Idaho 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. Idaho imposes spring weight restrictions on secondary roads typically February through April during spring thaw. Posted routes have reduced weight limits to protect pavement from frost damage. Check ITD for current restricted routes and load limits before routing on state highways and county roads during this period. Oversize and overweight permits are available from ID DOT for loads exceeding standard limits. Verify current road-specific postings with the Idaho DOT before routing heavy loads.
Idaho imposes spring weight restrictions on secondary roads typically February through April during spring thaw. Posted routes have reduced weight limits to protect pavement from frost damage. Check ITD for current restricted routes and load limits before routing on state highways and county roads during this period.
Check current restrictions at ID 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 Idaho on all routes where federal standards apply.
W = maximum weight in lbs · L = axle spacing in feet · N = number of axles
Idaho Transportation Department (ITD) issues oversize/overweight permits through its Transportation Bureau. Apply at itd.idaho.gov. Single-trip permits for one-time movements. Annual permits for qualifying repetitive operations — commonly used by agricultural and timber operators. Superload permits for extreme weights require engineering review and pre-approved routing. Idaho's mountain roads require careful routing review for any oversized load — many secondary routes have low bridge clearances and narrow road widths.
Apply for Idaho OS/OW Permit →On Idaho's designated routes, the maximum gross vehicle weight is 105,500 lbs — well above the federal 80,000 lb Interstate limit. This higher limit accommodates Idaho's heavy agricultural and timber freight needs. On standard routes (non-designated), the 80,000 lb federal standard applies. Contact ITD for the current list of designated higher-weight routes.
Yes. Idaho imposes spring weight restrictions on secondary roads typically from February through April during spring thaw. These restrictions protect road surfaces from frost-heave damage. Interstate highways and designated primary routes are generally not subject to spring restrictions. Check ITD's website for current restricted routes before routing heavy loads on state routes and county roads during this period.
Idaho allows 48,000 lbs on tridem axle groups on designated routes — higher than the 42,000 lbs allowed in most states. This generous tridem limit supports Idaho's agricultural and timber industries that use multi-axle configurations to maximize payload within the 105,500 lb gross limit on designated routes.
ITD issues oversize/overweight permits through its Transportation Bureau at itd.idaho.gov. Single-trip permits for one-time movements are available online. Annual permits are widely used by Idaho agricultural operators for seasonal grain and potato hauling. Superload permits for extreme weights require engineering review. Mountain route loads require routing review for bridge and grade constraints.
Idaho provides agricultural weight exemptions for certain farm commodity vehicles on intrastate routes, which may include potato haulers moving crops from field to storage or processing. The specific vehicle configurations, axle limits, and route restrictions that qualify for agricultural exemptions are defined in Idaho statute. Contact ITD or review current Idaho agricultural vehicle statutes for precise exemption details applicable to your operation.
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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: Idaho ID Department of TransportationLast reviewed: 2026-04