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Crash prone 'modern roundabouts'

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

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jakeroot

#2000
WSDOT is installing ramp meters at the Steptoe roundabout in Richland. Instead of HAWK signals like those in Carmel, these will be traditional ramp meter signals.

it's only a matter of time before we have four lane signalized roundabouts.

https://youtu.be/ieKxXKtOADs


kalvado

Quote from: kphoger on October 12, 2018, 01:24:05 PM
Quote from: jakeroot on October 11, 2018, 04:23:50 PM
the real issue is when peds are crossing the exit legs.

That sums up what I was getting at.  For a stoplight or STOP-controlled intersection with slip lanes, there is no "exit leg" crosswalk because both entry and exit leg crossings are combined into one.  kalvado seems to have missed that I was generally agreeing with him about that, but it's probably because I was so wordy.

One solution to that is to use mid-block crosswalks near roundabouts rather than crosswalks nearer the roundabout.  However, assuming that pedestrians will walk half a block to cross a street when no actual law prohibits them from doing so nearer the roundabout is... unrealistic and would require fencing.  (The states whose laws I'm familiar with only prohibit crossing the street outside of crosswalks if there is a stoplight within a block of that location.)
I really misunderstood you, sorry about that. Doesn't change my reply too much, though. I am trying to talk facts, not personal arguments. :bigass:


kphoger

Yeah, I was too lazy to actually post the codes.  Thanks for linking to them.

https://law.justia.com/codes/new-jersey/2013/title-39/section-39-4-33/
First two words:  "At intersections".
Does not apply to crossing the street mid-block.

https://law.justia.com/codes/new-jersey/2013/title-39/section-39-4-34/
Specifically states:  "in the absence of a crosswalk, and where not otherwise prohibited, at right angles to the roadway."
As long as you don't cross diagonally, then does not apply to crossing mid-block.

https://law.justia.com/codes/new-jersey/2013/title-39/section-39-4-36/
Laws pertaining to drivers, not to pedestrians.

Quote from: kalvado on October 12, 2018, 05:11:29 PM
Right of way within crosswalk, yield to vehicles elsewhere - but otherwise cross anywhere except if explicitly prohibited.

Precisely.




Quote from: jakeroot on October 12, 2018, 05:26:53 PM
it's only a matter of time before we have four lane signalized roundabouts.

ick!
Keep right except to pass.  Yes.  You.
Visit scenic Orleans County, NY!
Male pronouns, please.

Quote from: Philip K. DickIf you can control the meaning of words, you can control the people who must use them.

johndoe

#2003
Quote from: jakeroot on October 12, 2018, 05:26:53 PM
WSDOT is installing ramp meters at the Steptoe roundabout in Richland.

In the Google imagery you can tell they used to have multilane approaches: https://goo.gl/maps/vNEEKYYPKgM2
Sure enough: https://www.tri-cityherald.com/latest-news/article32210604.html
http://www.au2pb.com/steptoe/


I wonder if the queue reached the freeway with two westbound lanes. Interesting the DOT decided to meter it rather than any other multilane option (different signs, markings, speed table).

Also interesting that the movement from westbound Columbia Park Trail to eastbound 240 has required a lane change in both striping layouts....not a fan of that.  I wonder why they didn't stripe the westbound lane to the left rather than right circulating lane.

jakeroot

Quote from: johndoe on October 12, 2018, 08:36:11 PM
Quote from: jakeroot on October 12, 2018, 05:26:53 PM
WSDOT is installing ramp meters at the Steptoe roundabout in Richland.

In the Google imagery you can tell they used to have multilane approaches: https://goo.gl/maps/vNEEKYYPKgM2
Sure enough: https://www.tri-cityherald.com/latest-news/article32210604.html
http://www.au2pb.com/steptoe/

I wonder if the queue reached the freeway with two westbound lanes. Interesting the DOT decided to meter it rather than any other multilane option (different signs, markings, speed table).

It's one of only a couple roundabouts in WA where lane modifications have taken place. The Steptoe Roundabout has gone through three (maybe four) changes to its markings. I guess they got fed up. Lots of collisions, apparently.

I am wondering if the single lane approach makes it so there's a near-constant flow of cars from the east, rather than two or four at a time with two lanes. The occasional breaks would have made it easier for traffic from 240 to enter the roundabout.

kalvado

Quote from: kphoger on October 12, 2018, 06:07:36 PM
Yeah, I was too lazy to actually post the codes.  Thanks for linking to them.

https://law.justia.com/codes/new-jersey/2013/title-39/section-39-4-33/
First two words:  "At intersections".
Does not apply to crossing the street mid-block.

https://law.justia.com/codes/new-jersey/2013/title-39/section-39-4-34/
Specifically states:  "in the absence of a crosswalk, and where not otherwise prohibited, at right angles to the roadway."
As long as you don't cross diagonally, then does not apply to crossing mid-block.

https://law.justia.com/codes/new-jersey/2013/title-39/section-39-4-36/
Laws pertaining to drivers, not to pedestrians.

Quote from: kalvado on October 12, 2018, 05:11:29 PM
Right of way within crosswalk, yield to vehicles elsewhere - but otherwise cross anywhere except if explicitly prohibited.

Precisely.


Problem is, that on one hand pedestrians are a part of traffic flow with well-defined rights and responsibilities; but on the other hand, they are rarely, if ever, held responsible for ignoring those responsibilities. 
Jaywalking - as in crossing outside marked or unmarked crosswalk - but press (often) and insurance (always) consider vehicle-pedestrian accidents outside crosswalk as driver's responsibility. Since there is normally no criminal charges for accidents where drivers act in good faith, that pretty much means the concept of right of way is non-existent for pedestrians.
I do see some good reasons for that, considering person outside crosswalk as an open season game is a bad idea. But sometimes I feel things are going too far.

Back to roundabouts: there are some nice examples in posts above with grade-separated walkways, either to the center island or under the arms of roundabout. Rainwater drainage is, apparently, one of the technical problems which can be dealt with. However, I was told - on multiple occasions! - that US public is unable to deal with underground crosswalks until there is an armed cop stationed there 24/7...

kphoger

Quote from: kalvado on October 13, 2018, 01:52:38 AM
Back to roundabouts: there are some nice examples in posts above with grade-separated walkways, either to the center island or under the arms of roundabout. Rainwater drainage is, apparently, one of the technical problems which can be dealt with. However, I was told - on multiple occasions! - that US public is unable to deal with underground crosswalks until there is an armed cop stationed there 24/7...

The underground passageways I've used could be made a LOT more inviting with better lighting and maybe some art along the walls.  But bare concrete with cobwebbed dingy lights or no lights at all is more common: not exactly what inspires confidence in your personal security.  Interestingly, my mother was once assaulted on a pedestrian overpass back in the 1970s on her way to work.  It was this one over I-64.  She fought him off with her purse.
Keep right except to pass.  Yes.  You.
Visit scenic Orleans County, NY!
Male pronouns, please.

Quote from: Philip K. DickIf you can control the meaning of words, you can control the people who must use them.

kalvado

Quote from: kphoger on October 14, 2018, 04:06:04 PM
Quote from: kalvado on October 13, 2018, 01:52:38 AM
Back to roundabouts: there are some nice examples in posts above with grade-separated walkways, either to the center island or under the arms of roundabout. Rainwater drainage is, apparently, one of the technical problems which can be dealt with. However, I was told - on multiple occasions! - that US public is unable to deal with underground crosswalks until there is an armed cop stationed there 24/7...

The underground passageways I've used could be made a LOT more inviting with better lighting and maybe some art along the walls.  But bare concrete with cobwebbed dingy lights or no lights at all is more common: not exactly what inspires confidence in your personal security.  Interestingly, my mother was once assaulted on a pedestrian overpass back in the 1970s on her way to work.  It was this one over I-64.  She fought him off with her purse.
A vicious circle - they are not used because they are scary, and once they are not used - they grow scary, including higher risk of meeting with someone with bad intentions.
Punishing ADA requirements really don't help the case.

jakeroot

Quote from: kalvado on October 14, 2018, 05:13:15 PM
Quote from: kphoger on October 14, 2018, 04:06:04 PM
Quote from: kalvado on October 13, 2018, 01:52:38 AM
Back to roundabouts: there are some nice examples in posts above with grade-separated walkways, either to the center island or under the arms of roundabout. Rainwater drainage is, apparently, one of the technical problems which can be dealt with. However, I was told - on multiple occasions! - that US public is unable to deal with underground crosswalks until there is an armed cop stationed there 24/7...

The underground passageways I've used could be made a LOT more inviting with better lighting and maybe some art along the walls.  But bare concrete with cobwebbed dingy lights or no lights at all is more common: not exactly what inspires confidence in your personal security.  Interestingly, my mother was once assaulted on a pedestrian overpass back in the 1970s on her way to work.  It was this one over I-64.  She fought him off with her purse.

A vicious circle - they are not used because they are scary, and once they are not used - they grow scary, including higher risk of meeting with someone with bad intentions.
Punishing ADA requirements really don't help the case.

Lighting and width are key. Both are problems with modern attempts. Even Dutch underpasses are too narrow, and they're probably the best around.

That I-64 overpass shows exactly why overpasses are not always better. They usually require massive fences to prevent jumping and throwing, and always end up too narrow, more than likely due to budget constraints. Underpasses that are wide are really the best option, although wide pedestrian overpasses are okay too. If it's a freeway, an overpass is really the only option (not enough light seepage for an underpass, even a wide one), so making it wide and/or using a bit more glass are options.

mrsman

Quote from: jamess on October 08, 2018, 06:15:52 PM
From the previous page, this looks incredibly dangerous.

A pedestrian standing at the star needs to monitor 4 lanes of traffic before they can cross safely. Worse, the drivers at 1 and 2 will be looking only left and will take the first clear slot the accelerate straight into the crosswalk before confirming it is clear.

The crosswalk with the arrow has a triple threat, and the straight exit means vehicles will be accelerating quickly out of the circle.

Worse, the roundabout is designed so bicyclists exit the lane and use the crosswalks (note the ramps). Thats incredibly dangerous at the speeds this is designed for.

Incredibly irresponsible design.



WIth many of these larger roundabouts, especially the one pictured above, there seems to be little merging and instead very dangerous crossing.  Assuming the top left corner is north, the northbound 2 lanes intersect the 3 eastbound lanes, make a slight bend around and then intersect the two westbound lanes before continuing out of the roundabout.  Essentially, 2 uncontrolled intersections face every thru direction.  Extremely dangerous.

The situation reminds me of Scott Circle in DC.  Ignoring 16th street which goes underneath the circle, you have Mass Ave and RI Ave meeting in the circle, but the circle is so elongated that it is as though the two streams of streets meet at near-right angles, signalized intersections.  While the extra traffic signals do cause delay, at least there is no need to provide left turn phasing and the signals do increase safety.  The current layout is probably about equal in delay to a 6-point signalized intersection that you'd commonly see in Chicago.

https://www.google.com/maps/place/Scott+Cir+NW,+Washington,+DC/@38.907165,-77.0364776,18z/data=!4m5!3m4!1s0x89b7b7c0896e870b:0xf7c64d55f17ac8e3!8m2!3d38.9070139!4d-77.0365426

I am extremely worried about these multilane circles and roundabouts without traffic direction.  There does not seem to be any control and just letting drivers do what they want is chaotic.

kphoger

Quote from: mrsman on October 14, 2018, 08:43:29 PM
WIth many of these larger roundabouts, especially the one pictured above, there seems to be little merging and instead very dangerous crossing.  Assuming the top left corner is north, the northbound 2 lanes intersect the 3 eastbound lanes, make a slight bend around and then intersect the two westbound lanes before continuing out of the roundabout.  Essentially, 2 uncontrolled intersections face every thru direction.  Extremely dangerous.

This is a problem inherent in the design of a multi-lane roundabout.  No amount of flaring the lanes or expanding the circle will eliminate the conflict points.  The key reason given for roundabouts' reduction in collision severity is that it substitutes side-swipe accidents for T-bone accidents.  With multi-lane roundabouts, however, some of the T-bone possibility remains, except that the angle of collision is reduced somewhat.

See my post below:

Quote from: kphoger on January 11, 2018, 02:27:55 PM
Quote from: webny99 on January 11, 2018, 12:06:38 PM
Though multi-lane roundabouts can be annoying due to driver ignorance and hesitation, I fail to see how they are, functionally, any different from a standard one-lane roundabout.

I used to think that too.  However, I figured out a functional difference several months ago.  All of a single-lane roundabout's conflict points are side-swipe, the result of merging into a lane where there's already a car.  However, in a multi-lane roundabout, straight-through traffic can actually conflict in a more catastrophic way.

In order to avoid the green star conflict point illustrated below, the right lane of the approaches would need to be right-turn-only–effectively making it a single-lane roundabout with slip lanes.


Keep right except to pass.  Yes.  You.
Visit scenic Orleans County, NY!
Male pronouns, please.

Quote from: Philip K. DickIf you can control the meaning of words, you can control the people who must use them.

cjw2001

Quote from: mrsman on October 14, 2018, 08:43:29 PM

Assuming the top left corner is north, ...

The top left corner is east.

jakeroot

Quote from: kphoger on January 11, 2018, 02:27:55 PM
In order to avoid the green star conflict point illustrated below, the right lane of the approaches would need to be right-turn-only–effectively making it a single-lane roundabout with slip lanes.

https://i.imgur.com/SLCiqgK.png

It could remain as-is. Many multi-lane "modern roundabouts" have this path overlap issue, it just requires drivers to be aware of the origin of the vehicles around them. The blue line should have recognized that the red line entered from a different point, so the red line won't necessarily keep going around. If drivers stagger their positioning in a roundabout, there would be less chance for conflict. But that's asking a lot.

Of course, this puts great trust in drivers, and lacking that trust, we usually avoid path overlap. But a lot of countries do design roundabouts with path overlaps, intentionally or otherwise. This eastbound movement in Melbourne, Australia, for example. Many roundabouts in the UK feature "path overlap" in the strictest sense, but they usually don't have lane markings, so nobody assumes anything.

kphoger

Quote from: jakeroot on October 15, 2018, 02:56:44 PM
Many multi-lane "modern roundabouts" have this path overlap issue

My point was that all multi-lane roundabouts have path overlap.
Keep right except to pass.  Yes.  You.
Visit scenic Orleans County, NY!
Male pronouns, please.

Quote from: Philip K. DickIf you can control the meaning of words, you can control the people who must use them.

jamess

Quote from: mrsman on October 14, 2018, 08:43:29 PM
Quote from: jamess on October 08, 2018, 06:15:52 PM
From the previous page, this looks incredibly dangerous.

A pedestrian standing at the star needs to monitor 4 lanes of traffic before they can cross safely. Worse, the drivers at 1 and 2 will be looking only left and will take the first clear slot the accelerate straight into the crosswalk before confirming it is clear.

The crosswalk with the arrow has a triple threat, and the straight exit means vehicles will be accelerating quickly out of the circle.

Worse, the roundabout is designed so bicyclists exit the lane and use the crosswalks (note the ramps). Thats incredibly dangerous at the speeds this is designed for.

Incredibly irresponsible design.



WIth many of these larger roundabouts, especially the one pictured above, there seems to be little merging and instead very dangerous crossing.  Assuming the top left corner is north, the northbound 2 lanes intersect the 3 eastbound lanes, make a slight bend around and then intersect the two westbound lanes before continuing out of the roundabout.  Essentially, 2 uncontrolled intersections face every thru direction.  Extremely dangerous.

The situation reminds me of Scott Circle in DC.  Ignoring 16th street which goes underneath the circle, you have Mass Ave and RI Ave meeting in the circle, but the circle is so elongated that it is as though the two streams of streets meet at near-right angles, signalized intersections.  While the extra traffic signals do cause delay, at least there is no need to provide left turn phasing and the signals do increase safety.  The current layout is probably about equal in delay to a 6-point signalized intersection that you'd commonly see in Chicago.

https://www.google.com/maps/place/Scott+Cir+NW,+Washington,+DC/@38.907165,-77.0364776,18z/data=!4m5!3m4!1s0x89b7b7c0896e870b:0xf7c64d55f17ac8e3!8m2!3d38.9070139!4d-77.0365426

I am extremely worried about these multilane circles and roundabouts without traffic direction.  There does not seem to be any control and just letting drivers do what they want is chaotic.

Very good point.

By making the exits a straight-through movement, youre getting very close to creating a t-bone scenario. This is in contrast to the Dutch model where exiting vehicles are turning left then right, thus allowing more of a sideswipe.

jakeroot

Quote from: kphoger on October 15, 2018, 02:58:43 PM
Quote from: jakeroot on October 15, 2018, 02:56:44 PM
Many multi-lane "modern roundabouts" have this path overlap issue

My point was that all multi-lane roundabouts have path overlap.

Path overlap technically only exists when drivers are required to follow an invisible line after entering the roundabout, in order to go straight or turn right. Roundabout markings help guide traffic out of roundabouts, not into them, so most roundabouts are designed so that entering traffic does not need to turn their steering wheel to cross over the path of exiting traffic.

In the image above, the entries don't require traffic to do anything except except proceed straight across the path of exiting traffic. At the intersection below, the entrances from the top-bottom have very little path overlap, but the left-right entries have a massive path overlap (so they have to follow their own invisible line around the roundabout, not the one painted on the ground, which is for traffic that is exiting -- yes that's confusing).


silverback1065


kphoger

Quote from: jakeroot on October 15, 2018, 03:36:06 PM
Quote from: kphoger on October 15, 2018, 02:58:43 PM
Quote from: jakeroot on October 15, 2018, 02:56:44 PM
Many multi-lane "modern roundabouts" have this path overlap issue

My point was that all multi-lane roundabouts have path overlap.

Path overlap technically only exists when drivers are required to follow an invisible line after entering the roundabout, in order to go straight or turn right. Roundabout markings help guide traffic out of roundabouts, not into them, so most roundabouts are designed so that entering traffic does not need to turn their steering wheel to cross over the path of exiting traffic.

In the image above, the entries don't require traffic to do anything except except proceed straight across the path of exiting traffic. At the intersection below, the entrances from the top-bottom have very little path overlap, but the left-right entries have a massive path overlap (so they have to follow their own invisible line around the roundabout, not the one painted on the ground, which is for traffic that is exiting -- yes that's confusing).



Sorry, I must have misunderstood what you meant by "overlap."
What I mean to say is that all mutli-lane roundabouts have paths that cross each other, not just paths that merge and diverge.

By my count, at a typical double-lane roundabout, left turning traffic crosses paths (not just merges or diverges) with four separate lane movements.
In the roundabout below, red traffic coming from the left crosses paths at the four triangles.

Keep right except to pass.  Yes.  You.
Visit scenic Orleans County, NY!
Male pronouns, please.

Quote from: Philip K. DickIf you can control the meaning of words, you can control the people who must use them.

kalvado

Quote from: kphoger on October 15, 2018, 04:49:27 PM

What I mean to say is that all mutli-lane roundabouts have paths that cross each other, not just paths that merge and diverge.

By my count, at a typical double-lane roundabout, left turning traffic crosses paths (not just merges or diverges) with four separate lane movements.
In the roundabout below, red traffic coming from the left crosses paths at the four triangles.


And here is a standard "roundabout is better - it has less conflict points" pic:

Roundabouts are sold as having single merge/diverge point... Which is a bit dishonest from my perspective.

kphoger

Quote from: kalvado on October 15, 2018, 05:18:57 PM
And here is a standard "roundabout is better - it has less conflict points" pic:

Roundabouts are sold as having single merge/diverge point... Which is a bit dishonest from my perspective.

Roundabouts do approach that ideal if they are single-lane roundabouts.  Once you start adding lanes, it gets a whole lot messier wrt conflict points.  I'm convinced this has something to do with the heretofore unexpectedly high number of accidents at multi-lane roundabouts that tradephoric has so dogmatically highlighted throughout the life of this thread.

(There have now been more replies to this thread than years since B.C.)
Keep right except to pass.  Yes.  You.
Visit scenic Orleans County, NY!
Male pronouns, please.

Quote from: Philip K. DickIf you can control the meaning of words, you can control the people who must use them.

tradephoric

The SR 161 / Riverside intersection averaged 20 crashes per year before a roundabout was constructed in 2016.  When a complex triple-lane roundabout was being proposed, Jeannie Willis (engineering manager for the City of Dublin) said that the roundabout would reduce crashes.
Quote
"They improve safety.  We will reduce crashes.  It won't eliminate crashes.  The frequency of the crashes will be reduced and the severity will be reduced, of the crashes, meaning the number of injury related type crashes will be substantially reduced."

-Jeannie Willis, Engineering Manager, City of Dublin

Turns out the S.R.161/ Riverside Drive roundabout has averaged 2.5 crashes per week since the roundabout opened in August 2016.  That comes to 130 crashes/year compared to just 20 crashes/year before the roundabout.  That's over a 6X increase in crashes.  This upcoming weekend the roundabout will be closed as the city makes changes and eliminates a circulating lane in the roundabout to simplify operations.  This is what Jeannie Willis is saying about the proposed changes.

Quote"We do anticipate that the decision making for our drivers will get simpler and easier, which should help ease that confusion approaching the intersection... this will improve safety, help improve traffic operations and make the roundabout a little simpler for our northbound drivers,"

-Jeannie Willis, Engineering Manager, City of Dublin

https://abc6onyourside.com/news/local/changes-coming-to-dublin-roundabout-after-several-crashes

I hate to harp on Jeannie Willis, but she hasn't been effective at anticipating crash rates at this intersection in the past.  Will Jeannie Willis claim that the changes are a success if crashes drop from 130 crashes/year down to 80 crashes/year?  She might, but considering that there was only 20 crashes/year before the roundabout was built, crashes have a LONG way to drop to return to pre-roundabout levels.

tradephoric

The 121st roundabout just opened in Carmel at Carmel Drive and Old Meridian Road.  The city posted a youtube video of the grand opening and i decided to leave a comment.  We will see if the City can answer my request or if they just delete the comment.

Quote
Three people have been killed at the 96th and Westfield Blvd roundabout in Carmel over a 10 year period (2 killed on October 1, 2007 and 1 killed on March 17, 2016).  Has there been a signalized intersection in Carmel that has had 3 fatalities over a 10 year period?  I don't care if you got to go back to the 1970s to cite an example... just cite one signalized intersection in Carmel that has had 3 fatalities over a 10 year period.


https://www.youtube.com/watch?v=lOx7i41rKHk

mrsman

Quote from: kphoger on October 15, 2018, 08:13:41 PM
Quote from: kalvado on October 15, 2018, 05:18:57 PM
And here is a standard "roundabout is better - it has less conflict points" pic:

Roundabouts are sold as having single merge/diverge point... Which is a bit dishonest from my perspective.

Roundabouts do approach that ideal if they are single-lane roundabouts.  Once you start adding lanes, it gets a whole lot messier wrt conflict points.  I'm convinced this has something to do with the heretofore unexpectedly high number of accidents at multi-lane roundabouts that tradephoric has so dogmatically highlighted throughout the life of this thread.

(There have now been more replies to this thread than years since B.C.)
I agree.  Just like 4 way stops, they work fine in low traffic, but break down in high traffic.  A signal or grade separation is necessary.

Nexus 5X


jakeroot

Quote from: tradephoric on October 18, 2018, 07:28:47 PM
The 121st roundabout just opened in Carmel at Carmel Drive and Old Meridian Road.  The city posted a youtube video of the grand opening and i decided to leave a comment.  We will see if the City can answer my request or if they just delete the comment.

They won't delete it but they won't answer it. You'd be better off emailing the city or mayor directly.

tradephoric

Quote from: tradephoric on September 03, 2016, 10:35:30 AM
https://www.youtube.com/watch?v=T83ogwpkfLk

Remember this roundabout being proposed for I-35 and 51st Street in Austin?  Well the roundabout fully opened to traffic on June 14, 2018 and TxDOT released a video showing traffic circulating the new circle.  On August 1, 2018 TxDOT released another video of the roundabout in action and it appears that it has already been downsized from a 3x2 roundabout to a 2x2 roundabout (the spiral inner lane has been striped out).  I couldn't find any articles explaining why the roundabout was restriped but here are the videos TxDOT released:

https://www.youtube.com/watch?v=yuz33HHpq-A

https://www.youtube.com/watch?v=FW98z5LtylU



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