Trucking Regulations in Montana
Complete guide to weight limits, speed limits, permits, chain laws, and special rules for commercial truck drivers operating in Montana.
Max Gross Weight
80,000 lbs (131,060 lbs on state routes with permit)
Truck Speed Limit
70 mph on interstates day, 65 mph night
Diesel Tax
$0.2975 per gallon diesel + federal
Weight & Size Limits in Montana
| Measurement | Limit |
|---|---|
| Max Gross Vehicle Weight | 80,000 lbs (131,060 lbs on state routes with permit) |
| Max Axle Weight | 20,000 lbs single axle, 34,000 lbs tandem |
| Max Trailer Length | 93 ft for doubles/triples on designated routes |
| Max Width | 102 inches |
| Max Height | 14 ft |
Speed Limits for Trucks in Montana
Rural Interstate
80 mph (cars), 70 mph trucks
Urban Interstate
65 mph
Truck-Specific
70 mph on interstates day, 65 mph night
Fuel Tax & Tolls in Montana
Diesel Fuel Tax
$0.2975 per gallon diesel + federal
Toll Roads & Bridges
No toll roads in the state.
Chain Laws & Weather Requirements
Chains required on certain mountain passes during winter. Montana DOT chain-up areas on I-90 and US-93.
Oversize & Overweight Permits
Montana DOT Motor Carrier Services. Permits for heavy loads up to 131,060 lbs on state routes. Montana is oversize-friendly.
Port of Entry & Weigh Stations
Ports of entry on I-15, I-90, I-94, and US-93. All commercial vehicles must stop. Montana allows triple trailers with permit on designated routes.
Special Rules for Montana
Hazmat Route Restrictions
Hazmat restricted through Glacier National Park approaches. Designated hazmat routes through Billings, Missoula, and Great Falls. Mining and oil field hazmat transport regulated by state.
Rest Area & Parking Rules
Rest areas allow overnight parking with no specific time limits. Spacing between rest areas can be 50+ miles. No anti-idling law.
DOT Inspection Frequency
Moderate. Montana Highway Patrol motor carrier unit conducts inspections at ports of entry and via mobile units. Focus on winter safety compliance.
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Frequently Asked Questions About Montana Trucking Regulations
What is Montana's maximum truck weight?
Montana allows up to 131,060 lbs on designated state routes with multi-axle configurations and proper permits. Interstate highways follow the federal 80,000 lb limit. Montana's generous weight laws support the mining, timber, and agricultural industries that rely on heavy haul transport.
What is the truck speed limit in Montana?
Montana has a 70 mph truck speed limit on rural interstates during the day and 65 mph at night, while passenger vehicles can travel 80 mph. This 10 mph differential is strictly enforced. Urban areas are typically 65 mph for all vehicles.
Are chains required on Montana mountain passes?
Montana requires chains on certain mountain passes during winter conditions. Chain-up areas are designated on I-90 (Lookout Pass at the Idaho border), US-93 over Evaro Hill, and other mountain routes. Montana DOT issues chain advisories when conditions warrant.
How far apart are services in rural Montana?
Rural Montana stretches on I-94, I-15, and US-2 can have 50-100+ miles between fuel stops and services. Drivers should always fill up when possible, especially in eastern Montana and along US-2 (Hi-Line). Cell phone service is limited or nonexistent in many areas.
Are triple trailers allowed in Montana?
Yes, Montana permits triple trailers on designated routes with proper permits. This is one of the few states that allows triples. The flat, wide highways of eastern Montana are well-suited for long combinations. Specific routes and conditions apply.