Michigan oversize permit requirements
The Michigan rule that reshapes schedules is seasonal rather than dimensional. From February to April the spring thaw brings weight reductions of up to thirty-five per cent, and a tandem that carries thirty-four thousand pounds the rest of the year may drop to twenty-six thousand. A move planned in January on January figures can be illegal by March without a single number on the load changing. Routine permit width narrows in the same period, from sixteen feet to fourteen.
Permits cover state trunklines only — the routes marked I, US or M — and not city streets, so an urban delivery needs local arrangements on top. The permit runs five travel days. The standard window is sunrise to sunset, with a weekend allowance for modest loads: within ten feet wide, fourteen feet high and ninety feet long, daylight travel to three in the afternoon on Saturdays and Sundays. Overweight-only loads within seventy feet overall may run continuously.
Eleven counties apply peak-hour bans to loads over twelve feet wide or ninety feet long, covering Detroit, Grand Rapids, Lansing, Flint, Kalamazoo and Saginaw between them. The Ambassador Bridge to Canada has its own narrow window — ten in the morning to four in the afternoon, weekdays only, with a fee on top. Legal length carries a kingpin condition of forty-one feet, and drops to fifty feet on non-designated highways.
Legal dimensions
At or under these figures, no oversize permit is required in Michigan.
- Width
- 8′6″
- Height
- 13′6″
- Gross weight
- 80,000 lb
- Steer axle
- 15,400 lb on 11″ tires
- Single axle
- 20,000 lb
- Tandem
- 34,000 lb
- Tridem
- 42,000 lb
Routine permit limits
Above legal dimensions and up to these figures, Michigan issues a permit as routine business. Beyond them the load becomes a superload, reviewed case by case.
- Length
- 150′
- Width
- 16′, reducing to 14′ during the spring thaw
- Height
- 15′
- All groups
- Assessed case by case rather than published as fixed figures
Escort requirements
A load reaching any of these figures needs an escort in Michigan — the figure is the first size that requires one, so a load measuring exactly this much already needs it.
- Width
- 12′1″
- Height
- 14′6″
- Length
- 100′1″
When the load may move
Permit validity. Permits are valid for five travel days.
Operating time. Sunrise to sunset. Loads within 10′ wide, 14′ high and 90′ long may also travel in daylight until 3 PM on Saturdays and Sundays. Overweight-only loads within 70′ overall may travel continuously.
Restricted travel. Loads over 12′ wide or over 90′ long may not travel 7–9 AM or 3–6 PM in Genesee, Ingham, Jackson, Kalamazoo, Kent, Muskegon, Macomb, Oakland, Saginaw, Washtenaw and Wayne counties. No travel on major holidays or holiday weekends. The Ambassador Bridge is open to oversize movement only 10 AM to 4 PM, Monday to Friday, with an additional fee.
Worth knowing
- From February to April, spring thaw restrictions cut allowable weights by up to 35 per cent — a tandem may drop from 34,000 lb to 26,000 lb.
- Permits cover state trunklines only, marked I, US or M. City streets are not included.
- Legal length is 53′ for the semitrailer with a 41′ kingpin setting, and 50′ on non-designated highways.
- Legal width drops to 8′ off the designated highways.
Michigan permits, answered
What is the Michigan spring thaw restriction?
From February to April, allowable weights drop by up to 35 per cent — a tandem rated at 34,000 lb may be held to 26,000 lb — and routine permit width narrows from 16′ to 14′. A move planned on winter figures can be illegal by March.
Does a Michigan permit cover city streets?
No. MDOT permits cover state trunklines only — the routes marked I, US or M. City streets need separate local arrangements.
When can an oversize load cross the Ambassador Bridge?
10 AM to 4 PM, Monday to Friday, with an additional fee. It is a narrow window for the busiest commercial crossing to Canada.
Can an oversize load travel at the weekend in Michigan?
Within 10′ wide, 14′ high and 90′ long, yes — in daylight until 3 PM on Saturdays and Sundays.
How long is a Michigan oversize permit valid?
Five travel days.
Crossing more than Michigan?
A permit is per state. If the route leaves Michigan, these are the states it most likely enters.
Get a permit quote for Michigan
Enter the load once and the estimator prices every state on the route, flags where an escort is required, and turns the quote into an order.
Price a permit for Michigan →Compiled from published state DOT sources. Regulations change — confirm the current rules before dispatch. Last reviewed 2026-07-30.