Michigan Oversize & Overweight Permits

When Michigan needs a permit

Michigan is the weight outlier: its axle-spacing law legally allows up to about 164,000 lb gross on enough axles, so heavy loads can run permit-free off the Interstate while the Interstate still caps at 80,000 lb (Mich. Comp. Laws 257.719, 257.725). Oversize permits are flat and cheap: $50 single-trip, $100 annual. Rear escort over 12' wide, two over 14'. Daylight only, weekdays, and no moves on the six big holidays.

Thresholds, escorts, and curfews

• Legal max before a permit: Permit needed over 8'6" wide, 13'6" high, or the legal length. Weight is the twist: Michigan's axle-spacing law legally allows up to about 164,000 lb gross with enough axles on state and local roads, while the Interstate holds the federal 80,000 lb. Over the limit that applies to your route, permit up.
• Escort / pilot car: Rear escort over 12' wide; front and rear escorts over 14' wide. Overlength: one escort 90'-100', two escorts over 100'. Escort must be a car or pickup with an amber flashing/rotating light on the cab. Height clearances handled route-by-route on the permit.
• Superload: Superload once you top MDOT's routine permit limits: over 16' wide, 15' high, or 150' long (16' drops to 14' wide during spring thaw restrictions). Superloads need engineering review and route surveys and can take up to about 10 business days to issue once shipper docs are in.
• Travel curfew: Permits are daylight only and generally Monday through Friday (a half hour before sunrise to a half hour after sunset). No oversize movement on New Year's, Memorial Day, July 4th, Labor Day, Thanksgiving and Christmas, from noon the day before to dawn the day after. Detroit metro adds peak-hour limits.
• Permit fee: Cheap and flat: single-trip is $15 oversize-only or $50 if it's also overweight; a multi-trip or annual permit is $100 from MDOT (Mich. Comp. Laws 257.725). Local road authorities may charge their own, capped at the same figures.

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