Oct. 8, 2015


Federal Truck Size and Weight Study Falls Short of Congressional Requirements, Says New Report


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 www.nationalacademies.org.  A committee roster follows.



Dana Korsen, Media Officer

Emily Raschke, Media Assistant

Office of News and Public Information

202-334-2138; e-mail news@nas.edu


Twitter: @NASciences



Copies of Review of U.S. Department of Transportation Truck Size and Weight Study are available at www.trb.org.  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