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NATIONAL NCHRP REPORT 559 COOPERATIVE HIGHWAY RESEARCH PROGRAM Communicating Changes in Horizontal Alignment

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TRANSPORTATION RESEARCH BOARD EXECUTIVE COMMITTEE 2006 (Membership as of March 2006) OFFICERS Chair: Michael D. Meyer, Professor, School of Civil and Environmental Engineering, Georgia Institute of Technology Vice Chair: Linda S. Watson, Executive Director, LYNX--Central Florida Regional Transportation Authority Executive Director: Robert E. Skinner, Jr., Transportation Research Board MEMBERS MICHAEL W. BEHRENS, Executive Director, Texas DOT ALLEN D. BIEHLER, Secretary, Pennsylvania DOT JOHN D. BOWE, Regional President, APL Americas, Oakland, CA LARRY L. BROWN, SR., Executive Director, Mississippi DOT DEBORAH H. BUTLER, Vice President, Customer Service, Norfolk Southern Corporation and Subsidiaries, Atlanta, GA ANNE P. CANBY, President, Surface Transportation Policy Project, Washington, DC DOUGLAS G. DUNCAN, President and CEO, FedEx Freight, Memphis, TN NICHOLAS J. GARBER, Henry L. Kinnier Professor, Department of Civil Engineering, University of Virginia, Charlottesville ANGELA GITTENS, Vice President, Airport Business Services, HNTB Corporation, Miami, FL GENEVIEVE GIULIANO, Professor and Senior Associate Dean of Research and Technology, School of Policy, Planning, and Development, and Director, METRANS National Center for Metropolitan Transportation Research, USC, Los Angeles SUSAN HANSON, Landry University Professor of Geography, Graduate School of Geography, Clark University JAMES R. HERTWIG, President, CSX Intermodal, Jacksonville, FL ADIB K. KANAFANI, Cahill Professor of Civil Engineering, University of California, Berkeley HAROLD E. LINNENKOHL, Commissioner, Georgia DOT SUE MCNEIL, Professor, Department of Civil and Environmental Engineering, University of Delaware DEBRA L. MILLER, Secretary, Kansas DOT MICHAEL R. MORRIS, Director of Transportation, North Central Texas Council of Governments CAROL A. MURRAY, Commissioner, New Hampshire DOT JOHN R. NJORD, Executive Director, Utah DOT SANDRA ROSENBLOOM, Professor of Planning, University of Arizona, Tucson HENRY GERARD SCHWARTZ, JR., Senior Professor, Washington University MICHAEL S. TOWNES, President and CEO, Hampton Roads Transit, Hampton, VA C. MICHAEL WALTON, Ernest H. Cockrell Centennial Chair in Engineering, University of Texas at Austin MARION C. BLAKEY, Federal Aviation Administrator, U.S.DOT (ex officio) JOSEPH H. BOARDMAN, Federal Railroad Administrator, U.S.DOT (ex officio) REBECCA M. BREWSTER, President and COO, American Transportation Research Institute, Smyrna, GA (ex officio) GEORGE BUGLIARELLO, Chancellor, Polytechnic University of New York, and Foreign Secretary, National Academy of Engineering (ex officio) SANDRA K. BUSHUE, Deputy Administrator, Federal Transit Administration, U.S.DOT (ex officio) J. RICHARD CAPKA, Acting Administrator, Federal Highway Administration, U.S.DOT (ex officio) THOMAS H. COLLINS (Adm., U.S. Coast Guard), Commandant, U.S. Coast Guard (ex officio) JAMES J. EBERHARDT, Chief Scientist, Office of FreedomCAR and Vehicle Technologies, U.S. Department of Energy (ex officio) JACQUELINE GLASSMAN, Deputy Administrator, National Highway Traffic Safety Administration, U.S.DOT (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) JOHN E. JAMIAN, Acting Administrator, Maritime Administration, U.S.DOT (ex officio) J. EDWARD JOHNSON, Director, Applied Science Directorate, National Aeronautics and Space Administration (ex officio) ASHOK G. KAVEESHWAR, Research and Innovative Technology Administrator, U.S.DOT (ex officio) BRIGHAM MCCOWN, Deputy Administrator, Pipeline and Hazardous Materials Safety Administration, U.S.DOT (ex officio) WILLIAM W. MILLAR, President, American Public Transportation Association (ex officio) SUZANNE RUDZINSKI, Director, Transportation and Regional Programs, U.S. Environmental Protection Agency (ex officio) ANNETTE M. SANDBERG, Federal Motor Carrier Safety Administrator, U.S.DOT (ex officio) JEFFREY N. SHANE, Under Secretary for Policy, U.S.DOT (ex officio) CARL A. STROCK (Maj. Gen., U.S. Army), Chief of Engineers and Commanding General, U.S. Army Corps of Engineers (ex officio) NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Transportation Research Board Executive Committee Subcommittee for NCHRP MICHAEL D. MEYER, Georgia Institute of Technology (Chair) ROBERT E. SKINNER, JR., Transportation Research Board J. RICHARD CAPKA, Federal Highway Administration C. MICHAEL WALTON, University of Texas at Austin JOHN C. HORSLEY, American Association of State Highway LINDA S. WATSON, LYNX--Central Florida Regional and Transportation Officials Transportation Authority JOHN R. NJORD, Utah DOT

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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM NCHRP REPORT 559 Communicating Changes in Horizontal Alignment RICHARD W. LYLES AND WILLIAM C. TAYLOR Department of Civil and Environmental Engineering Michigan State University East Lansing, MI S UBJECT A REAS Highway Operations, Capacity, and Traffic Control 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. 2006 www.TRB.org

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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM NCHRP REPORT 559 Systematic, well-designed research provides the most effective Price $30.00 approach to the solution of many problems facing highway Project 3-61 administrators and engineers. Often, highway problems are of local ISSN 0077-5614 interest and can best be studied by highway departments individually or in cooperation with their state universities and ISBN 0-309-09851-3 others. However, the accelerating growth of highway transportation Library of Congress Control Number 2006923872 develops increasingly complex problems of wide interest to 2006 Transportation Research Board 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 COPYRIGHT PERMISSION Officials initiated in 1962 an objective national highway research Authors herein are responsible for the authenticity of their materials and for obtaining program employing modern scientific techniques. This program is written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the and support of the Federal Highway Administration, United States understanding that none of the material will be used to imply TRB, AASHTO, FAA, Department of Transportation. FHWA, FMCSA, FTA, or Transit Development Corporation endorsement of a The Transportation Research Board of the National Academies particular product, method, or practice. It is expected that those reproducing the was requested by the Association to administer the research material in this document for educational and not-for-profit uses will give appropriate program because of the Board's recognized objectivity and acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. 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 NOTICE cooperation with federal, state and local governmental agencies, The project that is the subject of this report was a part of the National Cooperative universities, and industry; its relationship to the National Research Highway Research Program conducted by the Transportation Research Board with the Council is an insurance of objectivity; it maintains a full-time approval of the Governing Board of the National Research Council. Such approval research correlation staff of specialists in highway transportation 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 matters to bring the findings of research directly to those who are in National Research Council. a position to use them. The members of the technical committee selected to monitor this project and to review The program is developed on the basis of research needs this report were chosen for recognized scholarly competence and with due identified by chief administrators of the highway and transportation consideration for the balance of disciplines appropriate to the project. The opinions and departments and by committees of AASHTO. Each year, specific conclusions expressed or implied are those of the research agency that performed the areas of research needs to be included in the program are proposed research, and, while they have been accepted as appropriate by the technical committee, to the National Research Council and the Board by the American they are not necessarily those of the Transportation Research Board, the National Research Council, the American Association of State Highway and Transportation Association of State Highway and Transportation Officials. Officials, or the Federal Highway Administration, U.S. Department of Transportation. Research projects to fulfill these needs are defined by the Board, and Each report is reviewed and accepted for publication by the technical committee qualified research agencies are selected from those that have according to procedures established and monitored by the Transportation Research submitted proposals. Administration and surveillance of research Board Executive Committee and the Governing Board of the National Research contracts are the responsibilities of the National Research Council 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 NOTE: The Transportation Research Board of the National Academies, the 500 Fifth Street, NW National Research Council, the Federal Highway Administration, the American Washington, DC 20001 Association of State Highway and Transportation Officials, and the individual and can be ordered through the Internet at: states participating in the National Cooperative Highway Research Program do http://www.national-academies.org/trb/bookstore 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. Ralph J. Cicerone 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. Ralph J. Cicerone 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 5,000 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 559 ROBERT J. REILLY, Director, Cooperative Research Programs CRAWFORD F. JENCKS, NCHRP Manager CHARLES W. NIESSNER, Senior Program Officer EILEEN P. DELANEY, Director of Publications ANDREA BRIERE, Editor ELLEN M. CHAFEE, Assistant Editor NCHRP PROJECT 3-61 PANEL Field of Traffic--Area of Operations and Control DAVID NOYCE, University of Wisconsin--Madison (Chair) STEVEN A. MCDONALD, National Engineering Technology Corporation, Jefferson City, MO EMMANUEL OFORI-DARKO, Virginia DOT JAMES L. PLINE, Pline Engineering, Inc., Boise, ID THOMAS M. SCHRIBER, California DOT X. SAM ZHOU, New York State DOT A. J. NEDZESKY, FHWA Liaison RICHARD A. CUNARD, TRB Liaison AUTHOR ACKNOWLEDGMENTS The research reported herein was performed under NCHRP who developed and executed the driver focus groups and who was Project 3-61 by the Department of Civil and Environmental Engi- an observer in the driver observation study; John Elliott (formerly a neering, Michigan State University (MSU). Portions of the project graduate student and currently director of the Erie Redevelopment were also done under subcontract by the Department of Civil Engi- Authority in Erie, Pennsylvania), who did much of the literature neering, North Carolina State University (NCSU). review and who developed and executed the practitioner focus The primary investigators for this project and authors of this groups in Michigan and Indiana; and several other graduate students report are Professor Richard W. Lyles, principal investigator, and who were responsible for preparing materials, coding data, and Professor William C. Taylor of MSU. Other major contributors were analysis, but principal among them was Xinguo Jiang (Joe) and Fred Vanosdall, consultant, who developed and executed the driver Anthony Ingle. Special recognition is also offered to Hannah observation study; Professor Joseph Hummer of NCSU, who was Remtema, who assisted with initial work on the original project pro- responsible for the parts of the driver surveys and practitioner focus posal and worked on the project for its duration (survey develop- groups done in North Carolina; Stephanie Aldighieri (formerly a ment and execution, data coding, data analysis, and observation in graduate student at MSU and currently with the Michigan DOT), the driver study) as an undergraduate and then as a graduate student.

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This report presents the findings of a research project to develop guidelines for the FOREWORD use of traffic control devices for communicating changes in horizontal alignment for By Charles W. Niessner two-lane, two-way rural roads. The report will be of particular interest to traffic engi- Staff Officer neering personnel with responsibility for roadway signing. Transportation Research Board Highway curves tend to be high-rate crash locations. The average crash rate for highway curves is about 3 times the average rate for highway tangents, and the average run-off-the-road crash rate for highway curves is about 4 times that of highway tangents. In lieu of curve-flattening practices or other geometrically based enhancements that are rarely employed on local road systems, traffic control devices offer the most poten- tial for reducing crash rates on horizontal curves. Warning signs (such as turn, curve, winding road, large arrow, and chevrons) with or without advisory speed plaques and a variety of delineation devices (such as wide edge lines, post delineators, raised pave- ment markers, and rumble strips) are used to communicate changes in horizontal align- ment. Nevertheless, such devices are used inconsistently from one jurisdiction to another and even from one location to another within a single jurisdiction, and they are sometimes used improperly. The devices related to horizontal alignment are rarely con- sidered as a system, but merely a collection of individual devices. Jurisdictions have varying practices regarding the spacing of delineation devices with changes in horizontal alignment; existing devices for roads with multiple changes in horizontal alignment do not provide speed information for each individual alignment change. For example, in a reverse curve with a 40-mph advisory speed, the first curve may be negotiable at 50-mph, leading to a false sense of security and a failure to slow for the second curve that has the 40-mph advisory speed or a single curve with a 30-mph advisory speed may be negotiated at 45-mph leading to distrust for advisory signing. Several recent studies have concluded that the current methodology for select- ing advisory speeds is outdated and needs to be reevaluated. Elements such as weather, roadway classification, road user familiarity, and commercial vehicle types may also affect the appropriate advisory speed Under NCHRP Project 3-61, "Communicating Changes in Horizontal Alignment," Michigan State University researchers developed three recommendations for changes to the Manual of Uniform Traffic Control Devices. The research team reviewed the literature and ongoing research to identify design methods, practices, and problems in determining and communicating horizontal curve information to road users. Focus group exercises and interview sessions involving prac- titioners were held in Michigan, North Carolina, and Indiana. And a national survey was conducted. The objective was to determine the perceptions and actual practice of practitioners regarding traffic control devices used for horizontal curves: are they ade- quate, are they used consistently, and should guidelines for use be changed?

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A driver behavior study using Driver Performance Monitoring (DPM) techniques was also conducted. Randomly selected drivers were observed as they traversed a 25-mile predetermined route, negotiating 43 curves. Trained observers assessed the driver's "search, speed, and direction control" as they negotiated the curves. The vehi- cle's speedometer readings at various points were also recorded as were comments on driving behavior. Using the information from the literature review, survey responses, input from the focus groups, and the DPM study the researchers developed several recommendations for changes to the Manual of Uniform Traffic Control Devices.

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CONTENTS S-1 SUMMARY 1 CHAPTER 1 Introduction and Research Approach Problem Statement and Research Objective, 1 Scope of Study, 1 Research Approach, 1 Report Organization, 1 2 CHAPTER 2 Findings Literature Review, 2 Curve and Turn Signs, 2 Advisory Speeds, 2 Chevrons, 3 Edgelines and Centerlines, 3 Post-Mounted Delineators, 3 Raised Pavement Markers, 3 Discussion and Comments, 3 Practitioner Focus Groups, 4 Practitioner Survey, 6 Driver Focus Groups, 7 Crash-Involved and Typical/Average Driver Survey, 8 Field Study of Driver Behavior Using Driver Performance Monitoring Technique, 10 General DPM Route Description, 10 DPM Subjects, 10 DPM Results, 10 Discussion of DPM Results, 12 Overall Summary and Recommendations, 14 Anecdotal Observations Based on DPM Subject Performance, 15 16 CHAPTER 3 Initial Guidelines and Recommendations for Changes to the MUTCD Introduction, 16 Findings from this Study Related to Uniformity, 17 Recommended Changes to the MUTCD, 17 First Change, 17 Second Change, 18 Third Change, 18 Other Recommendation, 19 20 CHAPTER 4 Practitioner Opinion on Proposed MUTCD Changes Introduction, 20 Final Practitioner Survey Results, 20 First Recommendation (Changing "May" to "Should" Regarding Use of Basic Curve Signs), 20 Second Recommendation (Use of Advisory Speed Plaques), 21 Third Recommendation (Engineering Study), 21 Fourth Recommendation (Expert System), 22 26 CHAPTER 5 Revised Recommendations for the MUTCD and Related Changes Introduction, 26 First Recommendation, 26 Initial Proposed Statement, 26 Existing Statements in the MUTCD, 26 Final Proposed Statement, 26 Second Recommendation, 27 Initial Proposed Statement, 27 Existing Statements in the MUTCD, 27 Final Proposed Statement, 27 Third Recommendation, 28 Initial Proposed Statement, 28 Final Proposed Statement, 28 Fourth Recommendation, 29 Initial Proposed Statement, 29 Final Proposed Statement, 29 Concluding Remarks, 29 31 BIBLIOGRAPHY