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Author Topic: Crash prone 'modern roundabouts'  (Read 276976 times)

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Re: Crash prone 'modern roundabouts'
« Reply #75 on: May 27, 2015, 05:32:36 PM »

I'd rather have more safe accidents then less deadly accidents.
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"more safe" is "less deadly".

I think you meant that you'd rather have more, but safer, accidents than fewer, but deadlier, accidents.
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colinstu

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Re: Crash prone 'modern roundabouts'
« Reply #76 on: May 27, 2015, 05:35:24 PM »

Yup that's what I mean. Phrasing. Figure it out. :P
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tradephoric

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Re: Crash prone 'modern roundabouts'
« Reply #77 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. 
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Re: Crash prone 'modern roundabouts'
« Reply #78 on: May 27, 2015, 07:49:36 PM »

Excerpts from an article discussing New Berlin interchange roundabouts (http://www.newberlinnow.com/news/56607067.html):

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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.

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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?
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Re: Crash prone 'modern roundabouts'
« Reply #79 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.
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DaBigE

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Re: Crash prone 'modern roundabouts'
« Reply #80 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, Madison.com 2014 News Story. 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.
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tradephoric

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Re: Crash prone 'modern roundabouts'
« Reply #81 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. 
« Last Edit: May 28, 2015, 11:55:45 AM by tradephoric »
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DaBigE

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Re: Crash prone 'modern roundabouts'
« Reply #82 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.
« Last Edit: May 28, 2015, 12:09:57 PM by DaBigE »
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tradephoric

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Re: Crash prone 'modern roundabouts'
« Reply #83 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.
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Re: Crash prone 'modern roundabouts'
« Reply #84 on: May 28, 2015, 09:14:50 PM »

A 5-leg roundabout in Valparaiso had 98 crashes in 2014.



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Re: Crash prone 'modern roundabouts'
« Reply #85 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:



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).
« Last Edit: May 29, 2015, 11:42:29 AM by tradephoric »
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Re: Crash prone 'modern roundabouts'
« Reply #86 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). 

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Re: Crash prone 'modern roundabouts'
« Reply #87 on: May 29, 2015, 05:23:31 PM »

PARCLO B4
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Re: Crash prone 'modern roundabouts'
« Reply #88 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
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tradephoric

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Re: Crash prone 'modern roundabouts'
« Reply #89 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
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Re: Crash prone 'modern roundabouts'
« Reply #90 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"?
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Re: Crash prone 'modern roundabouts'
« Reply #91 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.
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Re: Crash prone 'modern roundabouts'
« Reply #92 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.
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Re: Crash prone 'modern roundabouts'
« Reply #93 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/
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Re: Crash prone 'modern roundabouts'
« Reply #94 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/
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Re: Crash prone 'modern roundabouts'
« Reply #95 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.
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Re: Crash prone 'modern roundabouts'
« Reply #96 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
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Re: Crash prone 'modern roundabouts'
« Reply #97 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.
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jakeroot

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Re: Crash prone 'modern roundabouts'
« Reply #98 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.
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Re: Crash prone 'modern roundabouts'
« Reply #99 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). 



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
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