Public Release: 

Federal truck size and weight study falls short of congressional requirements, says new report

National Academies of Sciences, Engineering, and Medicine

WASHINGTON - Although a U.S. Department of Transportation report on federal truck size and weight limits acknowledges gaps in addressing its legislative charge, a more comprehensive and useful response would have been possible, says a new letter report from the National Academies of Sciences, Engineering, and Medicine. The DOT's Comprehensive Truck Size & Weight Limits Study lacks a consistent and complete quantitative summary of the alternative configuration scenarios, and major categories of costs -- such as expected bridge structural costs, frequency of crashes, and infrastructure costs on certain roads -- are not estimated.

DOT asked the Transportation Research Board of the Academies to convene a committee to review its congressionally mandated study of truck size and weight limits. The committee's 2014 letter report reviewed preliminary products of the study. In this final letter report, the committee considered how the DOT study addresses Congress' questions and assessed the appropriateness of the methods and data used to produce estimates of impacts of changes in federal truck size and weight limits on: bridges, pavements, shares of total freight traffic carried by trucks and other freight modes, safety, and enforcement of truck regulations.

The DOT report could have provided a framework for understanding all the costs and benefits, the committee found. Several components can be determined from results of the present and past studies, including a comprehensive list of the categories of costs and benefits; the features of a proposed regulatory change that influence each category; approximate sizes of impacts on shippers, truck operators, road users, and the public; and the categories that are likely to be critical to evaluating regulations. The committee also identified assumptions and simplifications in the DOT study that might result in misleading estimates of infrastructure, traffic, and safety impacts.

Although the Academies' letter report does not take a position on whether or how to change current federal truck size and weight limits, it offers recommendations for improving estimates in each of the impact categories, in order to increase the value of any future truck size and weight studies.

DOT should continue to support areas of research and data development begun in the present study in order to improve exposure data for estimating crash rates, understand the relationship of crash frequency on a road to the traffic volume and mix of vehicle types, and improve the cost-effectiveness of enforcement, the report says.


The Academies' study was sponsored by the U.S. Department of Transportation. The Transportation Research Board is a program of the National Academies of Sciences, Engineering, and Medicine -- private, nonprofit institutions that provide independent, objective analysis and advice to the nation to solve complex problems and inform public policy decisions related to science, technology, and medicine. The Academies operate under an 1863 congressional charter to the National Academy of Sciences, signed by President Lincoln. For more information, visit A committee roster follows.

Dana Korsen, Media Officer
Emily Raschke, Media Assistant
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Copies of Review of U.S. Department of Transportation Truck Size and Weight Study are available at Reporters may obtain a copy from the Office of News and Public Information (contacts listed above).

Transportation Research Board

Committee for Review of U.S. Department of Transportation (USDOT) Truck Size and Weight Study

James J. Winebrake (chair)
Professor and Dean
College of Liberal Arts
Rochester Institute of Technology
Rochester, N.Y.

Imad L. Al-Qadi
Founder Professor of Engineering, and
Director, Illinois Center for Transportation
Department of Civil and Environmental Engineering
University of Illinois

Christopher G. Caplice
Executive Director, Center for Transportation and Logistics
Massachusetts Institute of Technology

Raymond Cook
Lieutenant, and
Director, Commercial Vehicle Safety Section
Pennsylvania State Police

Georgene M. Geary
Principal Engineer
GGfGA Engineering, LLC
Stockbridge, Ga.

Douglas W. Harwood
Program Director, Transportation Research Center
MRI Global
Kansas City, Mo.

Susan E. Hida
Assistant State Bridge Engineer
California Department of Transportation

Jose Holguín-Veras
William H. Hart Professor
Civil and Environmental Engineering, and
Director, Center for Infrastructure, Transportation, and the Environment
Rensselaer Polytechnic Institute
Troy, N.Y.

Brenda M. Lantz
Program Director
Upper Great Plains Transportation Institute
North Dakota State University
Lakewood, Colo.

Sandra Q. Larson
Director, Systems Operations Bureau
Iowa Department of Transportation

Ted R. Miller
Senior Research Scientist
Pacific Institute for Research and Evaluation
Calverton, Md.

Eric Teoh
Senior Statistician
Insurance Institute for Highway Safety
Arlington, Va.

Michael Tooley
Montana Department of Transportation

Joseph R. Morris
Study Director

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