did, the public would start an outcry as to why their tax dollars are wasted on such things. Should the PD start putting out press releases as to why their Chevy squad cars are better than Dodge or Ford? Or is there a conspiracy with maintenance records and how much time the vehicles actually spend in the shop vs on the road?

And this is how engineering idiocy proliferate.
Post-mortem, lessons learned, project feedback - those are essential components of most professions; and a must for those where decisions are required.
Maybe no publishing - but an internal analysis is an absolute must.
Instead we have
What would be the criteria used to declare this project a success?
From an engineering perspective, no unusual circumstances proffer themselves (large cracks, misaligned joints, etc.) and everything is built to plan. From a public policy perspective, it comes in within budget and on time (and I believe it's actually a little early).

Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on December 24, 2019, 10:54:17 AM
we don't have a thread about Crash prone 'modern intersections'

Indeed, it is a thread we'll never see on AARoads (https://www.aaroads.com/forum/index.php?topic=10705.msg2183126#msg2183126).
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on December 24, 2019, 12:13:25 PM
It's almost certain that cities, counties, or states are going to great lengths to hide their actual roundabout crash data, because they know most of them don't perform well (or at least not to the touted levels prior to construction). Carmel seems to be a good example of this. The few roundabouts that actually have data, and are complex 2x1+ configurations, mostly seem to perform poorly. Yes, you can get an FOI request, but if these roundabouts are so damn good, why aren't municipalities going out of their way to mention as much? They build these things and then it's just radio silence (or until they announce a lane reduction or some other change to combat worsening conditions).
So now we're going to conspiracy theories? What actual (not hypothetical) evidence do you have to suggest agencies are "going to great lengths" to hide data? Many agencies (a few who have been reposted within this thread), publish annual crash reports. I have yet to see one of these reports with any roundabout-related crash information being redacted. The statement could also be reversed...if traffic signals are so damn good...
I don't have any; note my use of "almost certain" (i.e. not actually certain). I've based my assertion on how hard it has been for trade to find and organize data on these roundabouts.

Almost certain, actually certain, spin it how you wish. Semantics doesn't change the base of your comment. "How hard"...how many agencies has he actually tried contacting? From what has been posted here, it's only been information readily available online. Just because you can't find it from an online search doesn't mean they're trying to hide anything.

Why aren't they doing this? Because these same agencies don't have the manpower to waste on such an endeavor, and if they did, the public would start an outcry as to why their tax dollars are wasted on such things. Should the PD start putting out press releases as to why their Chevy squad cars are better than Dodge or Ford? Or is there a conspiracy with maintenance records and how much time the vehicles actually spend in the shop vs on the road?
The "public would start an outcry" if their local municipalities took the time to analyze, organize, and publish crash data? That seems like a reach, unless your citizens were seriously hard-up. Personally, I think more people would start an outcry when they find out that their tax-funded ~$4M roundabouts (https://www.therecord.com/sports-story/2567746-twin-roundabouts-on-ottawa-st-s-face-public-critique/) have done nothing, except exchange slightly-worse traffic for an increase in collisions.

That's not what I was referring to.
Yes, you can get an FOI request, but if these roundabouts are so damn good, why aren't municipalities going out of their way to mention as much? They build these things and then it's just radio silence (or until they announce a lane reduction or some other change to combat worsening conditions).

You were suggesting a post-construction PR campaign on how good the intersection is performing, basically advertising "how great" they are. THAT's what would generate an outcry. Again, not every agency has the staffing availability to run the numbers following each and every project they complete. Most of the general public doesn't care that deeply. If you pay attention to locations where roundabouts have been present for a number of years, the comments have changed to focus on the bad driving habits and not the roundabout itself.

The larger agencies are looking at the numbers and trying to figure out what went wrong. But in most cases, since the serious injury crashes are down and traffic is generally flowing better than before, they're going to move on to one of their many other fires they have to put out. Unfortunately, real-world engineering becomes a balancing act - there are always going to be trade-offs and compromises.

I'd love to simply ignore this thread entirely, but I keep making the same mistake of coming back when there's a new post, in the [insane?] hopes there is going to be some new information that I could maybe use. But it looks like I am better-off sticking with my Google News feed and industry-supported sources. If I want crash reports, I'll just go straight to the source and cut out the snarky middleman.
Okay. So go to your sources and get some damn data. Instead, users keep coming back to this thread, telling trade to stop cherry-picking data, and then disappear again. Present some alternative data, have an actual discussion. You know, things engineers might do (although clearly don't do since they keep building these giant roundabouts, apparently thinking theirs will be different).

Yes, sir, right away sir.  :rolleyes:  I'm really eager to serve those who keep insulting my profession, and painting all of us with the same broad brush.
My sources are barely any different than what any of you have. If someone is so hell-bent on disproving roundabouts, they have the time to research balanced information. Do your own damn digging.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on December 24, 2019, 12:26:29 PM
I don't really get the point of trying to shit on his data, or even his data collection methods.

It's almost certain that cities, counties, or states are going to great lengths to hide their actual roundabout crash data, because they know most of them don't perform well (or at least not to the touted levels prior to construction). Carmel seems to be a good example of this. The few roundabouts that actually have data, and are complex 2x1+ configurations, mostly seem to perform poorly. Yes, you can get an FOI request, but if these roundabouts are so damn good, why aren't municipalities going out of their way to mention as much? They build these things and then it's just radio silence (or until they announce a lane reduction or some other change to combat worsening conditions).

So now we're going to conspiracy theories? What actual (not hypothetical) evidence do you have to suggest agencies are "going to great lengths" to hide data? Many agencies (a few who have been reposted within this thread), publish annual crash reports. I have yet to see one of these reports with any roundabout-related crash information being redacted. The statement could also be reversed...if traffic signals are so damn good...

Why aren't they doing this? Because these same agencies don't have the manpower to waste on such an endeavor, and if they did, the public would start an outcry as to why their tax dollars are wasted on such things. Should the PD start putting out press releases as to why their Chevy squad cars are better than Dodge or Ford? Or is there a conspiracy with maintenance records and how much time the vehicles actually spend in the shop vs on the road?

And this is how engineering idiocy proliferate.
Post-mortem, lessons learned, project feedback - those are essential components of most professions; and a must for those where decisions are required.
Maybe no publishing - but an internal analysis is an absolute must.
Instead we have
What would be the criteria used to declare this project a success?
From an engineering perspective, no unusual circumstances proffer themselves (large cracks, misaligned joints, etc.) and everything is built to plan. From a public policy perspective, it comes in within budget and on time (and I believe it's actually a little early).

While I can't speak for every agency, I can say that this kind of postmortem analysis IS going on at a few I work with. Just because they don't make headlines, doesn't mean the work is not being done. Much of this work is then getting presented and/or published at TRB. Change doesn't happen overnight, especially when government agencies are involved.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on December 24, 2019, 01:29:27 PM
There's silence whether they improve safety or do not.  It's not some conspiracy.  Most transportation projects don't make the news much at all.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 24, 2019, 03:22:43 PM
You were suggesting a post-construction PR campaign on how good the intersection is performing, basically advertising "how great" they are. THAT's what would generate an outcry. Again, not every agency has the staffing availability to run the numbers following each and every project they complete. Most of the general public doesn't care that deeply.

"Going out of their way" was a poor choice of words on my part. I was thinking more along the lines of a press release talking about safety improvements. Along the lines of "20% reduction in injuries in the two years after construction as compared to before", or "crashes halved at busy county intersection after new roundabout". WSDOT already did this when they removed two traffic lights along an expressway: "Highway 500 reconfiguration passes 6-month crash test (https://www.columbian.com/news/2019/aug/08/highway-500-reconfiguration-passes-6-month-crash-test/)." They could do this for roundabouts too, no? If they want to build more, they could at least confirm that they work. That's not unreasonable.

The reason I consider things like this important, is because agencies do go on PR campaigns about the benefits of roundabouts. What major DOT doesn't have some webpage dedicated entirely to roundabouts and their benefits? Here is WashDOT's page on the matter (https://www.wsdot.wa.gov/Safety/roundabouts/benefits.htm), with titles such as "Improve safety", "Reduction in collisions", and "Reduce delay, improve traffic flow". As with other agencies, they continue to cite that nearly-20-year-old study from the IIHS, and literally nothing else. Then, there's the numerous videos online about how to drive roundabouts, why they are built, where they came from; again, after they are built, it's just complete silence.

Even more interesting, on WashDOT's page for "Safety" (https://www.wsdot.wa.gov/Safety/default.htm), they have sub-pages about cable barriers, rest areas, and...yep, roundabouts. Click on "roundabout", and there are six separate pages on what they are, their benefits, navigation, etc. You're gonna tell me that taxpayers are perfectly fine with agencies creating dedicated webpages, graphics, and PR campaigns specifically for these intersections, but they'll lose it if they announce post-construction safety improvements? Come on. I think both are perfectly reasonable.

If you pay attention to locations where roundabouts have been present for a number of years, the comments have changed to focus on the bad driving habits and not the roundabout itself.

That's not a good thing, though. How many signals or stop signs have similar levels of comments? Sure, people bitch and moan about red-light running, or failing to yield, but people don't go on and on about how "no one but them knows how to use one".
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on December 24, 2019, 06:22:51 PM
You were suggesting a post-construction PR campaign on how good the intersection is performing, basically advertising "how great" they are. THAT's what would generate an outcry. Again, not every agency has the staffing availability to run the numbers following each and every project they complete. Most of the general public doesn't care that deeply.

"Going out of their way" was a poor choice of words on my part. I was thinking more along the lines of a press release talking about safety improvements. Along the lines of "20% reduction in injuries in the two years after construction as compared to before", or "crashes halved at busy county intersection after new roundabout". WSDOT already did this when they removed two traffic lights along an expressway: "Highway 500 reconfiguration passes 6-month crash test (https://www.columbian.com/news/2019/aug/08/highway-500-reconfiguration-passes-6-month-crash-test/)." They could do this for roundabouts too, no? If they want to build more, they could at least confirm that they work. That's not unreasonable.

No, it's not unreasonable, but our PR people get crucified with any instructional mailing or other campaign that comes out, whether it be for roundabouts, diverging diamonds, the FYA, or a reduction in road salt use. Generally, if you stop hearing complaints, you accept the "victory"; you don't go poking the bear with an "I told you so" campaign. No news is good news.

How many signals or stop signs have similar levels of comments? Sure, people bitch and moan about red-light running, or failing to yield

Isn't that a little contradictory?

That's not a good thing, though. How many signals or stop signs have similar levels of comments? Sure, people bitch and moan about red-light running, or failing to yield, but people don't go on and on about how "no one but them knows how to use one".

It happens every time someone gets t-boned at a red light or stop sign, DUI or otherwise. The other week there was an editorial in our local paper asking the DOT to install FYAs at an intersection because no one seemingly knows what a green ball means. It happens more than you may think.
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on December 25, 2019, 01:49:58 AM
Questions for discussion: what makes multi-lane roundabouts broadly acceptable in the United Kingdom but not in the United States? Is the crash data substantially the same between the two countries? If not, why not?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 25, 2019, 07:21:48 AM
Questions for discussion: what makes multi-lane roundabouts broadly acceptable in the United Kingdom but not in the United States? Is the crash data substantially the same between the two countries? If not, why not?
Good question. As much as I hate to say that — engineers' level of understanding.  A few miles upthread we pressed @cl94 into confession that there is no interest (hence funding) from FHWA for roundabout-related research. If you look at the publications, most of related research happens in Irel.and and France.    While there is no very direct relation between academic research and showels in the ground, problem  understanding tends to go around.
My impression is that US engineers don't understand limitations of roundabouts in terms of traffic throughput, scalability, limitations. FHWA guildelines for road diet, for example, seem to have much better understanding of situation.
Squeezing roundabouts to the bare minimum size is another problematic trend. Being only fourth largest country in the world, US really needs smallest possible footprints
Yes, sir, right away sir.  :rolleyes:  I'm really eager to serve those who keep insulting my profession, and painting all of us with the same broad brush.
It could be worse... Some people critisize engineers for a living! For example, one of my most pressing pre-xmas deadlines was posting grades for two ENGXXX courses. I am not your dream Santa with 3 F's passed around. My only excuse — I didn't enjoy that at all.
While I can't speak for every agency, I can say that this kind of postmortem analysis IS going on at a few I work with. Just because they don't make headlines, doesn't mean the work is not being done. Much of this work is then getting presented and/or published at TRB. Change doesn't happen overnight, especially when government agencies are involved.
At least we're on the same page with seing the value in such analysis.
I am not fully with @jakeroot in expecting a lot of post-construction PR to go around (although no PR department is going to pass on opportunity to send out “a paper analysing recent projects was publishest by StateDOT engineers” , even without going into headlines?). And  from the general perspective, most of pre-construction PR quotes ancient papers — if the data about previous project existed, you think DOT would pass on the opportunity to include “a similar project 2 miles down the road resulted in 3x drop of accident rate” in public comment presentation?
Something I still need to see.

And while we're at this.... Merry Christmas, ladies and gentlemen!
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 25, 2019, 09:06:44 AM
"Going out of their way" was a poor choice of words on my part. I was thinking more along the lines of a press release talking about safety improvements. Along the lines of "20% reduction in injuries in the two years after construction as compared to before", or "crashes halved at busy county intersection after new roundabout". WSDOT already did this when they removed two traffic lights along an expressway: "Highway 500 reconfiguration passes 6-month crash test (https://www.columbian.com/news/2019/aug/08/highway-500-reconfiguration-passes-6-month-crash-test/)." They could do this for roundabouts too, no? If they want to build more, they could at least confirm that they work. That's not unreasonable.

This is where the nitpicking comes to play.  The news report you found was for a very specific, relatively unusual project.   But then you used this one example to claim they should be doing this for roundabouts.  Why not for traffic lights?  Or Interchanges?  Or widenings?  Or smoothing out a dangerous curve?  Or for an addition of chevron arrows?  Or for different paint for lines?  Or for reflectors?  Or for different asphalts?  Or for LED lighting?

This shows that most projects don't get full analysis afterwards. But finding one that does doesn't mean it's justified on every project, and especially towards one specific type of project.

Questions for discussion: what makes multi-lane roundabouts broadly acceptable in the United Kingdom but not in the United States? Is the crash data substantially the same between the two countries? If not, why not?

I tried doing searching for "roundabout crash analysis in France", "roundabout crash analysis in Paris France" and the same replacing "analysis" with "data" (and a few other similar searches).  Very few relevant results appear, and of the few, the analysis just talks mostly about the data collection rather than the results.  One search led me to roundabouts in Korea, but again, no real conclusion about their safety was mentioned.

So, the reasoning we have in the US may be a fallacy - we simply don't hear viewpoints of other countries, and the crash data and results in other countries.  We think of the US as not accepting of roundabouts because we are specifically looking for articles and viewpoints where people complain about them, and searches where we want to see Europe and other areas as favorable to them because they've had them.  But there's no definite conclusion I can quickly find that states they're safer in Europe, or people actually accept them and favor them in Europe (or elsewhere).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 25, 2019, 09:52:08 AM
Questions for discussion: what makes multi-lane roundabouts broadly acceptable in the United Kingdom but not in the United States? Is the crash data substantially the same between the two countries? If not, why not?

I tried doing searching for "roundabout crash analysis in France", "roundabout crash analysis in Paris France" and the same replacing "analysis" with "data" (and a few other similar searches).  Very few relevant results appear, and of the few, the analysis just talks mostly about the data collection rather than the results.  One search led me to roundabouts in Korea, but again, no real conclusion about their safety was mentioned.
You need to know where to look for.
https://link.springer.com/book/10.1007/978-3-642-84537-6#toc - is there anything remotely comparable for US? Published in 1991, mind it..
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 26, 2019, 02:28:56 PM
The larger agencies are looking at the numbers and trying to figure out what went wrong. But in most cases, since the serious injury crashes are down and traffic is generally flowing better than before, they're going to move on to one of their many other fires they have to put out. Unfortunately, real-world engineering becomes a balancing act - there are always going to be trade-offs and compromises.

Agencies aren't just moving on when they see a big spike in crashes at these complex roundabouts.  The reality is many of these 3x2 complex roundabouts have been downsized to 2x2 or even 2x1 roundabouts (Superior Street & 14th St roundabout in Lincoln).  Drastically reducing the capacity of the roundabout just years after it was built doesn’t sound like nothing.    The roundabouts that haven’t been downsized end up near the top of crash prone intersection lists (last year 3 of the top 5 most crash prone intersections in Michigan were at 3x2 roundabouts) and agencies are left defending what is almost indefensibly high crash rates.
   
It’s true, serious injury crashes and fatalities are down at the complex roundabouts analyzed in the Minnesota study, but total injury crashes rose by 6%.  Not to mention there was a 212% increase in PDO crashes.  Doing a before/after crash cost analysis, the social impacts of the roundabouts are worse than the intersections they replaced.  Similar case if you look at the social impacts of the complex roundabouts in the Region of Waterloo in the 2018 crash report that was just released.  You seem to be underestimating the impacts these problematic complex roundabouts are having.  Look at this chart of crash rates that was included in the Minnesota study.  Full dual roundabouts far and away have worse crash rates than other traffic control devices in Minnesota.

(https://i.imgur.com/HCungIJ.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 26, 2019, 03:38:39 PM
Questions for discussion: what makes multi-lane roundabouts broadly acceptable in the United Kingdom but not in the United States? Is the crash data substantially the same between the two countries? If not, why not?

I tried doing searching for "roundabout crash analysis in France", "roundabout crash analysis in Paris France" and the same replacing "analysis" with "data" (and a few other similar searches).  Very few relevant results appear, and of the few, the analysis just talks mostly about the data collection rather than the results.  One search led me to roundabouts in Korea, but again, no real conclusion about their safety was mentioned.
You need to know where to look for.
https://link.springer.com/book/10.1007/978-3-642-84537-6#toc - is there anything remotely comparable for US? Published in 1991, mind it..


Yeah, I didn't see that in my searching.  But even then, most results appear to be studies and predications. Other than the first result, we're still not giving an analysis of how they function. And even then, we would need to pay for the reports listed.  So after everything that has been claimed regarding how the US doesn't analyze recently built rounds, it's becoming clearer that nearly no other country, on a regular basis, analyzes them either!
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 26, 2019, 04:08:34 PM
A year after the 161-Riverside roundabout was modified to reduce a circulating lane of traffic, crashes have dropped from 2.5/week to 2/week.  That's still over 100 crashes a year and much higher than the 15 annual crashes the intersection averaged before the roundabout.  After modifications to the roundabout, injury accidents dropped from 37 to 15 per year.  That's a significant drop, but the pre-roundabout intersection only averaged 15 crashes total.  Of course the article makes no mention of the pre-roundabout crash rates, but here (http://dublinohiousa.gov/dev/dev/wp-content/uploads/2014/02/SR-161-Riverside-Drive-Intersection-Summary.pdf) is the link to that.  Back in 2014 the city was citing a crash rate of 0.98 at the intersection to justify the construction of the roundabout.  Now even with the "modified" roundabout, the crash rate is 5.7. 

Dublin officials say 161-Riverside roundabout fixes lessen crashes
https://www.thisweeknews.com/news/20191022/dublin-officials-say-161-riverside-roundabout-fixes-lessen-crashes
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 26, 2019, 04:48:55 PM
Questions for discussion: what makes multi-lane roundabouts broadly acceptable in the United Kingdom but not in the United States? Is the crash data substantially the same between the two countries? If not, why not?

I tried doing searching for "roundabout crash analysis in France", "roundabout crash analysis in Paris France" and the same replacing "analysis" with "data" (and a few other similar searches).  Very few relevant results appear, and of the few, the analysis just talks mostly about the data collection rather than the results.  One search led me to roundabouts in Korea, but again, no real conclusion about their safety was mentioned.
You need to know where to look for.
https://link.springer.com/book/10.1007/978-3-642-84537-6#toc - is there anything remotely comparable for US? Published in 1991, mind it..


Yeah, I didn't see that in my searching.  But even then, most results appear to be studies and predications. Other than the first result, we're still not giving an analysis of how they function. And even then, we would need to pay for the reports listed.  So after everything that has been claimed regarding how the US doesn't analyze recently built rounds, it's becoming clearer that nearly no other country, on a regular basis, analyzes them either!
Pay... this is academic research; unfortunately a lot of publications are not free; fortunately many universities have access (including access from university library by general public); even more fortunately there are other ways.... Bottom line - PM if you want to read those :)

As for analysis - a pretty broad one from UK:  https://journals.sagepub.com/doi/abs/10.3141/2585-02
And people are looking beyond today's needs: https://ieeexplore.ieee.org/abstract/document/7504449/authors#authors
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 31, 2019, 06:16:11 PM
A injury accident involving three-vehicles at the Morse Blvd and Stillwater Trail roundabout occurred in the Villages on Friday.  This comes a few weeks after a serious injury accident at a Village roundabout that left a motorcyclist in the ICU:

Driver taken by ambulance from three-vehicle crash in roundabout in The Villages (https://www.villages-news.com/2019/12/27/driver-taken-by-ambulance-from-three-vehicle-crash-in-roundabout-in-the-villages/)
(https://www.villages-news.com/wp-content/uploads/2019/12/The-driver-of-a-mini-van-was-transported-from-the-scene-of-the-crash-in-the-roundabout-near-the-gate-at-the-Village-of-Caroline--600x450.jpg)

Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on December 31, 2019, 09:06:08 PM
A injury accident involving three-vehicles at the Morse Blvd and Stillwater Trail roundabout occurred in the Villages on Friday.  This comes a few weeks after a serious injury accident at a Village roundabout that left a motorcyclist in the ICU:

Driver taken by ambulance from three-vehicle crash in roundabout in The Villages (https://www.villages-news.com/2019/12/27/driver-taken-by-ambulance-from-three-vehicle-crash-in-roundabout-in-the-villages/)
~IMAGE CENSORED~

Posting the link wasn't enough? What purpose did spreading a photo of someone being wheeled away on a stretcher add to this? It's bad enough that the newspaper published it.

Further, it was a rear-end chain-reaction crash...one that could have happened just as easily at any other intersection type:
Quote from: from article
The driver of a maroon minivan at about 10:30 a.m. Friday had been northbound on Morse Boulevard at the roundabout at Stillwater Trail when it crashed into the back of a RoMac Building Supply Co. window installation truck hauling glass, according to the Sumter County Sheriff’s Office. The RoMac truck was pushed into the rear of another vehicle.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 01, 2020, 05:06:50 AM
A injury accident involving three-vehicles at the Morse Blvd and Stillwater Trail roundabout occurred in the Villages on Friday.  This comes a few weeks after a serious injury accident at a Village roundabout that left a motorcyclist in the ICU:

Driver taken by ambulance from three-vehicle crash in roundabout in The Villages (https://www.villages-news.com/2019/12/27/driver-taken-by-ambulance-from-three-vehicle-crash-in-roundabout-in-the-villages/)
~IMAGE CENSORED~

Posting the link wasn't enough? What purpose did spreading a photo of someone being wheeled away on a stretcher add to this? It's bad enough that the newspaper published it.

Further, it was a rear-end chain-reaction crash...one that could have happened just as easily at any other intersection type:
Quote from: from article
The driver of a maroon minivan at about 10:30 a.m. Friday had been northbound on Morse Boulevard at the roundabout at Stillwater Trail when it crashed into the back of a RoMac Building Supply Co. window installation truck hauling glass, according to the Sumter County Sheriff’s Office. The RoMac truck was pushed into the rear of another vehicle.
But it did happen at roundabout, contributing to roundabout crash rate.
While I agree posting individual crash reports is meaningless, message of roundabouts safety underperforming by a huge margin is clear
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 03, 2020, 12:09:28 PM
Every year the roundabouts in Augusta, Maine are the most crash prone intersections in the state.  You can literally query out any year in Maine's crash database going back to 2003 and the Cony Circle and Memorial Circle will top the list (MaineDOT's crash database is cited in the article).  Also if you look at pre-2010, the Cony Circle had an insanely high number of injury crashes (highest average in the state each and every year).  The circle was reconfigured in 2008 (to conform to more modern roundabout standards) and the number of injury accidents have dropped but still higher than you would like to see at a roundabout.

8 Investigates Maine's high-crash locations for 2019
https://www.wmtw.com/article/8-investigates-maines-high-crash-locations-for-2019/30379657

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 03, 2020, 03:01:32 PM
^I won't post a picture of any of the many injury crashes that have occurred in the Cony circle so not to be censored.  Posting a picture involving an injury accident is outrageous apparently.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 03, 2020, 03:04:33 PM
And here's how to properly navigate the Cony Circle.  Simple right?
(https://i.imgur.com/11mN2wg.gif?1)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 03, 2020, 03:21:12 PM
Yes, it should be straightforward.  And yet, by my count, there are a total of nine conflict points that are not merely glancing blows:

(https://i.imgur.com/HHNQZjK.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 03, 2020, 03:33:55 PM
I've been through those Augusta roundabouts before (way back in 2011); Cony Circle is impressive to me, even if it's #2 most crash-prone in the state. It's really hard to configure a five-way intersection, so credit where credit's due to Augusta's engineers of yore.

On the other hand, Memorial Circle is arguably simpler, yet features more crashes (at least for 2019). That's not good for a regular four-leg roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on January 03, 2020, 04:01:31 PM
^I won't post a picture of any of the many injury crashes that have occurred in the Cony circle so not to be censored.  Posting a picture involving an injury accident is outrageous apparently.

Get over yourself. Apparently you're new to social media. News outlets (at least around here) get crucified when they post that kind of picture on social media. You never know who may not know about their loved one being involved in an accident. Finding out via social media is not usually a way loved ones prefer to find out. Your decision to continue one newspaper's bad decision doesn't make it any better.

What's arguably more troubling, your sharing of it had zero to do with furthering the cause of this topic other than over-sensationalizing the situation. It provides zero context to any possible cause of the crash or what role the roundabout may or may not have played. There were two other photos you could have posted, but you chose the one to spin the crash as bad as it possibly could be. It's one thing if the photo would have been included with the attachment on its own, but you had to do extra work and knowingly post the extra photo. You could have just left it with a link to the article.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 03, 2020, 05:07:18 PM
Yes, it should be straightforward.  And yet, by my count, there are a total of nine conflict points that are not merely glancing blows:

(https://i.imgur.com/HHNQZjK.png)
Which is the least relevant number for analysis.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 03, 2020, 05:13:30 PM
Those conflict points are what I think drive the hidden danger of multi-lane roundabouts.  In the literature, you can better your sweet bippy you'll always find an illustration touting the reduced number of conflict points a roundabout has, and also an explanation of how all the conflict points that remain are merely glancing blows unlikely to result in serious damage or injury/death.  Then that's used to help justify building a mutli-lane roundabout that has more conflict points than illustrated and also does indeed have non-glancing conflict points.

Yield-only approaches are fine and dandy when all trajectories gradually sweep into and out of each other.  But, when half the trajectories actually cross each other, mere yield signs are insufficient to prevent accidents.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 03, 2020, 05:17:00 PM
^I won't post a picture of any of the many injury crashes that have occurred in the Cony circle so not to be censored.  Posting a picture involving an injury accident is outrageous apparently.

Get over yourself. Apparently you're new to social media. News outlets (at least around here) get crucified when they post that kind of picture on social media. You never know who may not know about their loved one being involved in an accident. Finding out via social media is not usually a way loved ones prefer to find out. Your decision to continue one newspaper's bad decision doesn't make it any better.

What's arguably more troubling, your sharing of it had zero to do with furthering the cause of this topic other than over-sensationalizing the situation. It provides zero context to any possible cause of the crash or what role the roundabout may or may not have played. There were two other photos you could have posted, but you chose the one to spin the crash as bad as it possibly could be. It's one thing if the photo would have been included with the attachment on its own, but you had to do extra work and knowingly post the extra photo. You could have just left it with a link to the article.

This seems to be arguing for argument's sake.

The man is on a gurney with no visible injuries, and there is a dented car. I do not understand why this would be problematic. The man cannot be identified in the photo (his face is not visible), and there is no front licence plate.

He could have chosen to not share the image, but from my perspective, it's just a picture of the crash. No forum rules disallow this.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 03, 2020, 05:18:31 PM
If that article were published in Mexico, you might have seen blood on the pavement and organs hanging out of the abdomen on the front page of the newspaper.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 03, 2020, 05:20:58 PM
If that article were published in Mexico, you might have seen blood on the pavement and organs hanging out of the abdomen on the front page of the newspaper.

The last place I would expect censorship would be this forum. Mexican journalism? Guess I can't say I'm familiar, but I appreciate their straightforwardness.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 03, 2020, 05:24:24 PM
I've been through those Augusta roundabouts before (way back in 2011); Cony Circle is impressive to me, even if it's #2 most crash-prone in the state. It's really hard to configure a five-way intersection, so credit where credit's due to Augusta's engineers of yore.

On the other hand, Memorial Circle is arguably simpler, yet features more crashes (at least for 2019). That's not good for a regular four-leg roundabout.
The other factor to consider is total traffic through the intersection. I cannot lookup numbers at the moment, but I suspect we're dealing with circle operating over capacity, which was actually designed without understanding of those limitations. While traffic light on 5-leg would have issues as well, other approaches to distribution of traffic may be considered to unload the sour point - instead of trying to manage unmanageable.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on January 03, 2020, 06:25:50 PM
^I won't post a picture of any of the many injury crashes that have occurred in the Cony circle so not to be censored.  Posting a picture involving an injury accident is outrageous apparently.

Get over yourself. Apparently you're new to social media. News outlets (at least around here) get crucified when they post that kind of picture on social media. You never know who may not know about their loved one being involved in an accident. Finding out via social media is not usually a way loved ones prefer to find out. Your decision to continue one newspaper's bad decision doesn't make it any better.

What's arguably more troubling, your sharing of it had zero to do with furthering the cause of this topic other than over-sensationalizing the situation. It provides zero context to any possible cause of the crash or what role the roundabout may or may not have played. There were two other photos you could have posted, but you chose the one to spin the crash as bad as it possibly could be. It's one thing if the photo would have been included with the attachment on its own, but you had to do extra work and knowingly post the extra photo. You could have just left it with a link to the article.

This seems to be arguing for argument's sake.

The man is on a gurney with no visible injuries, and there is a dented car. I do not understand why this would be problematic. The man cannot be identified in the photo (his face is not visible), and there is no front licence plate.

He could have chosen to not share the image, but from my perspective, it's just a picture of the crash. No forum rules disallow this.

I never said it was against the forum rules. Is it in poor taste? I think many would agree that it is. You don't know if the injured person is known by a member here. Does it help further the investigation into roundabout performance? No, which is the whole point of this 90+ page thread. I asked why the photo was posted, and all I got was a smartass remark. All it does is help sensationalize a crash report and waste bandwidth; it added nothing to help determine why certain roundabouts have poorer performance than others. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 03, 2020, 06:30:45 PM
I've been through those Augusta roundabouts before (way back in 2011); Cony Circle is impressive to me, even if it's #2 most crash-prone in the state. It's really hard to configure a five-way intersection, so credit where credit's due to Augusta's engineers of yore.

On the other hand, Memorial Circle is arguably simpler, yet features more crashes (at least for 2019). That's not good for a regular four-leg roundabout.
The other factor to consider is total traffic through the intersection. I cannot lookup numbers at the moment, but I suspect we're dealing with circle operating over capacity, which was actually designed without understanding of those limitations. While traffic light on 5-leg would have issues as well, other approaches to distribution of traffic may be considered to unload the sour point - instead of trying to manage unmanageable.

Worst-case, they could always signalize the roundabouts. But I cannot even begin to imagine how bad the traffic would be.

At the Memorial Circle, I'm picturing a giant "squareabout" going in front of the CVS and then behind the triangle building. There would be a left turn from Cony St to northbound Bangor St. If I can find the time, I'll mock something up.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 03, 2020, 06:39:10 PM
I never said it was against the forum rules. Is it in poor taste? I think many would agree that it is. You don't know if the injured person is known by a member here. Does it help further the investigation into roundabout performance? No, which is the whole point of this 90+ page thread. I asked why the photo was posted, and all I got was a smartass remark. All it does is help sensationalize a crash report and waste bandwidth; it added nothing to help determine why certain roundabouts have poorer performance than others.

I know you didn't say that, but you're making a big deal out of something which isn't inherently wrong.

I think it's a bit ridiculous to presume that the only images that should be posted to this thread, should be those that "further the investigation into roundabout performance". I'll agree that the image from the article did absolutely nothing for this thread (it could have easily been omitted), but you could make the same argument about many of the photos in this thread; many are, at best, tangentially related to the actual topic at hand. But virtually none of the photos actively detract from the conversation. That, in my opinion, is the key point here: his photo may have been in poor taste to some eyes, but generally speaking, I don't think it detracted from the conversation.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 03, 2020, 07:05:51 PM
I was reading this document (http://conf.tac-atc.ca/english/resourcecentre/readingroom/conference/conf2004/docs/s12/clayton.pdf), prepared by Carl Clayton, P.Eng. P.E., Chuan Kua, P.Eng, and Brice Stephenson, P.Eng, which talks about how Edmonton, Alberta's traffic circles compare to so-called "modern roundabouts".

The document was prepared for the Innovative Intersection and Interchange Designs Session of the 2004 Annual Conference of the Transportation Association of Canada in Quebec City.

I quite like the final paragraph:

Quote
Collision rates for the Edmonton roundabouts are relatively high in comparison to other intersections in Edmonton. In instances where roundabouts were converted to typical signalized intersections, the collision rates appear to have decreased rather than increased. This is in conflict with the findings outlined in literature and by practitioners that well designed roundabouts typically have lower collision rates than other forms of at-grade intersections. A possible explanation for this might be that the geometry of Edmonton roundabouts, while conducive to maximizing traffic flows, degraded the superior level of safety typically attributed to roundabouts. Alternatively, another possibility might be that as much of the safety reviews prepared for roundabouts are on lower volume single lane roundabouts, perhaps the safety potential of a roundabout decreases as traffic volumes approach the upper capacity limit. In either case, it would appear to be prudent to avoid trying to accommodate traffic volumes at the higher end of the range recommended in the various design guidelines by using geometry beyond that recommended in the current state-of-the-art guidelines or oval shaped roundabouts.

Why do I like this paragraph? Well, it's 2004, and they're already noticing a trend that larger, heavy-volume roundabouts tend to have higher crash rates than signalized intersections. Edmonton has been lucky enough to have installed, left in place for some time, and then removed some of these roundabouts; evidently, they're a bit safer operating as regular signalized intersections.

Tangentially-related: the pentagon-shaped Bonnie Doon roundabout in Edmonton has been replaced by a traffic light (https://globalnews.ca/news/5731351/bonnie-doon-traffic-circle-intersection-valley-line-lrt/) due to an LRT line. This is problematic for locals, as the roundabout served all directions of the five intersection legs, unlike the new signal. Glad I got to drive it a few years ago.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 03, 2020, 08:57:50 PM
Collision rates for the Edmonton roundabouts are relatively high in comparison to other intersections in Edmonton. In instances where roundabouts were converted to typical signalized intersections, the collision rates appear to have decreased rather than increased. This is in conflict with the findings outlined in literature and by practitioners that well designed roundabouts typically have lower collision rates than other forms of at-grade intersections. A possible explanation for this might be that the geometry of Edmonton roundabouts, while conducive to maximizing traffic flows, degraded the superior level of safety typically attributed to roundabouts. Alternatively, another possibility might be that as much of the safety reviews prepared for roundabouts are on lower volume single lane roundabouts, perhaps the safety potential of a roundabout decreases as traffic volumes approach the upper capacity limit. In either case, it would appear to be prudent to avoid trying to accommodate traffic volumes at the higher end of the range recommended in the various design guidelines by using geometry beyond that recommended in the current state-of-the-art guidelines or oval shaped roundabouts.

Edmonton really is an interesting case study.  According to Edmonton's 2018 crash report, the unsignalized multi-lane roundabout at 107 Avenue & 142 Street was the most crash prone intersection in the city with 93 crashes.  Yet the 118th Avenue & St Albert Trail signalized roundabout in Edmonton didn't even crack the top 10, and it's a triple-lane roundabout no less.

(https://i.imgur.com/NCvx6I9.png)
https://www.edmonton.ca/transportation/PDF/2018MVC_AnnualReport.pdf

(https://i.imgur.com/tgJie5K.jpg)

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 14, 2020, 01:23:45 PM
I'd love to simply ignore this thread entirely, but I keep making the same mistake of coming back when there's a new post, in the [insane?] hopes there is going to be some new information that I could maybe use. But it looks like I am better-off sticking with my Google News feed and industry-supported sources. If I want crash reports, I'll just go straight to the source and cut out the snarky middleman.

Can you go to your industry-supported sources and track down crash data for the Taylor Street and Shawano Avenue roundabout in Green Bay?  I believe that roundabout was constructed in 2011 and still haven't been able to track down crash data for it.  Let's figure out how well (or poorly) it's doing.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 29, 2020, 03:14:11 PM
There have been at least 6 trucks that have tipped over at Worthington, MN roundabouts since 2015.  Now they are going to refine the curbing to try to prevent these truck tip-overs.  Hopefully whatever they do helps.

Roundabout redesign will improve Worthington's traffic circles
https://www.dglobe.com/business/transportation/4885702-Roundabout-redesign-will-improve-Worthingtons-traffic-circles



August 7, 2015 - Names released in semi roundabout accident
https://www.dglobe.com/news/3813093-names-released-semi-roundabout-accident

October 27, 2017 - These little piggies almost didn't make it to market when a Minn. hog truck rolled
https://www.agweek.com/news/4350581-these-little-piggies-almost-didnt-make-it-market-when-minn-hog-truck-rolled

November 10, 2017 - Tanker hauling cream overturns in Worthington roundabout
https://www.dglobe.com/news/accidents/4356792-tanker-hauling-cream-overturns-worthington-roundabout

July 21, 2018 - A roundabout rollover
https://www.dglobe.com/news/accidents/4475427-roundabout-rollover

August 1, 2018 - Spilled grain in Worthington roundabout
https://www.dglobe.com/news/accidents/4479958-spilled-grain-worthington-roundabout

October 22, 2018 - Roundabout Accident Sends One To Hospital
https://kicdam.com/news/170071-roundabout-accident-sends-one-to-hospital/

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 29, 2020, 03:34:52 PM
Maybe if we built these rural roundabouts a bit bigger, we wouldn't even need to use truck aprons.

Exhibit A: this two-lane suburban roundabout (https://www.google.com/maps/@47.8485889,-122.0057235,96m/data=!3m1!1e3) in Snohomish County, WA.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 29, 2020, 03:52:42 PM
Maybe if we built these rural roundabouts a bit bigger, we wouldn't even need to use truck aprons.

Exhibit A: this two-lane suburban roundabout (https://www.google.com/maps/@47.8485889,-122.0057235,96m/data=!3m1!1e3) in Snohomish County, WA.
That requires qualified engineers understanding what they are doing; so nope, not gonna happen.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on January 29, 2020, 04:10:01 PM
Maybe if we built these rural roundabouts a bit bigger, we wouldn't even need to use truck aprons.

Exhibit A: this two-lane suburban roundabout (https://www.google.com/maps/@47.8485889,-122.0057235,96m/data=!3m1!1e3) in Snohomish County, WA.

Bigger comes with a whole new set of problems.

Maybe if we built these rural roundabouts a bit bigger, we wouldn't even need to use truck aprons.

Exhibit A: this two-lane suburban roundabout (https://www.google.com/maps/@47.8485889,-122.0057235,96m/data=!3m1!1e3) in Snohomish County, WA.
That requires qualified engineers understanding what they are doing; so nope, not gonna happen.

On top of that, you have software firms that are trying to take the skilled engineer out of the equation. Programs like Torus allow just about anyone with meager CAD skills think they can design a roundabout. Garbage in, garbage out.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 29, 2020, 04:30:18 PM

Maybe if we built these rural roundabouts a bit bigger, we wouldn't even need to use truck aprons.

Exhibit A: this two-lane suburban roundabout (https://www.google.com/maps/@47.8485889,-122.0057235,96m/data=!3m1!1e3) in Snohomish County, WA.

Bigger comes with a whole new set of problems.

This.

For one thing, years ago, it was commonly stated that larger ICDs encourage drivers to go too fast through the roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 29, 2020, 04:45:26 PM

Maybe if we built these rural roundabouts a bit bigger, we wouldn't even need to use truck aprons.

Exhibit A: this two-lane suburban roundabout (https://www.google.com/maps/@47.8485889,-122.0057235,96m/data=!3m1!1e3) in Snohomish County, WA.

Bigger comes with a whole new set of problems.

This.

For one thing, years ago, it was commonly stated that larger ICDs encourage drivers to go too fast through the roundabout.

Yeah, I know. Speed. Got it. The cause of all of our problems.

But people are going around larger roundabouts at what, maybe 30 mph? Instead of 15 or 20? Increasing the design speed to be closer to the approach limit might then allow you to remove the truck apron, and reduce the chance for tip-over.

I'm not saying our urban or suburban roundabouts need to be designed for 30+ mph circulating speeds, but these rural roundabouts are distant cousins at best. Different traffic; different needs; different environment.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on January 29, 2020, 04:47:53 PM
Maybe if we built these rural roundabouts a bit bigger, we wouldn't even need to use truck aprons.

Exhibit A: this two-lane suburban roundabout (https://www.google.com/maps/@47.8485889,-122.0057235,96m/data=!3m1!1e3) in Snohomish County, WA.
That requires qualified engineers understanding what they are doing; so nope, not gonna happen.

Other than there are road markings, not much different than a traditional NJ traffic circle.

The NJ 70/72 circle is a great example.  And of the 5 roadways leading into it, 3 have 55 mph limits; the other 2 have 50 mph limits.

https://maps.app.goo.gl/fKfeKYQC8cHuvu3N9
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on January 29, 2020, 04:55:45 PM

Maybe if we built these rural roundabouts a bit bigger, we wouldn't even need to use truck aprons.

Exhibit A: this two-lane suburban roundabout (https://www.google.com/maps/@47.8485889,-122.0057235,96m/data=!3m1!1e3) in Snohomish County, WA.

Bigger comes with a whole new set of problems.

This.

For one thing, years ago, it was commonly stated that larger ICDs encourage drivers to go too fast through the roundabout.

Yeah, I know. Speed. Got it. The cause of all of our problems.

But people are going around larger roundabouts at what, maybe 30 mph? Instead of 15 or 20? Increasing the design speed to be closer to the approach limit might then allow you to remove the truck apron, and reduce the chance for tip-over.

I'm not saying our urban or suburban roundabouts need to be designed for 30+ mph circulating speeds, but these rural roundabouts are distant cousins at best. Different traffic; different needs; different environment.

You're suggesting to nearly double the "design" speed. Faster speeds = greater risk of severe injury, which is supposed to be one of the top selling points for roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 29, 2020, 05:23:33 PM

Maybe if we built these rural roundabouts a bit bigger, we wouldn't even need to use truck aprons.

Exhibit A: this two-lane suburban roundabout (https://www.google.com/maps/@47.8485889,-122.0057235,96m/data=!3m1!1e3) in Snohomish County, WA.

Bigger comes with a whole new set of problems.

This.

For one thing, years ago, it was commonly stated that larger ICDs encourage drivers to go too fast through the roundabout.

Yeah, I know. Speed. Got it. The cause of all of our problems.

But people are going around larger roundabouts at what, maybe 30 mph? Instead of 15 or 20? Increasing the design speed to be closer to the approach limit might then allow you to remove the truck apron, and reduce the chance for tip-over.

I'm not saying our urban or suburban roundabouts need to be designed for 30+ mph circulating speeds, but these rural roundabouts are distant cousins at best. Different traffic; different needs; different environment.

You're suggesting to nearly double the "design" speed. Faster speeds = greater risk of severe injury, which is supposed to be one of the top selling points for roundabouts.
Which only means concept should be reviewed for feasibility as improving safety creates more safety hazards.
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on January 29, 2020, 10:12:41 PM
I actually think "everything's bigger in America" is the #1 reason roundabouts are less common in the US and don't work as well here as they do in the UK.

We expect big houses, big cars, big roads, big everything, and making some extra turns of your steering wheel, with precision, in the confined space that is a roundabout, runs totally contrary to the way we've developed as a country in the past two centuries.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on January 29, 2020, 10:31:14 PM
I actually think "everything's bigger in America" is the #1 reason roundabouts are less common in the US and don't work as well here as they do in the UK.

We expect big houses, big cars, big roads, big everything, and making some extra turns of your steering wheel, with precision, in the confined space that is a roundabout, runs totally contrary to the way we've developed as a country in the past two centuries.

I disagree. Roundabouts are designed with the same sized vehicles as any other component of the American highway. The way I see far too many handle basic turns, we've gotten lazy. We fell in love with the traffic light. Most seek the "safety" of being told what to do and when. When human judgement comes into play is when crashes happen. The skill of the American driver has decreased with the addition of new distractions, shorter attention spans (thank you, Twitter), less rigorous drivers ed, and overconfidence in their vehicle's capabilities.
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on January 29, 2020, 10:51:08 PM
I agree, but I can agree without walking back, clarifying, or altering my original point. So I guess I disagree that there's a disagreement.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 30, 2020, 03:39:05 AM
I'm not saying our urban or suburban roundabouts need to be designed for 30+ mph circulating speeds, but these rural roundabouts are distant cousins at best. Different traffic; different needs; different environment.
You're suggesting to nearly double the "design" speed. Faster speeds = greater risk of severe injury, which is supposed to be one of the top selling points for roundabouts.
Which only means concept should be reviewed for feasibility as improving safety creates more safety hazards.

Right. Maybe the design speed is increased, but speed does not exist in a vacuum. It has to be weighed against other hazards. By increasing the ICD, you can get rid of the truck apron, which may have its own benefits (perhaps outweighing the benefits of tighter circles). Remember that speed alone is not dangerous; it's suddenly coming to a stop that gets you. If roundabouts can be designed for high speed operation, why not? It certainly makes sense along roads with existing high speeds.

My understanding with designing low-speed roundabouts is that the low speeds decrease braking distance and improve reaction time, but both of these things seem to be the result of classic American "everyone sucks so make it as easy as possible" design philosophy. I generally defend this philosophy, but how can we be sure that emergency stops and reaction time concerns aren't symptoms related to the tightness of many of these circles? How do we know that reactionary/emergency movements wouldn't be reduced at roundabouts with larger ICDs? How likely might it be that larger roundabouts would have fewer truck tip-overs? Would larger roundabouts reduce judgement errors? Would we see fewer property-damage collisions (a major issue at roundabouts)?

I'm not asking these questions as though anyone has answers, but I steadfastly refuse to accept any design standards as perfect, especially when there are totally different designs all across the planet for the same situation. As an example, in Germany (http://teachamerica.com/RAB14/RAB14papers/RAB14ppr045_Brilon.pdf) (p 7), it's accepted that rural roundabouts do not need aprons. The UK also does not seem to use them.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 30, 2020, 08:23:12 AM
I actually think "everything's bigger in America" is the #1 reason roundabouts are less common in the US and don't work as well here as they do in the UK.

We expect big houses, big cars, big roads, big everything, and making some extra turns of your steering wheel, with precision, in the confined space that is a roundabout, runs totally contrary to the way we've developed as a country in the past two centuries.

I disagree. Roundabouts are designed with the same sized vehicles as any other component of the American highway. The way I see far too many handle basic turns, we've gotten lazy. We fell in love with the traffic light. Most seek the "safety" of being told what to do and when. When human judgement comes into play is when crashes happen. The skill of the American driver has decreased with the addition of new distractions, shorter attention spans (thank you, Twitter), less rigorous drivers ed, and overconfidence in their vehicle's capabilities.
Thing is, driving is not an art or primary job for most people - it is a necessary evil to get from point A to point B. Don't expect people to practice that for the sake of art.
Moreover, engineering skill is recently lacking in US. Unlike driving, this is the primary job for many involved. And that is what is lacking. I am not sure if this is about too much twitter in design offices or lack of H-1B visas what hurts things....
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on January 30, 2020, 08:45:53 AM
I don't see a lack of engineering skill in the U.S.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on January 30, 2020, 08:51:29 AM

Maybe if we built these rural roundabouts a bit bigger, we wouldn't even need to use truck aprons.

Exhibit A: this two-lane suburban roundabout (https://www.google.com/maps/@47.8485889,-122.0057235,96m/data=!3m1!1e3) in Snohomish County, WA.

Bigger comes with a whole new set of problems.

This.

For one thing, years ago, it was commonly stated that larger ICDs encourage drivers to go too fast through the roundabout.

Yeah, I know. Speed. Got it. The cause of all of our problems.

But people are going around larger roundabouts at what, maybe 30 mph? Instead of 15 or 20? Increasing the design speed to be closer to the approach limit might then allow you to remove the truck apron, and reduce the chance for tip-over.

I'm not saying our urban or suburban roundabouts need to be designed for 30+ mph circulating speeds, but these rural roundabouts are distant cousins at best. Different traffic; different needs; different environment.

You're suggesting to nearly double the "design" speed. Faster speeds = greater risk of severe injury, which is supposed to be one of the top selling points for roundabouts.

You're thinking of a roundabout design as a one-size-fits-all design.  A roundabout in a rural area with little traffic may be able to obtain faster speeds than one in an urban area.

For the most part, a single lane roundabout's issue wouldn't be the speed of the roundabout, it would be the failure of people yielding prior to entering. 

I don't see a lack of engineering skill in the U.S.

Generally speaking, neither do I.  Most things are built well.  Yes there will be an occasional issue, and it will make a lot of news, and they will be investigated.  Don't expect most engineering issues in a foreign country to make much news in the US.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on January 30, 2020, 09:06:08 AM
I actually think "everything's bigger in America" is the #1 reason roundabouts are less common in the US and don't work as well here as they do in the UK.

We expect big houses, big cars, big roads, big everything, and making some extra turns of your steering wheel, with precision, in the confined space that is a roundabout, runs totally contrary to the way we've developed as a country in the past two centuries.

I disagree. Roundabouts are designed with the same sized vehicles as any other component of the American highway. The way I see far too many handle basic turns, we've gotten lazy. We fell in love with the traffic light. Most seek the "safety" of being told what to do and when. When human judgement comes into play is when crashes happen. The skill of the American driver has decreased with the addition of new distractions, shorter attention spans (thank you, Twitter), less rigorous drivers ed, and overconfidence in their vehicle's capabilities.
Thing is, driving is not an art or primary job for most people - it is a necessary evil to get from point A to point B. Don't expect people to practice that for the sake of art.
Moreover, engineering skill is recently lacking in US. Unlike driving, this is the primary job for many involved. And that is what is lacking. I am not sure if this is about too much twitter in design offices or lack of H-1B visas what hurts things....

I never said it was an art, but you did hit on why we won't see meaningful crash reductions until we go to autonomous vehicles. Driving has become a necessary, mindless task. Too many drivers are glued to their smartphones when behind the wheel. As for engineering skill, I'll only agree that there is a shortage of skilled labor in the industry.

Maybe if we built these rural roundabouts a bit bigger, we wouldn't even need to use truck aprons.

Exhibit A: this two-lane suburban roundabout (https://www.google.com/maps/@47.8485889,-122.0057235,96m/data=!3m1!1e3) in Snohomish County, WA.
Bigger comes with a whole new set of problems.
This.
For one thing, years ago, it was commonly stated that larger ICDs encourage drivers to go too fast through the roundabout.
Yeah, I know. Speed. Got it. The cause of all of our problems.

But people are going around larger roundabouts at what, maybe 30 mph? Instead of 15 or 20? Increasing the design speed to be closer to the approach limit might then allow you to remove the truck apron, and reduce the chance for tip-over.

I'm not saying our urban or suburban roundabouts need to be designed for 30+ mph circulating speeds, but these rural roundabouts are distant cousins at best. Different traffic; different needs; different environment.
You're suggesting to nearly double the "design" speed. Faster speeds = greater risk of severe injury, which is supposed to be one of the top selling points for roundabouts.
You're thinking of a roundabout design as a one-size-fits-all design.  A roundabout in a rural area with little traffic may be able to obtain faster speeds than one in an urban area.

It has nothing to do with urban vs rural. It's a simple fact of physics. More velocity results in more force resulting in more injury. The point of conflict doesn't change just because you're in a rural setting.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 30, 2020, 10:50:41 AM
I don't see a lack of engineering skill in the U.S.
Two recent R1 projects - Washington ave ext and  7-787  interchange were rebuilt to original lane layout, if not to original blueprints. Some lane realignment was pretty obvious thing to do.I guess all engineering genius from R1 was absorbed by Exit3 project?
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on January 30, 2020, 11:24:30 AM
I don't see a lack of engineering skill in the U.S.
Two recent R1 projects - Washington ave ext and  7-787  interchange were rebuilt to original lane layout, if not to original blueprints. Some lane realignment was pretty obvious thing to do.I guess all engineering genius from R1 was absorbed by Exit3 project?

You can confirm there was no political and/or financial influence on those decisions? What was the intent of the project pavement rehab or reconstruction? Money may not have been available for the desirable reconstruction.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on January 30, 2020, 11:45:08 AM


I don't see a lack of engineering skill in the U.S.
Two recent R1 projects - Washington ave ext and  7-787  interchange were rebuilt to original lane layout, if not to original blueprints. Some lane realignment was pretty obvious thing to do.I guess all engineering genius from R1 was absorbed by Exit3 project?

I don't see how this shows lack of engineering skill.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 30, 2020, 12:27:46 PM
I don't see a lack of engineering skill in the U.S.
Two recent R1 projects - Washington ave ext and  7-787  interchange were rebuilt to original lane layout, if not to original blueprints. Some lane realignment was pretty obvious thing to do.I guess all engineering genius from R1 was absorbed by Exit3 project?

You can confirm there was no political and/or financial influence on those decisions? What was the intent of the project pavement rehab or reconstruction? Money may not have been available for the desirable reconstruction.
those were not minor pavement rehab, those were deep reconstructions. Lane realignment within existing footprint would be pretty straightforward no extra cost task.
In at least one of these projects,  traffic improvement was an objective as NYSDOT even took up an unbearable task of synchronizing traffic lights.  All 3 of them. Apparently, they gave up after realizing this is too much of engineering work to do. 

As for structural engineering.. I can only pray it works better than traffic engineering.
On a grand scheme of things,  professional growth comes with practice. If lane realignment becomes too much of a task to do, then what do you expect in terms of professional growth?
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on January 30, 2020, 12:30:50 PM
I don't see a lack of engineering skill in the U.S.
Two recent R1 projects - Washington ave ext and  7-787  interchange were rebuilt to original lane layout, if not to original blueprints. Some lane realignment was pretty obvious thing to do.I guess all engineering genius from R1 was absorbed by Exit3 project?

You can confirm there was no political and/or financial influence on those decisions? What was the intent of the project pavement rehab or reconstruction? Money may not have been available for the desirable reconstruction.
those were not minor pavement rehab, those were deep reconstructions. Lane realignment within existing footprint would be pretty straightforward no extra cost task.
In at least one of these projects,  traffic improvement was an objective as NYSDOT even took up an unbearable task of synchronizing traffic lights.  All 3 of them. Apparently, they gave up after realizing this is too much of engineering work to do. 

As for structural engineering.. I can only pray it works better than traffic engineering.
On a grand scheme of things,  professional growth comes with practice. If lane realignment becomes too much of a task to do, then what do you expect in terms of professional growth?
I still don't know what you're getting at.  Both projects are fine as is.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 30, 2020, 12:44:35 PM
I don't see a lack of engineering skill in the U.S.
Two recent R1 projects - Washington ave ext and  7-787  interchange were rebuilt to original lane layout, if not to original blueprints. Some lane realignment was pretty obvious thing to do.I guess all engineering genius from R1 was absorbed by Exit3 project?

You can confirm there was no political and/or financial influence on those decisions? What was the intent of the project pavement rehab or reconstruction? Money may not have been available for the desirable reconstruction.
those were not minor pavement rehab, those were deep reconstructions. Lane realignment within existing footprint would be pretty straightforward no extra cost task.
In at least one of these projects,  traffic improvement was an objective as NYSDOT even took up an unbearable task of synchronizing traffic lights.  All 3 of them. Apparently, they gave up after realizing this is too much of engineering work to do. 

As for structural engineering.. I can only pray it works better than traffic engineering.
On a grand scheme of things,  professional growth comes with practice. If lane realignment becomes too much of a task to do, then what do you expect in terms of professional growth?
I still don't know what you're getting at.  Both projects are fine as is.

They are just so-so, ignoring traffic pattern changes over the decades, failing to use a chance to improve at a minimal cost (if any additional cost at all), and failing to reach some of published objectives - like synchronizing traffic lights.
Yes, it is a passing grade - work was performed using 20+ blueprints. WHo cares?
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on January 30, 2020, 12:59:35 PM
I don't see a lack of engineering skill in the U.S.
Two recent R1 projects - Washington ave ext and  7-787  interchange were rebuilt to original lane layout, if not to original blueprints. Some lane realignment was pretty obvious thing to do.I guess all engineering genius from R1 was absorbed by Exit3 project?

You can confirm there was no political and/or financial influence on those decisions? What was the intent of the project pavement rehab or reconstruction? Money may not have been available for the desirable reconstruction.
those were not minor pavement rehab, those were deep reconstructions. Lane realignment within existing footprint would be pretty straightforward no extra cost task.
In at least one of these projects,  traffic improvement was an objective as NYSDOT even took up an unbearable task of synchronizing traffic lights.  All 3 of them. Apparently, they gave up after realizing this is too much of engineering work to do. 

As for structural engineering.. I can only pray it works better than traffic engineering.
On a grand scheme of things,  professional growth comes with practice. If lane realignment becomes too much of a task to do, then what do you expect in terms of professional growth?
I still don't know what you're getting at.  Both projects are fine as is.

They are just so-so, ignoring traffic pattern changes over the decades, failing to use a chance to improve at a minimal cost (if any additional cost at all), and failing to reach some of published objectives - like synchronizing traffic lights.
Yes, it is a passing grade - work was performed using 20+ blueprints. WHo cares?
The only issue I'm aware of along there was the intersection with New Karner and there was no funding to deal with that completely (i.e., the backup turning right onto New Karner from Wash. Ave. Ext. WB).

In terms of traffic signal synchronization, I wonder if that made it into the design approval document.  I imagine fiscal constraints came into play there as well, especially given the large share of local funds put on the project.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 30, 2020, 01:16:14 PM
I don't see a lack of engineering skill in the U.S.
Two recent R1 projects - Washington ave ext and  7-787  interchange were rebuilt to original lane layout, if not to original blueprints. Some lane realignment was pretty obvious thing to do.I guess all engineering genius from R1 was absorbed by Exit3 project?

You can confirm there was no political and/or financial influence on those decisions? What was the intent of the project pavement rehab or reconstruction? Money may not have been available for the desirable reconstruction.
those were not minor pavement rehab, those were deep reconstructions. Lane realignment within existing footprint would be pretty straightforward no extra cost task.
In at least one of these projects,  traffic improvement was an objective as NYSDOT even took up an unbearable task of synchronizing traffic lights.  All 3 of them. Apparently, they gave up after realizing this is too much of engineering work to do. 

As for structural engineering.. I can only pray it works better than traffic engineering.
On a grand scheme of things,  professional growth comes with practice. If lane realignment becomes too much of a task to do, then what do you expect in terms of professional growth?
I still don't know what you're getting at.  Both projects are fine as is.

They are just so-so, ignoring traffic pattern changes over the decades, failing to use a chance to improve at a minimal cost (if any additional cost at all), and failing to reach some of published objectives - like synchronizing traffic lights.
Yes, it is a passing grade - work was performed using 20+ blueprints. WHo cares?
The only issue I'm aware of along there was the intersection with New Karner and there was no funding to deal with that completely (i.e., the backup turning right onto New Karner from Wash. Ave. Ext. WB).

In terms of traffic signal synchronization, I wonder if that made it into the design approval document.  I imagine fiscal constraints came into play there as well, especially given the large share of local funds put on the project.
And I saw - with my own eyes - how intersection by wallmart was rebuilt without a slightest though. And I saw multiple iterations of synchronizations attempts along Washington - to the point I was ready to pull over to explain folks what is being done wrong...  That was an epic try, I should say.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on January 30, 2020, 02:19:10 PM


I don't see a lack of engineering skill in the U.S.
Two recent R1 projects - Washington ave ext and  7-787  interchange were rebuilt to original lane layout, if not to original blueprints. Some lane realignment was pretty obvious thing to do.I guess all engineering genius from R1 was absorbed by Exit3 project?

You can confirm there was no political and/or financial influence on those decisions? What was the intent of the project pavement rehab or reconstruction? Money may not have been available for the desirable reconstruction.
those were not minor pavement rehab, those were deep reconstructions. Lane realignment within existing footprint would be pretty straightforward no extra cost task.
In at least one of these projects,  traffic improvement was an objective as NYSDOT even took up an unbearable task of synchronizing traffic lights.  All 3 of them. Apparently, they gave up after realizing this is too much of engineering work to do. 

As for structural engineering.. I can only pray it works better than traffic engineering.
On a grand scheme of things,  professional growth comes with practice. If lane realignment becomes too much of a task to do, then what do you expect in terms of professional growth?
I still don't know what you're getting at.  Both projects are fine as is.

They are just so-so, ignoring traffic pattern changes over the decades, failing to use a chance to improve at a minimal cost (if any additional cost at all), and failing to reach some of published objectives - like synchronizing traffic lights.
Yes, it is a passing grade - work was performed using 20+ blueprints. WHo cares?
The only issue I'm aware of along there was the intersection with New Karner and there was no funding to deal with that completely (i.e., the backup turning right onto New Karner from Wash. Ave. Ext. WB).

In terms of traffic signal synchronization, I wonder if that made it into the design approval document.  I imagine fiscal constraints came into play there as well, especially given the large share of local funds put on the project.
And I saw - with my own eyes - how intersection by wallmart was rebuilt without a slightest though. And I saw multiple iterations of synchronizations attempts along Washington - to the point I was ready to pull over to explain folks what is being done wrong...  That was an epic try, I should say.

You weren't on the design squad and therefore I doubt that you know that the project went forward without thought and given my experience, I find the idea of a project to be designed without thought to be ludicrous. 

The Walmart intersection operates like it did before.  I don't see an engineering issue there.

I don't know what went on regarding the synchronization if it happened as you described.  If it was required in the contract, then it would have been taken care of.  A contractor cannot "just give up" on implementing a contract.

All I can say is that I haven't come across any examples of engineering incompetence very often -- if at all -- during my career.  I have personally witnessed engineers having to design less than the preferred treatments due to fiscal constraints very often, though (I might even say constantly).  So, if an engineer not in the know comes along after a project and whines about the treatment being inadequate, I would place my bet on fiscal constraints rather than lack of skill.  In fact, you might even say that a higher level of skill is needed to do the best you can with the available funds (as opposed to thinking there was an unlimited pot to draw from).

(personal opinion emphasized)
Title: Re: Crash prone 'modern roundabouts'
Post by: ScottRAB on January 30, 2020, 02:47:09 PM
There have been at least 6 trucks that have tipped over at Worthington, MN roundabouts since 2015.  Now they are going to refine the curbing to try to prevent these truck tip-overs.  Hopefully whatever they do helps.

Roundabout redesign will improve Worthington's traffic circles
https://www.dglobe.com/business/transportation/4885702-Roundabout-redesign-will-improve-Worthingtons-traffic-circles



Since a recent study found a majority of truck drivers don’t understand how to drive a modern roundabout, it stands to reason most drivers don’t understand how a truck is supposed to drive a modern roundabout.

Modern roundabouts are designed for trucks, large vehicles, and trailer towing vehicles by including the center flat area around the circle.  It’s not a sidewalk, it’s called a truck apron, and it’s for trucks to begin a sharp right or end a left or U-turn on.  But they should obey the warning speed and know their vehicle.

Roundabout Trucks Videos:
Million mile driver: STAA, Porterville, CA:
FHWA:
Washington County, WI: http://tinyurl.com/trucksRABwi
U-turn: http://tinyurl.com/rabtruckuturn 
Windsor-Essex Parkway, Canada: http://tinyurl.com/windsoressexRAB
Washington DOT simulation:
Washington DOT US2/Rice Rd:  Oregon DOT tests: Deschutes County Fairgrounds  https://tinyurl.com/y7yfpw5q
   Portland Meadows Parking lot  https://tinyurl.com/ycxpqf3u
   Medford:
Opelika, AL: http://opelika-al.gov/CivicMedia?VID=3#player
Baker Road at Dan Hoey, Washtenaw County:
Alaska DOT: http://dot.alaska.gov/nreg/danby-wembley/
Florida DOT: https://www.fdot.gov/agencyresources/roundabouts/index.shtm
Truck Apron how to:
Trucks in action, Green Bay:

Trucks Use Both Lanes, just like at other intersections:
Anderson, CA: https://goo.gl/maps/kXoMwuF67GHAQqZa8

Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on January 30, 2020, 03:01:25 PM


I don't see a lack of engineering skill in the U.S.
Two recent R1 projects - Washington ave ext and  7-787  interchange were rebuilt to original lane layout, if not to original blueprints. Some lane realignment was pretty obvious thing to do.I guess all engineering genius from R1 was absorbed by Exit3 project?

You can confirm there was no political and/or financial influence on those decisions? What was the intent of the project pavement rehab or reconstruction? Money may not have been available for the desirable reconstruction.
those were not minor pavement rehab, those were deep reconstructions. Lane realignment within existing footprint would be pretty straightforward no extra cost task.
In at least one of these projects,  traffic improvement was an objective as NYSDOT even took up an unbearable task of synchronizing traffic lights.  All 3 of them. Apparently, they gave up after realizing this is too much of engineering work to do. 

As for structural engineering.. I can only pray it works better than traffic engineering.
On a grand scheme of things,  professional growth comes with practice. If lane realignment becomes too much of a task to do, then what do you expect in terms of professional growth?
I still don't know what you're getting at.  Both projects are fine as is.

They are just so-so, ignoring traffic pattern changes over the decades, failing to use a chance to improve at a minimal cost (if any additional cost at all), and failing to reach some of published objectives - like synchronizing traffic lights.
Yes, it is a passing grade - work was performed using 20+ blueprints. WHo cares?
The only issue I'm aware of along there was the intersection with New Karner and there was no funding to deal with that completely (i.e., the backup turning right onto New Karner from Wash. Ave. Ext. WB).

In terms of traffic signal synchronization, I wonder if that made it into the design approval document.  I imagine fiscal constraints came into play there as well, especially given the large share of local funds put on the project.
And I saw - with my own eyes - how intersection by wallmart was rebuilt without a slightest though. And I saw multiple iterations of synchronizations attempts along Washington - to the point I was ready to pull over to explain folks what is being done wrong...  That was an epic try, I should say.

You weren't on the design squad and therefore I doubt that you know that the project went forward without thought and given my experience, I find the idea of a project to be designed without thought to be ludicrous. 

The Walmart intersection operates like it did before.  I don't see an engineering issue there.

I don't know what went on regarding the synchronization if it happened as you described.  If it was required in the contract, then it would have been taken care of.  A contractor cannot "just give up" on implementing a contract.

All I can say is that I haven't come across any examples of engineering incompetence very often -- if at all -- during my career.  I have personally witnessed engineers having to design less than the preferred treatments due to fiscal constraints very often, though (I might even say constantly).  So, if an engineer not in the know comes along after a project and whines about the treatment being inadequate, I would place my bet on fiscal constraints rather than lack of skill.  In fact, you might even say that a higher level of skill is needed to do the best you can with the available funds (as opposed to thinking there was an unlimited pot to draw from).

(personal opinion emphasized)

This is exactly why I asked about political and/or fiscal constraints earlier. Armchair engineers are about as bad as armchair quarterbacks. What looks stupid on the surface >90% of the time is not what the engineer wanted, but had to do because of the higher-ups. This is why I mentioned several pages ago about roadway design being a balancing act: safety, design standards, funding, and politics all play a role. I have yet to encounter a project that has ever gone 100% per the engineers' preferred design.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on January 30, 2020, 03:04:06 PM


I don't see a lack of engineering skill in the U.S.
Two recent R1 projects - Washington ave ext and  7-787  interchange were rebuilt to original lane layout, if not to original blueprints. Some lane realignment was pretty obvious thing to do.I guess all engineering genius from R1 was absorbed by Exit3 project?

You can confirm there was no political and/or financial influence on those decisions? What was the intent of the project pavement rehab or reconstruction? Money may not have been available for the desirable reconstruction.
those were not minor pavement rehab, those were deep reconstructions. Lane realignment within existing footprint would be pretty straightforward no extra cost task.
In at least one of these projects,  traffic improvement was an objective as NYSDOT even took up an unbearable task of synchronizing traffic lights.  All 3 of them. Apparently, they gave up after realizing this is too much of engineering work to do. 

As for structural engineering.. I can only pray it works better than traffic engineering.
On a grand scheme of things,  professional growth comes with practice. If lane realignment becomes too much of a task to do, then what do you expect in terms of professional growth?
I still don't know what you're getting at.  Both projects are fine as is.

They are just so-so, ignoring traffic pattern changes over the decades, failing to use a chance to improve at a minimal cost (if any additional cost at all), and failing to reach some of published objectives - like synchronizing traffic lights.
Yes, it is a passing grade - work was performed using 20+ blueprints. WHo cares?
The only issue I'm aware of along there was the intersection with New Karner and there was no funding to deal with that completely (i.e., the backup turning right onto New Karner from Wash. Ave. Ext. WB).

In terms of traffic signal synchronization, I wonder if that made it into the design approval document.  I imagine fiscal constraints came into play there as well, especially given the large share of local funds put on the project.
And I saw - with my own eyes - how intersection by wallmart was rebuilt without a slightest though. And I saw multiple iterations of synchronizations attempts along Washington - to the point I was ready to pull over to explain folks what is being done wrong...  That was an epic try, I should say.

You weren't on the design squad and therefore I doubt that you know that the project went forward without thought and given my experience, I find the idea of a project to be designed without thought to be ludicrous. 

The Walmart intersection operates like it did before.  I don't see an engineering issue there.

I don't know what went on regarding the synchronization if it happened as you described.  If it was required in the contract, then it would have been taken care of.  A contractor cannot "just give up" on implementing a contract.

All I can say is that I haven't come across any examples of engineering incompetence very often -- if at all -- during my career.  I have personally witnessed engineers having to design less than the preferred treatments due to fiscal constraints very often, though (I might even say constantly).  So, if an engineer not in the know comes along after a project and whines about the treatment being inadequate, I would place my bet on fiscal constraints rather than lack of skill.  In fact, you might even say that a higher level of skill is needed to do the best you can with the available funds (as opposed to thinking there was an unlimited pot to draw from).

(personal opinion emphasized)

This is exactly why I asked about political and/or fiscal constraints earlier. Armchair engineers are about as bad as armchair quarterbacks. What looks stupid on the surface >90% of the time is not what the engineer wanted, but had to do because of the higher-ups. This is why I mentioned several pages ago about roadway design being a balancing act: safety, design standards, funding, and politics all play a role. I have yet to encounter a project that has ever gone 100% per the engineers' preferred design.
Yep, I know we're on the same page.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on January 30, 2020, 03:40:45 PM
You're thinking of a roundabout design as a one-size-fits-all design.  A roundabout in a rural area with little traffic may be able to obtain faster speeds than one in an urban area.
It has nothing to do with urban vs rural. It's a simple fact of physics. More velocity results in more force resulting in more injury. The point of conflict doesn't change just because you're in a rural setting.

Did you even bother to read my post? Because I get the feeling you didn't:

speed does not exist in a vacuum. It has to be weighed against other hazards. By increasing the ICD, you can get rid of the truck apron, which may have its own benefits (perhaps outweighing the benefits of tighter circles). Remember that speed alone is not dangerous; it's suddenly coming to a stop that gets you. If roundabouts can be designed for high speed operation, why not? It certainly makes sense along roads with existing high speeds.

My understanding with designing low-speed roundabouts is that the low speeds decrease braking distance and improve reaction time, but both of these things seem to be the result of classic American "everyone sucks so make it as easy as possible" design philosophy. I generally defend this philosophy, but how can we be sure that emergency stops and reaction time concerns aren't symptoms related to the tightness of many of these circles? How do we know that reactionary/emergency movements wouldn't be reduced at roundabouts with larger ICDs? How likely might it be that larger roundabouts would have fewer truck tip-overs? Would larger roundabouts reduce judgement errors? Would we see fewer property-damage collisions (a major issue at roundabouts)?

I'm not asking these questions as though anyone has answers, but I steadfastly refuse to accept any design standards as perfect, especially when there are totally different designs all across the planet for the same situation. As an example, in Germany (http://teachamerica.com/RAB14/RAB14papers/RAB14ppr045_Brilon.pdf) (p 7), it's accepted that rural roundabouts do not need aprons. The UK also does not seem to use them.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 30, 2020, 03:44:46 PM
The skill of the American driver has decreased with ... less rigorous drivers ed ...

Drivers' ed is less rigorous now than it used to be?
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on January 30, 2020, 04:20:48 PM
You're thinking of a roundabout design as a one-size-fits-all design.  A roundabout in a rural area with little traffic may be able to obtain faster speeds than one in an urban area.
It has nothing to do with urban vs rural. It's a simple fact of physics. More velocity results in more force resulting in more injury. The point of conflict doesn't change just because you're in a rural setting.

Did you even bother to read my post? Because I get the feeling you didn't:

speed does not exist in a vacuum. It has to be weighed against other hazards. By increasing the ICD, you can get rid of the truck apron, which may have its own benefits (perhaps outweighing the benefits of tighter circles). Remember that speed alone is not dangerous; it's suddenly coming to a stop that gets you. If roundabouts can be designed for high speed operation, why not? It certainly makes sense along roads with existing high speeds.

My understanding with designing low-speed roundabouts is that the low speeds decrease braking distance and improve reaction time, but both of these things seem to be the result of classic American "everyone sucks so make it as easy as possible" design philosophy. I generally defend this philosophy, but how can we be sure that emergency stops and reaction time concerns aren't symptoms related to the tightness of many of these circles? How do we know that reactionary/emergency movements wouldn't be reduced at roundabouts with larger ICDs? How likely might it be that larger roundabouts would have fewer truck tip-overs? Would larger roundabouts reduce judgement errors? Would we see fewer property-damage collisions (a major issue at roundabouts)?

I'm not asking these questions as though anyone has answers, but I steadfastly refuse to accept any design standards as perfect, especially when there are totally different designs all across the planet for the same situation. As an example, in Germany (http://teachamerica.com/RAB14/RAB14papers/RAB14ppr045_Brilon.pdf) (p 7), it's accepted that rural roundabouts do not need aprons. The UK also does not seem to use them.

Funny, cause I get the same feeling about you. Same principle as designing an urban 4-lane arterial at 35-mph vs a 4-lane arterial at 55-mph. Have the same intersection angle crash in both cases, and the one with the higher initial speed will have the greater injury severity. In both cases, the roadway was designed for the appropriate speed. In both cases, they have the same weak link at the intersection. Yes, the sudden stop is what gets you, but it's the initial speed that determines how bad the end-result is going to be.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on January 30, 2020, 08:13:33 PM
My understanding with designing low-speed roundabouts is that the low speeds decrease braking distance and improve reaction time, but both of these things seem to be the result of classic American "everyone sucks so make it as easy as possible" design philosophy. I generally defend this philosophy, but how can we be sure that emergency stops and reaction time concerns aren't symptoms related to the tightness of many of these circles? How do we know that reactionary/emergency movements wouldn't be reduced at roundabouts with larger ICDs? How likely might it be that larger roundabouts would have fewer truck tip-overs? Would larger roundabouts reduce judgement errors? Would we see fewer property-damage collisions (a major issue at roundabouts)?

I'm not asking these questions as though anyone has answers, but I steadfastly refuse to accept any design standards as perfect, especially when there are totally different designs all across the planet for the same situation. As an example, in Germany (http://teachamerica.com/RAB14/RAB14papers/RAB14ppr045_Brilon.pdf) (p 7), it's accepted that rural roundabouts do not need aprons. The UK also does not seem to use them.

My recollection of every post in the past 95+ pages isn't the sharpest, but I don't seem to recall anyone ever claiming any design standards were final, let alone perfect. Wisconsin is on their third iteration of their design guidelines. A fourth may not be too far down the line.

It isn't necessarily the presence of the truck apron that is causing the problems. A few of these incidents can be attributed to a poorly designed cross-slope of the circulatory roadway. As far as design standards go, there are varying opinions on how the circulatory roadway should be sloped. A combination of trucks entering too fast, load shift, and crown location contribute to the trucks tipping over. Truck aprons will likely be a fixture of single-lane roundabouts for the foreseeable future, as the circulatory roadway can only get so wide before people try to treat it as two lanes. With the appropriate truck laws, truck aprons could easily disappear from multilane roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on January 30, 2020, 08:21:39 PM
The skill of the American driver has decreased with ... less rigorous drivers ed ...

Drivers' ed is less rigorous now than it used to be?

That's a my-bad...I meant to edit that before finishing my post. That should have said "less rigorous drivers licensing" as in the knowledge tests have gotten easier even in just the 20-years I've had a license.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 31, 2020, 09:59:07 AM


The skill of the American driver has decreased with ... less rigorous drivers ed ...

Drivers' ed is less rigorous now than it used to be?

That's a my-bad...I meant to edit that before finishing my post. That should have said "less rigorous drivers licensing" as in the knowledge tests have gotten easier even in just the 20-years I've had a license.

That surprises me.  I expected the opposite to be true.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 31, 2020, 10:01:30 AM
DaBigE were you able to track down crash data for the triple-lane roundabout at Taylor Street and Shawano Avenue near Green Bay?  It's a major roundabout just off Highway 41 that was constructed nearly 10 years ago yet I can't find crash data on it.  What am i doing wrong here where I can't find any data?  Should not be this difficult (of course maybe I'm just an idiot and don't know what resource to look up... more likely perhaps!).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 31, 2020, 10:08:56 AM
OMG!  A truck tipped over at a Portage Wisconsin roundabout yesterday and crushed a car!  Ok maybe a slight fabrication as the truck was hauling salvaged cars, but with all these truck tip-overs you definitely wouldn't want one to tip over onto your vehicle.  That would end badly! 

Semi spills salvage cars after tipping over in Portage roundabout
(https://i.imgur.com/DlASf4U.jpg)
https://www.nbc15.com/content/news/Semi-spills-salvage-cars-after-tipping-over-in-Portage-roundabout-567430951.html
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on January 31, 2020, 10:30:25 AM
Another roundabout crash that demonstrates how dangerous they can be when approaching them too quickly.  If roundabouts force drivers to slow down then a sharp curve along a roadway forces drivers to slow down too.  But how often are sharp curves along a roadway touted for their safety benefits by traffic safety engineers? 

Quote
Woman killed in single-car rollover at Kennewick roundabout identified
https://www.nbcrightnow.com/news/woman-killed-in-single-car-rollover-at-kennewick-roundabout-identified/article_36cf7194-4374-11ea-b2c9-4bcfe1f06a0f.html

At about 3 a.m. on Jan. 30, Bricia Villasenor-Botello, 29, was driving westbound on 10th Avenue. She failed to negotiate the roundabout at Steptoe Street and her car left the roadway to the west. It rolled several times and crashed through two backyard fences. 
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on January 31, 2020, 10:42:07 AM


The skill of the American driver has decreased with ... less rigorous drivers ed ...

Drivers' ed is less rigorous now than it used to be?

That's a my-bad...I meant to edit that before finishing my post. That should have said "less rigorous drivers licensing" as in the knowledge tests have gotten easier even in just the 20-years I've had a license.

That surprises me.  I expected the opposite to be true.

That makes two of us. Because of the way the local DMV office was arranged, you could watch people take their computerized exams while waiting in line. Some of the questions I think should have been an automatic failure if you got them wrong (basic sign and safety information). Luckily, I think there's a number of drivers' ed programs over-prepare their students, but then there's the law of averages. And not all states require a formal drivers' ed program to sit for a test. This report on drivers' ed around the US (https://www.adtsea.org/webfiles/fnitools/documents/nhtsa-driver-ed-practices-selected-states-report.pdf), while dated, may be surprising to some, especially Table 2.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 31, 2020, 11:13:22 AM
If roundabouts force drivers to slow down then a sharp curve along a roadway forces drivers to slow down too.  But how often are sharp curves along a roadway touted for their safety benefits by traffic safety engineers? 

Well put.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 31, 2020, 11:14:44 AM
Because of the way the local DMV office was arranged, you could watch people take their computerized exams while waiting in line. Some of the questions I think should have been an automatic failure if you got them wrong (basic sign and safety information).

When I got my DL back in the mid-90s, there was no such thing as an "automatic failure" question on the test.  It was 25 questions, as I recall, and you could get up to five wrong.  It didn't matter which questions you got wrong.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on January 31, 2020, 11:42:53 AM
Because of the way the local DMV office was arranged, you could watch people take their computerized exams while waiting in line. Some of the questions I think should have been an automatic failure if you got them wrong (basic sign and safety information).

When I got my DL back in the mid-90s, there was no such thing as an "automatic failure" question on the test.  It was 25 questions, as I recall, and you could get up to five wrong.  It didn't matter which questions you got wrong.

To the best of my knowledge, I don't think we have automatic failure questions, but I think there should be some. If you have issues with a stop sign on the exam, you shouldn't be behind the wheel.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on January 31, 2020, 11:47:12 AM
In at least one of these projects,  traffic improvement was an objective as NYSDOT even took up an unbearable task of synchronizing traffic lights.  All 3 of them. Apparently, they gave up after realizing this is too much of engineering work to do. 

If driving straight thru all 3 lights, how many do you normally get stopped at?
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on January 31, 2020, 12:34:42 PM


Because of the way the local DMV office was arranged, you could watch people take their computerized exams while waiting in line. Some of the questions I think should have been an automatic failure if you got them wrong (basic sign and safety information).

When I got my DL back in the mid-90s, there was no such thing as an "automatic failure" question on the test.  It was 25 questions, as I recall, and you could get up to five wrong.  It didn't matter which questions you got wrong.

To the best of my knowledge, I don't think we have automatic failure questions, but I think there should be some. If you have issues with a stop sign on the exam, you shouldn't be behind the wheel.

OK, that may be, but that doesn't mean the tests have gotten easier.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 01, 2020, 08:14:17 AM


I don't see a lack of engineering skill in the U.S.
Two recent R1 projects - Washington ave ext and  7-787  interchange were rebuilt to original lane layout, if not to original blueprints. Some lane realignment was pretty obvious thing to do.I guess all engineering genius from R1 was absorbed by Exit3 project?

You can confirm there was no political and/or financial influence on those decisions? What was the intent of the project pavement rehab or reconstruction? Money may not have been available for the desirable reconstruction.
those were not minor pavement rehab, those were deep reconstructions. Lane realignment within existing footprint would be pretty straightforward no extra cost task.
In at least one of these projects,  traffic improvement was an objective as NYSDOT even took up an unbearable task of synchronizing traffic lights.  All 3 of them. Apparently, they gave up after realizing this is too much of engineering work to do. 

As for structural engineering.. I can only pray it works better than traffic engineering.
On a grand scheme of things,  professional growth comes with practice. If lane realignment becomes too much of a task to do, then what do you expect in terms of professional growth?
I still don't know what you're getting at.  Both projects are fine as is.

They are just so-so, ignoring traffic pattern changes over the decades, failing to use a chance to improve at a minimal cost (if any additional cost at all), and failing to reach some of published objectives - like synchronizing traffic lights.
Yes, it is a passing grade - work was performed using 20+ blueprints. WHo cares?
The only issue I'm aware of along there was the intersection with New Karner and there was no funding to deal with that completely (i.e., the backup turning right onto New Karner from Wash. Ave. Ext. WB).

In terms of traffic signal synchronization, I wonder if that made it into the design approval document.  I imagine fiscal constraints came into play there as well, especially given the large share of local funds put on the project.
And I saw - with my own eyes - how intersection by wallmart was rebuilt without a slightest though. And I saw multiple iterations of synchronizations attempts along Washington - to the point I was ready to pull over to explain folks what is being done wrong...  That was an epic try, I should say.

You weren't on the design squad and therefore I doubt that you know that the project went forward without thought and given my experience, I find the idea of a project to be designed without thought to be ludicrous. 

The Walmart intersection operates like it did before.  I don't see an engineering issue there.

I don't know what went on regarding the synchronization if it happened as you described.  If it was required in the contract, then it would have been taken care of.  A contractor cannot "just give up" on implementing a contract.

All I can say is that I haven't come across any examples of engineering incompetence very often -- if at all -- during my career.  I have personally witnessed engineers having to design less than the preferred treatments due to fiscal constraints very often, though (I might even say constantly).  So, if an engineer not in the know comes along after a project and whines about the treatment being inadequate, I would place my bet on fiscal constraints rather than lack of skill.  In fact, you might even say that a higher level of skill is needed to do the best you can with the available funds (as opposed to thinking there was an unlimited pot to draw from).

(personal opinion emphasized)
Welcome to upstate NY. You must be new here?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 01, 2020, 08:16:19 AM
In at least one of these projects,  traffic improvement was an objective as NYSDOT even took up an unbearable task of synchronizing traffic lights.  All 3 of them. Apparently, they gave up after realizing this is too much of engineering work to do. 

If driving straight thru all 3 lights, how many do you normally get stopped at?
all 3. I actually tried to look at the phase of a signal ahead and make it non-stop, but it _never_ worked for me.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on February 14, 2020, 10:36:23 AM
Driver in California drives straight through a roundabout at high speed and sends a big bolder flying.

VIDEO: Car goes airborne after crashing into roundabout in California
https://abc7chicago.com/5930794/

Car goes airborne after smashing into a roundabout
https://www.cnn.com/videos/us/2020/02/14/car-crash-airborne-long-beach-california-zw-orig.cnn
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on February 14, 2020, 11:29:16 AM
Driver in California drives straight through a roundabout at high speed and sends a big bolder flying.

VIDEO: Car goes airborne after crashing into roundabout in California
https://abc7chicago.com/5930794/

Car goes airborne after smashing into a roundabout
https://www.cnn.com/videos/us/2020/02/14/car-crash-airborne-long-beach-california-zw-orig.cnn

Tweet allows you to see the video without ads:

https://twitter.com/ABC7/status/1228087101381439488

More of a traffic circle than an actual roundabout.

Another job well done in getting a dangerous driver off the road before they could kill someone.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 14, 2020, 02:47:35 PM
Damn, they would have cleared the circle without those freakin' rocks!

It was built two years ago, according to Google Earth (can't find any online documents).

Another job well done in getting a dangerous driver off the road before they could kill someone.

Better no crashes at all.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on February 14, 2020, 03:32:51 PM
Damn, they would have cleared the circle without those freakin' rocks!

It was built two years ago, according to Google Earth (can't find any online documents).

Another job well done in getting a dangerous driver off the road before they could kill someone.

Better no crashes at all.

Even better if no one drove recklessly. They were bound to hit something or someone eventually.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on February 14, 2020, 04:20:47 PM
Damn, they would have cleared the circle without those freakin' rocks!

It was built two years ago, according to Google Earth (can't find any online documents).

Another job well done in getting a dangerous driver off the road before they could kill someone.

Better no crashes at all.

Aside from a mandatory breath analyzer in every cars, what's another solution?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 14, 2020, 05:12:09 PM
Better no crashes at all.
Aside from [clipped], what's another solution?
Even better if no one drove recklessly. They were bound to hit something or someone eventually.

So, if I get this correctly, the solution to crashes, is to cause the bad drivers to crash, learn their lesson (either by seriously injuring or killing themselves, and/or causing lots of property damage), and then...less crashes?

Seems kind of archaic. And a bit backwards, to be honest.

But there's a problem: bad drivers are born every day, they just don't hit the road for another 16 years. We need to do more to prevent bad driving to begin with, rather than ruining the life of someone whose judgement occasionally lapses. I guess this means either stricter training, more expensive licensing programs, cars that drive themselves, and importantly for us road-geeks: designing infrastructure to reduce the chance of collision.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 14, 2020, 05:15:20 PM
Better no crashes at all.
Aside from [clipped], what's another solution?
Even better if no one drove recklessly. They were bound to hit something or someone eventually.

So, if I get this correctly, the solution to crashes, is to cause the bad drivers to crash, learn their lesson (either by seriously injuring or killing themselves, and/or causing lots of property damage), and then...less crashes?

Seems kind of archaic. And a bit backwards, to be honest.

But there's a problem: bad drivers are born every day, they just don't hit the road for another 16 years. We need to do more to prevent bad driving to begin with, rather than ruining the life of someone whose judgement occasionally lapses. I guess this means either stricter training, more expensive licensing programs, cars that drive themselves, and importantly for us road-geeks: designing infrastructure to reduce the chance of collision.

Thinking about it... Such crashes are exact equivalent of T-bone on a traffic light. So one line less in roundabout advantages list?
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on February 14, 2020, 06:58:54 PM
Better no crashes at all.
Aside from [clipped], what's another solution?
Even better if no one drove recklessly. They were bound to hit something or someone eventually.

So, if I get this correctly, the solution to crashes, is to cause the bad drivers to crash, learn their lesson (either by seriously injuring or killing themselves, and/or causing lots of property damage), and then...less crashes?

Seems kind of archaic. And a bit backwards, to be honest.

No, you don't have it correctly, at least not based on what you selectively bolded. The context of my comment was exclusive of the (IRONY ALERT) traffic calming device. Someone going as fast as the person in the video is bound to hit something, especially when under the influence...another vehicle, tree, person taking their dog out to pee, etc. It unfortunately happens on perfectly straight roads without any obstacles such as a traffic circle (note: roundabouts DON'T have stop signs). I wasn't even beginning to imply that reckless drivers need to be taught a harsh lesson, rather it's the laws of probability: drive well in excess of the speed limit in an urban, tree and parked car-lined environment, chances are very high that the ending is not going to be good. Cut the reckless driving, and there would be a lot fewer crashes everywhere. What's shown in the video easily could have happened at a green-T intersection (https://goo.gl/maps/V6YsdQNbWFw3XKPr7) with similar results.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 14, 2020, 08:04:09 PM
Better no crashes at all.
Aside from [clipped], what's another solution?
Even better if no one drove recklessly. They were bound to hit something or someone eventually.

So, if I get this correctly, the solution to crashes, is to cause the bad drivers to crash, learn their lesson (either by seriously injuring or killing themselves, and/or causing lots of property damage), and then...less crashes?

Seems kind of archaic. And a bit backwards, to be honest.

No, you don't have it correctly, at least not based on what you selectively bolded. The context of my comment was exclusive of the (IRONY ALERT) traffic calming device. Someone going as fast as the person in the video is bound to hit something, especially when under the influence...another vehicle, tree, person taking their dog out to pee, etc. It unfortunately happens on perfectly straight roads without any obstacles such as a traffic circle (note: roundabouts DON'T have stop signs). I wasn't even beginning to imply that reckless drivers need to be taught a harsh lesson, rather it's the laws of probability: drive well in excess of the speed limit in an urban, tree and parked car-lined environment, chances are very high that the ending is not going to be good. Cut the reckless driving, and there would be a lot fewer crashes everywhere. What's shown in the video easily could have happened at a green-T intersection (https://goo.gl/maps/V6YsdQNbWFw3XKPr7) with similar results.

I agree that reckless driving needs to be "cut"...are circular intersections doing that?

Here:

Chance of successfully navigating a tight urban neighborhood street at high speeds while drunk: ~25%? (it's not 0%, but even 25% implies 3/4 of drivers will crash, which is probably high)
Chance of navigating straight through a circular junction at high speeds without issue: ~0% ("about", since there are mini-roundabouts that can be driven straight over, albeit it would be exceedingly uncomfortable, and a driver could lose control)
Chance of navigating straight through a regular intersection at high speeds without issue: >0% (probably pretty good, given how many intersections they've likely cleared already)
Chance of navigating straight through a T-intersection without issue: ~0% when approaching from the stem!

You're saying that, basically, there's a ton more ways that those drivers which are reckless in their behavior could cause harm to themselves and others. My point is that circular intersections are yet another thing on that list, and I don't see how that's necessarily benefitting anyone*.

*I'm actually fine with smaller traffic-calming circles...my comment is also exclusive of the circle at 4th/Daisy in Long Beach, and speaking more to larger circular intersections in general.
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on February 15, 2020, 08:48:41 AM
That's not a modern roundabout. This crash belongs in another thread.

Pixel 2

Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on February 15, 2020, 01:50:34 PM
Man, every drunk driver I've had the (dis)pleasure of getting a ride from has gone way under the speed limit.  Granted, I've seen drunk drivers going over the speed limit, but I've never personally been in the car with such a driver.



That's not a modern roundabout. This crash belongs in another thread.

Great point.  Discussion over.
Title: Re: Crash prone 'modern roundabouts'
Post by: DaBigE on February 15, 2020, 04:21:53 PM
Man, every drunk driver I've had the (dis)pleasure of getting a ride from has gone way under the speed limit.  Granted, I've seen drunk drivers going over the speed limit, but I've never personally been in the car with such a driver.

DUI is broad and doesn't always mean alcohol. The way the driver was stated as getting out of the car makes it sound more like they were on a drug trip.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 17, 2020, 07:21:46 PM
Would anyone know where to find data on the 106th St roundabout (https://www.google.com/maps/@39.9418203,-86.0182677,538m/data=!3m1!1e3) over I-69/IN-37 in Fishers?

It opened within the last couple years, and is definitely much larger than most roundabouts, as it spans across two overpasses:

(https://ucindy.com/wordpress/wp-content/uploads/2017/07/106th-and-I-69-Interchange-1-e1501179971984.jpg)
https://ucindy.com/project/i-69-and-106th-street-interchange/
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 17, 2020, 07:38:22 PM
Would anyone know where to find data on the 106th St roundabout (https://www.google.com/maps/@39.9418203,-86.0182677,538m/data=!3m1!1e3) over I-69/IN-37 in Fishers?

It opened within the last couple years, and is definitely much larger than most roundabouts, as it spans across two overpasses:

https://ucindy.com/project/i-69-and-106th-street-interchange/
I have no idea where the data can be, but have to say thet flying through the center of this one could have really interesting consequencies!
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 18, 2020, 03:59:16 AM
Would anyone know where to find data on the 106th St roundabout (https://www.google.com/maps/@39.9418203,-86.0182677,538m/data=!3m1!1e3) over I-69/IN-37 in Fishers?

It opened within the last couple years, and is definitely much larger than most roundabouts, as it spans across two overpasses:

https://ucindy.com/project/i-69-and-106th-street-interchange/
I have no idea where the data can be, but have to say thet flying through the center of this one could have really interesting consequencies!

Yeah, that's a good observation. With any luck, errant vehicles will come to a gentle stop after they slam into the jersey barrier. This is definitely one roundabout where a raised hill of vegetation is inadvisable, les you want cars flying over the freeway!
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on February 24, 2020, 09:24:47 PM

State web site for the project:  https://www.in.gov/indot/3399.htm

Youtube video:
Title: Re: Crash prone 'modern roundabouts'
Post by: skluth on March 14, 2020, 12:16:28 PM
I rather like this roundabout (https://benefits.transportation.org/kansas-city-divergabout-project/) which combines a DDI with a large, easy-to-navigate being built in my former home state of Missouri. I heard about it from MODOT's newsletter, but couldn't find more info on their website (which is not an easy site to find anything).

(https://benefits.transportation.org/wp-content/uploads/2020/02/kansas-city-divergabout-buti-small-1-.jpg)

If you'd like to subscribe to their newsletter (https://www.modot.org/express-lane).
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on March 14, 2020, 06:54:35 PM
I rather like this roundabout (https://benefits.transportation.org/kansas-city-divergabout-project/) which combines a DDI with a large, easy-to-navigate being built in my former home state of Missouri. I heard about it from MODOT's newsletter, but couldn't find more info on their website (which is not an easy site to find anything).

ttps://benefits.transportation.org/wp-content/uploads/2020/02/kansas-city-divergabout-buti-small-1-.jpg

If you'd like to subscribe to their newsletter (https://www.modot.org/express-lane).

All things considered, this seems like a great interchange. Single-lane roundabouts have a pretty decent record in terms of crashes, injuries, and fatalities, and DDIs have been found to be pretty effective too. If hardly anyone is exiting or entering the freeway, probably still not ideal because of the crossover. Still pretty slick.

I also see that another double-lane example (https://www.google.com/maps/@38.903261,-94.3768651,643m/data=!3m1!1e3) was built in Lee's Summit.
Title: Re: Crash prone 'modern roundabouts'
Post by: cpzilliacus on March 15, 2020, 11:46:26 AM
[WSJ.com has a paywall.  If you are blocked by the paywall, leave me a PM with your e-mail address and I will send you a copy of this article.]

Wall Street Journal: Car-Crash Mystery: Why Can’t Drivers Figure Out Roundabouts? (https://www.wsj.com/articles/car-crash-mystery-why-cant-drivers-figure-out-roundabouts-11584191556?mod=searchresults&page=1&pos=1)

Quote
City planners and engineers are stumped over why so many drivers can’t handle something as simple as a roundabout.

Quote
Roundabouts have proliferated around the U.S. in recent years, arriving in some areas of the Midwest and West for the first time. Yet even years after some are installed, driver confusion persists. And with confusion comes fender-benders.

Quote
Authorities have boosted public education, tweaked signs and modified roadway designs in search of solutions. The federal government is leading a study on drivers’ failure to yield to traffic when entering two-lane roundabouts, a major cause of collisions. State transportation departments from Washington to New York are helping fund the research.
Title: Re: Crash prone 'modern roundabouts'
Post by: Occidental Tourist on April 13, 2020, 05:55:03 PM
The Los Alamitos (Long Beach, CA) Traffic Circle, which was a free flowing rotary with a three entry lanes and a couple of dedicated rights, has been changed to a roundabout with two entry lanes and lane controls.

I'll try to get you some pics when I get a chance.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 15, 2020, 08:00:08 AM
This guy got some serious airtime.  Conveniently, the driver landed in a graveyard...

Car Slams Into Roundabout, Flies Through the Air, Lands in a Graveyard
https://interestingengineering.com/video/car-slams-into-roundabout-flies-through-the-air-lands-in-a-graveyard

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 15, 2020, 08:50:09 AM
In at least one of these projects,  traffic improvement was an objective as NYSDOT even took up an unbearable task of synchronizing traffic lights.  All 3 of them. Apparently, they gave up after realizing this is too much of engineering work to do. 

If driving straight thru all 3 lights, how many do you normally get stopped at?
all 3. I actually tried to look at the phase of a signal ahead and make it non-stop, but it _never_ worked for me.

If NYSDOT has difficulty synchronizing 3 lights I would hate to see how well they would do retiming 124 traffic signals.  In Detroit it’s possible to drive 40 miles and over 100 traffic signals without getting stopped at a red light.  BTW, since this video was taken, the signals along Woodward Avenue were retimed making signal progression even smoother than before.


^It's impossible to see this type of travel time run along a roundabout corridor.  Imagine driving through 124 roundabouts as opposed to 124 traffic signals… that would lead to 124 guaranteed instances of delay (driver drops down to 15-20 mph 124 times to navigate the roundabouts as opposed to cruising 45-50 mph through 124 consecutive green lights).  Hell, after navigating through 124 roundabouts the driver’s brakes would be smoldering! 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 16, 2020, 08:23:33 AM
Hilliard reports roundabout modifications have reduced accidents
https://www.thisweeknews.com/news/20200410/hilliard-reports-roundabout-modifications-have-reduced-accidents

The city of Hilliard reports that roundabout modifications made last summer have helped reduce accidents.  This could be big as the modifications did not include reducing the capacity of the roundabout by eliminating circulating lanes inside the roundabout (which at other complex roundabouts has been the main way at seeing big reduction in crashes).  The main modification made at the 2x1 Main and Scioto Darby roundabout was converting the central island from a circle to an oval (and not with just pavement markings but with raised curbing). 
(https://i.imgur.com/G37iwCd.png)

The modifications made at the 2x2 Main and Cemetery roundabout included raised crosswalks, changes to lane markings, overhead signs and the placement of signs with red LEDs in the central island of the roundabout that indicates drivers must yield to both lanes of traffic before entering the roundabout.  In the picture below you can see they used double dashed white lines and an additional thru arrow at the exiting leg of the roundabout to help reiterate to drivers that a “straight arrow”  means you are exiting the roundabout and not continuing around the circle. 
(https://i.imgur.com/UranRY2.png)

Letty Schamp who is the Deputy City Engineer for the City of Hilliard put together a great presentation that highlights the lessons learned at Hilliard roundabouts.  It highlights the fact that 2x2 roundabouts are very differently from 2x1 roundabouts and that a better job of differentiating between the two needs to be done.  It highlights the ONGOING crash problem that exists at these complex Hilliard roundabouts (and just wishing away crashes doesn't always work).  It highlights the fact that drivers can interpret signage and lane markings very differently from each other causing confusion.  It highlights the fact that engineers lose credibility when they disregard huge increases in PDO crashes and focus almost entirely on the reductions in injury crashes (even when the reductions in injury crashes at some of these complex roundabouts may be quite low).  To their credit the engineers in Hilliard understand the problems associated with complex 2x2 roundabouts and are trying to improve them.

12 Roundabouts in 12 Years:  Lessons Learned
http://www.dot.state.oh.us/engineering/OTEC/2018_OTEC_Presentation/Schamp_09.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 16, 2020, 02:28:13 PM
I appreciate Mr Schamp's sense of humor. That was quite a funny presentation!

I wrote a big paper on roundabouts for my last quarter at school. I wasn't required to go very deep into the research, but I focus more on how we changed from circles, like Dupont Circle, into rotaries (like those in Massachusetts), before we got into the early "modern" roundabouts along I-70 in Colorado (particularly those at the Vail junction).

One thing I noticed was that the early modern roundabouts were very British. Short of driving on the left, they were basically just flipped versions of their roundabouts. This extended to basic practices like not having lane lines through the circle, or flaring the entry roadway from one to two or three lanes to maximize throughput at the circle. The practice of "flaring" seems to have died down a bit.

I bring this up because, in the presentation that Mr Schamp gave, he talks about the "honeymoon" years with their early roundabouts, particularly those along Britton Parkway (oddly enough, a roundabout corridor in Lacey, WA (https://www.google.com/maps/@47.0681286,-122.7798654,16.25z) as well). He doesn't go into great detail about what exactly he means by this, but I think it's in reference to them just building a bunch of roundabouts, several quite large examples, and not really paying attention to crash data (with the child-rearing years being where they started to notice serious issues). I wouldn't want to suggest that those early roundabouts were somehow superior to the modern FHWA-compliant designs, but what changed at roundabouts, particularly those designed prior to 2009, to those that we we've seen built since the current MUTCD was released? As far as I can tell, the discussion around crashes has only come up majorly in the last ten years, despite 2x2 modern roundabouts having existed in sizeable numbers since the mid-90s.

When I look at some of the older notable roundabouts:

* Long Beach (Los Alamitos) Roundabout: no major changes after major modification in mid-90s.
* Vail roundabouts: some lane lines added
* Avon roundabouts: one entry (of dozens) narrowed; some lane lines but they frequent disappear
* Summerlin, NV (Town Center Dr): right lanes changed to right-only
* Lacey, WA (Britton/Marvin/Willamette): slip lane added, exit lines added (notable because it was in this early video (https://youtu.be/-olqiG42Ud4)).

So there have been some changes at these roundabouts, but not really anything major. The newest of these (Lacey, WA) was constructed eighteen years ago; collectively, they've experienced well over 100 years of crash data.

I guess, in short, it's funny how some of the roundabouts that have seen the most number of changes seem to have been those built since 2009.
Title: Re: Crash prone 'modern roundabouts'
Post by: Occidental Tourist on April 21, 2020, 06:07:23 PM
Here are some pictures of the new lane controls at the Los Alamitos (Long Beach, CA) Traffic Circle.  We're going to go counterclockwise starting at the 3 o'clock (east) side of the Traffic Circle.

(https://i.imgur.com/YL1Q32s.jpg)
Looking northwest toward the Lakewood Blvd entrance/exit.  Where the roundabout had been effectively three lanes wide and unmarked, striping at the edge and painted lane controls have reduced this portion to two lanes. Three entrance lanes from Los Coyotes Diagonal (right foreground) have been reduced to two by striping a median between the inside and outside entrance lanes.


(https://i.imgur.com/Gh51MU5.jpg)
Approach and new signage for the Lakewood Blvd entrance to the roundabout (now at 12 o'clock looking south).  The dedicated right turn lane from Lakewood Blvd to PCH westbound has been kept.  Not pictured are the flexible stakes that have been added to this dedicated right turn lane to delineate it from the rest of the roundabout.  Prior to this, this dedicated right turn lane was delineated from the rest of the roundabout by just a solid white line.


(https://i.imgur.com/DGq0VcW.jpg)
Lakewood Blvd approach again.  Two entrance lanes and a dedicated right turn lane have been reduced to two entrance lanes through striping.


(https://i.imgur.com/hSiii2K.jpg)
New signage and striping for the eastbound PCH entrance (9 o'clock looking east).

(https://i.imgur.com/eFXMP9b.jpg)
At the eastbound PCH entrance looking north towards Lakewood Blvd.  An asphalt curb/truck apron has been installed here along with pavement striping to reduce the roundabout to one lane here.  This is the only point where the roundabout is one lane.  All other sections are two lanes wide.

(https://i.imgur.com/Mn0coI8.jpg)
(At 6 o'clock now) Looking northeast toward the Los Coyotes Diagonal in the distance.  The dedicated right turn lane from PCH eastbound to PCH southeastbound has been kept.  Flexible stakes have been added to separate the dedicated lane from the remainder of the roundabout.  Previously, only a solid white line delineated the dedicated right turn lane.  On the east side of the roundabout, an asphalt curb/truck apron has been added to the inside of the roundabout to reduce the overall width to two lanes.


(https://i.imgur.com/Q2q5f9q.jpg)
Returning to the east side of the roundabout again (3 o'clock again).  Obviously, not all entrances and exits are uniform.  But here's an odd pavement lane control between the PCH northwestbound entrance and the Los Coyotes Diagonal exit.  I don't think the arrows in the right lane are accurate (two of the arrows are superfluous).  This lane control probably should have been painted back in the right entrance lane from northwest bound PCH (offscreen left). A similar arrow (not pictured) also has been painted on the right side near the Lakewood Blvd exit.

(https://i.imgur.com/2VZoUnM.jpg)
Still on the east side, here's entrance from northwestbound PCH to the roundabout.  It seems to be the only entrance from which the righthand lane has to cross over two exit lanes to enter the roundabout. 

Now that the Los Alamitos Traffic Circle has gone from laissez faire to having lane controls, we'll have to see how the accident rate at it fares.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on May 17, 2020, 07:37:07 PM
Here are some pictures of the new lane controls at the Los Alamitos (Long Beach, CA) Traffic Circle.  We're going to go counterclockwise starting at the 3 o'clock (east) side of the Traffic Circle.

I'm not sure how I missed this post.

I was just thinking the other day that the Los Alamitos Circle had not been modified from its original configuration since it was updated in 1994. That update in 1994 made it match British standards, with lane-control arrows before the roundabout but without lane markings. But my impression was that it had not been modified since because crashes hadn't become a hysterical issue like at other roundabouts. Part of me was contributing this to the vagueness of the circulating roadway (no lane lines might mean that drivers are a bit less careless, although I don't know this to be fact). I guess it's a bit disappointing to see that it has been modified, since it was one of the few unmodified 90s-era modern roundabouts; could be that those along I-70 in the Rockies are the last of this dying breed.

Part of me genuinely thinks crashes will go up, since all they've done is paint it to look like the numerous other multi-lane modern roundabouts that almost all universally perform poorly in terms of overall crashes. But I guess only time will tell.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 29, 2020, 07:07:12 PM
The most crash prone intersection in Michigan in 2019 was the 18 ½ Mile Road and Van Dyke Ave roundabout which saw 229 crashes (a 62% increase in crashes from the year before).  I think 229 annual crashes at a roundabout is a record for this thread

Michigan’s Most Dangerous Intersections in 2019
https://www.michiganautolaw.com/blog/2020/06/23/michigans-most-dangerous-intersections-2019/
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 29, 2020, 10:47:56 PM
The most crash prone intersection in Michigan in 2019 was the 18 ½ Mile Road and Van Dyke Ave roundabout which saw 229 crashes (a 62% increase in crashes from the year before).  I think 229 annual crashes at a roundabout is a record for this thread

Michigan’s Most Dangerous Intersections in 2019
https://www.michiganautolaw.com/blog/2020/06/23/michigans-most-dangerous-intersections-2019/

Pretty good proof that old roundabouts don't necessarily improve in time.
Title: Re: Crash prone 'modern roundabouts'
Post by: BrynM65 on June 30, 2020, 09:32:33 AM
I've not read the entire 99 pages so please forgive me if I am retreading old ground. I'll describe for driving on the right hand side of the road.

British style multi-lane roundabouts cause us no end of safety problems either due to high circulating speeds and low gap availability to merge into. This means entering traffic that has spent a while at the yield line tends to take a gamble and cut in front of others. The traditional two bridges over a freeway roundabouts with a straight section linked by curves are notoriously prone to this and as a result often end up under part time or complete signal control. This gets rid of the entry problems but at the cost of increasing delays on all arms.

The main driver of safety at any large roundabout is to ensure drivers are in the correct lane before entering, and that the lane markings direct drivers to their desired exit with no lane change necessary. This is not always achievable because you may need to move traffic towards the central island in a "spiral" layout but these moves to the left have fewer conflict potentials than moves across to the right.

DDIs and other advanced signal configurations are in my view much better than the traditional two bridge roundabouts. Minimise the conflict points and ensure speeds are at an appropriate level and that's how you reduce collisions.

The Michigan examples seem to have some design flaws but they could be partially fixed relatively cheaply by introducing visibility screens to prevent "reading through" and forcing traffic to yield as a consequence.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 30, 2020, 10:39:02 AM
I've not read the entire 99 pages so please forgive me if I am retreading old ground. I'll describe for driving on the right hand side of the road.

British style multi-lane roundabouts cause us no end of safety problems either due to high circulating speeds and low gap availability to merge into. This means entering traffic that has spent a while at the yield line tends to take a gamble and cut in front of others. The traditional two bridges over a freeway roundabouts with a straight section linked by curves are notoriously prone to this and as a result often end up under part time or complete signal control. This gets rid of the entry problems but at the cost of increasing delays on all arms.

The main driver of safety at any large roundabout is to ensure drivers are in the correct lane before entering, and that the lane markings direct drivers to their desired exit with no lane change necessary. This is not always achievable because you may need to move traffic towards the central island in a "spiral" layout but these moves to the left have fewer conflict potentials than moves across to the right.

DDIs and other advanced signal configurations are in my view much better than the traditional two bridge roundabouts. Minimise the conflict points and ensure speeds are at an appropriate level and that's how you reduce collisions.

The Michigan examples seem to have some design flaws but they could be partially fixed relatively cheaply by introducing visibility screens to prevent "reading through" and forcing traffic to yield as a consequence.
I think you're going into too fine details. Root cause is a serious lack of understanding of when roundabouts can work and where they cannot.
They are definitely oversold in US, with lots of wishful but uneducated publications. As a result, a lot of roundabouts are just not working anywhere close to expectations.
Unlike SPUI, where base concept of "more pavement for more throughput" works reasonably well and pretty intuitive, its not really the case with roundabouts.
 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 30, 2020, 11:51:33 AM
The Michigan examples seem to have some design flaws but they could be partially fixed relatively cheaply by introducing visibility screens to prevent "reading through" and forcing traffic to yield as a consequence.

They added visibility screens along the splitter islands of the M-5 & Pontiac Trail roundabout several years ago but it didn't help reduce crashes.  In fact the 6 months before the screens were added had the exact same number of crashes as the 6 months after.  Even with it being nearly a decade old, there seems to be more crashes at the roundabout than ever before (with 161 crashes in 2019 which is 23 more crashes than the 138 crashes it had in 2018).   
Title: Re: Crash prone 'modern roundabouts'
Post by: Sani on June 30, 2020, 01:37:12 PM
Here are some pictures of the new lane controls at the Los Alamitos (Long Beach, CA) Traffic Circle.  We're going to go counterclockwise starting at the 3 o'clock (east) side of the Traffic Circle.

I'm not sure how I missed this post.

I was just thinking the other day that the Los Alamitos Circle had not been modified from its original configuration since it was updated in 1994. That update in 1994 made it match British standards, with lane-control arrows before the roundabout but without lane markings. But my impression was that it had not been modified since because crashes hadn't become a hysterical issue like at other roundabouts. Part of me was contributing this to the vagueness of the circulating roadway (no lane lines might mean that drivers are a bit less careless, although I don't know this to be fact). I guess it's a bit disappointing to see that it has been modified, since it was one of the few unmodified 90s-era modern roundabouts; could be that those along I-70 in the Rockies are the last of this dying breed.

Part of me genuinely thinks crashes will go up, since all they've done is paint it to look like the numerous other multi-lane modern roundabouts that almost all universally perform poorly in terms of overall crashes. But I guess only time will tell.

As an insurance adjuster who had to determine liability on multiple crashes in this traffic circle and, more often than not, went 50/50 on liability for lack of any way to determine who encroached on whose lane, I'm glad there are finally marked lanes inside the circle.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 30, 2020, 02:57:32 PM
As an insurance adjuster who had to determine liability on multiple crashes in this traffic circle and, more often than not, went 50/50 on liability for lack of any way to determine who encroached on whose lane, I'm glad there are finally marked lanes inside the circle.

I don't see why it makes a difference to you. This entire thread is evidence that crashes are an issue at multi-lane roundabouts, so you're still going to be dealing with crashes.

It might make your job easier since liability is more obvious, but I think that misses the bigger issue at hand here which is that no amount of markings or signs seems to improve crash rates.
Title: Re: Crash prone 'modern roundabouts'
Post by: Ketchup99 on June 30, 2020, 11:57:18 PM
Roundabouts are good in certain situations, but not in others. A roundabout very effectively slows down traffic, which can be a blessing and a curse. On arterials, no. Roundabouts don't belong on arterials, in almost any situation. Timed traffic lights work lots better, and are also better at keeping traffic at a good speed - if the limit is 50, the only way to cruise down the road without stopping is at 50. That said, arterials should have as few intersections as possible anyway.

Roundabouts are good on residential collectors. For instance, this (https://www.google.com/maps/@40.7922318,-77.8464877,3a,75y,214.54h,85.34t/data=!3m7!1e1!3m5!1sI1arP7dObZPllnDcOJ2fHA!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3DI1arP7dObZPllnDcOJ2fHA%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D336.73547%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656) road in State College goes on for about three miles. Limit is 25 because it's a rather residential area, but when using it the way I do (I have to use the entire thing routinely), it's easy to watch the needle creep past 25, 30, 35. It just doesn't have the feel of the residential road that it largely is. Adding roundabouts at lots of intersections would definitely help keep speeds down.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 01, 2020, 10:50:14 AM

Driving through a roundabout is like playing the arcade game "Frogger".  The problem is some people suck at Frogger and can't judge gaps in traffic.  When you have 50k people a day driving through a roundabout, that's like 50k individual games of Frogger taking place and some people won't make it past the first level.  Here is an arterial of State Street & Ellsworth roundabout in Ann Arbor which was the 5th most dangerous intersection in Michigan with 154 crashes last year.  Look at all those frogs (cars) having to judge gaps in traffic.

(https://i.imgur.com/i6PMejt.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: BrynM65 on July 01, 2020, 11:03:23 AM
The entry angles also force you to have to look sharply over your shoulder to the left more than they should looking at that aerial again. This probably accounts for a lot of failure to see type collisions because that kind of posture is just uncomfortable so people don't do it.

The Ann Arbor example above has the problems I described that plague British roundabouts - including the two lane exits which, given the road reduces to single lane on three exit arms is not required - this is a hangover from the signals where you have the ahead lanes merge after the intersection because of the way platoons are sent out from a green.

I wonder if striping those exits down to a single lane and introducing a proper spiral lane system might help create better gaps.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 01, 2020, 05:54:37 PM
The Ann Arbor example above has the problems I described that plague British roundabouts - including the two lane exits which, given the road reduces to single lane on three exit arms is not required - this is a hangover from the signals where you have the ahead lanes merge after the intersection because of the way platoons are sent out from a green.

To be clear, that practice exists specifically because of the British practice at the time. Many of our first roundabouts were designed according to British standards, or by actual British roundabout designers (such as Frank Blackmore from the TRB), including such things as widened entry and exit points relative to the approach roads, and minimal or no lane markings. We largely went more with the Australian roundabout guidelines when all was said and done, the guidelines became part of the MUTCD, but those traits are also seen in Australian designs.

The entry angles also force you to have to look sharply over your shoulder to the left more than they should looking at that aerial again. This probably accounts for a lot of failure to see type collisions because that kind of posture is just uncomfortable so people don't do it.

This is an issue that I don't believe is considered often enough. Roundabout design guidelines suggest that, to avoid path overlap, the crossover points should minimize the amount of "turning" input required by drivers; basically, the entry and exits should be straight on, with the only curving being once you're inside the roundabout, or the approach and exit (to "line up" with the crossover). This seems logical, but it does seem to have the negative effect of making the entries quite sharp, and multi-lane entries can be difficult if you're the outside car.
Title: Re: Crash prone 'modern roundabouts'
Post by: Sani on July 02, 2020, 12:20:03 AM
As an insurance adjuster who had to determine liability on multiple crashes in this traffic circle and, more often than not, went 50/50 on liability for lack of any way to determine who encroached on whose lane, I'm glad there are finally marked lanes inside the circle.

I don't see why it makes a difference to you. This entire thread is evidence that crashes are an issue at multi-lane roundabouts, so you're still going to be dealing with crashes.

It might make your job easier since liability is more obvious, but I think that misses the bigger issue at hand here which is that no amount of markings or signs seems to improve crash rates.
Right, my only point was that it makes liability easier to determine. I was being a bit glib.

I had at least one claim where two cars, side by side, entered the circle at the same time and tried to take the same multi-lane exit and still, somehow, managed to collide. At least lane markings will make it a bit easier for those folks to tell which lane they should be in, even if they don't know where the edges of their vehicles are.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on July 02, 2020, 10:00:17 AM

The entry angles also force you to have to look sharply over your shoulder to the left more than they should looking at that aerial again. This probably accounts for a lot of failure to see type collisions because that kind of posture is just uncomfortable so people don't do it.

This is an issue that I don't believe is considered often enough. Roundabout design guidelines suggest that, to avoid path overlap, the crossover points should minimize the amount of "turning" input required by drivers; basically, the entry and exits should be straight on, with the only curving being once you're inside the roundabout, or the approach and exit (to "line up" with the crossover). This seems logical, but it does seem to have the negative effect of making the entries quite sharp, and multi-lane entries can be difficult if you're the outside car.

The deflected entry is also intended to slow drivers down.  They're more likely to enter a roundabout at too-high speeds if the entry is more of a straight line.  The exit is more of a straight shot because that's not a factor upon exiting.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 02, 2020, 12:40:14 PM
The entry angles also force you to have to look sharply over your shoulder to the left more than they should looking at that aerial again. This probably accounts for a lot of failure to see type collisions because that kind of posture is just uncomfortable so people don't do it.

This is an issue that I don't believe is considered often enough. Roundabout design guidelines suggest that, to avoid path overlap, the crossover points should minimize the amount of "turning" input required by drivers; basically, the entry and exits should be straight on, with the only curving being once you're inside the roundabout, or the approach and exit (to "line up" with the crossover). This seems logical, but it does seem to have the negative effect of making the entries quite sharp, and multi-lane entries can be difficult if you're the outside car.

The deflected entry is also intended to slow drivers down.  They're more likely to enter a roundabout at too-high speeds if the entry is more of a straight line.  The exit is more of a straight shot because that's not a factor upon exiting.

I know what the purpose of the curvature is. I'm say it's ill-advised, and/or had unintended consequences. The strong curvature and desired entry angle can, unintentionally, makes it difficult to see to the left (mostly for the outside lane, but sometimes inside too).
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on July 02, 2020, 12:44:01 PM
it's ill-advised, and/or had unintended consequences.

I suspect a combination of the two.  It's all but impossible for me to believe nobody considered that it's harder to look to the right when the angle is thus deflected.  But it's easy for me to believe it was determined that such wasn't a big deal.
Title: Re: Crash prone 'modern roundabouts'
Post by: BrynM65 on July 02, 2020, 01:04:36 PM
it's ill-advised, and/or had unintended consequences.

I suspect a combination of the two.  It's all but impossible for me to believe nobody considered that it's harder to look to the right when the angle is thus deflected.  But it's easy for me to believe it was determined that such wasn't a big deal.

One of my roles is road safety auditing and it's frightening how we often as engineers ignore the basics, because to us it's 'obvious'. Average drivers don't think like engineers, which is why there's often inexplicable resistance to sensible engineering concepts like DDIs because they look like a complex monster that makes you drive on the wrong side despite being actually ten times more efficient than a standard diamond.

A lot of 'fear' of roundabouts is the same thing I think - only an engineer would make you turn right to turn left (see also the humble cloverleaf interchange).
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on July 02, 2020, 01:34:05 PM
DDIs ... actually ten times more efficient than a standard diamond.

Uh oh.  Now you've asked for it (https://www.aaroads.com/forum/index.php?topic=15118.msg2053007#msg2053007).
Title: Re: Crash prone 'modern roundabouts'
Post by: BrynM65 on July 02, 2020, 01:40:05 PM
DDIs ... actually ten times more efficient than a standard diamond.

Uh oh.  Now you've asked for it (https://www.aaroads.com/forum/index.php?topic=15118.msg2053007#msg2053007).

They're not infallible; intersection choice is always location dependent - another thing us engineers screw up. No two intersections are the same after all.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on July 02, 2020, 01:46:44 PM
It's just that, in tradephoric's darling thread, you brought up another topic he's passionate about:  the comparative performance of DDIs.  Hopefully this won't now devolve into a discussion about the ParClo B4 and/or signal progression in Detroit.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 02, 2020, 02:44:51 PM
it's ill-advised, and/or had unintended consequences.

I suspect a combination of the two.  It's all but impossible for me to believe nobody considered that it's harder to look to the right when the angle is thus deflected.  But it's easy for me to believe it was determined that such wasn't a big deal.

One of my roles is road safety auditing and it's frightening how we often as engineers ignore the basics, because to us it's 'obvious'. Average drivers don't think like engineers, which is why there's often inexplicable resistance to sensible engineering concepts like DDIs because they look like a complex monster that makes you drive on the wrong side despite being actually ten times more efficient than a standard diamond.

A lot of 'fear' of roundabouts is the same thing I think - only an engineer would make you turn right to turn left (see also the humble cloverleaf interchange).
I would say that as long as this remains the selling picture for roundabouts, I would still assume that engineers do not simply ignore, but plainly don't understand basics:
(https://nextstl.com/wp-content/uploads/9577583353_3c13fe8144_o-1.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on July 02, 2020, 02:57:46 PM
basics

Such as drawing to scale.

A whole lot of those conflict points in the second picture could be collapsed into just a few dots.

And that's not even considering the fact that it considers points at which vehicle paths diverge to be points of conflict.  I estimate that the number of red dots could realistically be reduced by half, and the yellow squares by one third.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on July 02, 2020, 03:13:10 PM
(https://nextstl.com/wp-content/uploads/9577583353_3c13fe8144_o-1.jpg)

Yeah, I don't think so.

If I'm guessing, that graphic is comparing a 1 lane-per-direction roundabout with a 3 lane-per direction intersection.

Even within a roundabout, I'd say there's really two conflict points between each leg - where a vehicle enters the roundabout and where the vehicle exits the roundabout.  The point between the two areas would actually be the safest point.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 02, 2020, 03:47:27 PM
(https://nextstl.com/wp-content/uploads/9577583353_3c13fe8144_o-1.jpg)

Yeah, I don't think so.

If I'm guessing, that graphic is comparing a 1 lane-per-direction roundabout with a 3 lane-per direction intersection.

Even within a roundabout, I'd say there's really two conflict points between each leg - where a vehicle enters the roundabout and where the vehicle exits the roundabout.  The point between the two areas would actually be the safest point.

Thing is, even then that is irrelevant. First question to ask is:  why number of conflict points is a figure of merit to begin with?
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on July 02, 2020, 04:00:11 PM
The FHWA is certainly under the impression that reducing conflict points is a good thing.  What I can't find, however, is why they think so.

Quote from: Intersection Safety - Safety | FHWA
The success of innovative intersection designs begins with reducing the number and severity of conflict points — locations where user paths coincide.

Quote from: Chapter 10 - Signalized Intersections:  Informational Guide | FHWA
The common element in each treatment is the reduction in conflict points at the intersection, which provides safety and operational benefits by reducing the number of phases and conflicting volume at a single location.

Quote from: Access Management in the Vicinity of Intersections | FHWA
It is desirable to minimize the number of conflict points created with existing and future driveways since more conflict points increase the risk of a crash occurring.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 02, 2020, 04:18:25 PM
The FHWA is certainly under the impression that reducing conflict points is a good thing.  What I can't find, however, is why they think so.

Quote from: Intersection Safety - Safety | FHWA
The success of innovative intersection designs begins with reducing the number and severity of conflict points — locations where user paths coincide.

Quote from: Chapter 10 - Signalized Intersections:  Informational Guide | FHWA
The common element in each treatment is the reduction in conflict points at the intersection, which provides safety and operational benefits by reducing the number of phases and conflicting volume at a single location.

Quote from: Access Management in the Vicinity of Intersections | FHWA
It is desirable to minimize the number of conflict points created with existing and future driveways since more conflict points increase the risk of a crash occurring.
Because.. khmmm it is called education, you know... Imagine a grid with multiple parallel streets. Would compressing multiple parallel into one make things safer? Fewer conflict points, thats for sure
Title: Re: Crash prone 'modern roundabouts'
Post by: sparker on July 03, 2020, 02:25:31 AM
Good old AASHTO Weekly; they're reprinting a bit of roundabout flack:

https://aashtojournal.org/2020/07/02/trb-analysis-illustrates-benefits-of-roundabout-intersections/

One of the primary points raised is that there is an inherent reduction of overall speed when roundabouts are deployed.  All well and good in dense urban areas where general speed reduction might be beneficial -- but that concept isn't terribly portable to rural highways.  But it seems that some planners -- particularly at the state level -- seem to have posited a "zero-sum" approach to such things; that to provide certain benefits to the overall populace the methods employed to do so must be at the detriment of the driving portion of the public.  A "one size fits all" curriculum doesn't really address underlying problems; as I've averred previously, this is what's known as the "garbage can" policy methodology -- apply one's favored "solution" to as many problems as possible regardless of appropriateness.  Too much of that sort of BS can backfire against transportation agencies in terms of both operation and appropriations, particularly if repeated complaints are lodged by legislative constituents. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 03, 2020, 06:58:55 PM
(https://i.imgur.com/U8peMBjl.jpg)

I'm a fan of the "partial" Parclo A4 roundabout.  It has only one vehicle-to-vehicle conflict point compared to four at a more standard interchange roundabout (assume each example below is a "single lane" roundabout when calculating the number of conflict points).  I like the fact that all traffic entering the freeway doesn't have to travel through a roundabout and it's a simple design that limits the number of vehicle-to-vehicle conflicts.


^Through traffic along the arterial should never have to yield meaning that platooning can largely stay in tact in regards to good signal progression (arterial traffic will have to slow down to 25 mph to navigate the "partial" roundabout but only the off ramp traffic actually yields). 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 04, 2020, 02:20:26 PM
^^^
So what benefits are there exactly, as compared to a standard left-hand "add lane" merge?

I suppose the curve makes it so that traffic slows down, allowing the off-ramp more chances to go, although that slowing could cause cars to "pile up" approaching the curve, making it just as hard to find gaps (especially if the approach road is a relatively straight, wide, high-speed arterial with heavy traffic).

There is a left-hand merge A4 (https://www.google.com/maps/@49.18261,-122.7343768,180m/data=!3m1!1e3) in Surrey, BC seems to work pretty well.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 04, 2020, 02:55:44 PM
^^^
So what benefits are there exactly, as compared to a standard left-hand "add lane" merge?

I suppose the curve makes it so that traffic slows down, allowing the off-ramp more chances to go, although that slowing could cause cars to "pile up" approaching the curve, making it just as hard to find gaps (especially if the approach road is a relatively straight, wide, high-speed arterial with heavy traffic).

There is a left-hand merge A4 (https://www.google.com/maps/@49.18261,-122.7343768,180m/data=!3m1!1e3) in Surrey, BC seems to work pretty well.
I can see exit roundabout being a thing in certain suburban bedroom communities - it deprioritizes arterial through traffic compared to highway entry/exit traffic. May backfire once local area develops a bit and meaningful local traffic appears.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 05, 2020, 12:59:07 PM
^^^
So what benefits are there exactly, as compared to a standard left-hand "add lane" merge?

I suppose the curve makes it so that traffic slows down, allowing the off-ramp more chances to go, although that slowing could cause cars to "pile up" approaching the curve, making it just as hard to find gaps (especially if the approach road is a relatively straight, wide, high-speed arterial with heavy traffic).

There is a left-hand merge A4 (https://www.google.com/maps/@49.18261,-122.7343768,180m/data=!3m1!1e3) in Surrey, BC seems to work pretty well.
I can see exit roundabout being a thing in certain suburban bedroom communities - it deprioritizes arterial through traffic compared to highway entry/exit traffic. May backfire once local area develops a bit and meaningful local traffic appears.

That would be my worry. Feels to me that it would eventually have to be signalized. Or maybe the non-yield entry having a signal/meter to reduce the amount of traffic that "left" turning off-ramp traffic would have to worry about.

Still, my gut tells me that a regular left-side add-lane would be better, assuming there's enough ROW. It could be a yield at first, same as the roundabout, and then signalized in the future.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 05, 2020, 01:59:37 PM
I really like that left-hand merge A4 you linked and its questionable if that "partial" roundabout design would be in any way superior.  I'm just theorizing that a roundabout with the fewest number of conflict points would also have one of the lowest crash rates compared to other standard roundabouts.  It would be interesting if a few "partial" interchange roundabouts existed if nothing else just to research how safe they may be.
Title: Re: Crash prone 'modern roundabouts'
Post by: ErmineNotyours on August 10, 2020, 09:32:51 PM
I wonder how crash-prone this roundabout is.

https://twitter.com/Streetfilms/status/1023739247826632705

Can we find any pedestrian-only roundabouts?

Of course New Jersey would have a bike lane with a jughandle:
(https://i.imgur.com/MkSQWNf.jpg)

Add to the list the intersection of the Woodland Trail and the Chehalis Western Trail in Lacey, Washington.  Google Satellite View (https://www.google.com/maps/@47.0392013,-122.839351,65m/data=!3m1!1e3).  It is signed with yield and roundabout arrows.  There were so many homeless people around that I didn't want to violate anyone's privacy by taking a picture, and it was worse when I came back at night.
Title: Re: Crash prone 'modern roundabouts'
Post by: plain on August 16, 2020, 11:02:04 PM
I wonder how crash-prone this roundabout is.

https://twitter.com/Streetfilms/status/1023739247826632705

Can we find any pedestrian-only roundabouts?

Of course New Jersey would have a bike lane with a jughandle:
(https://i.imgur.com/MkSQWNf.jpg)

Add to the list the intersection of the Woodland Trail and the Chehalis Western Trail in Lacey, Washington.  Google Satellite View (https://www.google.com/maps/@47.0392013,-122.839351,65m/data=!3m1!1e3).  It is signed with yield and roundabout arrows.  There were so many homeless people around that I didn't want to violate anyone's privacy by taking a picture, and it was worse when I came back at night.

I'm glad that post got bumped. Has anyone found out where in NJ that bike lane jughandle is at yet?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 02, 2020, 11:29:35 AM
Some interesting comments from Washtenaw County Road Commission engineer Mark McCulloch who was behind the very first roundabout cited on this thread: the State and Ellsworth roundabout in Ann Arbor. 

Quote
"I never once imagined in my wildest imagination when we built it that we were going to have the number of fender bender noninjury crashes increase,"

Quote
"We as engineers thought we are getting such great results with single lane roundabouts when it came to crash statistics and capacity analysis that we just thought automatically it was going to translate over into the multilane roundabouts,"

Quote
"None of us, me included or the design engineers, had any idea [that] people were going to have complications with it,"

Quote
"what we're just finding out is [that] when you add that second lane in there, it makes it not just literally [more] difficult but potentially exponentially more difficult for some drivers."

Quote
"I'm optimistic in time with education and people becoming more familiar with roundabouts as more and more get built that that number can decrease. But [will it ever] get to fifty? I doubt it." (fifty referencing the fact that the feds consider any two-lane roundabout with over fifty crashes as high -- and State and Ellsworth averages 130). 

The Roundabout Drivers Hate

https://annarborobserver.com/s/the_roundabout_drivers_hate.html#.X0-2PNR7mK8


Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 02, 2020, 01:47:41 PM
Some interesting comments from Washtenaw County Road Commission engineer Mark McCulloch who was behind the very first roundabout cited on this thread: the State and Ellsworth roundabout in Ann Arbor. 

Quote
"I never once imagined in my wildest imagination when we built it that we were going to have the number of fender bender noninjury crashes increase,"

Quote
"We as engineers thought we are getting such great results with single lane roundabouts when it came to crash statistics and capacity analysis that we just thought automatically it was going to translate over into the multilane roundabouts,"

Quote
"None of us, me included or the design engineers, had any idea [that] people were going to have complications with it,"

Quote
"what we're just finding out is [that] when you add that second lane in there, it makes it not just literally [more] difficult but potentially exponentially more difficult for some drivers."

Quote
"I'm optimistic in time with education and people becoming more familiar with roundabouts as more and more get built that that number can decrease. But [will it ever] get to fifty? I doubt it." (fifty referencing the fact that the feds consider any two-lane roundabout with over fifty crashes as high -- and State and Ellsworth averages 130). 

The Roundabout Drivers Hate

https://annarborobserver.com/s/the_roundabout_drivers_hate.html#.X0-2PNR7mK8

Well... do they still require high school diploma to hold an engineering position at DOT?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 02, 2020, 05:02:38 PM
Well... do they still require high school diploma to hold an engineering position at DOT?

I don't know if part of engineering education is being taught to think outside the box on a regular basis. Thinking inside the box is, apparently, drilled into you from day one: standards, standards, standards.

Relevant because all roundabouts are supposed to be good: they are something within the box to improve safety. Ergo, install them, and winner winner chicken dinner. Even if the FHWA-ignored reality is that multi-lane roundabouts actually suck.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 02, 2020, 05:21:49 PM
Well... do they still require high school diploma to hold an engineering position at DOT?

I don't know if part of engineering education is being taught to think outside the box on a regular bases. Thinking inside the box is, apparently, drilled into you from day one: standards, standards, standards.

Relevant because all roundabouts are supposed to be good: they are something within the box to improve safety. Ergo, install them, and winner winner chicken dinner. Even if the FHWA-ignored reality is that multi-lane roundabouts actually suck.
That is a good thing for middle school, not so good for high school, and pretty poor for community college. I would think 2-year community college to be a bare minimum for holding those jobs, am I wrong?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 10, 2020, 02:47:31 PM
I noticed (thanks to a link (https://www.aaroads.com/forum/index.php?topic=18491.msg2532467#msg2532467) in another thread) that the southern roundabout at IN-265 and E 10th St in Utica, IN (https://www.google.com/maps/@38.3431491,-85.7062542,215m/data=!3m1!1e3) (just outside Jeffersonville) has meters for the two entrances from the north and west. I've seen meters at roundabouts before (https://goo.gl/maps/Pav1goqicKNFK2Bt9), but this seems to be both the only one with them installed from day one, and one of only a few with more than one entrance metered.

Indiana has other ramp meters (one example?) at roundabouts; Keystone Pkwy & Smokey Row (https://goo.gl/maps/iA48QbApxutUfa628) in Carmel being one example. Other than using only post-mounted HAWK signals, it's an identical setup.

Has anyone seen this in operation? I'm curious how drivers treat the yield entry when traffic is stopped from their left. Must look like they're frozen in time or something :-D.

I also find it interesting that HAWK signals were used. The other Indiana example (in Carmel) uses HAWK signals, but WSDOT uses their standard ramp meter setup with a pole-mounted RYG signal directly above a smaller RYG signal facing the stop line.

Here's a shot. Side-note: this roundabout briefly has four lanes right before the gore area. Perhaps the only four-lane roundabout in the US?

(https://i.imgur.com/Z0Jqsj1.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on September 10, 2020, 06:12:02 PM
I can see how the signals could be occasionally needed to avoid any backup of traffic onto the freeway.  The other thing that comes to mind would be if the signals are tied into the railroad crossing to help clear any backed up traffic on the crossing when a train approaches.   Likely that the signals don't get activated much unless one of the above scenarios arises.

Using HAWK signals makes sense as they can stay dark until needed, avoiding any unneeded confusion of a green light with the yield sign at the intersection to the roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: CardInLex on September 10, 2020, 06:12:36 PM
I noticed (thanks to a link (https://www.aaroads.com/forum/index.php?topic=18491.msg2532467#msg2532467) in another thread) that the southern roundabout at IN-265 and E 10th St in Utica, IN (https://www.google.com/maps/@38.3431491,-85.7062542,215m/data=!3m1!1e3) (just outside Jeffersonville) has meters for the two entrances from the north and west. I've seen meters at roundabouts before (https://goo.gl/maps/Pav1goqicKNFK2Bt9), but this seems to be both the only one with them installed from day one, and one of only a few with more than one entrance metered.

Indiana has other ramp meters (one example?) at roundabouts; Keystone Pkwy & Smokey Row (https://goo.gl/maps/iA48QbApxutUfa628) in Carmel being one example. Other than using only post-mounted HAWK signals, it's an identical setup.

Has anyone seen this in operation? I'm curious how drivers treat the yield entry when traffic is stopped from their left. Must look like they're frozen in time or something :-D.


(https://i.imgur.com/Z0Jqsj1.png)

I drive through frequently. I’ve never seen them in operation. But, I think they are more to do with the nearby rail crossing. My hypothesis: When RR is active, mainline has flashing red to keep roundabout clear. Then once the RR clears ramp gets flashing red to allow mainline backup to clear out.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on September 10, 2020, 06:42:37 PM

Has anyone seen this in operation? I'm curious how drivers treat the yield entry when traffic is stopped from their left. Must look like they're frozen in time or something :-D.


I've not been to this one in southern Indiana but I've experienced the scenario on the one in Carmel on the exit from Keystone Parkway.   Traffic is stopped far enough back from the intersection that it is fairly easy to tell that they aren't going anywhere.  Once the red light goes away it is easy enough to tell they are moving and then yield appropriately.  These signals are not activated that often other than as needed to prevent traffic backups onto northbound Keystone Parkway or on westbound Smoky Row (https://www.youarecurrent.com/2020/09/02/carmels-smoky-row-road-reverts-to-original-spelling/).  On street view you can see the sensor (https://www.google.com/maps/@39.9848432,-86.1135719,3a,75y,83.28h,96.88t/data=!3m6!1e1!3m4!1saMTPTaP_SWdYaYwCyotO1A!2e0!7i16384!8i8192) on the pole that detects backed up traffic.    Typically this only happens during rush periods often synced with the mass amount of student traffic entering or leaving the nearby high school.  At most times of the day the roundabout handles fairly light traffic so the signals are not activated.   In the many many times I've used this exit ramp I've only seen the signals active a few times.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on September 11, 2020, 09:30:10 AM
Using HAWK signals makes sense as they can stay dark until needed, avoiding any unneeded confusion of a green light with the yield sign at the intersection to the roundabout.

An important confusion to avoid.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 11, 2020, 12:22:38 PM

Has anyone seen this in operation? I'm curious how drivers treat the yield entry when traffic is stopped from their left. Must look like they're frozen in time or something :-D.


I've not been to this one in southern Indiana but I've experienced the scenario on the one in Carmel on the exit from Keystone Parkway.   Traffic is stopped far enough back from the intersection that it is fairly easy to tell that they aren't going anywhere.  Once the red light goes away it is easy enough to tell they are moving and then yield appropriately.  These signals are not activated that often other than as needed to prevent traffic backups onto northbound Keystone Parkway or on westbound Smoky Row (https://www.youarecurrent.com/2020/09/02/carmels-smoky-row-road-reverts-to-original-spelling/).  On street view you can see the sensor (https://www.google.com/maps/@39.9848432,-86.1135719,3a,75y,83.28h,96.88t/data=!3m6!1e1!3m4!1saMTPTaP_SWdYaYwCyotO1A!2e0!7i16384!8i8192) on the pole that detects backed up traffic.    Typically this only happens during rush periods often synced with the mass amount of student traffic entering or leaving the nearby high school.  At most times of the day the roundabout handles fairly light traffic so the signals are not activated.   In the many many times I've used this exit ramp I've only seen the signals active a few times.

I can't help but think the two were installed as test subjects to see if they would be useful at other roundabouts. I think they're a great idea and make roundabouts potentially more useful when one of the entrances tends to flood the circle (a common issue at exceptionally busy roundabouts with only one or two entry lanes ... the three lane roundabouts seem to handle large volumes better, and may explain why the one in Utica is rarely activated.

I drive through frequently. I’ve never seen them in operation. But, I think they are more to do with the nearby rail crossing. My hypothesis: When RR is active, mainline has flashing red to keep roundabout clear. Then once the RR clears ramp gets flashing red to allow mainline backup to clear out.

I don't dislike this theory, but that would also block cars from turning left towards Port Road and eastbound 265. I would think regular railway crossing signals and box markings would be superior? I mena, having traffic stop there will eventually result in a backup through the prior roundabout, and that would miss the point a bit.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on September 11, 2020, 02:17:15 PM

I can't help but think the two were installed as test subjects to see if they would be useful at other roundabouts. I think they're a great idea and make roundabouts potentially more useful when one of the entrances tends to flood the circle (a common issue at exceptionally busy roundabouts with only one or two entry lanes ... the three lane roundabouts seem to handle large volumes better, and may explain why the one in Utica is rarely activated.

The one at Smoky Row and Keystone Parkway was definitely installed to address a specific set of problems.   Prior to installation traffic would back up onto northbound Keystone Parkway during the evening rush hour and westbound Smoky Row traffic would back up during the school rush.   The signals have addressed both issues successfully.   

My gut feel is that these are probably activated a bit less now than when they were first installed due to the reduced traffic from Covid19 and the completion of the new interchange at 96th and Keystone (which removed the platoon effect of mass waves of synced traffic heading north on Keystone from the previous signal at 96th).    The great advantage of this solution is it doesn't affect traffic at all during normal roundabout operation and automatically responds only when needed to address an actual problem in progress.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 11, 2020, 06:56:45 PM

I can't help but think the two were installed as test subjects to see if they would be useful at other roundabouts. I think they're a great idea and make roundabouts potentially more useful when one of the entrances tends to flood the circle (a common issue at exceptionally busy roundabouts with only one or two entry lanes ... the three lane roundabouts seem to handle large volumes better, and may explain why the one in Utica is rarely activated.

The one at Smoky Row and Keystone Parkway was definitely installed to address a specific set of problems.   Prior to installation traffic would back up onto northbound Keystone Parkway during the evening rush hour and westbound Smoky Row traffic would back up during the school rush.   The signals have addressed both issues successfully.   

My gut feel is that these are probably activated a bit less now than when they were first installed due to the reduced traffic from Covid19 and the completion of the new interchange at 96th and Keystone (which removed the platoon effect of mass waves of synced traffic heading north on Keystone from the previous signal at 96th).    The great advantage of this solution is it doesn't affect traffic at all during normal roundabout operation and automatically responds only when needed to address an actual problem in progress.

I did not mean to imply that there were no reasons for the roundabout meters. Clearly, both roundabouts have a need for a meter. What I meant was more that these were being used as test dummies for other roundabouts, because they both have certain conditions that warranted some sort of experimentation. The one in Utica with the railway (potentially), and the one in Carmel because of the platooning effects from 96th, the nearby school, and the overall evening rush.

What I meant was more that the one in Utica was more about testing a large roundabout with meters, and the one in Carmel was more about testing a smaller roundabout with meters. Both are "interchange roundabouts" with at least one ramp having more or less constant flow conditions, but with one definitely needing it (Carmel) and the other perhaps not (Utica).
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on September 12, 2020, 11:30:38 AM

I did not mean to imply that there were no reasons for the roundabout meters. Clearly, both roundabouts have a need for a meter. What I meant was more that these were being used as test dummies for other roundabouts, because they both have certain conditions that warranted some sort of experimentation. The one in Utica with the railway (potentially), and the one in Carmel because of the platooning effects from 96th, the nearby school, and the overall evening rush.


Yep I got that, was just adding detail for others.
Title: Re: Crash prone 'modern roundabouts'
Post by: Revive 755 on September 12, 2020, 11:46:46 AM
Well... do they still require high school diploma to hold an engineering position at DOT?

Depending upon how "engineering position" is defined, a good number of states seem to require a four year degree, with some requiring licensure (or at least being on track for licensure in a certain amount of time).

I don't know if part of engineering education is being taught to think outside the box on a regular basis. Thinking inside the box is, apparently, drilled into you from day one: standards, standards, standards.

Relevant because all roundabouts are supposed to be good: they are something within the box to improve safety. Ergo, install them, and winner winner chicken dinner. Even if the FHWA-ignored reality is that multi-lane roundabouts actually suck.

I think this applies in multiple situations where agencies get hung up on standards rather than taking a good look at the project/intersection in question.  It really gets bad when those agencies strongly stand by outdated internal standards which become in conflict with other standards that get updated such as the MUTCD.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 16, 2020, 04:07:22 PM
File this under "overuse of roundabouts".

Can anyone explain what advantages this roundabout has over a traditional T-intersection? Traffic along the frontage road would still have priority even with a regular T-intersection. Only advantage that I can see might be traffic going slower and thus maybe easier to enter the roundabout from the "top" of the image. Still, traffic from the right has only just turned onto the road, so it's not like they're going very fast.

Near I-64 and Mason Road (https://goo.gl/maps/BoSob6dtoP6Vs8Kr8), just west of St Louis.

(https://i.imgur.com/fZU2J5e.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 16, 2020, 04:10:48 PM
I don't know if part of engineering education is being taught to think outside the box on a regular basis. Thinking inside the box is, apparently, drilled into you from day one: standards, standards, standards.

Relevant because all roundabouts are supposed to be good: they are something within the box to improve safety. Ergo, install them, and winner winner chicken dinner. Even if the FHWA-ignored reality is that multi-lane roundabouts actually suck.

I think this applies in multiple situations where agencies get hung up on standards rather than taking a good look at the project/intersection in question.  It really gets bad when those agencies strongly stand by outdated internal standards which become in conflict with other standards that get updated such as the MUTCD.

To be clear, I appreciate roadway standards. Without them, I'm sure we'd be in a very messy situation with our roads. Still, I really don't like "one size fits all" approaches to solving intersection problems, like roundabouts or DDIs, where they are installed with such great frequency that I have to assume they're dirt cheap. Otherwise, I feel like "spot improvements" are not given enough credit when it comes to improving issues like congestion or crash frequency.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on September 16, 2020, 04:19:34 PM
File this under "overuse of roundabouts".

Can anyone explain what advantages this roundabout has over a traditional T-intersection? Traffic along the frontage road would still have priority even with a regular T-intersection. Only advantage that I can see might be traffic going slower and thus maybe easier to enter the roundabout from the "top" of the image. Still, traffic from the right has only just turned onto the road, so it's not like they're going very fast.

Near I-64 and Mason Road (https://goo.gl/maps/BoSob6dtoP6Vs8Kr8), just west of St Louis.

(https://i.imgur.com/fZU2J5e.png)


1.  It could theoretically allow a free-flowing two-lane right turn out of the hospital parking lot–except that isn't the way they striped and signed it.

2.  It lets southbound traffic on Mason Road skirt around a red light by turning right with a Yield sign, going around the circle, and then turning right on red.   :)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 16, 2020, 05:18:14 PM
1.  It could theoretically allow a free-flowing two-lane right turn out of the hospital parking lot–except that isn't the way they striped and signed it.

2.  It lets southbound traffic on Mason Road skirt around a red light by turning right with a Yield sign, going around the circle, and then turning right on red.   :)

Based on your reply...I'm keeping it filed under "overuse" :-D.
Title: Re: Crash prone 'modern roundabouts'
Post by: CardInLex on September 16, 2020, 05:44:37 PM
1.  It could theoretically allow a free-flowing two-lane right turn out of the hospital parking lot–except that isn't the way they striped and signed it.

2.  It lets southbound traffic on Mason Road skirt around a red light by turning right with a Yield sign, going around the circle, and then turning right on red.   :)

Based on your reply...I'm keeping it filed under "overuse" :-D.

Google Maps places a bus stop marker on the outside of the roundabout. Perhaps it’s to allow busses turning off southbound Mason Road to drop off at the health facility and then turn back to resume going south on Mason. But that’s just a guess.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 16, 2020, 08:23:52 PM
1.  It could theoretically allow a free-flowing two-lane right turn out of the hospital parking lot–except that isn't the way they striped and signed it.

2.  It lets southbound traffic on Mason Road skirt around a red light by turning right with a Yield sign, going around the circle, and then turning right on red.   :)

Based on your reply...I'm keeping it filed under "overuse" :-D.

Google Maps places a bus stop marker on the outside of the roundabout. Perhaps it’s to allow busses turning off southbound Mason Road to drop off at the health facility and then turn back to resume going south on Mason. But that’s just a guess.

That would actually be quite plausible. But I did check Metro St Louis's route map, and the 65 runs along the frontage road, rather than along Mason. Route 57X uses Mason, but the closest stop is at Masonridge Rd (https://goo.gl/maps/J8WsypDqEudjrX3fA) on the other side of the interchange. Plus, it goes to and from downtown via 64, so it doesn't run past the health facility anyways.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on September 17, 2020, 08:58:53 AM

1.  It could theoretically allow a free-flowing two-lane right turn out of the hospital parking lot–except that isn't the way they striped and signed it.

2.  It lets southbound traffic on Mason Road skirt around a red light by turning right with a Yield sign, going around the circle, and then turning right on red.   :)

Based on your reply...I'm keeping it filed under "overuse" :-D.

Yeah, fair enough!

But I kind of doubt it's crash-prone.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 17, 2020, 02:16:19 PM

1.  It could theoretically allow a free-flowing two-lane right turn out of the hospital parking lot–except that isn't the way they striped and signed it.

2.  It lets southbound traffic on Mason Road skirt around a red light by turning right with a Yield sign, going around the circle, and then turning right on red.   :)

Based on your reply...I'm keeping it filed under "overuse" :-D.

Yeah, fair enough!

But I kind of doubt it's crash-prone.

No, that's true. Probably not a bunch of crashes. Although I still feel like it's overkill. Credit to them for doing something I've not seen done elsewhere, though.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on September 17, 2020, 02:31:44 PM
Could it be for traffic calming?

Left-turning traffic leaving the hospital would otherwise have to contend with cross-traffic accelerating toward WB I-64 from Mason Road.  With the teardrop design, on the other hand, that cross-traffic doesn't start accelerating toward the on-ramp till after the conflict point.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 17, 2020, 02:43:55 PM
Could it be for traffic calming?

Left-turning traffic leaving the hospital would otherwise have to contend with cross-traffic accelerating toward WB I-64 from Mason Road.  With the teardrop design, on the other hand, that cross-traffic doesn't start accelerating toward the on-ramp till after the conflict point.

I actually mentioned that in my original post as being the main advantage:

Only advantage that I can see might be traffic going slower and thus maybe easier to enter the roundabout from the "top" of the image. Still, traffic from the right has only just turned onto the road, so it's not like they're going very fast.
Title: Re: Crash prone 'modern roundabouts'
Post by: Occidental Tourist on September 18, 2020, 01:34:03 AM
Maybe it’s the standard explanation given for roundabouts: traffic turning left from the hospital is less likely to get in a severe collision by making the movement in a circle versus the potential T-bone situation of a direct left across traffic coming from the side.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 18, 2020, 01:13:47 PM
Maybe it’s the standard explanation given for roundabouts: traffic turning left from the hospital is less likely to get in a severe collision by making the movement in a circle versus the potential T-bone situation of a direct left across traffic coming from the side.

That's a fair point. Although traffic only did just turn onto this road 200 feet before the roundabout. Hard to believe they'd have picked up enough speed to cause any serious crash.

I think I'm going with this explanation: Missouri likes roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on September 18, 2020, 01:19:20 PM
Although traffic only did just turn onto this road 200 feet before the roundabout. Hard to believe they'd have picked up enough speed to cause any serious crash.

But see my point from earlier:

Left-turning traffic leaving the hospital would otherwise have to contend with cross-traffic accelerating toward WB I-64 from Mason Road.

It isn't just that traffic is accelerating–it's that a lot of it would be accelerating up to freeway speeds and probably wouldn't much feel like slowing down partway through.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 18, 2020, 02:55:42 PM
That's true as well. The speed limit on the frontage road is only 45 mph, which isn't really fast enough to normally worry about left turns across traffic (although probably the upper limit in most states). But then I doubt most people care about the frontage limit when they fully intend to enter I-64.

Another alternative to the roundabout would have been making this a RIRO, since there is another entrance to the healthcare facility along Mason Road to the north, with full access via a flush median. Problem is that it's signed as "Emergency Access Only", probably because the main entrance is meant to be the roundabout.

Still stranger: there is absolutely no pedestrian access to this facility from anywhere. They were apparently so focused on improving safety for that left turn onto the frontage road, they forgot to implement a safe passage for foot traffic to the hospital.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on September 23, 2020, 05:18:57 PM
This thread has had a huge amount of discussion regarding roundabouts, but I don't remember anything regarding the use of raised pedestrian crosswalks at the roundabout entries and exits.   This is something Carmel Indiana has been implementing on new roundabouts (and in one case retrofitting an existing roundabout) on the Rangeline Road corridor over the last few years.  These raised crosswalks have a traffic calming effect resulting in reduced speeds as traffic enter and exit each roundabout.  There have also been a few mid block raised crosswalks added as well between roundabouts.

Thoughts?

https://www.google.com/maps/@39.9755516,-86.1271211,3a,75y,169.53h,81.54t/data=!3m6!1e1!3m4!1sfvxFF730r__X4iMXGqqB_Q!2e0!7i13312!8i6656

https://www.google.com/maps/@39.9705177,-86.1270149,3a,75y,194.32h,84.54t/data=!3m6!1e1!3m4!1sZHKbCsrB2aqScLEp8aA66Q!2e0!7i16384!8i8192

https://www.google.com/maps/@39.9632378,-86.1268071,3a,75y,212.05h,75.32t/data=!3m6!1e1!3m4!1s7raZSUavITxTfZjKnjKpWw!2e0!7i16384!8i8192

https://www.google.com/maps/@39.9664102,-86.1269386,3a,75y,188.39h,68.32t/data=!3m6!1e1!3m4!1s3zBt67yZlWrq-HBxlWbIig!2e0!7i16384!8i8192

https://www.google.com/maps/@39.9690558,-86.1270773,3a,75y,17.74h,87.44t/data=!3m6!1e1!3m4!1sqJTPsvSK0RyaG9ZGAvJyXA!2e0!7i16384!8i8192

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 23, 2020, 06:31:06 PM
This thread has had a huge amount of discussion regarding roundabouts, but I don't remember anything regarding the use of raised pedestrian crosswalks at the roundabout entries and exits.   This is something Carmel Indiana has been implementing on new roundabouts (and in one case retrofitting an existing roundabout) on the Rangeline Road corridor over the last few years.  These raised crosswalks have a traffic calming effect resulting in reduced speeds as traffic enter and exit each roundabout.  There have also been a few mid block raised crosswalks added as well between roundabouts.

Thoughts?

https://www.google.com/maps/@39.9755516,-86.1271211,3a,75y,169.53h,81.54t/data=!3m6!1e1!3m4!1sfvxFF730r__X4iMXGqqB_Q!2e0!7i13312!8i6656

https://www.google.com/maps/@39.9705177,-86.1270149,3a,75y,194.32h,84.54t/data=!3m6!1e1!3m4!1sZHKbCsrB2aqScLEp8aA66Q!2e0!7i16384!8i8192

https://www.google.com/maps/@39.9632378,-86.1268071,3a,75y,212.05h,75.32t/data=!3m6!1e1!3m4!1s7raZSUavITxTfZjKnjKpWw!2e0!7i16384!8i8192

https://www.google.com/maps/@39.9664102,-86.1269386,3a,75y,188.39h,68.32t/data=!3m6!1e1!3m4!1s3zBt67yZlWrq-HBxlWbIig!2e0!7i16384!8i8192

https://www.google.com/maps/@39.9690558,-86.1270773,3a,75y,17.74h,87.44t/data=!3m6!1e1!3m4!1sqJTPsvSK0RyaG9ZGAvJyXA!2e0!7i16384!8i8192
As a guess...
Good idea to improve pedestrian safety.
A lot of struts being replaced by local shops.
Probably decreases intersection throughput - if there is a significant truck traffic, likely to the level of single lane all way stop system.
Only 3 of the links are for roundabout locations.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on September 24, 2020, 10:37:19 AM

A lot of struts being replaced by local shops.
Probably decreases intersection throughput - if there is a significant truck traffic, likely to the level of single lane all way stop system.
Only 3 of the links are for roundabout locations.


Also note that the corridor construction is still ongoing.  There will be additional roundabouts added in the near future and Google maps street view doesn't yet reflect recently completed addition of raised crosswalks at the Carmel Drive roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 24, 2020, 03:08:31 PM
When I last drove through the Carmel area (early July), I got to experience a few of those raised crosswalks.

First impression was that: well, they make sense. If there's a problem with roundabouts, it's that exiting traffic can sometimes move pretty quickly. This helps to curb that a bit. From walking through numerous roundabouts in Fisher around the same time period, traffic entering a roundabout seems pretty good at yielding to pedestrians since they're slowed down, but traffic exiting is mostly focused on speeding up and leaving the roundabout without hitting someone, and pedestrians don't seem to be on their mind.

Other impression is that for busy roundabouts, they may not be advisable. For example, triple lane or double lane roundabouts that are along corridors with speed limits 35 or greater, really should just use RRFBs with zebra crossings (not HAWKs either, unless used for ramp metering, since those can quickly cause gridlock).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 05, 2020, 10:52:08 AM
The grey car driving through the completed Sarasota roundabout at the end of this video pretty much sums up the confusion some drivers have when navigating a roundabout. 

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 05, 2020, 10:58:41 AM
Another video on how to drive through a roundabout.



Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 05, 2020, 02:49:00 PM
That Florida roundabout seems to be the second example of a "proper" turbo roundabout in North America, right after the turbo roundabout leaving Sidney Airport on Vancouver Island.

Much that like example, this one still features flat islands. I would love to see actual soft bumps.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 13, 2021, 10:29:19 AM
There has been another fatal crash at a Hamburg, NY roundabout this time involving a bicyclist.  Prior to that there had been 2 fatal crashes at the Big Tree/South Park Ave. roundabout after vehicles struck decorative rocks in the central island of the roundabout.  There are examples of counties with over 1 million people that have dozens of roundabouts where there hasn't been a documented roundabout fatality over decades of data.  Yet this small town outside Buffalo has seen 3 roundabout fatalities at their handful of roundabouts.  Either the community has been extremely unlucky or there is something inherently unsafe about their roundabout designs.




Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on April 25, 2021, 03:24:00 PM
American drivers at work

https://twitter.com/OregonRolledA20/status/1386160018056093698
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 25, 2021, 04:40:54 PM
American drivers at work

More like American engineering at its best. They installed roundabout, mission accomplished!
Signage, pavement markings? Why would anyone need that? < /sarcasm>
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on April 25, 2021, 06:22:43 PM
American drivers at work

More like American engineering at its best. They installed roundabout, mission accomplished!
Signage, pavement markings? Why would anyone need that? < /sarcasm>

Surely you noticed it's actively under construction?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 25, 2021, 06:37:23 PM
American drivers at work

More like American engineering at its best. They installed roundabout, mission accomplished!
Signage, pavement markings? Why would anyone need that? < /sarcasm>

Surely you noticed it's actively under construction?
I certainly noticed that it is open for traffic. An  if you ever saw temporary signs in a construction zone, you may have an idea about some possibilities to mitigate confusion like what we see.
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on April 25, 2021, 09:55:30 PM
What are the odds that anyone would have followed the signage and pavement markings even if they were present? It looked like there was a pretty strong follow-the-leader effect there, where once the first guy in line did something stupid, everyone else decided to just copy what they were doing.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 26, 2021, 04:25:53 AM
What are the odds that anyone would have followed the signage and pavement markings even if they were present? It looked like there was a pretty strong follow-the-leader effect there, where once the first guy in line did something stupid, everyone else decided to just copy what they were doing.
Which probably means leader was the best hint available.
As it was noticed, this is an area under construction, we don't know how traffic patterns changed during that time.
Google maps don't show new layout; old intersection had some dedicated turn lanes, I can easily see drivers expecting those dedicated lanes to be still present in some way.
Overall, I wonder why roundabout was considered at all when adding a traffic light would be a much more reasonable thing to do.
Title: Re: Crash prone 'modern roundabouts'
Post by: wanderer2575 on April 26, 2021, 01:19:33 PM
American drivers at work

https://twitter.com/OregonRolledA20/status/1386160018056093698

I just saw this on humorist Dave Barry's blog today and came here to post, but you beat me to it.

The "Thunder and Blazes" soundtrack was a nice touch.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on April 26, 2021, 01:36:22 PM
If we are ok with using the 85 percentile measurement to create rules (since drivers are safe and prudent and all that), I believe the official policy in that intersection is to drive on the left from now on
Title: Re: Crash prone 'modern roundabouts'
Post by: ibthebigd on April 26, 2021, 06:28:50 PM
Kentucky is on a don't put a light fix lately. Where that video is from is a good Roundabout candidate because it doesn't have consistent traffic but is by a lake. Should have been a bigger Roundabout.

Kentucky has been putting J Turns where people would like a light.



SM-G950U

Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 26, 2021, 06:50:04 PM
So does traffic only come from one direction there?  Because that's all I saw in the video.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 26, 2021, 07:24:03 PM
So does traffic only come from one direction there?  Because that's all I saw in the video.
That is the traffic from I-64, about 3 miles away.
Reported AADT on 4 arms are are 4800, 4300, 2100 and 3200, with relatively weak rush hour. This may be before the  Dollar store  was built on one corner within past few years , and there is some construction going on in another corner, though.
Title: Re: Crash prone 'modern roundabouts'
Post by: CardInLex on April 26, 2021, 08:27:38 PM
The original video poster on Facebook (Walker Construction) has posted an update saying that the video was partially staged and that all traffic was being directed by flaggers.

https://fb.watch/575atAPP3x/
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on April 27, 2021, 02:08:41 AM
The original video poster on Facebook (Walker Construction) has posted an update saying that the video was partially staged and that all traffic was being directed by flaggers.

https://fb.watch/575atAPP3x/

Not exactly. They said there were flaggers upstream, which explains why all the traffic came from one direction. However, when they reached the roundabout, the drivers appear to have picked the wrong side on their own.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 27, 2021, 11:48:55 AM
The original video now appears to be gone from the thread, but...

Was traffic driving on the left side of the road?  I can't remember.  What would you do if you were driving in one-lane traffic on the left half of a roadway and then came to a roundabout?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 27, 2021, 12:29:29 PM
The original video now appears to be gone from the thread, but...

Was traffic driving on the left side of the road?  I can't remember.  What would you do if you were driving in one-lane traffic on the left half of a roadway and then came to a roundabout?
Some of those who were to make a left turn (and should make 3/4 of a circle on the roundabout) were entering on the wrong side of the divider and making a 1/4 turn wrong way.
I know one local roundabout where people were doing that on a regular basis - until police cracked down on such pattern.

And honestly speaking I am doing that myself all the time. It should be noted, though, that I am doing that on a cul-de-sac with 3 driveways, AADT of maybe 15-20 vehicles, and average speeds of <10 MPH - so I still have to hear a complain.

There are also some roundabouts here where one-way "street" (highway ramp) enters roundabout. A full roundabout, not a dumbell (which would be an appropriate option). No wrong way issues there.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 27, 2021, 12:59:38 PM
They were talking about that Northeast Kentucky roundabout video on the morning radio show coming into work.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 27, 2021, 01:17:54 PM
What I mean is this:  was traffic driving on the left side upstream of the roundabout?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 27, 2021, 01:43:37 PM
What I mean is this:  was traffic driving on the left side upstream of the roundabout?
Upstream is a 2-lane undivided road, with a divider starting 50' (give or take) from the circle.
Some cars went to the left of that divider, going into the wrong way lane. WOuld be justified if they considered divider as the beginning of some sort of a slip lane, for example.
 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 27, 2021, 01:53:11 PM
Here's a repost:

https://twitter.com/achidente/status/1386218385298526208
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 27, 2021, 02:15:45 PM
Thanks, that answered my question.  They were not driving on the left already.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 27, 2021, 03:05:19 PM
Thanks, that answered my question.  They were not driving on the left already.

I suppose for someone in your position, having not seen the video until then, what you saw in the video was the more worrying of the possibilities.

Watching the video from Facebook, I think the contractor probably should stop sharing videos. Even in that video, you see traffic yielding to entering traffic.

I challenge someone here to get 60 seconds of roundabout footage from a drone that doesn't capture someone breaking a rule.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 27, 2021, 03:20:49 PM
I challenge someone here to get 60 seconds of roundabout footage of any intersection from a drone that doesn't capture someone breaking a rule.

or that
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on April 27, 2021, 11:14:41 PM
I live on the corner of a T intersection in a residential neighborhood, so I could probably do that easy...if I had a drone.....
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 28, 2021, 09:27:15 AM
I live on the corner of a T intersection in a residential neighborhood, so I could probably do that easy...if I had a drone.....

Then I assume it must be an uncontrolled intersection, or else I'm sure you'd find people not coming to a complete stop.
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on April 28, 2021, 10:27:10 AM
I live on the corner of a T intersection in a residential neighborhood, so I could probably do that easy...if I had a drone.....

Then I assume it must be an uncontrolled intersection, or else I'm sure you'd find people not coming to a complete stop.

In 60 seconds? Would be pretty easy to get 60 seconds with no traffic at all.
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on April 28, 2021, 10:31:58 AM
Meanwhile, I live near a three-way stop where, if I had 60 minutes of footage, you might not see any cars on the through road come to a complete stop.

Probably because (1) the through road doesn't need a stop sign; it's not even close to warranted based on volumes, but there are other local factors that took precedence, and (2) there didn't used to be a stop sign there, so some drivers forget it exists.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 28, 2021, 10:37:49 AM


I live on the corner of a T intersection in a residential neighborhood, so I could probably do that easy...if I had a drone.....

Then I assume it must be an uncontrolled intersection, or else I'm sure you'd find people not coming to a complete stop.

In 60 seconds? Would be pretty easy to get 60 seconds with no traffic at all.

Well, crap, I kept thinking of this as 60 minutes.  Even though, in its original context, 60 minutes would be too long of a period to be meaningful.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 28, 2021, 01:16:44 PM
I challenge someone here to get 60 seconds of roundabout footage of any intersection from a drone that doesn't capture someone breaking a rule.

or that

Yeah, failure to stop at a stop line? In a given 60 second window, that is easily the most broken rule, and it's not a fundamental failure of the intersection. Cali stops are so unbelievably common that it may as well be legal at this point. No other rules are broken anywhere near as often. Second place is probably failure to maintain a lane, and I don't think that happens every 60 seconds.

Roundabouts seem to have far more fundamental failures on a regular basis. Biggest two easily being failure to yield or excessive yielding, and failure to maintain a lane...I'm willing to bet that at least one of these things would occur in a given 60 second window (although more likely at multi-lane roundabouts), and both, IMO, are fundamental failures.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 28, 2021, 01:18:41 PM
Yeah, failure to stop at a stop line? In a given 60 second window, that is easily the most broken rule, and it's not a fundamental failure of the intersection. Cali stops are so unbelievably common that it may as well be legal at this point. No other rules are broken anywhere near as often. Second place is probably failure to maintain a lane, and I don't think that happens every 60 seconds.

Roundabouts seem to have far more fundamental failures on a regular basis. Biggest two easily being failure to yield or excessive yielding, and failure to maintain a lane...I'm willing to bet that at least one of these things would occur in a given 60 second window (although more likely at multi-lane roundabouts), and both, IMO, are fundamental failures.

Failure to maintain a lane is a big one, in my experience.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 28, 2021, 01:26:44 PM
Failure to maintain a lane is a big one, in my experience.

But it's a far more prevalent issue at multi-lane roundabouts, in addition to failure to yield/excessive yielding.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 28, 2021, 01:30:36 PM

Failure to maintain a lane is a big one, in my experience.

But it's a far more prevalent issue at multi-lane roundabouts, ...

Absolutely.  Even properly keeping your lane in a multi-lane roundabout still provides the opportunity for multiple conflict points.  I remember the reduction in conflict points being a big selling point for roundabouts several years ago, but that advantage (IMHO) goes away when you add additional lanes.
Title: Re: Crash prone 'modern roundabouts'
Post by: interstatefan990 on April 28, 2021, 01:41:39 PM
See my signature.
Title: Re: Crash prone 'modern roundabouts'
Post by: stevashe on April 29, 2021, 03:44:03 PM
Even in that video, you see traffic yielding to entering traffic.

Am I missing something? I don't see anyone yielding to entering traffic in the new video...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 29, 2021, 04:05:53 PM
Even in that video, you see traffic yielding to entering traffic.

Am I missing something? I don't see anyone yielding to entering traffic in the new video...

In the beginning, the red truck approaching from the right stops despite no one to his left. Only once cars stop coming from their right (the top approach) do they continue into the circle.

The red truck should have entered into the circle, and the silver sedan from the top should have yielded to them.
Title: Re: Crash prone 'modern roundabouts'
Post by: stevashe on April 29, 2021, 05:34:10 PM
I see, I was looking for someone within the circle yielding, which would be much worse. Honestly I wouldn't even consider that as breaking a rule. As far as I know, there's no rule compelling you to go as soon as you can from a yield sign  :-P Not to mention the truck only stops for about a second, which I think is reasonable since this is a brand new roundabout, after all.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 29, 2021, 06:13:49 PM
As far as I know, there's no rule compelling you to go as soon as you can from a yield sign  :-P

The rule only says you should stop to begin with "if required for safety" (UVC Art. IV, § 11-40).
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 29, 2021, 06:18:24 PM
I see, I was looking for someone within the circle yielding, which would be much worse. Honestly I wouldn't even consider that as breaking a rule. As far as I know, there's no rule compelling you to go as soon as you can from a yield sign  :-P Not to mention the truck only stops for about a second, which I think is reasonable since this is a brand new roundabout, after all.

Now may be a good time to mention why I said "rule" and not "law". Stopping unnecessarily at a yield sign is not breaking a law, but it's breaking many of the "soft" rules of roundabouts, including not stopping unless you have to.

I don't mind giving drivers a free pass, especially at a new intersection, but odd roundabout behavior doesn't seem to end after that "new" period has passed.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on April 29, 2021, 06:35:03 PM
I see, I was looking for someone within the circle yielding, which would be much worse. Honestly I wouldn't even consider that as breaking a rule. As far as I know, there's no rule compelling you to go as soon as you can from a yield sign  :-P Not to mention the truck only stops for about a second, which I think is reasonable since this is a brand new roundabout, after all.

Now may be a good time to mention why I said "rule" and not "law". Stopping unnecessarily at a yield sign is not breaking a law, but it's breaking many of the "soft" rules of roundabouts, including not stopping unless you have to.

I don't mind giving drivers a free pass, especially at a new intersection, but odd roundabout behavior doesn't seem to end after that "new" period has passed.

Some of this is apprehension, wondering if the other driver will stop.  That's defensive driving, and while it's more so for some people than others, I get it.

Some of it is people just never really understanding the rules of the road...and this group is more dangerous. These are the people that will say "everyone else is an idiot", not realizing that THEY are the one that did wrong.  These are the people that will merge on a highway as soon as possible, even though they're 30 mph under the limit, and believe the person in the right lane is at fault for having not moved over already.  These are the people that will change lanes because they put their turn signal on, believing that the signal gives them the absolute right to turn and others must yield to them.   And when it comes to roundabouts, whatever they decide to do at a roundabout is the right thing, and everyone else screwed up.  These are the loudest people to complain, and there's no convincing them that they are actually the ones causing the issues.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on April 29, 2021, 10:34:26 PM
Update on that Kentucky roundabout - now that it has actually been completed (proper lane markings, keep right signage, yield signs, etc.) it's doing better.

https://www.core77.com/posts/108602/An-Example-of-the-Importance-of-Signage-When-US-Drivers-Dont-Know-How-to-Use-a-Roundabout
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 30, 2021, 07:39:28 AM
Update on that Kentucky roundabout - now that it has actually been completed (proper lane markings, keep right signage, yield signs, etc.) it's doing better.

https://www.core77.com/posts/108602/An-Example-of-the-Importance-of-Signage-When-US-Drivers-Dont-Know-How-to-Use-a-Roundabout
Someone needs to tell KY engineers about modern traffic control devices. They learnt about proper signage the hard way, next lesson should be about traffic lights, though.
Title: Re: Crash prone 'modern roundabouts'
Post by: ErmineNotyours on August 01, 2021, 12:00:44 PM
I finally got a picture of the roundabout between two bicycle trails in Lacey, Washington.  These are actually two rail trails, though they (the railroads) used to cross on different grades.

(https://live.staticflickr.com/65535/51350387988_66619cef89_z.jpg) (https://flic.kr/p/2meEak3)
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 01, 2021, 01:32:32 PM
Update on that Kentucky roundabout - now that it has actually been completed (proper lane markings, keep right signage, yield signs, etc.) it's doing better.

https://www.core77.com/posts/108602/An-Example-of-the-Importance-of-Signage-When-US-Drivers-Dont-Know-How-to-Use-a-Roundabout
Someone needs to tell KY engineers about modern traffic control devices. They learnt about proper signage the hard way, next lesson should be about traffic lights, though.

It has been mentioned too many times to even bother with trying to mention again, but the first video was taken during construction when traffic control people intentionally directed people the wrong way. The video intentionally left that out.
Title: Re: Crash prone 'modern roundabouts'
Post by: Flint1979 on August 07, 2021, 09:41:22 AM
It seems like Michigan drivers can't be bothered to learn how to use a roundabout. They are popping up in Saginaw County and people in Saginaw are all mad because they don't know how to use one. Well learn how to use one. Also there has been one at I-75 and M-81 for 15 years you can't tell me that you've never gone through that intersection if you live in Saginaw.
Title: Re: Crash prone 'modern roundabouts'
Post by: tigerwings on August 07, 2021, 03:58:52 PM
ODOT is going to to rework the roundabout at Cherry Street, Berdan Ave, and N Detroit Ave in Toledo.

I had the pleasure to detour around this mess, and almost got hit at the roundabout at Phillips Ave.

41.68542050894232, -83.55617826575642

https://www.wtol.com/article/news/local/cherry-street-berdan-avenue-detroit-avenue-roundabout-construction-odot-dangerous-intersection-ohio/512-e805ba44-70ff-4c6d-96f8-4dfae2a08dd0
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 08, 2021, 09:27:19 AM
ODOT is going to to rework the roundabout at Cherry Street, Berdan Ave, and N Detroit Ave in Toledo.

I had the pleasure to detour around this mess, and almost got hit at the roundabout at Phillips Ave.

41.68542050894232, -83.55617826575642

https://www.wtol.com/article/news/local/cherry-street-berdan-avenue-detroit-avenue-roundabout-construction-odot-dangerous-intersection-ohio/512-e805ba44-70ff-4c6d-96f8-4dfae2a08dd0

Good to see they are reworking the most crash-prone intersection in Toledo.  This has always been a confusing roundabout. To most drivers it feels completely natural to take that blue path and continue along Detroit Avenue but that movement is not allowed and you risk getting side-swiped by a vehicle in the right lane.  Just a poor design from the beginning as it doesn't reflect most drivers' expectations IMO.

(https://i.imgur.com/SmVGmkU.png)





Title: Re: Crash prone 'modern roundabouts'
Post by: skluth on August 08, 2021, 12:54:32 PM
ODOT is going to to rework the roundabout at Cherry Street, Berdan Ave, and N Detroit Ave in Toledo.

I had the pleasure to detour around this mess, and almost got hit at the roundabout at Phillips Ave.

41.68542050894232, -83.55617826575642

https://www.wtol.com/article/news/local/cherry-street-berdan-avenue-detroit-avenue-roundabout-construction-odot-dangerous-intersection-ohio/512-e805ba44-70ff-4c6d-96f8-4dfae2a08dd0

Good to see they are reworking the most crash-prone intersection in Toledo.  This has always been a confusing roundabout. To most drivers it feels completely natural to take that blue path and continue along Detroit Avenue but that movement is not allowed and you risk getting side-swiped by a vehicle in the right lane.  Just a poor design from the beginning as it doesn't reflect most drivers' expectations IMO.

(https://i.imgur.com/SmVGmkU.png)

I don't see a problem with following the blue path as the lane markings in the roundabout look like they prohibit those in the right lane from continuing on the roundabout and having to exit onto North Detroit. The directional guidance on the street coming from the south also indicate that. However the markings going into the roundabout from Collingwood direct differently. The roundabout has contradictory markings. It's little wonder there are accidents.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 08, 2021, 05:32:42 PM
ODOT is going to to rework the roundabout at Cherry Street, Berdan Ave, and N Detroit Ave in Toledo.

I had the pleasure to detour around this mess, and almost got hit at the roundabout at Phillips Ave.

41.68542050894232, -83.55617826575642

https://www.wtol.com/article/news/local/cherry-street-berdan-avenue-detroit-avenue-roundabout-construction-odot-dangerous-intersection-ohio/512-e805ba44-70ff-4c6d-96f8-4dfae2a08dd0

Good to see they are reworking the most crash-prone intersection in Toledo.  This has always been a confusing roundabout. To most drivers it feels completely natural to take that blue path and continue along Detroit Avenue but that movement is not allowed and you risk getting side-swiped by a vehicle in the right lane.  Just a poor design from the beginning as it doesn't reflect most drivers' expectations IMO.
(..clipped..)

I don't see a problem with following the blue path as the lane markings in the roundabout look like they prohibit those in the right lane from continuing on the roundabout and having to exit onto North Detroit. The directional guidance on the street coming from the south also indicate that. However the markings going into the roundabout from Collingwood direct differently. The roundabout has contradictory markings. It's little wonder there are accidents.
If you look closer, you may realize that blue path is considered a right turn movement for 4 o'clock entrance. So no right turn from inner lane, e.g. no blue path.
To make things more interesting, both lanes at  7 o'clock entrance allow "straight"  movement - straight meaning exit at 12 o'clock from both lanes. So there is still a possibility of collision even with full compliance to the signage.
(yawn) year 10 of a learning curve, nothing to see here.

Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on August 08, 2021, 11:56:28 PM
Those arrows do indeed look very confusing. Add to that, its poorly designed so the exit is perfectly straight, meaning both vehicles are accelerating.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 09, 2021, 11:33:16 AM
Kelley Squre in Worcester in my opinion is a good example of a roundabout that simplified traffic movements:

(https://i.ytimg.com/vi/2PNyIBxcxfU/maxresdefault.jpg)
(https://www.gannett-cdn.com/presto/2020/12/31/NTEG/86da81b0-1c81-4ccd-a116-47da1269064c-LOC_Worcester_aerials_1.JPG?width=660&height=495&fit=crop&format=pjpg&auto=webp)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 11, 2021, 03:45:34 AM
^^^
One thing confusing to me about the change was the modification of the one-way system south of the roundabout.

Both Harding and Millbury had their directions switched, and I can't for the life of me figure out why this was necessary.
Title: Re: Crash prone 'modern roundabouts'
Post by: swiftdo on August 13, 2021, 01:25:24 PM
It seems like Michigan drivers can't be bothered to learn how to use a roundabout. They are popping up in Saginaw County and people in Saginaw are all mad because they don't know how to use one. Well learn how to use one. Also there has been one at I-75 and M-81 for 15 years you can't tell me that you've never gone through that intersection if you live in Saginaw.

You should hear people around Traverse City complain about the new roundabouts being built in the area. I think it was only a few days after it opened that a truck plowed through a new one on M 37 south of Chums Corner. Drivers up here just like to complain instead of learning how to use them.
Title: Re: Crash prone 'modern roundabouts'
Post by: civilmaher on August 17, 2021, 01:24:12 PM
Is there an upper limit for roundabout AADT? I'm looking into the feasibility of a multi-lane roundabout that would have an AADT of about 70,000 vehicles, and side street traffic would be approx. 12% of that share. I'm looking for a hard national guideline or standard that would tell me that this would/wouldn't be feasible. Thanks!
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on August 17, 2021, 01:42:39 PM
Is there an upper limit for roundabout AADT? I'm looking into the feasibility of a multi-lane roundabout that would have an AADT of about 70,000 vehicles, and side street traffic would be approx. 12% of that share. I'm looking for a hard national guideline or standard that would tell me that this would/wouldn't be feasible. Thanks!
I would say infeasible. FHWA charts go up to 3500 VPH, not as a hard standard, but a reasonable link. More qualified sources I cannot find right now gave 30k/day at most.
https://www.fhwa.dot.gov/publications/research/safety/00067/000674.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: civilmaher on August 18, 2021, 02:36:17 PM
Is there an upper limit for roundabout AADT? I'm looking into the feasibility of a multi-lane roundabout that would have an AADT of about 70,000 vehicles, and side street traffic would be approx. 12% of that share. I'm looking for a hard national guideline or standard that would tell me that this would/wouldn't be feasible. Thanks!

I would say infeasible. FHWA charts go up to 3500 VPH, not as a hard standard, but a reasonable link. More qualified sources I cannot find right now gave 30k/day at most.
https://www.fhwa.dot.gov/publications/research/safety/00067/000674.pdf


Thanks kalvado!
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 18, 2021, 06:02:53 PM
I would have to agree. I am not familiar with roundabouts along roads with 70,000 AADT, at least in the United States. So my hunch would certainly lean towards infeasible.

It is possible that it could work with partial signalization during peak hours, whereby one or more approaches are metered, allowing the otherwise-burdened entry additional uninterrupted entry flow for brief periods. WSDOT installed a ramp meter to improve the flow of a roundabout in Richland, WA a couple years ago; you can read about it here (https://wsdot.wa.gov/projects/sr240/steptoe-roundabout/home).

But, ultimately, I see that more as a band-aid than a new-build solution. I think the only proper modification to this kind of intersection is an interchange.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 18, 2021, 10:24:19 PM
I'm not going to find volume counts from 25-30 years ago, but along NJ 70 today, the traffic counts are around the 50,000-55,000 vehicle mark, and the Cherry Hill traffic circles (granted, not roundabouts) were removed in the early 1990's because they were overwhelmed with traffic.  And they used a metering system for many years prior to their removal.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 07, 2021, 05:31:02 PM
Since opening in May 2020, the roundabout at Highway 95A and U.S. 50 in Silver Springs, Nevada has been the site of two fatal crashes.  The latest fatality occurred on Labor day.

Quote
Driver dies in fiery Silver Springs wreck - Preliminary investigation shows that both a red 1998 Peterbilt semi tractor-trailer car hauler and a gray 2000 Honda Accord were traveling southbound on U.S. 95A approaching the roundabout with U.S. 50.  The driver of the Peterbilt was unable to slow his vehicle due to suspected mechanical failure and the front of the Peterbilt struck the rear of the Honda, the release said. Both vehicles continued southbound and entered the raised decorative rock median of the roundabout. Both vehicles caught fire.  The driver of the Honda, who is currently unidentified due to the extent of burn damage, was pronounced deceased on scene.  https://www.nevadaappeal.com/news/2021/jun/07/driver-dies-fiery-silver-springs-wreck/

Quote
Fallon Man Dies in Crash Near U.S. 50 Roundabout in Silver Springs - Nevada Highway Patrol has identified the driver killed in a rollover crash on U.S. 50 near the roundabout in Silver Springs early Monday morning.  The crash happened just before 5:15 a.m. on Monday at U.S. 50 and U.S. 50A. NHP says a preliminary investigation shows that a gray 2007 Chevrolet Silverado was heading west on U.S. 50 when the driver failed to slow down for the roundabout and hit the decorative rock wall and went over it. At that point, NHP says the pickup flipped, landed on its roof and slid across the road before stopping.  The driver of the Chevrolet, 21-year-old Anthony King died on scene. https://www.ktvn.com/story/44675667/fatal-crash-slows-traffic-near-us-50-roundabout-in-silver-springs

Title: Re: Crash prone 'modern roundabouts'
Post by: TheHighwayMan394 on September 07, 2021, 06:05:52 PM
Since opening in May 2020, the roundabout at Highway 95A and U.S. 50 in Silver Springs, Nevada has been the site of two fatal crashes.  The latest fatality occurred on Labor day.

Quote
Driver dies in fiery Silver Springs wreck - Preliminary investigation shows that both a red 1998 Peterbilt semi tractor-trailer car hauler and a gray 2000 Honda Accord were traveling southbound on U.S. 95A approaching the roundabout with U.S. 50.  The driver of the Peterbilt was unable to slow his vehicle due to suspected mechanical failure and the front of the Peterbilt struck the rear of the Honda, the release said. Both vehicles continued southbound and entered the raised decorative rock median of the roundabout. Both vehicles caught fire.  The driver of the Honda, who is currently unidentified due to the extent of burn damage, was pronounced deceased on scene.  https://www.nevadaappeal.com/news/2021/jun/07/driver-dies-fiery-silver-springs-wreck/

Um, unless I'm missing something, the roundabout had absolutely nothing to do with the fatal accident. He wouldn't have been able to stop for a red light and the other driver still would have died.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 07, 2021, 11:00:21 PM
Since opening in May 2020, the roundabout at Highway 95A and U.S. 50 in Silver Springs, Nevada has been the site of two fatal crashes.  The latest fatality occurred on Labor day.

Quote
Driver dies in fiery Silver Springs wreck - Preliminary investigation shows that both a red 1998 Peterbilt semi tractor-trailer car hauler and a gray 2000 Honda Accord were traveling southbound on U.S. 95A approaching the roundabout with U.S. 50.  The driver of the Peterbilt was unable to slow his vehicle due to suspected mechanical failure and the front of the Peterbilt struck the rear of the Honda, the release said. Both vehicles continued southbound and entered the raised decorative rock median of the roundabout. Both vehicles caught fire.  The driver of the Honda, who is currently unidentified due to the extent of burn damage, was pronounced deceased on scene.  https://www.nevadaappeal.com/news/2021/jun/07/driver-dies-fiery-silver-springs-wreck/

Um, unless I'm missing something, the roundabout had absolutely nothing to do with the fatal accident. He wouldn't have been able to stop for a red light and the other driver still would have died.

How are you so sure the light would have been red?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 08, 2021, 03:52:31 AM
The roundabout certainly sealed his fate. At least there is some hope with a signal.

I mean, seriously, if you're going full-speed towards a roundabout and your brakes just fail, what do you do? Best I can assume is to drive off the road, but that's sure to be one hell of a crash too.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 08, 2021, 07:29:54 AM
The roundabout certainly sealed his fate. At least there is some hope with a signal.

I mean, seriously, if you're going full-speed towards a roundabout and your brakes just fail, what do you do? Best I can assume is to drive off the road, but that's sure to be one hell of a crash too.
Crash looks mechanically survivable to me. It is a major fire that made it much worse. I assume rock installations in the center punctured gas tank from below.
And then there is an option of engine braking - at least for the truck.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 08, 2021, 10:59:54 AM
Of the roundabouts with multiple fatalities that i have found, there are either rocks or a retaining wall in the central island:

96th/Westfield roundabout in Carmel, IN
(https://i.imgur.com/5o1wg6a.png)
(3 fatalities at roundabout... all fatal crashes involved drivers striking the retaining wall in the central island)

Big Tree/South Park Ave. roundabout in Hamburg, NY
(https://i.imgur.com/oDMIOZv.jpg)
(SUV struck rocks in central island, flipped and caught fire)

Highway 95A and U.S. 50 roundabout in Silver Springs, Nevada
(https://i.imgur.com/l3Vfr5k.jpg)
(both fatal crashes involved drivers striking the rocks in the central island)
Title: Re: Crash prone 'modern roundabouts'
Post by: TheHighwayMan394 on September 08, 2021, 03:39:58 PM
The roundabout certainly sealed his fate. At least there is some hope with a signal.

What's the difference between this and, say, coming up behind a traffic jam on the freeway and the truck behind you can't stop? The traffic in front of you "sealed your fate".

In this particular example, I think blaming the roundabout in any way is a straw man. If it happened at a red light, no one would suggest the red light was at fault.
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on September 08, 2021, 04:01:07 PM
Maybe people shouldn't drive tractor-trailers with failing brakes? Just a thought.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 08, 2021, 06:07:53 PM
Maybe people shouldn't drive tractor-trailers with failing brakes? Just a thought.
While we're on this... People shouldn't commit crimes, start fires or get sick. Eliminating police, firefighters and healthcare should save a lot of money, so that actual engineers may be hired by DOTs.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on September 08, 2021, 07:01:58 PM
Maybe people shouldn't drive tractor-trailers with failing brakes? Just a thought.
While we're on this... People shouldn't commit crimes, start fires or get sick. Eliminating police, firefighters and healthcare should save a lot of money, so that actual engineers may be hired by DOTs.
A great example of a non sequitur.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 08, 2021, 07:39:36 PM
Maybe people shouldn't drive tractor-trailers with failing brakes? Just a thought.
While we're on this... People shouldn't commit crimes, start fires or get sick. Eliminating police, firefighters and healthcare should save a lot of money, so that actual engineers may be hired by DOTs.
A great example of a non sequitur.
Just missing a totally obvious link. But looks like I still need to explain.

It is easy to say "people shouldn't ..". But shit still happens - and a lot of things are done in anticipation that shit will happen and will hit the fan. 
Seatbelts, airbags, energy absorbing hoods - just examples engineered into most modern cars. Medians, shoulders, guardrails   on the road. Emergency exits, fire extinguishers, entire 911 system, so on so on.
Any engineer who actually earned a high school diploma should be able to ask "what would happen to my design if things go wrong?" Saying "people shouldnt..." is naiive at best, and should become outright criminal for PE holder.
Whoever designed that roundabout with a crash-enhancement island, apparently, failed to ask that question. Probably same person who thinks 4 second amber is excessive on traffic lights, though. And I don't believe people who deployed such designs and failed to learn from mistakes  should be ever allowed another chance.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 19, 2021, 11:44:04 AM
Someone started a youtube channel devoted to capturing the many crashes that occur at the Milwaukee Roundabout at Walker's Point.  Here is just some example of what you can expect to see on the channel:

(recut) The first car takes out a light pole, the second car takes out a police car - Crash #030

Is this the second time that poor tree got ran over? - Crash #037

How high did that wheel bounce? - Crash #034

It caught fire before it even landed - Crash #023

Motorcycle comes in hot and wipes out at the roundabout. Crash #007

They fail to yield and T-Bone a minivan! Crash #011
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on November 19, 2021, 02:01:50 PM
We should have a companion thread, "Crash Prone Signalized Intersections"

We could post dozens of videos a day.

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 19, 2021, 02:15:14 PM
We should have a companion thread, "Crash Prone Signalized Intersections"

We could post dozens of videos a day.



Go for it!  But keep in mind the crashes i just posted took place at the same Milwaukee roundabout over the course of a few months.  You should record what you believe is the most dangerous signalized intersection in your town for a few months and post all the crazy crashes.  Then we can compare all the crash carnage that occurred at each.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 19, 2021, 02:28:46 PM
At least 3 drivers lost their wheel while approaching this roundabout.  Gotta love the drivers who run off to retrieve their wheel!

Title: Re: Crash prone 'modern roundabouts'
Post by: CoreySamson on November 19, 2021, 04:51:56 PM
Consider this a soliloquy about driving on a roundabout for the first* time...

I’m scared about merging onto a roundabout (haven’t yet).
My  second roundabout (https://www.google.com/maps/@29.723876,-95.3910629,186m/data=!3m1!1e3) (first was the one directly south of it) I merged onto a couple months ago was extremely intimidating. I was trying to get from NB Hermann Park Drive to Montrose, but there was an immense amount of traffic going at least 25 mph (due to the oval shape of the roundabout, they didn't have to slow down as much, plus they had no obligation to stop or yield) coming from Main St NB around the roundabout, meaning I was stopped for at least a minute trying to find an opening to get onto it (the angle at which the traffic was coming at wasn't helping, either). When I was able to get into it, I was essentially forced to exit onto Main St NB, as I was in the right lane entering the roundabout and could not merge left without causing an accident due to the amount of cars and the difference between our speeds. Luckily it didn't really affect the route I planned in the long run.

Navigating that roundabout realized my fear of merging onto one. It very much ranks in my top 5 scariest moments while driving, somewhere between trying to navigate I-35 in Austin for the first time at night and almost getting sideswiped by a speeding car I didn't see on a slip lane. I don't know if it's because of Houston drivers or because of the geometry of the roundabout, but that event was scary. If I had been less conservative and tried to force my way onto Montrose, I could've caused a pretty bad accident.

(* Technically second, but the first one wasn't busy and only had two legs)
Title: Re: Crash prone 'modern roundabouts'
Post by: LilianaUwU on November 19, 2021, 04:56:57 PM
(* Technically second, but the first one wasn't busy and only had two legs)

A roundabout with two legs? What's the point of that?
Title: Re: Crash prone 'modern roundabouts'
Post by: CoreySamson on November 19, 2021, 05:08:33 PM
(* Technically second, but the first one wasn't busy and only had two legs)

A roundabout with two legs? What's the point of that?
Apparently it's relatively common. (https://www.aaroads.com/forum/index.php?topic=14869.0) The one I'm talking about  also serves a parking lot. (https://www.google.com/maps/@29.7214521,-95.3910077,318m/data=!3m1!1e3)
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on November 20, 2021, 01:29:33 PM
Consider this a soliloquy about driving on a roundabout for the first* time...

I’m scared about merging onto a roundabout (haven’t yet).
My  second roundabout (https://www.google.com/maps/@29.723876,-95.3910629,186m/data=!3m1!1e3) (first was the one directly south of it) I merged onto a couple months ago was extremely intimidating. I was trying to get from NB Hermann Park Drive to Montrose, but there was an immense amount of traffic going at least 25 mph (due to the oval shape of the roundabout, they didn't have to slow down as much, plus they had no obligation to stop or yield) coming from Main St NB around the roundabout, meaning I was stopped for at least a minute trying to find an opening to get onto it (the angle at which the traffic was coming at wasn't helping, either). When I was able to get into it, I was essentially forced to exit onto Main St NB, as I was in the right lane entering the roundabout and could not merge left without causing an accident due to the amount of cars and the difference between our speeds. Luckily it didn't really affect the route I planned in the long run.

Navigating that roundabout realized my fear of merging onto one. It very much ranks in my top 5 scariest moments while driving, somewhere between trying to navigate I-35 in Austin for the first time at night and almost getting sideswiped by a speeding car I didn't see on a slip lane. I don't know if it's because of Houston drivers or because of the geometry of the roundabout, but that event was scary. If I had been less conservative and tried to force my way onto Montrose, I could've caused a pretty bad accident.

(* Technically second, but the first one wasn't busy and only had two legs)

That isn't a modern roundabout, it's a traffic circle. Roundabouts aren't controlled by stop signs, and the circulatory road doesn't have yield signs, both of which this example has.

Also, it's on you for not being in the correct lane approaching the circle. If you want to turn left, you should be in the left lane approaching a multi-lane roundabout, the same way as you would be if you were approaching any other intersection. Roundabouts aren't designed for you to change lanes inside of them.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 20, 2021, 03:45:32 PM
I still maintain that there is a significant disconnect between how some drivers see roundabouts, and how engineers see roundabouts.

To an engineer, the modern roundabout is simply an intersection that has been twisted around a central island. Besides this, rules are the same: left turns from the left lane, right turns from the right lane, and so on.

But, to some drivers (very few, those who aren't familiar with roundabouts or cannot remember how they work), that doesn't seem to translate too well. To some, I still feel like roundabouts are actually seen as a one-way circle where, regardless of the total number of lanes, exiting cannot physically be done from the inside lanes, markings be-damned, and that perpetual circulation using the outside lane would be completely fine.
Title: Re: Crash prone 'modern roundabouts'
Post by: mukade on November 20, 2021, 03:48:51 PM
Hamilton County, Indiana has about 250 roundabouts, and the one that has had the most accidents is at Olio Road, Southeastern Parkway, and 136th St in Fishers. I love roundabouts, but I avoid this one unless I have no other option. That said, I would still rather have this as a roundabout than as a traffic light.

From my perspective as a driver is that 1) it carries a very high volume of traffic for a roundabout, 2) the traffic patterns at certain times of day cause long waits for some approaches, (much of it caused by the lack of traffic control on Olio Rd. to the south) 3) lanes rules are inconsistent and confusing. Supposedly work will be done in the next year or two to make it safer, but I believe that work will focus on pavement markings and signage improvements.

I would be interested what the opinions of the professionals are on what could be done to make this one safer.. 

Google Maps: https://www.google.com/maps/@39.9881723,-85.9194422,17.81z (https://www.google.com/maps/@39.9881723,-85.9194422,17.81z)
Article: http://www.fisherstos.com/the-most-dangerous-roundabout-in-hamilton-county-is-in-fishers/ (http://www.fisherstos.com/the-most-dangerous-roundabout-in-hamilton-county-is-in-fishers/)
Title: Re: Crash prone 'modern roundabouts'
Post by: bwana39 on November 20, 2021, 05:08:44 PM
I still maintain that there is a significant disconnect between how some drivers see roundabouts, and how engineers see roundabouts.

To an engineer, the modern roundabout is simply an intersection that has been twisted around a central island. Besides this, rules are the same: left turns from the left lane, right turns from the right lane, and so on.

But, to some drivers (very few, those who aren't familiar with roundabouts or cannot remember how they work), that doesn't seem to translate too well. To some, I still feel like roundabouts are actually seen as a one-way circle where, regardless of the total number of lanes, exiting cannot physically be done from the inside lanes, markings be-damned, and that perpetual circulation using the outside lane would be completely fine.

I honestly prefer sitting at a RED Light to doing a roundabout.

While they lessen T-bone accidents, they increase fender benders dramatically.

If you don't go through the same roundabout all the time, there is too much thinking required.
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on November 20, 2021, 05:15:05 PM
If a roundabout is more thinking than you're comfortable with doing, you need to turn in your keys, because you're not competent to drive a motor vehicle.
Title: Re: Crash prone 'modern roundabouts'
Post by: LilianaUwU on November 20, 2021, 05:18:54 PM
If a roundabout is more thinking than you're comfortable with doing, you need to turn in your keys, because you're not competent to drive a motor vehicle.

I mean, I don't even have a license and I can understand a roundabout. (My field of interests might be biased towards roads, though, which would explain it.)
Title: Re: Crash prone 'modern roundabouts'
Post by: Tom958 on November 20, 2021, 06:38:20 PM

That isn't a modern roundabout, it's a traffic circle. Roundabouts aren't controlled by stop signs, and the circulatory road doesn't have yield signs, both of which this example has.

It's not a traffic circle, either. It's a regular divided boulevard with one unusually large island put there for decorative purposes. If people misperceive it as a circle, roundabout or otherwise, then maybe the left turn access to Montrose that you were trying to get to should be closed off.

Also, it's a good idea to realize that sometimes it's better to abort a questionable move such as zipping across three lanes of Main Street traffic, do what's safest, and attempt to learn something from it. CoreySamson did it eventually, but better drivers will decide to do it more promptly. As it happens, turning right on Main, easing leftward. then turning left on Bissonet to get to Montrose is only a block longer and a lot safer if there's any traffic. Probably should make that the default route from Hermann Park to Montrose. Headed the other way, maybe Bissonet to Fannin or Caroline to Hermann Park.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 20, 2021, 06:42:53 PM
If a roundabout is more thinking than you're comfortable with doing, you need to turn in your keys, because you're not competent to drive a motor vehicle.

I generally agree, although signals are probably a hair easier to quickly process than a roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: Tom958 on November 20, 2021, 08:02:07 PM
Hamilton County, Indiana has about 250 roundabouts, and the one that has had the most accidents is at Olio Road, Southeastern Parkway, and 136th St in Fishers. I love roundabouts, but I avoid this one unless I have no other option. That said, I would still rather have this as a roundabout than as a traffic light.

From my perspective as a driver is that 1) it carries a very high volume of traffic for a roundabout, 2) the traffic patterns at certain times of day cause long waits for some approaches, (much of it caused by the lack of traffic control on Olio Rd. to the south) 3) lanes rules are inconsistent and confusing. Supposedly work will be done in the next year or two to make it safer, but I believe that work will focus on pavement markings and signage improvements.

I would be interested what the opinions of the professionals are on what could be done to make this one safer.. 

Google Maps: https://www.google.com/maps/@39.9881723,-85.9194422,17.81z (https://www.google.com/maps/@39.9881723,-85.9194422,17.81z)
Article: http://www.fisherstos.com/the-most-dangerous-roundabout-in-hamilton-county-is-in-fishers/ (http://www.fisherstos.com/the-most-dangerous-roundabout-in-hamilton-county-is-in-fishers/)

I'm not a professional, but...

The biggest problem I see here is with the overlapping paths of eastbound and southbound traffic. As a counterexample, look at the part of the circle where eastbound and northbound traffic cross. There's a small, rhombus-shaped overlap zone within which... eastbound traffic has two lanes, and it can see it has two lanes because of the solid lane lines both before and after the overlap zone and the dotted chicken feet lines within it. Northbound traffic can see that it has two lanes because of the solid lines; the chicken feet are barely visible because of the angle at which they cross the field of view. The paths of northbound and eastbound traffic cross; there is no weaving. This condition occurs four times at most four-leg multilane roundabouts and thus is familiar to Hamilton Countians.

For southbound and eastbound traffic at this roundabout, though, the overlap zone is too long due to the need to accommodate 136th Street. Rather than crossing as usual, eastbound and southbound traffic are forced into a two-lane bottleneck on the circular roadway, making it impossible for both movements to have two unobstructed lanes. The designers gave the two lanes to southbound traffic and a nasty surprise to eastbound traffic.

That article (http://www.fisherstos.com/the-most-dangerous-roundabout-in-hamilton-county-is-in-fishers/) is interesting and very well-written and informative. To me, it's obvious that the accident that caused that huge discussion was caused by the driver who continued around the circle in the right lane in defiance of the pavement markings. However, I think it's likely that the culprit had reason to believe that s/he was in the right due to common practice in the plentiful multilane roundabouts throughout the area.

So, how to fix it? Removing the 136th Street leg is probably necessary but not sufficient. The exit to southbound Olio Road needs to be moved outboard far enough to create the same sort of rhombus-shaped overlap zone as is found in four locations at typical four-leg roundabouts. A less-expensive alternative might be to install overhead signage that makes it abundantly clear to eastbound traffic that only the left lane leads to eastbound Southeastern Parkway. 

Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on November 20, 2021, 08:33:37 PM
If a roundabout is more thinking than you're comfortable with doing, you need to turn in your keys, because you're not competent to drive a motor vehicle.

I generally agree, although signals are probably a hair easier to quickly process than a roundabout.

Oh, I'll happily concede the point, and go so far as to say that, unlike a roundabout, as long as stoplights work properly and everyone follows them, they require near-zero thought from the driver. But there are a great deal of things that a driver can be asked to do that require way more thinking than a roundabout does, most of them require faster thinking than a roundabout does, and most of them have way more catastrophic outcomes if the wrong decision is made. Timing a merge in heavy, fast traffic with no acceleration lane is far more mentally taxing than a roundabout, because you have to parse the traffic flow and make sure you're clear ahead and behind you and do it at 70 mph instead of at a dead stop like at a roundabout.

So if you don't like roundabouts because "too much thinking is required", then too much thinking is required of you to drive a car, full stop. Take the bus.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 20, 2021, 08:49:11 PM
If a roundabout is more thinking than you're comfortable with doing, you need to turn in your keys, because you're not competent to drive a motor vehicle.
OK, let's see how fit you are.
Below is the schematic of a roundabout I drive through almost every day. You cannot see the far side because of large feature in the center. You're coming from the east and making left towards south. If it is not very clear, northern side has only 1 lane. Path A or path B?
(https://i.imgur.com/WxiSbAV.jpg)

Did it take you more than 3 seconds to answer? That's all  you have on the road
 
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on November 20, 2021, 09:46:32 PM
If a roundabout is more thinking than you're comfortable with doing, you need to turn in your keys, because you're not competent to drive a motor vehicle.
OK, let's see how fit you are.
Below is the schematic of a roundabout I drive through almost every day. You cannot see the far side because of large feature in the center. You're coming from the east and making left towards south. If it is not very clear, northern side has only 1 lane. Path A or path B?
(https://i.imgur.com/WxiSbAV.jpg)

Did it take you more than 3 seconds to answer? That's all  you have on the road
 

You forgot the markings and signage.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 20, 2021, 10:05:04 PM
If a roundabout is more thinking than you're comfortable with doing, you need to turn in your keys, because you're not competent to drive a motor vehicle.
OK, let's see how fit you are.
Below is the schematic of a roundabout I drive through almost every day. You cannot see the far side because of large feature in the center. You're coming from the east and making left towards south. If it is not very clear, northern side has only 1 lane. Path A or path B?
(https://i.imgur.com/WxiSbAV.jpg)

Did it take you more than 3 seconds to answer? That's all  you have on the road
 

You forgot the markings and signage.
There is nothing that would help with A/B selection. There is some signage in the northern approach, but you cannot see it it when you travel along red line.
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on November 21, 2021, 12:16:21 AM
Quote
Did it take you more than 3 seconds to answer?

Yes, but that's because you said "east" so I looked to the right side of the page and was trying to figure out what the red arrow was supposed to signify, because I have never seen anyone on this forum make a map with south on top. Your diagram also doesn't include the geometry that a properly-designed roundabout would that would indicate the proper travel path.

In any event, here's the MUTCD diagram for a roundabout like yours. Properly marked, the A path is pretty obviously the correct one.
(https://mutcd.fhwa.dot.gov/htm/2009r1r2/images/fig3c_04_1.gif)
Title: Re: Crash prone 'modern roundabouts'
Post by: Tom958 on November 21, 2021, 05:51:33 AM
OK, let's see how fit you are.
Below is the schematic of a roundabout I drive through almost every day. You cannot see the far side because of large feature in the center. You're coming from the east and making left towards south. If it is not very clear, northern side has only 1 lane. Path A or path B?

Either one is fine. It's the same as turning left at a signal or an unsignalized intersection.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on November 21, 2021, 08:30:17 AM
OK, let's see how fit you are.
Below is the schematic of a roundabout I drive through almost every day. You cannot see the far side because of large feature in the center. You're coming from the east and making left towards south. If it is not very clear, northern side has only 1 lane. Path A or path B?

Either one is fine. It's the same as turning left at a signal or an unsignalized intersection.
No.  Not if you are headed south, which he awkwardly put at the top of his map.

In any matter, Scott fleshed out what I was getting at.

Come to think of it, at least in the Northeast, moving to the outside of the roundabout to exit it is pretty well expected.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 21, 2021, 11:36:00 AM
OK, let's see how fit you are.
Below is the schematic of a roundabout I drive through almost every day. You cannot see the far side because of large feature in the center. You're coming from the east and making left towards south. If it is not very clear, northern side has only 1 lane. Path A or path B?

Either one is fine. It's the same as turning left at a signal or an unsignalized intersection.
No.  Not if you are headed south, which he awkwardly put at the top of his map.

In any matter, Scott fleshed out what I was getting at.

Come to think of it, at least in the Northeast, moving to the outside of the roundabout to exit it is pretty well expected.
Moreover, there is no guarantee that southern side has 2 exit lanes and one would be able to exit from inner lane at at all.
If you think about it, modern roundabout can be seen as several short lanes starting at center island and terminating at exit. So lane A just starts at that point and lane B is the one driver should continue in.

So, apparently roundabout requires more thinking than Scott could handle ...
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on November 21, 2021, 01:18:28 PM
What? The problem isn't with the roundabout, it's with your drawing.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 21, 2021, 01:23:18 PM
What? The problem isn't with the roundabout, it's with your drawing.
Once orientation of the drawing is sorted out (guilty as charged, I first draw the diagram with car coming in from the left, and then realized I may need that compass for description) everything relevant to the question is right there. Omitted signage doesn't help with dilemma.
You just chosen the wrong lane.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 21, 2021, 03:18:33 PM
Here is a real-life example of a problematic roundabout.

The image below is from Gig Harbor, Washington (Google Maps (https://www.google.com/maps/@47.3584223,-122.6125468,277m/data=!3m1!1e3)). Ignore the bottom roundabout, we are focusing on the top roundabout (the oval one).

Coming off the freeway from the right side of the image, there is no way to "turn left" across the overpass without changing lanes. Notice that the yellow chevrons markings and white edge extension markings lead you into the outside lane which then exits back onto the freeway. In order to turn left, you have to change lanes or make a very awkward sharp left move where that second inside lane forms near the top of the roundabout.

As a driver, this lane change is not signed. The roundabout signage on the off-ramp (https://goo.gl/maps/5LQyjPf4LjFHMzUY8) shows the left lane as taking you towards the overpass, yet that's incorrect.

The bottom roundabout had some unrelated issues and has been heavily modified since this picture was taken (10+ years ago).

(http://kpbj.com/drupalfiles/kpbj_images/2011/GigHarborRoundabouts_2406_lightbox.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: Tom958 on November 21, 2021, 06:01:16 PM
Here is a real-life example of a problematic roundabout.

Primitive as is would be, perhaps a sign that read

WA 16 EAST
Bremerton
KEEP LEFT

placed on the center island where it'll be prominent in a driver's field of view once s/he has entered the circle. With luck, drivers would wonder why WA 16 traffic needs to keep left while Borgen and Centerwood traffic doesn't.

plus a shield and banner assembly

EAST
WA 16
(diagonally up & left arrow)

near the end of the yellow-striped zone. Maybe make the yellow-striped zone narrower, too.
Title: Re: Crash prone 'modern roundabouts'
Post by: SEWIGuy on November 21, 2021, 07:17:08 PM
If you exit off the freeway to the far left lane, you most certainly can go left without changing lanes.  Am I missing something?

Also, has this roundabout actually been a problem?
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 21, 2021, 08:41:30 PM
has this roundabout actually been a problem?

The roundabout has been reconfigured at least twice since it opened in 2001, and rebuilt once. So, possibly.

If you exit off the freeway to the far left lane, you most certainly can go left without changing lanes.  Am I missing something?

Incorrect, the only lane that feeds the westbound exit is the left lane of the westbound entry (from the right in the below image). The markings (https://goo.gl/maps/CKrixW2w72S2nGaH8) also direct traffic into the outside lane and thus the entrance back onto WA-16:

(https://live.staticflickr.com/65535/51696334451_a642494159_o.png)
Borgen Blvd Roundabout Issue (https://flic.kr/p/2mLeeae) by Jacob Root (https://www.flickr.com/photos/62537709@N03/), on Flickr

Here is a real-life example of a problematic roundabout.

Primitive as is would be, perhaps a sign that read

WA 16 EAST
Bremerton
KEEP LEFT

placed on the center island where it'll be prominent in a driver's field of view once s/he has entered the circle. With luck, drivers would wonder why WA 16 traffic needs to keep left while Borgen and Centerwood traffic doesn't.

plus a shield and banner assembly

EAST
WA 16
(diagonally up & left arrow)

near the end of the yellow-striped zone. Maybe make the yellow-striped zone narrower, too.

I would not be opposed to that. Something is better than what exists now, which is basically for drivers to ignore the markings (problematic as noted in my sentence and link right before the above image).

The southbound Canterwood approach actually has writings in the lane (https://goo.gl/maps/chGxPYJrGinhJVYt8), that could be useful in the roundabout too.
Title: Re: Crash prone 'modern roundabouts'
Post by: Tom958 on November 21, 2021, 08:54:41 PM
If you exit off the freeway to the far left lane, you most certainly can go left without changing lanes.  Am I missing something?

Also, has this roundabout actually been a problem?

That was my take initially, but I trust jakeroot not to present a nonproblem as a problem.  :bigass:
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 21, 2021, 10:00:45 PM
If you exit off the freeway to the far left lane, you most certainly can go left without changing lanes.  Am I missing something?

Also, has this roundabout actually been a problem?

That was my take initially, but I trust jakeroot not to present a nonproblem as a problem.  :bigass:

I only brought it up because I got turned around in it recently, while out driving for Lyft. It's pretty close to where I live.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 09, 2021, 12:03:02 PM
This might be the smallest multi-lane turbo roundabout in the world. The middle bit of the roundabout is only about 20 feet in diameter.

It's near Coulon Park in Renton, WA, technically not a "public" road but it's publicly accessible.

(Overhead View (https://www.google.com/maps/@47.5024358,-122.2027631,79m/data=!3m1!1e3)) (Street View (https://goo.gl/maps/uxaEEPwB3qBmavts7))

(https://live.staticflickr.com/65535/51735782243_4cbc597e90_o.png)
Very Small Multilane Turbo Roundabout (https://flic.kr/p/2mPHpBz) by Jacob Root (https://www.flickr.com/photos/62537709@N03/), on Flickr
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 09, 2021, 12:41:20 PM
This might be the smallest multi-lane turbo roundabout in the world. The middle bit of the roundabout is only about 20 feet in diameter.

It's near Coulon Park in Renton, WA, technically not a "public" road but it's publicly accessible.

(Overhead View (https://www.google.com/maps/@47.5024358,-122.2027631,79m/data=!3m1!1e3)) (Street View (https://goo.gl/maps/uxaEEPwB3qBmavts7))

(https://live.staticflickr.com/65535/51735782243_4cbc597e90_o.png)
Very Small Multilane Turbo Roundabout (https://flic.kr/p/2mPHpBz) by Jacob Root (https://www.flickr.com/photos/62537709@N03/), on Flickr
As marijuana gets legalized, we may see more of these being implemented. Design under influence should be legal!
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 11, 2021, 12:02:34 PM
As marijuana gets legalized, we may see more of these being implemented. Design under influence should be legal!

It's not well signed either (no advanced warning, just yield signs and sharks teeth). I went through yesterday and almost no one was yielding or following the lane lines. It was basically an unsigned T-intersection. The lack of any visible markings in the middle does not help. Renton normally uses Botts Dots but this is private property so they used terrible apparently-non-reflective markings.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 02, 2022, 01:16:29 PM
There were 300 crashes reported in 2019 at the Homer Watson and Ottawa Street roundabout in Kitchener according to the 2020 Region of Waterloo collision report.  That's the highest number of crashes I've ever seen reported in a year at any roundabout in North America. 

(https://i.imgur.com/gGZtyKS.png)
https://www.regionofwaterloo.ca/en/living-here/resources/Documents/Future-Construction/2020-Annual-Collision-Report.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on September 02, 2022, 01:41:37 PM
There were 300 crashes reported in 2019 at the Homer Watson and Ottawa Street roundabout in Kitchener according to the 2020 Region of Waterloo collision report.  That's the highest number of crashes I've ever seen reported in a year at any roundabout in North America. 

Kitchener #1! :colorful:

I think the car traffic moves better through there with the roundabouts, but it can be pretty daunting the first time you use the dual 3-lane roundabouts. I can't even imagine trying to cross the 3-lane exits as a pedestrian! :-o

It was already one of the most crash-prone intersections in the Region, but I think going with 2-lane roundabouts would've been worth the increased congestion for better safety.

EDIT: They should've learned their lesson on 3-lane roundabouts after the Homer Watson/Block Line issues (which has had its third lane blocked for roughly a decade now!)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 02, 2022, 02:19:30 PM
There were 300 crashes reported in 2019 at the Homer Watson and Ottawa Street roundabout in Kitchener according to the 2020 Region of Waterloo collision report.  That's the highest number of crashes I've ever seen reported in a year at any roundabout in North America. 

Kitchener #1! :colorful:

I think the car traffic moves better through there with the roundabouts, but it can be pretty daunting the first time you use the dual 3-lane roundabouts. I can't even imagine trying to cross the 3-lane exits as a pedestrian! :-o

It was already one of the most crash-prone intersections in the Region, but I think going with 2-lane roundabouts would've been worth the increased congestion for better safety.

EDIT: They should've learned their lesson on 3-lane roundabouts after the Homer Watson/Block Line issues (which has had its third lane blocked for roughly a decade now!)
Three lane roundabout is pretty much a screw hammered in with a microscope.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on September 02, 2022, 02:21:20 PM
Did people, like, forget how to drive in 2019 or something?   :crazy:

Every single intersection on there went up 2018→2019 and then down 2019→2020.  And quite a few of them were by a significant amount.


(https://i.imgur.com/gGZtyKS.png)

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 02, 2022, 02:33:05 PM
Did people, like, forget how to drive in 2019 or something?   :crazy:

Every single intersection on there went up 2018→2019 and then down 2019→2020.  And quite a few of them were by a significant amount.



1
There was a slight reduction in traffic in 2020 due to a little-known public health condition. THat, probably, affected the number of crashes in 2020 (and, to a lesser extent, in 2021)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on September 02, 2022, 02:49:18 PM
There was a slight reduction in traffic in 2020 due to a little-known public health condition. THat, probably, affected the number of crashes in 2020 (and, to a lesser extent, in 2021)

1.  I recall having heard multiple times that crashes went up during the early days of the pandemic, not down.  Were roundabouts immune to this phenomenon?

2.  That does nothing to explain the dramatic jump from 2018 to 2019.

8% jump – Ottawa & Alpine (ramp)
52% jump – Clyde & Franklin
65% jump – Ottawa & Homer Watson
126% jump – Franklin & Main
241% jump – Dundas & Franklin
266% jump – Franklin & Pinebush
1000% jump – Franklin & Champlain
#DIV/0! – Erb & Landfill Gate 1
#DIV/0! – Erb & Landfill Gate 2

Those numbers don't strike you as strange?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 02, 2022, 03:56:43 PM
There was a slight reduction in traffic in 2020 due to a little-known public health condition. THat, probably, affected the number of crashes in 2020 (and, to a lesser extent, in 2021)

1.  I recall having heard multiple times that crashes went up during the early days of the pandemic, not down.  Were roundabouts immune to this phenomenon?
SOmetimes you have to look at the numbers closely. https://www.nhtsa.gov/press-releases/2020-fatality-data-show-increased-traffic-fatalities-during-pandemic and https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/813118
Similar fatality level in Jan-Feb 2020, down in Mar-May, UP in Jun-Dec.
Significant growth of non-buckled deaths (police didn't enforce things too much, so...). 
Another one from first hand experience - highways were much less crowded, but average speed went up by 10-20 MPH (above normal "speed limit +10-15 MPH").
Bottom line: no, people didn't forget how to drive in 2020; but they definitely got much less afraid of being pulled over.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on September 02, 2022, 04:41:43 PM
Bottom line: no, people didn't forget how to drive in 2020; but they definitely got much less afraid of being pulled over.

Wasn't my question to begin with.  I asked "did people forget how to drive in 2019".
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 02, 2022, 08:28:25 PM
Bottom line: no, people didn't forget how to drive in 2020; but they definitely got much less afraid of being pulled over.

Wasn't my question to begin with.  I asked "did people forget how to drive in 2019".

You kind of said both...

Did people, like, forget how to drive in 2019 or something?   :crazy:
I recall having heard multiple times that crashes went up during the early days of the pandemic, not down.

But you definitely didn't say anything about people forgetting to drive in 2020. Although you kind of implied that crashes went up in 2020.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 02, 2022, 08:52:39 PM
Bottom line: no, people didn't forget how to drive in 2020; but they definitely got much less afraid of being pulled over.

Wasn't my question to begin with.  I asked "did people forget how to drive in 2019".

You kind of said both...

Did people, like, forget how to drive in 2019 or something?   :crazy:
I recall having heard multiple times that crashes went up during the early days of the pandemic, not down.

But you definitely didn't say anything about people forgetting to drive in 2020. Although you kind of implied that crashes went up in 2020.
And at least on fatal accident side, 2020 and 2021 are much worse than 2018 and 2019. 2022  started high as well.
I wonder if that is enforcement or something else...
Title: Re: Crash prone 'modern roundabouts'
Post by: CtrlAltDel on September 05, 2022, 05:59:33 PM
Bottom line: no, people didn't forget how to drive in 2020; but they definitely got much less afraid of being pulled over.

Wasn't my question to begin with.  I asked "did people forget how to drive in 2019".

You kind of said both...

Did people, like, forget how to drive in 2019 or something?   :crazy:
I recall having heard multiple times that crashes went up during the early days of the pandemic, not down.

But you definitely didn't say anything about people forgetting to drive in 2020. Although you kind of implied that crashes went up in 2020.
And at least on fatal accident side, 2020 and 2021 are much worse than 2018 and 2019. 2022  started high as well.
I wonder if that is enforcement or something else...

I won't speak specifically for roundabouts but traffic fatalities did go up in 2020:

2019   36,355
2020   38,824   7.1%
2021   42,915   10.5%
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on September 05, 2022, 06:16:23 PM
Bottom line: no, people didn't forget how to drive in 2020; but they definitely got much less afraid of being pulled over.

Wasn't my question to begin with.  I asked "did people forget how to drive in 2019".

You kind of said both...

Did people, like, forget how to drive in 2019 or something?   :crazy:
I recall having heard multiple times that crashes went up during the early days of the pandemic, not down.

But you definitely didn't say anything about people forgetting to drive in 2020. Although you kind of implied that crashes went up in 2020.
And at least on fatal accident side, 2020 and 2021 are much worse than 2018 and 2019. 2022  started high as well.
I wonder if that is enforcement or something else...

I won't speak specifically for roundabouts but traffic fatalities did go up in 2020:

2019   36,355
2020   38,824   7.1%
2021   42,915   10.5%
That's the numbers I was referring to. I wonder if there was a similar increase in roundabouts out there... :pan:
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on September 06, 2022, 01:56:12 PM
Yet, in the table posted, every single roundabout listed had crashes go down from 2019 to 2020...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 05, 2022, 08:09:36 AM
Another fatal crash at the 96th & Westfield Blvd roundabout in Carmel.  This is now the 4th known fatality to occur at the roundabout since opening in 2005 and is one of the most deadly roundabouts in America. 

Coroner’s Office investigating death of Carmel man in single-car crash
https://readthereporter.com/coroners-office-investigating-death-of-carmel-man-in-single-car-crash/

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/RBfatalcrash1_zpsqnbnkfsm.png)

Quote
Police say two young men died early Monday morning at a roundabout in Carmel.  It happened around 3:00 am at Westfield Blvd. and 96th Street. Police found a Honda Accord in the center portion of the traffic roundabout. Police say the car crashed into the concrete retaining wall.
http://www.wthr.com/article/two-die-at-carmel-roundabout
https://safety.fhwa.dot.gov/intersection/roundabouts/fhwasa15072.pdf

Quote
A Carmel resident died March 17 after crashing a vehicle into a concrete barrier in the middle of a roundabout.  Police said Lambert Doll was driving a black 2014 Toyota Scion southbound on Westfield Boulevard and failed to negotiate the roundabout at 96th Street. The driver was taken to St.Vincent Hospital in Indianapolis and died a short time later.
http://currentincarmel.com/carmel-driver-dies-after-crashing-into-roundabouts-concrete-barrier
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 05, 2022, 08:24:15 AM
The majority of  Carmel roundabout fatalities that have occurred throughout the years involve drivers hitting rigid fixed objects in the central island of the roundabout.  In November 2021 a 35-year old man died at the 106th Street and Ditch Road roundabout after his Ford pickup struck the fountain structure in the middle of the roundabout causing the truck to roll over on its roof. 

35-year-old man dies after rollover crash Saturday morning in Carmel
https://www.indystar.com/story/news/2021/11/07/35-year-old-man-dies-after-crash-saturday-morning-carmel/6329786001/

The FHWA cited "fixed objects" as a lead crash type in their review of fatal crashes in Washington and Wisconsin accounting for 85% of fatal crashes at roundabouts.

Quote
FIXED OBJECTS
Fixed-object crash types were the most common crash types among the Injury A and B crashes at roundabouts in Washington and Wisconsin and were involved in 85 percent of fatal crashes at roundabouts. Of the 39 fatal fixed object crashes at roundabouts, 35 involved vehicles striking the curb. In some cases, multiple fixed objects were involved in a single crash. For example, a vehicle may have struck the curb first and a sign post second. Given that roundabouts rely on effective channelization using raised features such as splitter islands and central islands, as well as on signing to communicate legal movements and right-ofway to users, some fixed objects are inherent in the design of roundabouts and must be present in the design. Other objects that were hit, such as boulders, retaining walls, trees, and landscaping, may be optional at many roundabout locations. Based on these observations, the following sections summarize recommendations made about fixed objects.

Rigid Fixed Objects
Thoughtful placement of fixed objects is a basic principle of proper roadside design. In 2011, the American Association of State Highway and Transportation Officials (AASHTO) published an updated Roadside Design Guide (RDG), and the revisions to Chapter 10 on Roadside Safety in Urban or Restricted Environments represented a new perspective on roadside design in lower
speed and urban contexts.(7) Roundabouts share many of the characteristics discussed in this chapter of the RDG, and hence the updated guidance may be of value for roundabout design as well. In particular, as described in the RDG, it could be worthwhile to consider what may be “high risk”  locations for fixed objects unique to roundabouts, given the movements of traffic approaching, circulating, and leaving the vicinity of a roundabout.

A Review of Fatal and Severe Injury Crashes at Roundabouts PUBLICATION NO. FHWA-SA-15-072
https://safety.fhwa.dot.gov/intersection/roundabouts/fhwasa15072.pdf
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on November 05, 2022, 10:08:44 AM
Compared to national average traffic fatality rate of about 12 per 100,000 people, Carmel’s fatality rate is at two per 100,000.   Nearby Indianapolis has a rate of over 11 per 100,000.   The difference is the roundabouts.  You should focus on the amazing improvement in the overall fatality rate and not the exception caused by an impaired speeding driver.

https://usa.streetsblog.org/2022/09/22/we-couldnt-take-a-roundabout-out-if-we-wanted-to-an-interview-with-jim-brainerd-mayor-of-carmel-ind/

https://www.smartcitiesdive.com/news/roundabouts-carmel-in-mayor-jim-brainard-uscm/571074/
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 05, 2022, 11:15:05 AM
The FHWA cited "fixed objects" as a lead crash type in their review of fatal crashes in Washington and Wisconsin accounting for 85% of fatal crashes at roundabouts.

Wow, that's a much higher percentage than I'd have expected!

You should focus on the amazing improvement in the overall fatality rate and not the exception caused by an impaired speeding driver.

Actually, we should focus on what makes some roundabouts safer than others.  That, I think, is the biggest thing this thread has going for it.  It took a while for some of us to believe there were significant differences that could be identified, but |tradephoric| stuck with it in the face of our snarkiness, and I think most of us have come around to believing some roundabout designs are suboptimal.

Multilane roundabouts seem to have poorer safety record than single-lane roundabouts, for example, and we've explored the reasons that might be.  My main takeaway from looking into that is that not all conflict points in a multilane roundabout are actually sideswipes, as has often been touted as one of the key benefits of roundabout design.

Also, fixed objects in the center island appear to have an outsized impact on fatality rates.  The increased visibility comes at the cost of serious possible damage.

Then there's the question of ICD.  Is a larger ICD or a smaller ICD preferable?  Each has its advantages and disadvantages.  Is there a happy medium?

These are all important questions to ask.  And it helps to look at the most crash-prone roundabouts in order to identify their commonalities.
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on November 05, 2022, 12:54:15 PM
The more recent crash is still under investigation. The one from last year noted the driver was travelling at a "high speed." My problem with the tone of this thread has been the cherry picking from news accounts. It's always the roundabout's fault.
Is there another thread on these boards about any other specific type of intersection that records every serious accident that take place in them?

Pixel 7

Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 05, 2022, 01:08:00 PM
The more recent crash is still under investigation. The one from last year noted the driver was travelling at a "high speed." My problem with the tone of this thread has been the cherry picking from news accounts. It's always the roundabout's fault.

In fairness, cherry-picking the most crash-prone of modern roundabouts should be expected in a thread titled "Crash prone 'modern roundabouts'".

Yes, there has been an overall tone in this thread of using the most dangerous roundabouts as a way to dismiss any safety claims of all roundabouts in general, but I think we've generally gotten past that point.
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on November 05, 2022, 01:27:43 PM
I mean, in the most recent instance, it's not guaranteed that having the roundabout replaced with a flat cross intersection would have had a better outcome. If the guy was, for whatever reason, not interested in stopping before hitting a non-moving object, there's no guarantee he'd be interested in stopping before hitting another car in the intersection. At least if he hits a fountain or whatever he doesn't hurt anyone else.

But we don't have a "man hits other car in intersection" thread, because dog bites man is not news.
Title: Re: Crash prone 'modern roundabouts'
Post by: billpa on November 05, 2022, 01:31:44 PM
I mean cherry picking 'out' the bit about the driver operating at high speed.  That just might've played a role in what happened. 
If someone drives at a high speed on a standard road, fails to negotiate a curve, and then crashes into a tree we don't start a thread about roads that curve.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 05, 2022, 01:43:08 PM
I mean cherry picking 'out' the bit about the driver operating at high speed.  That just might've played a role in what happened. 
If someone drives at a high speed on a standard road, fails to negotiate a curve, and then crashes into a tree we don't start a thread about roads that curve.
(https://i.imgur.com/HnM8P18.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 05, 2022, 02:16:25 PM
A study examines 20 years of fatal crash data from the NHTSA to determine the deadliest intersections in the United States.  Here is a list of the 20 deadliest intersections in America:

(https://i.imgur.com/gTmfv9g.png)
https://www.fanglawfirm.com/the-deadliest-intersections-in-the-united-states/

Consider this. There are about 15,812,406 intersections in the continental United States. Less than 1 percent saw even one fatal crash (147,000). Only 1,828 had three or more fatal crashes – less than .01 percent.  As a result of our analysis, we determined that any intersection where at least three fatal crashes occurred should be considered a deadly intersection. A total of 1,828 intersections in the U.S. fit this criterion.

The roundabout at 96th and Westfield Blvd in Carmel has only been open since 2005 and has already seen 3 fatal crashes resulting in 4 fatalities.  Roundabouts are suppose to reduce fatal crashes by 90% yet a roundabout ends up in the top 0.01 percent most deadly intersections.  It just sounds like an interesting probability and statistics exam question.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 06, 2022, 10:30:00 AM
Compared to national average traffic fatality rate of about 12 per 100,000 people, Carmel’s fatality rate is at two per 100,000.   Nearby Indianapolis has a rate of over 11 per 100,000.   The difference is the roundabouts.  You should focus on the amazing improvement in the overall fatality rate and not the exception caused by an impaired speeding driver.

https://usa.streetsblog.org/2022/09/22/we-couldnt-take-a-roundabout-out-if-we-wanted-to-an-interview-with-jim-brainerd-mayor-of-carmel-ind/

https://www.smartcitiesdive.com/news/roundabouts-carmel-in-mayor-jim-brainard-uscm/571074/
Per-capita fatality rate isn't a good metric, especially when a single suburb is concerned. Looks like it isn't a good one even on the state level.
Normalize per vehicle-miles traveled as it is commonly done; take urban-suburban-rural into account; compare with similar towns in the area - now we're talking. For one, Indianapolis isn't very similar as it has quite a bit of interstate mileage with a lot of through traffic, while Carmel has only a small stretch in town (and there may be further fine print, like town services don't respond to crashes on  that stretch, and they are excluded from statistics)
Title: Re: Crash prone 'modern roundabouts'
Post by: algorerhythms on November 06, 2022, 11:52:07 AM
I mean, in the most recent instance, it's not guaranteed that having the roundabout replaced with a flat cross intersection would have had a better outcome. If the guy was, for whatever reason, not interested in stopping before hitting a non-moving object, there's no guarantee he'd be interested in stopping before hitting another car in the intersection. At least if he hits a fountain or whatever he doesn't hurt anyone else.

But we don't have a "man hits other car in intersection" thread, because dog bites man is not news.
There isn't really a type of intersection that is safe for a drunk driver going 100 mph. It sounds callous, but I'd rather have that driver dying by hitting the concrete barrier in the middle of the roundabout than that driver killing an innocent person.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 06, 2022, 12:29:56 PM
Here is a chart that lists the number of fatal crashes at the most deadly intersection in each state over a 20 year period (2000-2019).

(https://i.imgur.com/Rpc4GWH.png)

The roundabout at 96th and Westfield Blvd in Carmel doesn't have 20 full years of crash data (opened in 2005) but already has been the site of 3 fatal crashes resulting in 4 fatalities.  It would be the most deadly intersection in a number of states including Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, Delaware, Virginia, South Dakota, Nebraska, Utah, Montana, Alaska, and Hawaii.  I think many would be surprised to hear that an innocuous looking single-lane roundabout in Carmel, Indiana (the poster-child for safe intersections) would be the site of so many fatal crashes.  Looking deeper into why people are dying here, every so often you get someone that fails to negotiate the roundabout and crashes straight into the retaining wall in the central island.  As long as that retaining wall exists, there will be more deaths at this roundabout in the future. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 06, 2022, 12:33:41 PM
I mean, in the most recent instance, it's not guaranteed that having the roundabout replaced with a flat cross intersection would have had a better outcome. If the guy was, for whatever reason, not interested in stopping before hitting a non-moving object, there's no guarantee he'd be interested in stopping before hitting another car in the intersection. At least if he hits a fountain or whatever he doesn't hurt anyone else.

But we don't have a "man hits other car in intersection" thread, because dog bites man is not news.
There isn't really a type of intersection that is safe for a drunk driver going 100 mph. It sounds callous, but I'd rather have that driver dying by hitting the concrete barrier in the middle of the roundabout than that driver killing an innocent person.

Roundabouts are an effective design that reduces fatal crashes by 90%, yet they are also effective at killing off drunk drivers?  That's an impressive design if they can manage to do both.
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on November 06, 2022, 12:37:34 PM
Here is a chart that lists the number of fatal crashes at the most deadly intersection in each state over a 20 year period (2000-2019).

(https://i.imgur.com/Rpc4GWH.png)

Hey, let's all move to Wyoming, since it's so much safer there!

Wait, what do you mean it stopped being safe when everyone moved to Wyoming?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 06, 2022, 12:44:17 PM
Massachusetts has a population of nearly 7 million people yet over a 20 year period its most deadly intersection (SR-41 & Dublin Rd in Richmond) has been the site of only 2 fatal crashes.  The point is fatal crashes at (a specific) intersection is rare and having multiple fatal crashes over a 20 year period is exceedingly rare.  Once you get 3 fatal crashes you start asking yourself "WTF is wrong here?".
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on November 06, 2022, 01:02:17 PM
Maybe once you get 3 fatal crashes you ask yourself WTF is wrong here.

I look at that map, see 5 fatal crashes in Oklahoma, and nod my head going, "Ah, yes, because all of the intersections here have Oklahomans driving through them. Makes sense."
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on November 06, 2022, 01:17:19 PM
Maybe once you get 3 fatal crashes you ask yourself WTF is wrong here.

I look at that map, see 5 fatal crashes in Oklahoma, and nod my head going, "Ah, yes, because all of the intersections here have Oklahomans driving through them. Makes sense."

When there's 1 fatal accident every 4 years, it's tough to say it's really dangerous. Especially if (for example) one occurs because a truck lost its brakes, another because a drunk drove thru a red light, another because a pedestrian jaywalked, etc. If there's consistency, that's one thing. If it's a situation like the example above, it's just happenstance.
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on November 06, 2022, 01:22:50 PM
Compared to national average traffic fatality rate of about 12 per 100,000 people, Carmel’s fatality rate is at two per 100,000.   Nearby Indianapolis has a rate of over 11 per 100,000.   The difference is the roundabouts.  You should focus on the amazing improvement in the overall fatality rate and not the exception caused by an impaired speeding driver.

https://usa.streetsblog.org/2022/09/22/we-couldnt-take-a-roundabout-out-if-we-wanted-to-an-interview-with-jim-brainerd-mayor-of-carmel-ind/

https://www.smartcitiesdive.com/news/roundabouts-carmel-in-mayor-jim-brainard-uscm/571074/
Per-capita fatality rate isn't a good metric, especially when a single suburb is concerned. Looks like it isn't a good one even on the state level.
Normalize per vehicle-miles traveled as it is commonly done; take urban-suburban-rural into account; compare with similar towns in the area - now we're talking. For one, Indianapolis isn't very similar as it has quite a bit of interstate mileage with a lot of through traffic, while Carmel has only a small stretch in town (and there may be further fine print, like town services don't respond to crashes on  that stretch, and they are excluded from statistics)
For the record Carmel responds to accidents on I 465 many times each week, as part of I 465 is within Carmel's boundaries.  The US 31 freeway and Keystone Parkway are also inside Carmel's boundaries and generate their fair share of responses.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 06, 2022, 01:40:50 PM
Compared to national average traffic fatality rate of about 12 per 100,000 people, Carmel’s fatality rate is at two per 100,000.   Nearby Indianapolis has a rate of over 11 per 100,000.   The difference is the roundabouts.  You should focus on the amazing improvement in the overall fatality rate and not the exception caused by an impaired speeding driver.

https://usa.streetsblog.org/2022/09/22/we-couldnt-take-a-roundabout-out-if-we-wanted-to-an-interview-with-jim-brainerd-mayor-of-carmel-ind/

https://www.smartcitiesdive.com/news/roundabouts-carmel-in-mayor-jim-brainard-uscm/571074/
Per-capita fatality rate isn't a good metric, especially when a single suburb is concerned. Looks like it isn't a good one even on the state level.
Normalize per vehicle-miles traveled as it is commonly done; take urban-suburban-rural into account; compare with similar towns in the area - now we're talking. For one, Indianapolis isn't very similar as it has quite a bit of interstate mileage with a lot of through traffic, while Carmel has only a small stretch in town (and there may be further fine print, like town services don't respond to crashes on  that stretch, and they are excluded from statistics)
For the record Carmel responds to accidents on I 465 many times each week, as part of I 465 is within Carmel's boundaries.  The US 31 freeway and Keystone Parkway are also inside Carmel's boundaries and generate their fair share of responses.
Well, still interstate crashes do not dominate Carmel statistics. Fishers seem to get a bigger share.
Overall, this map doesn't show Carmel as a black hole in terms of serious events. Looks pretty much like other suburbs for me:
https://indympo.maps.arcgis.com/apps/dashboards/83d778fc586a4a43aba848a494b1cda3
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on November 06, 2022, 01:44:41 PM
Compared to national average traffic fatality rate of about 12 per 100,000 people, Carmel’s fatality rate is at two per 100,000.   Nearby Indianapolis has a rate of over 11 per 100,000.   The difference is the roundabouts.  You should focus on the amazing improvement in the overall fatality rate and not the exception caused by an impaired speeding driver.

https://usa.streetsblog.org/2022/09/22/we-couldnt-take-a-roundabout-out-if-we-wanted-to-an-interview-with-jim-brainerd-mayor-of-carmel-ind/

https://www.smartcitiesdive.com/news/roundabouts-carmel-in-mayor-jim-brainard-uscm/571074/
Per-capita fatality rate isn't a good metric, especially when a single suburb is concerned. Looks like it isn't a good one even on the state level.
Normalize per vehicle-miles traveled as it is commonly done; take urban-suburban-rural into account; compare with similar towns in the area - now we're talking. For one, Indianapolis isn't very similar as it has quite a bit of interstate mileage with a lot of through traffic, while Carmel has only a small stretch in town (and there may be further fine print, like town services don't respond to crashes on  that stretch, and they are excluded from statistics)
For the record Carmel responds to accidents on I 465 many times each week, as part of I 465 is within Carmel's boundaries.  The US 31 freeway and Keystone Parkway are also inside Carmel's boundaries and generate their fair share of responses.
Well, still interstate crashes do not dominate Carmel statistics. Fishers seem to get a bigger share.
Overall, this map doesn't show Carmel as a black hole in terms of serious events. Looks pretty much like other suburbs for me:
https://indympo.maps.arcgis.com/apps/dashboards/83d778fc586a4a43aba848a494b1cda3
Yes I 69 through Fishers is very congested and generates a lot of accidents. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 06, 2022, 01:51:49 PM
Compared to national average traffic fatality rate of about 12 per 100,000 people, Carmel’s fatality rate is at two per 100,000.   Nearby Indianapolis has a rate of over 11 per 100,000.   The difference is the roundabouts. You should focus on the amazing improvement in the overall fatality rate and not the exception caused by an impaired speeding driver.

https://usa.streetsblog.org/2022/09/22/we-couldnt-take-a-roundabout-out-if-we-wanted-to-an-interview-with-jim-brainerd-mayor-of-carmel-ind/

https://www.smartcitiesdive.com/news/roundabouts-carmel-in-mayor-jim-brainard-uscm/571074/
Per-capita fatality rate isn't a good metric, especially when a single suburb is concerned. Looks like it isn't a good one even on the state level.
Normalize per vehicle-miles traveled as it is commonly done; take urban-suburban-rural into account; compare with similar towns in the area - now we're talking. For one, Indianapolis isn't very similar as it has quite a bit of interstate mileage with a lot of through traffic, while Carmel has only a small stretch in town (and there may be further fine print, like town services don't respond to crashes on  that stretch, and they are excluded from statistics)
For the record Carmel responds to accidents on I 465 many times each week, as part of I 465 is within Carmel's boundaries.  The US 31 freeway and Keystone Parkway are also inside Carmel's boundaries and generate their fair share of responses.
Well, still interstate crashes do not dominate Carmel statistics. Fishers seem to get a bigger share.
Overall, this map doesn't show Carmel as a black hole in terms of serious events. Looks pretty much like other suburbs for me:
https://indympo.maps.arcgis.com/apps/dashboards/83d778fc586a4a43aba848a494b1cda3
Yes I 69 through Fishers is very congested and generates a lot of accidents.
And that directly contradicts highlighted statement above.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 06, 2022, 02:06:22 PM
It's confusing when CJW asks us to focus on the overall fatality rates and not the exception caused by an impaired speeding driver... when the overall fatality rate include crashes involving impaired speeding drivers.
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on November 06, 2022, 02:16:58 PM
It's confusing when CJW asks us to focus on the overall fatality rates and not the exception caused by an impaired speeding driver.

No, it's not.
Title: Re: Crash prone 'modern roundabouts'
Post by: UCFKnights on November 06, 2022, 07:55:16 PM
I mean, in the most recent instance, it's not guaranteed that having the roundabout replaced with a flat cross intersection would have had a better outcome. If the guy was, for whatever reason, not interested in stopping before hitting a non-moving object, there's no guarantee he'd be interested in stopping before hitting another car in the intersection. At least if he hits a fountain or whatever he doesn't hurt anyone else.

But we don't have a "man hits other car in intersection" thread, because dog bites man is not news.
There isn't really a type of intersection that is safe for a drunk driver going 100 mph. It sounds callous, but I'd rather have that driver dying by hitting the concrete barrier in the middle of the roundabout than that driver killing an innocent person.

Roundabouts are an effective design that reduces fatal crashes by 90%, yet they are also effective at killing off drunk drivers?  That's an impressive design if they can manage to do both.
Its not absurd though. If drunk driving causes people not to notice an intersection is there, and the intersection design is such that if you see the intersection and attempt to navigate it, its much safer, but if you fail to put any input into your vehicle and keep driving straight, its much less safe as the crash is 100% guaranteed.... then thats not far from expectations. And thats what we got with roundabouts.

When I used to drive around a lot at night, I saw many people completely fail to notice intersections, including traffic lights and stop signs. When they didn't notice them, they were always completely fine as it was a low traffic time, and going straight kept you on the road. If it were a roundabout, the crashes would have been guaranteed
Title: Re: Crash prone 'modern roundabouts'
Post by: SD Mapman on November 07, 2022, 08:05:19 AM
Here is a chart that lists the number of fatal crashes at the most deadly intersection in each state over a 20 year period (2000-2019).

(https://i.imgur.com/Rpc4GWH.png)

The roundabout at 96th and Westfield Blvd in Carmel doesn't have 20 full years of crash data (opened in 2005) but already has been the site of 3 fatal crashes resulting in 4 fatalities.  It would be the most deadly intersection in a number of states including Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, Delaware, Virginia, South Dakota, Nebraska, Utah, Montana, Alaska, and Hawaii.  I think many would be surprised to hear that an innocuous looking single-lane roundabout in Carmel, Indiana (the poster-child for safe intersections) would be the site of so many fatal crashes.  Looking deeper into why people are dying here, every so often you get someone that fails to negotiate the roundabout and crashes straight into the retaining wall in the central island.  As long as that retaining wall exists, there will be more deaths at this roundabout in the future. 

So we're going to be able to test this theory in real time over the next few years; the intersection of US 77 and NE 109 on the north side of Wahoo, NE had 5 fatal crashes in a year, and NDOT is planning to put a roundabout in.

https://journalstar.com/news/local/wahoo-roundabout-delayed-two-years-but-deadly-intersection-tamed-by-temporary-changes/article_af3322e6-2444-57eb-bc18-bf8161274cbe.html (https://journalstar.com/news/local/wahoo-roundabout-delayed-two-years-but-deadly-intersection-tamed-by-temporary-changes/article_af3322e6-2444-57eb-bc18-bf8161274cbe.html)

As someone who was a family friend of the three kids that died there (my wife's from the town), I hope you're wrong about big roundabout safety data, but we'll have to wait and see.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 07, 2022, 10:10:13 AM
Here is a chart that lists the number of fatal crashes at the most deadly intersection in each state over a 20 year period (2000-2019).

(https://i.imgur.com/Rpc4GWH.png)

The roundabout at 96th and Westfield Blvd in Carmel doesn't have 20 full years of crash data (opened in 2005) but already has been the site of 3 fatal crashes resulting in 4 fatalities.  It would be the most deadly intersection in a number of states including Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, Delaware, Virginia, South Dakota, Nebraska, Utah, Montana, Alaska, and Hawaii.  I think many would be surprised to hear that an innocuous looking single-lane roundabout in Carmel, Indiana (the poster-child for safe intersections) would be the site of so many fatal crashes.  Looking deeper into why people are dying here, every so often you get someone that fails to negotiate the roundabout and crashes straight into the retaining wall in the central island.  As long as that retaining wall exists, there will be more deaths at this roundabout in the future. 

So we're going to be able to test this theory in real time over the next few years; the intersection of US 77 and NE 109 on the north side of Wahoo, NE had 5 fatal crashes in a year, and NDOT is planning to put a roundabout in.

https://journalstar.com/news/local/wahoo-roundabout-delayed-two-years-but-deadly-intersection-tamed-by-temporary-changes/article_af3322e6-2444-57eb-bc18-bf8161274cbe.html (https://journalstar.com/news/local/wahoo-roundabout-delayed-two-years-but-deadly-intersection-tamed-by-temporary-changes/article_af3322e6-2444-57eb-bc18-bf8161274cbe.html)

As someone who was a family friend of the three kids that died there (my wife's from the town), I hope you're wrong about big roundabout safety data, but we'll have to wait and see.
Roundabouts are not intrinsically good or bad. It's lack of engineering skill and excess of heavy handed regulation that makes them bad. It's hard to say without looking at the map, traffic data, and actual design - and even then there are surprises.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 07, 2022, 11:26:52 AM
There isn't really a type of intersection that is safe for a drunk driver going 100 mph. It sounds callous, but I'd rather have that driver dying by hitting the concrete barrier in the middle of the roundabout than that driver killing an innocent person.

The catch in your argument, as has been pointed out up-thread:  a drunk driver going 100 mph straight through a roundabout has a 100% of hitting the island (and a non-zero chance of hiting an inncocent person nearby), whereas that same drunk driver going 100mph straight through a red light has a less-than-100% chance of hitting another vehicle.

The counter-argument to which, of course, is that the center island of a roundabout has a 0% chance of being an innocent person.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 07, 2022, 11:41:42 AM
So we're going to be able to test this theory in real time over the next few years; the intersection of US 77 and NE 109 on the north side of Wahoo, NE had 5 fatal crashes in a year, and NDOT is planning to put a roundabout in.

https://journalstar.com/news/local/wahoo-roundabout-delayed-two-years-but-deadly-intersection-tamed-by-temporary-changes/article_af3322e6-2444-57eb-bc18-bf8161274cbe.html (https://journalstar.com/news/local/wahoo-roundabout-delayed-two-years-but-deadly-intersection-tamed-by-temporary-changes/article_af3322e6-2444-57eb-bc18-bf8161274cbe.html)

As someone who was a family friend of the three kids that died there (my wife's from the town), I hope you're wrong about big roundabout safety data, but we'll have to wait and see.

The conceptual roundabout design for US 77 and NE 109 is showing a simple single-lane roundabout.  These are usually not too concerning in regards to total number of crashes.  Ideally the final design doesn't call for a bunch of fixed objects in the central island of the roundabout (rock walls, statues, retaining walls, etc.) as inevitably at some point a driver along Hwy 77 (which is a high-speed arterial) will misjudge the roundabout and fly right through the middle of the thing.  If there's a bunch of fixed objects to hit in the central island that's the scenario that can lead to a fatal roundabout crash. 

(https://gray-wowt-prod.cdn.arcpublishing.com/resizer/32CpLq1ntPxYpO9KTThNvfRjLFU=/980x0/smart/filters:quality(85)/cloudfront-us-east-1.images.arcpublishing.com/gray/GHYOPZKF7BHORBXBQRVV2SWSBY.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 07, 2022, 12:20:14 PM
There isn't really a type of intersection that is safe for a drunk driver going 100 mph. It sounds callous, but I'd rather have that driver dying by hitting the concrete barrier in the middle of the roundabout than that driver killing an innocent person.

The catch in your argument, as has been pointed out up-thread:  a drunk driver going 100 mph straight through a roundabout has a 100% of hitting the island (and a non-zero chance of hiting an inncocent person nearby), whereas that same drunk driver going 100mph straight through a red light has a less-than-100% chance of hitting another vehicle.

The counter-argument to which, of course, is that the center island of a roundabout has a 0% chance of being an innocent person.
Counter counter argument is soft sand in the island may reduce crash severity...
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on November 07, 2022, 12:27:59 PM
If people keep crashing into a roundabout at high speeds, then it would make sense to add a speed bump or rumble strips approaching the roundabout.

That being said, a design where a drunk driver is killed but no innocent victims are harmed is a success.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 07, 2022, 12:42:40 PM
That being said, a design where a drunk driver is killed but no innocent victims are harmed is a success.

Again... counter-argument... a design where neither person is harmed is a bigger success.  And a stoplight intersection has a greater chance of that happening.
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on November 07, 2022, 12:46:16 PM
We should create an intersection where, if a drunk driver passes straight through, they get teleported to a pocket dimension where they are forced to read this thread in its entirety, over and over.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 07, 2022, 12:51:18 PM
We should create an intersection where, if a drunk driver passes straight through, they get teleported to a pocket dimension where they are forced to read this thread in its entirety, over and over.
I have seen one such spot on masspike. It is signed as "runaway truck ramp", but any vehicle with a drunk driver would get stuck until help arrives....
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on November 07, 2022, 10:45:01 PM
  And a stoplight intersection has a greater chance of that happening.

Citation?
Title: Re: Crash prone 'modern roundabouts'
Post by: SD Mapman on November 07, 2022, 11:18:34 PM
So we're going to be able to test this theory in real time over the next few years; the intersection of US 77 and NE 109 on the north side of Wahoo, NE had 5 fatal crashes in a year, and NDOT is planning to put a roundabout in.

https://journalstar.com/news/local/wahoo-roundabout-delayed-two-years-but-deadly-intersection-tamed-by-temporary-changes/article_af3322e6-2444-57eb-bc18-bf8161274cbe.html (https://journalstar.com/news/local/wahoo-roundabout-delayed-two-years-but-deadly-intersection-tamed-by-temporary-changes/article_af3322e6-2444-57eb-bc18-bf8161274cbe.html)

As someone who was a family friend of the three kids that died there (my wife's from the town), I hope you're wrong about big roundabout safety data, but we'll have to wait and see.

The conceptual roundabout design for US 77 and NE 109 is showing a simple single-lane roundabout.  These are usually not too concerning in regards to total number of crashes.  Ideally the final design doesn't call for a bunch of fixed objects in the central island of the roundabout (rock walls, statues, retaining walls, etc.) as inevitably at some point a driver along Hwy 77 (which is a high-speed arterial) will misjudge the roundabout and fly right through the middle of the thing.  If there's a bunch of fixed objects to hit in the central island that's the scenario that can lead to a fatal roundabout crash. 

(https://gray-wowt-prod.cdn.arcpublishing.com/resizer/32CpLq1ntPxYpO9KTThNvfRjLFU=/980x0/smart/filters:quality(85)/cloudfront-us-east-1.images.arcpublishing.com/gray/GHYOPZKF7BHORBXBQRVV2SWSBY.jpg)
We'll see what they actually build (I think that was the plastic plan that never got built), the plan now is to build it as part of the 77 widening project in a couple years. If I remember right they modified it to neck you down to one lane on 77 before 109 (it's two-lane east of Wahoo), but when there's four lanes on both sides of the intersection I don't know if they'll neck it down or not. This will be the first roundabout on the Nebraska Expressway system to my knowledge, so there's going to be a high percentage of through traffic.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 08, 2022, 10:08:47 AM

That being said, a design where a drunk driver is killed but no innocent victims are harmed is a success.

Again... counter-argument... a design where neither person is harmed is a bigger success.  And a stoplight intersection has a greater chance of that happening.

Citation?

I thought it was obvious.

If no other vehicle is actually in front of the driver, then he simply blows through the red light at 100 mph with no incident.  And if this happens at, say, 2:30 AM, then those are pretty good odds.

If no other vehicle is actually in front of the driver, then he nevertheless plows straight into the roundabout's central island.  It doesn't matter if it's 2:30 PM or 2:30 AM–there's going to be an injury.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on November 08, 2022, 02:50:06 PM

That being said, a design where a drunk driver is killed but no innocent victims are harmed is a success.

Again... counter-argument... a design where neither person is harmed is a bigger success.  And a stoplight intersection has a greater chance of that happening.

Citation?

I thought it was obvious.

If no other vehicle is actually in front of the driver, then he simply blows through the red light at 100 mph with no incident.  And if this happens at, say, 2:30 AM, then those are pretty good odds.

If no other vehicle is actually in front of the driver, then he nevertheless plows straight into the roundabout's central island.  It doesn't matter if it's 2:30 PM or 2:30 AM–there's going to be an injury.

So your citation is a ridiculous made up example?

What about the time the driver blows through the intersection but there are multiple other cars already in it?

Like this crash that killed 6 at 1:40pm



Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 08, 2022, 03:26:09 PM
So your citation is a ridiculous made up example?

What about the time the driver blows through the intersection but there are multiple other cars already in it?

Like this crash that killed 6 at 1:40pm

I mean, I guess I could post a video about an incident in which nothing happened, but you know what, nobody makes news stories about that.

OK, you want a non-hypothetical, non-made-up example?  I've personally blown through a red light while crossing Michigan Avenue just north of downtown Chicago.  I had grown up in a small town, was a bit overwhelmed by city traffic, and neglected to notice the red light.  You know what happened?  Nothing.  I think a CTA bus honked at me, and that was it.  Forgive me if I can't link to a news story about it.  So yeah, I ran straight through a red light at a busy intersection in one of the nation's most crowded cities, and there were zero injuries.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 08, 2022, 03:29:03 PM

That being said, a design where a drunk driver is killed but no innocent victims are harmed is a success.

Again... counter-argument... a design where neither person is harmed is a bigger success.  And a stoplight intersection has a greater chance of that happening.

Citation?

I thought it was obvious.

If no other vehicle is actually in front of the driver, then he simply blows through the red light at 100 mph with no incident.  And if this happens at, say, 2:30 AM, then those are pretty good odds.

If no other vehicle is actually in front of the driver, then he nevertheless plows straight into the roundabout's central island.  It doesn't matter if it's 2:30 PM or 2:30 AM–there's going to be an injury.

So your citation is a ridiculous made up example?

What about the time the driver blows through the intersection but there are multiple other cars already in it?

Like this crash that killed 6 at 1:40pm

1. "Chance" is not certainty.
2. Cars on the side of roundabout where uncontrollable vehicle comes from would still be t-boned, and thrown into a central feature
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on November 08, 2022, 03:33:56 PM
2. Cars on the side of roundabout where uncontrollable vehicle comes from would still be t-boned, and thrown into a central feature

One car, yes, not multiple.

I mean, I guess I could post a video about an incident in which nothing happened, but you know what, nobody makes news stories about that.

OK, you want a non-hypothetical, non-made-up example?  I've personally blown through a red light while crossing Michigan Avenue just north of downtown Chicago.  I had grown up in a small town, was a bit overwhelmed by city traffic, and neglected to notice the red light.  You know what happened?  Nothing.  I think a CTA bus honked at me, and that was it.  Forgive me if I can't link to a news story about it.  So yeah, I ran straight through a red light at a busy intersection in one of the nation's most crowded cities, and there were zero injuries.

More anecdotes.

Your statement "a stoplight intersection has a greater chance of that happening" implied facts behind it. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on November 08, 2022, 03:35:43 PM
Your statement "a stoplight intersection has a greater chance of that happening" implied facts behind it. 

All other things being equal...

Fact:  an out-of-control vehicle heading for a roundabout's central island will hit that central island.

Fact:  an out-of-control vehicle heading for a regular intersection will not necessary hit any other vehicle.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on November 09, 2022, 08:18:13 AM
2. Cars on the side of roundabout where uncontrollable vehicle comes from would still be t-boned, and thrown into a central feature

One car, yes, not multiple.

James knows exactly how many vehicles will get t-boned when a driver blows through a roundabout at 100 mph.  One car, yes, but never two.


Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 09, 2022, 10:24:55 AM
2. Cars on the side of roundabout where uncontrollable vehicle comes from would still be t-boned, and thrown into a central feature

One car, yes, not multiple.

SOmething like this has a great potential for being a multi-vehicle event:
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on November 09, 2022, 10:25:38 AM
Yet, in the table posted, every single roundabout listed had crashes go down from 2019 to 2020...

Very easily explained by the fact that traffic overall went way down in 2020.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 09, 2022, 10:35:33 AM
Yet, in the table posted, every single roundabout listed had crashes go down from 2019 to 2020...

Very easily explained by the fact that traffic overall went way down in 2020.
possibly  adding even steeper reduction of long haul traffic, with non-locals more likely to run into a problem with unexpected road configurations.
Title: Re: Crash prone 'modern roundabouts'
Post by: skluth on November 09, 2022, 12:03:01 PM
So your citation is a ridiculous made up example?

What about the time the driver blows through the intersection but there are multiple other cars already in it?

Like this crash that killed 6 at 1:40pm

I mean, I guess I could post a video about an incident in which nothing happened, but you know what, nobody makes news stories about that.

OK, you want a non-hypothetical, non-made-up example?  I've personally blown through a red light while crossing Michigan Avenue just north of downtown Chicago.  I had grown up in a small town, was a bit overwhelmed by city traffic, and neglected to notice the red light.  You know what happened?  Nothing.  I think a CTA bus honked at me, and that was it.  Forgive me if I can't link to a news story about it.  So yeah, I ran straight through a red light at a busy intersection in one of the nation's most crowded cities, and there were zero injuries.

Congratulations on surviving. I've done the same in St Louis and I actually lived there at the time. It's called dumb luck. My Uncle Jimmy was just out of high school when he was thrown from his car in an accident; his car was crushed and he would have died had he worn his seat belt. He used this as an excuse to never wear his seat belt as he claimed that seat belts killed people. Statistics say he was lucky and was the exception to the norm. Your argument is meaningless unless you can cite evidence that your statement is true. Anecdotes alone mean nothing and will be ignored.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on November 09, 2022, 12:43:40 PM
So your citation is a ridiculous made up example?

What about the time the driver blows through the intersection but there are multiple other cars already in it?

Like this crash that killed 6 at 1:40pm

I mean, I guess I could post a video about an incident in which nothing happened, but you know what, nobody makes news stories about that.

OK, you want a non-hypothetical, non-made-up example?  I've personally blown through a red light while crossing Michigan Avenue just north of downtown Chicago.  I had grown up in a small town, was a bit overwhelmed by city traffic, and neglected to notice the red light.  You know what happened?  Nothing.  I think a CTA bus honked at me, and that was it.  Forgive me if I can't link to a news story about it.  So yeah, I ran straight through a red light at a busy intersection in one of the nation's most crowded cities, and there were zero injuries.

Congratulations on surviving. I've done the same in St Louis and I actually lived there at the time. It's called dumb luck. My Uncle Jimmy was just out of high school when he was thrown from his car in an accident; his car was crushed and he would have died had he worn his seat belt. He used this as an excuse to never wear his seat belt as he claimed that seat belts killed people. Statistics say he was lucky and was the exception to the norm. Your argument is meaningless unless you can cite evidence that your statement is true. Anecdotes alone mean nothing and will be ignored.
Evidence of what exactly do you want?
That high speed red light violation can be survivable with some luck? There are some examples above, so it is proven by presented  evidence. Pretty obvious that less traffic means better chances.
Evidence of hard feature in vehicle path greatly reduces survival chance? Again, fairly obvious. If you notice, they rarely - if ever - use concrete jersey barriers across the traffic path.  Exception may be something like T intersection at the edge of a cliff, where crash into concrete may be more survivable than 100s feet fall.
Most concrete barriers are parallel or low angle for lane separation and lane drop, and tested to 15 degree impact. Barriers across traffic are usually collapsible -  barrels, metal rail, some frames - to give driver a better chance in case of a crash.

If you see many opposing examples on the road, this is because your local DOT is not doing things right. And hard feature in the roundabout is against these approaches...
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on November 09, 2022, 05:46:18 PM
Hmm. I wonder what would happen if you put a freeway-style cable barrier in a loop around the center island of a roundabout? (Probably won't work, because those probably aren't designed to catch a vehicle hitting it at a 90° angle, but...)

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on November 10, 2022, 01:30:56 AM
Yet, in the table posted, every single roundabout listed had crashes go down from 2019 to 2020...

Very easily explained by the fact that traffic overall went way down in 2020.

The context was that fatalities increased from 2019 to 2020 despite total traffic dropping.
Title: Re: Crash prone 'modern roundabouts'
Post by: webny99 on November 11, 2022, 08:36:02 AM
Yet, in the table posted, every single roundabout listed had crashes go down from 2019 to 2020...

Very easily explained by the fact that traffic overall went way down in 2020.

The context was that fatalities increased from 2019 to 2020 despite total traffic dropping.

However, that was in total, not specific to roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: interstatefan990 on February 14, 2023, 02:37:36 PM
Does anyone else think this "roundabout" (https://goo.gl/maps/GxpWqjvusKucMTEv7) could use better signage and/or design?
Title: Re: Crash prone 'modern roundabouts'
Post by: cjw2001 on February 14, 2023, 03:54:08 PM
Does anyone else think this "roundabout" (https://goo.gl/maps/GxpWqjvusKucMTEv7) could use better signage and/or design?
This thread is about modern roundabouts, and that definitely isn't one.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 14, 2023, 05:38:15 PM
Does anyone else think this "roundabout" (https://goo.gl/maps/GxpWqjvusKucMTEv7) could use better signage and/or design?
This thread is about modern roundabouts, and that definitely isn't one.

That may be his point, though. It's definitely an older traffic-circle design from the early half of the 20th century and probably could use better signage and potentially overall design.

I think modifying that circle into a roundabout (improving approach angles, center island location adjustment) and maybe installing a second roundabout at Marvin / Calf Pasture Beach could make for a great double roundabout intersection.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 14, 2023, 05:51:28 PM
Does anyone else think this "roundabout" (https://goo.gl/maps/GxpWqjvusKucMTEv7) could use better signage and/or design?
This thread is about modern roundabouts, and that definitely isn't one.

That may be his point, though. It's definitely an older traffic-circle design from the early half of the 20th century and probably could use better signage and potentially overall design.

I think modifying that circle into a roundabout (improving approach angles, center island location adjustment) and maybe installing a second roundabout at Marvin / Calf Pasture Beach could make for a great double roundabout intersection.
I would say it could use some design to begin with. Looks like a low traffic area, so its unclear why they bothered to do anything at all. Someone had to defend a thesis?
Title: Re: Crash prone 'modern roundabouts'
Post by: interstatefan990 on February 14, 2023, 06:29:07 PM
Does anyone else think this "roundabout" (https://goo.gl/maps/GxpWqjvusKucMTEv7) could use better signage and/or design?
This thread is about modern roundabouts, and that definitely isn't one.

That may be his point, though. It's definitely an older traffic-circle design from the early half of the 20th century and probably could use better signage and potentially overall design.

I think modifying that circle into a roundabout (improving approach angles, center island location adjustment) and maybe installing a second roundabout at Marvin / Calf Pasture Beach could make for a great double roundabout intersection.

Agreed. And yeah, I just think it's confusing as heck because it's a normal traffic circle except it functions almost as a reverse roundabout, because traffic inside the circle yields to traffic entering the circle, save for the stop sign on one of the Gregory Boulevard approaches. There's also no yield sign at all for traffic on Marvin St continuing straight on to 5th St, crossing Gregory Boulevard in the process.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 14, 2023, 06:35:20 PM
I would say it could use some design to begin with. Looks like a low traffic area, so its unclear why they bothered to do anything at all. Someone had to defend a thesis?

Seems to have been built in the 1920s, maybe earlier. I'm not sure how traffic engineering worked back then, if I'm honest.

...And yeah, I just think it's confusing as heck because it's a normal traffic circle except it functions almost as a reverse roundabout, because traffic inside the circle yields to traffic entering the circle, save for the stop sign on one of the Gregory Boulevard approaches. There's also no yield sign at all for traffic on Marvin St continuing straight on to 5th St, crossing Gregory Boulevard in the process.

I assume traffic only yields inside the circle to traffic entering from Marvin? The other approaches are either stop signs entering the circle or no signs at all.

The obvious solution is just to install yield signs at all of the entries with supplemental "to traffic on left" signage.
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on February 14, 2023, 06:48:55 PM
Also I have to laugh at the way 89 Gregory Blvd. there is blurred out, which caused me to Google it to see if there's anything special about it (there's not), which I wouldn't have done if they had left it unblurred.
Title: Re: Crash prone 'modern roundabouts'
Post by: interstatefan990 on February 14, 2023, 06:49:16 PM
I assume traffic only yields inside the circle to traffic entering from Marvin? The other approaches are either stop signs entering the circle or no signs at all.

Well, "yield" in the sense that by law you have to let other cars go first even if there's no sign. If you were traveling in the direction that the camera is pointed here (https://goo.gl/maps/qBRBSdoCUZxHDDgZ7), I assume you'd have to yield to traffic coming from your right.

The obvious solution is just to install yield signs at all of the entries with supplemental "to traffic on left" signage.

Yes, that seems like the most cost-effective solution if converting it into a traditional roundabout isn't an option. I have to admit, I did get honked at for slowing down when I first drove through here going southbound on Gregory, as I wasn't sure if there was a missing YIELD sign on one of the approaches, or if I was supposed to yield at all.
Title: Re: Crash prone 'modern roundabouts'
Post by: interstatefan990 on February 14, 2023, 06:51:40 PM
Also I have to laugh at the way 89 Gregory Blvd. there is blurred out, which caused me to Google it to see if there's anything special about it (there's not), which I wouldn't have done if they had left it unblurred.

Right? This isn't Germany.
Title: Re: Crash prone 'modern roundabouts'
Post by: CovalenceSTU on February 14, 2023, 07:05:02 PM
On the subject of modern roundabouts, I can say from experience that the biggest problem with the US 101/OR 202 roundabout (mentioned towards the start of the thread) is that the 101S entrance/exit are too close together, meaning that unless you signal left people frequently don't react fast enough to stop:

(https://i.imgur.com/8gw9mTd.png)(https://i.imgur.com/jtbHKRZ.png)(https://i.imgur.com/NKx8mVI.png)

At 20mph (29-30 ft/s) that means that 101S has a full second less to react vs. 101N, and only around 2 seconds to see a car going around and stop. The solution would be to move the 101S exit farther back in the roundabout, which would add that ≈1 second of reaction time (and also extend the solid line, there's functionally no reason for traffic in the circle to cross to the right lane). MS Paint mockup of what it could look like:

(https://i.imgur.com/iZEsCcV.png)(https://i.imgur.com/MoenclM.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 14, 2023, 07:12:02 PM
I assume traffic only yields inside the circle to traffic entering from Marvin? The other approaches are either stop signs entering the circle or no signs at all.

Well, "yield" in the sense that by law you have to let other cars go first even if there's no sign. If you were traveling in the direction that the camera is pointed here (https://goo.gl/maps/qBRBSdoCUZxHDDgZ7), I assume you'd have to yield to traffic coming from your right.

True. Without signage, roundabouts would always require circulating traffic to yield as entering traffic is 'from the right' and by law has right-of-way.

The obvious solution is just to install yield signs at all of the entries with supplemental "to traffic on left" signage.

Yes, that seems like the most cost-effective solution if converting it into a traditional roundabout isn't an option. I have to admit, I did get honked at for slowing down when I first drove through here going southbound on Gregory, as I wasn't sure if there was a missing YIELD sign on one of the approaches, or if I was supposed to yield at all.

I would have instinctively slowed and yielded as well.

It should be noted that satellite imagery shows edge extension (usually yield) markings along the entrances from both Gregory and Marvin, despite both of these ostensibly having right-of-way in street view imagery. Curious if something has changed lately that isn't shown in street view.
Title: Re: Crash prone 'modern roundabouts'
Post by: interstatefan990 on February 14, 2023, 07:20:43 PM
It should be noted that satellite imagery shows edge extension (usually yield) markings along the entrances from both Gregory and Marvin, despite both of these ostensibly having right-of-way in street view imagery. Curious if something has changed lately that isn't shown in street view.

What's even more interesting is when I drove through, I think I remember a thin solid white line across one of the Gregory entrances, continuing out from the white line on the top of the yellow striped area that delineates the circle. Don't quote me on that, though. Classic CT road design.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 14, 2023, 07:52:08 PM
On the subject of modern roundabouts, I can say from experience that the biggest problem with the US 101/OR 202 roundabout (mentioned towards the start of the thread) is that the 101S entrance/exit are too close together, meaning that unless you signal left people frequently don't react fast enough to stop:

...
At 20mph (29-30 ft/s) that means that 101S has a full second less to react vs. 101N, and only around 2 seconds to see a car going around and stop. The solution would be to move the 101S exit farther back in the roundabout, which would add that ≈1 second of reaction time (and also extend the solid line, there's functionally no reason for traffic in the circle to cross to the right lane). MS Paint mockup of what it could look like:

This is...interesting.

Generally, roundabout exits are meant to be slightly higher speed than entrances, but still have some deflection to ensure traffic doesn't exit so fast as to decrease the chance of yielding to crossing pedestrians.

Your design does have a much flatter exit (meaning, higher speed) than present, and does have the added benefit of distancing the exit and entrance enough that traffic coming from 101 would have greater warning of traffic continuing to circulate, and would be able to keep moving more often. But that may have a detrimental impact on traffic coming from 202, who now has to contend with traffic entering at a higher and more continuous rate.

I would also argue that most roundabouts, particularly single-lane roundabouts, don't have exceptional distance between the exit and entrance legs. I.e., this is a fairly normal issue for most roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 14, 2023, 09:01:57 PM
On the subject of modern roundabouts, I can say from experience that the biggest problem with the US 101/OR 202 roundabout (mentioned towards the start of the thread) is that the 101S entrance/exit are too close together, meaning that unless you signal left people frequently don't react fast enough to stop:

...
At 20mph (29-30 ft/s) that means that 101S has a full second less to react vs. 101N, and only around 2 seconds to see a car going around and stop. The solution would be to move the 101S exit farther back in the roundabout, which would add that ≈1 second of reaction time (and also extend the solid line, there's functionally no reason for traffic in the circle to cross to the right lane). MS Paint mockup of what it could look like:

This is...interesting.

Generally, roundabout exits are meant to be slightly higher speed than entrances, but still have some deflection to ensure traffic doesn't exit so fast as to decrease the chance of yielding to crossing pedestrians.

Your design does have a much flatter exit (meaning, higher speed) than present, and does have the added benefit of distancing the exit and entrance enough that traffic coming from 101 would have greater warning of traffic continuing to circulate, and would be able to keep moving more often. But that may have a detrimental impact on traffic coming from 202, who now has to contend with traffic entering at a higher and more continuous rate.

I would also argue that most roundabouts, particularly single-lane roundabouts, don't have exceptional distance between the exit and entrance legs. I.e., this is a fairly normal issue for most roundabouts.
Pedestrian crosswalks don't belong within at least 100' from roundabout. Of course, an urge to use a cool design pushes safety to a back burner...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on February 15, 2023, 12:41:23 AM
On the subject of modern roundabouts, I can say from experience that the biggest problem with the US 101/OR 202 roundabout (mentioned towards the start of the thread) is that the 101S entrance/exit are too close together, meaning that unless you signal left people frequently don't react fast enough to stop:

...
At 20mph (29-30 ft/s) that means that 101S has a full second less to react vs. 101N, and only around 2 seconds to see a car going around and stop. The solution would be to move the 101S exit farther back in the roundabout, which would add that ≈1 second of reaction time (and also extend the solid line, there's functionally no reason for traffic in the circle to cross to the right lane). MS Paint mockup of what it could look like:

This is...interesting.

Generally, roundabout exits are meant to be slightly higher speed than entrances, but still have some deflection to ensure traffic doesn't exit so fast as to decrease the chance of yielding to crossing pedestrians.

Your design does have a much flatter exit (meaning, higher speed) than present, and does have the added benefit of distancing the exit and entrance enough that traffic coming from 101 would have greater warning of traffic continuing to circulate, and would be able to keep moving more often. But that may have a detrimental impact on traffic coming from 202, who now has to contend with traffic entering at a higher and more continuous rate.

I would also argue that most roundabouts, particularly single-lane roundabouts, don't have exceptional distance between the exit and entrance legs. I.e., this is a fairly normal issue for most roundabouts.
Pedestrian crosswalks don't belong within at least 100' from roundabout. Of course, an urge to use a cool design pushes safety to a back burner...

Speeds are too high 100 feet from a roundabout, better to use crosswalks at the entry/exit legs. Pedestrians will not detour that far anyways.
Title: Re: Crash prone 'modern roundabouts'
Post by: interstatefan990 on February 15, 2023, 12:45:16 AM
Isn't pedestrian traffic near roundabouts pretty low to start with? Since they're usually built in less densely populated areas or blend in with car-centric road design?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on February 15, 2023, 06:41:03 AM
Isn't pedestrian traffic near roundabouts pretty low to start with? Since they're usually built in less densely populated areas or blend in with car-centric road design?
You wish. US is a free country, so road designers are not bound by stupid rules, and roundabout in pedestrian core is a cool feature! (right at the top of crash intersection list.)

Actually after all the limitations are properly considered, roundabout use case ends up so rasor thin that they shouldn't be considered a mainstream approach.
Limitations an left turn capacity, on projected traffic growth, pedestrian presence, trucks percentage, speeds... No real scaling options....
There is a thread on fourth traffic light phase where cooperating autonomous vehicles can make use of cooperative yielding and small gaps. That is where roundabouts may shine... Although my feeling is juggling with wineglasses would be an easier and safer task.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 21, 2023, 08:39:46 AM
Relatively new I-95 interchange roundabout outside Richmond saw a serious crash that injured 6 people.  A passenger car crashed head-first into a tractor-trailer.

https://www.wric.com/news/local-news/richmond/six-people-injured-in-head-on-tractor-trailer-crash-at-maury-roundabout/
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 21, 2023, 08:52:44 AM
Relatively new I-95 interchange roundabout outside Richmond saw a serious crash that injured 6 people.  A passenger car crashed head-first into a tractor-trailer.

https://www.wric.com/news/local-news/richmond/six-people-injured-in-head-on-tractor-trailer-crash-at-maury-roundabout/
Doesn't sound like roundabout specific one. Entering oncoming traffic lane is bad regardless. If anything, roundabout slowed down oncoming truck for a better outcome.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on March 21, 2023, 10:34:56 AM
Relatively new I-95 interchange roundabout outside Richmond saw a serious crash that injured 6 people.  A passenger car crashed head-first into a tractor-trailer.

https://www.wric.com/news/local-news/richmond/six-people-injured-in-head-on-tractor-trailer-crash-at-maury-roundabout/
Doesn't sound like roundabout specific one. Entering oncoming traffic lane is bad regardless. If anything, roundabout slowed down oncoming truck for a better outcome.

Yeah. Based on the article the driver that cased the accident crossed the double yellow. The roundabout was immaterial to the issue.
Title: Re: Crash prone 'modern roundabouts'
Post by: SEWIGuy on March 21, 2023, 12:20:33 PM
So in other words, this really isn't an example of a "Crash prone 'modern roundabout.'"
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on March 21, 2023, 01:21:39 PM
So in other words, this really isn't an example of a "Crash prone 'modern roundabout.'"

Correct.  Rather, it's |tradephoric| attempting to pass off a single accident at a roundabout as proof that the roundabout is crash-prone.
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on March 21, 2023, 01:29:27 PM
So in other words, this really isn't an example of a "Crash prone 'modern roundabout.'"

Correct.  Rather, it's |tradephoric| attempting to pass off a single accident at a roundabout as proof that the roundabout is crash-prone.

Didn't even happen at a roundabout. It happened near one, and the vehicle that caused it hadn't approached it yet.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 21, 2023, 01:45:38 PM
Yeah. Based on the article the driver that cased the accident crossed the double yellow. The roundabout was immaterial to the issue.

The article made no mention of the driver crossing a double yellow.  This is how the article described the accident...

"According to police, the passenger vehicle was over-crowded with occupants and driving east on Maury Street. The passenger vehicle then crossed over into the westbound travel lane and hit a Semi-Tractor Trailer Tanker truck head-on. The tractor-trailer was exiting out of the roundabout onto Maury Street at the time."

An aerial view of the roundabout with the blue line indicating the driver's path traveling EB Maury Street prior to the roundabout being constructed.  If you "miss" the roundabout it now takes you straight into oncoming traffic.

(https://i.imgur.com/cjnRxtL.png)

 
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 21, 2023, 01:50:17 PM
So in other words, this really isn't an example of a "Crash prone 'modern roundabout.'"

Correct.  Rather, it's |tradephoric| attempting to pass off a single accident at a roundabout as proof that the roundabout is crash-prone.

Didn't even happen at a roundabout. It happened near one, and the vehicle that caused it hadn't approached it yet.
Being devil's advocate... We didn't see accident reconstruction, and it's not beyond reasonable doubt that truck exiting roundabout wasn't position correctly in the roadway as trucks do have hard time navigating small roundabouts. Article could state things from preliminary police report, which may be less than totally accurate
Title: Re: Crash prone 'modern roundabouts'
Post by: SEWIGuy on March 21, 2023, 01:52:15 PM
Yeah. Based on the article the driver that cased the accident crossed the double yellow. The roundabout was immaterial to the issue.

The article made no mention of the driver crossing a double yellow.  This is how the article described the accident...

"According to police, the passenger vehicle was over-crowded with occupants and driving east on Maury Street. The passenger vehicle then crossed over into the westbound travel lane and hit a Semi-Tractor Trailer Tanker truck head-on. The tractor-trailer was exiting out of the roundabout onto Maury Street at the time."

An aerial view of the roundabout with the blue line indicating the driver's path traveling EB Maury Street prior to the roundabout being constructed.  If you "miss" the roundabout it now takes you straight into oncoming traffic.

(https://i.imgur.com/cjnRxtL.png)

 


Uh...no it doesn't. You drew the line wrong.

Regardless, you can miss a light. Or a stop sign.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 21, 2023, 02:02:37 PM
Yeah. Based on the article the driver that cased the accident crossed the double yellow. The roundabout was immaterial to the issue.

The article made no mention of the driver crossing a double yellow.  This is how the article described the accident...

"According to police, the passenger vehicle was over-crowded with occupants and driving east on Maury Street. The passenger vehicle then crossed over into the westbound travel lane and hit a Semi-Tractor Trailer Tanker truck head-on. The tractor-trailer was exiting out of the roundabout onto Maury Street at the time."

An aerial view of the roundabout with the blue line indicating the driver's path traveling EB Maury Street prior to the roundabout being constructed.  If you "miss" the roundabout it now takes you straight into oncoming traffic. 


Uh...no it doesn't. You drew the line wrong.

Regardless, you can miss a light. Or a stop sign.
Overall, events like that do not work as an argument against roundabout. They are not roundabout-specific and may happen in other settings.
But do go into statistics which may show roundabouts  are more (or less) prone to accidents overall compared to other settings.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on March 21, 2023, 02:33:35 PM
The article made no mention of the driver crossing a double yellow.

"... According to police, the passenger vehicle was ... driving east ... then crossed over into the westbound travel lane ..."

Are you telling me there's no double yellow between eastbound and westbound lanes?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 21, 2023, 03:13:09 PM
Are you telling me there's no double yellow between eastbound and westbound lanes?

Really all I'm saying is the article never mentioned that the vehicle crossed over the double-yellow.  My gut is telling me the impact took place somewhere in the very lower left of the picture after the passenger vehicle crossed over the splitter island.

(https://www.virginiadot.org/Projects/Richmond/asset_upload_file335_137242.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: SEWIGuy on March 21, 2023, 03:39:42 PM
Yeah. Based on the article the driver that cased the accident crossed the double yellow. The roundabout was immaterial to the issue.

The article made no mention of the driver crossing a double yellow.  This is how the article described the accident...

"According to police, the passenger vehicle was over-crowded with occupants and driving east on Maury Street. The passenger vehicle then crossed over into the westbound travel lane and hit a Semi-Tractor Trailer Tanker truck head-on. The tractor-trailer was exiting out of the roundabout onto Maury Street at the time."

An aerial view of the roundabout with the blue line indicating the driver's path traveling EB Maury Street prior to the roundabout being constructed.  If you "miss" the roundabout it now takes you straight into oncoming traffic. 


Uh...no it doesn't. You drew the line wrong.

Regardless, you can miss a light. Or a stop sign.
Overall, events like that do not work as an argument against roundabout. They are not roundabout-specific and may happen in other settings.
But do go into statistics which may show roundabouts  are more (or less) prone to accidents overall compared to other settings.


Oh I agree. My understanding is that roundabouts have no impact on the frequency of accidents, but do have a significantly impact on the severity of accidents.

Now does that mean a roundabout will be safer in EVERY situation?  Of course not.  But by and large, they are safer.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 21, 2023, 03:48:19 PM
Yeah. Based on the article the driver that cased the accident crossed the double yellow. The roundabout was immaterial to the issue.

The article made no mention of the driver crossing a double yellow.  This is how the article described the accident...

"According to police, the passenger vehicle was over-crowded with occupants and driving east on Maury Street. The passenger vehicle then crossed over into the westbound travel lane and hit a Semi-Tractor Trailer Tanker truck head-on. The tractor-trailer was exiting out of the roundabout onto Maury Street at the time."

An aerial view of the roundabout with the blue line indicating the driver's path traveling EB Maury Street prior to the roundabout being constructed.  If you "miss" the roundabout it now takes you straight into oncoming traffic. 


Uh...no it doesn't. You drew the line wrong.

Regardless, you can miss a light. Or a stop sign.
Overall, events like that do not work as an argument against roundabout. They are not roundabout-specific and may happen in other settings.
But do go into statistics which may show roundabouts  are more (or less) prone to accidents overall compared to other settings.


Oh I agree. My understanding is that roundabouts have no impact on the frequency of accidents, but do have a significantly impact on the severity of accidents.

Now does that mean a roundabout will be safer in EVERY situation?  Of course not.  But by and large, they are safer.
Well, you basically have to confirm almost every word in your statement if we want to restart this discussion. My impression is that each parameter (accident frequency, accident severity, overall loss) can go up or down, depending on design quality and suitability of roundabout in a particular location. 
Title: Re: Crash prone 'modern roundabouts'
Post by: SEWIGuy on March 21, 2023, 03:56:09 PM
I do not wish to re-start this discussion.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 29, 2023, 11:46:41 AM
After US 41 roundabout crashes, Sarasota works to educate visitors, new residents
https://www.wfla.com/news/sarasota-county/after-u-s-41-roundabout-crashes-sarasota-works-to-educate-visitors-new-residents/

Always wondered how these roundabouts along US 41 in Sarasota would do.  The triple-lane Gulfstream roundabout is the most complicated of the bunch.
(https://media.yourobserver.com/img/photos/2022/12/22/DroneRoundy2_t850.jpeg?94beabde1e982a4eee8f83697e93b1d92468de7c)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 29, 2023, 12:01:10 PM
After US 41 roundabout crashes, Sarasota works to educate visitors, new residents
https://www.wfla.com/news/sarasota-county/after-u-s-41-roundabout-crashes-sarasota-works-to-educate-visitors-new-residents/

Always wondered how these roundabouts along US 41 in Sarasota would do.  The triple-lane Gulfstream roundabout is the most complicated of the bunch.
(https://media.yourobserver.com/img/photos/2022/12/22/DroneRoundy2_t850.jpeg?94beabde1e982a4eee8f83697e93b1d92468de7c)
Well, you cannot blame engineers because this should not be called engineering.
I wonder if there is a PE stamp on the project, and how that person feels about stats like these
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on March 29, 2023, 12:32:54 PM
I had started mapping out all the conflict points, and then I just got thoroughly confused up at the top part.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 29, 2023, 12:45:23 PM
I had started mapping out all the conflict points, and then I just got thoroughly confused up at the top part.
Top lane is effectively a slip lane from Gulfstram to US41 SB, if that helps
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on March 29, 2023, 12:50:17 PM
It was the top-right part that confused me.  I thought it was two lanes, judging by the striping immediately past it.  But then I noticed that the approach from the right is only one lane, and that the outer lane of the top-right part is actually striped off as neutral space.  Weird for a one-lane section to feed into a three-lane section.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 29, 2023, 01:42:15 PM
It was the top-right part that confused me.  I thought it was two lanes, judging by the striping immediately past it.  But then I noticed that the approach from the right is only one lane, and that the outer lane of the top-right part is actually striped off as neutral space.  Weird for a one-lane section to feed into a three-lane section.
bottom  one lane is effectively a one way driveway for what looks like apartment/mixed use complex
Right one lane is a slip lane at right edge + whatever feeds into circular movement. Circulationg approach looks like 1 lane + 1 lane taken by construction. Before roundabout, that was 1 slip + 2 traffic light lanes.
 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on March 29, 2023, 08:02:29 PM
I can't think of too many (any?) signalized intersections with triple left turns that were replaced by roundabouts.

I find the article to be a little ridiculous. The locals can navigate the roundabouts just fine but it's all those pesky "tourists" that cause the crashes? Talk about sticking your head in the sand.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 30, 2023, 06:50:33 AM
I can't think of too many (any?) signalized intersections with triple left turns that were replaced by roundabouts.

I find the article to be a little ridiculous. The locals can navigate the roundabouts just fine but it's all those pesky "tourists" that cause the crashes? Talk about sticking your head in the sand.
If you do something on a regular basis - be it driving through a complicated intersection, cooking fancy dish, working on a complex car or what not - you eventually get used to it and get better at that task. Those 3 left turning lanes are the main for people coming from several small keys. Looking at house density on those keys, I wonder if sardines in a can are really packed that tight and there should be twice as many of them in that can.  I bet regulars take that road pretty often.
So yes, most likely residents use those left turning lanes at high speed, and any tourist trying to navigate the crazy layout at a mere 30 MPH hinders traffic flow.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 31, 2023, 02:47:18 PM
Sofian Kiyine, a 25 year old midfielder for OH Leuven, blasted through a roundabout in Liege, Belgium on Thursday smashing through the wall of a sports hall at high speed landing on the gymnasium floor where it was reported children were playing just moments before the crash.  The video is absolutely wild. 

Video from the Telegraph youtube page
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on March 31, 2023, 02:49:22 PM
Sofian Kiyine, a 25 year old midfielder for OH Leuven, blasted through a roundabout in Liege, Belgium on Thursday smashing through the wall of a sports hall at high speed landing on the gymnasium floor where it was reported children were playing just moments before the crash.  The video is absolutely wild.

Is this a crash prone modern roundabout?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 31, 2023, 02:57:05 PM
It's more of a launch pad than a modern roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on March 31, 2023, 03:02:42 PM
It's more of a launch pad than a modern roundabout.

Wow!  How many crashes have there been?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on March 31, 2023, 05:54:57 PM
This is the aerial of the roundabout the guy hit.  He was driving along Quai Jules Destree N617 which is a limited access roadway with a 90 kph speed limit.

https://www.google.com/maps/@50.6034457,5.4862863,96m/data=!3m1!1e3
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on March 31, 2023, 06:20:11 PM
This is the aerial of the roundabout the guy hit.  He was driving along Quai Jules Destree N617 which is a limited access roadway with a 90 kph speed limit.

https://www.google.com/maps/@50.6034457,5.4862863,96m/data=!3m1!1e3

Does not answer the question that was asked.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on March 31, 2023, 06:28:49 PM
It's more of a launch pad than a modern roundabout.

Wow!  How many crashes have there been?
Sofian Kiyine, a 25 year old midfielder for OH Leuven, blasted through a roundabout in Liege, Belgium on Thursday smashing through the wall of a sports hall at high speed landing on the gymnasium floor where it was reported children were playing just moments before the crash.  The video is absolutely wild.

Is this a crash prone modern roundabout?
A better question:
How many crashes this guy has on his record?
Title: Re: Crash prone 'modern roundabouts'
Post by: algorerhythms on March 31, 2023, 09:16:59 PM
That seems like a case where the driver is the problem…
Title: Re: Crash prone 'modern roundabouts'
Post by: thspfc on April 01, 2023, 10:35:12 PM
That seems like a case where the driver is the problem…
That's basically this entire thread.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 02, 2023, 08:14:53 AM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Title: Re: Crash prone 'modern roundabouts'
Post by: thspfc on April 02, 2023, 04:17:40 PM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 02, 2023, 05:54:30 PM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?
Title: Re: Crash prone 'modern roundabouts'
Post by: SEWIGuy on April 02, 2023, 06:01:54 PM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?

I’ve seen some absurd analogies before, but this…this… is a piece of art.
Title: Re: Crash prone 'modern roundabouts'
Post by: thspfc on April 02, 2023, 09:56:22 PM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?
What are some legitimate differences you notice between the roundabouts in this thread and roundabouts that are not crash-prone?
Title: Re: Crash prone 'modern roundabouts'
Post by: Scott5114 on April 03, 2023, 05:10:33 AM
It's more of a launch pad than a modern roundabout.

You should probably post it in "Crash prone 'launch pads'" then.

That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?
What are some legitimate differences you notice between the roundabouts in this thread and roundabouts that are not crash-prone?

None of the roundabouts in this thread are crash-prone. In fact, I haven't seen any roundabouts crashing in this thread at all. Maybe it should be renamed to "Crash prone modern cars", because none of the roundabouts have crashed.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 03, 2023, 09:52:12 AM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?
What are some legitimate differences you notice between the roundabouts in this thread and roundabouts that are not crash-prone?

Triple-lane or complex double-lane roundabouts are the types where you can see 4X increases in crashes.  The roundabouts with triple-digit annual crashes documented in this thread are exclusively these multi-lane variety.   
Title: Re: Crash prone 'modern roundabouts'
Post by: thspfc on April 03, 2023, 10:58:21 AM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?
What are some legitimate differences you notice between the roundabouts in this thread and roundabouts that are not crash-prone?

Triple-lane or complex double-lane roundabouts are the types where you can see 4X increases in crashes.  The roundabouts with triple-digit annual crashes documented in this thread are exclusively these multi-lane variety.   
Are the majority of roundabouts not at least double-lane? All of them around here are double-lane. They’re not crash-prone. Triple-lane is a different discussion - once you get to the point of needing a triple-lane roundabout, alternative options should be considered - but double lane roundabouts are extremely common and the majority of them have no issues with crashes.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 03, 2023, 11:00:01 AM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?
What are some legitimate differences you notice between the roundabouts in this thread and roundabouts that are not crash-prone?

Some of the things which often considered for design are traffic counts, %% of traffic to secondary road compared to throughfare, %% of left turns, %% of trucks, all that preferrably in 15 min increments as morning rush hour and evening rush hour may have different patterns.
Design for the loop itself determines number of lanes, radius of inscribed circle, approach positioning and curvature, pavement grade, apron width and grade.  These are just a few parameters from the top of my head.
Overall, I am not the one with most respect to traffic engineers on this forum - but even I am totally flabbergasted that someone thinks that traffic engineer's job is nothing beyond Ctrl-C Ctrl-V...   
Title: Re: Crash prone 'modern roundabouts'
Post by: SEWIGuy on April 03, 2023, 11:19:55 AM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?
What are some legitimate differences you notice between the roundabouts in this thread and roundabouts that are not crash-prone?

Triple-lane or complex double-lane roundabouts are the types where you can see 4X increases in crashes.  The roundabouts with triple-digit annual crashes documented in this thread are exclusively these multi-lane variety.   
Are the majority of roundabouts not at least double-lane? All of them around here are double-lane. They’re not crash-prone. Triple-lane is a different discussion - once you get to the point of needing a triple-lane roundabout, alternative options should be considered - but double lane roundabouts are extremely common and the majority of them have no issues with crashes.


I live in Green Bay and drive through double lane roundabouts regularly. They aren't a problem at all. There are a couple triple lane ones around here, and they are the ones even I struggle with.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 03, 2023, 11:36:15 AM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?
What are some legitimate differences you notice between the roundabouts in this thread and roundabouts that are not crash-prone?

Triple-lane or complex double-lane roundabouts are the types where you can see 4X increases in crashes.  The roundabouts with triple-digit annual crashes documented in this thread are exclusively these multi-lane variety.   
Are the majority of roundabouts not at least double-lane? All of them around here are double-lane. They’re not crash-prone. Triple-lane is a different discussion - once you get to the point of needing a triple-lane roundabout, alternative options should be considered - but double lane roundabouts are extremely common and the majority of them have no issues with crashes.


I live in Green Bay and drive through double lane roundabouts regularly. They aren't a problem at all. There are a couple triple lane ones around here, and they are the ones even I struggle with.
Again, what do you define as "problem"? Crash rates are measured in crashes per million entering vehicles. Well-designed intersection should have months, if not years,  between  crashes. So your anecdotal experience of gong through specific roundabout few thousand times isn't a good basis for the judgement.
Now if you have some access to DOT data showing crash locations...   
Title: Re: Crash prone 'modern roundabouts'
Post by: SEWIGuy on April 03, 2023, 11:38:26 AM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?
What are some legitimate differences you notice between the roundabouts in this thread and roundabouts that are not crash-prone?

Triple-lane or complex double-lane roundabouts are the types where you can see 4X increases in crashes.  The roundabouts with triple-digit annual crashes documented in this thread are exclusively these multi-lane variety.   
Are the majority of roundabouts not at least double-lane? All of them around here are double-lane. They’re not crash-prone. Triple-lane is a different discussion - once you get to the point of needing a triple-lane roundabout, alternative options should be considered - but double lane roundabouts are extremely common and the majority of them have no issues with crashes.


I live in Green Bay and drive through double lane roundabouts regularly. They aren't a problem at all. There are a couple triple lane ones around here, and they are the ones even I struggle with.
Again, what do you define as "problem"? Crash rates are measured in crashes per million entering vehicles. Well-designed intersection should have months, if not years,  between  crashes. So your anecdotal experience of gong through specific roundabout few thousand times isn't a good basis for the judgement.
Now if you have some access to DOT data showing crash locations...   


I wasn't stating any sort of claim regarding the number of accidents at roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 03, 2023, 11:49:46 AM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?
What are some legitimate differences you notice between the roundabouts in this thread and roundabouts that are not crash-prone?

Triple-lane or complex double-lane roundabouts are the types where you can see 4X increases in crashes.  The roundabouts with triple-digit annual crashes documented in this thread are exclusively these multi-lane variety.   
Are the majority of roundabouts not at least double-lane? All of them around here are double-lane. They’re not crash-prone. Triple-lane is a different discussion - once you get to the point of needing a triple-lane roundabout, alternative options should be considered - but double lane roundabouts are extremely common and the majority of them have no issues with crashes.


I live in Green Bay and drive through double lane roundabouts regularly. They aren't a problem at all. There are a couple triple lane ones around here, and they are the ones even I struggle with.
Again, what do you define as "problem"? Crash rates are measured in crashes per million entering vehicles. Well-designed intersection should have months, if not years,  between  crashes. So your anecdotal experience of gong through specific roundabout few thousand times isn't a good basis for the judgement.
Now if you have some access to DOT data showing crash locations...   


I wasn't stating any sort of claim regarding the number of accidents at roundabouts.
You did. Highlighted above for your convenience.
Title: Re: Crash prone 'modern roundabouts'
Post by: SEWIGuy on April 03, 2023, 11:55:12 AM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?
What are some legitimate differences you notice between the roundabouts in this thread and roundabouts that are not crash-prone?

Triple-lane or complex double-lane roundabouts are the types where you can see 4X increases in crashes.  The roundabouts with triple-digit annual crashes documented in this thread are exclusively these multi-lane variety.   
Are the majority of roundabouts not at least double-lane? All of them around here are double-lane. They’re not crash-prone. Triple-lane is a different discussion - once you get to the point of needing a triple-lane roundabout, alternative options should be considered - but double lane roundabouts are extremely common and the majority of them have no issues with crashes.


I live in Green Bay and drive through double lane roundabouts regularly. They aren't a problem at all. There are a couple triple lane ones around here, and they are the ones even I struggle with.
Again, what do you define as "problem"? Crash rates are measured in crashes per million entering vehicles. Well-designed intersection should have months, if not years,  between  crashes. So your anecdotal experience of gong through specific roundabout few thousand times isn't a good basis for the judgement.
Now if you have some access to DOT data showing crash locations...   


I wasn't stating any sort of claim regarding the number of accidents at roundabouts.
You did. Highlighted above for your convenience.


Nope. You ignored the context. I claimed they aren't a problem for me to drive through. Never claimed anything about how crash prone they are.
Title: Re: Crash prone 'modern roundabouts'
Post by: ET21 on April 03, 2023, 12:54:51 PM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?

I’ve seen some absurd analogies before, but this…this… is a piece of art.

Should be framed and hung in the Louvre
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 03, 2023, 12:59:30 PM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?
What are some legitimate differences you notice between the roundabouts in this thread and roundabouts that are not crash-prone?

Triple-lane or complex double-lane roundabouts are the types where you can see 4X increases in crashes.  The roundabouts with triple-digit annual crashes documented in this thread are exclusively these multi-lane variety.   
Are the majority of roundabouts not at least double-lane? All of them around here are double-lane. They’re not crash-prone. Triple-lane is a different discussion - once you get to the point of needing a triple-lane roundabout, alternative options should be considered - but double lane roundabouts are extremely common and the majority of them have no issues with crashes.


I live in Green Bay and drive through double lane roundabouts regularly. They aren't a problem at all. There are a couple triple lane ones around here, and they are the ones even I struggle with.
Again, what do you define as "problem"? Crash rates are measured in crashes per million entering vehicles. Well-designed intersection should have months, if not years,  between  crashes. So your anecdotal experience of gong through specific roundabout few thousand times isn't a good basis for the judgement.
Now if you have some access to DOT data showing crash locations...   


I wasn't stating any sort of claim regarding the number of accidents at roundabouts.
You did. Highlighted above for your convenience.


Nope. You ignored the context. I claimed they aren't a problem for me to drive through. Never claimed anything about how crash prone they are.
Oh, you know, you think  you're totally healthy until your primary care says "you may want to talk to oncologist about it",  you're doing great at your job until HR wants to see you at 9.00 sharp, you're a great driver until the day your car is totaled... 
That's the way things work, and good engineer or doctor always has to look at those one-off events because everyone gets a one-off eventually. The difference between professional statistics and anecdotal evidence can be stark. . 
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on April 03, 2023, 01:20:08 PM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?

I’ve seen some absurd analogies before, but this…this… is a piece of art.

Should be framed and hung in the Louvre

Viewed through a loupe.
Title: Re: Crash prone 'modern roundabouts'
Post by: SEWIGuy on April 03, 2023, 02:28:34 PM
That seems like a case where the driver is the problem…
That's basically this entire thread.
That's shitty engineer idea of any crash. "99.99% drivers had no problems there!"
Almost none of the roundabouts in this thread are crash-prone due to poor design. They’re just standard roundabouts that, for whatever reason, are the sites of frequent crashes. If these roundabouts are truly crash-prone due to poor design, then why are there thousands of US roundabouts that are the exact same, but not crash-prone?
Try telling that to your doctor - there are thousands healthy people which look exact same - 2 hand, 2 legs, 1 head... So why do you think I need that treatment?
What are some legitimate differences you notice between the roundabouts in this thread and roundabouts that are not crash-prone?

Triple-lane or complex double-lane roundabouts are the types where you can see 4X increases in crashes.  The roundabouts with triple-digit annual crashes documented in this thread are exclusively these multi-lane variety.   
Are the majority of roundabouts not at least double-lane? All of them around here are double-lane. They’re not crash-prone. Triple-lane is a different discussion - once you get to the point of needing a triple-lane roundabout, alternative options should be considered - but double lane roundabouts are extremely common and the majority of them have no issues with crashes.


I live in Green Bay and drive through double lane roundabouts regularly. They aren't a problem at all. There are a couple triple lane ones around here, and they are the ones even I struggle with.
Again, what do you define as "problem"? Crash rates are measured in crashes per million entering vehicles. Well-designed intersection should have months, if not years,  between  crashes. So your anecdotal experience of gong through specific roundabout few thousand times isn't a good basis for the judgement.
Now if you have some access to DOT data showing crash locations...   


I wasn't stating any sort of claim regarding the number of accidents at roundabouts.
You did. Highlighted above for your convenience.


Nope. You ignored the context. I claimed they aren't a problem for me to drive through. Never claimed anything about how crash prone they are.
Oh, you know, you think  you're totally healthy until your primary care says "you may want to talk to oncologist about it",  you're doing great at your job until HR wants to see you at 9.00 sharp, you're a great driver until the day your car is totaled... 
That's the way things work, and good engineer or doctor always has to look at those one-off events because everyone gets a one-off eventually. The difference between professional statistics and anecdotal evidence can be stark. . 

Right. Which is why I never claimed my statements were based on "professional statistics."
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on April 03, 2023, 06:52:47 PM
I like the idea of amateur statistics and semi-pro statistics.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 04, 2023, 03:15:30 PM
I'll take any stats at this point.  For the amount of double and triple lane roundabouts in Green Bay it's difficult to track down up to date crash data for them. 
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on April 04, 2023, 04:02:47 PM
Are the majority of roundabouts not at least double-lane? All of them around here are double-lane. They’re not crash-prone. Triple-lane is a different discussion - once you get to the point of needing a triple-lane roundabout, alternative options should be considered - but double lane roundabouts are extremely common and the majority of them have no issues with crashes.

The majority of modern roundabouts in America are not double-lane.  I have a database of over 10,000 roundabouts and roughly 75% of them are single-lane roundabouts.  Not all double-lane roundabouts are prone to crashes either, it's mainly the 2X2 roundabouts that see these high crash rates.  Case in point a 2x2 roundabout in Deland Florida has been the site of 94 crashes and it's been open less than a year. 

Resident asks: Is a roundabout causing crashes in DeLand?
https://www.mynews13.com/fl/orlando/news/2023/03/06/traffic-inbox-roundabout-causing-crashes-in-deland#:~:text=Volusia%20County%20opened%20a%20roundabout,spot%20since%20the%20roundabout%20opened
(https://i0.wp.com/beacononlinenews.com/wp-content/uploads/2021/07/998acce74d34f228394f551ffe1410cb-1.jpg?fit=1200%2C777&ssl=1)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 04, 2023, 04:21:37 PM

Are the majority of roundabouts not at least double-lane? All of them around here are double-lane. They’re not crash-prone. Triple-lane is a different discussion - once you get to the point of needing a triple-lane roundabout, alternative options should be considered - but double lane roundabouts are extremely common and the majority of them have no issues with crashes.

The majority of modern roundabouts in America are not double-lane.  I have a database of over 10,000 roundabouts and roughly 75% of them are single-lane roundabouts.  Not all double-lane roundabouts are prone to crashes either, it's mainly the 2X2 roundabouts that see these high crash rates.

It's been a few years, but I remember trying to come up with multi-lane counterexamples, and it actually ended up being difficult for me to list examples where there were two lanes circulating around the entire circle.  A lot of what we think of as two-lane roundabouts are actually one/two hybrids.

I'm curious to know if you categorize those as single-lane, multi-lane, or something else.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 04, 2023, 04:56:10 PM

Are the majority of roundabouts not at least double-lane? All of them around here are double-lane. They’re not crash-prone. Triple-lane is a different discussion - once you get to the point of needing a triple-lane roundabout, alternative options should be considered - but double lane roundabouts are extremely common and the majority of them have no issues with crashes.

The majority of modern roundabouts in America are not double-lane.  I have a database of over 10,000 roundabouts and roughly 75% of them are single-lane roundabouts.  Not all double-lane roundabouts are prone to crashes either, it's mainly the 2X2 roundabouts that see these high crash rates.

It's been a few years, but I remember trying to come up with multi-lane counterexamples, and it actually ended up being difficult for me to list examples where there were two lanes circulating around the entire circle.  A lot of what we think of as two-lane roundabouts are actually one/two hybrids.

I'm curious to know if you categorize those as single-lane, multi-lane, or something else.
Not very specific to 2x1 intersection, but a "turbo roundabout" name is being used.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 04, 2023, 05:19:04 PM
I thought "turbo" was specific to the ones that funnel you out of the roundabout before reaching the 270° point.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 05, 2023, 11:08:41 AM
I thought "turbo" was specific to the ones that funnel you out of the roundabout before reaching the 270° point.
Yes, basically a circle made of pieces of lanes wound around the center, with every piece <360 degrees. (that is not more than 270 in case of perpendicular intersection of 2 roads)
apparently all-single-lane circle cannot be made that way.   
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 06, 2023, 03:03:23 PM

I thought "turbo" was specific to the ones that funnel you out of the roundabout before reaching the 270° point.

Yes, basically a circle made of pieces of lanes wound around the center, with every piece <360 degrees. (that is not more than 270 in case of perpendicular intersection of 2 roads)
apparently all-single-lane circle cannot be made that way.   

That still leaves roundabouts that are neither 100% single-lane, 100% multi-lane, nor turbo.  Like this, for example. (https://goo.gl/maps/aNHsWZLKjbU4uKhQ7)
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 06, 2023, 03:24:42 PM

I thought "turbo" was specific to the ones that funnel you out of the roundabout before reaching the 270° point.

Yes, basically a circle made of pieces of lanes wound around the center, with every piece <360 degrees. (that is not more than 270 in case of perpendicular intersection of 2 roads)
apparently all-single-lane circle cannot be made that way.   

That still leaves roundabouts that are neither 100% single-lane, 100% multi-lane, nor turbo.  Like this, for example. (https://goo.gl/maps/aNHsWZLKjbU4uKhQ7)
As far as I understand, this is a "traffic circle" rather than a "modern roundabout"
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 06, 2023, 03:30:23 PM
As far as I understand, this is a "traffic circle" rather than a "modern roundabout"

What criteria are not met?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 06, 2023, 03:43:23 PM
As far as I understand, this is a "traffic circle" rather than a "modern roundabout"

What criteria are not met?
Lane arrangement. For example, there is a conflict in exit to Branson Landing at 4 o'clock and exit to Parnell drive at 1 o'clock  - an outer lane heading to Parnell must yield to inner lane exiting to BL.
Just try plotting possible trajectories from Skaggs to those two exits
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 06, 2023, 06:43:27 PM
As far as I understand, this is a "traffic circle" rather than a "modern roundabout"

What criteria are not met?
Lane arrangement. For example, there is a conflict in exit to Branson Landing at 4 o'clock and exit to Parnell drive at 1 o'clock  - an outer lane heading to Parnell must yield to inner lane exiting to BL.
Just try plotting possible trajectories from Skaggs to those two exits

I don't think that is an unusual circumstance for roundabouts where an entry and exit meet, both with two lanes like here. Traffic intending to continue around the circle can either turn into the inside or outside lane; there is a small yellow painted chevron area (https://goo.gl/maps/BjuCY539WXQH7act6) to encourage traffic to "spiral" into the outer lane, discouraging traffic for Parnell from entering the inner lane and then suddenly dashing across the outside lane to exit.

I would personally consider that a "modern roundabout" without any shadow of a doubt. The fifth leg complicates it a bit, but only slightly. The markings, overall size, deflection, and signage are all consistent with modern roundabout standards. MTJ, the company that designed it, also calls it a roundabout (https://www.mtjengineering.com/project/us-65-branson-landing-blvd-roundabout-branson-mo/).
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 06, 2023, 07:49:47 PM
As far as I understand, this is a "traffic circle" rather than a "modern roundabout"

What criteria are not met?
Lane arrangement. For example, there is a conflict in exit to Branson Landing at 4 o'clock and exit to Parnell drive at 1 o'clock  - an outer lane heading to Parnell must yield to inner lane exiting to BL.
Just try plotting possible trajectories from Skaggs to those two exits

I don't think that is an unusual circumstance for roundabouts where an entry and exit meet, both with two lanes like here. Traffic intending to continue around the circle can either turn into the inside or outside lane; there is a small yellow painted chevron area (https://goo.gl/maps/BjuCY539WXQH7act6) to encourage traffic to "spiral" into the outer lane, discouraging traffic for Parnell from entering the inner lane and then suddenly dashing across the outside lane to exit.

I would personally consider that a "modern roundabout" without any shadow of a doubt. The fifth leg complicates it a bit, but only slightly. The markings, overall size, deflection, and signage are all consistent with modern roundabout standards. MTJ, the company that designed it, also calls it a roundabout (https://www.mtjengineering.com/project/us-65-branson-landing-blvd-roundabout-branson-mo/).
OK, looked at the signage a bit closer.  Let me put it so - if I ever had to order roundabout design, now I know who should not be asked for a bid.
Signage is too poor to discuss. I agree that with some better minimal stripping and signage it could become a roundabout - but for now it is an exhibit 1 of "why some roundabouts are so bad"
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 06, 2023, 08:28:12 PM
As far as I understand, this is a "traffic circle" rather than a "modern roundabout"

What criteria are not met?
Lane arrangement. For example, there is a conflict in exit to Branson Landing at 4 o'clock and exit to Parnell drive at 1 o'clock  - an outer lane heading to Parnell must yield to inner lane exiting to BL.
Just try plotting possible trajectories from Skaggs to those two exits

I don't think that is an unusual circumstance for roundabouts where an entry and exit meet, both with two lanes like here. Traffic intending to continue around the circle can either turn into the inside or outside lane; there is a small yellow painted chevron area (https://goo.gl/maps/BjuCY539WXQH7act6) to encourage traffic to "spiral" into the outer lane, discouraging traffic for Parnell from entering the inner lane and then suddenly dashing across the outside lane to exit.

I would personally consider that a "modern roundabout" without any shadow of a doubt. The fifth leg complicates it a bit, but only slightly. The markings, overall size, deflection, and signage are all consistent with modern roundabout standards. MTJ, the company that designed it, also calls it a roundabout (https://www.mtjengineering.com/project/us-65-branson-landing-blvd-roundabout-branson-mo/).
OK, looked at the signage a bit closer.  Let me put it so - if I ever had to order roundabout design, now I know who should not be asked for a bid.
Signage is too poor to discuss. I agree that with some better minimal stripping and signage it could become a roundabout - but for now it is an exhibit 1 of "why some roundabouts are so bad"

Did a little more digging. The roundabout was built in 2005, and opened in 2005 or early 2006. It opened with striping nearly identical to what we see today. This is the striping  (https://goo.gl/maps/RC2YXNuoox2QhYKfA)at the entry from Veterans Blvd when it first opened; the arrows are messed up but the striping is solid.

Looking back at historic street view, they seem to have messed up the striping around 2013 (https://goo.gl/maps/KHPcJv8HMf2P7njw9), making it seem like the outside lane could continue circulating around the circle at the Veterans Blvd entry, though the arrows still correctly showed both lanes in the roundabout as being able to exit onto Branson Landing, and the inside lane being able to continue around. This striping error was rectified around late 2014 or early 2015 when the inside lane was repaved.

There are now double white lines (https://goo.gl/maps/3p8TTmu9WRfdhif2A) at that point, to [try and] ensure traffic does not circulate around towards Parnell from the outside lane. While double white lines are unusual at roundabouts, at least at points where traffic absolutely must cross them (as traffic entering from Veterans Blvd must to enter the roundabout), vehicles will eventually create a natural gap through tire track degradation.

This all said, the roundabout seems just fine, and I don't see any issues with anything MTJ did. Could you be a little more specific as to the exact problem with the current roundabout? To go back to your original point, I don't see any place where an outer lane yields to an inner lane.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 06, 2023, 08:44:32 PM
As far as I understand, this is a "traffic circle" rather than a "modern roundabout"

What criteria are not met?
Lane arrangement. For example, there is a conflict in exit to Branson Landing at 4 o'clock and exit to Parnell drive at 1 o'clock  - an outer lane heading to Parnell must yield to inner lane exiting to BL.
Just try plotting possible trajectories from Skaggs to those two exits

I don't think that is an unusual circumstance for roundabouts where an entry and exit meet, both with two lanes like here. Traffic intending to continue around the circle can either turn into the inside or outside lane; there is a small yellow painted chevron area (https://goo.gl/maps/BjuCY539WXQH7act6) to encourage traffic to "spiral" into the outer lane, discouraging traffic for Parnell from entering the inner lane and then suddenly dashing across the outside lane to exit.

I would personally consider that a "modern roundabout" without any shadow of a doubt. The fifth leg complicates it a bit, but only slightly. The markings, overall size, deflection, and signage are all consistent with modern roundabout standards. MTJ, the company that designed it, also calls it a roundabout (https://www.mtjengineering.com/project/us-65-branson-landing-blvd-roundabout-branson-mo/).
OK, looked at the signage a bit closer.  Let me put it so - if I ever had to order roundabout design, now I know who should not be asked for a bid.
Signage is too poor to discuss. I agree that with some better minimal stripping and signage it could become a roundabout - but for now it is an exhibit 1 of "why some roundabouts are so bad"

Did a little more digging. The roundabout was built in 2005, and opened in 2005 or early 2006. It opened with striping nearly identical to what we see today. This is the striping  (https://goo.gl/maps/RC2YXNuoox2QhYKfA)at the entry from Veterans Blvd when it first opened; the arrows are messed up but the striping is solid.

Looking back at historic street view, they seem to have messed up the striping around 2013 (https://goo.gl/maps/KHPcJv8HMf2P7njw9), making it seem like the outside lane could continue circulating around the circle at the Veterans Blvd entry, though the arrows still correctly showed both lanes in the roundabout as being able to exit onto Branson Landing, and the inside lane being able to continue around. This striping error was rectified around late 2014 or early 2015 when the inside lane was repaved.

There are now double white lines (https://goo.gl/maps/3p8TTmu9WRfdhif2A) at that point, to [try and] ensure traffic does not circulate around towards Parnell from the outside lane. While double white lines are unusual at roundabouts, at least at points where traffic absolutely must cross them (as traffic entering from Veterans Blvd must to enter the roundabout), vehicles will eventually create a natural gap through tire track degradation.

This all said, the roundabout seems just fine, and I don't see any issues with anything MTJ did. Could you be a little more specific as to the exact problem with the current roundabout? To go back to your original point, I don't see any place where an outer lane yields to an inner lane.

According to this sign, there is at least one point. Hard to tell where it is, though.
https://www.google.com/maps/@36.6496759,-93.2207263,3a,75y,112.83h,78.79t/data=!3m6!1e1!3m4!1sB9cloEhzT16MrLnUeY7Yvw!2e0!7i16384!8i8192
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on April 07, 2023, 12:19:44 AM
As far as I understand, this is a "traffic circle" rather than a "modern roundabout"

What criteria are not met?
Lane arrangement. For example, there is a conflict in exit to Branson Landing at 4 o'clock and exit to Parnell drive at 1 o'clock  - an outer lane heading to Parnell must yield to inner lane exiting to BL.
Just try plotting possible trajectories from Skaggs to those two exits

I don't think that is an unusual circumstance for roundabouts where an entry and exit meet, both with two lanes like here. Traffic intending to continue around the circle can either turn into the inside or outside lane; there is a small yellow painted chevron area (https://goo.gl/maps/BjuCY539WXQH7act6) to encourage traffic to "spiral" into the outer lane, discouraging traffic for Parnell from entering the inner lane and then suddenly dashing across the outside lane to exit.

I would personally consider that a "modern roundabout" without any shadow of a doubt. The fifth leg complicates it a bit, but only slightly. The markings, overall size, deflection, and signage are all consistent with modern roundabout standards. MTJ, the company that designed it, also calls it a roundabout (https://www.mtjengineering.com/project/us-65-branson-landing-blvd-roundabout-branson-mo/).
OK, looked at the signage a bit closer.  Let me put it so - if I ever had to order roundabout design, now I know who should not be asked for a bid.
Signage is too poor to discuss. I agree that with some better minimal stripping and signage it could become a roundabout - but for now it is an exhibit 1 of "why some roundabouts are so bad"

Did a little more digging. The roundabout was built in 2005, and opened in 2005 or early 2006. It opened with striping nearly identical to what we see today. This is the striping  (https://goo.gl/maps/RC2YXNuoox2QhYKfA)at the entry from Veterans Blvd when it first opened; the arrows are messed up but the striping is solid.

Looking back at historic street view, they seem to have messed up the striping around 2013 (https://goo.gl/maps/KHPcJv8HMf2P7njw9), making it seem like the outside lane could continue circulating around the circle at the Veterans Blvd entry, though the arrows still correctly showed both lanes in the roundabout as being able to exit onto Branson Landing, and the inside lane being able to continue around. This striping error was rectified around late 2014 or early 2015 when the inside lane was repaved.

There are now double white lines (https://goo.gl/maps/3p8TTmu9WRfdhif2A) at that point, to [try and] ensure traffic does not circulate around towards Parnell from the outside lane. While double white lines are unusual at roundabouts, at least at points where traffic absolutely must cross them (as traffic entering from Veterans Blvd must to enter the roundabout), vehicles will eventually create a natural gap through tire track degradation.

This all said, the roundabout seems just fine, and I don't see any issues with anything MTJ did. Could you be a little more specific as to the exact problem with the current roundabout? To go back to your original point, I don't see any place where an outer lane yields to an inner lane.

According to this sign, there is at least one point. Hard to tell where it is, though.
https://www.google.com/maps/@36.6496759,-93.2207263,3a,75y,112.83h,78.79t/data=!3m6!1e1!3m4!1sB9cloEhzT16MrLnUeY7Yvw!2e0!7i16384!8i8192

Oh, that's pretty easily explained: the arrows are very poorly aligned. It's just saying the right lane can take the first or second exit, and the left lane can take...something close to the second exit or any exit thereafter.

In fairness, MTJ originally installed this sign (https://goo.gl/maps/qEmpJxtGejrbbnvQA) (blurry but shows both lanes going straight-on and the right lane being able to go right), which was a lot simpler. Not necessarily super accurate, but likely a bit less confusing.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 07, 2023, 06:50:18 AM
As far as I understand, this is a "traffic circle" rather than a "modern roundabout"

What criteria are not met?
Lane arrangement. For example, there is a conflict in exit to Branson Landing at 4 o'clock and exit to Parnell drive at 1 o'clock  - an outer lane heading to Parnell must yield to inner lane exiting to BL.
Just try plotting possible trajectories from Skaggs to those two exits

I don't think that is an unusual circumstance for roundabouts where an entry and exit meet, both with two lanes like here. Traffic intending to continue around the circle can either turn into the inside or outside lane; there is a small yellow painted chevron area (https://goo.gl/maps/BjuCY539WXQH7act6) to encourage traffic to "spiral" into the outer lane, discouraging traffic for Parnell from entering the inner lane and then suddenly dashing across the outside lane to exit.

I would personally consider that a "modern roundabout" without any shadow of a doubt. The fifth leg complicates it a bit, but only slightly. The markings, overall size, deflection, and signage are all consistent with modern roundabout standards. MTJ, the company that designed it, also calls it a roundabout (https://www.mtjengineering.com/project/us-65-branson-landing-blvd-roundabout-branson-mo/).
OK, looked at the signage a bit closer.  Let me put it so - if I ever had to order roundabout design, now I know who should not be asked for a bid.
Signage is too poor to discuss. I agree that with some better minimal stripping and signage it could become a roundabout - but for now it is an exhibit 1 of "why some roundabouts are so bad"

Did a little more digging. The roundabout was built in 2005, and opened in 2005 or early 2006. It opened with striping nearly identical to what we see today. This is the striping  (https://goo.gl/maps/RC2YXNuoox2QhYKfA)at the entry from Veterans Blvd when it first opened; the arrows are messed up but the striping is solid.

Looking back at historic street view, they seem to have messed up the striping around 2013 (https://goo.gl/maps/KHPcJv8HMf2P7njw9), making it seem like the outside lane could continue circulating around the circle at the Veterans Blvd entry, though the arrows still correctly showed both lanes in the roundabout as being able to exit onto Branson Landing, and the inside lane being able to continue around. This striping error was rectified around late 2014 or early 2015 when the inside lane was repaved.

There are now double white lines (https://goo.gl/maps/3p8TTmu9WRfdhif2A) at that point, to [try and] ensure traffic does not circulate around towards Parnell from the outside lane. While double white lines are unusual at roundabouts, at least at points where traffic absolutely must cross them (as traffic entering from Veterans Blvd must to enter the roundabout), vehicles will eventually create a natural gap through tire track degradation.

This all said, the roundabout seems just fine, and I don't see any issues with anything MTJ did. Could you be a little more specific as to the exact problem with the current roundabout? To go back to your original point, I don't see any place where an outer lane yields to an inner lane.

According to this sign, there is at least one point. Hard to tell where it is, though.
https://www.google.com/maps/@36.6496759,-93.2207263,3a,75y,112.83h,78.79t/data=!3m6!1e1!3m4!1sB9cloEhzT16MrLnUeY7Yvw!2e0!7i16384!8i8192

Oh, that's pretty easily explained: the arrows are very poorly aligned. It's just saying the right lane can take the first or second exit, and the left lane can take...something close to the second exit or any exit thereafter.

In fairness, MTJ originally installed this sign (https://goo.gl/maps/qEmpJxtGejrbbnvQA) (blurry but shows both lanes going straight-on and the right lane being able to go right), which was a lot simpler. Not necessarily super accurate, but likely a bit less confusing.
Overall, it's a great example how neither transportation authorities nor private contractors are qualified to design and maintain roundabouts properly. Sorting traffic into lanes by trajectory, and making sure drivers are aware of proper lane use is critical for safe operation. I wonder what is the accident rate there....
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on April 07, 2023, 08:18:46 AM
As far as I understand, this is a "traffic circle" rather than a "modern roundabout"

What criteria are not met?
Lane arrangement. For example, there is a conflict in exit to Branson Landing at 4 o'clock and exit to Parnell drive at 1 o'clock  - an outer lane heading to Parnell must yield to inner lane exiting to BL.
Just try plotting possible trajectories from Skaggs to those two exits

I don't think that is an unusual circumstance for roundabouts where an entry and exit meet, both with two lanes like here. Traffic intending to continue around the circle can either turn into the inside or outside lane; there is a small yellow painted chevron area (https://goo.gl/maps/BjuCY539WXQH7act6) to encourage traffic to "spiral" into the outer lane, discouraging traffic for Parnell from entering the inner lane and then suddenly dashing across the outside lane to exit.

I would personally consider that a "modern roundabout" without any shadow of a doubt. The fifth leg complicates it a bit, but only slightly. The markings, overall size, deflection, and signage are all consistent with modern roundabout standards. MTJ, the company that designed it, also calls it a roundabout (https://www.mtjengineering.com/project/us-65-branson-landing-blvd-roundabout-branson-mo/).
OK, looked at the signage a bit closer.  Let me put it so - if I ever had to order roundabout design, now I know who should not be asked for a bid.
Signage is too poor to discuss. I agree that with some better minimal stripping and signage it could become a roundabout - but for now it is an exhibit 1 of "why some roundabouts are so bad"

Did a little more digging. The roundabout was built in 2005, and opened in 2005 or early 2006. It opened with striping nearly identical to what we see today. This is the striping  (https://goo.gl/maps/RC2YXNuoox2QhYKfA)at the entry from Veterans Blvd when it first opened; the arrows are messed up but the striping is solid.

Looking back at historic street view, they seem to have messed up the striping around 2013 (https://goo.gl/maps/KHPcJv8HMf2P7njw9), making it seem like the outside lane could continue circulating around the circle at the Veterans Blvd entry, though the arrows still correctly showed both lanes in the roundabout as being able to exit onto Branson Landing, and the inside lane being able to continue around. This striping error was rectified around late 2014 or early 2015 when the inside lane was repaved.

There are now double white lines (https://goo.gl/maps/3p8TTmu9WRfdhif2A) at that point, to [try and] ensure traffic does not circulate around towards Parnell from the outside lane. While double white lines are unusual at roundabouts, at least at points where traffic absolutely must cross them (as traffic entering from Veterans Blvd must to enter the roundabout), vehicles will eventually create a natural gap through tire track degradation.

This all said, the roundabout seems just fine, and I don't see any issues with anything MTJ did. Could you be a little more specific as to the exact problem with the current roundabout? To go back to your original point, I don't see any place where an outer lane yields to an inner lane.

According to this sign, there is at least one point. Hard to tell where it is, though.
https://www.google.com/maps/@36.6496759,-93.2207263,3a,75y,112.83h,78.79t/data=!3m6!1e1!3m4!1sB9cloEhzT16MrLnUeY7Yvw!2e0!7i16384!8i8192

Oh, that's pretty easily explained: the arrows are very poorly aligned. It's just saying the right lane can take the first or second exit, and the left lane can take...something close to the second exit or any exit thereafter.

In fairness, MTJ originally installed this sign (https://goo.gl/maps/qEmpJxtGejrbbnvQA) (blurry but shows both lanes going straight-on and the right lane being able to go right), which was a lot simpler. Not necessarily super accurate, but likely a bit less confusing.
Overall, it's a great example how neither transportation authorities nor private contractors are qualified to design and maintain roundabouts properly. Sorting traffic into lanes by trajectory, and making sure drivers are aware of proper lane use is critical for safe operation. I wonder what is the accident rate there....
Pfft.  Plenty of roundabouts out there function perfectly well to make such a generalization false on its face.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on April 07, 2023, 11:00:40 AM
As far as I understand, this is a "traffic circle" rather than a "modern roundabout"

What criteria are not met?
Lane arrangement. For example, there is a conflict in exit to Branson Landing at 4 o'clock and exit to Parnell drive at 1 o'clock  - an outer lane heading to Parnell must yield to inner lane exiting to BL.
Just try plotting possible trajectories from Skaggs to those two exits

I don't think that is an unusual circumstance for roundabouts where an entry and exit meet, both with two lanes like here. Traffic intending to continue around the circle can either turn into the inside or outside lane; there is a small yellow painted chevron area (https://goo.gl/maps/BjuCY539WXQH7act6) to encourage traffic to "spiral" into the outer lane, discouraging traffic for Parnell from entering the inner lane and then suddenly dashing across the outside lane to exit.

I would personally consider that a "modern roundabout" without any shadow of a doubt. The fifth leg complicates it a bit, but only slightly. The markings, overall size, deflection, and signage are all consistent with modern roundabout standards. MTJ, the company that designed it, also calls it a roundabout (https://www.mtjengineering.com/project/us-65-branson-landing-blvd-roundabout-branson-mo/).
OK, looked at the signage a bit closer.  Let me put it so - if I ever had to order roundabout design, now I know who should not be asked for a bid.
Signage is too poor to discuss. I agree that with some better minimal stripping and signage it could become a roundabout - but for now it is an exhibit 1 of "why some roundabouts are so bad"

Did a little more digging. The roundabout was built in 2005, and opened in 2005 or early 2006. It opened with striping nearly identical to what we see today. This is the striping  (https://goo.gl/maps/RC2YXNuoox2QhYKfA)at the entry from Veterans Blvd when it first opened; the arrows are messed up but the striping is solid.

Looking back at historic street view, they seem to have messed up the striping around 2013 (https://goo.gl/maps/KHPcJv8HMf2P7njw9), making it seem like the outside lane could continue circulating around the circle at the Veterans Blvd entry, though the arrows still correctly showed both lanes in the roundabout as being able to exit onto Branson Landing, and the inside lane being able to continue around. This striping error was rectified around late 2014 or early 2015 when the inside lane was repaved.

There are now double white lines (https://goo.gl/maps/3p8TTmu9WRfdhif2A) at that point, to [try and] ensure traffic does not circulate around towards Parnell from the outside lane. While double white lines are unusual at roundabouts, at least at points where traffic absolutely must cross them (as traffic entering from Veterans Blvd must to enter the roundabout), vehicles will eventually create a natural gap through tire track degradation.

This all said, the roundabout seems just fine, and I don't see any issues with anything MTJ did. Could you be a little more specific as to the exact problem with the current roundabout? To go back to your original point, I don't see any place where an outer lane yields to an inner lane.

According to this sign, there is at least one point. Hard to tell where it is, though.
https://www.google.com/maps/@36.6496759,-93.2207263,3a,75y,112.83h,78.79t/data=!3m6!1e1!3m4!1sB9cloEhzT16MrLnUeY7Yvw!2e0!7i16384!8i8192

Oh, that's pretty easily explained: the arrows are very poorly aligned. It's just saying the right lane can take the first or second exit, and the left lane can take...something close to the second exit or any exit thereafter.

In fairness, MTJ originally installed this sign (https://goo.gl/maps/qEmpJxtGejrbbnvQA) (blurry but shows both lanes going straight-on and the right lane being able to go right), which was a lot simpler. Not necessarily super accurate, but likely a bit less confusing.
Overall, it's a great example how neither transportation authorities nor private contractors are qualified to design and maintain roundabouts properly. Sorting traffic into lanes by trajectory, and making sure drivers are aware of proper lane use is critical for safe operation. I wonder what is the accident rate there....
Pfft.  Plenty of roundabouts out there function perfectly well to make such a generalization false on its face.
Yep, some of those perfectly functioning ones are listed here:
https://www.timesunion.com/news/article/The-Capital-Region-s-most-dangerous-intersections-11281734.php

I have to give Albany engineers some credit here, they are not trying to be creative but seem to Ctrl-C Ctrl-V the reference design. Maybe you guys are right, that should be the scope of the DOT engineer job. At least explains why no obviously needed changes are made even in  major reconstruction projects over here...
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on April 11, 2023, 01:42:28 PM
Wow, all this discussion...

For what it's worth, I remember the opening of this roundabout quite well, even though I've never lived in Branson.  My wife and I were married at a church just north of there in April 2006, so the road construction process is pretty firm in my memory.  I think it was just before or after the wedding rehearsal that our maid of honor asked what I thought of the new roundabout, because her father is the one who designed it.  At the time, I wasn't too thrilled with its not having two circulating lanes throughout, and I may have mentioned that.  But anything is better than the five-way stoplight that probably would have been installed otherwise.

When it opened, the southeast leg was little-used, because Branson Landing wasn't quite done being developed, so hardly any traffic needed to go that way instead of right through downtown.

The roundabout's construction coincided with that part of US-65-Business being decommissioned and turned over to the city of Branson.  I heard at the time that this was because the descent from the north was too steep for the roundabout to meet federal roundabout guidelines–therefore the solution was to simply remove its US-Business designation.  I had printed detailed directions to the church and included them in our wedding invitations, to help out-of-town guests find their way from US-65.  My directions said to get off at the US-65-Business exit but, by the time the wedding rolled around, the exit sign no longer had a US-65-Business shield on it at all.  Fortunately, I think everyone still found the church OK.

Honestly, the only real problem I've seen there is that retirees on vacation from Arkansas don't seem to have a clue how to navigate a roundabout to begin with...
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on May 03, 2023, 09:58:20 AM
A second very interesting event in our neck of the woods within past few years:
(https://s.hdnux.com/photos/01/32/56/01/23781499/5/rawImage.jpg)
https://www.timesunion.com/news/article/tanker-truck-crash-closes-road-near-18075691.php?IPID=Times-Union-HP-latest-news
Quote
tanker was carrying a nonflammable chemical
I wonder if that means HF or TMAH? Both are used by GF in large quantities...
Few more historic pictures from the same general area:
(https://s.hdnux.com/photos/44/20/41/9504847/6/rawImage.jpg)
(https://s.hdnux.com/photos/63/15/62/13425798/5/ratio3x2_1200.jpg)

Looks like more hazmat events than I would like to see...
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 14, 2023, 12:00:36 PM
International news about a fatal bus crash that killed 10 in New South Wales Australia.  According to the article it's the biggest road tragedy in NSW since 1989.

Fatal bus crash on a Wine Country Drive roundabout at Greta, in NSW Hunter Valley, driver arrested
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 14, 2023, 12:04:38 PM
International news about a fatal bus crash that killed 10 in New South Wales Australia.  According to the article it's the biggest road tragedy in NSW since 1989.

Is it crash-prone?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 14, 2023, 01:10:19 PM
International news about a fatal bus crash that killed 10 in New South Wales Australia.  According to the article it's the biggest road tragedy in NSW since 1989.

Is it crash-prone?
(looking into the Boeing "PR standard phrases" textbook) - no, this is primarily lack of driver's skills in the third world countries. Operator should recognize full responsibility and ensure better training for the drivers!
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 14, 2023, 01:23:57 PM
third world countries

 :crazy:
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 14, 2023, 10:51:08 PM
The fact that "ten dead" is the worst crash since the 80s is a testament to how much driver training actually occurs in Australia.
Title: Re: Crash prone 'modern roundabouts'
Post by: SEWIGuy on June 15, 2023, 08:47:09 AM
The fact that "ten dead" is the worst crash since the 80s is a testament to how much driver training actually occurs in Australia.

Pretty good for a "third world country."
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 20, 2023, 10:30:16 AM
EPPD say high speed crash killed two men, injured seven in the Upper Valley
https://kvia.com/news/top-stories/2023/06/18/2-dead-multiple-seriously-injured-in-upper-valley-crash/

2 dead and 7 injured after the driver of a Cadillac CTS hit a landscape boulder at the County Club Rd/Memory Dr. roundabout in El Paso over the weekend. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 20, 2023, 10:39:04 AM
EPPD say high speed crash killed two men, injured seven in the Upper Valley
https://kvia.com/news/top-stories/2023/06/18/2-dead-multiple-seriously-injured-in-upper-valley-crash/

2 dead and 7 injured after the driver of a Cadillac CTS hit a landscape boulder at the County Club Rd/Memory Dr. roundabout in El Paso over the weekend. 

But is it crash-prone?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 20, 2023, 11:05:56 AM
I asked ChatGPT if modern roundabouts should be designed with fixed objects in the central island.  By no means am i claiming this is a great answer (reasons given are almost laughable) but I ultimately agree that fixed objects inside the central island of a roundabout are not desired in most circumstances. 

Quote
No, roundabouts should not be designed with fixed objects in the central island. The design principles of roundabouts prioritize safety, efficiency, and smooth traffic flow, and introducing fixed objects in the central island goes against these principles.

Here are some reasons why roundabouts are typically designed without fixed objects in the central island:

Safety: Fixed objects obstruct the visibility of drivers and increase the risk of collisions. Roundabouts are intended to provide clear sightlines and unobstructed views, allowing drivers to see approaching traffic and make informed decisions. Fixed objects can create blind spots and hinder drivers' ability to navigate the roundabout safely.

Traffic flow: Roundabouts are designed to keep traffic moving smoothly with minimal interruptions. Fixed objects can disrupt the flow by causing drivers to slow down, maneuver unpredictably, or hesitate. This can lead to congestion and increase the potential for accidents.

Pedestrian access: Roundabouts often have designated pedestrian crossings or paths within or around them. Placing fixed objects in the central island can impede pedestrian access and make it more challenging for pedestrians to navigate safely.

Emergency vehicle access: Roundabouts are designed to accommodate emergency vehicles, which require clear and unobstructed paths to respond quickly to emergencies. Fixed objects in the central island can hinder the movement of emergency vehicles, delaying their response times.

However, it's worth noting that there may be some exceptions or variations in roundabout designs in specific locations. Local traffic authorities and transportation engineers consider various factors, including traffic volume, available space, and specific site requirements when designing roundabouts. While it's generally preferred to avoid fixed objects in the central island, there may be instances where carefully designed and placed objects are deemed acceptable.

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 20, 2023, 11:10:43 AM
Here's a much better response discussing the issue of fixed objects in roundabouts.  This was published on the ASCE website.

Quote
Central question

The issue of what to put or not put in the roundabout’s central island is debated among traffic engineers. In the mini-roundabouts, the central island is paved precisely so that vehicles – especially large trucks – can drive across the island when necessary. But for larger roundabouts, the central island is often raised several inches or more above the grade of the road and can feature either landscaping or other objects, including sculptures, monuments, and even fountains. Such visual obstructions can “make the drivers focus on the road in front of them instead of looking across the roundabout,”  says Hu.

It can be especially useful to block the view across the central island at night, when the headlights of vehicles approaching the roundabout might give drivers on the opposite side of the circular intersection the false notion that the road continues straight, notes Brian Walsh, P.E., the state traffic design and operations engineer at the Washington State Department of Transportation and the chair of the Transportation Research Board Standing Committee on Roundabouts and Other Intersection Design and Control Strategies.

That is why his department has created design guidance to encourage raising the elevation of some central islands with hill-like mounds – parabolic shapes made from river rocks and other natural materials – to heights of 6 ft or more to block the views of the headlights on approaching vehicles. Together with reflective signage and even illumination of the central island, the approach should help nighttime drivers “realize there’s something in the middle there, so they make better decisions on slowing down as they approach and deflecting or going around,”  Walsh explains. “We want them to see that there’s (something) in the tangent road, that it isn’t straight.”  The geometry ahead of the roundabout intersection can also help drivers see the curvilinear elements of the roundabout intersection.

Other traffic engineers contend that the central island should not have fixed objects such as statues or other hard structures because drivers – admittedly, not always sober or fully in control of their vehicles – are “having very serious collisions”  with such obstacles in roundabouts, says Lalani. Instead, he recommends that there should only be “forgiving things”  in the central island, such as low bushes that can be driven over or things that can be easily knocked aside.

With respect to fixed objects within the central island, the context of the site matters, says Johnson. Fixed objects should be avoided in roundabouts located along high-speed roads – which he defines as roadways with posted speeds of 45 mph or higher. They are less of a concern along low-speed roads where “the probability of hitting the central island is much lower – and so it might be acceptable to risk putting in, for example, a statue or other fixed object”  that may be used to represent the local culture, history, or art, Johnson explains.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 20, 2023, 11:35:38 AM
I asked ChatGPT if modern roundabouts should be designed with fixed objects in the central island.  By no means am i claiming this is a great answer (reasons given are almost laughable) but I ultimately agree that fixed objects inside the central island of a roundabout are not desired in most circumstances. 

Quote
No, roundabouts should not be designed with fixed objects in the central island. The design principles of roundabouts prioritize safety, efficiency, and smooth traffic flow, and introducing fixed objects in the central island goes against these principles.

Here are some reasons why roundabouts are typically designed without fixed objects in the central island:

Safety: Fixed objects obstruct the visibility of drivers and increase the risk of collisions. Roundabouts are intended to provide clear sightlines and unobstructed views, allowing drivers to see approaching traffic and make informed decisions. Fixed objects can create blind spots and hinder drivers' ability to navigate the roundabout safely.

Traffic flow: Roundabouts are designed to keep traffic moving smoothly with minimal interruptions. Fixed objects can disrupt the flow by causing drivers to slow down, maneuver unpredictably, or hesitate. This can lead to congestion and increase the potential for accidents.

Pedestrian access: Roundabouts often have designated pedestrian crossings or paths within or around them. Placing fixed objects in the central island can impede pedestrian access and make it more challenging for pedestrians to navigate safely.

Emergency vehicle access: Roundabouts are designed to accommodate emergency vehicles, which require clear and unobstructed paths to respond quickly to emergencies. Fixed objects in the central island can hinder the movement of emergency vehicles, delaying their response times.

However, it's worth noting that there may be some exceptions or variations in roundabout designs in specific locations. Local traffic authorities and transportation engineers consider various factors, including traffic volume, available space, and specific site requirements when designing roundabouts. While it's generally preferred to avoid fixed objects in the central island, there may be instances where carefully designed and placed objects are deemed acceptable.
Doctor Google suggested some meds for me, but I don't trust PE ChatGPT that much....
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 20, 2023, 01:32:28 PM
Two accidents in two days at same roundabout in The Villages
https://www.villages-news.com/2023/05/01/two-accidents-in-two-days-at-same-roundabout-in-the-villages/

Both accidents involved drivers going through the central island and hitting a tree.

Quote
Wayne Dennis Lender, 72, of 2187 Dorst Lane, was driving a white 2023 Cadillac CTS four-door at 9 p.m. Saturday traveling east on Warm Springs Avenue when his vehicle jumped the curb, hit a tree and flipped onto its roof in the roundabout at Fenney Way, according to an accident report from the Wildwood Police Department. When emergency personnel arrived at the scene, the vehicle was in the middle of the roundabout.

The previous day, 22-year-old Kirsten Michelle Carroll of Bushnell was injured in a single-vehicle crash at the same roundabout. She was driving a silver 2017 Nissan Altima eastbound on Warm Springs Avenue at 10:46 p.m. Friday when her car crashed into a tree in the middle of the roundabout. The airbags deployed in her vehicle and she suffered a possible broken leg as well as lacerations to her face and arms, the accident report said. She was transported by ambulance to UF Health-Leesburg Hospital.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on June 20, 2023, 01:41:37 PM
Two accidents in two days at same roundabout in The Villages
https://www.villages-news.com/2023/05/01/two-accidents-in-two-days-at-same-roundabout-in-the-villages/

Both accidents involved drivers going through the central island and hitting a tree.

Quote
Wayne Dennis Lender, 72, of 2187 Dorst Lane, was driving a white 2023 Cadillac CTS four-door at 9 p.m. Saturday traveling east on Warm Springs Avenue when his vehicle jumped the curb, hit a tree and flipped onto its roof in the roundabout at Fenney Way, according to an accident report from the Wildwood Police Department. When emergency personnel arrived at the scene, the vehicle was in the middle of the roundabout.

The previous day, 22-year-old Kirsten Michelle Carroll of Bushnell was injured in a single-vehicle crash at the same roundabout. She was driving a silver 2017 Nissan Altima eastbound on Warm Springs Avenue at 10:46 p.m. Friday when her car crashed into a tree in the middle of the roundabout. The airbags deployed in her vehicle and she suffered a possible broken leg as well as lacerations to her face and arms, the accident report said. She was transported by ambulance to UF Health-Leesburg Hospital.
Pfft.  So, old people can't handle roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 20, 2023, 01:58:04 PM
Two accidents in two days at same roundabout in The Villages
https://www.villages-news.com/2023/05/01/two-accidents-in-two-days-at-same-roundabout-in-the-villages/

Both accidents involved drivers going through the central island and hitting a tree.

Quote
Wayne Dennis Lender, 72, of 2187 Dorst Lane, was driving a white 2023 Cadillac CTS four-door at 9 p.m. Saturday traveling east on Warm Springs Avenue when his vehicle jumped the curb, hit a tree and flipped onto its roof in the roundabout at Fenney Way, according to an accident report from the Wildwood Police Department. When emergency personnel arrived at the scene, the vehicle was in the middle of the roundabout.

The previous day, 22-year-old Kirsten Michelle Carroll of Bushnell was injured in a single-vehicle crash at the same roundabout. She was driving a silver 2017 Nissan Altima eastbound on Warm Springs Avenue at 10:46 p.m. Friday when her car crashed into a tree in the middle of the roundabout. The airbags deployed in her vehicle and she suffered a possible broken leg as well as lacerations to her face and arms, the accident report said. She was transported by ambulance to UF Health-Leesburg Hospital.
Pfft.  So, old people can't handle roundabouts.
If you add "but we should be building them anyway", that may qualify as a hate crime in NY
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 20, 2023, 02:00:09 PM
Pfft.  So, old people can't handle roundabouts.

One of the drivers was a 22-year old woman.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 20, 2023, 02:05:45 PM
TRAFFIC ALERT | Tanker hauling milk rolls at Walker roundabout
https://www.wzzm13.com/article/traffic/tanker-hauling-milk-rolls-at-walker-roundabout/69-139fc2d1-63d2-47b8-9f83-6468732bb443

This crash happened on June 15th, 2023.  I'm familiar with this roundabout as I took before/after footage of the roundabout.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 20, 2023, 02:08:00 PM
So, old people can't handle roundabouts.

I learned this when they installed roundabouts in Branson.

Especially old people from Arkansas...
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 20, 2023, 02:09:18 PM
TRAFFIC ALERT | Tanker hauling milk rolls at Walker roundabout
https://www.wzzm13.com/article/traffic/tanker-hauling-milk-rolls-at-walker-roundabout/69-139fc2d1-63d2-47b8-9f83-6468732bb443

This crash happened on June 15th, 2023.  I'm familiar with this roundabout as I took before/after footage of the roundabout.
Call me when a truck carrying chocolate spills it. Or something else I may like. Milk isn't worth it...
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on June 20, 2023, 03:09:22 PM
Pfft.  So, old people can't handle roundabouts.

One of the drivers was a 22-year old woman.
Okay, so people who aren't paying attention to where they're driving while driving can't handle roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 26, 2023, 07:45:36 AM
4 vehicles involved in serious head-on crash in Kalamazoo County roundabout
https://www.fox17online.com/news/local-news/kzoo-bc/kalamazoo/4-vehicles-involved-in-head-on-crash-in-kalamazoo-county-roundabout

Reported driver was traveling SB before being involved in a head on crash at the roundabout.  Drivers traveling SB approaching the roundabout are going up a hill which is obstructing the view of the roundabout.  It just looks like you are traveling on a straight 45 mph 4-lane road.

(https://i.imgur.com/ZLihvZF.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on June 26, 2023, 08:44:58 AM
4 vehicles involved in serious head-on crash in Kalamazoo County roundabout
https://www.fox17online.com/news/local-news/kzoo-bc/kalamazoo/4-vehicles-involved-in-head-on-crash-in-kalamazoo-county-roundabout

Reported driver was traveling SB before being involved in a head on crash at the roundabout.  Drivers traveling SB approaching the roundabout are going up a hill which is obstructing the view of the roundabout.  It just looks like you are traveling on a straight 45 mph 4-lane road.

(https://i.imgur.com/ZLihvZF.png)
Pfft.  Looking further on GSV, visual obstruction is not an issue here.  You also then have adequate signage.

Driver error.  Again.
Title: Re: Crash prone 'modern roundabouts'
Post by: SEWIGuy on June 26, 2023, 08:58:50 AM
This topic has gone from "crash prone modern roundabouts" to "crashes at roundabouts."
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 26, 2023, 10:56:01 AM
This topic has gone from "crash prone modern roundabouts" to "crashes at roundabouts."

Exactly.

|tradephoric|:  Do you not even care if these roundabouts are crash-prone anymore?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 26, 2023, 12:28:34 PM
The Sprinkle Road & I-94 roundabout is crash prone.  In 2019 it was the 5th most crash prone roundabout in Michigan with 71 crashes and 2 injuries and the most crash prone roundabout outside of SE Michigan.  In 2020 total crashes went down to 33 but injuries tripled to 6 (and was still the most crash prone roundabout in the state outside of SE Michigan).

Sprinkle Road Roundabout Makes Dubious Top Ten List
https://wkfr.com/sprinkle-road-roundabout-makes-dubious-top-ten-list/
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 26, 2023, 01:03:06 PM
There are more visual clues for NB drivers that a roundabout is approaching as opposed to SB drivers.

NB drivers approaching the roundabout
(https://i.imgur.com/vHbHdVR.png)

SB drivers approaching the roundabout
(https://i.imgur.com/ZLihvZF.png)
 
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 26, 2023, 01:07:27 PM
There are more visual clues for NB drivers that a roundabout is approaching as opposed to SB drivers.

NB drivers approaching the roundabout
(https://i.imgur.com/vHbHdVR.png)

SB drivers approaching the roundabout
(https://i.imgur.com/ZLihvZF.png)
 
can you do everyone a favor and paste google maps link?
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 26, 2023, 01:13:59 PM
can you do everyone a favor and paste google maps link?

https://goo.gl/maps/iVL3vJCTd3X63rRF6

I gotta say, it would be easy to miss.  Just a yellow diamond warning sign, and then the roundabout is at the crest of the hill.
Title: Re: Crash prone 'modern roundabouts'
Post by: HighwayStar on June 26, 2023, 01:30:55 PM
I think I identified my least favorite roundabout implementation on a recent trip.
While driving Arizona 260 and 89A to Jerome I was subjected to something like 12 roundabouts in 17 miles while driving what was obstinately a highway. Much of the route had speed limits of 55 or 45 and every mile or two I had to slow down to screech through a roundabout with some minor road that likely had a fraction of the traffic.

I'm not a roundabout fan generally, but this had to be the worst implementation I have ever seen. Breaking up a major highway where I should be able to set the cruise at 65 and just go where I am going with a dozen of these stupid things. Canceling the cruise, slow down, speed up, etc. Its irritating, definitely wastes gasoline, and seems to serve no other purpose than be cheap and trendy compared to some proper interchanges.  :banghead:
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on June 26, 2023, 01:39:11 PM


The Sprinkle Road & I-94 roundabout is crash prone.  In 2019 it was the 5th most crash prone roundabout in Michigan with 71 crashes and 2 injuries and the most crash prone roundabout outside of SE Michigan.  In 2020 total crashes went down to 33 but injuries tripled to 6 (and was still the most crash prone roundabout in the state outside of SE Michigan).

Wasn't the roundabout completed in 2016?  A fuller set of data would tell a better story, especially if crashes have continued to drop off.

Then again, how many times have we called you out on cherry picking data and you've just ignored us?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 26, 2023, 02:02:40 PM
Wasn't the roundabout completed in 2016?  A fuller set of data would tell a better story, especially if crashes have continued to drop off.

Then again, how many times have we called you out on cherry picking data and you've just ignored us?


Every year the 18 1/2 Mile & Van Dyke roundabout in Sterling Heights shows up on the list of intersections with the most crashes in Michigan.  In 2021 there were 168 total crashes and 17 injuries.  That roundabout was completed in 2005.  After nearly two decades, drivers are still having trouble with that roundabout.  You can blame it on driver error, but as the complexity of these roundabouts increase it can become increasingly difficult for drivers to navigate safely.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 26, 2023, 02:04:54 PM


The Sprinkle Road & I-94 roundabout is crash prone.  In 2019 it was the 5th most crash prone roundabout in Michigan with 71 crashes and 2 injuries and the most crash prone roundabout outside of SE Michigan.  In 2020 total crashes went down to 33 but injuries tripled to 6 (and was still the most crash prone roundabout in the state outside of SE Michigan).

Wasn't the roundabout completed in 2016?  A fuller set of data would tell a better story, especially if crashes have continued to drop off.

Then again, how many times have we called you out on cherry picking data and you've just ignored us?
Is there a way to access full crash data without lengthy work and FOILs, or that is something too specialized? You probably know how that works in NY..
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on June 26, 2023, 02:41:58 PM


The Sprinkle Road & I-94 roundabout is crash prone.  In 2019 it was the 5th most crash prone roundabout in Michigan with 71 crashes and 2 injuries and the most crash prone roundabout outside of SE Michigan.  In 2020 total crashes went down to 33 but injuries tripled to 6 (and was still the most crash prone roundabout in the state outside of SE Michigan).

Wasn't the roundabout completed in 2016?  A fuller set of data would tell a better story, especially if crashes have continued to drop off.

Then again, how many times have we called you out on cherry picking data and you've just ignored us?
Is there a way to access full crash data without lengthy work and FOILs, or that is something too specialized? You probably know how that works in NY..
Tradephoric already got the two years' worth.  That means he can get access to the rest.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 27, 2023, 01:17:42 AM
Wasn't the roundabout completed in 2016?  A fuller set of data would tell a better story, especially if crashes have continued to drop off.

Then again, how many times have we called you out on cherry picking data and you've just ignored us?

Every year the 18 1/2 Mile & Van Dyke roundabout in Sterling Heights shows up on the list of intersections with the most crashes in Michigan.  In 2021 there were 168 total crashes and 17 injuries.  That roundabout was completed in 2005.  After nearly two decades, drivers are still having trouble with that roundabout.  You can blame it on driver error, but as the complexity of these roundabouts increase it can become increasingly difficult for drivers to navigate safely.

It seems quite clear to me that crash rates at multi-lane roundabouts do fluctuate, but are likely higher than whatever multi-lane signalized intersection would have otherwise been built. The Sterling Heights roundabout is a classic example of this: it has not once been modified since opening, and drivers still continue to crash at it, at a remarkably high rate.

Driver error.  Again.

Of course, driver error is the cause of almost all crashes. But why do drivers seem to make more errors at multi-lane roundabouts? And why are the crash rates either barely improving, not improving, or even getting worse?
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on June 27, 2023, 06:59:29 AM
Wasn't the roundabout completed in 2016?  A fuller set of data would tell a better story, especially if crashes have continued to drop off.

Then again, how many times have we called you out on cherry picking data and you've just ignored us?

Every year the 18 1/2 Mile & Van Dyke roundabout in Sterling Heights shows up on the list of intersections with the most crashes in Michigan.  In 2021 there were 168 total crashes and 17 injuries.  That roundabout was completed in 2005.  After nearly two decades, drivers are still having trouble with that roundabout.  You can blame it on driver error, but as the complexity of these roundabouts increase it can become increasingly difficult for drivers to navigate safely.

It seems quite clear to me that crash rates at multi-lane roundabouts do fluctuate, but are likely higher than whatever multi-lane signalized intersection would have otherwise been built. The Sterling Heights roundabout is a classic example of this: it has not once been modified since opening, and drivers still continue to crash at it, at a remarkably high rate.

Driver error.  Again.

Of course, driver error is the cause of almost all crashes. But why do drivers seem to make more errors at multi-lane roundabouts? And why are the crash rates either barely improving, not improving, or even getting worse?
I'm not so sure this is generally true for two-lane roundabouts.  I can point to various examples in NY where there were low-speed crashes at the beginning of the installation, but those rates did drop off.

But sure, locations where crashes remain frequent should be re-evaluated.

But also, getting back to the one roundabout that caused this discussion, despite tradephoric's opinion on the data he presented, crashes dropped by half.  That's why a broader look time-wise is warranted.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 27, 2023, 07:30:23 AM
Wasn't the roundabout completed in 2016?  A fuller set of data would tell a better story, especially if crashes have continued to drop off.

Then again, how many times have we called you out on cherry picking data and you've just ignored us?

Every year the 18 1/2 Mile & Van Dyke roundabout in Sterling Heights shows up on the list of intersections with the most crashes in Michigan.  In 2021 there were 168 total crashes and 17 injuries.  That roundabout was completed in 2005.  After nearly two decades, drivers are still having trouble with that roundabout.  You can blame it on driver error, but as the complexity of these roundabouts increase it can become increasingly difficult for drivers to navigate safely.

It seems quite clear to me that crash rates at multi-lane roundabouts do fluctuate, but are likely higher than whatever multi-lane signalized intersection would have otherwise been built. The Sterling Heights roundabout is a classic example of this: it has not once been modified since opening, and drivers still continue to crash at it, at a remarkably high rate.

Driver error.  Again.

Of course, driver error is the cause of almost all crashes. But why do drivers seem to make more errors at multi-lane roundabouts? And why are the crash rates either barely improving, not improving, or even getting worse?
I'm not so sure this is generally true for two-lane roundabouts.  I can point to various examples in NY where there were low-speed crashes at the beginning of the installation, but those rates did drop off.

But sure, locations where crashes remain frequent should be re-evaluated.

But also, getting back to the one roundabout that caused this discussion, despite tradephoric's opinion on the data he presented, crashes dropped by half.  That's why a broader look time-wise is warranted.
What is the target crash rate for an intersection?  NY average for urban intersections is 0.2-0.5 per million,  looks like 0.2 is a good target number if design safety is a goal.
I am too lazy to look up traffic counts on that thing, but 50k/daily should be on the high side. That is, 1 crash every 100 days, or 3-4 crashes a year is a good target value for intersection evaluation.
We're talking about the drop from 71 to 33 crashes (that drop is in 2020, a covid year), which for me is a drop from "crucify designer in the center of the roundabout" to "firing squad is humane enough"
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 27, 2023, 11:23:56 AM
But also, getting back to the one roundabout that caused this discussion, despite tradephoric's opinion on the data he presented, crashes dropped by half.  That's why a broader look time-wise is warranted.

Thirty-three crashes and 6 injury crashes is significant and would be a target in any safety audits performed in that jurisdiction.  Yes, there was a drop in crashes in 2020 which is the same year everyone was being forced to stay in their homes (in Michigan resident's couldn't even travel freely between their vacation homes under Governor Whitmer's stay-at-home order).
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 27, 2023, 11:49:46 AM
Yes, there was a drop in crashes in 2020 which is the same year everyone was being forced to stay in their homes

Non-fatal crash rates dropped in 2020, but fatal crash rates increased.  The 2020 fatality rate was the highest since 2007, despite a steady decrease over the previous three years.

(https://i.imgur.com/IC0dAa7.jpg)

(https://i.imgur.com/GIrHgtB.png)

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 27, 2023, 11:54:36 AM
The University of Maryland National Transportation Center published a report in 2016 looking at the safety of roundabouts in Arizona.  This report was done before all the multi-lane roundabouts were constructed along Arizona 260 and 89A that HighwayStar referenced a few posts back.  They found that multi-lane roundabouts increase total crashes in Arizona which also mirrors the findings of other states.  While roundabouts can reduce the severity and number of injuries, there were examples in the report of roundabout locations that saw an increase in injury crashes.  It's not a guarantee a complex multi-lane roundabout will be safer than the signalized intersection it replaces.

(https://i.imgur.com/pVjkjjD.png)

Quote
EFFECT OF TRAFFIC ROUNDABOUTS ON SAFETY IN ARIZONA
https://mti.umd.edu/sites/mti.umd.edu/files/documents/NTC2015-SU-R-3%20Michael%20Mamlouk.pdf

EXECUTIVE SUMMARY
Seventeen roundabouts in 5 cities in Arizona were used in the study, out of which 11 single-lane and 16 double-lane. Most of the locations of single-lane roundabouts were controlled by 2-way stop signs before the roundabout installation, while most of the locations of double-lane roundabouts were controlled by signals. Accidents data were collected and broken down into 3 levels: damage, injury, and fatality. Equal number of years were used before and after the roundabout conversion at each location. The most recent AADT value at each location was used to backcalculate the AADT value at the time of roundabout conversion, which is the midpoint of the analysis period. The average rates of accidents, damages, and injuries per year and per year per million vehicles were evaluated. It was found that single-lane roundabouts reduced the accident rate of intersections. However, double-lane roundabouts increased the accident rate of intersections. A decision needs to be made as to either remove double-lane roundabouts or find solutions on how to make these roundabouts safe, such as making geometric improvements or educating the public on how to use them. The results also showed that both single- and double-lane roundabout conversions reduced the severity levels of accidents. Considering both accident rate and severity level, warrants needs to be developed for roundabout conversion for both single- and multi-lane roundabout conversion.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 27, 2023, 12:12:59 PM
Non-fatal crash rates dropped in 2020, but fatal crash rates increased.  The 2020 fatality rate was the highest since 2007, despite a steady decrease over the previous three years.

It sounds like we are in agreement then.  The Sprinkle & I-94 roundabout saw a big drop in total crashes in 2020 which follows the national trend of non-fatal crash rates dropping during the pandemic.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 27, 2023, 12:16:46 PM

Non-fatal crash rates dropped in 2020, but fatal crash rates increased.  The 2020 fatality rate was the highest since 2007, despite a steady decrease over the previous three years.

It sounds like we are in agreement then.  The Sprinkle & I-94 roundabout saw a big drop in total crashes in 2020 which follows the national trend of non-fatal crash rates dropping during the pandemic.

Are there data points for 2021 at that intersection?  National crash rates rebounded in 2021.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on June 27, 2023, 12:23:26 PM

Non-fatal crash rates dropped in 2020, but fatal crash rates increased.  The 2020 fatality rate was the highest since 2007, despite a steady decrease over the previous three years.

It sounds like we are in agreement then.  The Sprinkle & I-94 roundabout saw a big drop in total crashes in 2020 which follows the national trend of non-fatal crash rates dropping during the pandemic.

Are there data points for 2021 at that intersection?  National crash rates rebounded in 2021.
But also, getting back to the one roundabout that caused this discussion, despite tradephoric's opinion on the data he presented, crashes dropped by half.  That's why a broader look time-wise is warranted.

Thirty-three crashes and 6 injury crashes is significant and would be a target in any safety audits performed in that jurisdiction.  Yes, there was a drop in crashes in 2020 which is the same year everyone was being forced to stay in their homes (in Michigan resident's couldn't even travel freely between their vacation homes under Governor Whitmer's stay-at-home order).

Well, good.  We'll see what the jurisdiction does after conducting their safety audit, then.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 27, 2023, 01:39:40 PM
Are there data points for 2021 at that intersection?  National crash rates rebounded in 2021.

I honestly don't know but the roundabout wasn't in the top 20 list of most dangerous Michigan intersections in 2021, so presumably it had fewer than 71 crashes.  Of the 20 most crash prone intersections in the state, 5 of them were roundabouts. 

What Were Michigan’s Most Dangerous Intersections in 2021?
1. 11 MILE RD/I 696 @ VAN DYKE AVE, Warren, 173 Total Crashes, 38 Injuries
2. 10 MILE RD @ I 94, St. Clair Shores, 168 Total Crashes, 42 Injuries
3. 18 1/2 MILE RD @ VAN DYKE AVE, Sterling Heights, 168 Total Crashes, 17 Injuries (Roundabout)
4. MARTIN PKWY @ N PONTIAC TRL, Commerce Township, 140 Total Crashes, 18 Injuries (Roundabout)
5. US 131 @ WEALTHY ST, Grand Rapids, 134 Total Crashes, 26 Injuries
6. ORCHARD LAKE RD @ 14 MILE RD, Farmington Hills, 122 Total Crashes, 15 Injuries (Roundabout)
7. 12 MILE RD @ I 94, St. Clair Shores/Roseville, 121 Total Crashes, 47 Injuries
8. SCHOOLCRAFT RD @ TELEGRAPH RD, Redford Township, 104 Total Crashes, 21 Injuries
9. TELEGRAPH RD @ 12 MILE RD, Southfield, 95 Total Crashes, 15 Injuries
10. 11 MILE RD @ GRATIOT AVE E, Roseville, 92 Total Crashes, 9 Injuries
11. SOUTHFIELD RD @ W 11 MILE RD, Lathrup Village, 91 Total Crashes, 28 Injuries
12. HALL RD @ VAN DYKE AVE, Utica, 86 Total Crashes, 15 Injuries
13. SAGINAW ST @ N HOMER ST, Lansing Township, 85 Total Crashes, 26 Injuries
14. DIX AVE @ M 39, Lincoln Park, 83 Total Crashes, 17 Injuries
15. STATE ST @ ELLSWORTH RD, Ann Arbor, 79 Total Crashes, 1 Injury (Roundabout)
16. MIDDLE BELT RD @ SCHOOLCRAFT RD, Livonia, 78 Total Crashes, 16 Injuries
17. FORD RD @ LILLEY RD, Canton Township, 75 Total Crashes, 32 Injuries
18. FRANKLIN ST SW @ US 131, Grand Rapids, 75 Total Crashes, 10 Injuries
19. 6 MILE RD @ I 96/I 275, Livonia, 73 Total Crashes, 19 Injuries
20. LEE RD @ WHITMORE LAKE RD, Green Oak Township, 71 Total Crashes, 5 Injuries (West Roundabout)

https://www.michiganautolaw.com/legal-resources/most-dangerous-intersections/
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on June 27, 2023, 02:09:34 PM
3. 18 1/2 MILE RD @ VAN DYKE AVE, Sterling Heights, 168 Total Crashes, 17 Injuries (Roundabout)
4. MARTIN PKWY @ N PONTIAC TRL, Commerce Township, 140 Total Crashes, 18 Injuries (Roundabout)
6. ORCHARD LAKE RD @ 14 MILE RD, Farmington Hills, 122 Total Crashes, 15 Injuries (Roundabout)
15. STATE ST @ ELLSWORTH RD, Ann Arbor, 79 Total Crashes, 1 Injury (Roundabout)
20. LEE RD @ WHITMORE LAKE RD, Green Oak Township, 71 Total Crashes, 5 Injuries (West Roundabout)

Looking at Google Maps...

3.  Multi-lane roundabout.  2 lanes circulating.
4.  Multi-lane roundabout.  2 lanes circulating.  Median fencing on two approaches.
6.  Multi-lane roundabout.  2 lanes circulating.
15.  Multi-lane roundabout.  2 lanes circulating.
20.  Not quite 2 lanes circulating, SB exit is 1 lane.  Part of a double roundabout (with SB US-23 ramps).
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 27, 2023, 03:09:10 PM
^There are 3 roundabouts with triple circulating lanes (at least partial) in the entire state of Michigan. They also happen to be 3 of the top 6 most crash prone intersections in the state.  While these roundabouts do carry a lot of traffic, they don't see nearly the same traffic volumes as a major signalized intersection along the state's many 8-lane boulevards (ie. Telegraph, Woodward, Grand River, Northwester, Hall Road, etc).

3. 18 1/2 MILE RD @ VAN DYKE AVE, Sterling Heights, 168 Total Crashes, 17 Injuries (Roundabout)
4. MARTIN PKWY @ N PONTIAC TRL, Commerce Township, 140 Total Crashes, 18 Injuries (Roundabout)
6. ORCHARD LAKE RD @ 14 MILE RD, Farmington Hills, 122 Total Crashes, 15 Injuries (Roundabout)
Title: Re: Crash prone 'modern roundabouts'
Post by: skluth on June 27, 2023, 03:22:57 PM
I was really excited to see the incorporation of roundabouts into the base build of Cities Skylines 2 (https://youtu.be/iRM9rzuBkiY). It seems they don't share the opinions of some here who don't like roundabouts, especially multi-lane roundabouts. I'm sure I'll be using them all over my future cities.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on June 27, 2023, 03:23:53 PM
^There are 3 roundabouts with triple circulating lanes (at least partial) in the entire state of Michigan. They also happen to be 3 of the top 6 most crash prone intersections in the state.  While these roundabouts do carry a lot of traffic, they don't see nearly the same traffic volumes as a major signalized intersection along the state's many 8-lane boulevards (ie. Telegraph, Woodward, Grand River, Northwester, Hall Road, etc).

3. 18 1/2 MILE RD @ VAN DYKE AVE, Sterling Heights, 168 Total Crashes, 17 Injuries (Roundabout)
4. MARTIN PKWY @ N PONTIAC TRL, Commerce Township, 140 Total Crashes, 18 Injuries (Roundabout)
6. ORCHARD LAKE RD @ 14 MILE RD, Farmington Hills, 122 Total Crashes, 15 Injuries (Roundabout)
It may be too much to ask, but adding traffic counts to the list may really help.
I did commute through a 50k daily intersection. It was tough, but generally not very bad. Roundabouts top at 25-30k daily. FHWA says 40k but I am not sure what is that based upon other than wishful thinking.  I suspect those bad roundabouts handle try to process more than that.
Title: Re: Crash prone 'modern roundabouts'
Post by: HighwayStar on June 27, 2023, 09:41:35 PM
The University of Maryland National Transportation Center published a report in 2016 looking at the safety of roundabouts in Arizona.  This report was done before all the multi-lane roundabouts were constructed along Arizona 260 and 89A that HighwayStar referenced a few posts back.  They found that multi-lane roundabouts increase total crashes in Arizona which also mirrors the findings of other states.  While roundabouts can reduce the severity and number of injuries, there were examples in the report of roundabout locations that saw an increase in injury crashes.  It's not a guarantee a complex multi-lane roundabout will be safer than the signalized intersection it replaces.

Quote
EFFECT OF TRAFFIC ROUNDABOUTS ON SAFETY IN ARIZONA
https://mti.umd.edu/sites/mti.umd.edu/files/documents/NTC2015-SU-R-3%20Michael%20Mamlouk.pdf

EXECUTIVE SUMMARY
Seventeen roundabouts in 5 cities in Arizona were used in the study, out of which 11 single-lane and 16 double-lane. Most of the locations of single-lane roundabouts were controlled by 2-way stop signs before the roundabout installation, while most of the locations of double-lane roundabouts were controlled by signals. Accidents data were collected and broken down into 3 levels: damage, injury, and fatality. Equal number of years were used before and after the roundabout conversion at each location. The most recent AADT value at each location was used to backcalculate the AADT value at the time of roundabout conversion, which is the midpoint of the analysis period. The average rates of accidents, damages, and injuries per year and per year per million vehicles were evaluated. It was found that single-lane roundabouts reduced the accident rate of intersections. However, double-lane roundabouts increased the accident rate of intersections. A decision needs to be made as to either remove double-lane roundabouts or find solutions on how to make these roundabouts safe, such as making geometric improvements or educating the public on how to use them. The results also showed that both single- and double-lane roundabout conversions reduced the severity levels of accidents. Considering both accident rate and severity level, warrants needs to be developed for roundabout conversion for both single- and multi-lane roundabout conversion.

Not surprised in the least with those. Although most roundabouts at least seem to replace a regular intersection those were basically barriers on a highway at a junction with some minor road, easy to see how they would be inducing accidents.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on June 30, 2023, 11:24:37 AM
New Volusia County roundabout has seen over 70 crashes in a year
https://www.clickorlando.com/news/investigators/2023/06/29/newly-constructed-roundabout-in-volusia-county-has-seen-over-70-crashes-in-a-year/

The article referenced the roundabout at West Haven Road & Woodland Blvd constructed by FDOT about 5 miles away from the problem roundabout.  That roundabout only had 17 crashes in a 2 year time period.  The biggest difference is that is a 2X1 roundabout (much simpler to navigate) while the other roundabout is a 2X2 roundabout. 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on June 30, 2023, 05:43:28 PM
I love that in the story's video, you can see the news vehicle illegally continuing around the roundabout from the outside lane. At least twice (see 3:15). Perhaps an on-screen graphic where the image briefly goes black on white, with a big "NO" text? :-D

It is interesting to me how much confusion can arise from markings with roundabouts (like in the story, dashed lines being confused for "I can change lanes" rather than just guidance markings). Obviously they're designed to reduce confusion, and mostly I'd guess they do. But some drivers seem to totally misinterpret them. Perhaps we should try and make roundabouts more like signalized intersections, where markings are only used for complex situations, like double turns.

tradephoric, have you looked into the Los Alamitos Roundabout in Long Beach, CA? It recently had lane markings added, and entry widths' reduced. Curious to see how the accident rate has changed. Before 2020, it was easily the largest roundabout in the US, or at least the roundabout with the most entry lanes. And curiously, definitely the largest non-rotary (New England-style) circular intersection without any markings.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 02, 2023, 02:07:59 PM
tradephoric, have you looked into the Los Alamitos Roundabout in Long Beach, CA? It recently had lane markings added, and entry widths' reduced. Curious to see how the accident rate has changed. Before 2020, it was easily the largest roundabout in the US, or at least the roundabout with the most entry lanes. And curiously, definitely the largest non-rotary (New England-style) circular intersection without any markings.

There seems to be way too many arrows within the circle and the arrows that do exist are confusing. I believe roundabout specific arrows should only be used as drivers are approaching the roundabout (if used at all) but shouldn't be used inside the circulating lanes.  Also thru arrows in a modern roundabout should direct drivers to exit the roundabout not to continue around it.  I also don't see the need to have lane arrows right after drivers are exiting the roundabout.  Here is my proposed marking/arrow design compared to what is currently out there.  Not saying my proposed design would be any better but it does follow more modern-roundabout design guidelines (which may or may not be a good thing to adhere to at this particularly large circle). 

CURRENT ROUNDABOUT MARKINGS
(https://i.imgur.com/w6717J0.jpg)

PROPOSED ROUNDABOUT MARKINGS
(https://i.imgur.com/VkxhFiA.jpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on July 03, 2023, 11:15:53 AM
In the left circle it looks like both lanes are allowed to exit the roundabout at the same time but then in the right circle it looks like you are no longer allowed to from the left most circulating lane.  Can someone explain what is going on here?

(https://i.imgur.com/qwrJqOx.png)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 03, 2023, 09:56:47 PM
There seems to be way too many arrows within the circle and the arrows that do exist are confusing. I believe roundabout specific arrows should only be used as drivers are approaching the roundabout (if used at all) but shouldn't be used inside the circulating lanes.  Also thru arrows in a modern roundabout should direct drivers to exit the roundabout not to continue around it.  I also don't see the need to have lane arrows right after drivers are exiting the roundabout.  Here is my proposed marking/arrow design compared to what is currently out there.  Not saying my proposed design would be any better but it does follow more modern-roundabout design guidelines (which may or may not be a good thing to adhere to at this particularly large circle). 

....

Really appreciate the analysis, tradephoric. I also like your redesign.

In the left circle it looks like both lanes are allowed to exit the roundabout at the same time but then in the right circle it looks like you are no longer allowed to from the left most circulating lane.  Can someone explain what is going on here?
https://i.imgur.com/qwrJqOx.png

Nice spot, that is confusing!

This is a great example of how markings, if not done perfectly (and we have not yet found perfect markings, IMO), seem to create a more dangerous situation as drivers can fail to correctly interpret the markings. Eg, "I can change lanes here because the markings are dashed" even though they are dashed to indicate to entering drivers that they can cross over that line, not to allow drivers to stay left across it (in fairness, just writing that makes it seem confusing). The other is the type of driver who sees the roundabout as a huge one-way road, thinking you can only exit from the outside lane...so they just use the outside lane the whole time, even if "turning left".

The old circle, while perhaps not exactly 2009-MUTCD in its design (no surprise having been designed in part by British consultants in the 1990s), did not really hold your hand the way modern roundabouts do. I really do think marking-less roundabouts are something that needs to be tried again. I am growing tired of drivers who are misinterpreting lane lines and creating dangerous situations as a result, and then blaming (rightly or wrongly) the municipality.
Title: Re: Crash prone 'modern roundabouts'
Post by: Occidental Tourist on July 06, 2023, 03:09:11 AM
Oh, it’s a shitshow, all right.  The markings for PCH north coming into the circle are also confusing.  I’ve used the inside lane to enter the circle only to have someone from the outside lane cut over in front of me to try to get into the circle as well.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on July 10, 2023, 01:31:39 PM
New Volusia County roundabout has seen over 70 crashes in a year
https://www.clickorlando.com/news/investigators/2023/06/29/newly-constructed-roundabout-in-volusia-county-has-seen-over-70-crashes-in-a-year/

The article referenced the roundabout at West Haven Road & Woodland Blvd constructed by FDOT about 5 miles away from the problem roundabout.  That roundabout only had 17 crashes in a 2 year time period.  The biggest difference is that is a 2X1 roundabout (much simpler to navigate) while the other roundabout is a 2X2 roundabout.

Horrendous bike lane design. They direct people onto the sidewalk path but didnt build ramps

On
https://goo.gl/maps/HvqxerJPBRYYhmBe8

Off
https://goo.gl/maps/BMbASEeeTsKSLsAC8


In the on link, you can see bikes are forced to make a right turn


They got one corner right.

https://goo.gl/maps/WfX6thrF1oKF2v6b6

https://goo.gl/maps/a7cuMcbCY6eU7UL87

A licensed professional stamped this?
Title: Re: Crash prone 'modern roundabouts'
Post by: JoePCool14 on July 11, 2023, 10:08:07 AM
It really does boggle the mind sometimes how stuff makes it past QAQC. No one notices these things throughout the process? Or maybe they do notice them and can't be bothered to fix them. Lazy.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on July 11, 2023, 10:40:12 AM
It really does boggle the mind sometimes how stuff makes it past QAQC. No one notices these things throughout the process? Or maybe they do notice them and can't be bothered to fix them. Lazy.
There was a very interesting article at some point - and the more I look the more I find it convincing:
They call it "Hollywood effect" - people are used to happy endings. It will be all right, so why escalate things, why change plans, initiate conflicts?
That was in the context of lukewarm CDC response to early covid situation; but there are too many examples I can see. People are not expecting that they will fail, so.. why bother too much? 
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 19, 2023, 10:04:55 PM
Florida DOT built a new roundabout at SR-972 and SW 15 Rd in Miami (https://goo.gl/maps/Ky4NJtqW4Hgb8pDZA), so-called the "Coral Way Roundabout".

Not exactly ground-breaking, I know. The unusual part: several of the crossings are completely signalized with standard RYG signals, no RRFBs or HAWKs. Most of the signals are even post-mounted at eye-level with pedestrians and cars, which is fairly unusual for Florida, although understandable here with the I-95 overpass.

You can see everything in this YouTube video posted by FDOT:

Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on July 19, 2023, 11:16:29 PM
Florida DOT built a new roundabout at SR-972 and SW 15 Rd in Miami (https://goo.gl/maps/Ky4NJtqW4Hgb8pDZA), so-called the "Coral Way Roundabout".

Not exactly ground-breaking, I know. The unusual part: several of the crossings are completely signalized with standard RYG signals, no RRFBs or HAWKs. Most of the signals are even post-mounted at eye-level with pedestrians and cars, which is fairly unusual for Florida, although understandable here with the I-95 overpass.

You can see everything in this YouTube video posted by FDOT:

Look like pelicans to me, which is good.  Wonder why they didn't go with RRFBs, though.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on July 21, 2023, 10:04:36 PM
Look like pelicans to me, which is good.  Wonder why they didn't go with RRFBs, though.

I wondered that too, RRFBs are by far the most common "upgrade" at roundabout crossings, this roundabout seems like a shoo-in for them as much as any other. Could just be they're performing a test.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on August 18, 2023, 03:07:18 PM
The Sprinkle Road & I-94 roundabout is crash prone.  In 2019 it was the 5th most crash prone roundabout in Michigan with 71 crashes and 2 injuries and the most crash prone roundabout outside of SE Michigan.  In 2020 total crashes went down to 33 but injuries tripled to 6 (and was still the most crash prone roundabout in the state outside of SE Michigan).

Sprinkle Road Roundabout Makes Dubious Top Ten List
https://wkfr.com/sprinkle-road-roundabout-makes-dubious-top-ten-list/

Sprinkle Road roundabout yet again the most crash prone intersection in Kalamazoo County last year, this time with 68 total crashes and 7 injury crashes. 

10 Kalamazoo County intersections with the most crashes in 2022 — a roundabout is No. 1
https://www.mlive.com/news/kalamazoo/2023/08/10-kalamazoo-county-intersections-with-the-most-crashes-in-2022-a-roundabout-is-no-1.html
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 19, 2023, 03:35:27 AM
Repeat after me:

Roundabouts reduce all crashes up to 47 percent.

Roundabouts reduce all crashes up to 47 percent.

Roundabouts reduce all crashes up to 47 percent.

*eye twitch*
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 19, 2023, 10:25:40 PM
WSDOT's new roundabout project at WA-9/WA-204 in Lake Stevens has been met with online ridicule, making the rounds all over Twitter X and Facebook.

https://twitter.com/the_transit_guy/status/1692571700045529543

https://twitter.com/KostelecPlan/status/1692581072804937743
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on August 19, 2023, 10:43:04 PM
WSDOT's new roundabout project at WA-9/WA-204 in Lake Stevens has been met with online ridicule, making the rounds all over Twitter X and Facebook.

https://twitter.com/the_transit_guy/status/1692571700045529543

https://twitter.com/KostelecPlan/status/1692581072804937743

When broken down to an individual intersection basis, it's not bad overall. 

It's like when someone posts an aerial shot of a spaghetti-type interchange.  Sure it may look complicated overall, but for most motorists they only need to take a single ramp that's probably signed well.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on August 20, 2023, 02:33:28 AM
When broken down to an individual intersection basis, it's not bad overall. 

It's like when someone posts an aerial shot of a spaghetti-type interchange.  Sure it may look complicated overall, but for most motorists they only need to take a single ramp that's probably signed well.

Well, it's just roundabouts. The hate seems to be engineering-focused:

* too many slip lanes
* the frontage road on the left (of my image; east side of WA-9) is not necessary and should have been removed
* excessive chicanes on the entrance legs.

While the southbound WA-9 to westbound WA-204 slip lane is necessary because tons of cars go that direction, the other two slip lanes are just stupid and serve no real purpose. In fact, I'm almost certain they were installed because WSDOT wanted right turn lanes, but didn't want pedestrians to have to cross three lanes at once. So they separated the right turn lane from the through lanes, creating a slip lane.

Regarding the chicanes, WSDOT massively overuses chicanes. I understand their purpose (even if, in practice, they are easily ignored because the lanes are laughably wide), but they are not always necessary. In fact, in this entire complex, chicanes are really only "needed" entering the northern roundabout from the north, and entering the southern roundabout from the south. Every other approach is generally already low speed. In fairness to WSDOT here, though, I think only the entrances from WA-9 have chicanes; the image suggests other roundabout entrance are more straight-on entry.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on August 28, 2023, 07:27:51 PM
Sure it may look complicated overall, but for most motorists they only need to take a single ramp that's probably signed well.

And for people navigating this outside a motor vehicle?
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on September 01, 2023, 05:48:17 PM
I don't know how true this is (maybe there's a cross walk just off frame) but i liked this picture highlighting how convenient it is for pedestrians to cross the street.

(https://pbs.twimg.com/media/F31fVLdagAAjqEO?format=jpg&name=4096x4096)
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on September 01, 2023, 06:01:04 PM
Extremely misleading. WA-9 has no pedestrian facilities along it. The ghost roundabout in the picture below is the roundabout in the above photo:

(https://live.staticflickr.com/65535/53157091452_141700b84a_o.png)
WA-9 Lake Stevens Looking South(east) (https://flic.kr/p/2oZiZjL) by Jacob Root (https://www.flickr.com/photos/62537709@N03/), on Flickr
Title: Re: Crash prone 'modern roundabouts'
Post by: Occidental Tourist on September 02, 2023, 03:00:46 AM
Looking at the original configuration, this seems like a solution searching for a problem.
Title: Re: Crash prone 'modern roundabouts'
Post by: jamess on September 04, 2023, 10:00:29 PM
Extremely misleading. WA-9 has no pedestrian facilities along it. The ghost roundabout in the picture below is the roundabout in the above photo:

While it is certainly an improvement for pedestrians (some accommodations, versus previously none), that doesnt mean its a GOOD design for pedestrians.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 03, 2023, 05:53:59 PM
The Michigan Department of Transportation performed a study evaluating the performance and safety effectiveness of roundabouts throughout the state.  The 8 triple lane roundabouts studied saw a big increase in total crashes, a slight increase in injury crashes, and a reduction in KA crashes.

(https://i.imgur.com/IsbzZO2.png)
https://mdotjboss.state.mi.us/TSSD/tssdResearchAdminDetails.htm?keyword=SPR-1725
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 04, 2023, 10:18:19 AM
The Michigan Department of Transportation performed a study evaluating the performance and safety effectiveness of roundabouts throughout the state.  The 8 triple lane roundabouts studied saw a big increase in total crashes, a slight increase in injury crashes, and a reduction in KA crashes.

(https://i.imgur.com/IsbzZO2.png)
https://mdotjboss.state.mi.us/TSSD/tssdResearchAdminDetails.htm?keyword=SPR-1725

Thanks for the link!  The "Spotlight" document had a nice section called "RESULTS".  Here are some takeaways from the study that they report in that section:

— Crashes occur more often at roundabouts than at traditional intersections.
— Crashes at roundabouts are less likely to result in severe injuries or deaths.

— Roundabouts were found to reduce traffic delays by more than 63 percent on average
— Estimated fuel savings were more than $69 per vehicle per year
— Converting an existing intersection to a roundabout generally results in benefits six times greater than the costs.

— Drivers accepted smaller gaps at...
    * roundabouts with more than one lane
    * three-legged roundabouts
    * those located in rural areas.

— Roundabouts on interchanges, where speeds tend to be higher, had the lowest yielding rates.
— Roundabouts with pedestrian hybrid beacons produced higher yield rates.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 04, 2023, 10:24:29 AM
— Estimated fuel savings were more than $69 per vehicle per year

My bullshitmeter broke on this.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on October 04, 2023, 10:50:35 AM
— Estimated fuel savings were more than $69 per vehicle per year

My bullshitmeter broke on this.
Reminds me of economic benefit estimates of converting freeways to meet Interstate Highway System standards.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 04, 2023, 10:57:35 AM
— Estimated fuel savings were more than $69 per vehicle per year

My bullshitmeter broke on this.
Reminds me of economic benefit estimates of converting freeways to meet Interstate Highway System standards.
There are good reasons why scientific community switched to an independent peer review for publications.
There are some quite real facepalms in the report.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 04, 2023, 11:17:21 AM

— Estimated fuel savings were more than $69 per vehicle per year

My bullshitmeter broke on this.

Why?  Doing some back-of-the-envelope math here...

Assuming 12,000 miles driven per year...
Assuming fuel economy of 25 miles per gallon...
Makes 480 gallons of gas purchased per year...
Assuming $3.50 per gallon...
Makes $1680 spent on gas per year.

A savings of $69 per year...
Makes $1611 spent on gas per year...
Assuming $3.50 per gallon...
Makes 460.286 gallons of gas purchased per year...
Assuming 12,000 miles driven per year...
Makes 26.071 miles per gallon.

You don't think that eliminating a stoplight could result in a driver's fuel economy being improved by 1.071 mpg?
An improvement of 4.3% is unbelievable?

Maybe, maybe not.  If that stoplight were on my regular daily commute, I could imagine a savings like that.

Or did I do some bad math somewhere in there?  Math corrected.
Title: Re: Crash prone 'modern roundabouts'
Post by: 7/8 on October 04, 2023, 11:23:51 AM

— Estimated fuel savings were more than $69 per vehicle per year

My bullshitmeter broke on this.

Why?  Doing some back-of-the-envelope math here...

Assuming 12,000 miles driven per year...
Assuming fuel economy of 25 miles per gallon...
Makes 480 gallons of gas purchased per year...
Assuming $3.50 per gallon...
Makes $1680 spent on gas per year.

A savings of $69 per year...
Makes $1611 spent on gas per year...
Assuming $3.50 per gallon...
Makes 460.286 gallons of gas purchased per year...
Assuming 12,000 miles driven per year...
Makes 24.985 miles per gallon.

You don't think that eliminating a stoplight could result in a driver's fuel economy being improved by 0.015 mpg?
An improvement of 0.06% is unbelievable?
Why?

Or did I do some bad math somewhere in there?

I think something went wrong at the end with your math: 12 000 miles / 460.286 gallons = 26.07 miles per gallon (improvement of 1.07 mpg)
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 04, 2023, 11:30:06 AM
I think something went wrong at the end with your math: 12 000 miles / 460.286 gallons = 26.07 miles per gallon (improvement of 1.07 mpg)

Fixed.  Thank you.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 04, 2023, 03:16:08 PM
The crash severity distribution before and after roundabout chart really caught my eye.

Quote
One of the primary safety benefits of roundabouts is that they tend to reduce crash severities due to lower speeds at which drivers are forced to enter the intersection and traffic flowing around a central circle in only one direction. As such, the crash severity distribution before and after roundabout construction was also investigated.

(https://i.imgur.com/334sWY0.png)

Take these two intersections:

Intersection A:  10 injury crashes, 30 total crashes
Intersection B:  10 injury crashes, 100 total crashes

It's not enough to say that the percentage of injury crashes at intersection B is lower so it must be safer.  Yes, roundabouts reduce crash severity but there's just so many more crashes occurring at these complex roundabouts that the actual number of injuries is roughly the same (as seen in the triple-lane roundabouts analyzed in the study which actually had more injury accidents than the before condition). 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 04, 2023, 05:25:41 PM
It's not enough to say that the percentage of injury crashes at intersection B is lower so it must be safer.  Yes, roundabouts reduce crash severity but there's just so many more crashes occurring at these complex roundabouts that the actual number of injuries is roughly the same (as seen in the triple-lane roundabouts analyzed in the study which actually had more injury accidents than the before condition). 

You know, considering how much you hate it when people use single-lane roundabouts as a stand-in for all roundabouts when it comes to safety data, I'd have thought you would avoid using triple-lane roundabouts as a stand-in for all roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 04, 2023, 05:49:20 PM
It's not enough to say that the percentage of injury crashes at intersection B is lower so it must be safer.  Yes, roundabouts reduce crash severity but there's just so many more crashes occurring at these complex roundabouts that the actual number of injuries is roughly the same (as seen in the triple-lane roundabouts analyzed in the study which actually had more injury accidents than the before condition). 

You know, considering how much you hate it when people use single-lane roundabouts as a stand-in for all roundabouts when it comes to safety data, I'd have thought you would avoid using triple-lane roundabouts as a stand-in for all roundabouts.
It's just a strike against the quality of the report. And their normalization is borderline fraud. I would certainly say "major edits" as a reviewer if facing something like that.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 04, 2023, 08:26:00 PM
It's not enough to say that the percentage of injury crashes at intersection B is lower so it must be safer.  Yes, roundabouts reduce crash severity but there's just so many more crashes occurring at these complex roundabouts that the actual number of injuries is roughly the same (as seen in the triple-lane roundabouts analyzed in the study which actually had more injury accidents than the before condition). 

You know, considering how much you hate it when people use single-lane roundabouts as a stand-in for all roundabouts when it comes to safety data, I'd have thought you would avoid using triple-lane roundabouts as a stand-in for all roundabouts.

I didn't say there's so many more crashes occurring at all roundabouts... i said there are so many more crashes occurring at these complex roundabouts.  I've always tried to preference my comments about high crash rates in regards to complex (2X2 and 3X2) roundabouts. 
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 05, 2023, 09:57:55 AM
I didn't say there's so many more crashes occurring at all roundabouts... i said there are so many more crashes occurring at these complex roundabouts.  I've always tried to preference my comments about high crash rates in regards to complex (2X2 and 3X2) roundabouts. 

You're right, I didn't read your post carefully enough.  Sorry, there.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 05, 2023, 12:43:49 PM
No worries, I still am opposed to single-lane roundabouts with fixed objects in the central island but that's a separate issue.  For the most parts single-lane roundabouts work well.  To that point, it looks like Toledo did a great job redesigning the Detroit/Cherry Street roundabout reducing it to one lane for the Cherry Street approach.  There's now no confusion how to navigate through the roundabout.

(https://i.imgur.com/QQVmpvF.png)
https://www.google.com/maps/@41.6859893,-83.5564183,116m/data=!3m1!1e3?entry=ttu

Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on October 12, 2023, 11:33:12 AM
'Put a stoplight'; Man shares story after crashing at Maricopa County's worst intersection
https://www.12news.com/article/news/local/man-shares-story-after-crashing-at-maricopa-county-worst-intersection/75-61203028-076e-48a8-be79-11db4689d692

Most crashes of any intersection in Maricopa County is the 2x2 roundabout at 99TH Avenue & Lower Buckeye Road.  It had 411 crashes from 2017 thru 2021, which is 148 more crashes than the next most crash prone intersection in the county (67TH Avenue & Indian School Road).  Another example of a 2x2 roundabout failing at reducing crashes. I believe it's the only full blown 2x2 roundabout in the county which helps explain why there are so many more crashes at this complex roundabout compared to other multi-lane roundabouts in the county.

(https://i.imgur.com/OA2E3oJ.png)
https://azmag.gov/Portals/0/Documents/TSC_2017-04-18_List-of-Top-100-Intersections-Ranked-by-Crash-Risk.pdf?ver=2021-01-27-083723-227
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on October 12, 2023, 03:35:19 PM
'Put a stoplight'; Man shares story after crashing at Maricopa County's worst intersection
https://www.12news.com/article/news/local/man-shares-story-after-crashing-at-maricopa-county-worst-intersection/75-61203028-076e-48a8-be79-11db4689d692

Most crashes of any intersection in Maricopa County is the 2x2 roundabout at 99TH Avenue & Lower Buckeye Road.  It had 411 crashes from 2017 thru 2021, which is 148 more crashes than the next most crash prone intersection in the county (67TH Avenue & Indian School Road).  Another example of a 2x2 roundabout failing at reducing crashes. I believe it's the only full blown 2x2 roundabout in the county which helps explain why there are so many more crashes at this complex roundabout compared to other multi-lane roundabouts in the county.

(https://i.imgur.com/OA2E3oJ.png)
https://azmag.gov/Portals/0/Documents/TSC_2017-04-18_List-of-Top-100-Intersections-Ranked-by-Crash-Risk.pdf?ver=2021-01-27-083723-227
So...Arizonans can't handle roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 12, 2023, 04:11:16 PM
'Put a stoplight'; Man shares story after crashing at Maricopa County's worst intersection
https://www.12news.com/article/news/local/man-shares-story-after-crashing-at-maricopa-county-worst-intersection/75-61203028-076e-48a8-be79-11db4689d692

Most crashes of any intersection in Maricopa County is the 2x2 roundabout at 99TH Avenue & Lower Buckeye Road.  It had 411 crashes from 2017 thru 2021, which is 148 more crashes than the next most crash prone intersection in the county (67TH Avenue & Indian School Road).  Another example of a 2x2 roundabout failing at reducing crashes. I believe it's the only full blown 2x2 roundabout in the county which helps explain why there are so many more crashes at this complex roundabout compared to other multi-lane roundabouts in the county.

(https://i.imgur.com/OA2E3oJ.png)
https://azmag.gov/Portals/0/Documents/TSC_2017-04-18_List-of-Top-100-Intersections-Ranked-by-Crash-Risk.pdf?ver=2021-01-27-083723-227
So...Arizonan DOT engineers can't handle roundabouts.
FTFY
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 12, 2023, 04:19:06 PM
When a football team loses, it's always the coach's fault.

When a roundabout has a lot of crashes, it's always the engineer's fault.
Title: Re: Crash prone 'modern roundabouts'
Post by: JREwing78 on October 12, 2023, 06:42:28 PM
I blame idiot drivers. Other countries do crazy things with roundabouts and don't seem to have nearly as much trouble.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 12, 2023, 06:52:43 PM
I blame idiot drivers. Other countries do crazy things with roundabouts and don't seem to have nearly as much trouble.
But they have better engineering by now...
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 13, 2023, 10:41:50 AM
I blame idiot drivers. Other countries do crazy things with roundabouts and don't seem to have nearly as much trouble.

I'm not sure you can separate the two.  Engineering does not exist in a vacuum:  it exists within culture, and any roundabout design will play off that culture's history and values and expectations and norms.  It's possible that crazy roundabouts in other countries fare better because drivers in those other countries are better prepared—not by classroom instruction or personal discipline, but by aspects of their shared culture—to safely deal with them.  It's possible that some aspect of American culture just thwarts the safe performance of complex roundabout designs, no matter how well engineered they are.

I do find it strange that Americans have such trouble with well-designed, clearly marked, sufficiently signed multi-lane roundabouts—while drivers in third-world countries with practically zero drivers' education and much less strict traffic enforcement seem to have no trouble with poorly designed, unmarked multi-lane roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 13, 2023, 11:37:32 AM
I blame idiot drivers. Other countries do crazy things with roundabouts and don't seem to have nearly as much trouble.

I'm not sure you can separate the two.  Engineering does not exist in a vacuum:  it exists within culture, and any roundabout design will play off that culture's history and values and expectations and norms.  It's possible that crazy roundabouts in other countries fare better because drivers in those other countries are better prepared—not by classroom instruction or personal discipline, but by aspects of their shared culture—to safely deal with them.  It's possible that some aspect of American culture just thwarts the safe performance of complex roundabout designs, no matter how well engineered they are.

I do find it strange that Americans have such trouble with well-designed, clearly marked, sufficiently signed multi-lane roundabouts—while drivers in third-world countries with practically zero drivers' education and much less strict traffic enforcement seem to have no trouble with poorly designed, unmarked multi-lane roundabouts.
Two things - proper signage, which is less than guaranteed; appropriate placement in terms of traffic volume; and proper design - especially size-wise.
There is a strong push for tiny roundabouts (because ROW) to handle more traffic than feasible. The result is, well, somewhat predictable
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 13, 2023, 11:41:41 AM
There is a strong push for tiny roundabouts (because ROW) to handle more traffic than feasible. The result is, well, somewhat predictable

I seem to recall, maybe 15 or 20 years ago now, that the push for smaller roundabouts was being touted for safety benefits more than anything:  the smaller ICD made for lower speeds, which in turn made for safer performance.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 13, 2023, 12:29:34 PM
There is a strong push for tiny roundabouts (because ROW) to handle more traffic than feasible. The result is, well, somewhat predictable

I seem to recall, maybe 15 or 20 years ago now, that the push for smaller roundabouts was being touted for safety benefits more than anything:  the smaller ICD made for lower speeds, which in turn made for safer performance.
And I don't think I saw real research on that. Flipped trucks reports  suggest at least some wishful thinking  in lieu of information
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 13, 2023, 12:34:43 PM


There is a strong push for tiny roundabouts (because ROW) to handle more traffic than feasible. The result is, well, somewhat predictable

I seem to recall, maybe 15 or 20 years ago now, that the push for smaller roundabouts was being touted for safety benefits more than anything:  the smaller ICD made for lower speeds, which in turn made for safer performance.

And I don't think I saw real research on that. Flipped trucks reports  suggest at least some wishful thinking  in lieu of information

You may be right about that.  My memory is fuzzy, but I don't remember seeing much research to go along with it either.
Title: Re: Crash prone 'modern roundabouts'
Post by: JREwing78 on October 13, 2023, 01:58:28 PM
I blame idiot drivers. Other countries do crazy things with roundabouts and don't seem to have nearly as much trouble.

I'm not sure you can separate the two.  Engineering does not exist in a vacuum:  it exists within culture, and any roundabout design will play off that culture's history and values and expectations and norms.  It's possible that crazy roundabouts in other countries fare better because drivers in those other countries are better prepared—not by classroom instruction or personal discipline, but by aspects of their shared culture—to safely deal with them.  It's possible that some aspect of American culture just thwarts the safe performance of complex roundabout designs, no matter how well engineered they are.

I do find it strange that Americans have such trouble with well-designed, clearly marked, sufficiently signed multi-lane roundabouts—while drivers in third-world countries with practically zero drivers' education and much less strict traffic enforcement seem to have no trouble with poorly designed, unmarked multi-lane roundabouts.
Two things - proper signage, which is less than guaranteed; appropriate placement in terms of traffic volume; and proper design - especially size-wise.
There is a strong push for tiny roundabouts (because ROW) to handle more traffic than feasible. The result is, well, somewhat predictable

Anecdotally, the two main issues I see with folks navigating roundabouts:
- Not understanding who has right-of-way (i.e. the folks already in the roundabout)
- Not understanding what direction you can go from which lane.

The first problem is pure stupidity. I've never come across a roundabout that didn't have clear signage showing that people entering have to yield, and yet folks seem to have considerable trouble with that concept.

The second problem is a little more understandable - namely, cars already in the roundabout crossing paths because the inside lane tries to exit, but the outside lane tries to stay in the roundabout. Some of them angle the lanes in the roundabout to make it clearer which lane must exit, where the inside lane transitions outside. A lot of multi-lane roundabouts don't. If you sit someone down and make them think logically about how it works before they drive it, they're fine. But, on the spot, relying on instinct, they make the wrong decision. And, let's face it - most folks here driving roundabouts are relying on these faulty instincts.

It's a reflection on our driving culture - because we disinvested in public transportation 70 years ago in favor of the car, we have a whole group of people who have no business driving a car forced to do so. This lack of public transportation makes us hesitant to deny people access to driving, even when they're dangerous drivers who shouldn't be behind the wheel. Meanwhile, in places with robust public transportation, they can afford to be stingy about handing out a driver's license, and that tends to weed out bad drivers.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 13, 2023, 03:47:53 PM
I blame idiot drivers. Other countries do crazy things with roundabouts and don't seem to have nearly as much trouble.

I'm not sure you can separate the two.  Engineering does not exist in a vacuum:  it exists within culture, and any roundabout design will play off that culture's history and values and expectations and norms.  It's possible that crazy roundabouts in other countries fare better because drivers in those other countries are better prepared—not by classroom instruction or personal discipline, but by aspects of their shared culture—to safely deal with them.  It's possible that some aspect of American culture just thwarts the safe performance of complex roundabout designs, no matter how well engineered they are.

I do find it strange that Americans have such trouble with well-designed, clearly marked, sufficiently signed multi-lane roundabouts—while drivers in third-world countries with practically zero drivers' education and much less strict traffic enforcement seem to have no trouble with poorly designed, unmarked multi-lane roundabouts.
Two things - proper signage, which is less than guaranteed; appropriate placement in terms of traffic volume; and proper design - especially size-wise.
There is a strong push for tiny roundabouts (because ROW) to handle more traffic than feasible. The result is, well, somewhat predictable

Anecdotally, the two main issues I see with folks navigating roundabouts:
- Not understanding who has right-of-way (i.e. the folks already in the roundabout)
- Not understanding what direction you can go from which lane.

The first problem is pure stupidity. I've never come across a roundabout that didn't have clear signage showing that people entering have to yield, and yet folks seem to have considerable trouble with that concept.

The second problem is a little more understandable - namely, cars already in the roundabout crossing paths because the inside lane tries to exit, but the outside lane tries to stay in the roundabout. Some of them angle the lanes in the roundabout to make it clearer which lane must exit, where the inside lane transitions outside. A lot of multi-lane roundabouts don't. If you sit someone down and make them think logically about how it works before they drive it, they're fine. But, on the spot, relying on instinct, they make the wrong decision. And, let's face it - most folks here driving roundabouts are relying on these faulty instincts.

It's a reflection on our driving culture - because we disinvested in public transportation 70 years ago in favor of the car, we have a whole group of people who have no business driving a car forced to do so. This lack of public transportation makes us hesitant to deny people access to driving, even when they're dangerous drivers who shouldn't be behind the wheel. Meanwhile, in places with robust public transportation, they can afford to be stingy about handing out a driver's license, and that tends to weed out bad drivers.
There is a lot to say here...
First of all, using roundabout in excessive traffic locations results in inevitable reduction of safety margins. Drivers from the entry downstream of major one have to take chances into smaller gaps.
Second - yes, things have to be largely intuitive. Humans are pretty shitty in response  under stress, and looks like whatever had been known about that in 20th century is thoroughly forgotten. For one, a major US engineering company - Boeing - is pretty much in the toilet because they couldn't properly design "user interface" in fourth iteration of original 1960s design (737 max), nor showed institutional knowledge to build a solid case for UI of re-desing of 1990s design (777x)
Roundabouts follow similar scenario - things are designed without understanding normal human response. Then, of course, it's human fault...
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on October 13, 2023, 05:44:54 PM
Other countries do crazy things with roundabouts and don't seem to have nearly as much trouble.

Do we know this for sure?
Title: Re: Crash prone 'modern roundabouts'
Post by: Occidental Tourist on October 14, 2023, 08:20:43 AM
This is a poorly designed roundabout for the area, though, which is formerly rural transitioning to suburban with major routes emphasizing speed. The approach speed to this roundabout is 45 mph with no attempt at traffic calming before entry.  Two of the directions have driveways on the right just before the roundabout entrance, creating a driver distraction.  The design emphasizes continuity of speed for thru traffic by making thru movements subject to very little deviation angle.

They need to increase the deviation angle on entry as a start.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on October 14, 2023, 10:12:37 AM
This is a poorly designed roundabout for the area, though, which is formerly rural transitioning to suburban with major routes emphasizing speed. The approach speed to this roundabout is 45 mph with no attempt at traffic calming before entry.  Two of the directions have driveways on the right just before the roundabout entrance, creating a driver distraction.  The design emphasizes continuity of speed for thru traffic by making thru movements subject to very little deviation angle.

They need to increase the deviation angle on entry as a start.
The first question to ask is if there is actually enough benefits in going to a roundabout, or smaller changes, like adding turn lanes, have better cost-benefit ratio...
Title: Re: Crash prone 'modern roundabouts'
Post by: ErmineNotyours on October 14, 2023, 11:35:38 PM
I think I identified my least favorite roundabout implementation on a recent trip.
While driving Arizona 260 and 89A to Jerome I was subjected to something like 12 roundabouts in 17 miles while driving what was obstinately a highway. Much of the route had speed limits of 55 or 45 and every mile or two I had to slow down to screech through a roundabout with some minor road that likely had a fraction of the traffic.

I'm not a roundabout fan generally, but this had to be the worst implementation I have ever seen. Breaking up a major highway where I should be able to set the cruise at 65 and just go where I am going with a dozen of these stupid things. Canceling the cruise, slow down, speed up, etc. Its irritating, definitely wastes gasoline, and seems to serve no other purpose than be cheap and trendy compared to some proper interchanges.  :banghead:

My current pet peeve is Washington SR 539: four roundabouts in 3.7 miles.  That and a creepy anti-abortion shrine means I have used I-5 or 542 + 9 for my travels to Canada for several years now.
Title: Re: Crash prone 'modern roundabouts'
Post by: kphoger on October 16, 2023, 02:25:18 PM

Other countries do crazy things with roundabouts and don't seem to have nearly as much trouble.

Do we know this for sure?

A question I've long wondered.  I haven't seen much, if any, data given in here for roundabouts outside the US.
Title: Re: Crash prone 'modern roundabouts'
Post by: monty on October 16, 2023, 08:33:10 PM
I’ve driven a couple thousand kilometers in Ireland where roundabouts are frequent. Driving on the (traditional American) “wrong” side of the road with a manual transmission requires a lot of focus. Multi lane roundabouts are common even on freeways. I’ll just opine that drivers in Ireland were better than those in the US. They seemed to have a lot more patience even when I was in error. Dublin is a busy city but driving there still was a bit easier due just being around good drivers. My cabbie in Dublin and I had a good discussion on this topic.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on October 16, 2023, 09:01:01 PM
I’ve driven a couple thousand kilometers in Ireland where roundabouts are frequent. Driving on the (traditional American) “wrong” side of the road with a manual transmission requires a lot of focus. Multi lane roundabouts are common even on freeways. I’ll just opine that drivers in Ireland were better than those in the US. They seemed to have a lot more patience even when I was in error. Dublin is a busy city but driving there still was a bit easier due just being around good drivers. My cabbie in Dublin and I had a good discussion on this topic.
Ireland:  Where both manners and curse words are king.
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 26, 2023, 10:14:31 AM
On December 12th, Caltrans had a ribbon cutting ceremony celebrating the completion of the State Route 184 Roundabout Project that was aimed to improve traffic safety.  Later that day Jose Guadalupe De La Paz was killed after his car struck the State Routes 223 and 184 roundabout at high speed flying airborne into a gas station pillar, cutting his vehicle in half.  The grim irony.

Quote
Caltrans' celebrated the completion of their State Route 184 Roundabout Project that aims to improve traffic safety
https://www.turnto23.com/news/in-your-neighborhood/arvin-lamont/changes-are-coming-for-drivers-in-lamont

Ribbon cutting that morning, fatal crash that night at new Weedpatch traffic roundabout
https://www.kget.com/news/local-news/ribbon-cutting-that-morning-fatal-crash-that-night-at-new-weedpatch-traffic-roundabout/
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on December 26, 2023, 10:27:36 AM
I don't see the grim irony when someone hits the center of the roundabout at high speed, which would be more indicative of reckless/inattentive driving than a problem with the roundabout itself.  The driver could also have blown through a red light and hit another vehicle, possibly causing additional deaths.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 26, 2023, 10:40:00 AM
I don't see the grim irony when someone hits the center of the roundabout at high speed, which would be more indicative of reckless/inattentive driving than a problem with the roundabout itself.  The driver could also have blown through a red light and hit another vehicle, possibly causing additional deaths.
Statistics is, of course, a long lost wizardry....
Title: Re: Crash prone 'modern roundabouts'
Post by: tradephoric on December 26, 2023, 10:51:12 AM
I don't see the grim irony when someone hits the center of the roundabout at high speed, which would be more indicative of reckless/inattentive driving than a problem with the roundabout itself.  The driver could also have blown through a red light and hit another vehicle, possibly causing additional deaths.

Ironic situations according to Alanis Morissette:
A 98 year old man who won the lottery and died the next day...
A death row pardon two minutes too late...
A "No Smoking" sign on your cigarette break...
A ribbon cutting at a roundabout and a fatal crash that same day...

Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 26, 2023, 09:57:54 PM
I don't see the grim irony when someone hits the center of the roundabout at high speed, which would be more indicative of reckless/inattentive driving than a problem with the roundabout itself.  The driver could also have blown through a red light and hit another vehicle, possibly causing additional deaths.

Could have been a medical emergency too. In either case, why should they pay with their life?
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 27, 2023, 02:40:09 AM
I don't see the grim irony when someone hits the center of the roundabout at high speed, which would be more indicative of reckless/inattentive driving than a problem with the roundabout itself.  The driver could also have blown through a red light and hit another vehicle, possibly causing additional deaths.

Could have been a medical emergency too. In either case, why should they pay with their life?
Frankly speaking, roundabout isn't the only scenario where loosing control at high speed can be fatal.
The goal of design is to minimize consequences of such mistakes - but individual accident isn't very meaningful without proper statistics.
One can certainly flirt with baessian approach and start making conclusions. But I have to agree with@tradephoric - it's ironic that first fatal crash is logged immediately after safety improvements are completed. Hopefully next one is decades away
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on December 27, 2023, 08:48:05 AM
I don't see the grim irony when someone hits the center of the roundabout at high speed, which would be more indicative of reckless/inattentive driving than a problem with the roundabout itself.  The driver could also have blown through a red light and hit another vehicle, possibly causing additional deaths.

Could have been a medical emergency too. In either case, why should they pay with their life?
Medical emergency?  So, they're racing to the hospital?  I still don't see how that's the roundabout's fault.  Ambulance drivers also certainly don't throw all sense out the window when their sirens and lights are on.

Or, if you're saying he had some sort of medical issue while driving, again, if the roundabout wasn't there doesn't mean that he would have survived.
Title: Re: Crash prone 'modern roundabouts'
Post by: jakeroot on December 27, 2023, 10:10:05 PM
Or, if you're saying he had some sort of medical issue while driving, again, if the roundabout wasn't there doesn't mean that he would have survived.

Totally, that's why I'm all for being cautious of obstacles near high-speed roadways, as they can all cause serious injury or death. Like roundabouts.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on December 27, 2023, 10:17:01 PM
Or, if you're saying he had some sort of medical issue while driving, again, if the roundabout wasn't there doesn't mean that he would have survived.

Totally, that's why I'm all for being cautious of obstacles near high-speed roadways, as they can all cause serious injury or death. Like roundabouts.
That's exactly why high speed roads have a lot of engineering features to avoid bad outcomes - such as rumble strips, guardrails, medians, jersey barriers and what not.
Maybe we need to hire an engineer to design roundabouts properly? Looks like none are left on DOTs payroll...
Title: Re: Crash prone 'modern roundabouts'
Post by: jeffandnicole on December 27, 2023, 10:57:50 PM
I don't see the grim irony when someone hits the center of the roundabout at high speed, which would be more indicative of reckless/inattentive driving than a problem with the roundabout itself.  The driver could also have blown through a red light and hit another vehicle, possibly causing additional deaths.

Could have been a medical emergency too. In either case, why should they pay with their life?
Frankly speaking, roundabout isn't the only scenario where loosing control at high speed can be fatal.
The goal of design is to minimize consequences of such mistakes - but individual accident isn't very meaningful without proper statistics.
One can certainly flirt with baessian approach and start making conclusions. But I have to agree with@tradephoric - it's ironic that first fatal crash is logged immediately after safety improvements are completed. Hopefully next one is decades away

Maybe more ironic was per the article, safety improvements had been completed since the summer.  They just held a ribbon cutting ceremony that very day for no other reason than that's what politicians do.
Title: Re: Crash prone 'modern roundabouts'
Post by: MASTERNC on January 02, 2024, 12:49:36 PM
CalTRANS has a video on its new "turbo roundabout".  On one hand, I can see the issue with lane changes in the roundabouts (which I have witnessed personally, whether inadvertent or intentional).  On the other, seems some of these movements require a 90-degree turn across roundabout traffic.

Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 02, 2024, 01:53:46 PM
CalTRANS has a video on its new "turbo roundabout".  On one hand, I can see the issue with lane changes in the roundabouts (which I have witnessed personally, whether inadvertent or intentional).  On the other, seems some of these movements require a 90-degree turn across roundabout traffic.

This is a pretty standard 3-lane piece of shitty engineering. And good thing there is no snow so they can have those curbstones in the middle of the road. May sheer off some tires...
They say trucks are accounted for, but I have hard time thinking of a truck turning into an inner lane  with that radius.
Title: Re: Crash prone 'modern roundabouts'
Post by: Rothman on January 02, 2024, 02:02:08 PM
CalTRANS has a video on its new "turbo roundabout".  On one hand, I can see the issue with lane changes in the roundabouts (which I have witnessed personally, whether inadvertent or intentional).  On the other, seems some of these movements require a 90-degree turn across roundabout traffic.

This is a pretty standard 3-lane piece of shitty engineering. And good thing there is no snow so they can have those curbstones in the middle of the road. May sheer off some tires...
They say trucks are accounted for, but I have hard time thinking of a truck turning into an inner lane  with that radius.
Should have an apron.
Title: Re: Crash prone 'modern roundabouts'
Post by: kalvado on January 02, 2024, 02:19:53 PM
CalTRANS has a video on its new "turbo roundabout".  On one hand, I can see the issue with lane changes in the roundabouts (which I have witnessed personally, whether inadvertent or intentional).  On the other, seems some of these movements require a 90-degree turn across roundabout traffic.

This is a pretty standard 3-lane piece of shitty engineering. And good thing there is no snow so they can have those curbstones in the middle of the road. May sheer off some tires...
They say trucks are accounted for, but I have hard time thinking of a truck turning into an inner lane  with that radius.
Should have an apron.
There is an apron in the video. But just imagine a heavy 18-wheeler crawling across 3 lanes of traffic and mounting on an apron during the rush hour... Extra points for a tire blown on a curbstone while doing so.