Crash prone 'modern roundabouts'

[kphoger]

While the roundabout was where the fatal accident occurred, better them slamming into a tree than into another innocent vehicle.

As mentioned in another thread, retractable bollards should be added at signalized intersections.  The bollards would extend up when the signal turns red.  It is better for a red light driver to slam into a bollard than to T-bone somebody already in the intersection.  Would you be in favor of this idea?  I found a crash test on youtube that simulates a red light runner plowing into the bollards.

https://www.youtube.com/watch?v=9FfUlojxiqE

No, inattentive drivers might rear-end someone being stopped by a retractable bollard.

Why is it even possible to drive a straight path into the center island?  Shouldn't deflection direct a driver away from that?  Guardrails (guiderails?) along the approaches might help with that.

Guardrails look fairly ugly for urban locations. And with those curved approaches, number of expensive property-only accidents would go up as people would scrape those rails - while now it is just running the curb.
Some soft stopping items in central island - no trees no concrete - seem to be the least evil.

I think we should just construct everything out of Nerf.  Then people can get away without knowing how to drive at all and still not get injured.

[jakeroot]

The Village Center Circle roundabout is credited as being the first modern roundabout built in America.

Huh, so they were. I always thought the first two were the roundabouts at Hualapai Way and Canyon Run Drive, along Town Center Drive (both full 3x3 roundabouts). However, those didn't fully open until the late 90s! I was way off; the first two along Village Center Circle opened up in 1990. Neither of the Town Center Drive roundabouts must have been very safe, since they replaced the far right lane of each with slip lanes in the early 2000s. They were definitely the first full 3x3 roundabouts in this country, though (the Village Center/Town Drive roundabout had three lanes, but it was more of a T-approach with a driveway at the top) -- although, now that I think of it, I'm not sure any full 3x3 roundabouts were ever built beyond those two? Every other three-lane roundabout has a part with only two lanes.

[kalvado]

I think we should just construct everything out of Nerf.  Then people can get away without knowing how to drive at all and still not get injured.

I still believe red light cameras should be replaced with red light machine guns. You know, just shoot that damn criminal on the spot!

[kphoger]

I think we should just construct everything out of Nerf.  Then people can get away without knowing how to drive at all and still not get injured.

I still believe red light cameras should be replaced with red light machine guns. You know, just shoot that damn criminal on the spot!

But then the car might crash into the central island of a nearby roundabout.

[kalvado]

I think we should just construct everything out of Nerf.  Then people can get away without knowing how to drive at all and still not get injured.

I still believe red light cameras should be replaced with red light machine guns. You know, just shoot that damn criminal on the spot!

But then the car might crash into the central island of a nearby roundabout.

OK, make it red light grenade launcher.

[kphoger]

I think we should just construct everything out of Nerf.  Then people can get away without knowing how to drive at all and still not get injured.

I still believe red light cameras should be replaced with red light machine guns. You know, just shoot that damn criminal on the spot!

But then the car might crash into the central island of a nearby roundabout.

OK, make it red light grenade launcher.

too bulky

[MNHighwayMan]

I think we should just construct everything out of Nerf.  Then people can get away without knowing how to drive at all and still not get injured.

I still believe red light cameras should be replaced with red light machine guns. You know, just shoot that damn criminal on the spot!

But then the car might crash into the central island of a nearby roundabout.

OK, make it red light grenade launcher.

too bulky

Only briefly. Or are we talking about the launcher and not the red light runner?

[tradephoric]

The Village Center Circle roundabout is credited as being the first modern roundabout built in America.

Huh, so they were. I always thought the first two were the roundabouts at Hualapai Way and Canyon Run Drive, along Town Center Drive (both full 3x3 roundabouts). However, those didn't fully open until the late 90s! I was way off; the first two along Village Center Circle opened up in 1990. Neither of the Town Center Drive roundabouts must have been very safe, since they replaced the far right lane of each with slip lanes in the early 2000s. They were definitely the first full 3x3 roundabouts in this country, though (the Village Center/Town Drive roundabout had three lanes, but it was more of a T-approach with a driveway at the top) -- although, now that I think of it, I'm not sure any full 3x3 roundabouts were ever built beyond those two? Every other three-lane roundabout has a part with only two lanes.

Caltrans reclassified the Los Alamitos Circle in Long Beach from a traffic circle to a modern roundabout in 1993.  But they basically just converted it from stop control to yield control and the basic design still mimics that of a "traffic circle".  I personally wouldn't consider it a modern roundabout, but the Los Alamitos Circle does have triple entry lanes at all 4 approaches.

[jakeroot]

The Village Center Circle roundabout is credited as being the first modern roundabout built in America.

Huh, so they were. I always thought the first two were the roundabouts at Hualapai Way and Canyon Run Drive, along Town Center Drive (both full 3x3 roundabouts). However, those didn't fully open until the late 90s! I was way off; the first two along Village Center Circle opened up in 1990. Neither of the Town Center Drive roundabouts must have been very safe, since they replaced the far right lane of each with slip lanes in the early 2000s. They were definitely the first full 3x3 roundabouts in this country, though (the Village Center/Town Drive roundabout had three lanes, but it was more of a T-approach with a driveway at the top) -- although, now that I think of it, I'm not sure any full 3x3 roundabouts were ever built beyond those two? Every other three-lane roundabout has a part with only two lanes.

Caltrans reclassified the Los Alamitos Circle in Long Beach from a traffic circle to a modern roundabout in 1993.  But they basically just converted it from stop control to yield control and the basic design still mimics that of a "traffic circle".  I personally wouldn't consider it a modern roundabout, but the Los Alamitos Circle does have triple entry lanes at all 4 approaches.

That's true. Though as far as I can tell from Historic Aerials, from when the 3x3 Summerlin roundabouts opened to around 2003, they also lacked markings. So in a way, the Los Alamitos Circle was indeed the first 3x3 modern roundabout, relative to the standards of the era.

I'm 99% sure the first "three lane" roundabout in the US (that also had markings, which the Long Beach, Summerlin, and I-70 Vail/Avon roundabouts lacked) was the 18 1/2 & Van Dyke roundabout in Sterling Heights. Unless you know of an earlier one.

[tradephoric]

I'm 99% sure the first "three lane" roundabout in the US (that also had markings, which the Long Beach, Summerlin, and I-70 Vail/Avon roundabouts lacked) was the 18 1/2 & Van Dyke roundabout in Sterling Heights. Unless you know of an earlier one.

I believe the first triple lane modern roundabout with lane markings was the I-95 and Ritchie Marlboro Road roundabouts in Maryland (opened in 2003). 

https://www.google.com/maps/@38.8687399,-76.8449236,575m/data=!3m1!1e3

EDIT:  Nevermind, scratch that.  They were originally 2-lane roundabouts with the third lane going in around 2010.  I think you are right, the Van Dyke roundabout was the first.

[jakeroot]

I'm 99% sure the first "three lane" roundabout in the US (that also had markings, which the Long Beach, Summerlin, and I-70 Vail/Avon roundabouts lacked) was the 18 1/2 & Van Dyke roundabout in Sterling Heights. Unless you know of an earlier one.

I believe the first triple lane modern roundabout with lane markings was the I-95 and Ritchie Marlboro Road roundabouts in Maryland (opened in 2003). 

https://www.google.com/maps/@38.8687399,-76.8449236,575m/data=!3m1!1e3

EDIT:  Nevermind, scratch that.  They were originally 2-lane roundabouts with the third lane going in around 2010.  I think you are right, the Van Dyke roundabout was the first.

Regardless, that's pretty interesting that a roundabout was widened from two lanes to three. I've heard of roundabouts going from one lane to two, but not two to three.

[tradephoric]

And, as this is supposedly the 'first' modern roundabout, if there have been no other fatal accidents here, speaks to how well the roundabout has worked over the years.  Even the most safest roads will have a rare fatal on occasion; mostly due to other circumstances, which in this case was a drunk driver transporting an unbuckled passenger.

The Summerlin roundabout really hasn't performed well.  It is estimated there are 311,000 traffic signals in America.  If signals averaged a fatal crash every 27 years, there would be 11,518 traffic signal fatalities each year.  According to the FHWA, there were 2,924 fatalities at intersections controlled by traffic signals in 2007.  I'll take 2,924 fatalities over 11,518 fatalities any day.  Good thing traffic signals average fewer fatal crashes than the inaugural modern roundabout in Summerlin does.

https://safety.fhwa.dot.gov/intersection/other_topics/fhwasa10005/brief_2.cfm

[jeffandnicole]

And, as this is supposedly the 'first' modern roundabout, if there have been no other fatal accidents here, speaks to how well the roundabout has worked over the years.  Even the most safest roads will have a rare fatal on occasion; mostly due to other circumstances, which in this case was a drunk driver transporting an unbuckled passenger.

The Summerlin roundabout really hasn't performed well.  It is estimated there are 311,000 traffic signals in America.  If signals averaged a fatal crash every 27 years, there would be 11,518 traffic signal fatalities each year.  According to the FHWA, there were 2,924 fatalities at intersections controlled by traffic signals in 2007.  I'll take 2,924 fatalities over 11,518 fatalities any day.  Good thing traffic signals average fewer fatal crashes than the inaugural modern roundabout in Summerlin does.

https://safety.fhwa.dot.gov/intersection/other_topics/fhwasa10005/brief_2.cfm

Nothing you rambled has anything to do with that specific roundabout.

[jakeroot]

The Summerlin roundabout really hasn't performed well.

Based on what evidence? I suspect it probably has performed pretty well, because half the roundabout is single lane.

[tradephoric]

Nothing you rambled has anything to do with that specific roundabout.

Do you realize that traffic signals in America average one fatality every 100 years?  The Summerlin roundabout, which is one of the first modern roundabouts in the nation, had a fatal crash after just 27 years.  In 73 years time, how many more people will slam into the palm trees of that Summerlin roundabout? 

[jakeroot]

Nothing you rambled has anything to do with that specific roundabout.

Do you realize that traffic signals in America average one fatality every 100 years?  The Summerlin roundabout, which is one of the first modern roundabouts in the nation, had a fatal crash after just 27 years.  In 73 years time, how many more people will slam into the palm trees of that Summerlin roundabout?

I'm sure there are many signals with fatality rates greater than once-every-73-years. Should a roundabout's standard be that of the worst-performing traffic light? Probably not. But, me and J&N would like to see some numbers before a conclusion is reached here.

If you can't find any, just say it. I'd look it up, but if you can't find any numbers, I doubt I'd be able to.

[tradephoric]

I'm sure there are many signals with fatality rates greater than once-every-73-years. Should a roundabout's standard be that of the worst-performing traffic light? Probably not. But, me and J&N would like to see some numbers before a conclusion is reached here.

Let's look at a localized example.  I keep going back to SE Michigan because SEMCOG has compiled a tremendous amount of publicly available crash data that anyone can analyze.  Over the past decade, there have been 3 fatal crashes at the top 20 most crash prone intersections.  Analyzing 20 intersections over a 10 year period is equivalent to 200 years of crash data.  Extrapolating the numbers, the SE Michigan intersections have averaged a fatal crash every 66.6 years (200 years of data / 3 fatal crashes).  These are some of the heaviest traveled intersections in the region and they only average a fatal crash every 66.6 years. 


http://semcog.org/High-Frequency-Crash-Locations

[Occidental Tourist]

Caltrans reclassified the Los Alamitos Circle in Long Beach from a traffic circle to a modern roundabout in 1993.  But they basically just converted it from stop control to yield control and the basic design still mimics that of a "traffic circle".  I personally wouldn't consider it a modern roundabout, but the Los Alamitos Circle does have triple entry lanes at all 4 approaches.

How is the Los Alamitos Circle in its current configuration not the same configuration as a roundabout?

[jakeroot]

Caltrans reclassified the Los Alamitos Circle in Long Beach from a traffic circle to a modern roundabout in 1993.  But they basically just converted it from stop control to yield control and the basic design still mimics that of a "traffic circle".  I personally wouldn't consider it a modern roundabout, but the Los Alamitos Circle does have triple entry lanes at all 4 approaches.

How is the Los Alamitos Circle in its current configuration not the same configuration as a roundabout?

If you want to be strict, technically it's too big to be classified as a modern roundabout (a stupid requirement in my opinion), but more importantly, it lacks guidance lines. Many of the east coast "traffic circles" have been converted to yield control for all entries, but they still lack guidance lines so they are still often referred to as traffic circles or rotaries.

That said, due to the sheer number of lanes that flow through the Los Alamitos Circle, I think it works better without guidance lines. Apparently the British who helped design it agree, since they're the reason there isn't any today.

[Occidental Tourist]

Caltrans reclassified the Los Alamitos Circle in Long Beach from a traffic circle to a modern roundabout in 1993.  But they basically just converted it from stop control to yield control and the basic design still mimics that of a "traffic circle".  I personally wouldn't consider it a modern roundabout, but the Los Alamitos Circle does have triple entry lanes at all 4 approaches.

How is the Los Alamitos Circle in its current configuration not the same configuration as a roundabout?

If you want to be strict, technically it's too big to be classified as a modern roundabout (a stupid requirement in my opinion), but more importantly, it lacks guidance lines. Many of the east coast "traffic circles" have been converted to yield control for all entries, but they still lack guidance lines so they are still often referred to as traffic circles or rotaries.

That said, due to the sheer number of lanes that flow through the Los Alamitos Circle, I think it works better without guidance lines. Apparently the British who helped design it agree, since they're the reason there isn't any today.

Ah ha.  Thanks.

[kalvado]

Nothing you rambled has anything to do with that specific roundabout.

Do you realize that traffic signals in America average one fatality every 100 years?  The Summerlin roundabout, which is one of the first modern roundabouts in the nation, had a fatal crash after just 27 years.  In 73 years time, how many more people will slam into the palm trees of that Summerlin roundabout?

You're disappointing here.
First, not all intersections are equal. Normalizing per MEV as commonly done  is a semi-descent metric.
Second, you need statistics in order to draw numeric conclusions. If you consider the day fatal accident happened - then just think about other 36500 days within 100 years?? 
You need at least 10 events to talk reasonable statistic trends - and, thanks god, there are really few places which have that many fatal events over reasonable timeframe. That is why we either talk about less severe more common events, or consider larger ensembles of similar objects for statistical purposes.

[tradephoric]

First, not all intersections are equal. Normalizing per MEV as commonly done  is a semi-descent metric.

I was trying to give the roundabout every chance to succeed.  The Summerlin roundabout, a town center roundabout with an AADT of maybe 20k, was compared to the highest crash location in a region of 4.3 million people. Each individual intersection analyzed in SE Michigan had AADTs ranging from 40k to close to 100k.  The SE Michigan intersections - which carry significantly more traffic than the Summerlin roundabout - averaged a fatal crash every 66.6 years.  The Summerlin roundabout had a fatal crash after 27 years.  One of the nation's inaugural modern roundabout in Summerlin has averaged a fatal crash faster than even the worst performing intersections in SE Michigan. 

J&N cited the fact that the Summerlin roundabout had one fatal crash in 27 years as proof that the roundabout is performing well.  If fatalities is the metric used to determine if a roundabout is performing well, I would disagree with them (unless if a fatality at over twice the rate of the worst performing intersections is seen as a good thing). 

And, as this is supposedly the 'first' modern roundabout, if there have been no other fatal accidents here, speaks to how well the roundabout has worked over the years.

[billpa]

I was trying to give the roundabout every chance to succeed.

I doubt that very much.

SM-T230NU

[tradephoric]

Many close calls for this driver at roundabouts in 2017.  Supposedly this is just part 1 and focuses on "failure to yield".

https://www.youtube.com/watch?v=zShxhYSA7Dc

[jakeroot]

Many close calls for this driver at roundabouts in 2017.  Supposedly this is just part 1 and focuses on "failure to yield".

https://www.youtube.com/watch?v=zShxhYSA7Dc

Interesting. When I search "roundabout fails" on Youtube, this video is the sixth result. I wonder what you could have searched...