Circular infrastructure

[finehoe]

Circular infrastructure
What goes around
Learning to yield
Nov 19th 2011 | CARMEL, INDIANA |

“I MEAN, it’s round, how difficult can it be?” asks the front-desk attendant at the Renaissance Hotel in Carmel, exasperated, when asked whether visitors struggle to navigate the town’s many roundabouts. Carmel, just north of Indianapolis, has 70 of themâ€"more than any other city in America. But while locals love them for their speed and efficiency, visitors are apprehensive. One recent out-of-towner was so terrified by the strange formations that he preferred to travel by taxi.

The mayor, Jim Brainard, built the first roundabout in Carmel in 1997 after seeing them in Britain. Instead of a four-way intersection with traffic lights, a circular bit of road appeared. It was so successful that today Carmel is the roundabout capital of America, and the mayor plans to rip out all but one of his remaining 30 traffic lights.

The modern, safe roundabout first entered service in Britain back in 1966, after it adopted a rule that at all circular intersections traffic entering had to give way, or “yield”, to circulating traffic. This innovation, along with the sloping curves of the entry and exit of a roundabout (which slow traffic down), created a design that is now found worldwide. Though tens of thousands of roundabouts exist across Europe, America still has only 3,000 of them.

One of their main attractions, says Mayor Brainard, is safety. The Insurance Institute for Highway Safety, an independent research group, estimates that converting intersections with traffic lights to roundabouts reduces all crashes by 37% and crashes that involve an injury by 75%. At traffic lights the most common accidents are faster, right-angled collisions. These crashes are eliminated with roundabouts because vehicles travel more slowly and in the same direction. The most common accident is a sideswipe, generally no more than a cosmetic annoyance.

What locals like, though, is that it is on average far quicker to traverse a series of roundabouts than a similar number of stop lights. Indeed, one national study of ten intersections that could have been turned into roundabouts found that vehicle delays would have been reduced by 62-74% (nationally saving 325,000 hours of motorists’ time annually). Moreover, because fewer vehicles had to wait for traffic lights, 235,000 gallons of fuel could have been saved.

http://www.economist.com/node/21538779/print

[thelakelander]

Their interchanges are pretty interesting.  I can see how it would take outsiders sometime to get used to.

[Charles Hunter]

I wish pedestrians would not cross the middle of the roundabout at the Landing.  Pedestrians are supposed to cross at the marked crossings on the legs.  And I wish the one in front of MOSH was a real roundabout - without those stupid stop signs.

[Non-RedNeck Westsider]

I thought those stop signs were left over from the old intersection.   

[Non-RedNeck Westsider]

Without 4 way stops, where are they going to put thier Family Dollar, Gate stations & Walgreens?

[Dog Walker]

Their interchanges are pretty interesting.  I can see how it would take outsiders sometime to get used to.

Lake, what do you call that thing?  It's not a roundabout, maybe a bow-tie intersection/overpass?  Confusing, but look how efficient.

[tufsu1]

it is an elongated roundabout....we are working on a similar concept for an area in Tallahassee....based on Campus Martius in Detroit

[urban_Savvy]

Elongated roundabouts and standard roundabouts are a terrific idea and need to be emphasized on the menu of American transportation infrastructure options. Beyond perception, a minor but significant hinderance is the lowering of standards in driver's education courses nationwide.  In most cases, these programs favor teaching typical suburban driving behavior over urban considerations. In many states, a driver does not need to be pass a basic parallel park test just to name an example. My point in all of this is we need to start teaching roundabout driving and raising licensing standards if we hope to see it implemented more on a wide scale.

[tufsu1]

Not that I'd put this on the same level, but check out the concept of divergent diamond interchanges....

basically, it minimizes the conflict points and signalization needs for left turns....which means fewer lanes (and in theory easier to cross for peds).

http://en.wikipedia.org/wiki/Diverging_diamond_interchange

[dougskiles]

My personal experience with roundabouts in Spain was that they are great in rural and suburban areas (although it takes some time to get used to).  They are treacherous in urban areas - and very pedestrian unfriendly.

[tufsu1]

My personal experience with roundabouts in Spain was that they are great in rural and suburban areas (although it takes some time to get used to).  They are treacherous in urban areas - and very pedestrian unfriendly.

agree that they work best in lower traffic situations....if traffic is too heavy, cars can never get into the roundabout...for those situations, either single point interchanges or diverging diamond interchanges are probably the way to go

[Kay]

I'm with Doug in that they are not friendly to pedestrians if what they do is move cars through intersections faster.  We need to be more pedestrian friendly, not less.  Although roundabouts may be preferred over lane expansion and road widening. 

[Dog Walker]

Don't confuse roundabouts with rotaries or traffic circles. 

Roundabouts are the small, low speed circles of the type we have on Laura St.  They aren't bad for pedestrians since the entering traffic has to yield to both traffic in the roundabout and to pedestrians. In very heavy, urban traffic situations they can be signalized for pedestrians and bicycles.  They do this in the Netherlands.  Signals go on and all motorized traffic stops and bicycles and pedestrians cross in all directions.

Traffic circles are those huge circles like the one that the Arc de Triomphe sits in in Paris.  They are high speed and absolutely terrifying!  A lot of European countries have them and put monuments in the middle.  I think they were designed when all traffic was horse drawn and slower.  Incoming traffic has the right-of-way, not the traffic in the rotary.  Just the opposite of roundabouts. 

Rather than going to an amusement park ride to get scared out of your mind, you can just take a taxi ride across Paris or Rome!  Take a change of undies.

[Non-RedNeck Westsider]

I came across this one in my interweb travels today.  Please explain....
http://binged.it/zvby36


If someone can post the pic, I'd appreciate it.

[fsquid]

It's Swindon, they are just fecked up to begin with.