Crash prone 'modern roundabouts'

[kalvado]

Then I would rather have a T-bone, so that another driver unable to look around would leave the road.

Here's my theory:

At a traditional signal, the driver either misses you, or t-bones you. There's no "angle" crashes. At roundabouts however, assuming the drunk driver might follow the channelisation of the lane, but does not properly yield, there can be more of an angle crash. Or, they can drive straight over the channelising island, and t-bone you, just like at a signal. Or, they might miss you entirely.

Thusly, there's less of a chance of a t-bone collision at a roundabout, because it's one of three options, instead of two. A study would need to be done as to which type of crash is more common at roundabouts, however.

There is also a chance that I am turning left - and here comes angle collision. Also, if I see poorly controlled car in my  rear view mirror, I have more room to move out of impact on a regular intersection.

As for study.. If this wasn't published 5 years ago, it only means that a few (thousands) people in FHWA   DOTs  etc get their paychecks for not doing their jobs.

[jakeroot]

There is also a chance that I am turning left - and here comes angle collision.

Why would you turn left into someone?

Also, if I see poorly controlled car in my  rear view mirror, I have more room to move out of impact on a regular intersection.

I don't think there's any reasonable difference between roundabouts and signals in this regard. You're pretty much just nitpicking here.

[jeffandnicole]

...if I see poorly controlled car in my  rear view mirror, I have more room to move out of impact on a regular intersection.

Ah, yes, the "I know how I'm going to react" statement.

Good luck with that.  Seriously...if you're turning left watching for a gap in front of you, are you really looking in your rearview mirror?  Let me answer that for you: "No".

[kalvado]

There is also a chance that I am turning left - and here comes angle collision.

Why would you turn left into someone?

Also, if I see poorly controlled car in my  rear view mirror, I have more room to move out of impact on a regular intersection.

I don't think there's any reasonable difference between roundabouts and signals in this regard. You're pretty much just nitpicking here.

To make it simple: collision at an angle would occur on a regular intersection in case both vehicles aim to the same exit. I am turning left north, you also head straight north, for example.

...if I see poorly controlled car in my  rear view mirror, I have more room to move out of impact on a regular intersection.

Ah, yes, the "I know how I'm going to react" statement.

Good luck with that.  Seriously...if you're turning left watching for a gap in front of you, are you really looking in your rearview mirror?  Let me answer that for you: "No".

Of course nobody knows how they would react until they read police report on the accident.. Point rather is that you have a bit more freedom to avoid hazard in a regular intersection as opposed to curbs bth inside and outside the roundabout. It may only make things worse, after all.
But - and feel free to disagree - I would love to see statistics on a large dataset - probably there are thousands roundabouts which exist for 5+ years. I want that data published and organized by traffic volumes, number of lanes etc.
I would say that is something FHWA must do at some point, better sooner than later. And that should be fairly doable for them as well.

[cjw2001]

Having personally experienced this situation just a few weeks ago, I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.

[jeffandnicole]

There is also a chance that I am turning left - and here comes angle collision.

Why would you turn left into someone?

Also, if I see poorly controlled car in my  rear view mirror, I have more room to move out of impact on a regular intersection.

I don't think there's any reasonable difference between roundabouts and signals in this regard. You're pretty much just nitpicking here.

To make it simple: collision at an angle would occur on a regular intersection in case both vehicles aim to the same exit. I am turning left north, you also head straight north, for example.

...if I see poorly controlled car in my  rear view mirror, I have more room to move out of impact on a regular intersection.

Ah, yes, the "I know how I'm going to react" statement.

Good luck with that.  Seriously...if you're turning left watching for a gap in front of you, are you really looking in your rearview mirror?  Let me answer that for you: "No".

Of course nobody knows how they would react until they read police report on the accident.. Point rather is that you have a bit more freedom to avoid hazard in a regular intersection as opposed to curbs bth inside and outside the roundabout. It may only make things worse, after all.
But - and feel free to disagree - I would love to see statistics on a large dataset - probably there are thousands roundabouts which exist for 5+ years. I want that data published and organized by traffic volumes, number of lanes etc.
I would say that is something FHWA must do at some point, better sooner than later. And that should be fairly doable for them as well.

Statistics are all based on samples.  You don't need to get info from everything.  Even getting polling from voters only require a few thousand responses to gage the tens or hundreds of millions that'll be voting.  Sure, there's going to be a poll or two that turns out to be incorrect (and you'll hear about it forever from the candidate that proved it wrong), but by in large, those small samples will be on target.

Thus, you don't need data on a large subset...because what you're really asking for is data on the entire population of roundabouts.  And like others, you'll nitpick to extract the data you want.

[kalvado]

Statistics are all based on samples.  You don't need to get info from everything.  Even getting polling from voters only require a few thousand responses to gage the tens or hundreds of millions that'll be voting.  Sure, there's going to be a poll or two that turns out to be incorrect (and you'll hear about it forever from the candidate that proved it wrong), but by in large, those small samples will be on target.

Thus, you don't need data on a large subset...because what you're really asking for is data on the entire population of roundabouts.  And like others, you'll nitpick to extract the data you want.

statistics has a error margin associated with it. For such low-count event as fatal accident on roundabout, error margin will be huge.
Very roughly speaking, to achieve 5% error margin  you need statistics of sqrt(n)/n=0.05 or n=400 fatal accidents on comparable roundabouts to make a conclusion. If you separate things in 4 groups - say 1x1, 1x2,2x2, more than 2x2 lanes - with 400-500 fatal events in each group -   I suspect you need all historical data to make a somewhat valid conclusion, and even then I am not sure if there is enough events overall.
And pointing out single events on individual intersection - or lack thereof - is only good for a single data record

[6a]

It's not three lanes all the way around, if that's what you're referencing.

The sign correctly displays the number of lanes approaching the roundabout from the north (eastbound along route 33). Unless you're being cheeky, referring to tradephoric's dislike for triple-lane roundabouts.

No, I was being serious. I wasn't sure what he was referring to.

[DaBigE]

The latest crash numbers are in for Madison, WI.

Intersection -- 2015 (2014), change

• Mineral Point @ Pleasant View -- 35 (34), +1
• Lien Rd @ Thompson Rd -- 20 (16), +4
• CTH M @ Valley View Rd -- 16 (18), -2
• Commercial Ave @ Thompson Rd -- 6 (8), -2
• Verona Rd Frontage -- 3 (N/A)
• Eastpark Blvd @ Hanson Rd -- 0 (0), 0
• Thompson Rd @ STH 30 -- 0 (2), -2

• Fatalities -- 0 (0), 0
• Injuries -- 12 (12), 0

2014 Source
2015 Source

What I don't have at my disposal are the volumes. It would be interesting to see how these intersections are performing as compared to how many crashes would be expected vs. actual.

[tradephoric]

The latest crash numbers are in for Madison, WI.

Intersection -- 2015 (2014), change

• Mineral Point @ Pleasant View -- 35 (34), +1
• Lien Rd @ Thompson Rd -- 20 (16), +4
• CTH M @ Valley View Rd -- 16 (18), -2
• Commercial Ave @ Thompson Rd -- 6 (8), -2
• Verona Rd Frontage -- 3 (N/A)
• Eastpark Blvd @ Hanson Rd -- 0 (0), 0
• Thompson Rd @ STH 30 -- 0 (2), -2

• Fatalities -- 0 (0), 0
• Injuries -- 12 (12), 0

2014 Source
2015 Source

What I don't have at my disposal are the volumes. It would be interesting to see how these intersections are performing as compared to how many crashes would be expected vs. actual.

Great stuff DaBigE.  As you mentioned it doesn't include detailed intersection traffic volumes.  But i did find this link which gives link volumes for all the major roads in Madison.  For example, here are the link volumes near Washington Avenue and Stoughton Road (the signalized intersection with the most number of crashes cited in the report).


http://cityofmadison.maps.arcgis.com/apps/webappviewer/index.html?id=8c2d43c18d8542c7bdf8a93a11d7e545

Based on these link volumes, can we get a ballpark estimate of the intersection count?  Once we agree on the methodology for estimating the intersection counts we can do some more meaningful analysis.

[tradephoric]

I estimated the intersection volume at the Washington Ave & Stroughton Road intersection to be the following:

(47200 + 32700 + 56850 + 29800) / 2 =  83275

I used the same methodology to estimate the traffic volumes for the top 5 intersections in Madison with the highest total crashes in 2015 (looking at just signals and roundabouts).  The 2x2 roundabouts in Madison had exceedingly high crash rates when compared to the signalized intersections.

[tradephoric]

There have now been 36 crashes in the first 56 days of operation at the 161/Riverside Drive roundabout in Dublin.  Before the roundabout the intersection only averaged 12 crashes per year.

http://www.thisweeknews.com/content/stories/dublin/news/2016/10/11/state-route-161-riverside-drive-roundabout-growing-supporters-opponents.html

I alluded that this Dublin roundabout would see a lot of crashes.

I don't think anyone ever argued that roundabouts reduce collisions overall. What they argued was that, by reducing conflict points and angle of incidence (particularly head-on and T-bone collisions), they reduce the severity of the collisions that do occur, particularly compared to all-way stop and signalized intersections.

That's exactly what's being argued though.  Listen to what Jeannie Willis has to say about the expected safety benefits of a 3-lane roundabout currently under construction in Dublin, Ohio (6A touched on this roundabout previously in this thread).  What are the residents of Dublin to think if her predictions don't come to pass?  At that point, who cares right?  It will already be constructed.

"They improve safety.  We will reduce crashes. It won't eliminate crashes.  The frequency of the crashes will be reduced and the severity will be reduced, of the crashes, meaning the number of injury related type crashes will be substantially reduced."

-Jeannie Willis, Engineering Manager, City of Dublin

What a reduction in crashes Jeannie!  Great job on your new roundabout.

[tradephoric]

I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.

Said the driver of the black Toyota Camry...


http://www.ktva.com/three-vehicle-collision-closes-dowling-rd-roundabout-541/

[jakeroot]

I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.

Said the driver of the black Toyota Camry...

There's gonna be exceptions, trade.

[kalvado]

I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.

Said the driver of the black Toyota Camry...

There's gonna be exceptions, trade.

Sure, couple more crashes, a little more fatalities- but that is all in the name of safety, we have to understand and accept that!

[cjw2001]

I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.

Said the driver of the black Toyota Camry...

There's gonna be exceptions, trade.

It doesn't bother me in the least that he is able to Google up examples of exceptions.   I drive the roundabouts of Carmel and neighboring cities every single day, I've yet to see the mass carnage in the roundabouts that he predicts.   I'll keep enjoying my vastly improved travel experience and he can post as many exceptions as it takes to make him happy.     

[DAL764]

I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.

Said the driver of the black Toyota Camry...

There's gonna be exceptions, trade.

It doesn't bother me in the least that he is able to Google up examples of exceptions.   I drive the roundabouts of Carmel and neighboring cities every single day, I've yet to see the mass carnage in the roundabouts that he predicts.   I'll keep enjoying my vastly improved travel experience and he can post as many exceptions as it takes to make him happy.     

Clearly you are just living on borrowed time and at some point you, too, will be killed in a massive 50-car roundabout crash that will trigger an explosion so large that will just turn the entirety of Carmel into a massive roundabout with a 3-mile diameter.

[Rothman]

I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.

Said the driver of the black Toyota Camry...

There's gonna be exceptions, trade.

It doesn't bother me in the least that he is able to Google up examples of exceptions.   I drive the roundabouts of Carmel and neighboring cities every single day, I've yet to see the mass carnage in the roundabouts that he predicts.   I'll keep enjoying my vastly improved travel experience and he can post as many exceptions as it takes to make him happy.     

Clearly you are just living on borrowed time and at some point you, too, will be killed in a massive 50-car roundabout crash that will trigger an explosion so large that will just turn the entirety of Carmel into a massive roundabout with a 3-mile diameter.

Congratulations, you just won the Internet for the Day.

[cl94]

I think it is much easier at a roundabout intersection to observe and avoid the driver that blows through the yield sign at the roundabout entrance.  As you approach each spoke you typically have an excellent view of the approaching traffic and can take appropriate action to avoid someone that isn't stopping.

Said the driver of the black Toyota Camry...

There's gonna be exceptions, trade.

It doesn't bother me in the least that he is able to Google up examples of exceptions.   I drive the roundabouts of Carmel and neighboring cities every single day, I've yet to see the mass carnage in the roundabouts that he predicts.   I'll keep enjoying my vastly improved travel experience and he can post as many exceptions as it takes to make him happy.     

Clearly you are just living on borrowed time and at some point you, too, will be killed in a massive 50-car roundabout crash that will trigger an explosion so large that will just turn the entirety of Carmel into a massive roundabout with a 3-mile diameter.

Congratulations, you just won the Internet for the Day.

Except such a thing already exists in Malaysia.

[tradephoric]

Isn't it convenient that circulating vehicles disappear from the roundabout whenever a drunk driver blows through it.  To suggest that an innocent driver could get t-boned inside a roundabout is pure blasphemy to roundabout proponents:

I don't think it is poorly designed, and it improves Maryland traffic safety by "intercepting" some of those impaired motorists before they crash into something else, or a pedestrian or bicyclist.

Roundabouts (properly designed) vs 4-way intersection aren't going to have head-on or t-bone collisions.

If you drive like an idiot you live (or die) with the consequences.  These are the same people that would have blown the stop sign and taken out another car when it was a stop controlled intersection -- I'm much happier with them being stopped by an inanimate object rather than another vehicle.

You never know...there could've been someone traveling on the other side of the roundabout, and the boulder saved the idiot driver from plowing thru the median into their car, killing them instead.

Had it not been a roundabout, we may be talking more fatalities, because the likelihood of a high-speed t-bone collision are that much greater with other intersection types. No intersection control is fog-proof or human-proof.

But, I'd rather a central roundabout island stop a drunk driver, instead of another driver at a four-way intersection. The only loss in the collision above is the driver's car, and a bit of vegetation.

[cl94]

I think it's about time we get a lock on this topic. It has devolved into a flame war.

[jakeroot]

Isn't it convenient that circulating vehicles disappear from the roundabout whenever a drunk driver blows through it.  To suggest that an innocent driver could get t-boned inside a roundabout is pure blasphemy to roundabout proponents:

But are the chances of a T-bone at a roundabout the same as a traditional intersection? No one is trying to say that t-bone collisions disappear with roundabouts (if they are, they're certainly mistaken).

[jakeroot]

I think it's about time we get a lock on this topic. It has devolved into a flame war.

It's staying relatively civil. It's had its ups and downs but no one's getting hurt.

[DaBigE]

Isn't it convenient that circulating vehicles disappear from the roundabout whenever a drunk driver blows through it.  To suggest that an innocent driver could get t-boned inside a roundabout is pure blasphemy to roundabout proponents:
...

Had it not been a roundabout, we may be talking more fatalities, because the likelihood of a high-speed t-bone collision are that much greater with other intersection types. No intersection control is fog-proof or human-proof.

...

IF you insist on throwing labels around, I am NOT a roundabout proponent in the definition you're trying to insinuate; more accurately, I am a traffic engineering REALIST. Again, stop cherry-picking/twisting my words to fit your agenda.

[DaBigE]

I think it's about time we get a lock on this topic. It has devolved into a flame war.

It's staying relatively civil. It's had its ups and downs but no one's getting hurt.

While that may be true, the information well is clearly running dry...the post content is once again are taking a circular nature.