Montana commercial vehicle weight limits follow the federal Interstate standard of 105,500 lbs gross, 20,000 lbs per single axle, and 34,000 lbs per tandem axle group. The federal bridge formula (23 U.S.C. 127) applies on all routes. Montana imposes seasonal weight restrictions on secondary roads during spring breakup, typically February through May. Mountain passes may have year-round restrictions on certain grades. Check MDT's road condition system at mdt.mt.gov for current restricted routes before routing off Interstate or US highways. Oversize and overweight permits are available from MT DOT for loads exceeding standard limits. Verify current road-specific postings with the Montana DOT before routing heavy loads.
Montana imposes seasonal weight restrictions on secondary roads during spring breakup, typically February through May. Mountain passes may have year-round restrictions on certain grades. Check MDT's road condition system at mdt.mt.gov for current restricted routes before routing off Interstate or US highways.
Check current restrictions at MT DOT →The federal bridge formula limits the weight on any group of axles based on the distance between the outermost axles in the group. It applies in Montana on all routes where federal standards apply.
W = maximum weight in lbs · L = axle spacing in feet · N = number of axles
Montana oversize/overweight permits are issued by MDT at mdt.mt.gov/business/permits/. Single-trip permits available for most oversize/overweight loads. Annual permits available for certain qualifying operations. Superload permits (extremely heavy or wide loads) require engineering review and route pre-approval. Montana's remote road network means permit routing must account for bridge ratings on gravel county roads.
Apply for Montana OS/OW Permit →On Montana Interstate highways, the maximum gross vehicle weight is 80,000 lbs — the federal standard. On designated Montana state non-Interstate routes, the limit can reach 105,500 lbs. Verify which specific routes qualify for higher limits at MDT before operating above 80,000 lbs.
Yes. Montana imposes seasonal spring weight restrictions on secondary roads during spring breakup, typically February through May. Some roads close entirely to heavy vehicles during peak thaw. Check MDT's road conditions and spring restriction maps at mdt.mt.gov before routing off the Interstate and US highway system in spring.
Montana oversize/overweight permits are issued by MDT at mdt.mt.gov/business/permits/. Apply online for single-trip permits for most oversize or overweight loads. Annual permits are available for qualifying routine heavy-haul operations such as oil field service trucks. Superloads require engineering review.
The tandem axle weight limit in Montana is 34,000 lbs on Interstate highways — the federal standard. On designated Montana state routes, higher tridem axle limits of 48,000 lbs may apply. Verify route-specific limits with MDT before routing. Spring restrictions can further reduce tandem limits on secondary roads.
Montana logging trucks operating on designated forest routes may operate under specific weight agreements with MDT and the US Forest Service. Logging operations on Interstates and state primary routes must comply with posted limits. Montana's 105,500 lb GVW allowance on designated state routes is particularly valuable for loaded log hauls. Contact MDT Permit Office for current logging weight authorization details.
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Disclaimer
The information on this page is compiled from publicly available government sources and is provided for general informational purposes only. TruckRadar is an independent search engine — we are not affiliated with any government agency and this content does not constitute legal or compliance advice. Regulations change frequently; always verify current requirements directly with the official source before making compliance decisions.
Official source: Montana MT Department of TransportationLast reviewed: 2026-04