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Road Engineering Journal
September 2, 1997
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Rotary Intersection a Winner
Circles Slow Speeders on Residential Streets
National Cooperative Highway Research Program Synthesizes Research on Changeable Message Signs (CMSs)
Survey Finds State DOTs Feel Biodiversity is a New Issue in Transportation Development Projects

Highway Safety Publications Catalog. Articles on Road Engineering, Road Maintenance & Management, and Injury Litigation. Information and consulting for the Automobile and Road User, as well as for law professionals in accident investigations.
TranSafety's free consumer journal for automobile and road users, three subscription journals on road maintenance, engineering, and injury litigation, and highway safety publications catalog. See our free consumer journal for automobile and road users, three subscription journals on road maintenance, engineering, and injury litigation, and a highway safety publications catalog.


Circles Slow Speeders on Residential Streets
In a Spring 1997 "Crossroads" article, the Transportation Information Center at the University of Wisconsin-Madison described how traffic circles are returning to residential streets as cities rediscover this attractive traffic-calming method. The following is a reprint of that article.

An old-fashioned idea is making a come-back on neighborhood streets in Seattle, Minneapolis, and Madison. These cities are planting small circles in residential street intersections to slow down traffic.

Traffic circles are 12 to 20 feet in diameter, depending on street width and intersection radius. Formed by curved curbing, they are usually landscaped with low-growth vegetation. While all drivers must slow down to negotiate the circle, fire trucks, emergency vehicles, school buses, garbage and recycling trucks, and snow plows negotiate them easily.

Seattle, which now has more than 600 circles, has seen lower vehicle speeds and fewer accidents because of them. Neighborhoods there are competing to have circles installed, with more than 700 requests coming in each year. The city has developed selection criteria emphasizing strong community support (60% of all households and businesses in the area). The request must also satisfy a traffic safety analysis based on collision, volume, and speed data.

Minneapolis has also adopted the idea, with two traffic circles in place and 32 more being tested. About 28 will be made permanent this summer. "It improves the esthetic quality of the street. And drivers see greenery instead of a long strip of asphalt enticing them to speed," says Mike Monahan, Minneapolis Director of Transportation.

Testing Proves They'll Work

In Minneapolis, each circle gets a two-season experiment (fall-winter or winter-spring) using portable curb with flower planters inside. This allows residents to try out the circle in their neighborhood before much money is spent. A formal safety test for service vehicles involves videotaping each one going through the intersection. Their cost to install a circle is under $3500 plus $1500 for the test.

Snow plow drivers have to learn how to clear the roadway around the circles on their routes, which takes a while. With this year's [1996-97] heavy snows, Minneapolis is plowing more intensively around traffic circles to ensure that fire trucks can pass easily.

"This is the third winter and plow drivers are finally speaking to me again," says Monahan. "They admit that the circles are not so bad after all." Speeds on neighborhood streets are definitely lower, but traffic volumes are down only two to five percent. Monahan attributes the reduction to through traffic leaving residential streets and returning to arterials.

Residents Must Want Them

Neighborhood support is critical. "People either like them or they absolutely hate them," says Monahan. Even though traffic turning left may either turn in front of the circle or go around it, the disruption can produce negative reactions from neighbors, he says.

In Madison, the circles are a focal point for a new, neighborhood traffic planning initiative, says City Traffic Engineer David Dryer. "We have a neighborhood with documented traffic problems and they are willing to work with us as an organization." He hopes to install the first test circle in late summer.

Dryer had experience with traffic circles in Mobile, Alabama, where he worked until last year. "We had 20 there, and quite a bit of controversy," he says. "Drivers think you're nuts but residents like them."

Madison plans to use a mountable 30-inch curb for its permanent traffic circles to allow a moving van to easily negotiate the intersection, even if it can't quite make the circle. Neighborhoods will be responsible for maintaining low shrubs and flowers inside the circles.

Speeding is a problem on every street, and we're really hand-tied as to what works to get motorists to travel at lower speeds," Dryer says. Traffic circles and other traffic calming devices are widely used in Germany and the Netherlands where they seem to be effective and well-liked.

(Reprinted with permission from the Spring 1997 "Crossroads," newsletter of the Transportation Information Center at the University of Wisconsin--Madison)



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