Research has shown that eliminating left turns improves safety and traffic flow. Installing a Michigan left at an intersection is one way to limit left-turn movements, reduce the number and severity crashes and fatalities (30 to 60 percent reduction), and relieve congestion (providing 20 to 50 percent more capacity than direct left turns).

Michigan lefts not only improve safety for motorists, but pedestrians, bicyclists, and truck drivers as well.

The one downside to restricting left turns is that vehicles may be required to travel a little bit further before turning. However, smoother traffic flow and safety offset the impact of the relatively small inconvenience of driving further.

Intersections can be challenging and a major factor for stress for many drivers. This is because intersections are where vehicles, often moving very fast and in different directions, meet or cross. These potential conflict points make an intersection much more complicated and increase the chance of a serious crash or fatality, especially during left-turn movements. In fact, approximately 30 percent of all crashes in Michigan occur at intersections and nearly 58 percent of those are head-on left-turn and angle crashes. In addition, roughly 30 percent of all Michigan fatal crashes occur at intersections.

Single-lane Michigan lefts are designed for one vehicle to turn at a time. While some crossovers may appear to be wide enough to fit multiple passenger vehicles side-by-side, that extra room is actually there to accommodate larger vehicles, like tractor trailers and recreational vehicles, that need a wider turning radius. Regardless of the physical width, an unmarked median crossover should always be treated as a single-lane crossover.

Multi-lane Michigan lefts are designed for two vehicles to turn at a time. Pavement markings, such as arrows, ONLY lettering, and white solid lines, indicate that both lanes may be used to turn.

Not every intersection is created equal, and installing a Michigan left depends on a few factors, including crash history, type of road, and traffic volumes.

Before a Michigan left is installed, MDOT will study the crash history and traffic volumes at major intersections along the road to determine appropriate placement. Michigan lefts are most often used in urban situations where congestion and crashes are more common. Indirect left turns can be built on divided roads with any number of lanes (i.e., four, six or eight lanes), but they are not used on freeways or limited-access roads.

Ideal spacing for Michigan lefts is between a quarter and three quarters of a mile, but the actual distance is determined by the locations of major crossroads and driveways. Intersections with traffic signals need to be far enough apart that vehicles lined up to turn will not cause significant congestion.

Additionally, there are no absolute maximum/minimum traffic volume requirements for a Michigan left to be installed. Michigan lefts increase capacity and safety and have been used on state routes with average traffic volumes between 10,000 and 100,000 vehicles per day.

Michigan lefts also increase bicyclist safety. Bicyclists can use a Michigan left as a pedestrian, dismounting the bicycle and crossing in the pedestrian area, or as a bicyclist, riding through the Michigan left and using the designated median crossover to navigate a U-turn.

Michigan lefts are built to accommodate larger vehicles, which means safer turning for commercial vehicles. MDOT designs crossovers and medians with the local traffic in mind. In major commercial or industrial areas, crossovers need to accommodate large trucks approximately 74-feet-long with a 45-foot turning radius. This is accomplished by building a wider median or by providing paved areas on the outside edge of the roadway across from the crossovers. In residential or light commercial areas, typical crossovers are designed for vehicles 55-feet-long with a 45-foot turning radius.