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PRO roundabout editorial

JNA

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#1
From the Indianapolis Star:
Safe and round

The latest fashion in road design, roundabouts, is starting to appear in significant numbers in Indiana. Carmel has completed dozens of them and has more planned. Avon, Bloomington and Fort Wayne have embraced them.

Numerous studies show that roundabouts can reduce the number and severity of accidents. They also move traffic through intersections faster than stoplights or stop signs. But they are creating controversy and confusion among motorists unused to navigating circular intersections. If not properly designed, roundabouts can cause accidents and delays.

That's why Indiana lawmakers, as well as state and local highway planners, need to standardize the design. They also need to mount a campaign to educate Indiana drivers on how to drive through roundabouts.

Carmel has discovered that proper design and good signage are essential.

Studies show that while drivers initially resist roundabouts, their acceptance rapidly increases as they get used to navigating them.

Consistency of design, understandable instructions and driver education are essential if roundabouts are to work. Everyone needs to know what to expect.
Nice simple to the point - design, sign, and educate.

Does anybody's State Driver Manual address how to drive in a roundabout ?

Is there a resurgence in constructing roundabouts
or
is Indiana just now catching up with "latest fashion in road design" that everybody else has known for a long time ?
 

Chet

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#2
I think there is a reluctant resurgance. Our state DOT has installed quite a few, as have some of the local cities that are large enough to have transportation planners on staff.
 

jhboyle

     
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#3
We are reviewing several possible locations in our county right now, they seem safe, I read an article somewhere receintly about one in Maryland that ruduced congestion by 70%
 

Tide

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#5
Luca said:
what are the shortcomings of roundabouts (beyond any local lack of experience?)
Volume & capacity limits. As volume exceedes a certain amount they become a traffic nightmare and accident potential goes way up. Now, coming from NJ I am used to "circles" which are large roundabouts. There used to be a circle in Ledgewood, NJ that had an accident a day there. It has been replaced with a triangle.
 

Gedunker

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#6
Tide said:
Now, coming from NJ I am used to "circles" which are large roundabouts.
Both JNA and I are NJ natives, so we know circles. I used to navigate the Rts 22/202/206 circle in Somerville regularly. There were a number of businesses, including a diner, with direct access onto the circle (with continuous curbcuts to boot). It's a wonder to me that there were not more accidents there, but perhpas the utter confusion and fear trying to figure out where you were going actually worked to make the thing safer than it really was. I do remember times when I tried to go through the circle as fast as I possibly could, but I was a reckless youth in those days. In that, though, I hardly think I am unique.

It is timely that you post this thread. A major economic development coup for our fair city will bring our first three roundabouts to town. I'm looking forward to seeing how they act as far as traffic calming.
 

wahday

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#7
Albuquerque is preparing to install a few pilot project roundabouts and has put in place smaller traffic circles on some residential streets. So far, so good, and the public seems to like them too.

Personally, I like roundabouts for a number of reasons. They keep traffic moving, reduce cut-through traffic on side streets (which often happens when people are caught at a light), are easy to use (once you have been through them a few times) and without the stop and start traffic, the most harmful car emissions are greatly reduced.

The drawback I see is in retrofitting them to existing ROWs. The diameter of roudabouts increases dramatically in relation to traffic volume. We had the New Urbanist firm Moule and Polyzoides (who I was not particularly fond of for this and other reasons) do an area plan where they recommended a number of roundabouts on one of our busier arterials. Clearly they had not run through the details because when the traffic engineers did the modeling (based on M and Ps data sets for standards), they found that all of the proposed sites would require knocking down buildings to widen the intersections (details conspicuously missing from the report)! Ooops!:p
 
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#8
Tide said:
Volume & capacity limits. As volume exceedes a certain amount they become a traffic nightmare .

This is exactly what has happenedin the community wher I live- they installed some at the busiest intersections and it has become a traffic nightmare. When cars are stopped completely in the roundabout and backed up for hundreds of feet in any direction they lose all functionality.

Additionally, they are not a good choice for areas with a significant population of seniors. Seniors unaccustomed to using roundabouts will have a very very difficult time learing how to use them correctly - creating dangerous situations.
 
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#9
Luca said:
what are the shortcomings of roundabouts (beyond any local lack of experience?)
I'll repeat large volumes - single lane roundabouts are fairly straight forward, dual lane roundabouts start to get interesting, it would be undesirable to add capacity beyond that. Roundabounts often require increased ROW at the intersection when compared to more typical configurations. Cyclist and pedestrian movements can be awkward, but when properly thought out this usually isn't an issue. Large vehicles (especially with trailers) may have difficulty maneuvering around the roundabout.
 

Luca

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#10
So it sounds like roundabouts are a good solution on rural/secondary roads that do not carry massive traffic, in lieu of stops/4-way stops/lights. That seems to be the way they get used in the UK, mostly.

Next question: do large roundabouts that include lights make sense? Isn’t a normal intersection better in that case?
 

jmello

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#11
Luca said:
Next question: do large roundabouts that include lights make sense? Isn’t a normal intersection better in that case?
Well, you are avoiding left turn conflicts and multiple cycles with a signalized roundabout. This type of large roundabout is referred to as a "rotary" in New England.

Edit: IMHO, four-way stops are NEVER a good solution.
 
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Budgie

     
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#12
Hell, even KsDOT are starting to put them in and usually we're the last bastion of "old school" engineering and design. I grew up in England and can remember large roundabouts with as many as 8 exists going to different towns and villages. I also know how to properly signalize as I enter and exit a roundabout.

We've got a small one planned in our TND proposal.
 

Luca

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#13
jmello said:
Well, you are avoiding left turn conflicts and multiple cycles with a signalized roundabout. This type of large roundabout is referred to as a "rotary" in New England.

Edit: IMHO, four-way stops are NEVER a good solution.
Or even 'gyratory systems' as in the dreaded Hanger Lane Gyratory (system)...
 

zman

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#14
We have a few here and I like them. People were reluctant at first, but they seem to be getting good acceptance. Occasionally we'll have someone who cannot navigate the RAB and doesn't think to circle again, thus creating problems, but most of the time, things go well.

The ROW taken for them can be large, but we have been designing projects in order to accomodate this necessity. We even have a plan for out largest intersection (two multi-lane U.S. highways) to be in a "figure eight - dual RAB" THAT should be interesting if it ever gets impemented.

Also, Folks, think about traffic during a power outage. RABs are not affected by such occurance. ;)
 
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#15
zmanPLAN said:
Also, Folks, think about traffic during a power outage. RABs are not affected by such occurance. ;)
And also, think of that 2:wow:0 AM stop when there is no other traffic, but you just sit there because a red light is pointing at you.

I was able to spend a day at a roundabout course a couple of years ago and the guys (Northeast Roundabouts, I think they were called) really sold it. The only thing they could not answer is visualy impaired crossing (since audable signals would be lost).

--Fewer conflict points
--less severe accidents (no "T-Bones")
--Less stop and go (I think 0 to 15 mph acceleration is the most polluting)
--More bike friendly
--More (non-visual impaired) ped friendly
--Usually more attractive
 
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#16
Several have been installed here in NH and importantly, are becoming a default alternative when doing intersection work.

Roundabouts are significantly safer than a signalized intersection and have very few conflict points. I have read that there can be 70% fewer accidents, and those that do occur are generally of a much reduced severity.

They have the benefit of calming traffic - you can't speed up through it to beat the yellow like at a signal.

They should be installed in areas of moderate traffic where all approaches to the intersection are more or less balanced - this isn't critical, but can help maximize the capacity.

They can add beauty to the roadway network with space to plant flowers and greenery.

Bicyclists and vision impaired pedestrians are the ones most likely to be negatively impacted by a roundabout. The cyclists because they are circulating with turning and merging traffic, and vision impaired pedestrians because there are no signals to stop vehicles so that they can cross. Both of these issues can be rectified if they are a concern.

You should check out the FHWA Roundabouts Guide
 
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#17
There are a few in Buffalo, if that's what you want to call some of them now. Gates Circle, Niagara Square (although it does have a signal at a couple of points), North/Porter at Richmond/Allen/etc, Richmond at W. Ferry (although I thought they put stop signs up a while back making the design obsolete), Colonial Circle (need to get rid of the stop signs on that one), Chapin Pkwy at Bidwell, and maybe some others I missed. I thought there was one in South Buffalo on McKinley by South Park.

I remember they were talking about putting one at Elmwood and Forest (not feasible) and one at Elmwood and Rockwell.
 

jmello

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#19
SideshowBob said:
And also, think of that 2:wow:0 AM stop when there is no other traffic, but you just sit there because a red light is pointing at you.
That's why most of our lights go into flash mode in the wee AM hours.

SideshowBob said:
I was able to spend a day at a roundabout course a couple of years ago and the guys (Northeast Roundabouts, I think they were called) really sold it. The only thing they could not answer is visualy impaired crossing (since audable signals would be lost).
I just saw a presentation from a research fellow at UNC regarding a study of this issue. He is using a micro-simulation to test different designs for blind ped crossings at roundabouts. See the second study from the top:

http://www.itre.ncsu.edu/itremain/research/research_list.html#BikePed
 
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