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NATIONAL NCHRP REPORT 518 COOPERATIVE HIGHWAY RESEARCH PROGRAM Safety Evaluation of Permanent Raised Pavement Markers

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TRANSPORTATION RESEARCH BOARD EXECUTIVE COMMITTEE 2004 (Membership as of January 2004) OFFICERS Chair: Michael S. Townes, President and CEO, Hampton Roads Transit, Hampton, VA Vice Chair: Joseph H. Boardman, Commissioner, New York State DOT Executive Director: Robert E. Skinner, Jr., Transportation Research Board MEMBERS MICHAEL W. BEHRENS, Executive Director, Texas DOT SARAH C. CAMPBELL, President, TransManagement, Inc., Washington, DC E. DEAN CARLSON, Director, Carlson Associates, Topeka, KS JOHN L. CRAIG, Director, Nebraska Department of Roads DOUGLAS G. DUNCAN, President and CEO, FedEx Freight, Memphis, TN GENEVIEVE GIULIANO, Director, Metrans Transportation Center and Professor, School of Policy, Planning, and Development, USC, Los Angeles BERNARD S. GROSECLOSE, JR., President and CEO, South Carolina State Ports Authority SUSAN HANSON, Landry University Professor of Geography, Graduate School of Geography, Clark University JAMES R. HERTWIG, President, Landstar Logistics, Inc., Jacksonville, FL HENRY L. HUNGERBEELER, Director, Missouri DOT ADIB K. KANAFANI, Cahill Professor of Civil Engineering, University of California, Berkeley RONALD F. KIRBY, Director of Transportation Planning, Metropolitan Washington Council of Governments HERBERT S. LEVINSON, Principal, Herbert S. Levinson Transportation Consultant, New Haven, CT SUE MCNEIL, Director, Urban Transportation Center and Professor, College of Urban Planning and Public Affairs, University of Illinois, Chicago MICHAEL D. MEYER, Professor, School of Civil and Environmental Engineering, Georgia Institute of Technology KAM MOVASSAGHI, Secretary of Transportation, Louisiana Department of Transportation and Development CAROL A. MURRAY, Commissioner, New Hampshire DOT JOHN E. NJORD, Executive Director, Utah DOT DAVID PLAVIN, President, Airports Council International, Washington, DC JOHN REBENSDORF, Vice President, Network and Service Planning, Union Pacific Railroad Co., Omaha, NE PHILIP A. SHUCET, Commissioner, Virginia DOT C. MICHAEL WALTON, Ernest H. Cockrell Centennial Chair in Engineering, University of Texas, Austin LINDA S. WATSON, General Manager, Corpus Christi Regional Transportation Authority, Corpus Christi, TX MARION C. BLAKEY, Federal Aviation Administrator, U.S.DOT (ex officio) SAMUEL G. BONASSO, Acting Administrator, Research and Special Programs Administration, U.S.DOT (ex officio) REBECCA M. BREWSTER, President and COO, American Transportation Research Institute, Smyrna, GA (ex officio) GEORGE BUGLIARELLO, Chancellor, Polytechnic University and Foreign Secretary, National Academy of Engineering (ex officio) THOMAS H. COLLINS (Adm., U.S. Coast Guard), Commandant, U.S. Coast Guard (ex officio) JENNIFER L. DORN, Federal Transit Administrator, U.S.DOT (ex officio) ROBERT B. FLOWERS (Lt. Gen., U.S. Army), Chief of Engineers and Commander, U.S. Army Corps of Engineers (ex officio) EDWARD R. HAMBERGER, President and CEO, Association of American Railroads (ex officio) JOHN C. HORSLEY, Executive Director, American Association of State Highway and Transportation Officials (ex officio) RICK KOWALEWSKI, Deputy Director, Bureau of Transportation Statistics, U.S.DOT (ex officio) WILLIAM W. MILLAR, President, American Public Transportation Association (ex officio) MARY E. PETERS, Federal Highway Administrator, U.S.DOT (ex officio) SUZANNE RUDZINSKI, Director, Transportation and Regional Programs, U.S. Environmental Protection Agency (ex officio) JEFFREY W. RUNGE, National Highway Traffic Safety Administrator, U.S.DOT (ex officio) ALLAN RUTTER, Federal Railroad Administrator, U.S.DOT (ex officio) ANNETTE M. SANDBERG, Federal Motor Carrier Safety Administrator, U.S.DOT (ex officio) WILLIAM G. SCHUBERT, Maritime Administrator, U.S.DOT (ex officio) ROBERT A. VENEZIA, Program Manager of Public Health Applications, National Aeronautics and Space Administration (ex officio) NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Transportation Research Board Executive Committee Subcommittee for NCHRP MICHAEL S. TOWNES, Hampton Roads Transit, Hampton, VA JOHN C. HORSLEY, American Association of State Highway (Chair) and Transportation Officials JOSEPH H. BOARDMAN, New York State DOT MARY E. PETERS, Federal Highway Administration GENEVIEVE GIULIANO, University of Southern California, ROBERT E. SKINNER, JR., Transportation Research Board Los Angeles C. MICHAEL WALTON, University of Texas, Austin

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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM NCHRP REPORT 518 Safety Evaluation of Permanent Raised Pavement Markers GENI BAHAR CALVIN MOLLETT iTRANS Consulting, Ltd. Richmond Hill, Ontario, Canada BHAGWANT PERSAUD CRAIG LYON Ryerson University Toronto, Ontario, Canada ALISON SMILEY TOM SMAHEL Human Factors North, Inc. Toronto, Ontario, Canada HUGH MCGEE Bellomo-McGee, Inc. (BMI) Vienna, Virginia S UBJECT A REAS Highway Operations, Capacity, and Traffic Control Safety and Human Performance Research Sponsored by the American Association of State Highway and Transportation Officials in Cooperation with the Federal Highway Administration TRANSPORTATION RESEARCH BOARD WASHINGTON, D.C. 2004 www.TRB.org

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NATIONAL COOPERATIVE HIGHWAY RESEARCH NCHRP REPORT 518 PROGRAM Systematic, well-designed research provides the most effective Project G5-17 FY'01 approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local ISSN 0077-5614 interest and can best be studied by highway departments ISBN 0-309-08790-2 individually or in cooperation with their state universities and Library of Congress Control Number 2004102431 others. However, the accelerating growth of highway transportation develops increasingly complex problems of wide interest to 2004 Transportation Research Board highway authorities. These problems are best studied through a coordinated program of cooperative research. Price $20.00 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 NOTICE Department of Transportation. The project that is the subject of this report was a part of the National Cooperative The Transportation Research Board of the National Academies Highway Research Program conducted by the Transportation Research Board with the was requested by the Association to administer the research approval of the Governing Board of the National Research Council. Such approval program because of the Board's recognized objectivity and reflects the Governing Board's judgment that the program concerned is of national understanding of modern research practices. The Board is uniquely importance and appropriate with respect to both the purposes and resources of the suited for this purpose as it maintains an extensive committee National Research Council. structure from which authorities on any highway transportation The members of the technical committee selected to monitor this project and to review subject may be drawn; it possesses avenues of communications and this report were chosen for recognized scholarly competence and with due cooperation with federal, state and local governmental agencies, consideration for the balance of disciplines appropriate to the project. The opinions and universities, and industry; its relationship to the National Research conclusions expressed or implied are those of the research agency that performed the Council is an insurance of objectivity; it maintains a full-time research, and, while they have been accepted as appropriate by the technical committee, research correlation staff of specialists in highway transportation they are not necessarily those of the Transportation Research Board, the National matters to bring the findings of research directly to those who are in Research Council, the American Association of State Highway and Transportation a position to use them. Officials, or the Federal Highway Administration, U.S. Department of Transportation. The program is developed on the basis of research needs Each report is reviewed and accepted for publication by the technical committee identified by chief administrators of the highway and transportation according to procedures established and monitored by the Transportation Research departments and by committees of AASHTO. Each year, specific Board Executive Committee and the Governing Board of the National Research areas of research needs to be included in the program are proposed Council. 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. Published reports of the The needs for highway research are many, and the National NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Cooperative Highway Research Program can make significant contributions to the solution of highway transportation problems of are available from: mutual concern to many responsible groups. The program, however, is intended to complement rather than to substitute for or Transportation Research Board duplicate other highway research programs. Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet at: 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 http://www.national-academies.org/trb/bookstore 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. Printed in the United States of America

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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

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COOPERATIVE RESEARCH PROGRAMS STAFF FOR NCHRP REPORT 518 ROBERT J. REILLY, Director, Cooperative Research Programs CRAWFORD F. JENCKS, NCHRP Manager CHARLES W. NIESSNER, Senior Program Officer EILEEN P. DELANEY, Managing Editor BETH HATCH, Assistant Editor ANDREA BRIERE, Associate Editor NCHRP PROJECT G5-17 PANEL Field of Traffic--Area of Illumination and Visibility STEVE A. McDONALD, Missouri DOT (Chair) THOMAS ABER, Avery Dennison, Niles, IL LISA AULTMAN-HALL, University of Connecticut, Storrs, CT JOHAN J. BEMELEN, Aurora, CO LARRY CHRISTIANSON, Oregon DOT TOM KLEMENT, Ontario Ministry of Transportation, Downsview, Ontario, Canada DAVID C. WOODIN, New York State DOT CARL ANDERSEN, FHWA Liaison Representative PETER HATZI, FHWA Liaison Representative RICHARD PAIN, TRB Liaison Representative AUTHOR ACKNOWLEDGMENTS The research team acknowledges and thanks the valuable assis- Pennsylvania Arthur Breneman tance of staff from the study group states (Illinois, Missouri, New David Mallin Jersey, New York, Pennsylvania, and Wisconsin) for their partici- Larry Hancock pation in the data collection and for answering our numerous ques- Steve Mutchler tions during the data management phase of the safety evaluation Neill Cheers study. Their names are listed below: Ed Sperring Illinois Jennifer Obertino Gaye Luddick Bob Kleinlein Frank Cavataio Rob Robinson George Harley Missouri Steve A. McDonald Bill Hunter Michael Curtit Kory Shope New Jersey John Semler Wisconsin Richard Lange New York Bruce Smith The research team recognizes the participation of the following Jonathan Bray iTRANS staff members: Phoebe Fu, Kevin Shen, Joseph Palmisano, Michael Fay Maurice Masliah, Tara Erwin, Megan Johnson, Margaret Parkhill, Dave Clemens Michael Sone, Errol Tan, and Kenneth Ting. Denise Sandhu

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This report presents the findings of a research project to evaluate the safety per- FOREWORD formance of snowplowable permanent raised pavement markers (PRPMs) on two-lane By Charles W. Niessner roadways and four-lane freeways. An analytical engineering procedure relying on Staff Officer safety performance functions or crash prediction models for roadways with and with- Transportation Research out PRPMs was developed to determine the potential cost-effectiveness of implement- Board ing PRPMs at a location. The report will be of particular interest to traffic engineers with responsibility for installing and maintaining pavement marking systems. PRPMs were introduced for centerline and skip line application as a traffic safety measure to provide more positive guidance for drivers in inclement weather and low- light conditions. These devices have been popular with highway agencies and have been widely used as supplemental delineation treatments to improve driver preview distances. Studies in New York, Texas, and Pennsylvania have raised concerns about the rela- tionship between PRPMs and crash rates. Specifically, the studies conducted in Texas and Pennsylvania indicated potential negative safety effects of these devices. These studies pertained to single jurisdictions only, and their results were questioned because of some identified data and methodological difficulties. In general, there have been few compre- hensive and conclusive studies performed that quantify the safety effects of PRPMs. Under NCHRP Project 5-17, "Safety Evaluation of Permanent Raised Pavement Markers," iTRANS Consulting, Ltd., undertook research to quantify the safety effects of PRPMs and to develop guidelines for their use. This study gathered data in six states (Illinois, Missouri, New Jersey, New York, Pennsylvania, and Wisconsin) to evaluate the safety performance of snowplowable PRPMs at nonintersection locations along two-lane roadways, four-lane expressways, and four-lane freeways. Safety performance functions (or crash prediction models) were developed for var- ious crash types: total, fatal and injury, nighttime, nighttime fatal and injury, daytime, daytime fatal and injury, wet weather, dry weather, and guidance-related. These safety performance functions (SPFs) served as a statistical tool to determine the overall effec- tiveness of PRPMs for particular crash types at the treatment locations. Further disaggregate analysis, using regression techniques, investigated the rela- tionship between the effect of PRPMs on nighttime crashes and various roadway, traf- fic, and PRPM design factors. The purpose of this disaggregate analysis was to deter- mine some of the specific conditions under which PRPMs are effective or not in reducing crashes. The analysis showed the following: The nonselective implementation of PRPMs on two-lane roadways, overall, does not significantly reduce total or nighttime crashes, nor does it significantly increase these crash types. At locations where PRPMs were implemented on the basis of selective policies (i.e., poor crash history, among other criteria), the analyses produced mixed results. Positive effects were found in New York for

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total and nighttime crashes where PRPMs were installed at locations selected on the basis of the wet weather nighttime crash history. Similar safety effects were not found in Pennsylvania, where PRPMs were implemented at locations selected on the basis of total nighttime crash history. The analysis results have also revealed that selective implementation of PRPMs requires a careful con- sideration of traffic volumes and roadway geometry (i.e., degree of curvature). At low volumes (annual average daily traffic [AADT] < 5,000 veh/day), PRPMs can in fact be associated with a negative effect, which is magnified by the pres- ence of sharp curvature. For example, for PRPMs installed on roadways with AADTs ranging between 5,000 and 15,000 veh/day and with a degree of curva- ture greater than 3.5, an increase of nighttime crashes of 26 percent can be esti- mated from the model. Overall, the installation of PRPMs at noninterchange locations on four-lane free- ways showed neither a positive nor a negative overall safety effect on total and nighttime crashes. However, some significant reductions were recorded for wet weather crashes at those locations on four-lane freeways, and there are indica- tions that PRPMs are only effective in reducing nighttime crashes where the AADT exceeds 20,000 veh/day. Because of data-intrinsic constraints, it was not viable to perform a sound safety assessment of the effect of PRPMs on four-lane expressways. The results obtained from the disaggregate analyses were used to develop guidelines for the use of snowplowable PRPMs for two-lane roadways and four-lane freeways. The guidelines are based on a two-step procedure. First, the expected safety benefit after the installation of PRPMs is determined in relation to the expected reduction in future night- time crashes. Second, a positive expected safety effect is followed by an analytical engineering procedure relying on safety performance functions or crash prediction models for roads with and without PRPMs to determine the potential cost-effectiveness of implementing PRPMs at a location. The guidelines are discussed in the context of the present "Manual on Uniform Traffic Control Devices" (MUTCD), and modifications are proposed for future editions.

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CONTENTS 1 SUMMARY 3 CHAPTER 1 Introduction 4 CHAPTER 2 Review of PRPM-Related Literature and Jurisdictional Practices 2.1 Overview of PRPM Current Practices, 4 2.1.1 Nonretroreflective PRPMs, 4 2.1.2 Retroreflective PRPMs, 4 2.1.3 Implementation Criteria and Maintenance Procedures, 5 2.2 Review and Assessment of Knowledge about the Safety Effect of PRPMs, 7 2.2.1 Review of Literature, 7 2.2.2 Methodological Problems in Past Research, 12 2.3 Literature Review of Human Factors Issues and PRPMs, 13 2.3.1 Driver Needs with Respect to Delineation and Visibility, 13 2.3.2 Visibility of PRPMs, 14 2.3.3 Driver Behavior in Response to PRPMs, 17 2.3.4 Summary, 23 24 CHAPTER 3 Data Collection and Preparation 3.1 State Survey and Selection of Potential States for PRPM Safety Evaluation, 24 3.2 Data Collection, 25 3.2.1 PRPM Treatment Sites Inventory, 25 3.2.2 Reference and Comparison Group Sites, 26 3.2.3 Crash Data, 27 3.2.4 Roadway Attribute Data, 28 3.2.5 Traffic Volume Data, 28 3.2.6 Additional Delineation and Guidance Measures, 31 33 CHAPTER 4 Safety Impact Analysis of PRPM Installations 4.1 Composite Analysis Methodology, 33 4.2 Disaggregate Analysis Methodology, 34 4.2.1 Univariate Exploratory Analysis, 34 4.2.2 Multivariate Modeling of the Index of Effectiveness (), 34 4.3 Results of Analyses for Two-Lane Roadways, 35 4.3.1 Composite Analysis, 35 4.3.2 Univariate Disaggregate Analysis, 35 4.3.3 Multivariate Modeling of the Index of Effectiveness (site), 35 4.3.4 Spillover Analysis, 37 4.4 Results of Analysis for Four-Lane Freeways, 37 4.4.1 Composite Analysis, 37 4.4.2 Univariate Disaggregate Analysis, 39 4.4.3 Multivariate Modeling of the Index of Effectiveness (site), 39 4.5 Results of the Composite Analysis for Four-Lane Divided Expressways, 39 40 CHAPTER 5 Discussion of Study Results 5.1 Two-Lane Roadways, 40 5.1.1 Overview of Human Factors Issues, 40 5.1.2 Expected PRPM Impacts on Two-Lane Roadways, 41 5.2 Four-Lane Freeways, 42 5.2.1 Overview of Human Factors Issues, 42 5.2.2 Expected PRPM Impacts on Four-Lane Freeways, 42 44 CHAPTER 6 Guidelines for the Use of Snowplowable PRPMs 6.1 Background, 44 6.2 Proposed Guidelines for PRPMs on Two-Lane Roadways, 45 6.3 Proposed Guidelines for PRPMs on Four-Lane Freeways, 45 6.4 Proposed Revisions to the MUTCD, 45 6.5 Overview of the Analytical Engineering Procedure, 46 6.6 Illustration of the Analytical Engineering Procedure for Two-Lane Roadways, 47 6.6.1 Step 1: Assemble Data to Use SPFs, 47 6.6.2 Step 2: Estimate Expected Nighttime Nonintersection Crashes without PRPMs, 47

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6.6.3 Step 3: Estimate Expected Nighttime Nonintersection Crashes with PRPMs, 48 6.6.4 Step 4: Compare Expected Crashes with and without PRPMs, 49 6.6.5 Step 5: Conduct a Benefit-Cost Analysis, 49 51 CHAPTER 7 Conclusions 53 REFERENCES A-1 APPENDIX A Details of Calibrated Safety Performance Functions