Federal law places weight restrictions on trucks traveling on the Interstate Highway System, states the Federal Highway Administration. As of 2015, the total gross weight of a truck may not exceed 80,000 pounds.
The total weight allowed on a single axle is 20,000 pounds, while the weight allowed on a tandem axle is 34,000 pounds, states the Federal Highway Administration. Total gross allowable weight on bridges may be lower.
The Federal Highway Administration allows state law to determine the truck weight limit on some roads, as the California Department of Transportation demonstrates. For example, in California, trucks traveling on Route 85 or Interstate 580 may weigh up to 4.5 tons.