Commercial vehicles and loads are generally of a size and weight that allows them to freely travel on our nation’s highways; however, some are too large or too heavy (or both) to operate on a highway without posing a safety risk or potentially damaging highway infrastructure. A vehicle and load is considered oversized when the vehicle and the cargo it carries exceed the legal dimensions of length or width, as defined by federal requirements or length, height, or width as defined by state requirements for the state in which the vehicle will be traveling (see fig. 1). A vehicle and load is considered overweight when the vehicle and the cargo it carries exceed the legal weight limit as defined by federal and state requirements. When vehicles and loads exceed federal or state size and weight limits, carriers are generally required to reduce the size of the load to within the limits, if possible. Specifically, carriers must divide oversize or overweight loads of bulk goods such as corn, gravel, or mail into smaller loads unless they have special exceptions.overweight loads, such as sections of wind turbine towers, may receive permits to travel on a highway, if they can be safely transported without damaging pavements or bridges as determined by state requirements (see fig. 2). FHWA has established some federal vehicle size and weight requirements, collects some information on state enforcement practices, and provides some technical assistance to states related to truck size and weight issues. Federal laws and FHWA regulations establish standards for vehicle width, weight, and length on some of the nation’s highways. Width and weight standards are set at maximums. The width standards generally require states to allow vehicles to be up to, but not exceed, 8 feet 6 inches wide (see fig. 4). Similarly, the weight standards generally require states to allow vehicles to be up to, but not exceed, 80,000 pounds in total vehicle weight. States cannot set lower width or weight maximums when these federal standards apply. Vehicles exceeding these width and weight standards are considered overwide or overweight. The federal length standards differ from the above width and weight standards in that they do not establish a maximum overall length for a vehicle. The length standard is a minimum standard set to ensure interstate commerce is not impeded by a state’s requirements. The regulation provides only that states may not require permits for vehicles with trailers that are less than a specific length, which depends on the type of vehicle. For example, states cannot require trucks with a single trailer to obtain a permit for a trailer that is less than 48 feet. However, states may allow longer vehicles or trailers to travel without requiring a permit. According to FHWA officials, federal length and width standards are set to enhance interstate commerce by ensuring carriers can travel from state to state without undue restrictions on vehicle size. Maximum width standards are set to minimize infrastructure damage and assure safe traffic operations, and maximum weight standards are primarily to protect highways and bridges from damage from excessive weight and to assure safe traffic operations. FHWA’s federal vehicle width, length, and weight regulations apply to a small percentage of the nation’s highways. There are approximately 4,093,000 total miles of public highways and roads in the United States, and federal size and weight standards apply to designated highways of national importance, as shown in figure 5. The National Network connects cities on highways capable of safely handling larger commercial vehicles for interstate commerce. FHWA’s vehicle size (width and length) regulations apply to the entire 200,000 miles in the National Network, which includes the Interstate System, while the weight regulations apply to the 47,000-mile Interstate System, and not the larger National Network. Also, the National Highway System (NHS)—those highways important to the nation’s economy, defense, and mobility—is supported with improvement projects funded by almost $22 billion in federal-aid highway funds in fiscal year 2014. The federal size and weight regulations do not apply to about 50,000 miles of the 223,000 miles of the NHS. Therefore, size and weight regulations are applied differently and not on all types of federal highways. The federal size regulations apply to less than 5 percent, and the federal weight regulations apply to a little over 1 percent, of the over 4 million miles of public highways and roads. States can set their own size and weight standards where a federal standard does not apply to a certain highway, which can be either more or less restrictive than the federal standards, depending on the type of standard. For example, while the State of Michigan follows the federal width standard (8 feet 6 inches) for vehicles on the highways covered by federal regulations or on special state-designated highways, on all other highways, a truck’s width cannot exceed a more restrictive state standard of 8 feet 0 inches. Conversely, New York is less restrictive on trailer lengths and allows 53 feet 0 inch long trailers—five feet longer than the minimum length states must allow on highways covered by federal regulations. Further, federal standards have not been established for all aspects of vehicle size allowed on certain highways of national importance. Specifically, Congress has not set a vehicle height requirement, nor given FHWA the authority to do so, for any federal highway. FHWA officials said that the decision to not have a federal height standard goes back to a decision made in the 1950’s when the Interstate System was being constructed and the height clearances already varied from state to state. All states have set a maximum height at, or above, the standard semi- trailer height of 13 feet- 6 inches. In addition, while there are weight standards for the almost 47,000 mile Interstate System, there are no federal weight standards for the approximately 176,000 miles of highways on the federally important NHS and 153,000 miles of the National Network that are not on the Interstate System, as mentioned earlier. As a result, states determine the maximum truck height, length, and weight allowed and when a permit is required for these highways. Given these limits in federal standards for vehicle size and weight, states have the flexibility to set their own standards; however, as shown in the following sections, this flexibility results in a variance from state to state. In addition to establishing size and weight standards, FHWA oversees some state activities related to oversize and overweight vehicles and loads. FHWA’s Office of Freight Management and Operations in Washington, D.C., and staff in each of FHWA’s 52 Division Offices are responsible for communicating with states on federal standards regarding vehicle size and weight. FHWA requires states to prepare and submit an annual Truck Size and Weight Certification (Certification) and State Enforcement Plan. FHWA Division Offices are to review these documents to verify that each state is enforcing vehicle size and weight laws, and that state laws do not conflict with federal laws. Further, based on these documents and review of the states’ size and weight enforcement operations, the division offices are to prepare an evaluation report for each state. If states do not provide their annual certification, or the Secretary of Transportation (Secretary) determines that a state is not adequately enforcing all state laws on the Interstate System and other federal-aid routes, then the Secretary can withhold 7 percent of that state’s federal-aid highway funding while the state is given an opportunity to come into conformity with federal regulations or appeal the Secretary’s decision. If the state fails to certify, or the certification is rejected and the state’s appeal process is exhausted, the Secretary is required by law to redirect the 7 percent of the state’s federal funding previously withheld to other states. FHWA officials stated that they and state officials work together to correct problems with the certifications to avoid withholding funding from states and, as a result, have not withheld or redirected funding from any state since fiscal year 1992. Pub. L No. 112-141, § 32801, 126 Stat. 405, 816 (2012). MAP-21 is the current authorization act for surface transportation programs and expired at the end of fiscal year 2014. Programs and budget authority authorized by MAP-21 were extended to May 31, 2015. Pub. L. No. 113-159, § 1001(a),128 Stat. 1839, 1840 (2014). Among other things, section 32801 of MAP-21 required DOT to conduct a comprehensive truck size and weight limits study addressing differences in safety risks, infrastructure impacts, and the effect on levels of enforcement between trucks operating at or within federal truck size and weight limits and trucks legally operating in excess of federal limits. emergencies as set out in on MAP-21. Additionally, FHWA in cooperation with the trucking industry and the Commercial Vehicle Safety Alliance funded the development of pilot car escort and law enforcement escort best practices guides in 2004. FHWA officials told us that they are planning to provide staff support to update the pilot car escort best practices guide including providing research on stakeholder-identified priority areas, such as vehicle operations.funds administered by FHWA can be used by states in constructing some infrastructure, such as weigh stations, to enforce weight standards. FHWA’s policy is to provide a safe and efficient highway network that can accommodate large vehicles, but FHWA plays a limited role in permitting oversize and overweight vehicles for several reasons. While FHWA’s regulations establish standards for vehicle size and weight, according to FHWA officials, FHWA lacks the statutory authority to establish any requirements for state permitting. According to these officials, permitting practices are largely a state matter, and thus they do not keep records of states’ permitting requirements or provide technical assistance on permitting to states. Officials from the 10 states we interviewed told us that the federal government provides them with little or no guidance on permitting. However, state transportation agencies—through their membership in AASHTO—have efforts under way to harmonize size and weight requirements and conditions under which they issue oversize and overweight vehicle permits. FHWA assists in an advisory role in this effort. FHWA officials told us that states are now working on changes to state administrative rules in order to harmonize requirements.