The Project for Public Spaces has a post on their blog today about modern roundabouts. Being from Cape Cod, the home of the rotaries from hell, I’ve been slow to come around to the idea of roundabouts (which are actually different from rotaries). I’ve spent too many hours of my life on the Airport Rotary in Hyannis or the Mashpee Rotary (or every other rotary on the Cape) yelling at the tourist from maude knows where who keeps stopping on the rotary. The rotaries we see on the Cape and some other areas are however a different beast from the modern roundabout. Rotaries are basically big highways set in a circle designed to quickly spin traffic around and shoot it out in different directions, roundabouts are much smaller and designed to make traffic flow smoothly, but actually have the idea of slowing traffic at their core.
PPS cites the Washington State Department of Transportation about the safety benefits of roundabouts versus signalized intersections:
1) Low travel speeds – because drivers must yield to traffic before entering a roundabout, they naturally slow down, 2) no red lights to run – roundabouts are designed to keep traffic flowing without requiring vehicles to stop, so the incentive for drivers to speed up to make it through a yellow or red light is removed, and 3) less potential for serious crashes – since vehicles all travel around the center island in the same direction, head-on and left-hand turn (T-bone) collisions are eliminated.
One concern I have about roundabouts is how they work for pedestrians. Below is a video from the Mayor of Carmel, Indiana explaining the benefits of roundabouts in his community. He has some comments on the benefits to pedestrians.
In the video, the Carmel Mayor cites the reduced traffic speed as a safety feature for pedestrians. I suppose if I were to be hit by a car, I’d prefer to be hit by one slowing to navigate a roundabout rather than one speeding to make it through a yellow light. I think I’d prefer to just not be hit though. Looking at the geometry of a roundabout, I’m concerned about crossing the roundabout exit. How is a pedestrian to judge if a vehicle is staying in the roundabout or exiting to where she is trying to cross? Ideally the vehicles exiting would signal such (that is what you are supposed to do on a rotary so traffic entering can know you are leaving), but this is Rhode Island, we may need an 8 week course to show drivers where their turn signals are.
The Carmel roundabouts have a recessed crosswalk (i.e. set back from the actual intersection) with a center median serving as a pedestrian refuge. This arrangement does not address slowing traffic exiting the roundabout to allow for pedestrian movement. One tool that could be used to slow traffic exiting the roundabout is the use of raised crosswalks.
Most of us are aware of the giant mountain on Smith Street at the State House, this is a somewhat extreme example of a raised crosswalk. At the other end of the scale, we have some raised crosswalks in Kennedy Plaza that barely even register with drivers. A raised crosswalk should force drivers to slow somewhat, but not force them to come to a complete stop if there are no pedestrians in the crosswalk.
Another concern for roundabouts is how bicycles would navigate them. Traffic slows enough to navigate a roundabout that it comes down to bicycle speeds, allowing bicycles to move into traffic and use the roundabout just as a car would. This video from the New York State Department of Transportation shows this:
While most roundabouts in the US are being built in suburban areas, in Europe roundabouts are used in urban areas like Providence. Do you think roundabouts are a traffic measure that should be explored for Providence? Where would you propose roundabouts should be installed here?