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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 REPORT 780 Design Guidance For Intersection Auxiliary Lanes Kay Fitzpatrick Texas a&M TransporTaTion insTiTuTe College Station, TX Marcus A. Brewer Texas a&M TransporTaTion insTiTuTe College Station, TX Paul Dorothy WhiTe sTar engineering ConsulTanTs Worthington, OH Eun Sug Park Texas a&M TransporTaTion insTiTuTe College Station, TX Subscriber Categories Design â¢ Operations and Traffic Management TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2014 www.TRB.org Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration
NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation develops increasingly complex problems of wide interest to 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 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 Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Boardâs recognized objectivity and 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 cooperation with federal, state and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed 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. 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 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet at: http://www.national-academies.org/trb/bookstore Printed in the United States of America NCHRP REPORT 780 Project 03-102 ISSN 0077-5614 ISBN 978-0-309-28432-5 Library of Congress Control Number 2014946499 Â© 2014 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, FMCSA, FTA, or Transit Development Corporation 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. NOTICE The project that is the subject of this report was a part of the National Cooperative Highway Research Program, conducted by the Transportation Research Board with the approval of the Governing Board of the National Research Council. The members of the technical panel selected to monitor this project and to review this report were chosen for their special competencies and with regard for appropriate balance. 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 Governing Board of the National Research Council. 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 Research Council, or the program sponsors. The Transportation Research Board of the National Academies, the National Research Council, 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.
The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon 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 technical 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 Academy 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 achievements of engineers. Dr. C. D. Mote, Jr., 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, upon its own initiative, to identify issues of medical care, research, and education. Dr. Victor J. Dzau 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 Academyâs purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, 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 Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. C. D. Mote, Jr., are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is one of six major divisions of the National Research Council. The mission of the Transporta- tion Research Board is to provide leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal. The Boardâs varied activities annually engage about 7,000 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 individu- als interested in the development of transportation. www.TRB.org www.national-academies.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 REPORT 780 Christopher W. Jenks, Director, Cooperative Research Programs Christopher Hedges, Manager, National Cooperative Highway Research Program B. Ray Derr, Senior Program Officer Danna Powell, Senior Program Assistant Eileen P. Delaney, Director of Publications Hilary Freer, Senior Editor NCHRP PROJECT 03-102 PANEL Field of TrafficâArea of Operations and Control Anthony D. Wyatt, North Carolina DOT, Garner, NC (Chair) Michael S. Fleming, Washington State DOT, Olympia, WA Aaron M. Frits, Kansas DOT, Topeka, KS Evangelos I. Kaisar, Florida Atlantic University, Boca Raton, FL Lawrence T. Moore, California DOT, Sacramento, CA James L. Pline, Pline Engineering, Inc., Boise, ID Lisa Schletzbaum, Massachusetts DOT, Boston, MA Jeffrey Shaw, FHWA Liaison Richard A. Cunard, TRB Liaison
F O R E W O R D AASHTOâs A Policy on Geometric Design of Highways and Streets (the Green Book) contains a limited amount of guidance for auxiliary lanes at intersections. This report expands on that guidance, particularly regarding bypass lanes, channelized right-turn lanes, deceleration and taper length, design and capacity of multiple left-turn lanes, and alterna- tive intersection designs. The report will be very useful in updating agency design manuals and to those designing intersections. A large proportion of crashes occur at intersections and auxiliary turn lanes are a key countermeasure for addressing such crashes. Auxiliary lanes can also be used to increase capacity and improve operations at an intersection. The design components of a traditional auxiliary turn lane consist of the length needed to store an appropriate number of waiting vehicles, a vehicle deceleration area, and the taper needed to develop the full lane width. Offset and indirect turn lanes and other types of auxiliary lanes (e.g., acceleration lanes) have similar components. The guidance and practice used throughout the United States for auxiliary lane designs and application vary by intersection location (e.g., rural or urban), traffic control (e.g., stop-control or signal-control), and lane type (e.g., right- or left-turn). The AASHTO Green Book contains limited criteria for geometric design of auxiliary lanes at intersections. Additional support for these criteria and expansion of the material to cover additional designs are needed to fully realize the safety and operational benefits of auxiliary lanes at intersections. In NCHRP Project 03-102, the Texas A&M Transportation Institute reviewed existing literature and ongoing research projects and identified issues meriting further study to vali- date, enhance, and expand current Green Book guidance. Field studies were conducted to assess the operation of double left-turn lanes and deceleration lanes. The research team then developed practical guidance for designers on auxiliary lanes, including recommendations for improving the Green Book. By B. Ray Derr Staff Officer Transportation Research Board
AUTHOR ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 03-102 by the Texas A&M Trans- portation Institute (TTI) and Paul Dorothy of White Star Engineering Consultants. The Texas A&M Research Foundation was the contractor for this study. Kay Fitzpatrick, TTI senior research engineer, was the principal investigator. The other authors of this report are Marcus A. Brewer (associate research engineer, TTI), Paul Dorothy (principal, White Star Engineering Consultants), and Eun Sug Park (research scientist, TTI). The work was performed under the general supervision of Dr. Fitzpatrick. The authors wish to acknowledge the many individuals who contributed to this research by participat- ing in the state-of-the-practice questionnaire, assisting with the review of literature and reference manu- als, helping with field data collection and reduction, and assisting with other project-related tasks. Those individuals include (but are not limited to) â¢ Robert Medland, vice president/senior project manager, Traffic Research and Analysis, Inc. â¢ Lisa Walters, administrative assistant, Traffic Research and Analysis, Inc. â¢ Joseph Kaluha, senior field supervisor, Traffic Research and Analysis, Inc. â¢ Mark W. Litzmann, project manager, transportation, CMB Smith. â¢ P.K. Okyere, project manager, transportation, CMB Smith. â¢ State-of-the-practice questionnaire respondents (whose individual names cannot be listed here). â¢ Amanda Martin, student worker TTI. â¢ Blanca Garcia, student worker, TTI. â¢ Carla Beltran, student worker, TTI. â¢ Colleen Dau, lead office assistant, TTI. â¢ Christopher White, student worker, TTI. â¢ Dan Walker, assistant research specialist, TTI. â¢ Hailey Minter, student worker, TTI. â¢ James Robertson, graduate student, Texas A&M University. â¢ Kayla Ryan, student worker, TTI. â¢ Mehdi Azimi, graduate student, Texas A&M University. â¢ Noopur Shah, student worker, TTI. â¢ Pei-fen Kuo, graduate student, Texas A&M University. â¢ Ross Langdale, student worker, TTI. â¢ Sarah Motes, student worker, TTI. â¢ Seth Cole, student worker, TTI. â¢ Shelby Buenger, student worker, TTI.
C O N T E N T S 1 Summary 5 Chapter 1 Background 5 Research Problem Statement 5 Research Objectives 5 Research Approach 5 Report Organization 7 Chapter 2 Review of Literature and State Design Guidance 7 Literature 21 Offset Left-Turn Lanes 29 Design Tools 29 Ongoing and Recently Completed Research 30 Review of Online Design Manuals 32 Chapter 3 State of the Practice 32 Introduction 33 Questionnaire Responses 44 Chapter 4 Typical Designs 44 Introduction 44 Case Studies 58 Chapter 5 Double Left-Turn Lane Field Study 58 Background 58 Study Selection 58 Literature 61 Objective and Measures of Effectiveness 61 Study Matrix 61 Study Sites 63 Data Collection 64 Data Reduction 69 Analysis/Results 77 Chapter 6 Deceleration Field Study 77 Background 77 Objective and Measures of Effectiveness 78 Literature 82 Study Matrix 83 Study Sites 84 Data Collection 87 Data Reduction 89 Quality Control 89 Analysis 99 Suggested Changes to Green Book
101 Chapter 7 Conclusions, Recommendations, and Suggested Research 101 Project Summary 103 Conclusions 108 Recommendations 109 Suggested Research 112 Appendix A Recommended Revisions to AASHTO Green Book 145 References Note: Many of the photographs, figures, and tables in this report 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.