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Michigan’s Next Export: The Michigan Left?

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Signage for a Michigan left turn intersection. Graphic by Christopher J. Bessert via Wikimedia Commons.

Signage for a Michigan left turn intersection. Graphic by Christopher J. Bessert via Wikimedia Commons.

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DETROIT (WWJ) — Traffic engineers at Wayne State University say the median U-turn, which most drivers around here call the Michigan left, has been a great asset in moving traffic safely and efficiently here for more than 50 years. While widely used in Michigan, other states and countries have not adopted it. Wayne State officials say that’s because the design is not included in standard manuals and software that highway designers use.

With the help of a $78,000 grant from Science Applications International Corp., a team led by Wayne State’s Joseph Hummer, professor and chair of the Department of Civil and Environmental Engineering, aims to change that. They plan to develop equations, text and software so that the Michigan left turn and three other alternative designs can be included in the next edition of the Highway Capacity Manual used by highway designers.

According to Hummer, numerous research efforts and publications on alternative intersections and interchanges sponsored by the Federal Highway Administration have taken place in the last decade to enable analysis and deployment of alternative intersections and interchanges.

“Unfortunately, most of the analysis of alternative intersections and interchanges to this point involved the use of microscopic simulations that are expensive and time-consuming,” said Hummer. “The Highway Capacity Manual and the Highway Capacity Software — a widely used deterministic statistical equation-based analysis tool — have simpler and quicker procedures for conventional intersections and interchanges, but none for alternative designs.”

The alternatives have not been included to date due to the complex nature of traffic flow across multiple segments and junctions when compared to more conventional intersections and interchanges, according to Hummer.

In collaboration with researchers from North Carolina State University, the University of Florida and Virginia Tech, Hummer will lead the group to develop credible procedures for four designs: the double crossover diamond interchange, the displaced left turn intersection, the restricted crossing U-turn intersection and the median U-turn or Michigan left turn intersection. These procedures will be included in the next version of the Highway Capacity Manual and the Highway Capacity Software.

Once the Highway Capacity Manual is updated with the Michigan left turn, the intersection design could be Michigan’s next big export, Hummer said.

“We hope that in the future when people think of products from Michigan, they think of autos, cherries — and Michigan left turns,” he said.

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