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Author Topic: Crash prone 'modern roundabouts'  (Read 234496 times)

cpzilliacus

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Re: Crash prone 'modern roundabouts'
« Reply #25 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 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.
« Last Edit: May 25, 2015, 05:02:06 PM by cpzilliacus »
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Brian556

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Re: Crash prone 'modern roundabouts'
« Reply #26 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.
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6a

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Re: Crash prone 'modern roundabouts'
« Reply #27 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.

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froggie

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Re: Crash prone 'modern roundabouts'
« Reply #28 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.

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Sykotyk

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Re: Crash prone 'modern roundabouts'
« Reply #29 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.
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roadfro

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Re: Crash prone 'modern roundabouts'
« Reply #30 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.
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tradephoric

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Re: Crash prone 'modern roundabouts'
« Reply #31 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.

« Last Edit: May 20, 2015, 11:29:40 PM by tradephoric »
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Tarkus

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Re: Crash prone 'modern roundabouts'
« Reply #32 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.
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lordsutch

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Re: Crash prone 'modern roundabouts'
« Reply #33 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.
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tradephoric

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Re: Crash prone 'modern roundabouts'
« Reply #34 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.


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
« Last Edit: May 20, 2015, 11:21:45 PM by tradephoric »
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Bickendan

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Re: Crash prone 'modern roundabouts'
« Reply #35 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?
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lordsutch

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Re: Crash prone 'modern roundabouts'
« Reply #36 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, given the weird angle of the existing intersection I suspect the multilane roundabout will be an improvement on both scores.
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Bickendan

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Re: Crash prone 'modern roundabouts'
« Reply #37 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.
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KEK Inc.

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Re: Crash prone 'modern roundabouts'
« Reply #38 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. 
« Last Edit: May 21, 2015, 02:33:22 AM by KEK Inc. »
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jakeroot

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Re: Crash prone 'modern roundabouts'
« Reply #39 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.
« Last Edit: May 21, 2015, 02:49:51 AM by jakeroot »
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tradephoric

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Re: Crash prone 'modern roundabouts'
« Reply #40 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".
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jeffandnicole

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Re: Crash prone 'modern roundabouts'
« Reply #41 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.
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tradephoric

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Re: Crash prone 'modern roundabouts'
« Reply #42 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
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english si

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Re: Crash prone 'modern roundabouts'
« Reply #43 on: May 21, 2015, 02:34:38 PM »

This 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.
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jeffandnicole

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Re: Crash prone 'modern roundabouts'
« Reply #44 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.
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Brandon

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Re: Crash prone 'modern roundabouts'
« Reply #45 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.
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tradephoric

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Re: Crash prone 'modern roundabouts'
« Reply #46 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
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jakeroot

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Re: Crash prone 'modern roundabouts'
« Reply #47 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.
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Re: Crash prone 'modern roundabouts'
« Reply #48 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: 

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triplemultiplex

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Re: Crash prone 'modern roundabouts'
« Reply #49 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.
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