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Coming to a Streetcorner Near You: Roundabouts!
Kentucky Transportation Cabinet has changed its policy (2p pdf) to cautiously endorse Modern Roundabouts. The Modern Roundabout is an intersection technology like "4-way stop" and "stop lights". However, in some places it will outperform these older technologies in almost every way.
Says "Making Places":
It turns out that roundabouts may be part of the panacea for our greatest traffic woes. Across America, towns and cities of all shapes and sizes have been choosing modern roundabouts over antiquated signalization equipment and expensive grade separated interchanges. The choice of a roundabout, or a modern roundabout, rather, makes sense for several reasons: they have proven to improve the flow of traffic, reduce cost, improve safety, and enhance the quality of place.
The roundabout in the video is right here in Kentucky, at Norton Commons. I rode it and it was a lot of fun. I'm so well-trained to STOP at intersections, it took concious effort to roll through the YIELD sign the first few times. The biggest revalation was just how relaxed everyone was about driving there. There were no Leadfoot Louies gunning it for the lights.
Read More to Learn Why is there no Truck in this picture!
Because the Driver was so 'traffic calmed' he was yielding to my photography Line of Sight! I had to wave him through. Compare that to a crosswalk, where Louisville motorists very agressively fume at having to wait for 'unexpected' pedestrians. Engineering matters.
Comments
Roundabout
How many lanes can feed it? What is the speed limit of the access roads? At what point do you switch to stop lights?
Two lanes, Four lanes
With no additional driver training, any driver can have a go at a roundabout at the juntion of 2-lane roads. They're just Yield signs, which in theorey people understand. Though the first time through it feels wierd, then it becomes normal very quickly.
Here is a nice animation on how a bigger roundabout, serving a 4-lane road and a 2-lane road, would work. Notice how interactive it is, how trucks and cars are supposed to perform differently, and in general how much more training it takes. KYTC has wisely, in my opinion, decided to keep the bigger roundabouts sidelined until Kentuckians build up a basic understanding of the normal ones.
What makes a roundabout "modern?"
What was the "old fashioned" kind like?
modernism
Each road feeding into the roundabout has a traffic island in the middle as a ped shelter. This makes walking across much less challenging for those of us who can't see 360-degrees.
Yield signs, not stop signs, are essential to getting traffic throughput. Putting stop signs in ruins the whole thing.
Also, my guess is that archeo traffic circles operated on the "more pavement is better" principle. That's certainly the case at the Castleman and Daniel Boone traffic circles near Cherokee Park. Modern roundabouts constrict the space to force people to focus on what's important - not hitting eachother. This is particularly important for bicyclists, who otherwise would tend to the outer rim of the roundabout, where they're invisible.