M-85, also known as Fort Street or Fort Road for its entire length, is a state trunkline highway in the U.S. state of Michigan. The highway serves several Downriver suburbs of Detroit, as well as neighborhoods in the city itself. From its southern terminus at exit 28 on Interstate 75 (I-75) to its second interchange with exit 43 on I-75 in southwest Detroit, M-85 is part of the Lake Erie Circle Tour. In between, it serves mostly residential areas running parallel to a pair of rail lines; the highway carries between 5,000 and 43,000 vehicles per day on average. Once in the city of Detroit, Fort Street runs parallel to I-75 for several miles before they separate near the Ambassador Bridge. The northern end of M-85 is at the intersection with Griswold Street in downtown Detroit, one block away from Campus Martius Park. Two previous unrelated highways bore the M-85 designation. The first was in Montcalm County and the second near Caro. These uses were retired in the 1930s and the 1940s, respectively. The current M-85 was created in 1956 after the construction of the Detroit-Toledo Freeway; the original northern end was at an intersection with US Highway 25 (US 25) in downtown. The northern end was truncated in the late 1960s to the northern junction with I-75. The highway was then extended back into downtown Detroit in the first year of the 21st century. Route description M-85 starts a directional interchange with I-75 in near Rockwood; traffic to or from southbound I-75 must use Gibraltar Road instead. M-85 runs north from this interchange to Gibraltar Road as a full freeway; north of that intersection the highway becomes a boulevard. There are many businesses directly adjacent to Fort Street in the Downriver area with residential subdivisions on either side of them. The trunkline parallels a pair of rail lines. In this area, M-85 also runs parallel to, but inland from, the southern part of the Detroit River. The highway runs northeasterly through Gibraltar to Trenton, where it turns due north. Fort Street forms the boundary between Riverview and Trenton in the area near the Riverview Landing Shopping Center between King and Sibley Roads; north of here, Riverview extends along both sides of the road. At Pennsylvania Road, Fort Street crosses into the city of Southgate and curves to the northeast near the Southgate Tower office building. The highway returns to