Iowa commercial vehicle weight limits follow the federal Interstate standard of 80,000 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. Iowa imposes seasonal weight restrictions on secondary roads during spring thaw, typically February through April. Frost law reduces axle weight limits on posted routes to protect pavement from freeze-thaw damage. Check Iowa DOT for current restricted routes and reduced limits before routing on state and county roads. Oversize and overweight permits are available from IA DOT for loads exceeding standard limits. Verify current road-specific postings with the Iowa DOT before routing heavy loads.
Iowa imposes seasonal weight restrictions on secondary roads during spring thaw, typically February through April. Frost law reduces axle weight limits on posted routes to protect pavement from freeze-thaw damage. Check Iowa DOT for current restricted routes and reduced limits before routing on state and county roads.
Check current restrictions at IA 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 Iowa on all routes where federal standards apply.
W = maximum weight in lbs · L = axle spacing in feet · N = number of axles
Iowa DOT issues oversize/overweight permits through the Motor Vehicle Division. Apply through the Iowa DOT permit system. Single-trip permits for one-time movements. Annual permits for qualifying routine operations — widely used by Iowa grain, pork, and agricultural supply chain operators. Superload permits for extreme weights require engineering review and pre-approved routing. Iowa's bridge formula enforcement is active — bridge formula violations are a common citation category for Iowa-based carriers.
Apply for Iowa OS/OW Permit →On Iowa Interstate highways with 8-axle configurations, the maximum gross vehicle weight is 96,000 lbs — 16,000 lbs above the standard federal 80,000 lb limit. Standard 5-axle configurations are limited to 80,000 lbs on most routes. Iowa state routes and county roads may have lower posted limits. Overweight permits from Iowa DOT are required for loads exceeding applicable legal limits.
Yes. Iowa imposes frost law weight restrictions on secondary roads typically from February through April during spring thaw. These restrictions are among the most restrictive in the country — county roads may post limits as low as 10,000–15,000 lbs per axle. Posted road signs and Iowa DOT's frost law hotline indicate currently restricted routes and their applicable limits. Plan routes to avoid secondary roads during frost law whenever possible.
Iowa allows 96,000 lbs gross vehicle weight for 8-axle vehicle combinations on Iowa Interstate highways. This allowance is designed to accommodate Iowa's heavy agricultural freight needs and allows operators to use multi-axle vehicle configurations (such as a tandem-drive tractor with a tridem-axle trailer) to maximize payload within bridge formula constraints. Vehicles operating under this allowance must comply with proper axle spacing requirements.
Iowa DOT issues oversize/overweight permits through its Motor Vehicle Division permit system at iowadot.gov. Single-trip and annual permits are available online. Annual permits are widely used by Iowa agricultural operators for grain, pork, and farm supply hauling. Superload permits for extreme weights require engineering review. During frost law periods, overweight permits on restricted secondary routes may not be available — plan accordingly.
Grain hauling in Iowa involves a complex weight limit environment. Interstate hauling uses the standard 80,000 lb (or 96,000 lb with 8 axles) limits. State highways have their own limits. County road limits are the most restrictive — especially during spring frost law. Agricultural exemptions may apply for certain moves of unprocessed grain. During fall harvest, operators typically maximize legal loads for efficiency; during spring planting supply season, careful routing around restricted county roads is essential.
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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: Iowa IA Department of TransportationLast reviewed: 2026-04