Commercial Vehicle Weight Limits Explained
Federal law generally limits combination trucks to 80,000 pounds gross vehicle weight on the interstate system, with additional limits per axle group — 20,000 lbs on a single axle and 34,000 lbs on a tandem axle group. States may set different limits on non-interstate roads and issue permits for legal overweight loads.
Key Takeaways
- Federal gross weight limit: 80,000 lbs on the interstate system.
- Single axle limit: 20,000 lbs; tandem axle group limit: 34,000 lbs.
- The 'bridge formula' further restricts weight based on axle spacing.
- Weigh stations and scale records document compliance or violations.
How the federal weight formula works
The 80,000-pound gross limit is only part of the picture — the federal 'bridge formula' also restricts weight based on the distance between axles, preventing trucks from concentrating too much weight over too short a wheelbase, which would damage bridges and roads and compromise handling and braking. Single axles are capped at 20,000 lbs and tandem axle groups at 34,000 lbs.
States can authorize overweight loads through special permits for certain routes and cargo (agricultural products, indivisible loads like large equipment), but these permits come with specific route and escort requirements.
Why overweight trucks are dangerous — and how it's proven
An overloaded truck takes longer to stop, strains its brakes and tires beyond their design limits, and handles less predictably in curves and emergency maneuvers — all of which raise crash risk and severity. Weigh station records, scale tickets, bills of lading, and post-crash weighing of the vehicle establish whether a truck was over its legal limit at the time of the crash.
Overweight violations frequently implicate the shipper or loader in addition to the carrier, since federal law places responsibility for accurate weight declarations on whoever loaded and documented the cargo.
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Frequently Asked Questions
What is the maximum legal weight for a semi-truck?+
Generally 80,000 pounds gross vehicle weight on the interstate system, subject to axle weight limits and the bridge formula, unless an overweight permit applies.
How is a truck's weight verified after a crash?+
Through weigh station and scale records from the trip, bills of lading, and in some cases post-crash weighing or reconstruction analysis.
Who is liable if a truck was illegally overweight?+
The carrier and driver, and potentially the shipper or loader that certified an inaccurate weight, can all share liability.