Truck Weight

Truck weight is a carefully monitored aspect of the trucking industry. Both federal and state laws regulate truck weight for tractor trailers and other commercial motor vehicles (CMVs). All vehicles are required to meet federal truck weight limitations. After these basic requirements are met, trucks must follow the truck weight laws of each state that is traveled through. State truck weigh stations exist to regulate truck weight.

Federal Truck Weight Laws

The Federal Bridge Gross Weight Formula is a mathematical formula for determining an appropriate maximum gross weight of a truck. It is also referred to as the Federal Bridge Formula or Bridge Formula B. The formula is used in the U.S. by the Department of Transportation (DOT) and truck drivers, and is primarily intended to preserve the integrity of U.S. bridges and highways. Truck weight calculation involves the number and spacing of axles within the truck. The formula is also used for other commercial motor vehicles (CMVs) such as buses.

Federal truck weight laws for CMVs driving on the Interstate Highway System are as follows:

  • Single-axle vehicles: 20,000 pound truck weight limit
  • Tandem axle vehicles: 34,000 pound truck weight limit
  • Gross vehicle weight: 80,000 pound truck weight limit

Federal Truck Dimension Laws

Most tractor-trailers do not have a federally-mandated maximum length. However, vehicles that carry boats or automobiles are restricted to 65 or 75 feet, depending on the connection type between the trailer and tractor. Federal laws dictate that no state may limit truck length to less than 48 feet on a semi-trailer and 28 feet on a twin-trailer. No state is permitted to alter the vehicle width requirement of 102 inches. There are no federal requirements for vehicle height.

State Truck Weight Laws

State truck weight laws may vary between states. States typically calculate truck weight based on axle weight, or the amount of weight that is carried by each axle of a truck. Gross weight is also used. Gross weight is the combined weight of all of the truck’s axles. A common truck weight limit is 34,000 pounds in standard tractor trailers.

Truck Weigh Stations

Truck weigh stations are used by states to ensure that passing trucks meet state safety guidelines. Additionally, truck weigh stations are used by many states to collect taxes in accordance with the weight of the goods being transported. Each truck weight station may use differing methods to weigh the truck. Truck weight may be determined by weighing each axle at a time, the entire truck weight at once using several scales, or new technology that measures truck weight while the truck is in motion.


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