Montana Oversize & Overweight Permits

When Montana needs a permit

Montana's legal envelope is 8'6" wide, 14' high, 80,000 lb; over that you permit through MDT (MCA 61-10-124). On two-lane roads a front pilot starts at 12'6" wide, a rear pilot is added at 16'6", and a high-pole car at 17' high. You get continuous travel up to about 10' wide, then it drops to daylight only. Superload-size loads pull in MDT engineering and a structural review, so plan the lead time.

Thresholds, escorts, and curfews

• Legal max before a permit: Permit needed over 8'6" wide, 14' high, 80,000 lb, or past legal length (53' trailer, up to 75' combination). Stay under all four and no permit.
• Escort / pilot car: Two-lane: one front pilot car over 12'6" wide, a front and rear pilot over 16'6", two front and one rear over 18', and a high-pole car over 17' high. Interstate: one escort over 16'6" wide or over 120' long. The widest superloads (24'+) need multiple front and rear pilots. Confirm on the permit.
• Superload: Montana has no single crisp superload number in statute. Past the routine permit band (about 18' wide, 17'-18' high, 150' long) or on a very heavy non-divisible load, MDT's Engineering and Permitting offices run a structural and route review before they issue. Build in the lead time.
• Travel curfew: Continuous travel is allowed up to about 10' wide, 15'6" high, 110' long. Bigger than that runs daylight only, up to the 18' wide / 18' high / 120' band. Movement is held on major holidays. Read the eTRIPS permit restrictions for the exact windows on your route.
• Permit fee: Single-trip oversize permits start low, roughly $10 to $40. Overweight adds a per-axle, per-mile charge that climbs fast, so a heavy overweight special can run into the thousands. Annual and blanket permits are available for repeat runs.

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