According to the Michigan Department of Transportation (MDOT), M-185 is "the only state highway in the nation where motor vehicles are banned". Traffic on it is by foot, on horse, by horse-drawn vehicle, or by bicycle. Restrictions on automobiles date back to the 1890s, and since the ban, only a few vehicles have been permitted on the island other than the city's emergency vehicles. The highway was built during the first decade of the 20th century by the state and designated as a state highway in 1933. The highway was paved in the 1950s, and portions were rebuilt to deal with shoreline erosion in the 1980s. Until an accident in 2005, it was the only state highway without any automobile accidents.