Transportation Safety:

Federal Highway Administration Should Conduct Research to Determine Best Practices in Permitting Oversize Vehicles

GAO-15-236: Published: Feb 26, 2015. Publicly Released: Feb 26, 2015.

Additional Materials:


Susan Fleming
(202) 512-2834


Office of Public Affairs
(202) 512-4800

What GAO Found

The Department of Transportation's (DOT) Federal Highway Administration (FHWA) has established some federal vehicle size and weight requirements and oversees some state activities. Based on current legislation, FHWA has established rules and regulations for vehicle width, truck trailer length, and vehicle weight standards for certain federal-aid highways aimed at protecting highways and bridges from damage while providing a safe and efficient highway network. FHWA does not, however, have the authority to establish a height requirement, a decision that goes back to the Interstate System's construction in the 1950's, when height clearances already varied from state to state. FHWA also oversees states' processes for enforcing these standards by reviewing states' documentation of enforcement operations. However, FHWA has more limited involvement in individual states' permitting processes and requirements, which the agency considers largely a state matter. For example, it does not provide technical assistance on permitting to states.

Federal Vehicle Size and Weight Standards

Federal Vehicle Size and Weight Standards

State laws and regulations set varying size and weight limits and permitting requirements for vehicles that exceed these limits and that operate on highways and bridges. Specifically, GAO found that the vehicle size and weight limits set by state laws and regulations vary by state, although they are within the parameters of federal requirements. For example, states' length standards vary between the minimum federal standard of 48 feet and 65 feet for a semitrailer. GAO also found that permitting practices for oversize vehicles often vary by state. In some cases, states follow similar practices; for example, most states make use of online permitting systems and escort vehicles that travel with an oversize or overweight vehicle. However, other permitting practices vary by state—such as states' use of automated routing systems to provide a route for oversize vehicles. A National Transportation Safety Board investigation reported that differences among states on the various aspects of truck permitting could be a safety concern. State officials GAO interviewed did not always agree on the benefits of the various permitting practices, and some spoke of the need for more information on this topic. While FHWA is (1) conducting some research on the potential effect of changes to truck size and weight limits and (2) working with the trucking industry to update a best practices guide on escort vehicle operations, it has not studied permitting best practices across states due to lack of authority over state permitting. In GAO's prior work on improving agency performance, GAO found that identifying best practices can help identify changes that might be needed to improve performance. By conducting this type of research, FHWA would be better positioned to help states make sound decisions to improve safety and protect infrastructure.

Why GAO Did This Study

In May 2013, a truck carrying an oversize load crashed into an interstate bridge in Washington state causing it to collapse. This crash raised issues about oversize vehicles and public safety. DOT develops regulations on vehicle size and weight, and states enforce these standards with some oversight from DOT. States also issue their own regulations on vehicle size and weight and issue permits for oversize and overweight vehicles.

The Joint Explanatory Statement of the Consolidated Appropriations Act for Fiscal Year 2014 required GAO to review the role of federal and state agencies in overseeing oversize vehicles. This report discusses (1) how DOT regulates and provides oversight of oversize vehicles and (2) how states regulate oversize vehicles.

GAO collected information from 50 states and the District of Columbia about their permitting practices; reviewed relevant federal legislation and DOT regulations and documents; and interviewed DOT and state officials from a non-generalizable sample of 10 states, chosen based on a variety of considerations, including geographic diversity and types of permitting requirements.

What GAO Recommends

GAO recommends that DOT conduct a study on states' oversize- and overweight-permitting practices, including automated vehicle routing and escort driver certification, to identify areas of best practice and share the results with states. DOT agreed with GAO's recommendation and provided clarifying comments, which GAO incorporated.

For more information, contact Susan Fleming at (202) 512-2834 or

Recommendation for Executive Action

  1. Status: Open

    Comments: The Federal Highway Administration (FHWA) concurred with this recommendation. According to an FHWA letter, they will conduct a review of permitting practices, which will include findings from several recent and ongoing research projects related to oversize and overweight permitting. FHWA plans to complete this review by September 30, 2017, and share the results with states through peer exchanges and forums.

    Recommendation: To improve stewardship over the nation's highways and bridges, the Secretary of Transportation should direct the FHWA Administrator to conduct a study on state oversize- and overweight-permitting practices, including automated vehicle routing and escort driver certification, to identify areas of best practice and share the results with states.

    Agency Affected: Department of Transportation


Explore the full database of GAO's Open Recommendations »

Dec 14, 2017

Dec 4, 2017

Nov 30, 2017

Nov 15, 2017

Nov 2, 2017

Oct 31, 2017

Oct 26, 2017

Oct 5, 2017

Sep 20, 2017

Sep 7, 2017

Looking for more? Browse all our products here