In-Service Performance of Traffic Barriers (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 490 Research Sponsored by the American Association of State Highway and Transportation Officials in Cooperation with the Federal Highway Administration SUBJECT AREAS Highway and Facility Design • Safety and Human Performance In-Service Performance of Traffic Barriers M. H. RAY, J. WEIR, AND J. HOPP Worcester Polytechnic Institute Worcester, MA

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 490 Project C22-13(2) FY’99 ISSN 0077-5614 ISBN 0-309-08762-7 Library of Congress Control Number 2003108638 © 2003 Transportation Research Board Price $26.00 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 490 ROBERT J. REILLY, Director, Cooperative Research Programs CRAWFORD F. JENCKS, Manager, NCHRP CHARLES NIESSNER, Senior Program Officer EILEEN P. DELANEY, Managing Editor ELLEN M. CHAFEE, Assistant Editor NCHRP PROJECT C22-13(2) PANEL Field of Design—Area of Vehicle Barrier Systems SAMUEL A. JOHNSTON, Oregon DOT (Chair) MARYBETH BOSSOLINI, Troy, NY OWEN S. DENMAN, Barrier Systems, Inc., Sacramento, CA MONIQUE R. EVANS, Ohio DOT JAMES A. HATTON, JR., Montgomery Village, MD JOHN JEWELL, California DOT JARVIS D. MICHIE, JDM Consulting Engineering, San Antonio, TX JOSEPH P. TARRIS, Kilareksi and Tarris, State College, PA HARRY W. TAYLOR, JR., FHWA JOHN G. VINER, Durango, CO JERRY W. WEKEZER, Florida A&M University-Florida State University CHARLES F. MCDEVITT, FHWA Liaison Representative STEPHEN F. MAHER, TRB Liaison Representative AUTHOR ACKNOWLEDGMENTS A number of people were involved with collecting data in Con- necticut, North Carolina and Iowa, including Mr. William Hunter, Mr. David Harkey and Mr. Tom Meadows of the University of North Carolina’s Highway Safety Research Center; Mr. Dan McGehee and Ms. Mireille Raby of the University of Iowa’s Public Policy Center; Mr. Jeff Hopp and Mr. Dav Nemovitz of the University of Iowa’s Center for Computer Aided Design; and Dr. Kathleen Hancock, Mr. Mike Fitzpatrick and Mr. Keshavan of the University of Massachusetts. In addition to the project team, the authors would like to thank the police officers and DOT personnel who assisted the research team in the data collection. The authors would also like to thank Mr. David Little of the Iowa DOT for his assistance during the project and his many helpful comments.

This report presents the findings of a research project to develop a practical proce- dures manual for conducting in-service performance evaluations of roadside barriers. The report will be of particular interest to safety practitioners with responsibility for roadside safety improvements. Significant improvements in highway safety have been achieved through a multi- tude of actions over the past three decades, but one area where serious problems still exist is the highway roadside. Crash data indicate that more than 40% of highway fatal- ities involve vehicles hitting objects on the roadside, including barriers. Highway designers attempt to address these roadside safety problems by minimizing the number of objects, providing adequate clear zones, or using barriers to shield the vehicles from the hazard. Several generations of barriers have been developed to improve safety, but the effectiveness of these barriers in the field is not fully understood. While crashwor- thiness criteria have been established in NCHRP Report 350, Recommended Proce- dures for the Safety Performance Evaluation of Highway Features, the tests are based on idealized installations of barriers. In field installations, the barrier may be located on a slope, struck at different angles, subjected to the effects of settlement, and may be installed and maintained inconsistently. In addition, crashes not reported to the police confound attempts to determine the true in-service performance of barriers. Further, when assessing barrier performance factors such as injury risk, it is necessary to con- sider the changing characteristics of the vehicle fleet (e.g., airbags). These and other factors can influence in-service performance of barriers, but there has been only lim- ited effort to investigate their effects. Transportation agencies need guidance on the in-service performance of traffic barriers to make effective decisions on their use under specific conditions. The Amer- ican Association of State Highway and Transportation Officials (AASHTO) Roadside Design Guide (RDG) provides general guidelines to assist design personnel in deter- mining when safety treatments may be needed. The RDG presents these guidelines in terms of roadside terrain, traffic volumes, design speed, crash probability, and envi- ronmental conditions. This guidance is limited to general references to applicability under specific roadside conditions because in-service performance data are inadequate. Thus, needs exist for (1) in-service performance data for roadside barriers; (2) a pro- cedure(s) to efficiently gather these data on a regular basis; and (3) a process to com- pile, maintain, and share these data in efforts to improve roadside safety. Under NCHRP Projects 22-13 and 22-13(2), “In-Service Performance of Traf- fic Barriers” and “Expansion and Analysis of In-Service Barrier Performance Data and Planning for Establishment of a Database,” respectively, Worcester Polytech- nic Institute developed a procedures manual for conducting in-service performance evaluations. FOREWORD By Charles Niessner Staff Officer Transportation Research Board

The research team reviewed the literature to identify past and current in-service evaluation studies and determined what methods had been previously effective. An in- service evaluation was planned and performed in portions of the states of Connecticut, Iowa, and North Carolina. The in-service performance of common barriers and termi- nals was examined by collecting crash, maintenance, and inventory information in the three data collection areas. The information was supplemented with visits to the crash sites to make measurements of the damaged barrier and document the collision scene using photographs. A procedures manual for planning and conducting in-service eval- uations of roadside hardware was developed based on the methods used and the lessons learned in the evaluation study. The manual was subsequently used as a guide for an in-service evaluation project performed in Washington State by a different research team and modified based on their experiences and recommendations. The procedures can be used as a general framework for developing and perform- ing an in-service performance evaluation of a roadside feature. They are based on tech- niques that have been used in other in-service performance evaluations as well as other collision data studies. The procedures are intended to be used by design and mainte- nance engineers and do not require that the collisions be reconstructed. The procedures can be implemented into the routine operations of many roadway maintenance organi- zations and used as an ongoing management tool. The pilot studies have demonstrated that in-service performance evaluations can yield useful information about the field performance of roadside features. The researchers concluded that in-service performance evaluations should be integrated more fully into the overall cycle of design, test, and evaluation of roadside hardware. The results of such evaluations will allow state DOTs to develop policy and mainte- nance procedures based on observable field phenomena rather than speculation and conjecture.

1 CHAPTER 1 Introduction Roadside Feature Design Process, 1 Purpose of In-Service Evaluations, 1 In-Service Evaluation Recommendations, 2 Comparison of Crash Tests and In-Service Evaluations, 3 Benefits of In-Service Evaluations, 4 Scope of This Study, 5 7 CHAPTER 2 Literature Review Introduction, 7 Historical Studies, 7 Collision Studies, 12 In-Service Evaluations, 20 Procedural Studies, 27 Discussion and Conclusions, 28 31 CHAPTER 3 Data Collection Areas Connecticut Data Collection Area, 31 Iowa Data Collection Area, 34 North Carolina Data Collection Area, 38 Conclusions, 41 42 CHAPTER 4 Procedures Development Process, 42 Summary, 42 51 CHAPTER 5 In-Service Performance Evaluation of the BCT and MELT Guardrail Terminals in Iowa and North Carolina 51 CHAPTER 6 In-Service Performance Evaluation of the Bullnose Median Barrier in the State of Iowa 51 CHAPTER 7 In-Service Performance Evaluation of Post-and-Beam Guardrails in Connecticut, Iowa, and North Carolina 51 CHAPTER 8 Videolog Assessment of Vehicle Collision Frequency with Concrete Median Barriers on an Urban Highway in Connecticut 52 CHAPTER 9 Conclusions and Recommendations Introduction, 52 Literature Review, 52 Data Collection Areas, 53 Procedures, 54 BCT and MELT Terminals, 54 Bullnose Median Barriers, 55 Guardrails, 55 Recommendation, 55 56 REFERENCES A-1 APPENDIX A Bibliography D-1 APPENDIX D In-Service Performance Evaluation Procedures Manual CONTENTS