Federal regulations that apply on major U.S. highways govern the weight and width of vehicles and the number of trailers that a power unit may tow. These regulations have important economic consequences because trucking accounts for four-fifths of expenditures on freight transportation in the United States, and trucking costs are influenced by truck size and weight. Size and weight limits also influence highway construction and maintenance costs and highway accident losses. The regulations affect international commerce as well because U.S. limits differ from those of Canada and Mexico and because containers shipped in international trade often are not consistent with U.S. regulations.
The most recent extensive revisions in federal truck size and weight limits were enacted in 1983. Since then there have been changes in the use and characteristics of the highway system, as well as important structural changes in the freight industries. Congress has received proposals for revisions to the federal limits from industry groups, state governments, and others. Proposals for changes in federal regulations governing vehicle size and weight have always been controversial, however, because allowing larger trucks could increase some categories of highway costs and attract freight from railroads to the highways. Trucking firms and shippers’ groups typically advocate liberalization of the limits because larger trucks reduce their costs. The railroad industry, highway safety advocacy groups, some trucking firms (especially smaller ones), and some states oppose increases in federal size and weight limits.
In June 1998, Congress enacted the Transportation Equity Act for the 21st Century (TEA-21, Public Law 105-178), which provided $220 billion in highway and transit funding over 6 years. Section 1213i of the act instructs the Secretary of Transportation to request that the Transportation Research Board (TRB) “conduct a study regarding the regulation of weights, lengths, and widths of commercial motor vehicles . . . and develop recommendations regarding any revisions to law and regulations that the Board determines appropriate.” The act
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Suggested Citation: "1. Introduction." Transportation Research Board. Regulation of Weights, Lengths, and Widths of Commercial Motor Vehicles: Special Report 267. Washington, DC: The National Academies Press, 2002. ×
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stipulates that the study consider regulation of commercial motor vehicles operating on federal-aid highways and that it encompass a review of laws, regulations, other studies, and practices; solicitation of input from the U.S. Department of Transportation (DOT), the states, the motor carrier industry, freight shippers, highway safety groups, air quality and natural resource management groups, and commercial motor vehicle driver representatives; and evaluation of the impact of study recommendations on the economy, the environment, safety, and service to communities. Recommendations are to be addressed to Congress and the Secretary of Transportation. Appendix A contains the text of the section of the act calling for the study.
At the request of DOT, TRB formed the Committee for the Study of the Regulation of Weights, Lengths, and Widths of Commercial Motor Vehicles to conduct the study called for by Congress. This report is the committee’s response to the legislation’s study charge. The first section of this introductory chapter describes the purposes of truck size and weight regulations. The second section identifies the forces that have driven the evolution of these regulations in the past and that are generating calls for change today. The next three sections identify the principal directions for change that have been proposed, outline the challenges confronting reform, and describe the criteria and methods used by the committee in evaluating possible changes.