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Portal:Michigan Highways

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Michigan Highways

The State Trunkline Highway System of the US state of Michigan is a network of roads owned and maintained by the Michigan Department of Transportation (MDOT). The most prominent of these roads are part of one of three numbered highway systems in Michigan: Interstates Highways, US Highways, and the other State Trunklines. Other systems of roads are operated by the 83 counties in the state as well as each city.

Interstate Highways and US Highways are assigned at the national level. Interstate Highways are numbered in a grid—even-numbered highways are east–west highways (but the lowest numbers are along Mexico and the Gulf of Mexico), and odd-numbered highways are north–south highways (with the lowest numbers along the Pacific Ocean). US Highways are also numbered in a grid—even numbered for east–west highways (with the lowest numbers along Canada) and odd numbered for north–south highways (with the lowest numbers along the Atlantic Ocean). For this reason, mainline (two-digit) Interstate Highways in Michigan all have numbers above 69 and mainline US Highways all have numbers below 45. Three-digit Interstate and U.S. Highways, also known as "child routes," are branches off their main one- or two-digit "parents". The Interstate and US Highways are maintained by MDOT. Interstate 75 (I-75) and US Highway 23 (US 23) are the longest examples in the state.

State Trunklines are the other state highways maintained by MDOT. These highways are completely owned and maintained by the state. Michigan highways are properly referred to using the M and never as "Route 28" or "Highway 115", but as M-28 or M-115. The marker used for state trunklines is a diamond with a block-letter "M" at the top. Roads that are maintained by the state but not assigned a state trunkline designation carry an unsigned highway designation.

County-Designated Highways are assigned numbers in a zone system by MDOT, but maintained by the counties. Each zone is indicated by a letter A–H which is followed by a number based on a grid inside that zone. Each county also maintains any other roadway that is not a state trunkline or a city street. The numbering and signing practices vary from county to county, as does the size of each county's system. Numerical designations typically do not carry over from one county to the next; a CDH that crosses county lines keeps its designation in each county however. County road designations are typically abbreviated "CR" or "Co Rd" followed by the number, and CDHs are abbreviated to just their letter and number assignment.

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H-63 is a county-designated highway in the Upper Peninsula. The highway parallels the I-75 corridor between St. Ignace and Sault Ste. Marie. The road is called Mackinac Trail after the Upper Peninsula branch of an Indian trail used before European settlers reached the area. Originally, the roadway was built as a section of US 2 before being added to the CDH system in the 1970s. H-63 serves as a two-lane alternative to the I-75 freeway across the eastern end of the Upper Peninsula. Between the northern side of St. Ignace, the roadway has connections to two state highways before running concurrently with M-48 near Rudyard. H-63 ends on the south side of Sault Ste. Marie. (more...)

Recently selected: U.S. Route 223 • M-64 • M-73

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Mackinac Bridge

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U.S Route 12 business loop Ypsilanti Michigan.JPG
Bus. US 12/M-17 in downtown Ypsilanti

Recently selected: Bus. M-28 • I-75 • US 131/M-55

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State Trunkline System, overview of the system

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