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Alternative Intersection Design and Selection A Synthesis of Highway Practice Henry Brown Praveen Edara Grace Hartman University of MissoUri Columbia, MO Gil Chlewicki AdvAnced trAnsportAtion solUtions Rockville, MD 2020 Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration Subscriber Categories Design â¢ Highways â¢ Operations and Traffic Management 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 SYNTHESIS 550
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 by going to http://www.national-academies.org and then searching for TRB Printed in the United States of America NCHRP SYNTHESIS 550 Project 20-05, Topic 50-11 ISSN 0547-5570 ISBN 978-0-309-48138-0 Library of Congress Control Number 2020935938 Â© 2020 National Academy of Sciences. All rights reserved. COPYRIGHT INFORMATION 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. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FTA, GHSA, NHTSA, or TDC endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. Cover photo credit: (top left) Screenshot from drone video footage of diverging diamond/ roundabout interchange at US-50 and SR-291S in Leeâs Summit, Missouri (Missouri Department of Transportation 2018c). (top right) Screenshot of public outreach video for continuous flow intersections, location at Redwood Road and West 6200 South in Taylorsville, Utah, video produced by the North Carolina Department of Transporta- tion (North Carolina Department of Transportation 2018b). (bottom left) Aerial view of quadrant roadway intersection at US-21 and SR-73 in Huntersville, North Carolina (Imagery Â©2019 Google, Imagery Â©2019 Maxar Technologies, Orbis Inc, U.S. Geological Survey, Map data Â©2019 Google). (bottom right) Screenshot from time-lapse video for superstreet at US-41 and SR-114 in Morocco, Indiana (Indiana Department of Trans- portation 2017). NOTICE The report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the National Academies of Sciences, Engineering, and Medicine. The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; the FHWA; or the program sponsors. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturersâ names appear herein solely because they are considered essential to the object of the report. NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed, and implementable research is the most effective way to solve many problems facing state departments of transportation (DOTs) administrators and engineers. Often, highway problems are of local or regional interest and can best be studied by state DOTs individually or in cooperation with their state universities and others. However, the accelerating growth of highway transporta- tion results in increasingly complex problems of wide interest to high- way authorities. These problems are best studied through a coordinated program of cooperative research. Recognizing this need, the leadership of the American Association of State Highway and Transportation Officials (AASHTO) in 1962 ini- tiated an objective national highway research program using modern scientific techniquesâthe National Cooperative Highway Research Program (NCHRP). NCHRP is supported on a continuing basis by funds from participating member states of AASHTO and receives the full cooperation and support of the Federal Highway Administration (FHWA), United States Department of Transportation, under Agree- ment No. 693JJ31950003. The Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine was requested by AASHTO to administer the research program because of TRBâs recognized objectivity and understanding of modern research practices. TRB is uniquely suited for this purpose for many reasons: TRB maintains an extensive com- mittee structure from which authorities on any highway transportation subject may be drawn; TRB possesses avenues of communications and cooperation with federal, state, and local governmental agencies, univer- sities, and industry; TRBâs relationship to the National Academies is an insurance of objectivity; and TRB maintains a full-time staff of special- ists in highway transportation matters to bring the findings of research directly to those in a position to use them. The program is developed on the basis of research needs iden- tified by chief administrators and other staff of the highway and transportation departments, by committees of AASHTO, and by the FHWA. Topics of the highest merit are selected by the AASHTO Special Committee on Research and Innovation (R&I), and each year R&Iâs recommendations are proposed to the AASHTO Board of Direc- tors and the National Academies. Research projects to address these topics are defined by NCHRP, and qualified research agencies are selected from submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Academies and TRB. The needs for highway research are many, and NCHRP can make significant contributions to solving 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.
The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, non- governmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president. The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. John L. Anderson is president. The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president. The three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. The National Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine. Learn more about the National Academies of Sciences, Engineering, and Medicine at www.national-academies.org. The Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to provide leadership in transportation improvements and innovation through trusted, timely, impartial, and evidence-based information exchange, research, and advice regarding all modes of transportation. The Boardâs varied activities annually engage about 8,000 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. Learn more about the Transportation Research Board at www.TRB.org.
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 CRP STAFF FOR NCHRP SYNTHESIS 550 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Jo Allen Gause, Senior Program Officer Deborah Irvin, Program Coordinator Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications NCHRP PROJECT 20-05 PANEL Joyce N. Taylor, Maine DOT, Augusta, ME (Chair) Socorro âCocoâ Briseno, California DOT (Retired), Sacramento, CA Anita Bush, Nevada DOT, Carson City, NV Joseph D. Crabtree, University of Kentucky, Lexington, KY Mostafa âMoeâ Jamshidi, Nebraska DOT, Lincoln, NE Cynthia L. Jones, Ohio DOT, Columbus, OH Jessie X. Jones, Arkansas DOT, Little Rock, AR Brenda Moore, North Carolina DOT, Raleigh, NC Ben Orsbon, South Dakota DOT, Pierre, SD Randall R. âRandyâ Park, Avenue Consultants, Bluffdale, UT Brian Worrel, Iowa DOT, Ames, IA Jack Jernigan, FHWA Liaison Jim McDonnell, AASHTO Liaison Stephen F. Maher, TRB Liaison TOPIC 50-11 PANEL Christina D. Barry, Georgia DOT, White, GA Bradford P. Foley, Maine DOT, Augusta, ME Federico J. Gontaruk, Virginia DOT, Richmond, VA John M. Mason, Pennsylvania State University - Harrisburg, Middletown, PA Kenneth L. Mora, Texas DOT, Austin, TX Brad L. Steckler, Indiana DOT, Indianapolis, IN Mike R. Wahlstedt, TranSystems, Kansas City, MO Mark Doctor, FHWA Liaison Richard A. Cunard, TRB Liaison
ABOUT THE NCHRP SYNTHESIS PROGRAM Highway administrators, engineers, and researchers often face problems for which information already exists, either in documented form or as undocumented experience and practice. This infor- mation may be fragmented, scattered, and unevaluated. As a consequence, full knowledge of what has been learned about a problem may not be brought to bear on its solution. Costly research findings may go unused, valuable experience may be overlooked, and due consideration may not be given to recommended practices for solving or alleviating the problem. There is information on nearly every subject of concern to highway administrators and engineers. Much of it derives from research or from the work of practitioners faced with problems in their day- to-day work. To provide a systematic means for assembling and evalu ating such useful information and to make it available to the entire highway community, the American Association of State High- way and Transportation Officialsâthrough the mechanism of the National Cooperative Highway Research Programâauthorized the Transportation Research Board to undertake a continuing study. This study, NCHRP Project 20-05, âSynthesis of Information Related to Highway Problems,â searches out and synthesizes useful knowledge from all available sources and prepares concise, documented reports on specific topics. Reports from this endeavor constitute an NCHRP report series, Synthesis of Highway Practice. This synthesis series reports on current knowledge and practice, in a compact format, without the detailed directions usually found in handbooks or design manuals. Each report in the series provides a compendium of the best knowledge available on those measures found to be the most successful in resolving specific problems. FOREWORD By Jo Allen Gause Staff Officer Transportation Research Board As traffic demand increases, the use of alternative intersections, such as roundabouts, diverging diamond interchanges, J-turns, median U-turns, and continuous flow intersections, is becoming more prevalent within the United States. An alternative intersection is an intersection where traffic movement is re-routed from a traditional intersection form to remove major conflict points. This synthesis report documents the evaluation and selection processes within state departments of trans- portation for intersection projects. Information for this study was gathered through a literature review, a survey of state departments of transportation, and follow-up interviews with selected agencies. Six case examples provide addi- tional information on alternative intersection design and selection practices. Henry Brown, Praveen Edara, and Grace Hartman, University of Missouri in Columbia, and Gil Chlewicki, Advanced Transportation Solutions, collected and synthesized the information and wrote the report. The members of the topic panel are acknowledged on page iv. The synthesis is an imme- diately useful document that records practices that were acceptable within the limitations of the knowledge available at the time of its preparation. As progress in research and practice continues, new knowledge will be added to that now at hand.
1 Summary 5 Chapter 1 Introduction 5 Background 5 Objectives and Scope 6 Definitions 6 Types of Alternative Intersections 11 Synthesis Methodology 11 Synthesis Organization 12 Chapter 2 Literature Review 12 Guidance for Alternative Intersections 17 Intersection Control Evaluation Policies 21 Screening and Analysis Tools 23 Operational and Safety Evaluations 30 Considerations for Bicyclists and Pedestrians 33 Constructability 34 Public Perception 35 Chapter 3 Survey Results 35 Experience with Alternative Intersections 42 Considerations for Alternative Intersections 43 Evaluations of Alternative Intersections 44 Policies and Guidance for Alternative Intersections 44 Practices for Alternative Intersections 48 Public Outreach for Alternative Intersections 49 Other Survey Feedback 49 Summary of Key Survey Findings 51 Chapter 4 Case Examples 53 Alabama 55 Georgia 58 Indiana 61 Minnesota 63 Missouri 65 Texas 67 Case Examples Summarized 68 Chapter 5 Conclusions 68 Synthesis Objectives, Scope, and Methodology 68 Summary of Key Findings 70 Suggestions for Future Study C O N T E N T S
72 List of Abbreviations 73 References 82 Appendix A Survey Questionnaire 99 Appendix B List of Responding Agencies 101 Appendix C Individual Survey Responses 177 Appendix D Design Guidance and Standards for Departments of Transportation (DOTs) 182 Appendix E Example Flowcharts and Tables from Intersection Control Evaluation (ICE) Policies 197 Appendix F Screening and Analysis Tools for Alternative Intersections 199 Appendix G Summary of Operational Studies for Alternative Intersections 204 Appendix H Summary of Safety Evaluations of Alternative Intersections Note: Photographs, figures, and tables in this report may have been converted from color to grayscale for printing. The electronic version of the report (posted on the web at www.trb.org) retains the color versions.