Crash prone 'modern roundabouts'

[kalvado]

No one is saying that roundabouts are a universal solution, but you seem to be saying that all roundabouts are intrinsically evil.

I am saying that thoughtless design of anything is evil.  Most, if not all, roundabouts I see around do fall into that category.

Not really thoughtless design. Most (all?) are designed to MUTCD standards. Never mind that no comprehensive studies have ever come out that steadfastly show multi-lane roundabouts to be not-as-great as we previously thought. There have been seminars, small studies, presentations, etc that have presented the idea of multi-lane roundabouts having more than their fair share of collisions, but there's never been anything thorough before.

I understand that the FHWA based a lot of current roundabout rhetoric off old, small studies. But trying to refute those studies with an equally small study doesn't prove anything (except that small studies can often be engineered to reflect the desired outcome of the author).

As far as I remember earlier posts in this thread, you're now infected with my skepticism... 
Yes, that is pretty much the point - building without looking back.  Road standards, by their nature, are not set in stone or asphalt, they have to adapt. Quite often you can say you're on an old road just by driving it.  And "we just follow MUTCD" is not a good excuse for not learning on past experience.

[DaBigE]

No one is saying that roundabouts are a universal solution, but you seem to be saying that all roundabouts are intrinsically evil.

I am saying that thoughtless design of anything is evil.  Most, if not all, roundabouts I see around do fall into that category.

Not really thoughtless design. Most (all?) are designed to MUTCD standards. Never mind that no comprehensive studies have ever come out that steadfastly show multi-lane roundabouts to be not-as-great as we previously thought. There have been seminars, small studies, presentations, etc that have presented the idea of multi-lane roundabouts having more than their fair share of collisions, but there's never been anything thorough before.

I understand that the FHWA based a lot of current roundabout rhetoric off old, small studies. But trying to refute those studies with an equally small study doesn't prove anything (except that small studies can often be engineered to reflect the desired outcome of the author).

FIFY. The MUTCD doesn't govern roundabout design. The MUTCD only provides suggested marking and signing layouts for roundabouts.

[jakeroot]

No one is saying that roundabouts are a universal solution, but you seem to be saying that all roundabouts are intrinsically evil.

I am saying that thoughtless design of anything is evil.  Most, if not all, roundabouts I see around do fall into that category.

Not really thoughtless design. Most (all?) are designed to MUTCD standards. Never mind that no comprehensive studies have ever come out that steadfastly show multi-lane roundabouts to be not-as-great as we previously thought. There have been seminars, small studies, presentations, etc that have presented the idea of multi-lane roundabouts having more than their fair share of collisions, but there's never been anything thorough before.

I understand that the FHWA based a lot of current roundabout rhetoric off old, small studies. But trying to refute those studies with an equally small study doesn't prove anything (except that small studies can often be engineered to reflect the desired outcome of the author).

As far as I remember earlier posts in this thread, you're now infected with my skepticism... 
Yes, that is pretty much the point - building without looking back.  Road standards, by their nature, are not set in stone or asphalt, they have to adapt. Quite often you can say you're on an old road just by driving it.  And "we just follow MUTCD" is not a good excuse for not learning on past experience.

I am skeptical of large roundabouts, yes. I'm just not as worried as Trade is. A lot of the small studies that I've seen seem to show that, while collisions are on the rise, every other aspect of junction safety is on the decline (not true at all roundabouts, though).

The MUTCD doesn't govern roundabout design. The MUTCD only provides suggested marking and signing layouts for roundabouts.

Good to know. I thought the MUTCD was more thorough. Do individual states provide roundabout engineering standards?

[tradephoric]

Take a look at this route https://www.google.com/maps/dir/39.9232311,-86.1121404/40.0648746,-86.1262864/@39.9712591,-86.0688241,12.25z going from 96th and Keystone Parkway northward through Carmel and on through Westfield.    Almost every interchange along this route has roundabout intersections, but the through traffic passes under or over the roundabouts.   This is intelligent usage of roundabouts.

The most intelligent roundabout is one where drivers don't have to drive through it?  We are starting to agree!  Although I'll point out that the roundabout at 116th & Keystone Parkway has a horrendous crash rate.  According to the Carmel Police Department Annual Reports, the 116th and Keystone roundabout averaged 64.3 crashes a year from 2011-2014 and had an AADT of 20,463.  That equates to a crash rate of 8.7 MEV which is over 4x higher than 2.0 MEV (what many agencies consider a "˜critical' crash rate that warrants further investigation).  In addition, the city added a traffic signal at the 136th Street and Keystone Parkway roundabout to address the traffic snarls that would occur at that roundabout during heavy rushes.   



I don't see how roundabouts with horrendous crash rates and ones that require traffic signals to function properly could be considered "intelligent" .  Not to mention, the through traffic along Keystone Parkway totally bypasses the roundabouts.  Imagine the cluster that would occur if Keystone Parkway wasn't grade separated.  Roundabouts wouldn't have even been an option.

[cjw2001]

The ramp meters at 136 and keystone only operate a few minutes a day on demand as triggered by traffic sensors, during the sudden rush brought on by 5000+ students arriving or leaving the state's largest high school all at the same time.   The vast majority of the day it operates as a normal roundabout.   That's an intelligent solution that only invokes the ramp meters as needed.

I'll take the traffic throughput  of the roundabout at 116th and Keystone any day over the stop light it replaced.  Yes there may be more minor fender benders as compared to a stoplight (it's hard to run into other people when stuck in gridlock) but traffic flows well without backups.  There is no way we would want to go back to the previous intersection.  I don't define the success of the intersection based on the number of fender benders, I define it based on the smooth traffic flow that we have today.

[tradephoric]

Carmel does a far better job on their roundabout design than most places.   Having lived here in the pre roundabout era and the post roundabout era I can say that traffic is far far better today than in the past.   There are another 30 roundabouts on the way  and very much looking forward to it.  http://carmellink.com/

Much of the improved traffic flow is a result of grade-separating the city's heaviest traveled routes.  You can't credit roundabouts for the improved flow along Keystone Parkway and Meridian Street.  Of the heavily traveled surface-streets that haven't been grade-separated, most are void of roundabouts.  You just don't encounter a roundabout every intersection as you drive down Rangeline Road, 96th Street or 116th Street.  But that's all about to change.  If you look at the link provided by cjw2001, 18 of the 30 upcoming roundabouts are being constructed along these major routes.  While Carmel has been conservative in their roundabout design in the past, they are finally jumping in head first and building more complex roundabouts along the heaviest traveled roadways.

CJW2001, did they finish constructing the 96th and Gray Road roundabout?  To the best of my knowledge, this is the first roundabout in Carmel that has three circulating lanes of traffic. Roundabouts with triple circulating lanes are the type of roundabouts that win awards... specifically most crashes in the state awards.  I'm sure you would be proud if Carmel could win such a prestigious award!   

[cjw2001]

96th and Gray will be summer 2017

[tradephoric]

96th and Gray will be summer 2017

Thanks for the info.  Since Carmel will be constructing their first triple-lane roundabout this year it might be wise to consider how triple-lane roundabouts have performed in other parts of the country.  Over the past ten years, Wisconsin has constructed about 20 triple-lane roundabouts and not surprisingly many have exceedingly high crash rates.  The international roundabout conference is taking place in Green Bay this year so we might hear more about these "triple-laners" .  But to the best of my knowledge, all but one district in Wisconsin has placed a moratorium on designing triple-lane roundabouts moving forward.  It's telling when an agency with the most experience building triple-lane roundabouts places a moratorium on them.    Wisconsin has spent ten years tested the limitations of roundabouts and they seemingly concluded that "triple laners"  are too much. 

[kphoger]

I wonder if a three-lane turbo roundabout would see lower crash rates.

[tradephoric]

Car shoots through roundabout and over bluff at Bachman Tunnel
http://wdef.com/2017/04/21/car-shoots-roundabout-bluff-bachman-tunnel/

Early this morning a driver failed to make a turn at the Bluffman Tunnel roundabout in Chattanooga and plunged 50 feet down a cliff.  The passenger is in critical condition.   Looking at historical imagery and streetview, this isn't the first time a driver hit the guardrail on the other side of the roundabout.  Exhibit A in the upcoming lawsuit:

[jakeroot]

^^ There doesn't seem to be much (if any) warning of the impending roundabout. A blinking overhead W2-6 may be in order.

The only sign seems to be this one before the tunnel, which is only half correct:



*also, Bluffman tunnel?

[kphoger]

What does this have to do with the intersection being a roundabout?

[jeffandnicole]

^^ There doesn't seem to be much (if any) warning of the impending roundabout. A blinking overhead W2-6 may be in order.

The only sign seems to be this one before the tunnel, which is only half correct:



*also, Bluffman tunnel?

There's also a large overhead 'Yield ahead at end of tunnel' with blinking lights sign prior to these signs. Not to mention what appears to be a slow speed tunnel and a pretty good Yield sign at the end of the tunnel.

What the issue probably was is some kid who decided to speed way too fast they the tunnel and couldn't slow down in time.

Sometimes, you just have to chalk things up to driver stupidity.

[jakeroot]

What does this have to do with the intersection being a roundabout?

Actually that's a good point. The intersection is still T-shaped. Roundabout or not, going over that bluff is inevitable if one is going too quickly.

[english si]

What does this have to do with the intersection being a roundabout?

I'd argue that it is somewhat relevant as, ignoring jeffandnicole's comments about the reality, it is part of the "engineers are often terrible at providing decent information to drivers" and "drivers are often stupid" problems that seems to be sustaining this thread.

[kalvado]

What does this have to do with the intersection being a roundabout?

I'd argue that it is somewhat relevant as, ignoring jeffandnicole's comments about the reality, it is part of the "engineers are often terrible at providing decent information to drivers" and "drivers are often stupid" problems that seems to be sustaining this thread.

I would add "intentionally obscuring the view, as required per roundabout concept"

[jeffandnicole]

Car shoots through roundabout and over bluff at Bachman Tunnel
http://wdef.com/2017/04/21/car-shoots-roundabout-bluff-bachman-tunnel/

Early this morning a driver failed to make a turn at the Bluffman Tunnel roundabout in Chattanooga and plunged 50 feet down a cliff.  The passenger is in critical condition.   Looking at historical imagery and streetview, this isn't the first time a driver hit the guardrail on the other side of the roundabout.  Exhibit A in the upcoming lawsuit:

Since Trade has a tendency to provide only half the story...here's a possible reason those guardrail dents are there: http://wdef.com/2016/07/20/cascades-motel-robbery-suspect-crashes-chattanooga-chase/  Apparently, leading police on a high speed chase and hitting another car is now a fault of a roundabout.

[MNHighwayMan]

Apparently, leading police on a high speed chase and hitting another car is now a fault of a roundabout.

Idiots will always be idiots, there's no helping that.

[kalvado]

Car shoots through roundabout and over bluff at Bachman Tunnel
http://wdef.com/2017/04/21/car-shoots-roundabout-bluff-bachman-tunnel/

Early this morning a driver failed to make a turn at the Bluffman Tunnel roundabout in Chattanooga and plunged 50 feet down a cliff.  The passenger is in critical condition.   Looking at historical imagery and streetview, this isn't the first time a driver hit the guardrail on the other side of the roundabout.  Exhibit A in the upcoming lawsuit:

Since Trade has a tendency to provide only half the story...here's a possible reason those guardrail dents are there: http://wdef.com/2016/07/20/cascades-motel-robbery-suspect-crashes-chattanooga-chase/  Apparently, leading police on a high speed chase and hitting another car is now a fault of a roundabout.

From the look of those guardrails, looks like they have daily police chases in the area.

[tradephoric]

Maybe it was an epic multi-year police chase .  The roundabout crash is relevant in that it dispels the whole premise of why roundabouts are safer.  Just read what the Insurance Institute for Highway Safety website says...



A driver blowing through a roundabout and flying 50 feet over a cliff is evidence that roundabouts don't force drivers to slow down.  With their logic I could make the argument that traffic signals are safer than roundabouts because red lights force drivers to stop - at roundabouts you merely slow down.   If they can't even get the premise right, why would anyone believe their dubious claim that roundabouts reduce fatal crashes by 90%? 

[Brian556]

The accidents at the Bachman Tunnel roundabout that are being described here would happen whether the roundabout was there or not.

They are happening because there is a T-junction/sharp turn after the tunnel, and people are stupid and don't read signs.

That roundabout wasn't always there. I'd be willing to bet the accidents were happening long before the roundabout was installed

[kalvado]

The accidents at the Bachman Tunnel roundabout that are being described here would happen whether the roundabout was there or not.

They are happening because there is a T-junction/sharp turn after the tunnel, and people are stupid and don't read signs.

That roundabout wasn't always there. I'd be willing to bet the accidents were happening long before the roundabout was installed

I would say that money ($1M or so I suspect) were just lost here. Roundabout was apparently built as a way to eliminate accidents - but equally apparently fails.
I have hard time finding location on the map, but from the look of posted mapshots I suspect that there is no power readily available at the location - i.e. no traffic lights or flashing warnings.
Maybe it would make more sense to spend money either running power line, or installing solar array + batteries to power some more aggressive warning signals?
And if that is more or less the case - this is exactly what I am complaining about - thoughtless building of roundabouts under flawed assumptions of "it solves all problems"

UPD: taking power available portion back. Apparently power is available, so illuminated signs probably just don't result in attractive enough contracts...

[lordsutch]

A driver blowing through a roundabout and flying 50 feet over a cliff is evidence that roundabouts don't force drivers to slow down.  With their logic I could make the argument that traffic signals are safer than roundabouts because red lights force drivers to stop - at roundabouts you merely slow down.   If they can't even get the premise right, why would anyone believe their dubious claim that roundabouts reduce fatal crashes by 90%? 

Now you're just being silly. For example, road diets are designed to slow drivers down because drivers generally drive slower in narrower lanes (9' to 11' lanes rather than 12'+), with closer curbs, etc. Yet there's no physical impediment to using a dieted road as a drag strip, so I guess road diets don't actually work.

[kalvado]

A driver blowing through a roundabout and flying 50 feet over a cliff is evidence that roundabouts don't force drivers to slow down.  With their logic I could make the argument that traffic signals are safer than roundabouts because red lights force drivers to stop - at roundabouts you merely slow down.   If they can't even get the premise right, why would anyone believe their dubious claim that roundabouts reduce fatal crashes by 90%? 

Now you're just being silly. For example, road diets are designed to slow drivers down because drivers generally drive slower in narrower lanes (9' to 11' lanes rather than 12'+), with closer curbs, etc. Yet there's no physical impediment to using a dieted road as a drag strip, so I guess road diets don't actually work.

As I said multiple times, the root cause problem is quality of engineering personnel.
Roads are designed for average Joe. Maybe for 80 years old aunt Mary and her husband who is still driving. For those college kids who have more hormones than brains. And roads MUST be designed with them in mind.
If it was about designing NASCAR track, requirements may be different. But there is a clear sign of accident pattern observable in that area - even on google maps.
That is design problem.
That is engineering problem.
In private company such performance failure would be a reason for firing, plain and simple.
 

[jeffandnicole]

A driver blowing through a roundabout and flying 50 feet over a cliff is evidence that roundabouts don't force drivers to slow down.  With their logic I could make the argument that traffic signals are safer than roundabouts because red lights force drivers to stop - at roundabouts you merely slow down.   If they can't even get the premise right, why would anyone believe their dubious claim that roundabouts reduce fatal crashes by 90%? 

Now you're just being silly. For example, road diets are designed to slow drivers down because drivers generally drive slower in narrower lanes (9' to 11' lanes rather than 12'+), with closer curbs, etc. Yet there's no physical impediment to using a dieted road as a drag strip, so I guess road diets don't actually work.

As I said multiple times, the root cause problem is quality of engineering personnel.
Roads are designed for average Joe. Maybe for 80 years old aunt Mary and her husband who is still driving. For those college kids who have more hormones than brains. And roads MUST be designed with them in mind.
If it was about designing NASCAR track, requirements may be different. But there is a clear sign of accident pattern observable in that area - even on google maps.
That is design problem.
That is engineering problem.
In private company such performance failure would be a reason for firing, plain and simple.
 

How did those accidents happen with the guardrail?

If there was 3 separate accidents, and 3 different causes, what was the design problem?

What if an accident was caused by a deer running thru the roundabout?  Or someone blew a tire?  The guardrail SAVED their lives.  Simply because a guardrail was hit doesn't mean there's a design problem.  On the contrary, the guardrail was designed properly.

By your and Trade's logic, we should never have guardrails anywhere ever, because that reveals a design problem when hit.