Crash prone 'modern roundabouts'

Started by tradephoric, May 18, 2015, 02:51:37 PM

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Zeffy

Two lanes should be the maximum for any circular intersection. Three lanes is just too much.
Life would be boring if we didn't take an offramp every once in a while

A weird combination of a weather geek, roadgeek, car enthusiast and furry mixed with many anxiety related disorders


jakeroot

Quote from: cl94 on December 22, 2015, 02:36:10 PM
Quote from: Rothman on December 22, 2015, 11:54:32 AM
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.
Quote from: 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.

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).

tradephoric

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

Jovet

Quote from: 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. 
I agree.  I think they're just inviting trouble!

Same for multi-lane four-way stops. Those drive me UP THE WALL!
Joseph
[Jovet]

Quillz

So, during my research, I came across this proposed roundabout design for the UK:



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.

cl94

Quote from: Quillz on January 23, 2016, 11:53:09 PM
So, during my research, I came across this proposed roundabout design for the UK:



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".
Please note: All posts represent my personal opinions and do not represent those of my employer or any of its partner agencies.

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Quillz

Quote from: cl94 on January 24, 2016, 12:10:55 AM
Quote from: Quillz on January 23, 2016, 11:53:09 PM
So, during my research, I came across this proposed roundabout design for the UK:



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.

jakeroot

Quote from: Quillz on January 24, 2016, 12:12:49 AM
Quote from: cl94 on January 24, 2016, 12:10:55 AM
Quote from: 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.

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.

Quillz

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.

roadfro

Quote from: cl94 on January 24, 2016, 12:10:55 AM
Quote from: Quillz on January 23, 2016, 11:53:09 PM
So, during my research, I came across this proposed roundabout design for the UK:



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.)
Roadfro - AARoads Pacific Southwest moderator since 2010, Nevada roadgeek since 1983.

english si

Quote from: Quillz on January 23, 2016, 11:53:09 PM
So, during my research, I came across this proposed roundabout design for the UK:

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.

Kacie Jane

Quote from: jakeroot on January 24, 2016, 12:36:50 AM
Quote from: Quillz on January 24, 2016, 12:12:49 AM
Quote from: cl94 on January 24, 2016, 12:10:55 AM
Quote from: 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.

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.

jakeroot

Quote from: Kacie Jane on January 24, 2016, 01:21:38 PM
Quote from: jakeroot on January 24, 2016, 12:36:50 AM
Quote from: Quillz on January 24, 2016, 12:12:49 AM
Quote from: cl94 on January 24, 2016, 12:10:55 AM
Quote from: 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.

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).

Quillz

I don't know what is so mind boggling. The only roundabouts I've ever personally driven on have been single laned.

tradephoric

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:

QuoteThere 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.   

jeffandnicole

Quote from: 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.

Then try driving a 2 or 3 lane roundabout.

PurdueBill

Quote from: 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:

QuoteThere 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.

Rothman

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.
Please note: All comments here represent my own personal opinion and do not reflect the official position(s) of NYSDOT.

Quillz

Quote from: jeffandnicole on January 25, 2016, 12:41:39 PM
Quote from: 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.

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.

roadfro

Quote from: 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.

You stay in your same lane, the one directly ahead of you. You're not supposed to change lanes in a roundabout.
Roadfro - AARoads Pacific Southwest moderator since 2010, Nevada roadgeek since 1983.

tradephoric

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.

QuoteHomer 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

https://www.youtube.com/watch?v=cF43x2AvhjE

Brian556

QuoteSame 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.


tradephoric

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). 

jeffandnicole

Quote from: 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). 


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.


tradephoric

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.



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