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
