M-37 is a north–south state trunkline highway in the US state of Michigan. The southern terminus is near the border between Kalamazoo and Calhoun counties at exit 92 of Interstate 94 (I-94) southwest of Battle Creek. The northern terminus is at the Mission Point Light on Old Mission Point in Grand Traverse County. In between, the highway connects Battle Creek, Grand Rapids and Traverse City. Motorists will travel through agricultural land, forests, suburbs and large cities along the way. The section of M-37 on the Old Mission Peninsula was designated what is now a Pure Michigan Scenic Byway in 2008.
M-78 is a state trunkline highway in the US state of Michigan. The western terminus is the intersection with M-66 north of Battle Creek in Pennfield Township. The roadway runs 10.744 miles (17.291 km) through rural farmland and the community of Bellevue as it approaches its eastern terminus at an interchange with Interstate 69 (I-69) near Olivet. The highway is used by between 3,100 and 5,300 vehicles on a daily basis.
M-21 is an east–west state trunkline highway in the US state of Michigan connecting the cities of Grand Rapids and Flint. The highway passes through rural farming country and several small towns along its course through the Lower Peninsula. Following the course of a handful of rivers, M-21 also connects some of the state's freeways like Interstate 96 (I-96), US Highway 127 (US 127) and I-75. The highway is used by between 1,700 and 36,000 vehicles daily.
Interstate 196 (I-196) is an auxiliary Interstate Highway that runs for 80.6 miles (129.7 km) in the US state of Michigan. It is a state trunkline highway that links Benton Harbor, South Haven, Holland, and Grand Rapids. In Kent, Ottawa, and Allegan counties, I-196 is known as the Gerald R. Ford Freeway, or simply the Ford Freeway, after President Gerald Ford, who was raised in Grand Rapids and served Michigan in the House of Representatives for 25 years. This name generally refers only to the section between Holland and Grand Rapids. I-196 changes direction; it is signed as a north–south highway from its southern terminus to the junction with US Highway 31 (US 31) just south of Holland, and as an east–west trunkline from this point to its eastern terminus at an interchange with I-96, its parent highway. There are three business routes related to the main freeway. There are two business loops and one business spur that serve South Haven, Holland and the Grand Rapids areas. Another business spur for Muskegon had been designated relative to the I-196 number.
M-96 is a state trunkline highway in the US state of Michigan that runs between Kalamazoo and Marshall. Its termini are both on business routes of Interstate 94 (I-94); the eastern one coincides with an intersection with I-69. Between Kalamazoo and Marshall it passes through Comstock, Galesburg, Augusta, and Battle Creek intersecting I-194/M-66 in Battle Creek and I-94 in Emmett Township.
M-43 is a state trunkline highway in the southwestern and central parts of the US state of Michigan. The highway runs from South Haven to Webberville along an indirect path through both rural areas and larger cities. The trunkline follows five overall segments: a southeasterly track from South Haven to Oshtemo Township, a northerly path to Plainwell, a southeasterly route to Richland, a northeasterly course to the Hastings area and an easterly route through the Lansing area.
US Highway 16 (US 16), also called Grand River Avenue for much of its length in the state, was one of the principal roads prior to the post-World War II construction of freeways in the state of Michigan. Before the creation of the United States Numbered Highway System in 1926, the highway had been designated as a state highway numbered M-16. The modern route of Grand River Avenue cuts across the Lower Peninsula in a northwest–southeast fashion from near Grand Rapids to Detroit. Before the late 1950s and early 1960s, US 16 followed other roads between Muskegon and Grand Rapids, and then Grand River Avenue through Lansing to Detroit. In the years immediately preceding the creation of the Interstate Highway System, US 16 was shifted from older roads to newer freeways. Later, it was co-designated as an Interstate. When the gap in the freeway was filled in around Lansing, the US 16 designation was decommissioned in the state. The freeway was solely designated Interstate 96 (I-96) east of Grand Rapids and I-196 west of that city.
M-50 is a state trunkline highway in the US state of Michigan. Although designated as an east–west highway, it is nearly a diagonal northwest–southeast route. The western terminus is at exit 52 along Interstate 96 (I-96) near Alto a few miles east of the metro Grand Rapids area, and its eastern terminus is in downtown Monroe at US Highway 24. In between the trunkline runs through seven counties of the southern part of the Lower Peninsula mostly through rural farm fields and small communities. The highway also runs through downtown Jackson to connect between two freeway sections of US 127. In the Irish Hills area of the state southeast of Jackson, M-50 runs next to Michigan International Speedway.
M-14 is an east–west state trunkline highway in the southeastern portion of the US state of Michigan. Entirely freeway, it runs for 22.250 miles (35.808 km) to connect Ann Arbor with Detroit by way of a connection with Interstate 96 (I-96). The western terminus is at a partial interchange with I-94 west of Ann Arbor. From there, the freeway curves around the north side of Ann Arbor and runs concurrently with US Highway 23 (US 23). East of that section, M-14 passes through woodlands and fields in Washtenaw County. In Wayne County, the freeway returns to a suburban area of mixed residential neighborhoods and light industrial areas. It crosses two different rivers and a pair of rail lines as it approaches Detroit's inner suburbs, where it terminates at an interchange between I-96 and I-275.
M-51 is a north–south state trunkline highway in the southwestern portion of the US state of Michigan. The southern terminus is at a connection with State Road 933 across the Michigan–Indiana state line near South Bend, Indiana. From there the trunkline runs north through an interchange with US Highway 12 (US 12) into Niles along a route that was once part of Business US 12. North of Niles, the highway runs parallel to a river and a rail line through rural areas. The northern terminus is on Interstate 94 (I-94) west of Paw Paw.
M-45 is a state trunkline highway in the US state of Michigan that is also called Lake Michigan Drive. The highway runs from Agnew near Lake Michigan to the west side of Grand Rapids in the western Lower Peninsula. Lake Michigan Drive continues in each direction from M-45's termini, extending west of US Highway 31 (US 31) and east of Interstate 196 (I-196). In between, the road runs through rural and suburban areas of Ottawa and Kent counties, including the main campus of Grand Valley State University in Allendale. Lake Michigan Drive was originally part of M-50 until the mid-1960s. Previously in the 1920s and 1930s, the M-45 number was designated along a highway in the Upper Peninsula (UP).
M-143, also known as Michigan Avenue, is a previously unsigned spur state trunkline highway in the south central region of the US state of Michigan. The M-143 portion of Michigan Avenue runs from the East Lansing city limit to a junction with M-43 at Grand River Avenue. This highway is the second time that there has been an M-143 in Michigan. The first was a connection to the original Cheboygan State Park. The current is a remnant of M-43 in the Lansing area.
M-44 is a 37.463-mile (60.291 km) state trunkline highway in the western region of the US state of Michigan. It runs northward from the intersection of M-11 and M-37 toward the Rockford area. The highway then turns eastward to Belding, and it ends six miles (10 km) north of Ionia at M-66. M-44 is known in Grand Rapids as the "East Beltline" and intersects with its related highway, Connector M-44, in Plainfield Township. This highway runs concurrently with M-37 between M-11 and Interstate 96 (I-96).
M-114 was the designation of a former state trunkline highway and planned beltline in the US state of Michigan around the city of Grand Rapids. It was designated by the end of 1929 on various streets in adjoining cities and townships. By the 1940s, sections of it on the west and south sides of Grand Rapids were given new designations and the segment along the east side of town was finished. By late 1945 the highway designation was completely decommissioned in favor of other numbers. M-114 split into two branches, one running east–west and the other running north–south. The east–west spur routing is now local streets while the rest is part of state highways.
US Highway 12 (US 12) is an east–west United States Numbered Highway that runs from Aberdeen, Washington, to Detroit, Michigan. In Michigan, it runs for 210 miles (340 km) between New Buffalo and Detroit as a state trunkline highway and Pure Michigan Byway. On its western end, the highway is mostly a two-lane road that runs through the southern tier of counties roughly parallel to the Indiana state line. It forms part of the Niles Bypass, a four-lane expressway south of Niles in the southwestern part of the state, and it runs concurrently with the Interstate 94 (I-94) freeway around the south side of Ypsilanti in southeastern Michigan. In between Coldwater and the Ann Arbor area, the highway angles northeasterly and passes Michigan International Speedway. East of Ypsilanti, US 12 follows a divided highway routing on Michigan Avenue into Detroit, where it terminates at an intersection with Cass Avenue.
There are currently eight business routes of Interstate 94 (I-94) in the US state of Michigan. These business routes connect I-94 to the downtown business districts of neighboring cities. Seven of the eight routes are business loops which bear the Business Loop I-94 designation while one is a business spur that bears the Business Spur I-94. These loops are former routings of I-94's two predecessors in Michigan: US Highway 12 (US 12) or US 25. The westernmost BL I-94 runs through the twin cities of Benton Harbor and St. Joseph along the former routing of US 12 and US 31/US 33 that now includes a section of the Lake Michigan Circle Tour in the state. The loops in Kalamazoo, Battle Creek, Marshall, Albion, and Jackson were also formerly segments of US 12 which were later designated as separate version of Business US Highway 12 through their respective cities before becoming BL I-94s in 1960. The BL I-94 in Kalamazoo was converted into BS I-94 in 2019. The route of the business loop through Ann Arbor was previously US 12 and then later M-14 before receiving its current moniker. The BL I-94 through Port Huron was previously US 25 and then Business US Highway 25.
There are six business routes of US Highway 131 in the state of Michigan, and previously there was one bypass route and an additional business route. All of the business routes are former sections of US Highway 131 (US 131). These former sections of the mainline highway, along with the necessary connecting roads, allow traffic to access the downtowns business districts of cities bypassed by sections of US 131 built since the 1950s. The extant business loops connect to Constantine, Three Rivers, Kalamazoo, Big Rapids, Cadillac, and Manton. The former bypass route in Grand Rapids allowed traffic to bypass that city's downtown at a time when US 131 still ran through the heart of the city, and the later business route connected through downtown while US 131 ran on a freeway bypassing the central business district.
There have been six business routes of Interstate 96 (I-96) in the US state of Michigan. There are two business loops designated Business Loop Interstate 96 : one through Lansing and one through Howell. Both follow the old route of US Highway 16 (US 16), with appropriate connections to I-96. There are three former business spurs that were designated Business Spur Interstate 96. One connected to the carferry docks in Muskegon, running concurrently with part of Business US 31 along former US 16, but it has been eliminated. The second spur ran into downtown Portland until it was decommissioned in 2007. Two routes in the Detroit area—a loop through Farmington and a spur into Detroit—both using Grand River Avenue, and meeting at the temporary end of I-96 near Purdue Avenue, were eliminated when I-96 was moved to the completed Jeffries Freeway in 1977. The Farmington business route is still state-maintained as an unsigned highway, while the Detroit business route remained unsigned until it was decommissioned in 2016 and replaced by an extension of M-5.
I-96 near Marne 
