Crash prone 'modern roundabouts'

[kalvado]

It really does boggle the mind sometimes how stuff makes it past QAQC. No one notices these things throughout the process? Or maybe they do notice them and can't be bothered to fix them. Lazy.

There was a very interesting article at some point - and the more I look the more I find it convincing:
They call it "Hollywood effect" - people are used to happy endings. It will be all right, so why escalate things, why change plans, initiate conflicts?
That was in the context of lukewarm CDC response to early covid situation; but there are too many examples I can see. People are not expecting that they will fail, so.. why bother too much? 

[jakeroot]

Florida DOT built a new roundabout at SR-972 and SW 15 Rd in Miami, so-called the "Coral Way Roundabout".

Not exactly ground-breaking, I know. The unusual part: several of the crossings are completely signalized with standard RYG signals, no RRFBs or HAWKs. Most of the signals are even post-mounted at eye-level with pedestrians and cars, which is fairly unusual for Florida, although understandable here with the I-95 overpass.

You can see everything in this YouTube video posted by FDOT:

https://youtu.be/tpUJl5s5mfk

[Rothman]

Florida DOT built a new roundabout at SR-972 and SW 15 Rd in Miami, so-called the "Coral Way Roundabout".

Not exactly ground-breaking, I know. The unusual part: several of the crossings are completely signalized with standard RYG signals, no RRFBs or HAWKs. Most of the signals are even post-mounted at eye-level with pedestrians and cars, which is fairly unusual for Florida, although understandable here with the I-95 overpass.

You can see everything in this YouTube video posted by FDOT:

https://youtu.be/tpUJl5s5mfk

Look like pelicans to me, which is good.  Wonder why they didn't go with RRFBs, though.

[jakeroot]

Look like pelicans to me, which is good.  Wonder why they didn't go with RRFBs, though.

I wondered that too, RRFBs are by far the most common "upgrade" at roundabout crossings, this roundabout seems like a shoo-in for them as much as any other. Could just be they're performing a test.

[tradephoric]

The Sprinkle Road & I-94 roundabout is crash prone.  In 2019 it was the 5th most crash prone roundabout in Michigan with 71 crashes and 2 injuries and the most crash prone roundabout outside of SE Michigan.  In 2020 total crashes went down to 33 but injuries tripled to 6 (and was still the most crash prone roundabout in the state outside of SE Michigan).

Sprinkle Road Roundabout Makes Dubious Top Ten List
https://wkfr.com/sprinkle-road-roundabout-makes-dubious-top-ten-list/

Sprinkle Road roundabout yet again the most crash prone intersection in Kalamazoo County last year, this time with 68 total crashes and 7 injury crashes. 

10 Kalamazoo County intersections with the most crashes in 2022 — a roundabout is No. 1
https://www.mlive.com/news/kalamazoo/2023/08/10-kalamazoo-county-intersections-with-the-most-crashes-in-2022-a-roundabout-is-no-1.html

[jakeroot]

Repeat after me:

Roundabouts reduce all crashes up to 47 percent.

Roundabouts reduce all crashes up to 47 percent.

Roundabouts reduce all crashes up to 47 percent.

*eye twitch*

[jakeroot]

WSDOT's new roundabout project at WA-9/WA-204 in Lake Stevens has been met with online ridicule, making the rounds all over Twitter X and Facebook.

https://twitter.com/the_transit_guy/status/1692571700045529543

https://twitter.com/KostelecPlan/status/1692581072804937743

[jeffandnicole]

WSDOT's new roundabout project at WA-9/WA-204 in Lake Stevens has been met with online ridicule, making the rounds all over Twitter X and Facebook.

https://twitter.com/the_transit_guy/status/1692571700045529543

https://twitter.com/KostelecPlan/status/1692581072804937743

When broken down to an individual intersection basis, it's not bad overall. 

It's like when someone posts an aerial shot of a spaghetti-type interchange.  Sure it may look complicated overall, but for most motorists they only need to take a single ramp that's probably signed well.

[jakeroot]

When broken down to an individual intersection basis, it's not bad overall. 

It's like when someone posts an aerial shot of a spaghetti-type interchange.  Sure it may look complicated overall, but for most motorists they only need to take a single ramp that's probably signed well.

Well, it's just roundabouts. The hate seems to be engineering-focused:

* too many slip lanes
* the frontage road on the left (of my image; east side of WA-9) is not necessary and should have been removed
* excessive chicanes on the entrance legs.

While the southbound WA-9 to westbound WA-204 slip lane is necessary because tons of cars go that direction, the other two slip lanes are just stupid and serve no real purpose. In fact, I'm almost certain they were installed because WSDOT wanted right turn lanes, but didn't want pedestrians to have to cross three lanes at once. So they separated the right turn lane from the through lanes, creating a slip lane.

Regarding the chicanes, WSDOT massively overuses chicanes. I understand their purpose (even if, in practice, they are easily ignored because the lanes are laughably wide), but they are not always necessary. In fact, in this entire complex, chicanes are really only "needed" entering the northern roundabout from the north, and entering the southern roundabout from the south. Every other approach is generally already low speed. In fairness to WSDOT here, though, I think only the entrances from WA-9 have chicanes; the image suggests other roundabout entrance are more straight-on entry.

[jamess]

Sure it may look complicated overall, but for most motorists they only need to take a single ramp that's probably signed well.

And for people navigating this outside a motor vehicle?

[tradephoric]

I don't know how true this is (maybe there's a cross walk just off frame) but i liked this picture highlighting how convenient it is for pedestrians to cross the street.

[jakeroot]

Extremely misleading. WA-9 has no pedestrian facilities along it. The ghost roundabout in the picture below is the roundabout in the above photo:


WA-9 Lake Stevens Looking South(east) by Jacob Root, on Flickr

[Occidental Tourist]

Looking at the original configuration, this seems like a solution searching for a problem.

[jamess]

Extremely misleading. WA-9 has no pedestrian facilities along it. The ghost roundabout in the picture below is the roundabout in the above photo:

While it is certainly an improvement for pedestrians (some accommodations, versus previously none), that doesnt mean its a GOOD design for pedestrians.

[tradephoric]

The Michigan Department of Transportation performed a study evaluating the performance and safety effectiveness of roundabouts throughout the state.  The 8 triple lane roundabouts studied saw a big increase in total crashes, a slight increase in injury crashes, and a reduction in KA crashes.


https://mdotjboss.state.mi.us/TSSD/tssdResearchAdminDetails.htm?keyword=SPR-1725

[kphoger]

The Michigan Department of Transportation performed a study evaluating the performance and safety effectiveness of roundabouts throughout the state.  The 8 triple lane roundabouts studied saw a big increase in total crashes, a slight increase in injury crashes, and a reduction in KA crashes.


https://mdotjboss.state.mi.us/TSSD/tssdResearchAdminDetails.htm?keyword=SPR-1725

Thanks for the link!  The "Spotlight" document had a nice section called "RESULTS".  Here are some takeaways from the study that they report in that section:

— Crashes occur more often at roundabouts than at traditional intersections.
— Crashes at roundabouts are less likely to result in severe injuries or deaths.

— Roundabouts were found to reduce traffic delays by more than 63 percent on average
— Estimated fuel savings were more than $69 per vehicle per year
— Converting an existing intersection to a roundabout generally results in benefits six times greater than the costs.

— Drivers accepted smaller gaps at...
    * roundabouts with more than one lane
    * three-legged roundabouts
    * those located in rural areas.

— Roundabouts on interchanges, where speeds tend to be higher, had the lowest yielding rates.
— Roundabouts with pedestrian hybrid beacons produced higher yield rates.

[kalvado]

— Estimated fuel savings were more than $69 per vehicle per year

My bullshitmeter broke on this.

[Rothman]

— Estimated fuel savings were more than $69 per vehicle per year

My bullshitmeter broke on this.

Reminds me of economic benefit estimates of converting freeways to meet Interstate Highway System standards.

[kalvado]

— Estimated fuel savings were more than $69 per vehicle per year

My bullshitmeter broke on this.

Reminds me of economic benefit estimates of converting freeways to meet Interstate Highway System standards.

There are good reasons why scientific community switched to an independent peer review for publications.
There are some quite real facepalms in the report.

[kphoger]

— Estimated fuel savings were more than $69 per vehicle per year

My bullshitmeter broke on this.

Why?  Doing some back-of-the-envelope math here...

Assuming 12,000 miles driven per year...
Assuming fuel economy of 25 miles per gallon...
Makes 480 gallons of gas purchased per year...
Assuming $3.50 per gallon...
Makes $1680 spent on gas per year.

A savings of $69 per year...
Makes $1611 spent on gas per year...
Assuming $3.50 per gallon...
Makes 460.286 gallons of gas purchased per year...
Assuming 12,000 miles driven per year...
Makes 26.071 miles per gallon.

You don't think that eliminating a stoplight could result in a driver's fuel economy being improved by 1.071 mpg?
An improvement of 4.3% is unbelievable?

Maybe, maybe not.  If that stoplight were on my regular daily commute, I could imagine a savings like that.

Or did I do some bad math somewhere in there?  Math corrected.

[7/8]

— Estimated fuel savings were more than $69 per vehicle per year

My bullshitmeter broke on this.

Why?  Doing some back-of-the-envelope math here...

Assuming 12,000 miles driven per year...
Assuming fuel economy of 25 miles per gallon...
Makes 480 gallons of gas purchased per year...
Assuming $3.50 per gallon...
Makes $1680 spent on gas per year.

A savings of $69 per year...
Makes $1611 spent on gas per year...
Assuming $3.50 per gallon...
Makes 460.286 gallons of gas purchased per year...
Assuming 12,000 miles driven per year...
Makes 24.985 miles per gallon.

You don't think that eliminating a stoplight could result in a driver's fuel economy being improved by 0.015 mpg?
An improvement of 0.06% is unbelievable?
Why?

Or did I do some bad math somewhere in there?

I think something went wrong at the end with your math: 12 000 miles / 460.286 gallons = 26.07 miles per gallon (improvement of 1.07 mpg)

[kphoger]

I think something went wrong at the end with your math: 12 000 miles / 460.286 gallons = 26.07 miles per gallon (improvement of 1.07 mpg)

Fixed.  Thank you.

[tradephoric]

The crash severity distribution before and after roundabout chart really caught my eye.

One of the primary safety benefits of roundabouts is that they tend to reduce crash severities due to lower speeds at which drivers are forced to enter the intersection and traffic flowing around a central circle in only one direction. As such, the crash severity distribution before and after roundabout construction was also investigated.

Take these two intersections:

Intersection A:  10 injury crashes, 30 total crashes
Intersection B:  10 injury crashes, 100 total crashes

It's not enough to say that the percentage of injury crashes at intersection B is lower so it must be safer.  Yes, roundabouts reduce crash severity but there's just so many more crashes occurring at these complex roundabouts that the actual number of injuries is roughly the same (as seen in the triple-lane roundabouts analyzed in the study which actually had more injury accidents than the before condition). 

[kphoger]

It's not enough to say that the percentage of injury crashes at intersection B is lower so it must be safer.  Yes, roundabouts reduce crash severity but there's just so many more crashes occurring at these complex roundabouts that the actual number of injuries is roughly the same (as seen in the triple-lane roundabouts analyzed in the study which actually had more injury accidents than the before condition). 

You know, considering how much you hate it when people use single-lane roundabouts as a stand-in for all roundabouts when it comes to safety data, I'd have thought you would avoid using triple-lane roundabouts as a stand-in for all roundabouts.

[kalvado]

It's not enough to say that the percentage of injury crashes at intersection B is lower so it must be safer.  Yes, roundabouts reduce crash severity but there's just so many more crashes occurring at these complex roundabouts that the actual number of injuries is roughly the same (as seen in the triple-lane roundabouts analyzed in the study which actually had more injury accidents than the before condition). 

You know, considering how much you hate it when people use single-lane roundabouts as a stand-in for all roundabouts when it comes to safety data, I'd have thought you would avoid using triple-lane roundabouts as a stand-in for all roundabouts.

It's just a strike against the quality of the report. And their normalization is borderline fraud. I would certainly say "major edits" as a reviewer if facing something like that.