Weight Regulations

The Federal Bridge Gross Weight Formula (also known as Bridge Formula B and the Federal Bridge Formula) is a mathematical formula in use in the United States by truck drivers and Department of Transportation (DOT) officials to determine the appropriate maximum gross weight for a commercial motor vehicle (CMV) based on axle number and spacing. The formula is part of federal weight and size regulations regarding interstate commercial traffic (intrastate traffic is subject to state limits). The formula is necessary to prevent heavy vehicles from damaging roads and bridges. CMVs are most often tractor-trailers or buses, but the formula is of most interest to truck drivers due to the heavy loads their vehicles often carry. The national Vehicle Size and Weight Team of the United States Department of Transportation Federal Highway Administration is responsible for setting up the weight regulations of commercial vehicles on the Eisenhower Interstate Highway System as well as other specifically named roads throughout the United States and Puerto Rico. If you drive a vehicle that crosses state lines and weighs over 10,001 lbs., you are subject to commercial motor vehicle regulations and DOT truck weight restrictions.

Weight per Axle

Truck weight restrictions use the number of axles on a vehicle as a basic guideline. The axle can help distribute the gross weight of the vehicle. A vehicle with a single rear axle may only haul 20,000 lbs. according to DOT weight regulations. A tandem axle vehicle may haul 34,000 lbs. The maximum gross vehicle weight for any commercial vehicle is 80,000 lbs.
The Department of Transportation also establishes truck weight restrictions for bridges. In order to minimize damages to bridges, DOT weight regulations may call for restricted weight limits on specific bridges. Commercial vehicles with longer wheelbases or multiple axles may still be able to cross these bridges with the additional weight while vehicles with single axles or shorter wheelbases may have to detour around weight-restricted bridges because of their inability to spread the weight over a larger area.


Not only do commercial vehicles need to meet standards, the Department of Transportation also requires that commercial vehicles meet size standards as well to be compliant with DOT weight regulations. While DOT doesn’t impose length restrictions on commercial vehicles other than those hauling automobiles or boats, states can and do set limits. These restrictions vary according to the individual state. The limit for car haulers on federal level is 65 feet. It may extend to 75 feet depending on the tractor-trailer setup. You should be familiar with size limitations in any state you transport materials. Vehicle width is set at 102 inches. This does not take into account any mirrors or handholds necessary for the safe operation of the vehicle. There are no federal height limitations. The states may post limits as low as 13.6 feet if necessary.


If commercial vehicle operators choose to ignore DOT regulations, they must pay a fine if caught. Since heavy vehicles are subject to weight inspection, they should have the appropriate  loads in order to facilitate the delivery of their product.
States are also subject to obeying federal truck regulations on roads within the state designated as part of the Dwight D. Eisenhower System of Interstate and Defense Highways or one of the other roads designated as part of the National Network System. If a state fails to comply with any portion of the federal DOT regulations for these highways, they stand to lose their entire allotment of federal transportation funding. Certain exceptions do apply.