Montana

Montana interstate GVW limit: 80,000 lbs. State highways allow up to 131,060 lbs with proper axle configuration. Per-axle limits: Single axle 20,000 lbs, Tandem axle 34,000 lbs, Tridem axle 42,000 lbs. Federal bridge formula on interstates; Montana allows higher weights with additional axles on state routes; LCV operations permitted. Enforcement tolerance: No general tolerance during spring restrictions.

Height: 14 ft. Width: 8 ft 6 in. Trailer length: 53 ft (semitrailer). Overall combination length: 100 ft combination (on designated routes).

Oversize/overweight permits through MDT online system Fees: Single-trip: $25; Annual: $125. Idaho oversize/overweight permits are honored under reciprocal agreements. Verify specific terms before travel. Apply online: https://www.mdt.mt.gov/business/contracting/oversize.aspx Enforcement: MHP and MDT enforcement; weigh stations on major corridors.

Agricultural: Agricultural vehicles exempt on state highways; harvest season allows extended hours and higher weights. Timber/Forestry: Timber trucks allowed up to 131,060 lbs with proper axle configuration on state routes.

Spring thaw restrictions on posted roads from March through May; reduced weights during breakup season. Check with the state DOT for current postings and dates before planning your route.

For the most current weight and size regulations, permit applications, and seasonal restriction updates, visit the official Montana DOT page at https://www.mdt.mt.gov/business/contracting/oversize.aspx. Contact the Montana Department of Transportation for specific routing questions.