A September 10 Sustainable City Network article examined how traffic roundabouts can reduce serious traffic accidents, improve traffic flow, lower gas and infrastructure maintenance costs, encourage business/economic development, and minimize environmental impacts. The article cites Federal Highway Administration (FHWA) findings that roundabouts reduce severe crashes with injuries or fatalities by 82 percent vs. intersections with stop signs and 78 percent vs. intersections with traffic signals. The article also distinguished roundabouts from older traffic circles:
[FHWA Intersections Program Manager Jeff] Shaw explained that roundabouts differ from traffic circles and rotaries that have been around for many years prior to 1990.
“Modern roundabouts have three characteristics that rotaries and traffic circles (like the eight-lane circle in Paris around the Arc De Triomphe) do not generally have: (1) all traffic travels counterclockwise around a central island, (2) entering traffic yields to circulating traffic and (3) geometry that results in low vehicle speeds (generally ranging from 15-25 mph),” Shaw said. “Additionally, weaving or lane changing is eliminated with a multi-lane modern roundabout design.”
The article also cited a 2014 Indianapolis Star column by Carmel, Indiana Mayor Jim Brainard on the benefits of roundabouts:
• Safety: “Roundabouts virtually eliminate deadly head-on collisions and T-bone crashes. All motorists, not just those who see a red light, are forced to slow and yield as they enter the roundabout, making it less likely that an accident will occur. ….”
• Cost: “Roundabouts save an average of 24,000 gallons of gas per year, per roundabout (based on a 10-site study by the Insurance Institute of Highway Safety). … Roundabouts not only save money when it comes to purchasing gasoline, they are also cheaper to build and maintain. When improving a troubled intersection, cities and towns can save about $150,000, which is the cost of a traffic signal. Thousands of dollars per year are saved by not having to provide electricity to the signal, as well as the cost of maintenance.”
• Traffic flow: “Roundabouts improve the daily flow of traffic by eliminating congestion and the long backups that often plague busy stop sign or stoplight intersections. Typically, the maximum capacity of a four-way stop is about 1,500 vehicles per hour. A single-lane roundabout, on the other hand, has a capacity of 2,500-2,800 per hour, an increase of 65-90 percent in capacity. ….”
Brainard also discussed the environmental, traffic calming, and economic development/business benefits of roundabouts in the article.