Crash prone 'modern roundabouts'

[kalvado]

The uptick in accidents at these roundabouts is proving that drivers aren't driving properly through them. The issue whether the agencies responsible want to have their heads in the sand, or accept that some drivers simply bugger up the system. Both the timid and the brave.

I'm afraid you are putting things up side down: roundabouts are, by design, using controlled aggression to allow traffic to use smaller gaps and so increase throughput. So somewhat aggressive driving should be encouraged, not suppressed - otherwise capacity of roundabout would be reduced below meaningful threshold.

[Sykotyk]

The uptick in accidents at these roundabouts is proving that drivers aren't driving properly through them. The issue whether the agencies responsible want to have their heads in the sand, or accept that some drivers simply bugger up the system. Both the timid and the brave.

I'm afraid you are putting things up side down: roundabouts are, by design, using controlled aggression to allow traffic to use smaller gaps and so increase throughput. So somewhat aggressive driving should be encouraged, not suppressed - otherwise capacity of roundabout would be reduced below meaningful threshold.

I see roundabout as a traffic calming device. Sitting at a light or stop sign can be aggravating. Allowing a vehicle to proceed after only slowing down when there's inconsistent or little side traffic is the positive result of a roundabout.

Putting one in a heavily used intersection does what you say and what I had been pointing to for a while, that it takes away safety in exchange for the 'me first' attitude of drivers trying to be the next one into the circle or to avoid having to come to a full stop.

You've made my point.

[english si]

So somewhat aggressive driving should be encouraged, not suppressed - otherwise capacity of roundabout would be reduced below meaningful threshold.

Assertive, not aggressive. There's a big difference.

"the 'me first' attitude of drivers trying to be the next one into the circle or to avoid having to come to a full stop." - oddly we don't see that here: perhaps a cultural difference? But even in France (without the Germanic respect for rules, or the British love of queuing), Spain, etc they do it fine.

[kalvado]

So somewhat aggressive driving should be encouraged, not suppressed - otherwise capacity of roundabout would be reduced below meaningful threshold.

Assertive, not aggressive. There's a big difference.

Well, big question is what criteria should be used, and what kind of traffic that roundabout gets.
You want to be an assertive person who is going to wait until a gap big enough to keep 2 second intervals both before and after your car? Remember to take a tent and a grill, you will be camping there for a while.
I still think that being able to put a razor between two bumpers is not safe enough? I am with you... But I am evolving....

Once again, problem is with understanding the role of roundabouts. As I say, it's a problem- specific medication, Insulin should not be prescribed for every pneumonia.  Over here roundabouts are positioned as a replacement for heaviest load intersections. You plainly have no choice once you have a roundabout with 20-30k daily traffic count - you need to lower you threshold.

[english si]

You want to be an assertive person who is going to wait until a gap big enough to keep 2 second intervals both before and after your car? Remember to take a tent and a grill, you will be camping there for a while.

No I don't. Aggressive is "Poop, poop, out my way!", jumping onto a roundabout and expecting else everyone to make it safe, whereas assertive is "Hello, I'm here!". You don't need to slot into a 4 second gap as
1) The car in front of you won't hit you if you are a couple of yards behind it - you simply move slowly enough to make the gap bigger.
2) The car behind you can also slow down to make the gap bigger
3) Cars are turning off anyway and roundabouts are small enough that the person you are slotting in behind will have left the roundabout not long after you joined (unless turning right).

Over here roundabouts are positioned as a replacement for heaviest load intersections.

I take it you've never been to the UK! We use them for far busier junctions than the the US. The 3 trunk road dual carriageway arms at the Black Cat Roundabout in Bedfordshire (the 4th arm is the old route of one of the trunk roads) have volumes of 53267 (north), 27784 (west) and 24977 (south), giving total figures of over 53k using that roundabout! OK, that's an outlying excessive case, but 20k-30k is very much par for the course.

You plainly have no choice once you have a roundabout with 20-30k daily traffic count - you need to lower you threshold.

My nearest roundabout (a mini roundabout) has that sort of volume (and is far from a busy one for Blighty).* The gaps seem to be fine. I can't be bothered to time them, but they are about every two seconds. People just navigate the junction slowly, but assertively.


*3 arms with conservative (count would increase if the points were closer to the roundabout) 2014 figures of 14164, 16818 and 9610, divided by 2 (as each car through the roundabout would be counted twice) = 20296. There's roundabouts in my town with figures of 41899, 31830 (three arms) and 31610, and even they are rather ordinary for the UK. The 3-arm one between the A355 and A40 just north of M40 J2 has more than 43k vehicles per day and never seems to have any problems.

[tradephoric]

English_si, are any of those UK roundabouts that you referenced signalized?  I have heard that at some of the bigger UK roundabouts have signals that are dark for most of the day but cycle during peak times. 

[english si]

The Black Cat was recently, but wasn't when the traffic figures were taken in 2014. I gather the signalisation merely extended the queues.

None of the others are signalised.

[kalvado]

No I don't. Aggressive is "Poop, poop, out my way!", jumping onto a roundabout and expecting else everyone to make it safe, whereas assertive is "Hello, I'm here!". You don't need to slot into a 4 second gap as
1) The car in front of you won't hit you if you are a couple of yards behind it - you simply move slowly enough to make the gap bigger.
2) The car behind you can also slow down to make the gap bigger
3) Cars are turning off anyway and roundabouts are small enough that the person you are slotting in behind will have left the roundabout not long after you joined (unless turning right).

OK, looks like we have a different definition of "aggressive".
I wouldn't call "Poop, poop, out my way!" aggressive, I would call that "idiot" at best (I am not sure if moderators would tolerate full comment).
Your assumption that the car behind you may slow down a bit _is_ the definition of "somewhat aggressive" for me, as "yield" assumes other driver should not have to touch brake pedal at all.
With that in mind, looks like we're on the same page here, but you're a more seasoned roundabouter...

[tradephoric]

Top 5 Crash-Prone Intersections In Oakland County Include 2 Roundabouts
http://detroit.cbslocal.com/2016/01/05/top-5-dangerous-intersections-in-oakland-county-include-2-roundabouts/

With 116 total crashes, the roundabout at M-5 & Pontiac Trail was the highest crash prone intersection in Oakland County in 2015.  The roundabout was constructed in 2011 and Oakland County drivers have had 4 years to get use to the operation of the roundabout.  Here is 10 years of crash data for this intersection based on SEMCOG crash data:



Accidents at M-5 & Pontiac Trail jumped from 54 in 2014 to 116 in 2015.  Haggerty Road which runs parallel to M-5 was reconstructed in 2015 and the roundabout was part of the detour route.  This could help explain the large spike in accidents.

[Sykotyk]

The data should also be based on a percentage of total average daily vehicles that use that intersection. If a big development was built nearby or the roads around it were improved to make it a more preferable route, could see an uptick in traffic and then a corresponding uptick in accidents.

Detour traffic could easily explain the spike for 2015, though, as you have people unfamiliar with a road trying to follow orange blazers back to their original route or destination leaving them less observant at a roundabout.

[kphoger]

It also makes me wonder about the spike between 2011 and 2012.

I remember when I-57 northbound was closed in southern Illinois one, and all traffic was routed through the uncontrolled town square in Benton. Utter misery. A modern roundabout in that case would have helped not one bit; what was needed was traffic cops directing traffic.

[tradephoric]

The data should also be based on a percentage of total average daily vehicles that use that intersection.

I previously listed crash rates for 3x2 and 2x2 multi-lane roundabouts I could find data on.  It's important to note that many agencies consider a crash rate above 2.0 MEV as "critical"  that warrants further investigation. 



The average crash rate for these multi-lane roundabouts was 3.69 MEV.  As a comparison, the average crash rate of Minnesota's high speed signalized intersections was just 0.8 MEV.  The multi-lane roundabouts have a crash rate over 4X higher than Minnesota's high speed signalized intersections.
 

http://www.dot.state.mn.us/trafficeng/publ/fundamentals/MnDOT_Safety_Handbook_FINAL.pdf

[tradephoric]

I think I'll leave this here ...

http://www.mlive.com/news/ann-arbor/index.ssf/2016/04/road_commission_improves_state.html#incart_river_home

Number of crashes at State and Ellsworth roundabout drops following initial spike

It's getting better.  The idiots are beginning to learn how to navigate it.  And it's not nearly as bad as someone who does not live here makes it out to be.  I have to deal with it every day, and have yet to see an accident.  I don't think anyone has died there, either.

It's like bragging your favorite baseball team lost 9-2 when the day before they got shut out 14-0.   YAY... good job... only 114 crashes this year. 

[tradephoric]

Find out which Livingston County intersections rank highest for number of injuries
http://www.livingstondaily.com/story/news/local/community/livingston-county/2015/11/23/livingston-countys-worst-intersections-crashes/75170418/

Instead of ranking intersections by total crashes, the above article ranks them by the number of injuries.  Lee Road roundabout (pictured below) was No. 2 on the list with 23 injury crashes and 264 total crashes over the past 5 years.  There are literally hundreds of intersections in Livingston County.  If roundabouts are so much safer, how is it that the Lee Road roundabout had the 2nd highest number of injury crashes over the past 5 years? 

[kalvado]

Find out which Livingston County intersections rank highest for number of injuries
http://www.livingstondaily.com/story/news/local/community/livingston-county/2015/11/23/livingston-countys-worst-intersections-crashes/75170418/

You know, it makes some sense to include exact location with a post like this one... here you go:
https://www.google.com/maps/place/Lee+Rd,+Brighton,+MI+48116/@42.5061734,-83.7604905,1154m/data=!3m1!1e3!4m2!3m1!1s0x88234fcef7c20dfb:0x53f7c294fdc4524a

I really wonder if traffic volumes warranted such a complex interchange set to begin with...

[Tarkus]

The engineer who designed that Lee Road dual-roundabout has to be some sort of sadist.  Honestly, it makes the Swindon Magic Roundabout look sensible. 

[tradephoric]

Look at how worn the pavement markings are in the below aerial compared to when Lee Road roundabout was freshly painted.  A lot of the safety improvements done to these crash prone roundabouts involve pavement marking tweaks.  All this research is done regarding pavement markings at roundabouts but then we allow the pavement markings to fade to nothing.

[kalvado]

Look at how worn the pavement markings are in the below aerial compared to when Lee Road roundabout was freshly painted.  A lot of the safety improvements done to these crash prone roundabouts involve pavement marking tweaks.  All this research is done regarding pavement markings at roundabouts but then we allow the pavement markings to fade to nothing.

One thing I heard about roundabouts is that they are oh, so much cheaper to maintain, unlike  traffic lights which consume power and need bulbs change!
Given new LED traffic controls, sounds like we have a $100 solution for an $1 problem..

As for the intersection in question, with total of 5 roundabouts... I only wonder how much was the kickback.

[Tarkus]

One thing I heard about roundabouts is that they are oh, so much cheaper to maintain, unlike  traffic lights which consume power and need bulbs change!
Given new LED traffic controls, sounds like we have a $100 solution for an $1 problem..

The whole "maintenance cost" claim with signals vs. roundabouts was a load of hooey even before LEDs became commonplace in signals.  The usually cited savings figure is $5000/year, which means that for a $250,000 signal vs. a $2,500,000 roundabout, you're looking at 450 years before one reaches the break even point, and I doubt the roundabout is going to have a design life of 450 years.

[jakeroot]

One thing I heard about roundabouts is that they are oh, so much cheaper to maintain, unlike  traffic lights which consume power and need bulbs change!
Given new LED traffic controls, sounds like we have a $100 solution for an $1 problem..

The whole "maintenance cost" claim with signals vs. roundabouts was a load of hooey even before LEDs became commonplace in signals.  The usually cited savings figure is $5000/year, which means that for a $250,000 signal vs. a $2,500,000 roundabout, you're looking at 450 years before one reaches the break even point, and I doubt the roundabout is going to have a design life of 450 years.

The price of intersection modification is highly subjective. Not all roundabouts cost $2.5mil, and not all signals cost $250k.

The best example might be freeway/service road interchanges. The cost of widening a bridge over a freeway costs a lot more than installing roundabouts at the ramp termini.

FWIW, WSDOT cites an average annual signal maintenance cost of $8k: http://goo.gl/q3Q6Kh

[tradephoric]

DOT eyes crash-heavy roundabout on Eau Claire's south side

http://www.leadertelegram.com/News/Front-Page/2016/03/30/Crash-heavy-roundabout-eyed.html

The article states there has been 26 crashes at the roundabout between 2011 and 2015.  That equates to about 5 crashes a year.  That to me is not "crash heavy" especially considering the amount of traffic volume US 53 carries.  This is a multi-lane roundabout but it's a simpler 2x1 variety.  I guess they plan on adding rumble strips before the roundabout to slow traffic down and also mound the center island to make it more visible to approaching motorists.

[tradephoric]

A 2016 report by the UMD National Transportation Center analyzed the safety of Arizona roundabouts.   Of the double-lane roundabouts analyzed there was a 68% increase in the average rate of accidents per million vehicles.  Also, there was an 8% decrease in the average rate of injuries per year per million vehicles.  The report came to the following conclusion:

In conclusion, single-lane roundabouts improved the safety of intersections. However, double-lane roundabouts reduced the safety of intersections. A decision needs to be made as to either remove double-lane roundabouts or find solutions on how to make these roundabouts safe, such as making geometric improvements or educating the public on how to use them.

http://ntc.umd.edu/sites/default/files/documents/Publications/NTC2015-SU-R-3_Mamlouk.pdf

Many multi-lane roundabouts in this thread (specifically 2x2 and higher) have seen large increases in total accidents with a lackluster reduction in injury accidents.  This 2016 study of multi-lane roundabouts in Arizona match this performance.

[JMAN_WiS&S]

DOT eyes crash-heavy roundabout on Eau Claire's south side

http://www.leadertelegram.com/News/Front-Page/2016/03/30/Crash-heavy-roundabout-eyed.html

The article states there has been 26 crashes at the roundabout between 2011 and 2015.  That equates to about 5 crashes a year.  That to me is not "crash heavy" especially considering the amount of traffic volume US 53 carries.  This is a multi-lane roundabout but it's a simpler 2x1 variety.  I guess they plan on adding rumble strips before the roundabout to slow traffic down and also mound the center island to make it more visible to approaching motorists.

I mentioned this a few pages back and it seems people ignored it as nobody replied and continued other replies.

[tradephoric]

DOT eyes crash-heavy roundabout on Eau Claire's south side

http://www.leadertelegram.com/News/Front-Page/2016/03/30/Crash-heavy-roundabout-eyed.html

The article states there has been 26 crashes at the roundabout between 2011 and 2015.  That equates to about 5 crashes a year.  That to me is not "crash heavy" especially considering the amount of traffic volume US 53 carries.  This is a multi-lane roundabout but it's a simpler 2x1 variety.  I guess they plan on adding rumble strips before the roundabout to slow traffic down and also mound the center island to make it more visible to approaching motorists.

I mentioned this a few pages back and it seems people ignored it as nobody replied and continued other replies.

I vaguely remember someone bringing up the US 53 Eau Claire roundabout but I didn't see your earlier post until now.  My point is I don't believe there is much of a crash problem at that Eau Claire roundabout (despite what the headline of the article leads you to believe).  I've been criticized for pointing out high crash rate roundabouts throughout this thread but I'll be the first to defend a roundabout that is working well.  The multi-lane roundabout in Eau Claire averages about 5 crashes a year.  That doesn't sound bad at all.

[JMAN_WiS&S]

DOT eyes crash-heavy roundabout on Eau Claire's south side

http://www.leadertelegram.com/News/Front-Page/2016/03/30/Crash-heavy-roundabout-eyed.html

The article states there has been 26 crashes at the roundabout between 2011 and 2015.  That equates to about 5 crashes a year.  That to me is not "crash heavy" especially considering the amount of traffic volume US 53 carries.  This is a multi-lane roundabout but it's a simpler 2x1 variety.  I guess they plan on adding rumble strips before the roundabout to slow traffic down and also mound the center island to make it more visible to approaching motorists.

I mentioned this a few pages back and it seems people ignored it as nobody replied and continued other replies.

I vaguely remember someone bringing up the US 53 Eau Claire roundabout but I didn't see your earlier post until now.  My point is I don't believe there is much of a crash problem at that Eau Claire roundabout (despite what the headline of the article leads you to believe).  I've been criticized for pointing out high crash rate roundabouts throughout this thread but I'll be the first to defend a roundabout that is working well.  The multi-lane roundabout in Eau Claire averages about 5 crashes a year.  That doesn't sound bad at all.

The only issue is people going into it too quickly going SB. I'm quite suprised eau claire only has a couple roundabouts and not more, as it seems they are popular elsewhere in the state.