Michigan OS/OD Overview
Permit Required
Yes – all oversize or overweight loads require a permit from the Michigan Department of Transportation (MDOT).
Legal Limits (Without Permit)
- Width: 8'6"
- Height: 13'6"
- Length: 75' (combo); 53' trailer allowed
- Weight: 80,000 lbs GVW (on federal highways; Michigan allows more on state roads with proper configuration)
Permitted Load Maximums (Typical Upper Limits)
- Width: Up to 16' with escorts
- Height: Over 14'6" requires route survey and utility notification
- Length: Over 150' requires special review and escort
- Weight: Over 250,000 lbs with engineering review, axle spacing, and bridge analysis
Michigan has unique weight laws allowing higher legal axle weights on some state routes. Superloads require careful coordination.
Travel Hours
- Standard: Sunrise to Sunset only
- Weekend: No travel after 12:00 PM Saturday or any time Sunday for most OS/OW loads
- Holidays: Travel prohibited on major holidays and holiday weekends
- Night travel: May be allowed for loads under 10' wide with lights and special permission
Escort Requirements (General Guidelines)
| Dimension | Escort Requirement |
|---|---|
| Width > 12' | 1 Escort (rear or front depending on route) |
| Width > 14' | 2 Escorts (front and rear) |
| Height > 14' | High pole escort + route clearance |
| Length > 150' | 2 Escorts minimum, possibly more depending on configuration |
Additional Notes
- “Oversize Load” signs, flags, and amber lights are required per permit
- Many local roads and townships require separate permits in Michigan
- Permits are issued through the Michigan Automated Permitting System (MAPS)
- Frost laws (seasonal load restrictions) affect movement during spring months
Detailed Information
PERMITS: Permits valid for five travel days. Must have permit prior to entering the state.
OPERATING TIME: Sunrise to sunset. Weekend travel is now being permitted on loads not exceeding 10' wide, 14' in height, and 90' in length. Saturday and Sunday daylight to 3:00 PM. If overweight only with all dimensions legal and not exceeding 70' overall length can have continuous travel.
RESTRICTED TRAVEL: Loads over 12' wide or 90' long are not to move from 7:00 a.m. – 9:00 a.m. and from 3:00 p.m. – 6:00 p.m. in the following counties: Genesee, Ingham, Jackson, Kalamazoo, Kent, Muskegon, Macomb, Oakland, Saginaw, Westenau, Wayne. No travel on major holidays and holiday weekends. Note on Bridge Crossings: Contact Mackinaw Bridge Authority (phone 906-643-7600) 24 hours prior to planned bridge
arrival/crossing. Escort will be provided (no charge) for loads exceeding legal weight or 10' wide. Crossing is not allowed when winds exceed 25 miles per hour. Ambassador Bridge (between Detroit and Windsor, Ontario) is now charging $50.00 or more for O/D shipments and may require a one-day notice. They have restricted crossing hours from 10:00 AM to 4:00 PM, Monday through Friday. Ambassador Bridge phone is 313-496-1111.
LEGAL DIMENSIONS:
Width: 8'6" designated highways, 8'0" all other roads Height: 13'6" Length: 53' semi-trailer on Interstate and designated highways, 50' maximum on non-designated highways. 53’ trailer must have kingpin setting of 41’ Weight: 80,000 Gross Steer Axle – 700 pounds per inch of tire width (15,400 pounds with 11" tires) Tandem – 34,000 (32,000 on non-designated roads, and 26,000 on second tandem) Tridem – 42,000 (39,000 on non-designated) Single – 20,000 designated highways (18,000 other roads)
ROUTINE PERMIT LIMITS: Width: 16' (or 14' during spring thaw restrictions) Height: 15' Shipper/driver are responsible for finding safe routes when the height exceeds 13'6" Length: 150' Weight: "Handled on a case-by case basis." Air or lift axles should be on the ground. You must be registered for at least the amount of weight you are permitting for Michigan. Loads exceeding these dimensions must be applied for as superloads, and may take up to ten days to issue once shipper letter, route surveys, etc. are received. Michigan is very slow on processing super load permits.
ESCORTS: Width: Height: Over 12' – 1 escort; over 14' – 2 escorts Over 14'6" – 1 escort with high pole; over 15' – 2 escorts and a route survey must be submitted and approved. Length: Over 90' – 1 escort; over 100' – 2 escorts. Overhang: Over 15' – 1 escort. LIFT AXLES: According to Michigan provision sheet, "Vehicles must have air or lift axles on ground." According to the permit office, when under a load, all axles including flip axles must be on the ground if you are overweight.
SEASONAL LOAD RESTRICTIONS: Usually February to April, maximum weights per axle and specific routing may vary. No overweight permits will be issued during the spring weight restriction period. Maximum axle weights may be reduced up to 35%. A tandem group may be allowed only 26,000 pounds (13,000 pounds per axle), or with two tandem groups they may allow 26,000 pounds for one group and 32,000 for the other tandem group. Frost Phone: 800-787-8960
SIGNS, FLAGS & LIGHTS: "Oversize Load" signs required on front of vehicle and on rear of load for any overdimensional load. An overwidth or overlength vehicle/load requires flags at each corner of the load, with an additional flag at the widest point on each side of the load if it extends beyond the corner flags. When rear overhang is 4' or more, the extreme rear of the load must have a flag for daytime running, and a red light or lantern at night.