Portal:Michigan highways
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 (with the lowest numbers 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.
Recognized content - 
M-25 is a state trunkline highway in the US state of Michigan. The route follows an arc-like shape closely along the Lake Huron shore of the Thumb in the eastern Lower Peninsula between Port Huron and Bay City. It serves the lakeshore resorts along Lake Huron and Saginaw Bay and generally lies within sight of the lake and the bay. All is surface road and generally scenic, except for the freeway segment near the junction with Interstate 75 (I-75) and connection into the US Highway 10 (US 10) freeway.
Between Port Huron and Port Austin it is the north–south highway was formerly US 25 before the designation was removed. Between Port Austin and Bay City it is an east–west route that appeared on some maps as US 25 and on some maps as M-25. Since the 1970s, when all of US 25 was deleted north of Cincinnati, Ohio, it is entirely signed as M-25. (Full article...)
General images
Planning map for the Detroit area freeways from 1955
Construction along I-96 for the interchange with M-231 in July 2013 (from Michigan State Trunkline Highway System)
Grand River Avenue, once a part of M-16 and later US 16, was originally an Indian trail converted as a plank road before becoming a state highway.
M-87 on November 1, 1956
Junction between M-28 and M-178 south of Munising before 1941
Exit 254 on I-75 south of Grayling
Map of the zone system
Dead Man's Curve along the Marquette–Negaunee Road shown in 1917 with its hand-painted centerline, the first in the nation
Welcome sign along US 8
Interstate HighwaysOther freewaysMiscellaneous expressways
M-553 approaching Glass' Curve south of Marquette
H-13 during winter
A-2 in Allegan County south of Holland
Milemarker used in 1922 for M-14
Map of the pre-statehood Indian trails
M-121 in Jenison
M-39 bridge over the River Rouge in Dearborn
H-58 west of Grand Marais
Selected picture
Topics
State Trunkline System, overview of the system
- Interstates Highways in the state
- US Highways in the state
- State Trunklines
- County-Designated Highways in the state
- Pure Michigan Byways, a system of scenic, historical or recreational highways in the state
- Great Lakes Circle Tour
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