Montana Oversize & Overweight Permits
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.
A detail here is flagged medium confidence — confirm with the state permit office before you rely on it.
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: Non-Interstate: 1 front pilot car over 12'6" wide, a front and rear over 16'6", two front and one rear over 18', two front and two rear over 24'; 1 rear pilot over 150' long and a front and rear over 200'. Interstate: 1 rear pilot over 16'6" wide and two rear side by side over 18', with no length trigger. Over 17' high takes a front pilot with a height pole on any road, plus a rear pilot over 24' (MDT restrictions 36a-36d, 37a-37f; ARM 18.8.511A).
- Superload: Superload over 18' wide, 17' high, or 150' long, or any load the MDT Bridge Bureau must approve on weight, truck configuration, or route (ARM 18.8.509(11)). Class 1 runs to 34' wide, 24' high, 200' long and MDT must decide within two working days of a complete application; Class 2 is anything past that, five working days. Class 3 is a bridge-weight approval inside the ordinary dimensions, good for a year.
- Travel curfew: On the Interstate you run 24 hours a day, 7 days a week up to 18' wide, holidays and holiday weekends included; over 18' wide you park. Off the Interstate you run 24/7 up to 10' wide, 150' long, 15'6" high, and past any one of those it is daylight only. Non-Interstate loads over 18' wide, 150' long, or 17' high get no weekend travel. On a holiday or holiday weekend off the Interstate, 10' to 12'6" wide is daylight only, and over 12'6" wide, 150' long, or 15'6" high cannot move at all (MDT eTRIPs permit restrictions 1a-1e).
- 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.
Montana Oversize Permit FAQ
When do I need an oversize permit in Montana?
Does Montana require a pilot car or escort?
Can I move an oversize load at night or on weekends in Montana?
What does an oversize permit cost in Montana?
Reference information for planning, not legal advice. Traffic laws change and this can be out of date, so always confirm the current statute and obey posted signs before you rely on it. Last reviewed July 2026. Source: https://www.mdt.mt.gov/business/mcs/permits.aspx. See our Terms & Disclaimer.
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