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TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2008 www.TRB.org 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 613 Subject Areas Planning and Administration Guidelines for Selection of Speed Reduction Treatments at High-Speed Intersections Brian Ray Wayne Kittelson Julia Knudsen Brandon Nevers Paul Ryus Kate Sylvester KITTELSON & ASSOCIATES, INC. Portland, OR Ingrid Potts Douglas Harwood David Gilmore Darren Torbic MIDWEST RESEARCH INSTITUTE Kansas City, MO Fred Hanscom TRANSPORTATION RESEARCH CORPORATION Markham, VA John McGill Delbert Stewart SYNECTICS, INC. St. Catharines, ON, Canada 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 613 Project 3-74 ISSN 0077-5614 ISBN: 978-0-309-09935-6 Library of Congress Control Number 2008927124 © 2008 Transportation Research Board COPYRIGHT PERMISSION 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. Such approval reflects the Governing Boardâs judgment that the program concerned is of national importance and appropriate with respect to both the purposes and resources of the National Research Council. The members of the technical committee selected to monitor this project and to review this report were chosen for recognized scholarly competence and with due consideration for the balance of disciplines appropriate to the project. The opinions and conclusions expressed or implied are those of the research agency that performed the research, and, while they have been accepted as appropriate by the technical committee, they are not necessarily those of the Transportation Research Board, the National Research Council, the American Association of State Highway and Transportation Officials, or the Federal Highway Administration, U.S. Department of Transportation. Each report is reviewed and accepted for publication by the technical committee according to procedures established and monitored by the Transportation Research Board Executive Committee and the Governing Board of the National Research Council. 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 states participating in 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 this report.
CRP STAFF FOR NCHRP REPORT 613 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Christopher J. Hedges, Senior Program Officer Eileen P. Delaney, Director of Publications Hilary Freer, Senior Editor Kami Cabral, Editor NCHRP PROJECT 3-74 PANEL Field of TrafficâArea of Operations and Control Mark C. Wilson, Florida DOT, Tallahassee, FL (Chair) Bryan K. Allery, Colorado DOT, Denver, CO Frank Corrao, III, Rhode Island DOT, Providence, RI Carlos Ibarra, Texas DOT, Atlanta, TX Steven S. Pasinski, Baker Engineering, Inc., Chicago, IL Nikiforos Stamatiadis, University of Kentucky, Lexington, KY J. Richard Young, Jr., PBS&J, Jackson, MS Joe Bared, FHWA Liaison Richard A. Cunard, TRB Liaison 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
This study evaluated the effectiveness of treatments to reduce vehicle speeds at high-speed intersections. The treatments included geometric design features as well as signage and pavement markings. In the first phase of research, potential treatments were evaluated based on their applicability, key features, speed effects, safety benefits, multimodal impacts, and maintenance issues. The most promising treatments were evaluated using field testing at 10 sites in Oregon, Washington, and Texas. The following guidelines are based on the research results and will provide highway planners and designers with an important new tool in their ongoing efforts to improve safety on our highway systems. Intersection crashes, a significant portion of total crashes nationwide, account for an average of 9,000 fatalities and 1.5 million injuries annually. Fatalities and severe injuries are more likely to occur in high-speed environments in rural and suburban areas. An recent international scanning tour focused on innovative safety practices in the planning, design, operation, and maintenance of signalized intersections. The scanning team visited several European countries and developed an implementation plan with five major recommenda- tions. One recommendation was to develop treatments that reduce speeds at the approaches to and through intersections. Under NCHRP Project 03-74, a research team led by Brian L. Ray of Kittelson & Associates, Inc., developed guidelines for selecting speed reduction treatments applicable to high-speed intersections. The first phase of the study consisted of a review of relevant literature and a survey of current practices of highway agencies across the country. The research team recommended three promising treatments for further eval- uation in the second phase of the study: rumble strips, transverse pavement markings, and dynamic warning signs. These treatments were evaluated using before-and-after field stud- ies at 10 sites in three states. Based on the results, the team developed guidelines illustrating sound practices for selecting appropriate speed-reduction treatments. These guidelines led the user through intersection pre-screening, treatment screening, and treatment implemen- tation considerations. The guidelines also include information about the effects of speed and the conditions that may contribute to undesirably high speeds at intersection approaches. A final report documenting the entire research effort is available as NCHRP Web-Only Document 124 on the TRB website at htp://trb.org/news/blurb_detail.asp? id-9101. F O R E W O R D By Christopher J. Hedges Staff Officer Transportation Research Board
Managing speeds on all roadway types is of key interest to transportation professionals. Because of potential conflicts and the risk of collisions, speed management at intersections is of special interest. Research supporting the practice of managing high-speed intersections, however, is in its infancy. The treatments, and discussion of their application, in these guidelines are based on relatively limited research results from high-speed intersection loca- tions. We benefit from the intuitiveness of supplementing intersection testing results and applying what is known and documented about roadway segments and speed management. Under NCHRP Project 3-74, Kittelson & Associates, Inc., conducted testing on three speed reduction treatments, and these guidelines provide a foundation for future research that is needed to quantify the effects of each listed treatment. Future research should test the speed reduction qualities of the various treatments in a variety of applications. Further, additional information is needed to understand the possible benefits of combining treat- ments to maximize speed reduction opportunities. In addition to quality data on speed reduction, more must be learned and documented about speedâs role in, and relationship to, intersection safety. These guidelines provide a substantial discussion about speed, the role it plays, and its impact on intersections. Roadway segments and intersections place different demands and risks on drivers. The discussion emphasizes the distinct relationship between roadway seg- ments and intersections. Engineering solutions for speed management should feature ele- ments that help drivers differentiate between the tasks needed in roadway segments versus those potentially needed at intersections. In some cases, speed reduction may not necessar- ily result in increased safety. Future studies may help professionals consider whether aiding drivers to be more alert and prepared to take needed actions at an intersection (versus along the upstream roadway segment) may be as valuable as actually reducing intersection speeds. As we collect volumes of speed reduction data for a variety of treatment types, perhaps future professionals will establish values for âspeed modification factorsâ similar to the con- cept of âaccident modification factorsâ being applied in highway safety manual initiatives. With a sufficient database of speed reduction information for a variety of treatments in numerous applications, future users of updated guidelines may enjoy the benefits of predic- tive tools to consider the tradeoffs and benefits of various speed management treatments in a wide range of high-speed intersection environments. P R E F A C E
1 Summary 3 Section 1 Introduction 3 1.1 Intended Users 3 1.2 Purpose of Guidelines 3 1.3 Scope of Guidelines 4 1.4 Report Organization 5 Section 2 Speed Considerations 5 2.1 Overview 5 2.2 Intersection/Segment Relationship 7 2.3 Designing for Appropriate Speeds 7 2.4 Factors Influenced by Speed 10 2.5 Factors that Affect Speed 12 2.6 Conditions Potentially Sensitive to Speed 14 2.7 Summary 15 Section 3 Selecting an Appropriate Treatment 15 3.1 Introduction 16 3.2 Determining the Need for a Treatment 16 3.3 Treatment Selection Process 20 3.4 Combining Treatments 21 3.5 Treatment Considerations 27 3.6 Treatment Evaluation 28 3.7 Summary 29 Section 4 Treatment Descriptions 29 4.1 Overview 30 4.2 Dynamic Warning Signs 33 4.3 Transverse Pavement Markings 36 4.4 Transverse Rumble Strips 39 4.5 Longitudinal Rumble Strips 42 4.6 Wider Longitudinal Pavement Markings 44 4.7 Roundabouts 47 4.8 Approach Curvature 49 4.9 Splitter Islands 52 4.10 Speed Tables and Plateaus 54 4.11 Reduced Lane Width 57 4.12 Visible Shoulder Treatments 58 4.13 Roadside Design Features 61 4.14 Summary 62 References C O N T E N T S
65 Appendix A Treatment Implementation Process Framework 68 Appendix B Case Studies 95 Appendix C Testing Results 98 Appendix D Supplemental References