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Ken Johnson, John Gorder, and Brian Malm.

U grads and roundabout advocates Ken Johnson (left), John Gorder, and Brian Malm (seated).

The benefits of going in circles

By Darlene Gorrill

December 13, 2005

In March, three recent graduates of the University of Minnesota's Infrastructure Systems Engineering (ISE) master's program appeared before the Mahtomedi Planning Commission to share information about a common passion--the advantages of roundabouts as an alternative to traditional traffic intersections.

Ken Johnson, John Gorder, and Brian Malm are making impressive headway in increasing awareness about roundabouts in the transportation community and in paving the way for construction of roundabouts. Popular in Europe, roundabouts come in different sizes, depending on traffic volumes. Minnesota has only a few roundabouts. The state's first roundabout was constructed in Rochester in 1998, and its largest is located south of the Twin Cities on I-35 near the Medford Outlet Mall.

"Modern roundabouts, when designed and implemented properly, can have substantial safety and traffic operation benefits," says Malm, a project manager for the consulting engineering firm Bolton & Menk, Inc. "A March 2000 study by the Insurance Institute for Highway Safety of 24 intersections in the United States that were converted to modern roundabouts showed a 40 percent reduction in all crashes and a 70 percent reduction in injury crashes. Those are significant numbers."

A roundabout works on a simple concept: Instead of an intersection with signal lights, drivers from all intersecting streets yield to traffic in the roundabout, entering the circle only when traffic allows. Traffic in the roundabout moves freely without interruption, counterclockwise around a center island. No parking is allowed in the roundabout, nor are pedestrians allowed to cross to the center island.

Since all vehicles travel in the same direction around the center island, traffic paths don't cross, helping dramatically reduce the number of serious crashes, says Johnson, a project manager at the Minnesota Department of Transportation (Mn/DOT) Metro Division. Roundabouts are also designed for traffic to slow to 15 to 20 miles per hour, which gives drivers more time for decision-making. Additional studies show that in many cases, drivers encounter less delay in roundabouts than in traditional intersections with stop signs or lights, adds Johnson.

He discovered his first roundabout on a trip to Ireland, and it was love at first drive. When he joined the ISE program in the Center for the Development of Technological Leadership at the U's Institute of Technology, Johnson found an ideal place to explore the advantages of roundabouts in greater depth.

"[A study] of 24 intersections in the United States that were converted to modern roundabouts showed a 40 percent reduction in all crashes and a 70 percent reduction in injury crashes," says Malm.

As part of an ISE course, Johnson developed a computer analysis tool to help engineers determine the types of intersections best suited to roundabouts and the impact of the roundabout design on traffic patterns. When it came time to consider a capstone project (the final course that requires the student to integrate everything he or she has learned in the program with their job experience), Johnson knew he wanted to continue exploring roundabouts. It wasn't long before he found two colleagues who also wanted to know more.

The group produced a description of roundabout features and benefits, guidelines for selecting intersections for roundabout consideration, a list of intersections that would make good candidates for roundabout installation, and actions--such as an awareness campaign, ongoing education, and evaluation studies--to increase acceptance and encourage implementation of roundabouts.

The project serves as a reminder to consider alternatives, says Gorder, an assistant city engineer for the city of Eagan. "The solutions to engineering problems aren't always the 'tried-and-true' methods, but there are alternatives," he says. "The solutions also don't have to be high-tech. Sometimes simple geometry and alignment are all that's needed."

Thanks to their efforts, interest in roundabouts is increasing in Minnesota, with new plans to add roundabouts or at least consider them. The city of Eagan, in conjunction with Dakota County, is considering a roundabout as a solution to an over-capacity intersection in Eagan. Mn/DOT is including a roundabout as part of a construction project for Highway 610 in Maple Grove. It also has begun developing official guidelines for roundabouts to help designers determine when best to use roundabouts and how to design them. And the Department of Public Safety included a section about driving in roundabouts in its recent drivers' guide edition.

The team has also presented their findings to the Minnesota Public Works Association, the Minnesota City Engineers Association, and the American Society of Civil Engineers.

"My knowledge of how [roundabouts] worked and their benefits was limited," says Malm. "Since we started this project, I've learned enough to know that as engineers, we would be foolish to ignore the benefits of roundabouts."