Roundabouts

[roadfro]

Where did I say anywhere that traffic in the circle yields?  I was referring to traffic entering the circle, not leaving it.  You can't turn into and inside lane from an inside lane if the lane outside of the one you are turning into is occupied and that's pretty much the case.

I misinterpreted your first response...my apologies.

However, if I'm understanding what you wrote, the first part of your comment isn't always correct. Entering vehicles should to yield to all vehicles in any lane of the circulatory roadway--especially since all roundabouts are not marked the same, and few drivers actually signal their intent to exit a roundabout.

Say a driver is heading northbound towards a 4-leg roundabout approaching from the outside lane.  When that driver reaches the yield line, there's a car coming in the inner circulating lane at the same time. If the driver in the inner circulating lane wants to exit on the east leg of the roundabout, the northbound driver cannot enter  simultaneously, because their paths will cross at the eastbound exit (resulting in a sideswipe collision). The northbound driver has to wait for the circulating vehicle to clear the conflict point before entering the roundabout.

[golden eagle]

I love roundabouts. I wish there were more roundabouts. I wish idiot Americans would stop complaining about roundabouts and actually take the time to learn how to properly navigate them.

And as for this near accident, was it you or the other guy that was in the roundabout? did someone not give way to the person inside? what happened?

I was trying to go north and was in the right lane, the other driver was in the left lane trying to go east.

[hbelkins]

The term "traffic circle" is not synonymous with the term "roundabout".

To me it is... 

[deathtopumpkins]

Case in point of roundabouts that don't work--the two rural roundabouts that Washington County, Oregon's Department of Land Use and Transportation (DLUT) installed in 2003 on NW Verboort Road, a major arterial north of Forest Grove that forms part of a link between OR-47 and US-26.  The accident statistics released by the county to the Rural Roads Committee in 2008 showed negligible improvements.

Were those two roundabouts originally proposed to be multilane ones? The markings seem to indicate such.

The intersection in the middle has a roundabout, but this is a very light intersection and is more decorative than functional.  There's more landscaping there now than Street View shows and I've never had a problem with it.

Interesting. A 2-way stop with a roundabout.



Here they installed recently the first roundabout in Hampton Roads that I am aware of on a public roadway, but it is pathetic. All they did was take an existing 4-way intersection with a 2-way stop and put a small circular plastic curb in the middle, and remove the stop signs. It is rather pointless as there is not much traffic and it is ineffective at slowing down traffic, which was its purpose (it was installed about 500 feet before where Beach Rd. in Hampton ends right at the edge of the Chesapeake Bay--come flying through there and prepare to get wet). And so far it seems to be a waste of money in most regards because, to prevent people from flying through it, they installed those folding plastic pole things along the shoulder line, which are all replaced about every 2 weeks because they get repeatedly flattened.

[SSOWorld]

The intersection in the middle has a roundabout, but this is a very light intersection and is more decorative than functional.  There's more landscaping there now than Street View shows and I've never had a problem with it.

Interesting. A 2-way stop with a roundabout.

That sat image is likely taken before the roundabout was installed.

[UptownRoadGeek]

However, if I'm understanding what you wrote, the first part of your comment isn't always correct. Entering vehicles should to yield to all vehicles in any lane of the circulatory roadway--especially since all roundabouts are not marked the same, and few drivers actually signal their intent to exit a roundabout.

You're right as far safety/legal standpoint, but in the city a lot of times the defacto rule is "get in where ya fit".  Sit and wait for all lanes to clear and you'll probably never get in and in the process be cursed out, have something thrown at you, or in rare cases shot at.

I know it's dangerous, but it is what it is.

[roadfro]

The intersection in the middle has a roundabout, but this is a very light intersection and is more decorative than functional.  There's more landscaping there now than Street View shows and I've never had a problem with it.

Interesting. A 2-way stop with a roundabout.

That sat image is likely taken before the roundabout was installed.

The Street View clearly shows stop signs on two approaches 

[deathtopumpkins]

The intersection in the middle has a roundabout, but this is a very light intersection and is more decorative than functional.  There's more landscaping there now than Street View shows and I've never had a problem with it.

Interesting. A 2-way stop with a roundabout.

That sat image is likely taken before the roundabout was installed.

I was referring to the streetview.  The satellite view doesn't show the roundabout at all.

[SSOWorld]

That sat image is likely taken before the roundabout was installed.

I was referring to the streetview.  The satellite view doesn't show the roundabout at all.

Ah - forgot to look down - doesn't look like a true roundabout for sure.  if anything that was hap-hazardly put together by the local street department 

[J N Winkler]

The term traffic circle is deprecated in relation to circular intersections which operate to a yield-on-entry rule because it is also used to refer to circular intersections where traffic in the circle does have to yield to entering traffic, like at the Arc de Triomphe in Paris.

There are also presentational advantages in differentiating between roundabouts and traffic calming circles.  Roundabouts are specialized to handle balanced traffic flows more efficiently and safely, with shorter queues and less waiting time, in comparison to traffic signals.  In fact, the standard recommendation nowadays (in many jurisdictions) is to use traffic signals only in constrained locations, to handle severely unbalanced flows, or when the overall volumes would cause a roundabout to "lock up" but system considerations militate against grade separation.  Traffic calming circles are a different animal altogether--they usually try to reduce traffic speeds in residential neighborhoods by leaving the existing curb returns unrevised while replacing part of the circulatory area in the intersection with an island.

In general, I believe it is a mistake to introduce roundabouts and traffic calming circles at the same time in a community which is naïve to both, and in general to design roundabouts with crossfall in the circulatory carriageway so steep that they come across more as traffic calming devices than as a different form of intersection control.

[Scott5114]

I think a reason that Americans and roundabouts may not get along so well is because Americans are loathe to yield to anyone. Or is that just Oklahomans (somehow I doubt that). I doubt most people around here would yield to their own grandmother!

[roadfro]

The term traffic circle is deprecated in relation to circular intersections which operate to a yield-on-entry rule because it is also used to refer to circular intersections where traffic in the circle does have to yield to entering traffic, like at the Arc de Triomphe in Paris.

There are also presentational advantages in differentiating between roundabouts and traffic calming circles.  Roundabouts are specialized to handle balanced traffic flows more efficiently and safely, with shorter queues and less waiting time, in comparison to traffic signals.  In fact, the standard recommendation nowadays (in many jurisdictions) is to use traffic signals only in constrained locations, to handle severely unbalanced flows, or when the overall volumes would cause a roundabout to "lock up" but system considerations militate against grade separation.  Traffic calming circles are a different animal altogether--they usually try to reduce traffic speeds in residential neighborhoods by leaving the existing curb returns unrevised while replacing part of the circulatory area in the intersection with an island.

In general, I believe it is a mistake to introduce roundabouts and traffic calming circles at the same time in a community which is naïve to both, and in general to design roundabouts with crossfall in the circulatory carriageway so steep that they come across more as traffic calming devices than as a different form of intersection control.

Spot-on descriptions.

"Traffic calming circles", as used in residential neighborhoods, can be a great way to reduce speeds--I much prefer these over unwarranted two-way or four-way stop signs.  I've also heard the term "mini roundabout" used professionally to describe these.

My understanding is that traffic circles are being gradually phased out in many areas, in favor of roundabouts or other controls.  In my personal opinion, it would be a mistake to introduce traffic circles anywhere in the U.S. that doesn't already have them...and it's better to just not construct new ones at all. Seeing some of the circles in Washington DC in action a few years ago really made my head spin--definitely some complex signal timing involved to make sure those don't jam up.

I believe the cross slope of roundabouts is generally designed to be around 2%, which is the standard crossfall of a typical roadway.

[Terry Shea]

I don't know, maybe they make sense in some areas but the ones I've seen do nothing to alleviate traffic tie-ups, confuse the drivers causing more accidents and are nothing but a big waste of money!

Do you have a cite that supports this? I've seen some DOT statements that say roundabouts generally improve safety. I'd be interested to see how the costs and benefits of roundabouts work out as well.

Well the only experience I've had with them is the 2 that I mentioned previously.  The one that receives too much traffic is the one at the intersection of 3 Mile RD and Dean Lake Ave in Grand Rapids Twp.  Traffic gets backed up as far as the eye can see in all directions during rush hour.  It did when it was a 4-way stop and it still does now.

The other one is in front of a retirement home on Pfeiffer Woods Dr in Kentwood.  It's not even at the main entrance to the home but at a service drive!  And I'm betting that large service vehicles making deliveries are going to have trouble negotiating the tight sharp turns.  (Kentwood has also been turning their busy streets into boulevards with Michigan left turns and they didn't design most of them with enough room for a semi to negotiate the left turn.)  Like I said there is absolutely no reason for a roundabout, traffic signal or stop sign here because there is absolutely no traffic on this road.

Both of these projects were a total waste of money.  The one doesn't do the job it was designed to do because traffic is still log jammed and the other serves no purpose whatsoever, accept for making it difficult for delivery trucks to enter the service drive.