Improvements Needed in the Department of Transportation's Truck Size and Weight Study

CED-80-41: Published: Jan 14, 1980. Publicly Released: Jan 15, 1980.

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The Department of Transportation's truck size and weight study will be directed by the Intermodal Studies Division within the Office of the Secretary of Transportation. A review of the draft study design indicated a number of areas where modifications should be made. Congress should be aware that the study has been expanded beyond the areas specifically mentioned in implementing legislation and this expansion will require additional data which may require more time than provided for in legislation.

In general, the study plan defines a framework for analyzing the impact of changes in truck weight laws. The work will be divided into seven separate tasks: intermodal competition and traffic diversion; impacts on the highway system; nonuniformity in State truck size and weight laws; impacts on highway and motor carrier safety; impacts on energy use; impacts on the environment; and policy analysis, development, and recommendations. The study plan is based on correlation and analysis of existing highway data with little development of new information. This approach, dictated by time and budget restraints, will make the final study results sensitive to the limitations of existing data and the assumptions that are made when using it. The draft study outlines a general analysis framework but does not discuss the specific assumptions and other matters that will be added during the course of study.

Recommendation for Executive Action

  1. Status: Closed

    Comments: Please call 202/512-6100 for additional information.

    Recommendation: The Secretary of Transportation should require that the study: (1) describe how specific scenarios were analyzed to determine the actual effect on truck weight; (2) consider important determinants of truck weight, including permit and exemption policies, State weight enforcement efforts, and the severity of penalities for overweight violations; (3) include as a scenario the three legislative recommendations in the July 16, 1979 GAO report; and (4) include as a scenario the pre-1975 Federal weight limits of 18,000 pounds for a single axle, 32,000 pounds for a tandem axle, and 73,280 pounds gross vehicle weight. The Secretary should identify all assumptions concerning availability of funds and explain the sensitivity of different funding levels in the study report; and require that the report clearly identify who will pay the costs and who will receive the benefits as determined by analysis of the benefits and costs associated with specific weight limit scenarios. The Secretary should remove excessive reliance on interstate highway statistics and require a clear explanation of the effect of any data limitations in the study report. The Secretary should require that the report include data on State overlay design and policies, and that the data be used in analyzing the impact of weight on payment. Finally, the Secretary should require the study to: include all direct and indirect energy consumption in the energy model analysis; supplement the contractor's highway safety efforts with a survey of current knowledge about the relationship of weight to safety features; and consider, to the extent possible, the impact of weather factors on pavements, especially freeze-thaw cycles.

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