Illinois 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. Illinois imposes spring weight restrictions on certain secondary roads typically from early March through late April. Reduced axle weight limits (often 73,280 lbs gross) apply on posted roads during spring thaw. Check IDOT for current restricted routes. Oversize and overweight permits are available from IL DOT for loads exceeding standard limits. Verify current road-specific postings with the Illinois DOT before routing heavy loads.
Illinois imposes spring weight restrictions on certain secondary roads typically from early March through late April. Reduced axle weight limits (often 73,280 lbs gross) apply on posted roads during spring thaw. Check IDOT for current restricted routes.
Check current restrictions at IL 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 Illinois on all routes where federal standards apply.
W = maximum weight in lbs · L = axle spacing in feet · N = number of axles
IDOT issues oversize/overweight permits. Chicago city permits required separately for loads on city streets. Annual permits available for routine operations. Superloads require engineering review and route approval.
Apply for Illinois OS/OW Permit →On Illinois Interstate highways, the maximum gross vehicle weight is 80,000 lbs matching the federal standard. However, many Illinois state routes limit gross weight to 73,280 lbs without an overweight permit. Plan routes carefully to avoid state routes with lower limits.
Yes. Illinois typically imposes spring weight restrictions from early March through late April on secondary state roads and certain routes. Reduced limits (often to 73,280 lbs gross) apply during spring thaw. Check IDOT's website for current restricted routes before routing heavy loads in spring.
No. Triple trailers are prohibited in Illinois. Double trailers are allowed with a Class A CDL and T endorsement, but triples cannot operate on Illinois roads.
Yes. Chicago city streets require a Chicago city permit in addition to an Illinois IDOT oversize/overweight permit. Contact the Chicago Department of Transportation for city permit requirements. Routes through Chicago must be pre-approved.
Illinois allows 34,000 lbs on tandem axles on Interstate highways, matching the federal standard. On certain state routes with the 73,280 lb gross limit, tandem axle limits may be proportionally lower. Always verify road-specific limits with IDOT before routing.
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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: Illinois IL Department of TransportationLast reviewed: 2026-04