Michigan Left-Turn
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The Michigan Left was developed to avoid the interlocking left-turn movements along divided highways. In this way, the only turning movements allowed at such an intersection are right-hand turns. Traffic lights can be placed at busier Michigan Left intersections if warranted. For the most heavily-used "crossovers," specialized traffic signals may be placed to ensure traffic does not back up on the highway waiting to turn left.  Research and experience have shown that the Michigan Left relieves congestion; it increases safety by reducing the number and severity of crashes. Whenever MDOT plans work on a boulevard (divided roadway), engineers will consider incorporating Michigan Lefts.
 
References
Michigan DOT
Where a Michigan Left is in place, left turns at the intersection are not allowed. To turn left, you must drive straight then turn left or turn right and make a U-turn at a median crossover.
Michigan DOT

Michigan Highways
Often maligned, often misunderstood, the Michigan Left Turn is an operation which causes much consternation among out-of-state drivers and nary a second thought from locals. Developed in Michigan in 1960, these turning set-ups exist across the entire state, from Niles to Escanaba and from Detroit to Marquette.
Michigan Highways

Median U-Turn Tech Brief
In the United States, congestion at intersections throughout urban and suburban areas continues to worsen. Crashes reported at intersections have continued to increase. One potential treatment to combat congestion and safety problems at intersections is the Median U-Turn Intersection Treatment (MUTIT), which has been used extensively in Michigan for many years and has been implemented successfully in Florida, Maryland, New Jersey, and Louisiana.
Michigan U-Turn Tech Brief.pdfMichigan U-Turn Tech Brief.pdf