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TRANSPORTATION RESEARCH BOARD WASHINGTON, D.C. 2014 www.TRB.org The Second S T R A T E G I C H I G H W A Y R E S E A R C H P R O G R A M REPORT S2-L08-RW-1 Incorporating Travel Time Reliability into the Highway Capacity Manual John Zegeer, James Bonneson, richard dowling, Paul ryus, mark Vandehey, and wayne kittelson Kittelson & Associates, Inc. nagui rouPhail, Bastian schroeder, ali haJBaBaie, BehZad aghdashi, thomas chase, and soheil saJJadi North Carolina State UniversityâInstitute for Transportation Research and Education richard margiotta Cambridge Systematics, Inc. lily elefteriadou Independent Consultant
Subject Areas Highways Operations and Traffic Management Planning and Forecasting
SHRP 2 Reports Available by subscription and through the TRB online bookstore: www.TRB.org/bookstore Contact the TRB Business Office: 202-334-3213 More information about SHRP 2: www.TRB.org/SHRP2 SHRP 2 Report S2-L08-RW-1 ISBN: 978-0-309-27351-0 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 copy- right to any previously published or copyrighted material used herein. The second Strategic Highway Research Program grants permission to repro- duce 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, or FHWA endorsement of a particular prod- uct, method, or practice. It is expected that those reproducing material in this document for educational and not-for-profit purposes will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from SHRP 2. Note: SHRP 2 report numbers convey the program, focus area, project number, and publication format. Report numbers ending in âwâ are published as web documents only. Notice The project that is the subject of this report was a part of the second Strategic 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 committee selected to monitor this project and review this report were chosen for their special competencies and with regard for appropriate balance. The report was reviewed by the technical committee 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 second Strategic 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 Second Strategic Highway Research Program Americaâs highway system is critical to meeting the mobility and economic needs of local communities, regions, and the nation. Developments in research and technologyâsuch as advanced materials, communications technology, new data collection tech- nologies, and human factors scienceâoffer a new opportunity to improve the safety and reliability of this important national resource. Breakthrough resolution of significant transportation problems, however, requires concentrated resources over a short time frame. Reflecting this need, the second Strategic Highway Research Program (SHRP 2) has an intense, large-scale focus, integrates multiple fields of research and technology, and is fundamentally different from the broad, mission-oriented, discipline-based research programs that have been the mainstay of the highway research industry for half a century. The need for SHRP 2 was identified in TRB Special Report 260: Strategic Highway Research: Saving Lives, Reducing Congestion, Improving Quality of Life, published in 2001 and based on a study sponsored by Congress through the Transportation Equity Act for the 21st Century (TEA-21). SHRP 2, modeled after the first Strategic Highway Research Program, is a focused, time- constrained, management-driven program designed to com- plement existing highway research programs. SHRP 2 focuses on applied research in four areas: Safety, to prevent or reduce the severity of highway crashes by understanding driver behavior; Renewal, to address the aging infrastructure through rapid design and construction methods that cause minimal disruptions and produce lasting facilities; Reliability, to reduce congestion through incident reduction, management, response, and mitigation; and Capacity, to integrate mobility, economic, environmental, and community needs in the planning and designing of new trans- portation capacity. SHRP 2 was authorized in August 2005 as part of the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU). The program is managed by the Transportation Research Board (TRB) on behalf of the National Research Council (NRC). SHRP 2 is conducted under a memo- randum of understanding among the American Association of State Highway and Transportation Officials (AASHTO), the Federal Highway Administration (FHWA), and the National Academy of Sciences, parent organization of TRB and NRC. The program provides for competitive, merit-based selection of research contractors; independent research project oversight; and dissemination of research results.
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. On the authority of the charter granted to it by 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 achieve- ments of engineers. Dr. C. D. (Dan) 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, on 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. (Dan) 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 Transportation Research Board is to provide leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisci- plinary, 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 Transporta- tion, and other organizations and individuals interested in the development of transportation. www.TRB.org www.national-academies.org
ACKNOWLEDGMENTS This work was sponsored by the Federal Highway Administration in cooperation with the American Asso- ciation of State Highway and Transportation Officials. It was conducted in the second Strategic Highway Research Program (SHRP 2), which is administered by the Transportation Research Board of the National Academies. The project was managed by William Hyman, Senior Program Officer for SHRP 2 Reliability. Kittelson & Associates, Inc., was the primary contractor for the project and was supported by the follow- ing subcontractors: the Institute for Transportation Research and Education (ITRE) at North Carolina State University, Cambridge Systematics, Inc., the Texas A&M Research Foundation, and Write Rhetoric. Mark Vandehey and Wayne Kittelson with Kittelson & Associates, Inc., served as principal investigators for this project. The other authors are Paul Ryus, Richard Dowling, James Bonneson, and John Zegeer of Kittelson & Associates, Inc.; Nagui Rouphail, Bastian Schroeder, Ali Hajbabaie, Behzad Aghdashi, Thomas Chase, and Soheil Sajjadi of ITRE; Richard Margiotta of Cambridge Systematics, Inc.; and Lily Elefteriadou, independent consultant. SHRP 2 STAFF Ann M. Brach, Director Stephen J. Andrle, Deputy Director Neil J. Pedersen, Deputy Director, Implementation and Communications Cynthia Allen, Editor Kenneth Campbell, Chief Program Officer, Safety JoAnn Coleman, Senior Program Assistant, Capacity and Reliability Eduardo Cusicanqui, Financial Officer Richard Deering, Special Consultant, Safety Data Phase 1 Planning Shantia Douglas, Senior Financial Assistant Charles Fay, Senior Program Officer, Safety Carol Ford, Senior Program Assistant, Renewal and Safety Jo Allen Gause, Senior Program Officer, Capacity James Hedlund, Special Consultant, Safety Coordination Alyssa Hernandez, Reports Coordinator Ralph Hessian, Special Consultant, Capacity and Reliability Andy Horosko, Special Consultant, Safety Field Data Collection William Hyman, Senior Program Officer, Reliability Linda Mason, Communications Officer Reena Mathews, Senior Program Officer, Capacity and Reliability Matthew Miller, Program Officer, Capacity and Reliability Michael Miller, Senior Program Assistant, Capacity and Reliability David Plazak, Senior Program Officer, Capacity and Reliability Rachel Taylor, Senior Editorial Assistant Dean Trackman, Managing Editor Connie Woldu, Administrative Coordinator
F O R EWO R D William Hyman, SHRP 2 Senior Program Officer, Reliability The scope of work for SHRP 2 Reliability Project L08, Incorporating Travel Time Reliability into the Highway Capacity Manual, called for developing methods that could potentially address travel time reliability in the analytic procedures for freeway facilities and urban streets in the Highway Capacity Manual (HCM). This research resulted in two chapters that the TRB Committee on Capacity and Quality of Service has approved for inclusion in the HCM. The first is Chapter 36, concerning freeway facilities and urban streets, and the second is a supplemental Chapter 37, which provides more detail on the methodologies. Corresponding to the methodologies for incorporating reliability into the Highway Capacity Manual for freeway facilities and urban streets are new computational engines developed in conjunction with the 2010 HCM that work with FREEVAL and STREETVAL. After this project was completed, the SHRP 2 Reliability Program conducted four pilots in the states of California, Florida, Minnesota, and Washington, in part to test the new com- putational software for addressing reliability. Recommendations for improving the software were compiled and selected enhancements were made, generally to make the software more user friendly. While SHRP 2 finished the enhancements, further work on improving the reliability high- way capacity analysis products has occurred under National Cooperative Highway Research Program (NCHRP) Project 03-115, Production of a Major Update to the Highway Capacity Manual. Those interested in the treatment of reliability in highway capacity analysis should examine this NCHRP work when it is completed. Interested individuals should also moni- tor the decisions of the TRB Committee on Highway Capacity and Quality of Service for approved updates to the manual. The Highway Capacity Manual is one of the most widely consulted technical references in the transportation field. The work performed under SHRP 2 Reliability Project L08 is likely to allow decision makers, practitioners, and researchers to better understand the impli- cations of nonrecurring congestion factors, such as incidents, weather, and work zones, for the capacity analysis, assessment of level of service, and performance evaluation of freeway facilities and urban streets.
C O N T E N T S 1 Executive Summary 1 Definition for Travel Time Reliability 2 Reliability Metrics (for Use as Performance Measures) 4 Methodology for Calculating Reliability 6 Development of Scenario Generators 7 Enhancements to the HCM Base Methodologies 8 Corridor Applications 9 Potential Methods for Defining Level of Service by Using Reliability as a Service Measure 10 Future Research Needs 12 CHAPTER 1 Introduction 12 Research Problem Statement 12 Project Objectives 13 Project Tasks 14 CHAPTER 2 Defining and Measuring Reliability 14 Definitions for Reliability 15 Terminology 15 Reliability Metrics 18 CHAPTER 3 State of the Art and State of the Practice 18 Domestic and International Agency Usage 19 International Research 20 U.S. Research 24 CHAPTER 4 Development of Freeway and Urban Streets Methodologies 24 Overview of the L08 Conceptual Analysis Framework 25 Introduction to the Freeway Facilities Methodology 26 Components of the Freeway Facilities Methodology 31 Introduction to the Urban Streets Methodology 37 CHAPTER 5 Scenario Generator Development 37 Introduction to Freeway Scenario Development 38 Concept and Generation of Base Freeway Scenarios 44 Study Period for Freeway Scenario Generation 58 Detailed Freeway Scenario Generation 60 Freeway Scenario Generation Input for FREEVAL-RL 63 Freeway Summary and Conclusions 63 Urban Street Scenario Development
80 CHAPTER 6 Model Enhancements 80 Freeway Facilities Introduction 81 Description of Freeway Facility Enhancements 89 FREEVAL-RL Calibration 93 Summary of Freeway Model Enhancements 93 Urban Streets Enhancements 107 CHAPTER 7 Corridor Applications 107 Corridor Definition 107 Methodological Considerations 108 Potential Applications of Corridor Reliability Analysis 111 CHAPTER 8 Recommendations 111 Defining Reliability Levels of Service 115 Implementing the L08 Research 116 Identifying Freeway Facility Research Needs 117 Identifying Urban Streets Research Needs 120 References 122 Appendix A. FREEVAL Userâs Guide 142 Appendix B. STREETVAL Userâs Guide 169 Appendix C. Recurring Demand for Freeway Scenario Generator 175 Appendix D. Weather- and Incident-Related Crash Frequencies 193 Appendix E. Weather-Modeling Alternatives and Validation for the Freeway and Urban Street Scenario Generators 205 Appendix F. Incident Probabilities Estimation for Freeway Scenario Generator 216 Appendix G. Freeway Free-Flow Speed Adjustments for Weather, Incidents, and Work Zones 225 Appendix H. Default Factors for the Urban Streets Reliability Methodology 233 Appendix I. Example Problem: Existing Freeway Reliability 248 Appendix J. HCM Urban Streets Methodology Enhancements: Saturation Flow Rate Adjustment Factor for Work Zone Presence