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Commercial Vehicle Size and Weight Program

Authorization of the “Dwight D. Eisenhower System of Interstate and Defense Highways” (the Interstate Highway System) in the 1950s created an interest in preserving the integrity of highways built with federal funds. Federal interest in the nation's highway system also extends to ensuring the safety, productivity, and mobility of freight commerce.

The national Vehicle Size and Weight Team, a part of the Federal Highway Administration's (FHWA's) Office of Freight Management and Operations, oversees state enforcement of heavy truck and bus size and weight standards in the United States. The Vehicle Size and Weight Team is assisted by FHWA's policy and legal staff. Additionally, staff in each of FHWA's 52 Division Offices provide one-on-one support to individual states, the District of Columbia, and Puerto Rico. Washington Headquarters and Division Office staff also assist with policy questions, clarifications, reporting requirements, training, and other related program and administrative issues.

Trucks entering weigh station for weight compliance check
View of weigh station
Trucks entering weigh station for weight compliance check.

Federal standards center on a commercial vehicle's weight, length, and width. Specific details of the standards follow.

Commercial Vehicle Weight Standards

National weight standards apply to commercial vehicle operations on the Interstate Highway System, an approximately 40,000-mile system of limited access, divided highways that spans the nation. Off the Interstate Highway System, states may set their own commercial vehicle weight standards.

Federal commercial vehicle maximum standards on the Interstate Highway System are:

Single Axle: 20,000 pounds
Tandem Axle: 34,000 pounds
Gross Vehicle Weight: 80,000 pounds

Bridge Formula Weights
The bridge formula was introduced in 1975 to reduce the risk of damage to highway bridges by requiring more axles, or a longer wheelbase, to compensate for increased vehicle weight. The formula may require a lower gross vehicle weight, depending on the number and spacing of the axles in the combination vehicle.1

Commercial Vehicle Size (Length and Width) Standards2

National vehicle size standards apply on what is known as the National Network of highways. The National Network includes: (1) the Interstate Highway System and (2) highways, formerly classified as Primary System routes, capable of safely handling larger commercial motor vehicles, as certified by states to FHWA. The total National Network system is about 200,000 miles. (See table for specific limits.)

Federal Commercial Vehicle Size Limits on the National Network

Overall vehicle length

No federal length limit is imposed on most truck tractor-semitrailers operation on the National Network.

Exception: On the National Network, combination vehicles (truck tractor plus semitrailer or trailer) designed and used specifically to carry automobiles or boats in specially designed racks may not exceed a maximum overall vehicle length of 65 feet, or 75 feet, depending on the type of connection between the tractor and trailer.

Trailer length

Federal law provides that no state may impose a length limitation of less than 48 feet (or longer if provided for by grandfather rights) on a semitrailer operating in any truck tractor-semitrailer combination on the National Network. (Note: A state may permit longer trailers to operate on its National Network highways.)

Similarly, federal law provides that no state may impose a length limitation of less than 28 feet on a semitrailer or trailer operating in a truck tractor-semitrailer-trailer (twin-trailer) combination on the National Network.

Vehicle width

On the National Network, no state may impose a width limitation of more or less than 102 inches. Safety devices (e.g., mirrors, handholds) necessary for the safe and efficient operation of motor vehicles may not be included in the calculation of width.

Vehicle height

No federal vehicle height limit is imposed. State standards range from 13.6 feet to 14.6 feet.

Penalties for Non-Compliance with Federal Standards

Weight Standards: A state is subject to loss of its entire National Highway System apportionment if its laws or regulations establish weight limits for commercial motor vehicles operating on the Interstate Highway System that are either higher or lower than the four federal weight standards mentioned above.3 The only exception relates to changes affecting established “grand-father” limits; although a state may not set weight limits above a grandfathered maximum, it may set them below the maximum, provided such a limit is not below the corresponding federal standard.

Size Standards: A state that violates federal statutes on commercial vehicle size, or the implementing regulations, is subject to a civil action in federal district court for injunctive relief, in accordance with 49 U.S.C. 31115, “Enforcement.” The action will be brought by the Department of Justice on behalf of FHWA.

Reporting Requirements: Each year, states must provide the FHWA with both a plan and a certification of accomplishment of planned size and weight enforcement activities. Failure to certify, or inadequately enforce all state laws affecting maximum size and weight on Federal-Aid highways, despite the provision of certifying documents to FHWA, can result in a 10 percent reduction of all Federal-Aid highway funds to the state for the next fiscal year.

State Exceptions and Variations

In addition to the general standards described here, federal law includes provisions, exemptions, and variations applicable to particular states, routes, vehicles, or operations. For more details, please consult 23 CFR Part 658, available on FHWA's Office of Freight Management and Operations website

For more information, please contact

Crystal Jones

1 U.S. Department of Transportation, Federal Highway Administration, Bridge Formula Weights. (Washington, DC: January 1994).
2 U.S. Department of Transportation, Federal Highway Administration. Federal Size Regulations for Commercial Motor Vehicles. (Washington, DC: 1996).
3 See 23 U.S.C. 127(a), as implemented in 23 CFR 658.21, “Procedures for reduction of funds.”
May 2003
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U.S. Department of Transportation, Federal Highway Administration,
Office of Freight Management and Operations, 400 7th Street, SW, Room 3401, Washington, D.C. 20590
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