| Interstate Highways of the State Trunkline Highway System | |
|---|---|
Highway markers in different years for Interstate 69 (1957), Business Loop Interstate 75 (1957), Interstate 94 (1971), Business Spur Interstate 96 (1971) and the Capitol Loop (1989) | |
 Michigan's Interstates highlighted in red | |
| System information | |
| Maintained by MDOT and MBA | |
| Length | 1,238.709 mi[2] (1,993.509 km) Plus 197.816 mi [2] (318.354 km) of business routes |
| Formed | June 29, 1956[1] |
| Highway names | |
| Interstates | Interstate nn (I‑nn) |
| Business Loops: | Business Loop Interstate nn (BL I‑nn) |
| Business Spurs: | Business Spur Interstate nn (BS I‑nn) |
| System links | |
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The Interstate Highways in Michigan are the segments of the national Dwight D. Eisenhower System of Interstate and Defense Highways[3] that are owned and maintained by the U.S. state of Michigan,[4] totaling about 1,239 miles (1,994 km).[2] The longest of these, Interstate 75 (I-75), is also the longest highway of any kind in the state.[5] On a national level, the standards and numbering for the system are handled by the Federal Highway Administration (FHWA) and the American Association of State Highway and Transportation Officials (AASHTO), while the highways in Michigan are maintained by the Michigan Department of Transportation (MDOT) and the Mackinac Bridge Authority (MBA). The Interstates in Michigan have their origins in World War II-era expressways built in the Detroit area. After the system was created in 1956, the state highway department completed its first border-to-border Interstate in 1960. The last highway was completed in 1992, giving Michigan a total of 13 Interstate freeways. The original allotment of mileage to Michigan which would receive federal funding was expanded in 1968, and the United States Congress designated an additional highway in the 1990s that has not yet been built.
There are also 26 current business routes that connect cities bypassed by the Interstates; 22 are business loops that connect on both ends to their parent highway, and four are business spurs that connect on only one end. I-496 had the Capitol Loop as its connection to the Michigan State Capitol in downtown Lansing. Another six business routes have been designated but are either no longer signed or maintained as state highways.
- ^ McNichol (2006), p. 106.
- ^ a b c Cite error: The named reference
PRFAwas invoked but never defined (see the help page). - ^ Swift (2011), p. 5.
- ^ Hamilton (2007), p. 8.
- ^ Cite error: The named reference
factswas invoked but never defined (see the help page).
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