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Crash prone 'modern roundabouts'

Started by tradephoric, May 18, 2015, 02:51:37 PM

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Mr_Northside

Quote from: MNHighwayMan on April 13, 2018, 11:58:40 AM
Quote from: kalvado on April 13, 2018, 11:24:42 AM
Posting statistics makes sense; somewhat special accidents (like manure truck  :awesomeface:) make some sense.

It took shitting on roundabouts to a whole new, literal level. :bigass: :awesomeface:

I don't have opinions anymore. All I know is that no one is better than anyone else, and everyone is the best at everything


jakeroot

Quote from: Mr_Northside on April 13, 2018, 03:48:18 PM
Quote from: MNHighwayMan on April 13, 2018, 11:58:40 AM
Quote from: kalvado on April 13, 2018, 11:24:42 AM
Posting statistics makes sense; somewhat special accidents (like manure truck  :awesomeface:) make some sense.

It took shitting on roundabouts to a whole new, literal level. :bigass: :awesomeface:



The facebook comments on the crash were full of BTTF references. Hell, I'm pretty sure that's the only reason it's funny.

tradephoric

Quote from: kalvado on April 13, 2018, 11:24:42 AM
Quote from: tradephoric on April 13, 2018, 10:04:48 AM
A motorcyclist was killed in Lawrence, Indiana early today after failing to negotiate a roundabout.

Motorcyclist killed in roadway roundabout traffic accident
http://fox59.com/2018/04/13/motorcyclist-killed-in-east-side-roundabout-traffic-accident/
Seriously, this is just one of 100 fatal accidents which happened yesterday.
Posting statistics makes sense; somewhat special accidents (like manure truck  :awesomeface:) make some sense. Routine crashes... we know that they happen..

Another fatal motorcycle crash at a Delaware roundabout just two days after the Lawrence, Indiana fatality.  I wouldn't say fatal crashes at intersections are routine.  According to the FHWA there were 2,924 fatal crashes at roughly 300,000 signalized intersections in 2007.  If you believe those FHWA's stats, traffic signals average a fatal crash about every 100 years.  Here's the Delaware news story...

Motorcyclist killed in roundabout near Bear
https://www.delawareonline.com/story/news/crime/2018/04/15/motorcyclist-killed-roundabout-near-bear/518767002/

Now we are told that roundabouts reduce fatalities by 90%.  Believing those stats, if all 300,000 traffic signals in America were converted to roundabouts, we would see about 300 deaths per year (as opposed to 3000 deaths if they remained signalized intersections).   If that's the case, a roundabout would average a fatal crash about every 1,000 years.  The Delaware roundabout where the fatal motorcyclist crash occurred was constructed last year.  Do we expect not to see another fatal crash at this roundabout for the next 999 years?  The IIHS claim that roundabouts reduce fatalities by 90% is a fabrication.  While i do believe roundabouts reduce fatalities overall compared to signalized intersections, i don't think it's anywhere near the 90% the IIHS has claimed.

kalvado

Quote from: tradephoric on April 16, 2018, 03:18:45 PM
Quote from: kalvado on April 13, 2018, 11:24:42 AM
Quote from: tradephoric on April 13, 2018, 10:04:48 AM
A motorcyclist was killed in Lawrence, Indiana early today after failing to negotiate a roundabout.

Motorcyclist killed in roadway roundabout traffic accident
http://fox59.com/2018/04/13/motorcyclist-killed-in-east-side-roundabout-traffic-accident/
Seriously, this is just one of 100 fatal accidents which happened yesterday.
Posting statistics makes sense; somewhat special accidents (like manure truck  :awesomeface:) make some sense. Routine crashes... we know that they happen..

Another fatal motorcycle crash at a Delaware roundabout just two days after the Lawrence, Indiana fatality.  I wouldn't say fatal crashes at intersections are routine.  According to the FHWA there were 2,924 fatal crashes at roughly 300,000 signalized intersections in 2007.  If you believe those FHWA's stats, traffic signals average a fatal crash about every 100 years.  Here's the Delaware news story...

Motorcyclist killed in roundabout near Bear
https://www.delawareonline.com/story/news/crime/2018/04/15/motorcyclist-killed-roundabout-near-bear/518767002/

Now we are told that roundabouts reduce fatalities by 90%.  Believing those stats, if all 300,000 traffic signals in America were converted to roundabouts, we would see about 300 deaths per year (as opposed to 3000 deaths if they remained signalized intersections).   If that's the case, a roundabout would average a fatal crash about every 1,000 years.  The Delaware roundabout where the fatal motorcyclist crash occurred was constructed last year.  Do we expect not to see another fatal crash at this roundabout for the next 999 years?  The IIHS claim that roundabouts reduce fatalities by 90% is a fabrication.  While i do believe roundabouts reduce fatalities overall compared to signalized intersections, i don't think it's anywhere near the 90% the IIHS has claimed.
To properly answer your question, a total number of roundabouts in US would be useful. It is always about numbers - and properly dealing with them.


tradephoric

In a previous post, I attempted to estimate the number of fatal crashes per roundabout in the US for 2017.  My estimate came to 0.0033 fatalities per roundabout.  This is comparable to FHWA published data for the number of fatalities per roundabout in the U.S. between 2005 and 2013.  Keep in mind the IIHS made the claim that roundabouts reduce fatal crash by 90% way back in 2000.  There is a lot more data available today to sift through that proves the IIHS claim back then was wrong.  You just aren't seeing 90% reductions in fatalities at roundabouts in America.

Quote from: tradephoric on January 05, 2018, 12:05:48 PM
News reports for fatal roundabout crashes that occurred in 2017. 

http://www.sun-sentinel.com/local/broward/fl-boca-man-dies-in-parkland-crash-20170117-story.html
http://www.theledger.com/news/20170208/teen-faces-manslaughter-charge-after-girl-dies-in-crash-following-chase-with-lpd-officer
http://www.wdbj7.com/content/news/60-year-old-Roanoke-County-woman-dies-in-motorcycle-crash-413537653.html
http://www.fox9.com/news/unbelted-man-dies-in-chisago-county-crash-friday-afternoon
http://www.wcsh6.com/news/local/fatal-crash-closes-rte-114-bypass-in-gorham/433810393
http://www.toledoblade.com/Police-Fire/2017/04/30/Alcohol-believed-to-be-factor-in-fatal-Springfield-Twp-crash.html
http://www.gainesville.com/news/20170502/roundabout-crash-kills-two-police-say
http://www.bellinghamherald.com/news/local/article153269789.html
http://www.cecildaily.com/police_and_fire_beat/article_bed6099c-45a6-5be5-b61d-ec91d893631b.html
http://www.wpta21.com/story/35827071/coroner-identifies-motorcyclist-involved-in-thursday-morning-fatal-crash
http://www.prescottenews.com/index.php/news/current-news/item/30613-37-year-old-man-from-page-dies-in-crash-at-roundabout
http://www.startribune.com/driver-in-st-cloud-roundabout-fatally-hits-pedestrian/453113583/
http://www.lasvegasnow.com/news/one-killed-in-overnight-crash/859083995

This was based on about an hour of google searches and based on this limited research, there were at least 13 fatal roundabouts crashes in 2017 resulting in 14 fatalities.   According to the latest 2013 FHWA estimates, there are roughly 3200 roundabouts in the United States.  I personally have compiled a database of over 5200 roundabouts in America, but I don't know the exact methodology used to compile the FHWA database.  Let's split the difference and say there are about 4200 roundabouts in America.   In 2017 each modern roundabout averaged 0.0033 fatal crashes (14 fatalities / 4200 roundabouts).  This ratio is comparable to previous years based on data compiled by the FHWA:

https://safety.fhwa.dot.gov/intersection/innovative/roundabouts/docs/fhwasa15072.pdf

So how does this ratio compare to signalized intersections?  Based on FHWA data there were 2,924 fatalities at approximately 311,000 signalized intersections in 2007.  Each signal averaged 0.0094 fatal crashes (2,924 fatalities / 311,000 signals). 
https://safety.fhwa.dot.gov/intersection/other_topics/fhwasa10005/brief_2.cfm

Now we can use these ratios to get a sense of how much roundabouts are reducing fatal crashes.  Is it really 90% as the IIHS claims?  To me it looks to be closer to 65% (1-(0.0033/0.0094)).  That's still a big reduction, but it's not 90%.  And consider that the IIHS claims that roundabouts reduce injury crashes by 76%.  However, Minnesota research found that complex roundabouts in that state actually saw a 6% increase in injury crashes.  The point is there is potentially a subset of modern roundabouts that are increasing fatal crashes, not reducing them.  I'll tell you one subset of roundabouts that are potentially increasing fatal crashes... roundabouts that have retaining walls in the central island.  Do you think it's a coincidence there have been 3 fatalities in the past 10 years at the 96th and Westfield Blvd roundabout in Carmel?  Every time a driver misjudges the roundabout and drive through the middle of it, they smack into a concrete wall.  Boom!  Dead!

DaBigE

To continue to say the IIHS data is wrong is disingenuous. The data is outdated, as just about anyone here can agree. It was accurate at the time it was published, given the data available. Can we quit beating this dead horse already? It'd be like Toyota continuing to advertise having the 2000 Truck of the Year.
"We gotta find this road, it's like Bob's road!" - Rabbit, Twister

MNHighwayMan

Quote from: DaBigE on April 16, 2018, 04:56:35 PM
To continue to say the IIHS data is wrong is disingenuous. The data is outdated, as just about anyone here can agree. It was accurate at the time it was published, given the data available. Can we quit beating this dead horse already? It'd be like Toyota continuing to advertise having the 2000 Truck of the Year.

As long as this thread remains not locked, the dead horse beating will continue.

jakeroot

Quote from: MNHighwayMan on April 16, 2018, 06:01:59 PM
Quote from: DaBigE on April 16, 2018, 04:56:35 PM
To continue to say the IIHS data is wrong is disingenuous. The data is outdated, as just about anyone here can agree. It was accurate at the time it was published, given the data available. Can we quit beating this dead horse already? It'd be like Toyota continuing to advertise having the 2000 Truck of the Year.

As long as this thread remains not locked, the dead horse beating will continue.

I don't think locking this thread would be smart. It's become a dumping ground for roundabout news, and any other roundabout threads would almost certainly become a discussion on safety anyways.

MNHighwayMan

Quote from: jakeroot on April 17, 2018, 02:45:02 AM
Quote from: MNHighwayMan on April 16, 2018, 06:01:59 PM
Quote from: DaBigE on April 16, 2018, 04:56:35 PM
To continue to say the IIHS data is wrong is disingenuous. The data is outdated, as just about anyone here can agree. It was accurate at the time it was published, given the data available. Can we quit beating this dead horse already? It'd be like Toyota continuing to advertise having the 2000 Truck of the Year.
As long as this thread remains not locked, the dead horse beating will continue.
I don't think locking this thread would be smart. It's become a dumping ground for roundabout news, and any other roundabout threads would almost certainly become a discussion on safety anyways.

Right, and I actually agree, for the reasons you stated. All I'm saying is that this thread will always have a component of deceased equine assault in and among the news and actually useful discussion.

tradephoric

Quote from: DaBigE on April 16, 2018, 04:56:35 PM
To continue to say the IIHS data is wrong is disingenuous. The data is outdated, as just about anyone here can agree. It was accurate at the time it was published, given the data available. Can we quit beating this dead horse already? It'd be like Toyota continuing to advertise having the 2000 Truck of the Year.

The IIHS study was never accurate, even at the time of publication.  When nearly half of the multi-lane roundabouts analyzed in the study didn't even have before injury crash data, how can it be taken seriously?  The few remaining multi-lane roundabouts with before injury crash data were along a 25 mph roadway through a ski-resort in Colorado.  It's a joke.  Of course that hasn't stopped agencies from citing the safety statistics found in that IIHS study to gain public support for roundabouts.  Anytime you hear that roundabouts reduce fatalities by 90%, just know you are being lied to.   The study basically admits that the 90% reduction in fatalities number is a WAG...  a Wild Ass Guess.

QuoteEffects 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.

DaBigE

Quote from: jakeroot on April 17, 2018, 02:45:02 AM
Quote from: MNHighwayMan on April 16, 2018, 06:01:59 PM
Quote from: DaBigE on April 16, 2018, 04:56:35 PM
To continue to say the IIHS data is wrong is disingenuous. The data is outdated, as just about anyone here can agree. It was accurate at the time it was published, given the data available. Can we quit beating this dead horse already? It'd be like Toyota continuing to advertise having the 2000 Truck of the Year.

As long as this thread remains not locked, the dead horse beating will continue.

I don't think locking this thread would be smart. It's become a dumping ground for roundabout news, and any other roundabout threads would almost certainly become a discussion on safety anyways.

Agree, there's no reason to lock the thread, and it has become a dumping ground lately...for one-off news reports of fatal crashes. Anyone with a Google news subscription to the term 'roundabout' can get the same info. I'd argue that just seeing that kind of new post dilutes the value of the thread, since we all know these crashes happen on occasion. Where's the thread devoted to reporting crashes at signals, stop signs, or grade crossings? Or are roundabouts the only horse in the race?
"We gotta find this road, it's like Bob's road!" - Rabbit, Twister

tradephoric

Over the past week two motorcyclist have been killed in separate roundabout crashes.  At this rate, each roundabout in America would average 0.0208 fatal crashes per year (104 fatalities / 5000 roundabouts).  How does that compare to the number of fatalities at traffic signals?  According to FHWA data, there were 2,924 fatalities at approximately 311,000 signalized intersections in 2007.  This equates to 0.0094 fatal crashes per traffic signal.  So, I could publish a report that concludes that the estimated number of fatal crashes per roundabout in the U.S. is about twice as high as the number of fatal crashes per traffic signal in the U.S.  (0.0208 fatal crashes per roundabout vs. 0.0094 fatal crashes per signal).   

DabigE, you would bash me for making safety conclusions based on one week of crash data.   The scope is way too narrow.  But you fail to acknowledge the narrow scope of the 2000 IIHS study.  The only multi-lane roundabouts analyzed in that study (with before/after injury data) was along a 25 mph roadway through a ski-resort in Colorado.  Your only criticism of the 2000 IIHS study is that it's outdated.  At least my report would only be about a week old.  It's amazing that the safety conclusions from such a weak study could be perpetuated for the next 20 years in an attempt to gain public support for roundabouts in this country, and seemingly smart people like yourself never question it.

DaBigE

Quote from: tradephoric on April 17, 2018, 02:39:29 PM
DabigE, you would bash me for making safety conclusions based on one week of crash data.   The scope is way too narrow.  But you fail to acknowledge the narrow scope of the 2000 IIHS study.  The only multi-lane roundabouts analyzed in that study (with before/after injury data) was along a 25 mph roadway through a ski-resort in Colorado.  Your only criticism of the 2000 IIHS study is that it's outdated.  At least my report would only be about a week old.  It's amazing that the safety conclusions from such a weak study could be perpetuated for the next 20 years in an attempt to gain public support for roundabouts in this country, and seemingly smart people like yourself never question it.

OMFG...I can't tell if you're that dense or just have that selective of a memory. I haven't treated the 2000 IIHS study as the gospel of roundabouts, nor have I thrown the baby out with the bath water. Frankly, I have yet to see a study on roundabouts that doesn't have some level of significant flaw to it, including the recent ones from Wisconsin and Minnesota. Being old is far from my only criticism of the IIHS study; however, that is one of the main reasons why I believe it should stop being quoted...a concept which you can't seem to grasp.
"We gotta find this road, it's like Bob's road!" - Rabbit, Twister

tradephoric

So DaBigE, now you do think the 2000 IIHS study is flawed?  Not only flawed, but significantly flawed.  Good to hear you came around from earlier today when you said the study was "accurate".  That was a good laugh. 

DaBigE

Quote from: tradephoric on April 17, 2018, 04:13:05 PM
So DaBigE, now you do think the 2000 IIHS study is flawed?  Not only flawed, but significantly flawed.  Good to hear you came around from earlier today when you said the study was "accurate".  That was a good laugh.

Back to our selective reading and quote twisting once again, I see. And glad I could provide you a laugh...it's probably about time, since you've been making my stomach hurt from laughing so hard lately.

Quote from: DaBigE on April 16, 2018, 04:56:35 PM
It was accurate at the time it was published, given the data available.

Note the text that was already italicized. In hindsight, I probably should have said "given the data that was used". In any case, at the time, how many roundabouts had fatalities in the US at the time the study was done? How many roundabouts were studied? Given the data the IIHS included, the results of the study were accurate. But that is also how it is flawed...using a limited data set. That is how something can be both accurate and flawed at the same time. :-o

But to one of your other points: If you're going to do a comprehensive study of roundabouts, there's going to be a few which will not have any before crash data, since not all roundabouts are built purely for safety benefits. Unfortunately, that doesn't fit the broad picture you've been attempting to paint for the last 68+ pages. This is when comparing the expected number of crashes vs the actual number of crashes would come into play.
"We gotta find this road, it's like Bob's road!" - Rabbit, Twister

tradephoric

#1715
The notorious M-5 and Pontiac Trail roundabout has been the most crash prone intersection in Michigan for several years.  Now they are planning a $100 million retail center along the vacant land right next to the roundabout.  I love how Commerce Township supervisor David Scott cites a traffic study stating "This project, surprisingly, creates no traffic problems that didn't already exist."   :-D :awesomeface:  :biggrin:   

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

billpa

It should be noted the motorcyclist who died in Bear, Del was not wearing a helmet. I realize it's always the roundabout's fault. I just thought I'd put it in the permanent record.

Pixel 2


tradephoric

There are calls for a roundabout to be built at Highway 35 and Highway 335 in Saskatchewan, which was the site of the Humboldt Broncos bus tragedy that killed 16 on April 6th.  A flashing light was added to the stop sign in 1997, after a pickup blew through the stop sign into the path of a semi-truck and killed 6 people.  So at least 22 people have died at the stop-controlled intersection over the past 21 years.  That's obviously a horrible result. 

https://globalnews.ca/news/4156114/highway-roundabouts-alberta-humboldt-broncos-bus-crash/

But adding a sharp curve in the middle of a high-speed rural roadway (ie. a roundabout) is not the way to make the roadway safer IMO.  There are other ways to prevent drivers from crashing into each other beyond adding sharp curves along a rural roadways.  What if the bus driver isn't paying attention as they approach the rural roundabout, takes the roundabout too fast and flips the bus on its side?  Worse yet.. what if there is a big retaining wall in the middle of the roundabout, and the bus experiences brake failure and strikes the retaining wall head on at 80kph?  OTOH, if it remains a straight section of rural-road, and the bus experiences brake failure, it could fly through the "straight"  intersection at 80kph with no harm, unless if there is another vehicle in the direct path of the bus.  If there is another vehicle in the buses direct path, it can instantly kill 16 people which obviously is a massive tragedy.  So the question becomes how do you prevent the semi-truck from being in the path of the bus at that rural intersection in Saskatchewan?

The answer to the problem, IMO, is connected vehicles.  If the bus driver was warned that a vehicle was approaching the intersection at high speed and a collision avoidance warning was displayed, the driver could have taken evasive action to avoid this deadly crash.  The semi-truck was approaching from the west where there is a line of trees that would have obstructed the bus-drivers view of the approaching semi-truck.  The only way for the bus driver to know that a semi-truck was approaching the intersection is if the two vehicles were communicating with each other.  This connected vehicle technology is already available in some luxtury vehicles, most notably Cadillac's CTS sedan.  GM is dedicated to advancing this technology, regardless of government mandates (i believe the Trump administration recently reversed the Obama administration's decision that would have mandated auto-makers to include vehicle-2-vehicle communications in new vehicles).

DaBigE

Quote from: tradephoric on April 23, 2018, 11:47:53 AM
There are calls for a roundabout to be built at Highway 35 and Highway 335 in Saskatchewan, which was the site of the Humboldt Broncos bus tragedy that killed 16 on April 6th.  A flashing light was added to the stop sign in 1997, after a pickup blew through the stop sign into the path of a semi-truck and killed 6 people.  So at least 22 people have died at the stop-controlled intersection over the past 21 years.  That's obviously a horrible result. 

https://globalnews.ca/news/4156114/highway-roundabouts-alberta-humboldt-broncos-bus-crash/

But adding a sharp curve in the middle of a high-speed rural roadway (ie. a roundabout) is not the way to make the roadway safer IMO.  There are other ways to prevent drivers from crashing into each other beyond adding sharp curves along a rural roadways.  What if the bus driver isn't paying attention as they approach the rural roundabout, takes the roundabout too fast and flips the bus on its side?  Worse yet.. what if there is a big retaining wall in the middle of the roundabout, and the bus experiences brake failure and strikes the retaining wall head on at 80kph?  OTOH, if it remains a straight section of rural-road, and the bus experiences brake failure, it could fly through the "straight"  intersection at 80kph with no harm, unless if there is another vehicle in the direct path of the bus.  If there is another vehicle in the buses direct path, it can instantly kill 16 people which obviously is a massive tragedy.  So the question becomes how do you prevent the semi-truck from being in the path of the bus at that rural intersection in Saskatchewan?

The answer to the problem, IMO, is connected vehicles.  If the bus driver was warned that a vehicle was approaching the intersection at high speed and a collision avoidance warning was displayed, the driver could have taken evasive action to avoid this deadly crash.  The semi-truck was approaching from the west where there is a line of trees that would have obstructed the bus-drivers view of the approaching semi-truck.  The only way for the bus driver to know that a semi-truck was approaching the intersection is if the two vehicles were communicating with each other.  This connected vehicle technology is already available in some luxtury vehicles, most notably Cadillac's CTS sedan.  GM is dedicated to advancing this technology, regardless of government mandates (i believe the Trump administration recently reversed the Obama administration's decision that would have mandated auto-makers to include vehicle-2-vehicle communications in new vehicles).

That's one hell of a slippery slope and a lot of 'what ifs', yet you forget one big one: What if the connected vehicle technology fails?

What if there's a bus full of little kids coming from all directions and all electronic devices fail, and they're in dense fog?

There is no perfect solution that will prevent every conceivable method of tragedy. A properly designed roundabout is arguably the best low-tech solution, with somewhat-reasonable costs. A grade-separated interchange would be the ultimate solution, but comes at price that likely fails to achieve a reasonable cost-benefit ratio. Connected vehicle technology is only viable once there is significant market saturation. And with the current price of vehicles and how long the average person keeps their car nowadays, that's going to take a long time.

There are many rural, high-speed roundabouts that have achieved their goal of reducing serious-injury and fatal crash events. Most of them fall off your radar since they're single-lane roundabouts. But they also employ sound design practices: physical upstream guidance, approach signing, transitional lighting, and forgiving landscape design.
"We gotta find this road, it's like Bob's road!" - Rabbit, Twister

kalvado

Quote from: DaBigE on April 23, 2018, 02:04:27 PM
Quote from: tradephoric on April 23, 2018, 11:47:53 AM
There are calls for a roundabout to be built at Highway 35 and Highway 335 in Saskatchewan, which was the site of the Humboldt Broncos bus tragedy that killed 16 on April 6th.  A flashing light was added to the stop sign in 1997, after a pickup blew through the stop sign into the path of a semi-truck and killed 6 people.  So at least 22 people have died at the stop-controlled intersection over the past 21 years.  That's obviously a horrible result. 

https://globalnews.ca/news/4156114/highway-roundabouts-alberta-humboldt-broncos-bus-crash/

But adding a sharp curve in the middle of a high-speed rural roadway (ie. a roundabout) is not the way to make the roadway safer IMO.  There are other ways to prevent drivers from crashing into each other beyond adding sharp curves along a rural roadways.  What if the bus driver isn't paying attention as they approach the rural roundabout, takes the roundabout too fast and flips the bus on its side?  Worse yet.. what if there is a big retaining wall in the middle of the roundabout, and the bus experiences brake failure and strikes the retaining wall head on at 80kph?  OTOH, if it remains a straight section of rural-road, and the bus experiences brake failure, it could fly through the "straight"  intersection at 80kph with no harm, unless if there is another vehicle in the direct path of the bus.  If there is another vehicle in the buses direct path, it can instantly kill 16 people which obviously is a massive tragedy.  So the question becomes how do you prevent the semi-truck from being in the path of the bus at that rural intersection in Saskatchewan?

The answer to the problem, IMO, is connected vehicles.  If the bus driver was warned that a vehicle was approaching the intersection at high speed and a collision avoidance warning was displayed, the driver could have taken evasive action to avoid this deadly crash.  The semi-truck was approaching from the west where there is a line of trees that would have obstructed the bus-drivers view of the approaching semi-truck.  The only way for the bus driver to know that a semi-truck was approaching the intersection is if the two vehicles were communicating with each other.  This connected vehicle technology is already available in some luxtury vehicles, most notably Cadillac's CTS sedan.  GM is dedicated to advancing this technology, regardless of government mandates (i believe the Trump administration recently reversed the Obama administration's decision that would have mandated auto-makers to include vehicle-2-vehicle communications in new vehicles).

That's one hell of a slippery slope and a lot of 'what ifs', yet you forget one big one: What if the connected vehicle technology fails?

What if there's a bus full of little kids coming from all directions and all electronic devices fail, and they're in dense fog?

There is no perfect solution that will prevent every conceivable method of tragedy. A properly designed roundabout is arguably the best low-tech solution, with somewhat-reasonable costs. A grade-separated interchange would be the ultimate solution, but comes at price that likely fails to achieve a reasonable cost-benefit ratio. Connected vehicle technology is only viable once there is significant market saturation. And with the current price of vehicles and how long the average person keeps their car nowadays, that's going to take a long time.

There are many rural, high-speed roundabouts that have achieved their goal of reducing serious-injury and fatal crash events. Most of them fall off your radar since they're single-lane roundabouts. But they also employ sound design practices: physical upstream guidance, approach signing, transitional lighting, and forgiving landscape design.
There is another option on the table, it is called "traffic light".
We are talking about a situation where vehicle has to slow down - and possibly come to a stop - to negotiate the intersection. For both roundabout and traffic light (and for a stop sign, for that matter) an advance warning has to be given - and received! - by a driver in order to achieve safe outcome. Failure to do so can - and in some designs will, cause a significant accident. That is pretty much all you need to know talking about fog or anything. Properly designed roundabout is probably worse than properly designed traffic light for this situation, as it falls under "will" part of it..

tradephoric

Quote from: DaBigE on April 23, 2018, 02:04:27 PM
Connected vehicle technology is only viable once there is significant market saturation. And with the current price of vehicles and how long the average person keeps their car nowadays, that's going to take a long time.

V2V is included as a standard feature on 2017 Cadillac CTS's sold in the U.S. and Canada.  It does take time for standard features in luxury models to trickle down to the compact car segment, but it will come.  I mean, is ABS only a standard option in Cadillac's today?

Quote from: DaBigE on April 23, 2018, 02:04:27 PM
What if there's a bus full of little kids coming from all directions and all electronic devices fail, and they're in dense fog?

In that case all the safety layers have broken down, and all that's left to do is cross your fingers that the buses don't end up in the intersection at the exact same time.  But if it's so foggy that the driver can't see the traffic signal, what makes you think they would be able to safely navigate through the sharp curves of a roundabout?  Below are two videos; one is a driver blowing through a red light and one blowing through a roundabout.  No harm, no foul with the red light runner!  Apparently that blue SUV had V2V in their vehicle, because they slammed on his brakes avoiding t-boning that vehicle.  Amazing...

https://www.youtube.com/watch?v=vuH-oZZBBjU

https://www.youtube.com/watch?v=McGRv0FjBI8

There will be growing pains with connected vehicles, and there are a lot of issues to sort out still.  But in 10 years, you can't see a world where drivers approaching an intersection will be warned of red light runners?  That's what GM has in mind when they included V2V technology in their 2017 CTS model.  Here is an excerpt from their press release:

QuoteCadillac's V2V solution uses Dedicated Short-Range Communications (DSRC) and GPS and can handle 1,000 messages per second from vehicles up to nearly 1,000 feet away. For example, when a car approaches an urban intersection, the technology scans the vicinity for other vehicles and tracks their positions, directions and speeds, warning the driver of potential hazards that might otherwise be invisible.
http://media.cadillac.com/media/us/en/cadillac/news.detail.html/content/Pages/news/us/en/2017/mar/0309-v2v.html

If connected vehicles are successful and widespread adaptation takes place, there could be a day where it becomes very difficult to get t-boned by a red-light runner.  At that point, roundabouts may become more dangerous than signalized intersections.  Think about it,  mechanical failures will still happen and any bus that loses their brakes approaching a roundabout is going to FLY over the roundabout dukes of hazard style... much like the video above... HOLD ON KIDS!!!  In theory, with connected vehicles the only way two vehicles would get in a t-bone accident is if both vehicles lost their brakes, and end up entering the intersection at the exact same time.  The connected vehicles will know that there is about to be an imminent crash, but won't be able to prevent it because the brakes are unable to be applied.  But then again, maybe the connected vehicles can determine that if one vehicle speeds up by 5 mph, it will be able to clear the intersection before the other "out of control"  vehicle enters the intersection.  It will give the warning "SPEED UP!"  in an attempt to prevent a deadly t-bone crash.

DaBigE

Quote from: tradephoric on April 24, 2018, 12:08:09 AM
Quote from: DaBigE on April 23, 2018, 02:04:27 PM
Connected vehicle technology is only viable once there is significant market saturation. And with the current price of vehicles and how long the average person keeps their car nowadays, that's going to take a long time.

V2V is included as a standard feature on 2017 Cadillac CTS's sold in the U.S. and Canada.  It does take time for standard features in luxury models to trickle down to the compact car segment, but it will come.  I mean, is ABS only a standard option in Cadillac's today?

Again, you missed the point. Yes, the technology will eventually reach every car in every showroom. I recently sat in on a CV presentation, where it was said that VW promises to have the capability to send V2V data across its lineup within the next 2 model years. BUT IT STILL HAS TO REACH THE CONSUMER. Unless Oprah plans on several mass car giveaways, there will still be a large number of vehicles on the road still living in the technological dark ages. The average age of a car on the road is 11.5 years and trends shows signs of that growing older, especially as new car prices continue to increase and wages have not kept up (not to mention the elephant of health care costs). That also does not address the population of classic car collectors. The future of car tech looks very promising, but we still have to work with what is out there today and will be tomorrow. Further, as Uber has recently taught us, technology isn't infallible.

Quote from: tradephoric on April 24, 2018, 12:08:09 AM
Quote from: DaBigE on April 23, 2018, 02:04:27 PM
What if there's a bus full of little kids coming from all directions and all electronic devices fail, and they're in dense fog?

In that case all the safety layers have broken down, and all that's left to do is cross your fingers that the buses don't end up in the intersection at the exact same time.  But if it's so foggy that the driver can't see the traffic signal, what makes you think they would be able to safely navigate through the sharp curves of a roundabout?

Headlights, streetlights, and street signs still work in fog. Throw in a power outage for good measure, and you still have headlights and retroreflective signs and pavement markings. No different than a car negotiating tight mountain pass curves.

Quote from: kalvado on April 23, 2018, 03:56:45 PM
There is another option on the table, it is called "traffic light".

I never said it wasn't an option. It's just not an option that is designed to prevent high-speed t-bone crashes.
"We gotta find this road, it's like Bob's road!" - Rabbit, Twister

kalvado

Quote from: DaBigE on April 24, 2018, 11:48:06 AM


Quote from: kalvado on April 23, 2018, 03:56:45 PM
There is another option on the table, it is called "traffic light".

I never said it wasn't an option. It's just not an option that is designed to prevent high-speed t-bone crashes.
Apparently, you're doing same thing Trade is criticizing in FHWA report throughout this thread (with little understanding from the rest of the gang)  : you assume roundabout forces drivers to slow down. Nope, in your "dense fog" scenario roundabout as prone to t-bone as traffic lights are. Driver has to get a "slow down" message in advance, something coming out of the fog will only make them die confused.. 

DaBigE

So a curve can't force you to slow down. Gotcha. Shall I start finding mountain roads for you?
"We gotta find this road, it's like Bob's road!" - Rabbit, Twister

kalvado

Quote from: DaBigE on April 24, 2018, 12:47:49 PM
So a curve can't force you to slow down. Gotcha. Shall I start finding mountain roads for you?
A sharp curve in a fog - and remember, we're talking about
Quote from: DaBigE on April 23, 2018, 02:04:27 PM
What if there's a bus full of little kids coming from all directions and all electronic devices fail, and they're in dense fog?
can easily be a cause for a crash if driver doesn't see it in advance.
Remember, you brought up dense fog as a situation we're talking about. And deliberately introduced extra curves - on roundabout approach and the circle itself - do increase probability of a serious accident.   And there was an example of such accident somewhere upstream in the thread..



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