Are roundabouts an urban or suburban technology?
(The program sure is "neoliberal" in how it stresses technological solutions and the negatives of regulation. And there sure isn't much opportunity to delve very deeply into any of the issues presented) One of the people presenting at the Post conference is talking about the time wasted by queuing at intersections. He lives in a smaller town.
He suggests that compared to traditional intersections, roundabouts work better in terms of faster throughput and increased safety. Roundabouts are intersections that are made into circles, where for the most part, entry roads into the circle are not signed or signalized or are signed with yield signs.
In DC, we have both traffic circles and roundabouts. Traffic circles are not roundabouts because they have traffic signals. Examples of a traffic circle would include Dupont Circle, Chevy Chase Circle, Washington Circle, Logan Circle, or Thomas Circle.
Sherman Circle, Washington, DC
Roundabouts that you think are traffic circles but isn't because there aren't traffic signals, only yield or stop signs, are Grant Circle and Sherman Circle in the Petworth neighborhood. There is a more true "roundabout" in terms of size on Brentwood Road NE.
Brentwood Road NE roundabout
I use these roundabouts regularly and as a pedestrian and cyclist, I find that roundabouts are designed to prioritize vehicular traffic rather than to balance the needs of pedestrians and cyclists with the desire of motor vehicle operators to move quickly.
I rarely feel comfortable going into a circle as a bicyclist because most of the motor vehicle operators don't signalize if they are turning, and in terms of entry, often I have to move to the leftmost part of a lane to ward off traffic coming behind me.
NotionsCapital calls our attention to a couple pieces on the topic, "They're Small But Powerful," from the FHWA magazine Public Roads, and "Evaluating pedestrian and bicyclist risk in Minnesota roundabouts" from the University of Minnesota Center for Transportation Studies (which is a great resource).
The UMN study finds that all is not peachy for pedestrians and cyclists with roundabouts, although the study city in the City of Minneapolis had a greater rate of vehicles yielding to pedestrians and cyclists compared to the suburban site. From the article:
The research team identified several factors that influence drivers’ yielding behavior. Study results indicate the following trends:
- Drivers are more likely to yield to pedestrians or bicyclists beginning their crossing in the center island.
- Vehicles exiting the roundabout are less likely to yield than those entering it.
- Drivers are more likely to yield to larger groups.
- Vehicles entering the roundabout at the immediate upstream entrance are more likely to yield than those coming from other entrances.
- Drivers are less likely to yield if they encounter another vehicle merging into the roundabout immediately before the exit where the pedestrian is trying to cross.
- Yielding probability decreases with more vehicles present in the roundabout.
Note that the Florida DOT report Roundabouts and Access Management has a review of the literature that goes beyond the above-cited publications.