Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page R1
NATIONAL NCHRP REPORT 524 COOPERATIVE HIGHWAY RESEARCH PROGRAM Safety of U-Turns at Unsignalized Median Openings
OCR for page R2
TRANSPORTATION RESEARCH BOARD EXECUTIVE COMMITTEE 2004 (Membership as of July 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, CSX Intermodal, Jacksonville, FL GLORIA J. JEFF, Director, Michigan 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 and Department of Civil and Material Engineering, University of Illinois, Chicago MICHAEL D. MEYER, Professor, School of Civil and Environmental Engineering, Georgia Institute of Technology CAROL A. MURRAY, Commissioner, New Hampshire DOT JOHN E. NJORD, Executive Director, Utah DOT DAVID PLAVIN, President, Airports Council International, Washington, DC JOHN H. REBENSDORF, Vice President, Network Planning and Operations, 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, Executive Director, LYNX--Central Florida Regional Transportation Authority, Orlando, FL 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) 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) BETTY MONRO, Acting Administrator, Federal Railroad Administration, U.S.DOT (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) ANNETTE M. SANDBERG, Federal Motor Carrier Safety Administrator, U.S.DOT (ex officio) WILLIAM G. SCHUBERT, Maritime 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) 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
OCR for page R3
NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM NCHRP REPORT 524 Safety of U-Turns at Unsignalized Median Openings INGRID B. POTTS DOUGLAS W. HARWOOD DARREN J. TORBIC KAREN R. RICHARD Midwest Research Institute Kansas City, MO JEROME S. GLUCK Urbitran Associates New York, NY HERBERT S. LEVINSON New Haven, CT AND PHILIP M. GARVEY RAMY S. GHEBRIAL Pennsylvania State University State College, PA S UBJECT A REAS Highway and Facility Design 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
OCR for page R4
NATIONAL COOPERATIVE HIGHWAY RESEARCH NCHRP REPORT 524 PROGRAM Systematic, well-designed research provides the most effective Project G17-21 FY'00 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 0-309-08805-4 individually or in cooperation with their state universities and Library of Congress Control Number 2004111239 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 $24.00 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
OCR for page R5
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 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
OCR for page R6
COOPERATIVE RESEARCH PROGRAMS STAFF FOR NCHRP REPORT 524 ROBERT J. REILLY, Director, Cooperative Research Programs CRAWFORD F. JENCKS, Manager, NCHRP B. RAY DERR, Senior Program Officer EILEEN P. DELANEY, Director of Publications HILARY FREER, Editor NCHRP PROJECT G17-21 PANEL Field of Traffic--Area of Safety PATRICK T. MCCOY, University of Nebraska--Lincoln (Chair) (Deceased) W. MARTIN BRETHERTON, JR., P.E., Gwinnett County (GA) DOT PHILIP B. DEMOSTHENES, Parametrix, Denver, CO MARYAM GHYABI, P.E., Ghyabi, Lassiter & Associates, Deland, FL KURT KUNDE, P.E., Grand Ledge, MI DAVID NOYCE, P.E., University of WisconsinMadison RICHARD F. TWARDOKUS, P.E., Bloomfield, NY JOE BARED, P.E., FHWA Liaison Representative RICHARD A. CUNARD, P.E., TRB Liaison Representative
OCR for page R7
This report presents guidelines for locating and designing unsignalized median FOREWORD openings. A methodology is included for comparing the relative safety performance of By B. Ray Derr different designs. Primarily, geometric designers for both state and local agencies will Staff Officer benefit from the report, but it will also be useful to those discussing the impacts of Transportation Research installing medians with business and property owners. Board Designs for nontraversable medians vary widely and the safety and operational effects of the different designs have not been well documented. A thorough review of the safety and operational effects of the various designs was needed, both for setting design policy and in project-level design. Transportation agencies often face resistance to installing nontraversable medians on multilane highways. One of the arguments made is that the number of U-turning vehicles will increase. However, the effect of an increase in U-turns on the safety of the road is not clear. Studies attributing safety gains to a nontraversable median have not focused on the specific situation at the median opening, either isolated or at an inter- section, where U-turns occur. After a nontraversable median has been installed, agencies are often approached by abutting property owners who want a new median opening. Additional information would be helpful in reviewing these requests, determining if an opening should be allowed, and developing a design that does not unduly affect the safety or operation of the road. In NCHRP Project 17-21, Midwest Research Institute and their subcontractors determined state and local agency design practices and policies related to unsignalized median openings for U-turns. After promising designs were identified, their effects on safety were assessed through field observation and crash data analysis. The knowledge gained was distilled into design guidelines and a methodology for comparing the expected safety performance of different designs.
OCR for page R8
CONTENTS 1 SUMMARY 3 CHAPTER 1 Introduction Background, 3 Research Objectives and Scope, 3 Organization of This Report, 3 5 CHAPTER 2 Literature Review Location of Median Openings, 5 Spacing of Median Openings, 6 Safety of Median Openings, 7 Median Width, 8 Median Opening Length, 10 Safety Effects of Median Treatments (Raised/Depressed/Flush/TWLTL), 10 Safety Effects of Increasing U-Turn Maneuvers Through Use of Nontraversable Medians, 15 Left-Turn Lanes, 16 Median Acceleration Lanes, 18 Loons to Assist Larger Vehicles in Completing U-Turn Maneuvers, 20 Sight Distance at Median Openings, 20 Indirect Left-Turn Maneuvers, 21 Access Management, 24 Spacing Between Access Points, 25 Effects of Adjacent Traffic Signals, 26 27 CHAPTER 3 Current Design Policies and Practices of Highway Agencies Survey Recipients, 27 Response Rate, 27 Location and Design of Median Openings, 27 Treatment of U-Turns at Median Openings, 28 Median and Roadway Widths to Accommodate U-Turn Maneuvers, 31 Traffic Operational and Safety Problems at Median Openings, 32 Mitigation Measures for Safety Problems, 32 33 CHAPTER 4 Classification and Assessment of Typical Median Opening Designs Factors Used in Classification of Median Opening Designs, 33 Overview of Typical Median Opening Designs, 34 Factors That Influence the Safety and Operational Performance of Median Openings, 42 Relative Safety of Median Opening Designs Based on Traffic Conflict Points, 52 Combinations of Median Openings Along Arterial Streets, 53 59 CHAPTER 5 Data Collection and Analysis Catalog of Existing Median Openings, 59 Data Collection and Analysis for Selected Median Openings, 62 68 CHAPTER 6 Findings Accident and Field Data, 68 Median Opening Accident Frequencies, 68 Median Opening Accident Rates, 69 Median Opening Conflict Rates, 71 Comparison of Median Opening Accident and Conflict Rates, 72 Combinations of Median Openings, 74 79 CHAPTER 7 Conclusions and Recommendations Conclusions, 79 Recommendations, 80 81 REFERENCES A-1 APPENDIX A Highway Agency Survey Questionnaire B-1 APPENDIX B Summary of Survey Responses From State and Local Highway Agencies C-1 APPENDIX C Guidelines for the Use, Location, and Design of Unsignalized Median Openings