Crash prone 'modern roundabouts'

[tradephoric]

Flying cars a real thing in Romania.  Incredibly the driver avoided life-threatening injuries.

[jakeroot]

@Tom958 likely finds this more interesting than anyone else:

At I-25 and Castle Rock Pkwy, in Castle Rock, CO, the roundabout at the ramp terminus (a trumpet interchange) has markings inconsistent with the arrows, which were added at a much later date:

https://maps.app.goo.gl/swoL9JeZHa8K4qaYA

Taken at face value, the spiral markings imply that the two off-ramp lanes from I-25 southbound can both go left at the roundabout, immediately back onto I-25. That obviously makes no sense, and both lanes should instead be able to carry on southbound onto Promenade Pkwy. This is what they want, apparently, as straight arrows were added to both southbound lanes and cars already seem to exit from the "inside" lane; signs were also added.

Seems weird that they wouldn't just repaint the spiral markings so they continue onto Promenade instead of circulating to the left, more or less implying a double left turn at that point. They should then add some other type of dotted line for traffic entering from the left (eastbound) so they know that the two lanes at that point in the roundabout are for them to continue straight onto (kind of like this in Wisconsin, though maybe a bit more prominent).

[mrsman]

I'd personally much rather someone doing three times the speed limit plow into a rock than fifteen people.

What if the person is a bus driver carrying 15 people?

If a bus driver carrying fifteen people plows into fifteen people instead of a rock, then that would be a total of thirty.  So, still better.

Is there anything specific about the design that makes the Silver Springs NV roundabout so deadly?

Every road has a single lane approach.

Is it more deadly than the previous all-way stop condition?

[mrsman]

Half of the most crash prone intersections in Michigan during 2024 were at roundabouts.  Par for the course anymore.

MAP: Michigan's most dangerous intersections based on crash data
https://www.fox2detroit.com/news/map-michigans-most-dangerous-intersections-based-crash-data

1. 11 Mile Rd/I 696 @ Van Dyke Ave, Warren, 185 Total Crashes, 26 Injuries
2. 18 1/2 Mile Rd @ Van Dyke Ave, Sterling Heights, 162 Total Crashes, 12 Injuries (Roundabout)
3. Martin Pkwy @ N Pontiac Trl, Commerce Township, 151 Total Crashes, 9 Injuries (Roundabout)
4. Schoolcraft Rd @ Telegraph Rd, Redford Township, 137 Total Crashes, 26 Injuries
5. N Hamilton St @ Washtenaw Ave, Ypsilanti, 132 Total Crashes, 7 Injuries           
6. Orchard Lake Rd @ 14 Mile Rd, Farmington Hills, 109 Total Crashes, 5 Injuries (Roundabout)

Geez... Van Dyke Ave takes no prisoners.

It is interesting how some states will go head over heels to reduce or eliminate left turns, especially through installing DDIs. Yet in Michigan, none of the highest crash-rate intersections involve true "direct left" turns like at a standard signal.

A bit off-topic...but what in the world was going on at Hamilton/Washtenaw in Ypsilanti? Hard to believe that many crashes could occur at such a small intersection. I see they rebuilt it recently.

While I've never been to the area, I had the same question and so I did look and see that they've changed the setup of the intersection recently.  Apparently, the route of M-17 (not shown on Google Maps, but I found it on wikipedia) was meant as a through-town routing from US 12 to US 23.  [There's also a business US 12, but M-17 goes more through the heart of town and closer to the EMU campus.]  The eastbound routing is: Washtenaw, right on Hamilton, left on Michigan and westbound is: Michigan, right on Huron, left on Cross, continue onto Washtenaw.

At the corner of Washtenaw/Hamilton and Huron/Cross there used to be slip ramps to allow people to make the turns to stay on M-17 without stopping and yielding, except for pedestrians.  I imagine this wasn't considered safe for peds or bikes, so the DOT (don't know if this is city, county, or state) changed it and added in bike lanes and closed the slip ramp.

Apparently, one key problem with the changes is that Washtenaw is now two lanes approaching Hamilton.  Right lane requires a right and left lane is straight or right.  Apparently, the old configuration allowed two lanes straight and one lane right, and many drivers are continuing to go straight in the right lane (what used to be the middle lane) even though this is not allowed by the current signage and they are causing collisions with drivers who are in the left lane who are turning right [which is allowed, but probably not wise]. 

Again, not being from the area, I don't know how busy this right turn is.  Since it is the most direct way to I-94 from the center of town, I imagine it probably gets a lot of traffic at certain times, but it seems that the current configuration is dangerous and perhaps they should sacrifice throughput for safety and restrict the right turn to one lane. 

I found this post on Reddit that explains one driver's view:

https://www.reddit.com/r/Michigan/comments/1p0hkla/mostaccident_intersections/

I know this one! I f**** hate what they did to that intersection last year!

At this intersection, Washtenaw is a one direction road heading southeast and Hamilton is a one direction road heading south. Washtenaw used to have three lanes from Cross until Hamilton. The right lane separated from the other two at Hamilton by an island and was a right turn only lane. The middle and left lanes were intended for traffic going straight, but if you messed up and missed the right lane you could turn right after the island from the middle lane. Note how this system has no risk of lanes crossing each other.

Last year they moved the island a little, I still don't know why, making the right lane smaller. It used to be large enough for both a vehicle lane and a bike lane together, but they shrank it to the size of a sedan and made it a bike lane only. Adding the bike lane was the impetus for this, I think, but they really didn't have to get rid of the right turn lane to do so. I've never seen another cyclist use this lane, and I've only taken it once myself in all this time.

So now it's just the two lanes originally meant for traffic going straight. They decide that both lanes should be right turn lanes, with only the left lane being allowed to go straight, and did nothing to block vehicles in the right (formerly middle) lane from going straight. The curb is still in the same spot it always was. An overhead sign is the only indication of what you're supposed to do

After a s***load of collisions they started putting some traffic barrels in front of that lane to stop people from going straight, but they just kept barreling through it for months after that. Almost every day the cones would be smacked out of place then moved back, and sometimes they were saved only by the grace of God putting a moving vehicles passenger side in front of them.

The intersection was perfectly fine and didn't need any modifications to add a bike lane, nor did we need a bike lane right there. They just made it one of the most dangerous intersections in the state for no f**** reason, and I'm so glad to finally have statistics backing up my rage.

ETA an additional article reporting the list had this to say:

https://www.clickondetroit.com/news/local/2025/11/17/metro-detroit-dominates-list-of-michigans-20-most-dangerous-intersections-in-2024/

5. Hamilton Street and Washtenaw Avenue in Ypsilanti.
*   132 crashes, seven injuries.
*    This is the first year this interchange has made the list.
*    In 2023 they had a total of 12 crashes and zero injuries.

That is an extreme increase in crashes. 

[tradephoric]

According to a recent study, 4 of the 6 most crash prone intersections in Washington State are at roundabouts.  By far the most crash prone intersection in the state over the past 4 years has been the SR 204 & SR 9 Lake Stevens roundabout with 272 crashes over a 4 year period. Crashes exploded once the intersection was converted to a roundabout.


https://wellstrumbull.com/new-study-the-most-crash-prone-intersections-in-washington/

[jakeroot]

This may be of some interest to us. These improvements were completed several years ago.

...the location experienced an immediate and substantial increase in crashes in the years following the completion of the project. After reviewing the crash reports, NWR found an issue with the combination of 2-entering and 2-exiting lanes configuration on one of the roundabout legs, known as a "2x2" configuration, contributing to about 75 percent of the total increase in crashes.

...Most of these collisions were sideswipe-type crashes that were low in severity, most often only resulting in property damage; however, every collision resulted in lane closure of the circulating lane of the roundabout, resulting in long delays and queueing for the entire intersection.

This is the roundabout where SR-20 Spur meets SR-20 in Washington State, near Anacortes, in the Skagit Valley.


WA-20 Sharpes Corner Roundabout Lane Reduction by Jacob Root, on Flickr

From this PDF:

https://wsdot.wa.gov/sites/default/files/2023-12/2021-2023-Low-Cost-Enhancement-Report.pdf

[kphoger]

"The new configuration brought the safety performance of the roundabout back to the rates that the original 2017 analysis predicted."

Translation:  The 2017 analysis predictions were based on data collected primarily from roundabouts with single-lane entry, and go figure, they didn't match the reality of a roundabout with two-lane entries.

[kalvado]

"The new configuration brought the safety performance of the roundabout back to the rates that the original 2017 analysis predicted."

Translation:  The 2017 analysis predictions were based on data collected primarily from roundabouts with single-lane entry, and go figure, they didn't match the reality of a roundabout with two-lane entries.

And you can see paint gradually wearing out from 2021 (first image with eliminated lane) to 2025 (last available). I wonder how stats would go without proper periodic stripping... 

[tradephoric]

The notorious State & Ellsworth roundabout is getting a safety overhaul in an attempt to bring down the number of crashes, but it's going to remain a 2X2 roundabout.  Seems like the only long term solution to bring these crashes at 2x2 roundabouts under control is to simplify the operation by eliminate a circulating lane (like they did at the Washington roundabout Jake linked above).  Time will tell if the new striping/signage they are planning will help:

Crash-prone Ann Arbor roundabout getting safety overhaul
https://www.mlive.com/news/ann-arbor/2026/02/crash-prone-ann-arbor-roundabout-getting-safety-overhaul.html

[kalvado]

The notorious State & Ellsworth roundabout is getting a safety overhaul in an attempt to bring down the number of crashes, but it's going to remain a 2X2 roundabout.  Seems like the only long term solution to bring these crashes at 2x2 roundabouts under control is to simplify the operation by eliminate a circulating lane (like they did at the Washington roundabout Jake linked above).  Time will tell if the new striping/signage they are planning will help:

Crash-prone Ann Arbor roundabout getting safety overhaul
https://www.mlive.com/news/ann-arbor/2026/02/crash-prone-ann-arbor-roundabout-getting-safety-overhaul.html

Once upon a time, NYS DOT had a 2x3 design presented as an option...

[jakeroot]

2x3 roundabouts definitely seem like a pipe dream these days. Never mind Summerlin-style 3x3 roundabouts.

With that in mind, a privately-funded 2x3 lane roundabout is being built where WA-162 meets 128th St south of Sumner, WA. It will be Washington's first roundabout with 3 circulating lanes (the first three lane entry was WA-9 at WA-204, built a few years ago).

This project has been in the works for some time. I thought it would never get built, but I just went through the area last week, and construction is well underway (including the widening of SR-162 and widening of 128th).

https://sr162traffic.org/SR162/MCMILLIN-ROUNDABOUT/