Review of Truck Characteristics as Factors in Roadway Design (2003)

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T R A N S P O R T A T I O N R E S E A R C H B O A R D WASHINGTON, D.C. 2003 www.TRB.org NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM NCHRP REPORT 505 Research Sponsored by the American Association of State Highway and Transportation Officials in Cooperation with the Federal Highway Administration SUBJECT AREAS Planning and Administration • Highway and Facility Design • Highway Operations, Capacity, and Traffic Control Review of Truck Characteristics as Factors in Roadway Design DOUGLAS W. HARWOOD DARREN J. TORBIC KAREN R. RICHARD Midwest Research Institute Kansas City, MO WILLIAM D. GLAUZ Leawood, KS AND LILY ELEFTERIADOU Pennsylvania State University University Park, PA

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation develops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research. In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Board’s recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State Highway and Transportation Officials. Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board. The needs for highway research are many, and the National Cooperative Highway Research Program can make significant contributions to the solution of highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement rather than to substitute for or duplicate other highway research programs. Note: The Transportation Research Board of the National Academies, the National Research Council, the Federal Highway Administration, the American Association of State Highway and Transportation Officials, and the individual states participating in the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the object of this report. Published reports of the NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM are available from: Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet at: http://www.national-academies.org/trb/bookstore Printed in the United States of America NCHRP REPORT 505 Project C15-21 FY 2000 ISSN 0077-5614 ISBN 0-309-08779-1 Library of Congress Control Number 2003114214 © 2003 Transportation Research Board Price $30.00 NOTICE The project that is the subject of this report was a part of the National Cooperative Highway Research Program conducted by the Transportation Research Board with the approval of the Governing Board of the National Research Council. Such approval reflects the Governing Board’s judgment that the program concerned is of national importance and appropriate with respect to both the purposes and resources of the National Research Council. The members of the technical committee selected to monitor this project and to review this report were chosen for recognized scholarly competence and with due consideration for the balance of disciplines appropriate to the project. The opinions and conclusions expressed or implied are those of the research agency that performed the research, and, while they have been accepted as appropriate by the technical committee, they are not necessarily those of the Transportation Research Board, the National Research Council, the American Association of State Highway and Transportation Officials, or the Federal Highway Administration, U.S. Department of Transportation. Each report is reviewed and accepted for publication by the technical committee according to procedures established and monitored by the Transportation Research Board Executive Committee and the Governing Board of the National Research Council.

The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished schol- ars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. On the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and techni- cal matters. Dr. Bruce M. Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Acad- emy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achieve- ments of engineers. Dr. William A. Wulf is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, on its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Acad- emy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both the Academies and the Institute of Medicine. Dr. Bruce M. Alberts and Dr. William A. Wulf are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is a division of the National Research Council, which serves the National Academy of Sciences and the National Academy of Engineering. The Board’s mission is to promote innovation and progress in transportation through research. In an objective and interdisciplinary setting, the Board facilitates the sharing of information on transportation practice and policy by researchers and practitioners; stimulates research and offers research management services that promote technical excellence; provides expert advice on transportation policy and programs; and disseminates research results broadly and encourages their implementation. The Board’s varied activities annually engage more than 4,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individuals interested in the development of transportation. www.TRB.org www.national-academies.org

COOPERATIVE RESEARCH PROGRAMS STAFF FOR NCHRP REPORT 505 ROBERT J. REILLY, Director, Cooperative Research Programs CRAWFORD F. JENCKS, Manager, NCHRP CHRISTOPHER J. HEDGES, Senior Program Officer EILEEN P. DELANEY, Managing Editor HILARY FREER, Associate Editor II ELLEN M. CHAFEE, Assistant Editor NCHRP PROJECT C15-21 PANEL Field of Design—Area of General Design JAKE KONONOV, Colorado DOT (Chair) FRANK CSIGA, Nevada DOT GERALD DONALDSON, Advocates for Highway & Auto Safety, Washington, DC COLIN HUGHES, Calgary, AB, Canada ALBERTO MENDOZA, Mexican Transportation Institute DAN MIDDLETON, Texas Transportation Institute JOHN PEARSON, Council of Deputy Ministers Responsible for Transportation, Canada DUANE PERRIN, NHTSA WILLIAM A. PROSSER, FHWA JOE BARED, FHWA Liaison Representative ELAINE KING, TRB Liaison Representative AUTHOR ACKNOWLEDGMENTS This report was written by Mr. Douglas W. Harwood, Mr. Dar- ren J. Torbic, and Ms. Karen R. Richard of Midwest Research Insti- tute; Dr. William D. Glauz, a consultant in Leawood, Kansas; and Dr. Lily Elefteriadou of Pennsylvania State University. The authors wish to acknowledge the contributions of Dr. Kevin M. Mahoney and Mr. Polanthep Leftworwanich, both of Pennsylvania State Uni- versity. The authors also wish to thank (1) the state departments of transportation of California, Colorado, and Pennsylvania for their assistance in identifying sites on long, steep grades and allowing access to those sites for field data collection on truck speeds; and (2) the state police agencies of Kansas, Missouri, and Texas for pro- viding access to their weigh stations for field data collection on trailer lengths and antilock brake usage.

This report presents guidance for roadway geometric designers on how best to accommodate large trucks on the U.S. highway system. Under NCHRP Project 15-21, a research team reviewed the range of dimensions and performance characteristics of trucks currently used on U.S. highways and pre- dicted how these characteristics may change in response to current political, economic, and technological trends. The research team conducted an analysis of those geometric design features affected by vehicle characteristics and then evaluated the adequacy of current geometric design policy to accommodate the current and anticipated truck fleet. Based on the findings, the report makes recommendations for a number of changes to the AASHTO Policy on Geometric Design of Highways and Streets (“Green Book”). The report (1) provides valuable guidance for designers of roads and facilities that need to accommodate large trucks and (2) will assist AASHTO in updating geometric design policy. The information developed in this project will also be useful as input to future editions of other documents such as the TRB Highway Capacity Manual, the FHWA Manual on Uniform Traffic Control Devices, and the AASHTO Roadside Design Guide. The heavy truck vehicle fleet constitutes a significant percentage of the traffic on major routes in the United States, such as the Interstate highway system. The volume of heavy truck traffic is increasing because of factors that include economic growth; advances in freight transportation logistics, such as just-in-time delivery systems; and changing trade patterns resulting from the North American Free Trade Agreement (NAFTA). To provide a seamless and efficient national highway transportation system, it is important to ensure that the criteria for roadway geometric design are appropriate for the current and anticipated fleet of heavy trucks on U.S. highways. Research was needed on the dimensions, performance, and operational characteristics of the current and future fleet, so that these characteristics can be evaluated and, if necessary, accom- modated on a consistent basis in geometric design standards. Transportation engineers rely on AASHTO’s Policy on Geometric Design of High- ways and Streets for information on design vehicles and roadway design criteria. Heavy truck operating characteristics are treated to a limited extent in the present AASHTO Policy and are based on generalized design vehicles that may not reflect the character- istics of the current fleet. The information currently in the AASHTO Policy needs to be reviewed and updated as appropriate to account for the current and future truck fleet using the U.S. national highway transportation system. Under NCHRP Project 15-21, “Review of Truck Characteristics as Factors in Roadway Design,” the Midwest Research Institute began by reviewing the legal size and weight limits for trucks in U.S. states, as well as limits for Canadian and Mexican FOREWORD By Christopher J. Hedges Staff Officer Transportation Research Board

trucks using U.S. highways under NAFTA. The characteristics of the current fleet were determined by analysis of FHWA and U.S. Census Bureau data. The team then evalu- ated those geometric design features affected by truck characteristics and made rec- ommendations on where changes are needed to the current design policy in order to accommodate the characteristics of the truck fleet. The recommendations include sev- eral changes to the standard design vehicles now in use, as well as four new design vehi- cles reflecting truck configurations that could be permitted in the future under certain scenarios. As part of the research, the team developed a truck speed profile model to predict truck performance on upgrades. The model was implemented as an Excel spreadsheet program that is included with this report on diskette. The spreadsheet pro- gram can be used by highway agencies to anticipate where additional climbing lanes may be warranted.

1 SUMMARY 3 CHAPTER 1 Introduction Background, 3 Research Objectives and Scope, 3 Organization of this Report, 4 5 CHAPTER 2 Truck Size and Weight Limits Federal Truck Size and Weight Limits, 5 State Truck Size and Weight Limits, 5 NAFTA Size and Weight Limits and Performance Criteria, 9 13 CHAPTER 3 Size, Composition, and Characteristics of the U.S. Truck Fleet Number of Trucks in the U.S. Fleet, 13 Truck-Miles of Travel, 13 Truck Types, 16 Truck Length, 18 Truck Gross Weight, 18 Trucks Entering the United States From Canada and Mexico, 19 22 CHAPTER 4 Design Vehicles Overview of Design Vehicles, 22 Future Changes to the U.S. Truck Fleet, 22 Single-Unit Trucks, 27 Truck Tractors, 27 Single-Trailer Combinations (Five-Axle Tractor-Semitrailers), 28 Single-Trailer Combinations (Six-Axle Tractor-Semitrailers), 33 Single-Trailer Combinations (Truck/Full Trailer Combinations), 34 Double-Trailer Trucks, 34 Triple-Trailer Trucks, 37 Summary of Design Vehicle Recommendations, 37 39 CHAPTER 5 Truck Characteristics Related to Geometric Design Turning Radius, 39 Offtracking and Swept Path Width, 39 Trailer Swingout, 43 Braking Distance, 44 Driver Eye Height, 48 Truck Acceleration Characteristics, 49 Speed-Maintenance Capabilities on Grades, 51 Vehicle Length, 55 Vehicle Height, 55 Rearward Amplification, 55 Suspension Characteristics, 56 Load Transfer Ratio, 58 Rollover Threshold, 58 61 CHAPTER 6 Highway Geometric Design Criteria and Their Relationship to Truck Characteristics Stopping Sight Distance, 61 Passing Sight Distance and Passing/No-Passing Zones on Two-Lane Highways, 66 Decision Sight Distance, 76 Intersection Sight Distance, 78 Railroad-Highway Grade Crossing Sight Distance, 87 Intersection and Channelization Geometrics, 89 Critical Length of Grade, 94 Downgrades, 96 Acceleration Lanes, 99 Deceleration Lanes, 102 Lane Width, 102 Horizontal Curve Radius and Superelevation, 103 Pavement Widening on Horizontal Curves, 111 Cross-slope Breaks, 111 Vertical Clearances, 113 114 CHAPTER 7 Conclusions and Recommendations 117 REFERENCES CONTENTS

A-1 APPENDIX A Summary of Truck Characteristics B-1 APPENDIX B Weigh Station Data Collection C-1 APPENDIX C Turning Performance Analysis of Specific Design Vehicles D-1 APPENDIX D Field Estimates of Truck Weight-to-Power Ratios E-1 APPENDIX E Truck Speed Profile Model F-1 APPENDIX F Recommended Changes to the AASHTO Policy on Geometric Design of Highways and Streets