Crash prone 'modern roundabouts'

[kphoger]

Maybe Carmel could have spent a few hundred thousand to retime their traffic lights as opposed to spending a few hundred million to construct all those roundabouts - and after all those roundabouts drivers still experience delays as they have to slow down at every roundabout they approach.  Conversely, you could cruise 40 miles hitting 124 consecutive green lights and barely tap your brakes.

Yeah good point. All Carmel needs is 180-foot ROW for all their roads, and a diminishing population. Problems solved!

Thanks for posting that.  After logging out last time, I was still wondering how the signal timing in suburban Detroit related to the roundabouts in Carmel.

[billpa]

Maybe Carmel could have spent a few hundred thousand to retime their traffic lights as opposed to spending a few hundred million to construct all those roundabouts - and after all those roundabouts drivers still experience delays as they have to slow down at every roundabout they approach.  Conversely, you could cruise 40 miles hitting 124 consecutive green lights and barely tap your brakes.

Yeah good point. All Carmel needs is 180-foot ROW for all their roads, and a diminishing population. Problems solved!

Very well put. I like getting several green lights in a row as much as the next guy but it's not the kind of environment I'd want to live near, let alone be a pedestrian in.
Obviously with all those greens 'someone' is getting a red. When that one car waiting on a side street 'does' get his green it'll mean everyone on the 40 mile 'green light freeway' will have to come to a full stop and have their 250-green-light-series broken up.

SM-T230NU

[kalvado]

Maybe Carmel could have spent a few hundred thousand to retime their traffic lights as opposed to spending a few hundred million to construct all those roundabouts - and after all those roundabouts drivers still experience delays as they have to slow down at every roundabout they approach.  Conversely, you could cruise 40 miles hitting 124 consecutive green lights and barely tap your brakes.

Yeah good point. All Carmel needs is 180-foot ROW for all their roads, and a diminishing population. Problems solved!

Very well put. I like getting several green lights in a row as much as the next guy but it's not the kind of environment I'd want to live near, let alone be a pedestrian in.
Obviously with all those greens 'someone' is getting a red. When that one car waiting on a side street 'does' get his green it'll mean everyone on the 40 mile 'green light freeway' will have to come to a full stop and have their 250-green-light-series broken up.

SM-T230NU

And that is exactly how this does NOT work. No surprise people support roundabouts if that is the general level of understanding things...

[kphoger]

Maybe Carmel could have spent a few hundred thousand to retime their traffic lights as opposed to spending a few hundred million to construct all those roundabouts - and after all those roundabouts drivers still experience delays as they have to slow down at every roundabout they approach.  Conversely, you could cruise 40 miles hitting 124 consecutive green lights and barely tap your brakes.

Yeah good point. All Carmel needs is 180-foot ROW for all their roads, and a diminishing population. Problems solved!

Very well put. I like getting several green lights in a row as much as the next guy but it's not the kind of environment I'd want to live near, let alone be a pedestrian in.
Obviously with all those greens 'someone' is getting a red. When that one car waiting on a side street 'does' get his green it'll mean everyone on the 40 mile 'green light freeway' will have to come to a full stop and have their 250-green-light-series broken up.

SM-T230NU

And that is exactly how this does NOT work. No surprise people support roundabouts if that is the general level of understanding things...

That doesn't make Carmel=Detroit.

[tradephoric]

Obviously with all those greens 'someone' is getting a red. When that one car waiting on a side street 'does' get his green it'll mean everyone on the 40 mile 'green light freeway' will have to come to a full stop and have their 250-green-light-series broken up.

Here's an aerial model of how the lights in downtown Portland are timed.  The turning movements are purposely left out to highlight how there is "daylight"  between the platoons.  Sure, there are always turning vehicles filling up this daylight but those movements are much more sporadic than the main platoon.  You seem to be picturing every time a side-street turns green that all the main street traffic has to stop.  That's not really how it works.  A well timed network of lights would theoretically stop only the sporadic vehicles that made a turn at an upstream signal or those who pulled out of a midblock drive.

https://www.youtube.com/watch?v=7jGWdCknurM&t=60s

By the way the closely spaced traffic signals in downtown Portland are timed for 13 mph and help regulate the speed of traffic downtown.  Roundabouts would never be as effective at regulating the speed of traffic in downtown as the traffic signals are.  But you have people mindlessly believing that roundabouts are safer than the traffic signals they replace without question.  Let's hope James Brainard doesn't runs for the mayor of Portland. 

[billpa]

Obviously with all those greens 'someone' is getting a red. When that one car waiting on a side street 'does' get his green it'll mean everyone on the 40 mile 'green light freeway' will have to come to a full stop and have their 250-green-light-series broken up.

Here's an aerial model of how the lights in downtown Portland are timed.  The turning movements are purposely left out to highlight how there is "daylight"  between the platoons.  Sure, there are always turning vehicles filling up this daylight but those movements are much more sporadic than the main platoon.  You seem to be picturing every time a side-street turns green that all the main street traffic has to stop.  That's not really how it works.  A well timed network of lights would theoretically stop only the sporadic vehicles that made a turn at an upstream signal or those who pulled out of a midblock drive.

https://www.youtube.com/watch?v=7jGWdCknurM&t=60s

By the way the closely spaced traffic signals in downtown Portland are timed for 13 mph and help regulate the speed of traffic downtown.  Roundabouts would never be as effective at regulating the speed of traffic in downtown as the traffic signals are.  But you have people mindlessly believing that roundabouts are safer than the traffic signals they replace without question.  Let's hope James Brainard doesn't runs for the mayor of Portland.

No offense, but when it comes to roundabouts I don't find you to be an honest broker.
I'm not saying you have zero data or have made no good points but you're SO anti-roundabout that I'm not sure this thread is rational.

HTC6525LVW

[tradephoric]

No offense, but when it comes to roundabouts I don't find you to be an honest broker.
I'm not saying you have zero data or have made no good points but you're SO anti-roundabout that I'm not sure this thread is rational.

A December 2017 Caltrans pamphlet promotes the safety of roundabouts by citing decades old IIHS safety statistics.  Next to those impressive numbers is a picture of a complex roundabout that has a propensity to increasing total crashes AND injury crashes.  I'm citing published roundabout research from 2017 - not generic safety statistics from two decades ago.   The definition of propaganda is information, especially of a biased or misleading nature, used to promote or publicize a particular political cause or point of view.   You may think that definition describes my posts.  But isn't it misleading for Caltrans to cite decades old IIHS safety statistics when much more recent roundabout research exists that refute it? 


http://www.dot.ca.gov/milemarker/docs/articles/2017/Q4/MM-2017-Q4-roundabout.pdf

[jakeroot]

isn't it misleading for Caltrans to cite decades old IIHS safety statistics when much more recent roundabout research exists that refute it?

Research exists in this thread, and a few PowerPoints presented at various research conferences (and accompanying PDFs), but there still hasn't been any major country-wide research done on the topic. Just regional stuff that not all traffic engineers might be privy to.

Just a few months ago, I spoke to a local traffic engineer in my area (city of Fife, WA) about flashing yellow arrows. The city recently changed a 4-way intersection with stop signs for the minor road into a fully-protected intersection with protected-only phasing for the left turns. I asked him why they went from minimum control to complete control, and he stated that their consultant suggested it. I asked about protected/permissive phasing, and he stated that left turns against more than one lane should have protected phasing. I informed him of the numerous permissive left turns against three+ lanes of traffic in Federal Way, a city literally due north about three miles, and he told me that he'd never heard of such a thing. I told him that Federal Way had seen a decrease in collisions/injuries, but he told me that he was limited in his options due to this "consultant" evidently holding more power than him.

My point is that engineers sometimes live in these bubbles, where they genuinely aren't privy to work outside of their area. They eventually hear of certain things like roundabouts or Michigan Lefts, many years after they were first implemented, but the follow-up studies sometimes don't reach them. And from what I can tell, rarely do the laziest engineers ever go out and try to see "what's up"...they just keep on doing what they've always been doing, with only occasional innovation. Think of all the protected left turns that Caltrans continues to install. That's so painfully 70s that I'm stunned that they even consider roundabouts, which are effectively the opposite of signals with fully protected phasing.

[jeffandnicole]

isn't it misleading for Caltrans to cite decades old IIHS safety statistics when much more recent roundabout research exists that refute it?

Research exists in this thread, and a few PowerPoints presented at various research conferences (and accompanying PDFs), but there still hasn't been any major country-wide research done on the topic. Just regional stuff that not all traffic engineers might be privy to.

Just a few months ago, I spoke to a local traffic engineer in my area (city of Fife, WA) about flashing yellow arrows. The city recently changed a 4-way intersection with stop signs for the minor road into a fully-protected intersection with protected-only phasing for the left turns. I asked him why they went from minimum control to complete control, and he stated that their consultant suggested it. I asked about protected/permissive phasing, and he stated that left turns against more than one lane should have protected phasing. I informed him of the numerous permissive left turns against three+ lanes of traffic in Federal Way, a city literally due north about three miles, and he told me that he'd never heard of such a thing. I told him that Federal Way had seen a decrease in collisions/injuries, but he told me that he was limited in his options due to this "consultant" evidently holding more power than him.

My point is that engineers sometimes live in these bubbles, where they genuinely aren't privy to work outside of their area. They eventually hear of certain things like roundabouts or Michigan Lefts, many years after they were first implemented, but the follow-up studies sometimes don't reach them. And from what I can tell, rarely do the laziest engineers ever go out and try to see "what's up"...they just keep on doing what they've always been doing, with only occasional innovation. Think of all the protected left turns that Caltrans continues to install. That's so painfully 70s that I'm stunned that they even consider roundabouts, which are effectively the opposite of signals with fully protected phasing.

Frustratingly true.

The same can be said within Transportation organizations as well.  One engineering department can be for a certain intersection arrangement; another can be against it.  Or one administration be for something; another against it.  You wind up with a single road designed at different times with different arrangements at different intersections, because different teams were involved (and which don't actually talk with each other).

Actually, the same can be said of consultants.  I recall one NJDOT public meeting I went to where they were planning on 'widening' a local road at an intersection.  The current road is one lane per direction with no turn lanes at the intersection.  The widening will consist of adding a single lane left turn channel on each approach.  I asked why they don't widen the main roadway to 2 lanes per direction as well, which is badly needed.  He accused me of being a speed racer who only wanted fast roads.

The same consultant, I learned, was redesigning a local roadway in Virginia. It was going to be 3 or 4 lanes per direction.  I guess they're all speed racers down there if they're getting such a wide roadway.  Shame I didn't know that at the time of the NJDOT meeting.

[kalvado]

isn't it misleading for Caltrans to cite decades old IIHS safety statistics when much more recent roundabout research exists that refute it?

Research exists in this thread, and a few PowerPoints presented at various research conferences (and accompanying PDFs), but there still hasn't been any major country-wide research done on the topic. Just regional stuff that not all traffic engineers might be privy to.

Just a few months ago, I spoke to a local traffic engineer in my area (city of Fife, WA) about flashing yellow arrows. The city recently changed a 4-way intersection with stop signs for the minor road into a fully-protected intersection with protected-only phasing for the left turns. I asked him why they went from minimum control to complete control, and he stated that their consultant suggested it. I asked about protected/permissive phasing, and he stated that left turns against more than one lane should have protected phasing. I informed him of the numerous permissive left turns against three+ lanes of traffic in Federal Way, a city literally due north about three miles, and he told me that he'd never heard of such a thing. I told him that Federal Way had seen a decrease in collisions/injuries, but he told me that he was limited in his options due to this "consultant" evidently holding more power than him.

My point is that engineers sometimes live in these bubbles, where they genuinely aren't privy to work outside of their area. They eventually hear of certain things like roundabouts or Michigan Lefts, many years after they were first implemented, but the follow-up studies sometimes don't reach them. And from what I can tell, rarely do the laziest engineers ever go out and try to see "what's up"...they just keep on doing what they've always been doing, with only occasional innovation. Think of all the protected left turns that Caltrans continues to install. That's so painfully 70s that I'm stunned that they even consider roundabouts, which are effectively the opposite of signals with fully protected phasing.

You know, sometimes I really wonder if there is a hidden helicopter parking lot near the local DOT building. If they were driving same roads I do, they would definitely notice problems which apparently go unnoticed for decades....

[tradephoric]

^Apart from the RV blowing through the middle of that Worthington Minnesota roundabout, there has been two other pretty major events at the roundabout over the past couple weeks.

Tanker hauling cream overturns in Worthington roundabout

http://www.dglobe.com/news/accidents/4356792-tanker-hauling-cream-overturns-worthington-roundabout


These little piggies almost didn't make it to market when a Minn. hog truck rolled

http://www.agweek.com/news/4350581-these-little-piggies-almost-didnt-make-it-market-when-minn-hog-truck-rolled

Cream trucks rolling over, hogs running around the highway, some RV driver thinking they are Bo Duke... these roundabouts really give the good people of Worthington Minnesota something to talk about!

Another vehicle vaulted over the Worthington roundabout on Sunday.  The driver sustained non-life threatening injuries.  This comes a month after an RV was videotaped launching over the roundabout in early November.

Minivan vaults over roundabout Sunday
https://www.dglobe.com/news/accidents/4375814-minivan-vaults-over-roundabout-sunday

[tradephoric]

Walker roundabouts creating more problems than solutions
http://www.wbrz.com/news/walker-roundabouts-creating-more-problems-than-solutions/

"It's been a tremendous headache for us," said Captain John Sharp. "We're a small police department. We have enough officers to cover routine wrecks, but if we have to take an officer out of the call rotation and put him out here directing traffic, then that leaves us short-handed."

DOTD put in the roundabouts in August to try and fix the traffic congestion of a growing city, but Walker PD says it's simply not working.

Captain Sharp says they average about 3 accidents a week on these things.  "This is a state highway. It's a state project. The city of Walker has no input. We have nothing to do with it," said Sharp.

[tradephoric]

Carmel mayor says roundabouts contributing to fewer injury accidents

http://fox59.com/2017/12/21/carmel-mayor-says-roundabouts-contributing-to-fewer-injury-accidents/

The mayor of Carmel cites the reduction of citywide injury crash rates over the past 21 years as prove that roundabouts have made Carmel safer.  He argues that not much has changed in Carmel that would attribute to the reduction in injury crashes...

"The only big change is our roundabouts, because Indianapolis is about the same. Fishers is about the same. The other surrounding communities have stayed about the same over the last 20 years,"  Brainard said.

But a lot has changed since 1996.   

#1.  Nationwide there has been a 35% reduction in the fatal crash rate from 1996 to today.  Advancements in vehicle safety over the past 21 years has changed.

#2.  The population of Carmel was 31,808 in 1996 and 92,475 today.  With the population nearly tripling over the past 21 years, Carmel has turned less "rural" and more "urban".  Basically the old adage "there are safety in numbers" applies here. 



#3.  Two of the major roadways in Carmel (Meridian Street and Keystone Pkwy) were converted from surface streets to grade separated freeways over the past 21 years.  Freeways have lower fatality rates than surface streets, and when two heavily traveled surface streets in your city are converted to grade separated freeways, you should expect a reduction in injury crashes. 

Nowhere in this article does the Mayor mention that there have been 5 fatalities at Carmel roundabouts over the past decade.  Compare that to no known fatal crashes at Carmel traffic signals in the same time period (even as traffic signals in Carmel outnumbered the roundabouts a decade ago).  If traffic signals are so much more dangerous than roundabouts, why has there been an infinitely higher number of fatal crashes at Carmel's roundabouts?  The mayor rightfully says...

"That's what it's really about, building our roadways so they are as safe as possible,"  he said. "We know that humans are always going to error. We are all going to make mistakes. We all do it. The question is can we design our roadways in a safer manner so when that mistake is made it results in a fender bender, not a trip to the hospital or a fatality."

It's a mistake when a driver blows through the middle of a roundabout.  Consider the fact that there have been 3 fatalities at the Westfield and 96th roundabout over the past decade - in each case the vehicle blew through the roundabout and struck a retaining wall in the central island.  The mayor acknowledges that we all make mistakes, but the roads should be designed so those mistakes results in a fender bender and not a trip to the hospital or morgue in a gurney.  If he really believed that then the retaining wall on the 96th and Westfield roundabout would have been torn down already (instead they doubled down and added some memorial "art" to the central island of the roundabout...the next driver to blow through the roundabout will potentially get speared to death).

[MNHighwayMan]

yet another long post

[tradephoric]

It is beating a dead horse when roundabout proponents keep saying how safe roundabouts are.  Jim Brainard's posts would be about 3 words long - "roundabouts are safe" - and he has been mindlessly repeating that mantra for the past 21 years.  Using generic citywide injury crash data (that doesn't directly relate to intersection crashes) isn't a compelling argument.  But don't bother Jim with facts, he is meditating...

Roundabouts are safe...
Roundabouts are safe...
Roundabouts are safe...

[AlexandriaVA]

I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

That said, the data are abundantly clear about the utility of roundabouts, particularly in lower-density areas like Indiana etc.

[silverback1065]

this is the worst thread on aaroads

[Rothman]

No, it isn't the worst thread.  Not by a long shot.

That said, his assertion that increases in population means safer streets made me laugh

I am with the Mayor on this one.

[kalvado]

I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

That said, the data are abundantly clear about the utility of roundabouts, particularly in lower-density areas like Indiana etc.

Then why are you wasting your time on this (or any other) forum to begin with?

[kalvado]

That said, his assertion that increases in population means safer streets made me laugh

Can be zillion secondary effects.
More traffic means change in road design.  Tighter control, replacement of two-way stop with traffic lights, lightning, etc.
Reduced speeds.
Change in travel patterns.
Increased police presence and enforcement
Change in demographics (somehow leading to reduced drunk driving or better seatbelt use, for example)

Not sure how that would work for an area going from rural to suburban to urban in a same location, but difference between rural and urban accident rate is very real.

[AlexandriaVA]

I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

That said, the data are abundantly clear about the utility of roundabouts, particularly in lower-density areas like Indiana etc.

Then why are you wasting your time on this (or any other) forum to begin with?

Because I still enjoy the discussions. But I don't know why some people seem so inclined, almost to the point of pathology, to oppose the roundabouts. I think some people are just scared of change.

[kalvado]

I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

That said, the data are abundantly clear about the utility of roundabouts, particularly in lower-density areas like Indiana etc.

Then why are you wasting your time on this (or any other) forum to begin with?

Because I still enjoy the discussions. But I don't know why some people seem so inclined, almost to the point of pathology, to oppose the roundabouts. I think some people are just scared of change.

How can you enjoy if you yourself said that

I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

You probably better off trying to ron for some office instead of wasting time on discussions with jockeys

[AlexandriaVA]

I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

That said, the data are abundantly clear about the utility of roundabouts, particularly in lower-density areas like Indiana etc.

Then why are you wasting your time on this (or any other) forum to begin with?

Because I still enjoy the discussions. But I don't know why some people seem so inclined, almost to the point of pathology, to oppose the roundabouts. I think some people are just scared of change.

How can you enjoy if you yourself said that
quote author=AlexandriaVA link=topic=15546.msg2285872#msg2285872 date=1513952086]
I'm far more interested in the views of an elected public official who has to deal with the consequences of his policy decisions than some random internet jockey.

You probably better off trying to ron for some office instead of wasting time on discussions with jockeys
[/quote]

I don't religiously oppose roundabouts unlike some on here. Moreover, the data is pretty clear they work. If you parse anything long enough, you can find the results you want.

My point is that the mayor, as an elected official, has to balance the data, public opinion,internal politics, etc. There's more to road design than just engineering, after all. Given all that, the fact that he endorses them is more illuminating to me than some long-winded manifesto.

[kalvado]

My point is that the mayor, as an elected official, has to balance the data, public opinion,internal politics, etc. There's more to road design than just engineering, after all. Given all that, the fact that he endorses them is more illuminating to me than some long-winded manifesto.

Of course, that is a big part of entire picture. But given so many stupid things are done in the name of winning the next election, political support means pretty much nothing in technical terms.

. Moreover, the data is pretty clear they work.

It is not, but whatever - see above.

[AlexandriaVA]

My point is that the mayor, as an elected official, has to balance the data, public opinion,internal politics, etc. There's more to road design than just engineering, after all. Given all that, the fact that he endorses them is more illuminating to me than some long-winded manifesto.

Of course, that is a big part of entire picture. But given so many stupid things are done in the name of winning the next election, political support means pretty much nothing in technical terms.

. Moreover, the data is pretty clear they work.

It is not, but whatever - see above.

Then play Sim City. In the real world, political context is a major influence, always has been and always will be.