Size & weight restrictions

Truck size and weight restrictions are used to preserve the condition of roadways. The Federal Highway Administration sets the standards for truck size and weight, and states enforce them on the Interstate highway system. 

Key characteristics




WSDOT regions

Other names

  • Overheight detection system

Strategy description

Trucking is a major part of the United States’ economy, and larger/heavier trucks lower per-unit shipping costs to achieve a better economy of scale. However, larger and heavier trucks cause more damage to the condition of roadways. To preserve the roadway infrastructure, the Federal Highway Administration sets maximum standards for vehicle size (length and width) and weight. 

States enforce the Federal truck size and weight maximums on the Interstate highway system and other federally funded roads, to be eligible for Federal highway funding. States must also monitor size and weight restrictions that occur in active work zones to ensure that large vehicles have a viable route through the state. 

Agencies may use size or weight restrictions when the infrastructure does not meet current standards due to construction or old infrastructure. For example, a bridge with a low clearance of the roadway may require a height restriction or a bridge that needs repair may require a weight restriction.

Primarily, agencies use permits to manage oversize/overweight vehicles on the roadway. Oversize trucks must be approved with a permit before operating on the roadway. Occasionally, agencies use technology to detect, warn and divert overheight vehicles before a low clearance bridge. 

When to use this strategy

Size and weight restrictions make sense for States required to enforce the Federal size and weight restrictions on the Interstate highway system. The aging condition of a roadway may also require the restriction of vehicles over a designated height or weight. Construction work zones may also need to enforce width, height or weight restrictions for vehicles moving through the work area.

Strategy benefits:

  • Preserves the condition of the roadway infrastructure
  • Mitigates damage to infrastructure from overweight trucks
  • Reduces collisions with low clearance bridges or in narrow lanes

What you need in order to implement

Planning needs:

  • Develop standards that comply with federally mandated maximums for truck length, width, height, and weight

Coordination needs:

  • Coordinate with local agencies if a size or weight restriction requires an alternate route onto local streets
  • Coordinate with oversize/overweight trucking companies to issue permits to use the roadways

Equipment needs:

  • A state system or website that contains information on all size and weight restrictions
  • Diversion devices, like detection, audible warning horns, and electronic signs, that alert overheight vehicles prior to a low clearance bridge
  • Signs identifying size or weight restrictions to ensure that vehicles do not collide with obstructions
  • Weigh stations and weigh-in-motion technology to enforce the federal standards

Maintenance needs:

  • Maintain the system or website that communicates the size/weight restrictions
  • Maintain site-specific equipment for overheight detection and warning

Agency resources needs:

  • State agencies must enforce the Federal size and weight maximum standards with weigh stations and employees

Learn more about this strategy

Federal Highway Administration (FHWA), Freight Management and Operations, Commercial Vehicle Size and Weight Program.

About key characteristics

Location notes:

Size and weight restrictions can apply to any roadway that has a height, width, or weight restriction caused by active construction, existing over crossings with lower clearance, or existing bridges with weight limits.

Cost notes:

Cost is low to notify the public about size and weight restrictions. The cost becomes high if the agency is trying to remove the restriction because it may require raising an over crossing or building a new bridge.

Technology notes:

Technology may be used to detect and alert an oversize vehicle of an impending height, width or weight restriction so the driver can take an alternate route. The technology requirements are low because an oversize detection and warning system can be deployed at a single location with the restriction, which limits the complexity.

Collaboration notes:

Collaboration is important when restrictions are required for temporary construction because agencies need to ensure alternate routes are maintained that will accommodate oversize (height or width) or overweight vehicles.

Need or issue this strategy addresses