Several special routes of U.S. Route 31 exist. In order from south to north they are as follows.
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Tennessee
U.S. Route 31A exists between Nashville and Pulaski, Tennessee. From Nashville, the road begins at Union St. in downtown Nashville and runs as 4th & 2nd Avenue South and South Nashville as Nolensville Pike. After passing through Davidson County, it goes through Williamson County as Nolensville Road. It then goes to a small town named Nolensville. It goes through Murfreesboro Road, and goes through as Horton Highway. it then goes as N Horton Pkwy. It heads into Marshall County and reaches the Fayetteville Hwy. before turning southwest to continue to Pulaski.
Franklin business loop
Business U.S. 31 exists between the city of Franklin and Franklin. The road starts at SR 397 (Mack Hatcher Memorial Parkway) and goes through downtown Franklin, as Columbia Pike. U.S. 31 Business then has an interchange with US 431 Business. U.S. 31 Business then goes over the Harpeth River on the Warrant Officer Judson E. Mount Memorial Bridge. U.S. 31 Business then travel through some countryside before meeting mainline U.S. 31.
Note: U.S. 31 Business is not very well signed throughout Franklin.
US 31A
Former US 31A began at an interchange with US 31 where it traveled on Indianapolis Road and 11th Street. It followed State Road 46 on Brown Street (northbound) and Lindsay Street (southbound). South of Columbus, US 31A went through Jonesville, then passed through an interchange with Interstate 65, and terminated at US 50 in Seymour, Indiana. US 31A was deleted in Indiana around 1981, and State Road 11 was extended northward.
Miami County Business Route
Business US 31 in Miami County began at US 31 south of Peru. When it reached downtown Peru, it turned right onto Bus. US 24 (Main St.), then it turned left onto Broadway. It becomes Mexico Road after an intersection with U.S. 24. Going through Mexico, the route ends at US 31 just north of Mexico.
Plymouth Alternate Route
Alternate US 31 in Plymouth traveled along the Michigan Road. It began at US 31 north of Plymouth, and terminated at US 31 south of Plymouth.
South Bend Business Route
Business US 31 in South Bend follows the former US 31 north from the US 20/US 31/St. Joseph Valley Parkway interchange on the south side of the city, joining SR 933 south of downtown, then turns west along Cleveland Road just north of the Indiana Toll Road (Interstate 80/90) to return to US 31. It is unsigned for its entire length.
Michigan
There are five current, and two former, business routes for US 31 in Michigan. In addition, there was an alternate route in the state.