Guidelines for Guardrail Implementation (2009)

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TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2009 www.TRB.org N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP REPORT 638 Subject Areas Highway and Facility Design Guidelines for Guardrail Implementation Dean L. Sicking Karla A. Lechtenberg Scott Peterson MIDWEST ROADSIDE SAFETY FACILITY UNIVERSITY OF NEBRASKA-LINCOLN Lincoln, NE Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration

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. 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 638 Project 22-12(02) ISSN 0077-5614 ISBN: 978-0-309-11781-4 Library of Congress Control Number 2009903448 © 2009 Transportation Research Board COPYRIGHT PERMISSION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. 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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. 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CRP STAFF FOR NCHRP REPORT 638 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Charles W. Niessner, Senior Program Officer Eileen P. Delaney, Director of Publications NCHRP PROJECT 22-12(02) PANEL Field of Design—Area of Vehicle Barrier Systems Edward T. Paulis, Jr., Maryland State Highway Administration, Timonium, MD (Chair) Brian L. Bowman, Auburn University, Auburn, AL Owen S. Denman, Barrier Systems, Inc., Vacaville, CA Don J. Gripne, Trinity Highway Products, LLC., Olympia, WA Rodney D. Lacy, Kansas DOT, Topeka, KS Charles F. McDevitt, McDevitt Consulting, Matthews, NC Aurora Meza, Texas DOT, Austin, TX Harry W. Taylor, Jr., Taylor Consulting, Washington, DC Steven E. Walker, Alabama DOT, Montgomery, AL Kenneth S. Opiela, FHWA Liaison Stephen F. Maher, TRB Liaison AUTHOR ACKNOWLEDGMENTS The authors wish to acknowledge the National Cooperative Highway Research Program for sponsor- ing this project and the NCHRP Project 22-12 Panel for its guidance. A special thank you is also given to the following individuals at the Midwest Roadside Safety Facility who made a contribution to the comple- tion of this research project: Midwest Roadside Safety Facility John R. Rohde, Associate Professor John D. Reid, Professor Ronald K. Faller, Research Assistant Professor Robert W. Bielenberg, Research Associate Engineer Scott K. Rosenbaugh, Research Associate Engineer C O O P E R A T I V E R E S E A R C H P R O G R A M S

This report provides guidance on selecting the appropriate barrier performance level for the installation of longitudinal barriers. The report presents performance-level selection guidelines to help designers determine the most appropriate guardrail test level for any route. Further, site- specific guidelines not only identify what guardrail test level should be incorporated but also can be used to determine when guardrail use is not cost beneficial. Supplemental procedures for identifying appropriate guardrail test levels have also been developed. These procedures expand the applicability of the guardrail selection guidelines to many unusual hazards that can- not be included in development of general procedures. The report will be of particular interest to designers with responsibility for designing roadside safety features. Recent research has promoted the concept of matching highway-safety features to the type of roadway facility and its traffic conditions. According to NCHRP Report 350: Rec- ommended Procedures for the Safety Evaluation of Highway-Safety Features, a safety fea- ture may be developed to meet one of up to six test levels, depending on the type of feature. Further, a feature may be designed for temporary (work zone) or permanent applications. Under this concept, features developed for the lower test levels, which have minimal con- tainment capabilities for heavier vehicles, may be considered applicable for low-speed, low- volume conditions. While the test levels have been defined, recommended guidelines for their application have only been developed for bridge rails. Transportation agencies (fed- eral, state, and local) are being required to make decisions on the use of features without guidelines on the appropriateness of highway-safety features including permanent and tem- porary traffic barriers, crash cushions, terminals, truck-mounted attenuators, breakaway supports, rumble strips, and cross-sectional elements for specific conditions. The AASHTO Roadside Design Guide (RDG) provides general guidelines to assist design personnel in determining when specific highway-safety features may be needed. The RDG presents these guidelines in terms of roadside terrain features, traffic volumes, design speed, accident probability, and environmental conditions. It does not, however, provide guidance on the specific type of highway-safety feature most appropriate for combinations of these conditions. Objective guidelines are needed not only to identify site conditions where a safety feature is required but also to identify the most appropriate feature for that site. The guidelines should take into account roadway and traffic conditions, and the characteristics of candidate features (e.g., impact performance, life-cycle costs, durability, and maintain- ability). Inappropriate selection of a highway-safety feature at a particular site can be detri- mental to the overall safety of the roadway or wasteful of scarce resources. Under NCHRP Project 22-12(2), “Selection Criteria and Guidelines for Highway Safety Features,” the University of Nebraska-Lincoln used a benefit-cost analysis procedure to F O R E W O R D By Charles W. Niessner Staff Officer Transportation Research Board

develop general guidelines for guardrail implementation. The safety treatment options to be evaluated were identified as well as the relevant parameters needed to describe each alter- native, including safety treatment layout, construction costs, and accident severities. The roadway, roadside, and traffic characteristics of various highway functional classes along with the type and severity of hazards commonly found along each type of roadway were also identified. Specific roadway, roadside, and hazard conditions to be analyzed were then assigned to a set of detailed hazard scenarios that form the basis of a benefit-to-cost analysis. The Roadside Safety Analysis Program (RSAP) was used to analyze each hazard scenario under a wide variety of roadway and traffic characteristics. These RSAP runs were then tab- ulated and used to identify specific locations where various guardrail performance levels should be implemented. These specific guidelines were then generalized to develop route- specific recommendations for guardrail performance levels for each of five different high- way functional classes as a function of traffic volume.

C O N T E N T S 1 Chapter 1 Introduction 1 Objectives 2 Chapter 2 Literature Review 3 Encroachment Probability Models 5 Encroachment Characteristics 8 Crash Costs 9 Solution Method 10 Benefit-to-Cost Analysis 11 Chapter 3 Research Approach 12 Chapter 4 RSAP Input 12 Roadside Hazards 12 Safety Improvement Options and Costs 13 Guardrail Layout 15 Crash Costs 15 Roadway and Roadside Characteristics 17 Traffic Characteristics 18 Chapter 5 Benefit/Cost Analysis 21 Chapter 6 Route-Specific Selection Guidelines 21 Findings 22 Guideline Development 23 Guideline Application 25 Chapter 7 Supplemental Analysis Procedures 25 Supplemental Analysis Examples 28 Chapter 8 Conclusions and Recommendations 29 References 30 Appendices