Crash prone 'modern roundabouts'

[hm insulators]

A few days ago, I was exercising my shoulder at the physical therapist's office (a word of advice: never dislocate a shoulder and/or tear a rotator cuff) and the TV was tuned to a station that showed a diverging-diamond intersection either already in place at some freeway/surface-street interchange or about to be installed (the sound was off) and it showed a video of how a diverging diamond intersection works. I watched it and said, "I definitely like that better than these stupid roundabouts that having been cropping up!"

[jeffandnicole]

ANother small non-injury accident on a roundabout: truck with hot tar rolled over on one of the roundabots in Malta - the road in question has a chain of 7.
Previously those circles made to the top of Trade's list of bad guys, and one of them made it to the list of 20 most dangerous intersections in the area as published by local insurance company. But that all is a small price to pay for your safety!
http://cbs6albany.com/news/local/traffic-alert-tanker-rollover-at-exit-12

While that does suck, we can find rollover truck accidents that have occurred everywhere.  Why the insistence of nitpicking when they happen on a roundabout?  I've yet to see anyone say we need to eliminate all curves because of a single truck rollover.

[jakeroot]

Tradephoric: dumbell/roundabout interchange or diverging diamond interchange?

[jeffandnicole]

Tradephoric: dumbell/roundabout interchange or diverging diamond interchange?

Parclo B.  Everytime.  Regardless of the circumstances.

[jakeroot]

Tradephoric: dumbell/roundabout interchange or diverging diamond interchange?

Parclo B.  Everytime.  Regardless of the circumstances.

Oh, right. I've heard they're great for signal progression. Not so much for safety. But who cares about safety?

[kalvado]

ANother small non-injury accident on a roundabout: truck with hot tar rolled over on one of the roundabots in Malta - the road in question has a chain of 7.
Previously those circles made to the top of Trade's list of bad guys, and one of them made it to the list of 20 most dangerous intersections in the area as published by local insurance company. But that all is a small price to pay for your safety!
http://cbs6albany.com/news/local/traffic-alert-tanker-rollover-at-exit-12

While that does suck, we can find rollover truck accidents that have occurred everywhere.  Why the insistence of nitpicking when they happen on a roundabout?  I've yet to see anyone say we need to eliminate all curves because of a single truck rollover.

Because harsh sequential curves of roundabouts, along with design pushing trucks to uneven inner circle are very likely a contributing factor in this accident. Ideology of roundabout, when traffic never has a right of way on entry, makes maneuvering that is relatively easy for cars somewhat difficult for heavy trucks, which often struggle with proper acceleration, which is required for proper navigation of roundabouts. Wouldn't be surprised that entry at higher rate of speed is a contributing factor - but required to avoid accidents with cars sneaking by.

[tradephoric]

Tradephoric: dumbell/roundabout interchange or diverging diamond interchange?

That's like asking me to pick my favorite type of broccoli.  Both the dumbbell roundabout and DDI kill good signal progression along Happy Valley Road, making driving along Happy Valley Road less happy for drivers.

Oh, right. I've heard they [Parclo B4s] are great for signal progression. Not so much for safety. But who cares about safety?

I encountered the dangers of freeway exiting loop ramps about a year ago.  The guy infront of me exited a freeway loop ramp at about 80 mph and didn't even tap his brakes.  But the interchange in question wasn't a Parclo B4.  The fact is there are hundreds - probably thousands - of interchanges in America that include exiting loop ramps.  Even today many freeway interchanges are being designed with exiting loop ramps.  If you have a problem with the safety of exiting loop ramps on freeways, then there are a lot of different interchange designs you can focus on.

https://www.youtube.com/watch?v=2dvm7-5yMMo

[tradephoric]

While that does suck, we can find rollover truck accidents that have occurred everywhere.  Why the insistence of nitpicking when they happen on a roundabout?  I've yet to see anyone say we need to eliminate all curves because of a single truck rollover.

The Herb Gray Parkway roundabout outside Windsor, Ontario had 4 trucks rollover from April 2015 to August 2015.  That's right - 4 truck rollovers in 5 months.  What signalized intersection has seen 4 trucks rollover over a 5 month period?  There are roughly 300,000 traffic signals in America compared to about 5,000 roundabouts.  With 300,000 traffic signals to choose from, surely you can find a traffic signal that averages a rollover a month.

Apr 22, 2015:  All lanes open after another roundabout rollover at Highway 3
http://www.cbc.ca/news/canada/windsor/all-lanes-open-after-another-roundabout-rollover-at-highway-3-1.3043578

May 20, 2015:  The Star's View: Warn truckers of traffic circle tipping hazard
http://windsorstar.com/uncategorized/warn-truckers-of-traffic-circle-tipping-hazard

August 4, 2015:Transport rollover at Howard Avenue and Highway 401
http://windsorstar.com/news/transport-rollover-at-howard-avenue-and-highway-401

[jakeroot]

Tradephoric: dumbell/roundabout interchange or diverging diamond interchange?

That's like asking me to pick my favorite type of broccoli.  Both the dumbbell roundabout and DDI kill good signal progression along Happy Valley Road, making driving along Happy Valley Road less happy for drivers.

What interchange do you think would be superior? I don't think a regular diamond would be any good. Maybe a SPUI? A B4 Parclo could fit in the space, honestly.

How do roundabouts kill good signal progression? Roundabouts seem to process what's thrown at them pretty well (though I know some use metering due to the large amount of entering traffic from one direction). DDI's seem far worse to me.

Oh, right. I've heard they [Parclo B4s] are great for signal progression. Not so much for safety. But who cares about safety?

I encountered the dangers of freeway exiting loop ramps about a year ago.  The guy infront of me exited a freeway loop ramp at about 80 mph and didn't even tap his brakes.  But the interchange in question wasn't a Parclo B4.  The fact is there are hundreds - probably thousands - of interchanges in America that include exiting loop ramps.  Even today many freeway interchanges are being designed with exiting loop ramps.  If you have a problem with the safety of exiting loop ramps on freeways, then there are a lot of different interchange designs you can focus on.

I was mostly being facetious. I just remember you mentioning them being less popular with DOTs due to a perceived danger with exiting loops.

[jakeroot]

While that does suck, we can find rollover truck accidents that have occurred everywhere.  Why the insistence of nitpicking when they happen on a roundabout?  I've yet to see anyone say we need to eliminate all curves because of a single truck rollover.

The Herb Gray Parkway roundabout outside Windsor, Ontario had 4 trucks rollover from April 2015 to August 2015.  That's right - 4 truck rollovers in 5 months.

Which makes me wonder, more than anything else: why do all of our roundabouts have truck aprons? Why not just have the circulating lane (the actual circle) be two lanes wide, with a short inner curb that trucks could run over if absolutely necessary? Seems to me that the truck apron indirectly contributes to rollover crashes (certainly not helping if a truck enters faster than they should).

Some of Washington's older roundabouts have this design:

(2005) Cordata Parkway Roundabout(s), Bellingham -- photo from Reid Middleton:


(2002) Tester Road Roundabout, Monroe:

[kalvado]

Which makes me wonder, more than anything else: why do all of our roundabouts have truck aprons? Why not just have the circulating lane (the actual circle) be two lanes wide, with a short inner curb that trucks could run over if absolutely necessary? Seems to me that the truck apron indirectly contributes to rollover crashes (certainly not helping if a truck enters faster than they should).

If you ask me: there shouldn't be any extra lanes, which do not have proper entrance/exit ports associated with them for car navigation reasons. Trucks in tight turns need extra room. If you ever saw 53' navigating tight 2-lane intersection...
Now making those extra lanes flush with roadway invites traffic... So you need to have that cake and eat it too. Outcome? You're hungry and have no cake...

[jakeroot]

Which makes me wonder, more than anything else: why do all of our roundabouts have truck aprons? Why not just have the circulating lane (the actual circle) be two lanes wide, with a short inner curb that trucks could run over if absolutely necessary? Seems to me that the truck apron indirectly contributes to rollover crashes (certainly not helping if a truck enters faster than they should).

If you ask me: there shouldn't be any extra lanes, which do not have proper entrance/exit ports associated with them for car navigation reasons.

Sorry, what I meant was one lane that was roughly 20-24 feet wide. Not two marked lanes with no apron.

Not sure if that changes your response, though.



Tradephoric, have you seen this story? http://www.dailymail.co.uk/news/article-2639400/Australian-roundabouts-dangerous-world.html

[A] report...released by Austroads last week, found that the design of Australian roundabouts encouraged drivers to speed through intersections and to "˜look but not see' other motorists

Australian roundabouts are built according to a tangential design, which means that the driver has very good visibility as they approach the roundabout and is less likely to slow down, or check the roundabout closely as they approach the intersection.

European radial design left, Australian (and American) tangential design right:

[kalvado]

Which makes me wonder, more than anything else: why do all of our roundabouts have truck aprons? Why not just have the circulating lane (the actual circle) be two lanes wide, with a short inner curb that trucks could run over if absolutely necessary? Seems to me that the truck apron indirectly contributes to rollover crashes (certainly not helping if a truck enters faster than they should).

If you ask me: there shouldn't be any extra lanes, which do not have proper entrance/exit ports associated with them for car navigation reasons.

Sorry, what I meant was one lane that was roughly 20-24 feet wide. Not two marked lanes with no apron.

Not sure if that changes your response, though.

It doesn't matter if that affects my response, it does matter if it affect driver behavior  .

And what I would expect.... I go through one of roundabouts daily; I approach from the side where 1 lane splits into two: one dedicated right turn, one option lane for through traffic and left turn. Everything is marked, signed, labeled... Once or twice a week I see someone trying to continue through  by going into dedicated right lane (and frankly speaking, that means a less wavy drive).   usually they realize and yield to traffic in proper lane, but once a month I see a close call.
Now what you suggest is a similar design without pavement marks and designated lanes...  I expect this to be a non-stop close call...

One possibility would be using two-color pavement (and that is  what they do anyway) - in a level layout, not elevated apron. That may work...  if weather is fine. Rainy nights, snow - not so much.

[jakeroot]

I agree that the straighter the line, the higher the speed, chance for collision, etc. But if we designed our roundabouts with a less tangential entry (see above), maybe we'd see lower speeds? An entry with more of a right turn?

While the Dutch are heavy users of truck aprons, they use this "right turn to enter" approach at most, if not all new roundabouts:

image from Urban Design NL (Twitter):

[english si]

kill good signal progression

If anyone wants to know where tradephoric got his initial dislike of roundabouts, it is his love of good signal progression and roundabouts changing that.

Of course, if you do a Carmel, then signal progression doesn't matter as there very few signals.

[kalvado]

I agree that the straighter the line, the higher the speed, chance for collision, etc. But if we designed our roundabouts with a less tangential entry (see above), maybe we'd see lower speeds? An entry with more of a right turn?

While the Dutch are heavy users of truck aprons, they use this "right turn to enter" approach at most, if not all new roun

Well. two things: tangential approaches often include wavy patterns to begin with - although I suspect that is a result of DUI (Design Under Influence), slowing down traffic is another outcome.
As for square-in approach... I don't see that working well for more than 1 circulating lane. Remember - Trade's crusade is after the multilane ones, single lane are less of a problem generally.
And re-introducing possibility of T-bone, reducing throughput... what is the point of construction then?

[tradephoric]

Remember - Trade's crusade is after the multilane ones, single lane are less of a problem generally.

This is true.  I'm mainly focused on the multilane roundabouts that have exceedingly high crash rates.  The single-lane roundabouts I have opposed are ones with fixed objects in the central island.  For instance, the roundabout at 96th and Westfield Blvd in Carmel has been the site of multiple fatalities over the past decade.   Two people were killed in 2007 when a vehicle slammed into the retaining wall in the middle.  The same thing happened again in 2016, killing one person.  These fatalities account for a significant percentage of total roadway fatalities in Carmel over the past decade.

Of the roundabouts analyzed in the IIHS study, there were 3 fatal crashes during the before period and none during the after period.  Based on this limited data they made the claim that roundabouts reduce fatalities by 90%.  Looking back at the 96th and Westfield Blvd intersection there are no news reports of fatal crashes occurring before the roundabout was constructed.  Since the fatalities at 96th and Westfield Blvd went from 0 in the before period to 3 in the after period, maybe we can claim that roundabouts increase fatalities by 90% (same amount of fatalities cited in the 2000 IIHS study when they made their claims).

The 96th and Westfield Blvd isn't the only roundabout in Carmel that has had a fatal crash.  In August 2014, a driver was killed after losing control of their vehicle in the Pennsylvania St and 106th roundabout.  In Sept. 2014 a motorcyclist was killed after colliding with the curb on the north side of the 126th and Hazel Dell Parkway roundabout.  According to the Carmel Police Department there were 5 fatal crashes in the city from 2014-2016.  Of these 5 fatal crashes, 3 of them occurred at roundabouts.  Here are news reports of the fatal roundabout crashes:

Fishers man dies in motorcycle crash
http://fox59.com/2014/09/26/person-dead-after-motorcycle-accident-in-carmel/

Driver dead following accident in Carmel, passenger taken to hospital
http://fox59.com/2014/08/06/one-dead-in-carmel-accident-passenger-taken-to-hospital/

Carmel driver dies after crashing into roundabout's concrete barrier
http://currentincarmel.com/carmel-driver-dies-after-crashing-into-roundabouts-concrete-barrier

[tradephoric]

Worst roundabout in Britain? Multiple crashes at 'lethal' roundabout cause concern
http://www.telegraph.co.uk/news/2017/07/31/worst-roundabout-britain-multiple-crashes-lethal-roundabout/

Incredibly there were 10 crashes in a 48 hour period at a newly opened roundabout in Britain.  These are British drivers who supposedly have a lot of experience driving through roundabouts.  So why so many crashes?  Is it just bad British drivers or bad design? 

[english si]

see thread on SABRE about that roundabout: https://www.sabre-roads.org.uk/forum/viewtopic.php?f=1&t=37936

it seems that while there are many things not up to muster (too flat, signs not big enough for the speed, junction not in keeping with the road, clearly designed by home-builders rather than highways people), it's not quite as bad as the drivers are making out and their numptiness is a contributing factor to the incidents.

[jakeroot]

Odd that they would put in a roundabout where there was already grade separation. Seems like a bad idea (mostly because of driver expectation).

OSM shows where the roundabout is (Google has not yet updated their maps as of 1 Aug): https://goo.gl/NMePAs

[kalvado]

it's not quite as bad as the drivers are making out and their numptiness is a contributing factor to the incidents.

Oh, now UK drivers are not fit for roundabouts... You're making progress, my friend, soon you would acknowledge that roundabouts are too good  to be built on planet Earth!

[jakeroot]

it's not quite as bad as the drivers are making out and their numptiness is a contributing factor to the incidents.

Oh, now UK drivers are not fit for roundabouts... You're making progress, my friend, soon you would acknowledge that roundabouts are too good  to be built on planet Earth!

I'd like to see how well American drivers could handle an unsigned roundabout suddenly appearing out of nowhere on a 70 MPH freeway.

A rogue roundabout is likely to produce more collisions off the bat than a signal due to the "conform or crash" nature of the design. Not denying that.

[english si]

Oh, now UK drivers are not fit for roundabouts...

No not saying that at all - the issue isn't the existence of the roundabout, it is that poor warning of this new feature, on a road where it doesn't really belong, raised the bar of attention needed on the road far above the already-high minimum expected on UK roads, catching the less attentive out. If the signs were the right size for 70mph, if the roundabout was well lit and had stuff in the middle (even just a raised mound of earth), then none of these crashes would have happened - but at the same time, if the drivers were as attentive they ought to have been, they wouldn't have crashed as they'd have seen the small signs on the approach and would be warned - even though the maroon car had taken out the chevron signs that mark the island.

I imagine the outcome of investigation into the RTIs will be zero bad driving charges (ie that they were driving with the legally expected amount of due care and attention), but also zero insurance payout from the constructors of the roundabout as they met the required standards even though they fell way short of best practice.

AFAICS, no one was hurt, and the only reason that cars were damaged (it seems that the maroon car has a puncture, but no dents, and the blue car is stuck in the mud, with some dents) was due to the sign poles (like everything else) merely conforming to minimum standards, but not best practice. It's a lesson in why shoddy practices are bad, ie what I've been saying, rather than one in "roundabouts are dangerous and require too high a standard of driving that drivers can't cope with" that you and tradephoric are pushing as a narrative in order to push shoddy practices. Tradephoric has attacked raised areas on islands as death traps, but the lack of one here is a key factor into why people didn't see the roundabout.

[tradephoric]

Oh, now UK drivers are not fit for roundabouts.

English_si would never admit that.  British drivers are blameless and if there are a lot of crashes at a UK roundabout it must be bad design.    Of course if there are a lot of crashes at an American roundabout then it's due to those stupid, lazy, and unobservant American drivers. 

I'd argue that the main problem with US roundabouts is culture and education, but in the UK it's geometry and design if a roundabout has lots of crashes.

In the US, when the issue seems to be design, it's actually due to education reasons - assuming that American drivers are stupid, lazy and unobservant, and therefore designing poor practice to be proscribed by road markings is a recipe for disaster.

[kalvado]

Oh, now UK drivers are not fit for roundabouts...

No not saying that at all - the issue isn't the existence of the roundabout, it is that poor warning of this new feature, on a road where it doesn't really belong, raised the bar of attention needed on the road far above the already-high minimum expected on UK roads, catching the less attentive out. If the signs were the right size for 70mph, if the roundabout was well lit and had stuff in the middle (even just a raised mound of earth), then none of these crashes would have happened - but at the same time, if the drivers were as attentive they ought to have been, they wouldn't have crashed as they'd have seen the small signs on the approach and would be warned - even though the maroon car had taken out the chevron signs that mark the island.

I imagine the outcome of investigation into the RTIs will be zero bad driving charges (ie that they were driving with the legally expected amount of due care and attention), but also zero insurance payout from the constructors of the roundabout as they met the required standards even though they fell way short of best practice.

AFAICS, no one was hurt, and the only reason that cars were damaged (it seems that the maroon car has a puncture, but no dents, and the blue car is stuck in the mud, with some dents) was due to the sign poles (like everything else) merely conforming to minimum standards, but not best practice. It's a lesson in why shoddy practices are bad, ie what I've been saying, rather than one in "roundabouts are dangerous and require too high a standard of driving that drivers can't cope with" that you and tradephoric are pushing as a narrative in order to push shoddy practices. Tradephoric has attacked raised areas on islands as death traps, but the lack of one here is a key factor into why people didn't see the roundabout.

Got it, got it...
Then, good sir, would you mind explaining what you mean by the following phrase:

it's not quite as bad as the drivers are making out and their numptiness is a contributing factor to the incidents.

And just to be cristal clear about the roots of my question:

numpty, noun British informal
    A stupid or ineffectual person.

So, good sir, do I get it correct that said drivers got into the accident on said roundabout are  stupid and/or ineffectual - in other words, not really qualified for driving?