Crash prone 'modern roundabouts'

[lordsutch]

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.

[jakeroot]

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).

[tradephoric]

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:

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.

[silverback1065]

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

[jakeroot]

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

My favorite quote(s):

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.

[cl94]

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

My favorite quote(s):

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.

[tradephoric]

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. 

[tradephoric]

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.   

https://www.youtube.com/watch?v=lchIO9YPLgE

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

[jakeroot]

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.

[Rothman]

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).

[cl94]

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.

[Rothman]

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.

[tradephoric]

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. 

[silverback1065]

http://www.wthr.com/story/30254415/round-and-round-carmel-man-sets-out-to-set-roundabout-driving-record

[tradephoric]

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.

[tradephoric]

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://www.wral.com/traffic/story/11369528/

[jakeroot]

What are the traffic flow numbers along Hillsborough Street?

[tradephoric]

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. 


www.ncdot.gov/travel/statemapping/trafficvolumemaps/default.html

[tradephoric]

In addition to the increase in total crashes, the Hillsborough Street roundabout had a 29% increase in injury crashes:


https://connect.ncdot.gov/resources/safety/Safety%20Evaluation%20Projects/Roundabout%20Presentation%20with%20Notes.pdf

[jakeroot]

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?

[tradephoric]

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

[tradephoric]

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://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://www.islandpacket.com/news/local/traffic/article33716778.html

[jakeroot]

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.

[silverback1065]

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.

[tradephoric]

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:









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).