Crash prone 'modern roundabouts'

[kphoger]

A drunk driver speeding through a standard non-roundabout intersection and hitting another vehicle is also likely to result in a fatality.  But highlighting it in this thread implies that the fatality is somehow due to the intersection's being a roundabout.

[kalvado]

A drunk driver speeding through a standard non-roundabout intersection and hitting another vehicle is also likely to result in a fatality.  But highlighting it in this thread implies that the fatality is somehow due to the intersection's being a roundabout.

It really depends. If it is a one off event, then you have a point. if, as Trade said

Apart from the major increases in crashes ever since the roundabout was built there has now been a fatality.   

Then it's just another datapoint.

[kphoger]

Then it's just another datapoint.

I agree.  Just another datapoint.  Unnoteworthy, so far as the intersection design is concerned.

[kalvado]

Then it's just another datapoint.

I agree.  Just another datapoint.  Unnoteworthy, so far as the intersection design is concerned.

Fatal accident is generally a noteworthy datapoint for an intersection. Moreso if it occurs with high level of non-fatal crashes

[jakeroot]

I agree.  Just another datapoint.  Unnoteworthy, so far as the intersection design is concerned.

Fatal accident is generally a noteworthy datapoint for an intersection. Moreso if it occurs with high level of non-fatal crashes

They are now, to be sure. But fatality crashes did seem tolerated (to an extent) into the early 2000s. Crash rates had been dropping for decades and so too was the serious injury/fatality rate. But after fatality/serious injury rates began to rise around ten years ago, a lot more attention has been paid to them. Even those that seem to have nothing to do with engineering.

The problem with roundabouts is that they have a 100% crash rate among those drivers who fail to circumnavigate the roundabout. Outside of roundabouts, I cannot think of an intersection design (applicable to major intersections) where a geometric hazard is considered good design.

[kphoger]

Outside of roundabouts, I cannot think of an intersection design (applicable to major intersections) where a geometric hazard is considered good design.

Some skewed intersections have the side-road do a sinuous route in order to meet up at closer to 90°.  Not sure if that counts.

[kalvado]

Outside of roundabouts, I cannot think of an intersection design (applicable to major intersections) where a geometric hazard is considered good design.

Some skewed intersections have the side-road do a sinuous route in order to meet up at closer to 90°.  Not sure if that counts.

And any T intersection in general, where failure to stop on asymmetric leg can be anything from a guardrail damage to a flight off the cliff

[jakeroot]

Cross-posting from the Washington thread:

SR-9 to be reduced to one lane at SR-204 due to a high number of crashes in the roundabout (which are dropping, apparently...but not enough?)

It's amazing that we went from the initial plan of SR-9 grade separation down to a single southbound through lane. It's a shame they couldn't spring for a flyover, because now there's fewer southbound through lanes then 30 years ago.

https://wsdotblog.blogspot.com/2026/08/sr-9-sr-204-roundabout.html

[CoreySamson]

^^^ Why would you put the roundabout there with that side road?

Anyways, I came to this thread today because I discovered this near Cleveland, TX in the much beleaguered Colony Ridge subdivision:
https://maps.app.goo.gl/inaERaymSWMVmrJ56
https://maps.app.goo.gl/4aLR9CNvaAnRdzfG6

Is this the right way to mark a multilane roundabout? Because it doesn't look right to me.

[Scott5114]

Is this the right way to mark a multilane roundabout?

Hell no. Holy conflict points, Batman!

[jakeroot]

^^^ Why would you put the roundabout there with that side road?

The whole area is full of them. It's a totally botched setup on all counts, in my opinion: too many roundabouts too close together, too much traffic, too many chicanes, too many slip lanes...it's just a mess.

https://www.google.com/maps/@48.0038671,-122.1083555,434a,35y,119.86h,14.12t/data=!3m1!1e3?entry=ttu&g_ep=EgoyMDI2MDgxOS4wIKXMDSoASAFQAw%3D%3D

Anyways, I came to this thread today because I discovered this near Cleveland, TX in the much beleaguered Colony Ridge subdivision:
https://maps.app.goo.gl/inaERaymSWMVmrJ56
https://maps.app.goo.gl/4aLR9CNvaAnRdzfG6

Is this the right way to mark a multilane roundabout? Because it doesn't look right to me.

That whole area, including the design of the roundabouts, looks straight out of the 80s. I'm stunned this is a development from the last ten years. The roundabouts themselves are so...80s looking. Very European too, with straight-on entry/exit legs.

Hell no. Holy conflict points, Batman!

While I can see your concern, I think this is MUTCD compliant. Marking the section beyond that exit as two lanes probably isn't kosher, but I don't think it's disallowed either.

[Scott5114]

While I can see your concern, I think this is MUTCD compliant. Marking the section beyond that exit as two lanes probably isn't kosher, but I don't think it's disallowed either.

So if someone in the left lane wants to get out of the roundabout and the person in the right lane doesn't, and they each follow the lane markings there...What happens?

That whole area, including the design of the roundabouts, looks straight out of the 80s. I'm stunned this is a development from the last ten years. The roundabouts themselves are so...80s looking.

I think it's because the closely-spaced dashed lines and lack of edge lines give it dead-mall-parking-lot vibes.

[jakeroot]

While I can see your concern, I think this is MUTCD compliant. Marking the section beyond that exit as two lanes probably isn't kosher, but I don't think it's disallowed either.

So if someone in the left lane wants to get out of the roundabout and the person in the right lane doesn't, and they each follow the lane markings there...What happens?

That's pretty normal, though, no?

https://maps.app.goo.gl/CdXU3LBnnpEMPzV28

Traffic in the "outer" lane of a roundabout rarely is permitted to continue around a roundabout unless it's expressly marked as permitted.

That whole area, including the design of the roundabouts, looks straight out of the 80s. I'm stunned this is a development from the last ten years. The roundabouts themselves are so...80s looking.

I think it's because the closely-spaced dashed lines and lack of edge lines give it dead-mall-parking-lot vibes.

For sure. And the lack of truck apron, lack of crosswalks or sidewalks...just devoid of all normal features!

[CoreySamson]

That whole area, including the design of the roundabouts, looks straight out of the 80s. I'm stunned this is a development from the last ten years. The roundabouts themselves are so...80s looking.

I think it's because the closely-spaced dashed lines and lack of edge lines give it dead-mall-parking-lot vibes.

For sure. And the lack of truck apron, lack of crosswalks or sidewalks...just devoid of all normal features!

The road infrastructure with the geometry and lane lines specifically reminds me of something you'd see in a newer middle-class development in Mexico:

Reynosa: https://maps.app.goo.gl/hBHyT7MohkrBWpSi9
Cancun: https://maps.app.goo.gl/TG5TSQ1MNgUFZ8FY8
Outside Heroica Veracruz: https://maps.app.goo.gl/uyjMqpXHHvAxGrL87

[kalvado]

Traffic in the "outer" lane of a roundabout rarely is permitted to continue around a roundabout unless it's expressly marked as permitted.

I would say that you should have not more than 1 option lane.
As constructed, they can designate either lane as option, with some excessive pavement to support that designation. Could be that they wanted both variants to be available?

[kphoger]

Unless the lanes are otherwise marked, I approach a multi-lane roundabout with this assumption:

right lane = right turn or straight ahead
left lane = left turn or straight ahead

[kalvado]

Unless the lanes are otherwise marked, I approach a multi-lane roundabout with this assumption:

right lane = right turn or straight ahead
left lane = left turn or straight ahead

This implies low fraction of left turning traffic..