Crash prone 'modern roundabouts'

[Rothman]

Looks like 11 Mile Road/I-696 @ Van Dyke needs a roundabout.

Looks like DOTs should not be allowed to design roundabout until supervised by a responsible adult.

At least I make sense.

That's fine, make whatever you want - just don't design things.

Ok.  We'll let engineers design the roundabout that will lower the injuries at the worst intersection in Michigan.

Are they going to ask for more H-1Bs for that?

Not sure what you mean by this, but there's a very ugly worst case scenario behind your intent.

Just simple understanding that roundabout design and use isn't developed in US.
There is seemingly no progress in developing the understanding in the past 10 years, so learning from outside experts is the only option.

Given my experience in the industry and the innovations introduced over the years in my own career, I disagree with this assessment.

[kalvado]

Looks like 11 Mile Road/I-696 @ Van Dyke needs a roundabout.

Looks like DOTs should not be allowed to design roundabout until supervised by a responsible adult.

At least I make sense.

That's fine, make whatever you want - just don't design things.

Ok.  We'll let engineers design the roundabout that will lower the injuries at the worst intersection in Michigan.

Are they going to ask for more H-1Bs for that?

Not sure what you mean by this, but there's a very ugly worst case scenario behind your intent.

Just simple understanding that roundabout design and use isn't developed in US.
There is seemingly no progress in developing the understanding in the past 10 years, so learning from outside experts is the only option.

Given my experience in the industry and the innovations introduced over the years in my own career, I disagree with this assessment.

Well, I guess the only option at this point is to agree that we disagree, and time will tell...

[kphoger]

H

A

P

P

Y

.

G

O

A

T

[kalvado]

H

A

P

P

Y

.

G

O

A

T

Thank you, Mr. Goat! I hope you're happy!

[tradephoric]

They must be buddies, but how is the second driver that brain dead?!  I'd be interested to see official crash data for this roundabout, but the Milwaukee Roundabout youtube page documented 85 crashes from the first video posted on 4/11/21 to the last video posted on 8/28/22. The page was gaining notoriety similar to that website that was dedicated to the "11-foot-8 bridge" at the Norfolk Southern–Gregson Street Overpass.

[tradephoric]

This Oak Cliff roundabout in Dallas has seen two separate accidents 3 months apart where a vehicle crashed into a nearby townhouse.  While emergency services were tending to the latest incident, two pedestrians almost get struck by an apparent intoxicated driver who drove through the grass.

According to the news report this roundabout has seen a reduction in crashes from 17 the 3 years prior to the roundabout to 8 the 3 years after the roundabout.  It's just of those 8 crashes, 25% of them end up with a driver crashing into town houses.

[tradephoric]

^Potential solution would be to plant hedges along the central island to block drivers view of the far side of the roundabout.  The way the roundabout is offset, drivers approaching the roundabout can see tail lights directly infront of them from vehicles who have already circulated the roundabout, and they may assume it's just a straight section of road infront of them.  At most roundabouts, the central island raised berm blocks the view of vehicles on the far side as you approach the roundabout but that's not the case here.  There appears to be some visual clue that makes drivers believe they are traveling on a straight section of road as they are approaching this roundabout.

[mrsman]

They must be buddies, but how is the second driver that brain dead?!  I'd be interested to see official crash data for this roundabout, but the Milwaukee Roundabout youtube page documented 85 crashes from the first video posted on 4/11/21 to the last video posted on 8/28/22. The page was gaining notoriety similar to that website that was dedicated to the "11-foot-8 bridge" at the Norfolk Southern–Gregson Street Overpass.

I believe they were probably racing each other.

I know I've commented about this one upthread.  This seems like an easy one to get removed and redesigned to make it safer.

Block 5th at West Virginia.  Convert the roundabout into a signalized T-intersection between 6th and Florida.  West Virginia between 5th and 6th can be two-ways.

There would be no need for a roundabout if only two streets intersect here.

The fact that there are so many crashes screams that something dramatic needs to be done.

[mrsman]

It seems like this intersection could have been designed more like the southern intersection of Polk and Tyler.  Not too many movements, and a regular intersection could probably avoid some of the problems with the roundabout.

[Scott5114]

Would it really be safer if these idiots were racing through a T intersection? Then they can T-bone someone,  instead of getting filtered out by the roundabout.

As someone who lives in a city where reckless driving like this is commonplace, it really isn't a bad thing to have people like that crash into something like a roundabout or other traffic control device before they can crash into some innocent bystander, someone's property, etc.

[tradephoric]

As someone who lives in a city where reckless driving like this is commonplace, it really isn't a bad thing to have people like that crash into something like a roundabout or other traffic control device before they can crash into some innocent bystander, someone's property, etc.

A driver plows through the Polk/Tyler roundabout and proceeds to crash into a condo building.  Having a roundabout at this location didn't prevent a reckless driver from crashing into someone's property.  In fact, multiple reckless drivers have recently crashed into those condo buildings.

[Rothman]

As someone who lives in a city where reckless driving like this is commonplace, it really isn't a bad thing to have people like that crash into something like a roundabout or other traffic control device before they can crash into some innocent bystander, someone's property, etc.

A driver plows through the Polk/Tyler roundabout and proceeds to crash into a condo building.  Having a roundabout at this location didn't prevent a reckless driver from crashing into someone's property.  In fact, multiple reckless drivers have recently crashed into those condo buildings.

Sounds like a reckless driver issue rather than a roundabout issue...

[tradephoric]

Interestingly enough, professional engineers don't ignore crashes that are caused by reckless drivers when analyzing the safety of an intersection.

[kalvado]

Interestingly enough, professional engineers don't ignore crashes that are caused by reckless drivers when analyzing the safety of an intersection.

American engineers do. But "American engineer" starts to sound like a "Florida man"

[paulthemapguy]

Yeah, actual traffic engineer here. No traffic engineer sees any crash that affects people as something they should just ignore. A traffic engineer may still distinguish between crashes that follow a pattern and anomalous crashes. If an engineering decision is changed to prevent many crashes that fit into a whole category of similar crashes, then an engineer will likely choose the design change that prevents more crashes, as opposed to making the change that prevents one anomalous crash.

[tradephoric]

1-year review: Rockford's one-lane roundabout reduces accidents, but causes delays
https://www.mystateline.com/news/local-news/roundabout-reduction-accidents-traffic/

[paulthemapguy]

Wow, that's a horrifically designed roundabout if you actually take a look at it. The people who designed it had no idea what they were doing.

https://maps.app.goo.gl/uGThhwC1pNj8Dv528

[kalvado]

Wow, that's a horrifically designed roundabout if you actually take a look at it. The people who designed it had no idea what they were doing.

https://maps.app.goo.gl/uGThhwC1pNj8Dv528

I thought that approach is pretty much an industry standard.

[jakeroot]

Wow, that's a horrifically designed roundabout if you actually take a look at it. The people who designed it had no idea what they were doing.

https://maps.app.goo.gl/uGThhwC1pNj8Dv528

I thought that approach is pretty much an industry standard.

I agree, I don't see any major differences between the Rockford roundabout and most other two-lane roundabouts.

The only thing about the Rockford roundabout, that might be unusual, is the very small design. I think two-lane roundabouts should be a bit bigger, which might allow for a longer curved entrance (as opposed to a very short curve directly into the roundabout).

[paulthemapguy]

The inside lane of the circulating roadway is inescapable. You can't do a two-lane roundabout in all directions, unless you spawn lanes near the center and have them spiral outward. If a four-lane road intersects a two-lane road, you can get away with having two-lane approaches across from each other. But a configuration with two-lane approaches on all four sides is impossible without lanes that spiral outward.

[kalvado]

The inside lane of the circulating roadway is inescapable. You can't do a two-lane roundabout in all directions, unless you spawn lanes near the center and have them spiral outward. If a four-lane road intersects a two-lane road, you can get away with having two-lane approaches across from each other. But a configuration with two-lane approaches on all four sides is impossible without lanes that spiral outward.

1. Nope. Outer lane exits at every branch, you turn from inner to outer lane at that point. Look at the pavement marks
2. I was referring to design by those who have no clue as a standard practice.

[jakeroot]

The inside lane of the circulating roadway is inescapable. You can't do a two-lane roundabout in all directions, unless you spawn lanes near the center and have them spiral outward. If a four-lane road intersects a two-lane road, you can get away with having two-lane approaches across from each other. But a configuration with two-lane approaches on all four sides is impossible without lanes that spiral outward.

And we wonder why these things have so many crashes...

As noted above, this analysis is thoroughly incorrect. Inside lane can turn into either lane at the crossover point. Outer lane must always exit. This has been the case at modern roundabouts since their invention in the 1960s by Frank Blackmore/TRL, and is only not the case when specifically painted or indicated otherwise.

[kalvado]

The inside lane of the circulating roadway is inescapable. You can't do a two-lane roundabout in all directions, unless you spawn lanes near the center and have them spiral outward. If a four-lane road intersects a two-lane road, you can get away with having two-lane approaches across from each other. But a configuration with two-lane approaches on all four sides is impossible without lanes that spiral outward.

And we wonder why these things have so many crashes...

As noted above, this analysis is thoroughly incorrect. Inside lane can turn into either lane at the crossover point. Outer lane must always exit. This has been the case at modern roundabouts since their invention in the 1960s by Frank Blackmore/TRL, and is only not the case when specifically painted or indicated otherwise.

Seems like a few of such things can be used as a litmus test.
Those insisting on KREP (usually for others) are the most aggressive drivers, those who love roundabouts are those who don't know how to use them ..

[kphoger]

The inside lane of the circulating roadway is inescapable. You can't do a two-lane roundabout in all directions, unless you spawn lanes near the center and have them spiral outward. If a four-lane road intersects a two-lane road, you can get away with having two-lane approaches across from each other. But a configuration with two-lane approaches on all four sides is impossible without lanes that spiral outward.

wtf?

1.  The inside lane of the circulating roadway is escapable at every exit point.  The pavement is even striped as such.

2.  Two-lane roundabouts that don't spawn lanes and spiral them outward are... well, those are just normal two-lane roundabouts.  Totally common.  Just thinking of some I personally remember driving through:  example, example.

3.  It is certainly not impossible to have a configuration of two-lane approaches on all four sides without lanes that spiral outward.  See point #2 above.

[paulthemapguy]

Outer lane must always exit. This has been the case at modern roundabouts since their invention in the 1960s by Frank Blackmore/TRL, and is only not the case when specifically painted or indicated otherwise.

Wrong. Northbound and southbound exits from this roundabout in this example shown in the MUTCD are shown as a straight/right option lane. Please learn about roundabout design before commenting on roundabout design.


Screenshot 2025-06-08 144309 by Paul Across America, on Flickr

The inside lane of the circulating roadway is inescapable. You can't do a two-lane roundabout in all directions, unless you spawn lanes near the center and have them spiral outward. If a four-lane road intersects a two-lane road, you can get away with having two-lane approaches across from each other. But a configuration with two-lane approaches on all four sides is impossible without lanes that spiral outward.

1. Nope. Outer lane exits at every branch, you turn from inner to outer lane at that point. Look at the pavement marks
2. I was referring to design by those who have no clue as a standard practice.

I'm trying to explain to those who will listen (not you, apparently) why this failed design of a roundabout is begging for rampant crashes. I'm talking about what happens in practice, not what's painted on the road. You can't escape the inner lane of a circulating roadway if there is a car in the outer lane. If you're in the inner lane, and there's a car in the outer lane, your only way out of the roundabout is to risk crashing into it.

If you're in the left lane of an approach to the roundabout, it has to spiral you outward into a left turn. I don't see that happening here. See this example shown in the MUTCD. See those lanes getting generated at the center of the roundabout? The little yellow hatched triangles? Why are those there?


Screenshot 2025-06-08 144309 by Paul Across America, on Flickr

And for me to say a roundabout generating tons of crashes is a bad design, and for you to disagree, does that mean you want more crashes? Whose side are you on?