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SHRP 2 Reliability Project L08 Proposed Chapters for Incorporating Travel Time Reliability into the Highway Capacity Manual
SHRP 2 Reliability Project L08 Proposed Chapters for Incorporating Travel Time Reliability into the Highway Capacity Manual Paul Ryus, James Bonneson, Richard Dowling, John Zegeer, Mark Vandehey, and Wayne Kittelson Kittelson & Associates, Inc. Nagui Rouphail, Bastian Schroeder, Ali Hajbabaie, Behzad Aghdashi, Thomas Chase, and Soheil Sajjadi Institute for Transportation Research and Education at North Carolina State University Richard Margiotta Cambridge Systematics TRANSPORTATION RESEARCH BOARD Washington, D.C. 2013 www.TRB.org
© 2013 National Academy of Sciences. All rights reserved. ACKNOWLEDGMENT This work was sponsored by the Federal Highway Administration in cooperation with the American Association of State Highway and Transportation Officials. It was conducted in the second Strategic Highway Research Program, which is administered by the Transportation Research Board of the National Academies. 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. The second Strategic Highway Research Program 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, or FHWA endorsement of a particular product, 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. NOTICE The project that is the subject of this document 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 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. DISCLAIMER The opinions and conclusions expressed or implied in this document are those of the researchers who performed the research. They are not necessarily those of the second Strategic Highway Research Program, the Transportation Research Board, the National Research Council, or the program sponsors. The information contained in this document was taken directly from the submission of the authors. This material has not been edited by the Transportation Research Board.
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Foreword William Hyman, SHRP 2 Senior Program Officer, Reliability This document contains two proposed chapters for the Transportation Research Boardâs Highway Capacity Manual (HCM) that introduce the concept of travel time reliability and offer new analytic methods. The chapters were prepared under SHRP 2 Project L08, Incorporation of Travel Time Reliability into the Highway Capacity Manual, but they have not been officially accepted by the Highway Capacity and Quality of Service (HCQS) Committee of the Transportation Research Board. The HCQS Committee has responsibility for approving the content of the HCM. The scope of work for SHRP 2 Reliability Project L08 called for revising the methodologies for freeway facilities and urban streets. This research has resulted in a prospective Chapter 36 for the HCM concerning freeway facilities and urban streets and a prospective supplemental Chapter 37 that elaborates on the methodologies and provides an example calculation. In addition, a report documenting the research effort was prepared. It includes the userâs guides for the computational engines for freeways and urban streets. As with all SHRP 2 research, it is standard procedure to publish the key documents that result from each research project. The National Academies have approved Chapters 36 and 37 and the final report for publication as SHRP 2 products. The HCQS Committee, responsible for approval of changes to the HCM, has begun considering this material. Proposed Chapters 36 and 37 set out methodologies for incorporating reliability into the HCM analytic procedures for freeway facilities and urban streets. The approach is to generate many freeway and urban street scenarios involving various causes of nonrecurring congestion, such as incidents, weather, and work zones, and use the scenarios as input to a computational engine to calculate travel time
over a segment. The travel times for each scenario are used to construct a distribution of travel time from which reliability performance measures can be derived. Chapter 37 supplements Chapter 36. It provides reliability values for selected U.S. facilities, offers an alternative freeway incident prediction method, elaborates on the freeway and urban street scenario generators, explains how to measure reliability in the field, and gives an example problem.