Crash prone 'modern roundabouts'

[kphoger]

1.  It could theoretically allow a free-flowing two-lane right turn out of the hospital parking lot–except that isn't the way they striped and signed it.

2.  It lets southbound traffic on Mason Road skirt around a red light by turning right with a Yield sign, going around the circle, and then turning right on red.   

Based on your reply...I'm keeping it filed under "overuse" .

Yeah, fair enough!

But I kind of doubt it's crash-prone.

[jakeroot]

1.  It could theoretically allow a free-flowing two-lane right turn out of the hospital parking lot–except that isn't the way they striped and signed it.

2.  It lets southbound traffic on Mason Road skirt around a red light by turning right with a Yield sign, going around the circle, and then turning right on red.   

Based on your reply...I'm keeping it filed under "overuse" .

Yeah, fair enough!

But I kind of doubt it's crash-prone.

No, that's true. Probably not a bunch of crashes. Although I still feel like it's overkill. Credit to them for doing something I've not seen done elsewhere, though.

[kphoger]

Could it be for traffic calming?

Left-turning traffic leaving the hospital would otherwise have to contend with cross-traffic accelerating toward WB I-64 from Mason Road.  With the teardrop design, on the other hand, that cross-traffic doesn't start accelerating toward the on-ramp till after the conflict point.

[jakeroot]

Could it be for traffic calming?

Left-turning traffic leaving the hospital would otherwise have to contend with cross-traffic accelerating toward WB I-64 from Mason Road.  With the teardrop design, on the other hand, that cross-traffic doesn't start accelerating toward the on-ramp till after the conflict point.

I actually mentioned that in my original post as being the main advantage:

Only advantage that I can see might be traffic going slower and thus maybe easier to enter the roundabout from the "top" of the image. Still, traffic from the right has only just turned onto the road, so it's not like they're going very fast.

[Occidental Tourist]

Maybe it's the standard explanation given for roundabouts: traffic turning left from the hospital is less likely to get in a severe collision by making the movement in a circle versus the potential T-bone situation of a direct left across traffic coming from the side.

[jakeroot]

Maybe it's the standard explanation given for roundabouts: traffic turning left from the hospital is less likely to get in a severe collision by making the movement in a circle versus the potential T-bone situation of a direct left across traffic coming from the side.

That's a fair point. Although traffic only did just turn onto this road 200 feet before the roundabout. Hard to believe they'd have picked up enough speed to cause any serious crash.

I think I'm going with this explanation: Missouri likes roundabouts.

[kphoger]

Although traffic only did just turn onto this road 200 feet before the roundabout. Hard to believe they'd have picked up enough speed to cause any serious crash.

But see my point from earlier:

Left-turning traffic leaving the hospital would otherwise have to contend with cross-traffic accelerating toward WB I-64 from Mason Road.

It isn't just that traffic is accelerating–it's that a lot of it would be accelerating up to freeway speeds and probably wouldn't much feel like slowing down partway through.

[jakeroot]

That's true as well. The speed limit on the frontage road is only 45 mph, which isn't really fast enough to normally worry about left turns across traffic (although probably the upper limit in most states). But then I doubt most people care about the frontage limit when they fully intend to enter I-64.

Another alternative to the roundabout would have been making this a RIRO, since there is another entrance to the healthcare facility along Mason Road to the north, with full access via a flush median. Problem is that it's signed as "Emergency Access Only", probably because the main entrance is meant to be the roundabout.

Still stranger: there is absolutely no pedestrian access to this facility from anywhere. They were apparently so focused on improving safety for that left turn onto the frontage road, they forgot to implement a safe passage for foot traffic to the hospital.

[cjw2001]

This thread has had a huge amount of discussion regarding roundabouts, but I don't remember anything regarding the use of raised pedestrian crosswalks at the roundabout entries and exits.   This is something Carmel Indiana has been implementing on new roundabouts (and in one case retrofitting an existing roundabout) on the Rangeline Road corridor over the last few years.  These raised crosswalks have a traffic calming effect resulting in reduced speeds as traffic enter and exit each roundabout.  There have also been a few mid block raised crosswalks added as well between roundabouts.

Thoughts?

https://www.google.com/maps/@39.9755516,-86.1271211,3a,75y,169.53h,81.54t/data=!3m6!1e1!3m4!1sfvxFF730r__X4iMXGqqB_Q!2e0!7i13312!8i6656

https://www.google.com/maps/@39.9705177,-86.1270149,3a,75y,194.32h,84.54t/data=!3m6!1e1!3m4!1sZHKbCsrB2aqScLEp8aA66Q!2e0!7i16384!8i8192

https://www.google.com/maps/@39.9632378,-86.1268071,3a,75y,212.05h,75.32t/data=!3m6!1e1!3m4!1s7raZSUavITxTfZjKnjKpWw!2e0!7i16384!8i8192

https://www.google.com/maps/@39.9664102,-86.1269386,3a,75y,188.39h,68.32t/data=!3m6!1e1!3m4!1s3zBt67yZlWrq-HBxlWbIig!2e0!7i16384!8i8192

https://www.google.com/maps/@39.9690558,-86.1270773,3a,75y,17.74h,87.44t/data=!3m6!1e1!3m4!1sqJTPsvSK0RyaG9ZGAvJyXA!2e0!7i16384!8i8192

[kalvado]

This thread has had a huge amount of discussion regarding roundabouts, but I don't remember anything regarding the use of raised pedestrian crosswalks at the roundabout entries and exits.   This is something Carmel Indiana has been implementing on new roundabouts (and in one case retrofitting an existing roundabout) on the Rangeline Road corridor over the last few years.  These raised crosswalks have a traffic calming effect resulting in reduced speeds as traffic enter and exit each roundabout.  There have also been a few mid block raised crosswalks added as well between roundabouts.

Thoughts?

https://www.google.com/maps/@39.9755516,-86.1271211,3a,75y,169.53h,81.54t/data=!3m6!1e1!3m4!1sfvxFF730r__X4iMXGqqB_Q!2e0!7i13312!8i6656

https://www.google.com/maps/@39.9705177,-86.1270149,3a,75y,194.32h,84.54t/data=!3m6!1e1!3m4!1sZHKbCsrB2aqScLEp8aA66Q!2e0!7i16384!8i8192

https://www.google.com/maps/@39.9632378,-86.1268071,3a,75y,212.05h,75.32t/data=!3m6!1e1!3m4!1s7raZSUavITxTfZjKnjKpWw!2e0!7i16384!8i8192

https://www.google.com/maps/@39.9664102,-86.1269386,3a,75y,188.39h,68.32t/data=!3m6!1e1!3m4!1s3zBt67yZlWrq-HBxlWbIig!2e0!7i16384!8i8192

https://www.google.com/maps/@39.9690558,-86.1270773,3a,75y,17.74h,87.44t/data=!3m6!1e1!3m4!1sqJTPsvSK0RyaG9ZGAvJyXA!2e0!7i16384!8i8192

As a guess...
Good idea to improve pedestrian safety.
A lot of struts being replaced by local shops.
Probably decreases intersection throughput - if there is a significant truck traffic, likely to the level of single lane all way stop system.
Only 3 of the links are for roundabout locations.

[cjw2001]

A lot of struts being replaced by local shops.
Probably decreases intersection throughput - if there is a significant truck traffic, likely to the level of single lane all way stop system.
Only 3 of the links are for roundabout locations.

• If taken at low speed the slope transition is pretty gentle on the car.  These aren't your typical speed bumps.  That said they are quite effective at keeping speed in check and drawing attention to possible pedestrian activity.
• No significant truck traffic on this corridor.
• The other 2 links are for a couple of midblock crossing between roundabouts, which helps to keep the overall speed on the corridor in check.   I didn't attempt to link every occurrence, just a few examples.

Also note that the corridor construction is still ongoing.  There will be additional roundabouts added in the near future and Google maps street view doesn't yet reflect recently completed addition of raised crosswalks at the Carmel Drive roundabout.

[jakeroot]

When I last drove through the Carmel area (early July), I got to experience a few of those raised crosswalks.

First impression was that: well, they make sense. If there's a problem with roundabouts, it's that exiting traffic can sometimes move pretty quickly. This helps to curb that a bit. From walking through numerous roundabouts in Fisher around the same time period, traffic entering a roundabout seems pretty good at yielding to pedestrians since they're slowed down, but traffic exiting is mostly focused on speeding up and leaving the roundabout without hitting someone, and pedestrians don't seem to be on their mind.

Other impression is that for busy roundabouts, they may not be advisable. For example, triple lane or double lane roundabouts that are along corridors with speed limits 35 or greater, really should just use RRFBs with zebra crossings (not HAWKs either, unless used for ramp metering, since those can quickly cause gridlock).

[tradephoric]

The grey car driving through the completed Sarasota roundabout at the end of this video pretty much sums up the confusion some drivers have when navigating a roundabout. 

https://www.youtube.com/watch?v=GXst6sNUFDk

[tradephoric]

Another video on how to drive through a roundabout.

https://www.youtube.com/watch?v=67o3NpDaVpc

[jakeroot]

That Florida roundabout seems to be the second example of a "proper" turbo roundabout in North America, right after the turbo roundabout leaving Sidney Airport on Vancouver Island.

Much that like example, this one still features flat islands. I would love to see actual soft bumps.

[tradephoric]

There has been another fatal crash at a Hamburg, NY roundabout this time involving a bicyclist.  Prior to that there had been 2 fatal crashes at the Big Tree/South Park Ave. roundabout after vehicles struck decorative rocks in the central island of the roundabout.  There are examples of counties with over 1 million people that have dozens of roundabouts where there hasn't been a documented roundabout fatality over decades of data.  Yet this small town outside Buffalo has seen 3 roundabout fatalities at their handful of roundabouts.  Either the community has been extremely unlucky or there is something inherently unsafe about their roundabout designs.

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

[jamess]

American drivers at work

https://twitter.com/OregonRolledA20/status/1386160018056093698

[kalvado]

American drivers at work

More like American engineering at its best. They installed roundabout, mission accomplished!
Signage, pavement markings? Why would anyone need that? < /sarcasm>

[jamess]

American drivers at work

More like American engineering at its best. They installed roundabout, mission accomplished!
Signage, pavement markings? Why would anyone need that? < /sarcasm>

Surely you noticed it's actively under construction?

[kalvado]

American drivers at work

More like American engineering at its best. They installed roundabout, mission accomplished!
Signage, pavement markings? Why would anyone need that? < /sarcasm>

Surely you noticed it's actively under construction?

I certainly noticed that it is open for traffic. An  if you ever saw temporary signs in a construction zone, you may have an idea about some possibilities to mitigate confusion like what we see.

[Scott5114]

What are the odds that anyone would have followed the signage and pavement markings even if they were present? It looked like there was a pretty strong follow-the-leader effect there, where once the first guy in line did something stupid, everyone else decided to just copy what they were doing.

[kalvado]

What are the odds that anyone would have followed the signage and pavement markings even if they were present? It looked like there was a pretty strong follow-the-leader effect there, where once the first guy in line did something stupid, everyone else decided to just copy what they were doing.

Which probably means leader was the best hint available.
As it was noticed, this is an area under construction, we don't know how traffic patterns changed during that time.
Google maps don't show new layout; old intersection had some dedicated turn lanes, I can easily see drivers expecting those dedicated lanes to be still present in some way.
Overall, I wonder why roundabout was considered at all when adding a traffic light would be a much more reasonable thing to do.

[wanderer2575]

American drivers at work

https://twitter.com/OregonRolledA20/status/1386160018056093698

I just saw this on humorist Dave Barry's blog today and came here to post, but you beat me to it.

The "Thunder and Blazes" soundtrack was a nice touch.

[jamess]

If we are ok with using the 85 percentile measurement to create rules (since drivers are safe and prudent and all that), I believe the official policy in that intersection is to drive on the left from now on

[ibthebigd]

Kentucky is on a don't put a light fix lately. Where that video is from is a good Roundabout candidate because it doesn't have consistent traffic but is by a lake. Should have been a bigger Roundabout.

Kentucky has been putting J Turns where people would like a light.



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