Crash prone 'modern roundabouts'

[jakeroot]

^^^
The AADT numbers would include the right turn counts via the slip lanes.

Makes sense. I'd like to see the safety numbers for a roundabout where all the right turn slip lanes are protected (followed by a merge or something).

Is it possible that the separation of the right turn lane from the straight/left lanes may have improved sightlines? Nevermind the slip lane traffic going from north to northwest (at the Valley View/CR-M roundabout outside of Madison, WI) that don't conflict with the circle at all.

[tradephoric]

Makes sense. I'd like to see the safety numbers for a roundabout where all the right turn slip lanes are protected (followed by a merge or something).

The Rte. 101/Winchester Street roundabout in Keene has protected right turn slip lanes for all approaches.   There was a head on crash near the roundabout about a month ago that injured 2 people.

Two taken to hospital after head-on crash near Keene roundabout
http://www.sentinelsource.com/news/local/two-taken-to-hospital-after-head-on-crash-near-keene/article_1130b673-283f-5724-88b8-93108b6eeb97.html

Someone apparently caught the crash on dashcam... 
https://www.youtube.com/watch?v=r1YQupa9jmo

[jakeroot]

Makes sense. I'd like to see the safety numbers for a roundabout where all the right turn slip lanes are protected (followed by a merge or something).

The Rte. 101/Winchester Street roundabout in Keene has protected right turn slip lanes for all approaches.   There was a head on crash near the roundabout about a month ago that injured 2 people.

Ooooookay. So maybe slip lanes don't protect against drifting after you leave a roundabout, but maybe they help prevent right turn crashes, where somebody turning right fails to give way, or maybe where their visibility wasn't good, so they just went and hoped for the best?

[tradephoric]

Here is an example of a multi-lane roundabout in Milton Keynes, UK. 

https://www.google.com/maps/@52.0416474,-0.7445147,95m/data=!3m1!1e3

This is the type of complex roundabout that seems so problematic for American drivers.  There are literally dozens more roundabouts just like this in Milton Keynes and many have minimal signage/pavement markings to direct traffic through the roundabout.  Truck aprons are nearly non-existent and there is no overhead signs to direct traffic what lane to be in when navigating the roundabout.  Here is an example of a roundabout where there are no visible pavement markings in the circle at all.

https://www.google.com/maps/@52.0443739,-0.7637102,95m/data=!3m1!1e3

I'm not suggesting that roundabouts with minimal pavement markings and directional signs are safer than roundabouts without them.  It just seems like the UK isn't hung up on every little design element.  It's a circle, and drivers circulate through it the best they can without hitting another vehicle.  So the question becomes how many crashes are occurring at these complex Milton Keynes roundabouts and what are the daily traffic volumes?  Do the crash rates of these UK roundabouts compare to the complex roundabouts found in America? 

[english si]

I'm not suggesting that roundabouts with minimal pavement markings and directional signs are safer than roundabouts without them.  It just seems like the UK isn't hung up on every little design element.  It's a circle, and drivers circulate through it the best they can without hitting another vehicle.

Yes - this is what I've been banging on about. The problem is that America is very prescriptive - do this, do that. Whereas the UK puts more onus on the driver, only guiding them and telling them not to do stuff (though we're changing to a more nannying principle and our crash rate improvements has flattened out).

So the question becomes how many crashes are occurring at these complex Milton Keynes roundabouts and what are the daily traffic volumes?  Do the crash rates of these UK roundabouts compare to the complex roundabouts found in America?

I think upthread I did one.

Brinklow Roundabout is a 3-lane roundabout with 70mph dual carriageway arms carrying traffic volumes (2016 figures taken from nearby count points) as follows
A421W: 25941
A421E: 28760
A4146N: 30485
A4146S: 20516
which, as everyone will use 2 legs and be counted twice, giving an average traffic on the circulatory carriageway of 52851/day (2004 figures of 23840+19921+30449+18762/2 = 46486)

I can't find any RTC data, but in 2002, they reduced visibility on the approaches to increase safety and it worked.

A re-engineered junction on Barnsdale Drive and Tattenhoe, a gap closure on Avebury/Elder Gate, removal of a right hand turn from Grafton Street into Walgrave Drive and installing of visibility barriers on approach to Brinklow roundabout have so far resulted in no serious injuries or fatalities and only 40 slight injuries. Over the three years prior to implementation between 2000 and 2002, there were 11 serious and 96 slight injuries, indicating that in total these schemes have successfully reduced casualties.

Lets say that all those 40 slight injuries happened in 2004, rather than over the three-year 2003-05 period (to really tilt the table against MK), and at that roundabout, rather than also at the other junctions. That gives 17013876 vehicles passing and 40 injury crashes - an injury crash every 425347 vehicle entries is a rate of 2.35MEV.

Edit: I've found a not that useful way of finding it: http://www.crashmap.co.uk/search This covers all crashes. On the roundabout and it's approaches (where most rtas are clustered (we'll go to the bus stops on each approach), there are 51 recorded incidents, but this covers the 5 year period from 01/01/12 to 31/12/16. All but 1 are slight, though no damage only incidents are included (as seems to be the case with UK statistics).

Even putting that whole 5 years of injury crashes into 2016, that's 2.63MEV.

[tradephoric]

Edit: I've found a not that useful way of finding it: http://www.crashmap.co.uk/search This covers all crashes. On the roundabout and it's approaches (where most rtas are clustered (we'll go to the bus stops on each approach), there are 51 recorded incidents, but this covers the 5 year period from 01/01/12 to 31/12/16. All but 1 are slight, though no damage only incidents are included (as seems to be the case with UK statistics).

That link is incredibly useful!  As you mentioned the data doesn't appear to include damage only incidents.  This is confirmed when reading about the data on the website:

CrashMap uses data collected by the police about road traffic crashes occurring on British roads where someone is injured which is then compiled in to an easy to use format showing each incident on a map. This data is approved by the National Statistics Authority and reported on by the Department for Transport each year. Northern Ireland data is not provided proactively and has been obtained through an FoI request. Incidents are plotted to within 10 metres of their location and as such, can sometimees appear to be off the carriageway when zoomed in very closely.

I zoomed into one of the Milton Keynes roundabouts I linked in my above post to see how many injury crashes there were over the past 5 years:
https://www.google.com/maps/@52.0416474,-0.7445147,95m/data=!3m1!1e3

The Childs Way / Marlborough St roundabout had 15 injury crashes over a 5 year period (14 slight, 1 serious).  Now do you know of a good resource to find traffic volumes on British roadways?  Then we can nail down injury crash rates for these British roundabouts.

[ScottRAB]

Many people confuse other and older styles of circular intersections with modern roundabouts. East coast rotaries, large multi-lane traffic circles (Arc D'Triomphe, Dupont Circle), and small neighborhood traffic circles are not modern roundabouts. If you want to see the difference between a traffic circle, a rotary (UK traffic roundabout) and a modern roundabout (UK continental roundabout).
Go to  http://www.k-state.edu/roundabouts/photos.htm to see pictures. 
The Brits even call a merry-go-round a kid's roundabout.

The US and UK introduced circular intersections in the early 20th century.  The US and UK adopted widespread use of rotaries in the 40's and 50's and while both countries found them to be less than ideal, the US walked away from them while the UK kept on tinkering. The offside priority rule (yield on entry) and smaller size with deflection on entry are the key operational and design changes developed by the British. The French and Aussies have applied them more than the US. We're essentially importing the refined, safer grandchild of the east coast rotary, thus the preferred name modern roundabout. Look up Frank Blackmore.

Roundabout History
Frank Blackmore:  https://en.wikipedia.org/wiki/Frank_Blackmore
https://www.theguardian.com/theguardian/2008/jun/21/6
http://www.mini-roundabout.com/tribute.htm
https://supernet.isenberg.umass.edu/visuals/FOMgt341-F10/Rotaries%20vs%20Roundabouts.pdf
http://rodel-interactive.com/about/capacity.html
http://www.economist.com/news/europe/21697235-invented-britain-modern-traffic-circles-invade-frances-hexagon-french-revolution

[english si]

Now do you know of a good resource to find traffic volumes on British roadways?  Then we can nail down injury crash rates for these British roundabouts.

If the arms are A roads, then http://www.dft.gov.uk/traffic-counts/, otherwise there's typically only stuff for a specific study if there is one.

[cjw2001]

A little "red meat" for the Carmel roundabout haters...  Injury accidents continue to decline in Carmel despite population growth

[kalvado]

A little "red meat" for the Carmel roundabout haters...  Injury accidents continue to decline in Carmel despite population growth

Glass can be half-full or half-empty.
Lets try flip it around,... Total number of injury incidents in Carmel is flat over past 20 years while US saw 30% drop! Roundabouts INURE people!
Proper analysis is often more involved. They gamble on population growth over the period - but what does it tell about traffic? Not much. How many transit vehicles are there for those just going through the town? Is it possible that drivers literally go extra mile not to struggle with roundabouts? Any new highways so traffic avoids intersections?
Of course, that is too complicated for most traffic engineers...

[tradephoric]

Here is a link to the 2016 Carmel Police Department Annual report so you can analyze the data for yourself: 

http://carmel.in.gov/Modules/ShowDocument.aspx?documentID=8375

In previous years the Carmel Police Department Annual Repots would provide a map of the highest crash intersections in the city.  Starting in 2015 they omitted this map, and readers can no longer determine what intersections in Carmel are experiencing the most crashes.  If anybody has another resource to track crashes at Carmel intersections, that would be useful info.

Any new highways so traffic avoids intersections?

That's a good point.  Over the past decade Carmel has converted heavily traveled surface streets (Keystone Parkway and Meridian Street) to grade-separated highways.  A lot of Carmel drivers bypass the major intersections that they once had to travel through.  It's hard to get t-boned on a highway.  Brainard attributes the decrease in the accident rate to the city's investment in roundabouts, but it could be due to the major surface streets in the city being converted to grade-separated highways.

[UCFKnights]

I was in Gainesville, Florida recently, and as part of the new development and bridge over I-75, they put in a really weird two lane roundabout, that seems like it will be very accident prone once it gets any traffic. One leg exits into another roundabout, one leg to a stop sign about 10 feet forward of the exit, and one leg comes in from the 2 lane bridge. The signage is also wrong on the bridge approach indicating what each lane does, and even though its a two lane roundabout, the bridge leg is the only one that is 2 lanes.

No pictures on google maps yet, but especially considering they had a completely fresh slate on both sides of the bridge with all empty lane, and all new roads, its hard to envision why anyone would design it like this.

I still stand by my opinion of being a fan of single lane roundabouts (especially to replace any intersection controlled by a stop sign), but strongly against multilane roundabouts as there seems to be just about no way to get Americans to understand the lane use in them, making crashes inevitable.

[tradephoric]

Carmel awards $28.8M contract for 96th and Keystone roundabout
https://www.ibj.com/articles/64656-carmel-awards-288m-contract-for-96th-and-keystone-roundabout

The headline doesn't mention that 96th and Keystone is being converted from a standard intersection to a full blown grade-separated interchange.  They are so roundabout obsessed in Carmel that the headline focuses on the on/off ramp roundabouts and make no mention the grade-separated interchange.   The roundabouts being proposed at 96th and Keystone have a similar design to the existing roundabouts at 116th and Keystone (which has one of the highest crash rates in Carmel with a crash rate over 5.0 MEV).

[jeffandnicole]

Carmel awards $28.8M contract for 96th and Keystone roundabout
https://www.ibj.com/articles/64656-carmel-awards-288m-contract-for-96th-and-keystone-roundabout

They are so roundabout obsessed in Carmel that the headline focuses on the on/off ramp roundabouts and make no mention the grade-separated interchange.

Well, except in the very first sentence.  And in the graphic below the very first sentence.

And I think there's someone much more roundabout obsessed than this town or newspaper.

[tradephoric]

Carmel awards $28.8M contract for 96th and Keystone roundabout
https://www.ibj.com/articles/64656-carmel-awards-288m-contract-for-96th-and-keystone-roundabout

They are so roundabout obsessed in Carmel that the headline focuses on the on/off ramp roundabouts and make no mention the grade-separated interchange.

Well, except in the very first sentence.  And in the graphic below the very first sentence.

And I think there's someone much more roundabout obsessed than this town or newspaper.

Yeah, but it's not in the headline. A lot of people will read a headline and nothing else.  They are so roundabout obsessed that a major $28.8 million dollar interchange project is viewed as a "roundabout" project.  Yeah, it's the "roundabouts" that are improving traffic flow on Keystone Parkway (nothing to do with the grade-separation right?).  Also it's very likely there will be more crashes at the interchange roundabouts than the surface intersection they are replacing (just like there were when 116th & Keystone was converted to a grade-separated interchange).  But somehow it will be viewed as a success because there are bunch of ideologues running that city who believe roundabouts are always the best option... to the point where the mayor of Carmel is proposing every traffic signal in the city be converted to a roundabout.  The mayor is obsessed.

[jakeroot]

The rest of Keystone is a freeway. If it's locals that are reading the story, I think they'll known straight-away that it's going to be an interchange.

But, in the event that maybe they don't...

roundabout interchange

construction of the roundabout interchange

traffic on Keystone will travel over 96th Street

The intersection is the only one along the Keystone corridor in Carmel that hasn't been upgraded to an elevated roundabout

[tradephoric]

The rest of Keystone is a freeway. If it's locals that are reading the story, I think they'll known straight-away that it's going to be an interchange.

But, in the event that maybe they don't...

roundabout interchange

construction of the roundabout interchange

traffic on Keystone will travel over 96th Street

The intersection is the only one along the Keystone corridor in Carmel that hasn't been upgraded to an elevated roundabout

Sounds like Fake News Jake.  CNN did some propaganda piece on Carmel's roundabouts...

CNN: Very Fake News

https://www.youtube.com/watch?v=WaICdKez2jg

https://www.youtube.com/watch?v=X-Mkjee9XBk

[jakeroot]

[tradephoric]

Why an Indiana City is Totally Obsessed with Roundabouts:  When is a circle better than an X?
https://www.inverse.com/article/34337-carmel-indiana-might-forever-be-america-s-roundabout-kingdom

Circles and Cyclists May Not Mix

It was safety stats like these that allowed modern traffic circles to hop the pond and find a home in cities like Carmel. But in recent years, many English cities have been paving over their roundabouts, in part because of the damage this design seems to pose to cyclists.

While the statistics about driver safety may still ring true, a 2008 study in the journal Accident Analysis & Prevention found that turning a traffic signal into a roundabout actually increased a cyclist's risk of injury by 27 percent. Reduced speeds can reduce damage, but even helmet-wearing cyclists aren't totally protected from the full force of a car going 25 miles an hour. This study isn't the last word, of course, and many cities continue to report improved safety for cyclists in roundabouts over traditional intersections, but this and other concerning data has been enough to spur some urban planners to reconsider.

Other research, like the fact that there isn't a documented 2x2 roundabout in America with a crash rate below 1.0 MEV.  Every complex geometry roundabout where crash data is available has an unacceptably high crash rate.  It's quite amazing that there isn't even one outlier, where the crash rate could be viewed as acceptable.

Christine Scales, a city-county councillor representing neighboring Indianapolis, which shares more than a few roads with Carmel, tells Inverse that some intersections are just better without a roundabout.

"I have no opposition to roundabouts when their location is considered in a judicious manner,"  Scales says. And yet she opposes Carmel's mayor in his attempted expansion of the roundabout program. "I believe he has convinced himself of the safety of roundabouts, as well as their benefit of enhancing traffic flow,"  she says. "[But] because he does not appear to evaluate each intersection as to the cost-benefit of replacing a traditional intersection, he has run into some problems."

[tradephoric]

Listen to the first thing Mayor James Brainard said relating to roundabouts in that CNN piece:  "Roundabouts work everywhere" .  Luckily not everyone is as indoctrinated as Mayor Brainard.  Arizona State University found that double lane roundabouts in their state saw a 62% increase in total accidents, a 60% increase in damages, and only a 16% drop in injuries. 

Link to Arizona State University study:
https://repository.asu.edu/attachments/170314/content/Souliman_asu_0010N_15713.pdf

ADOT may replace roundabouts with diverging-diamond interchange design
http://www.azcentral.com/story/news/local/phoenix-traffic/2017/07/19/adot-may-replace-roundabouts-diverging-diamond-design-interchange/490345001/

[tradephoric]

Council, residents speak against roundabout plans
http://www.ricentral.com/nk_standard_times/news/local_news/council-residents-speak-against-roundabout-plans/article_a7042b7a-6d6c-11e7-a959-2b0b9a38eba6.html

So this roundabout is being opposed by residents and city counsel, but listen to the outlandish claim made back in 2012 about the safety of roundabouts by someone from RIDOT.

RIDOT's Robert Rocchio also said in 2012 that the roundabout was being envisioned as the town prepared for the Rolling Greens development.

"Whether it occurs or doesn't occur, we want to make sure our improvements could accommodate that,"  he said in 2012. "Roundabouts are much safer than signals, it is proven. They reduce up to 90 percent of crashes."  

No Robert Rocchio there is not a 90% reduction in crashes at roundabouts.  And it hasn't been proven that there is a 90% reduction in fatalities (if that is what you indeed meant to say).  If you actually read the 2000 IIHS study that made the claim that roundabouts reduce fatalities by 90%, they basically admit that it's a fabricated number...

Effects on fatal crashes and those causing incapacitating injuries are more difficult to measure due to the small samples, but indications are that such crashes were substantially reduced. For the 20 converted intersections with injury data, there were 3 fatal crashes during the before period and none during the after period. The fatal crashes may have contributed to the fact that the roundabouts were constructed and may therefore contribute to the regression-to-the-mean phenomenon.

[tradephoric]

Controversy revolving around Shawnee Roundabout
http://www.hometownstations.com/story/35968348/controversy-revolving-around-shawnee-roundabout

In the 23 months prior to construction beginning at Shawnee and Ft. Amanda Road, 27 vehicle accidents occurred at the location. Since the completion of the roundabout, 61 vehicle accidents took place.

Engineer's comment:

"It's moving traffic very efficiently. There's little to no back-ups," states Rhodes. "Because of that, the people in the area that use it on a daily basis report to me that they love it."

Police Chief's comment:

It is a burden on our manpower and resources. There's no question about it. Nobody working here is really happy about that," says Shawnee Township Police Chief Mike Keith. "For one, for the expenses and costs of people involved in accidents. Two, for the manpower and resources we direct toward that."

"We suggested one lane. A lot of our accidents are people changing lanes in the round about, which is not permitted. Doesn't stop the accident from occurring. And trucks and buses can't really stay in one lane making that shoulder curve,"  states Chief Keith.

[jakeroot]

How often do you send your data to engineers?

[kalvado]

ANother small non-injury accident on a roundabout: truck with hot tar rolled over on one of the roundabots in Malta - the road in question has a chain of 7.
Previously those circles made to the top of Trade's list of bad guys, and one of them made it to the list of 20 most dangerous intersections in the area as published by local insurance company. But that all is a small price to pay for your safety!
http://cbs6albany.com/news/local/traffic-alert-tanker-rollover-at-exit-12

[hm insulators]

That's one way to resurface a roadway!