Auto and Road User  Journal
Auto and Road User Journal
October 15, 1997
TranSafety, Inc.
1-800-777-2338
(U.S. and Canada)
(360) 683-6276
Fax: (360) 335-6402
transafety@live.com

Traffic Circles and Rotaries Slow Speeders and Expedite Traffic

(summarized from "Crossroads," the newsletter of the Transportation Information Center at the University of Wisconsin--Madison)

Across the United States, alternatives to traditional intersections are helping motorists move safely and efficiently through intersections. Traffic circles in Seattle, Minneapolis, and Madison are an old-fashioned idea that is making a comeback in efforts to slow speeding motorists in residential neighborhoods. In Sheboygan, Wisconsin, an oval-shaped exchange called a rotary allows a busy five-leg intersection to move traffic smoothly and efficiently.

Traffic Circles

Traffic circles are 12 to 20 feet in diameter, and they are formed with curved curbing. Placed in the middle of residential intersections, they are landscaped with low-growing shrubs and flowers. Studies have shown they cause motorists to reduce their speed when driving through residential neighborhoods. Emergency vehicles, school buses, garbage trucks, and snow plows must also slow, but they can easily negotiate the traffic circles. In some communities, using mountable curbs for traffic circles facilitates getting moving vans into and out of housing areas.

Cities find most neighborhood residents like the addition of traffic circles to their intersections, while many drivers "think you're nuts." Seattle requires 60 percent of all households and businesses in a neighborhood to support a request for a traffic circle, and they still have more than 700 requests coming in each year. Neighborhoods are actually competing to have traffic circles installed.

Rotary

Sheboygan was confronted by a major five-leg intersection with increasing traffic volumes due to new harbor development. They could find no way to control the intersection with signs or lights, and they decided that a modified rotary design would be the best solution. Despite tight time lines due to the opening of a nearby bridge and a related soil-contamination cleanup, they went ahead with the rotary. After more than two years of operation, they are finding the rotary works even better than Department of Public Works staff had hoped.

The oval is 240 feet by 140 feet and is never less than two lanes. Stop or Yield signs confront entering vehicles, while traffic on the rotary has right-of-way. In 1994, traffic counts at this intersection were 16,200 vehicles per day, and the city projects 23,800 vehicles per day by 2015. The city feels it has found an effective, attractive solution to an increasingly difficult traffic problem.


Traffic circle in a Seattle residential neigborhood



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