Crash Modification Factors in the Highway Safety Manual: Resources for Evaluation (2023)

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NCHRP Web-Only Document 352 Crash Modification Factors in the Highway Safety Manual Resources for Evaluation Raghavan Srinivasan James Bonneson Taha Saleem Kittelson & Associates University of North Carolina Portland, OR Highway Safety Research Center Chapel Hill, NC Bhagwant Persaud Toronto, ON Frank Gross Thanh Le Craig Lyon Scott Himes Ottowa, ON R. J. Porter Vanasse Hangen Brustlin, Inc. Raleigh, NC Appendices for NCHRP Project 17-72 Submitted June 2022 © 2023 by the National Academy of Sciences. National Academies of Sciences, Engineering, and Medicine and the graphical logo are trademarks of the National Academy of Sciences. All rights reserved. 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 transportation results in increasingly complex problems of wide interest to highway 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 initiated an objective national highway research program using modern scientific techniques—the 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 Agreement No. 693JJ31950003. 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. DISCLAIMER The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research. They 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 does not develop, issue, or publish standards or specifications. The Transportation Research Board manages applied research projects which provide the scientific foundation that may be used by Transportation Research Board sponsors, industry associations, or other organizations as the basis for revised practices, procedures, or specifications. The Transportation Research Board, the National Academies, and the sponsors of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the object of the report. The information contained in this document was taken directly from the submission of the author(s). This material has not been edited by TRB. 

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COOPERATI VE RESEAR CH PROGRAMS CRP STAFF FOR NCHRP WEB-ONLY DOCUMENT 352 Christopher J. Hedges, Director, Cooperative Research Programs Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program Zuxuan Deng, Senior Program Officer Anthony P. Avery, Senior Program Assistant Natalie Barnes, Director of Publications Heather DiAngelis, Associate Director of Publications Jennifer Correro, Assistant Editor NCHRP PROJECT 17-72 PANEL Field of Traffic—Area of Safety Girish N. Modi, Pennsylvania Department of Transportation, Harrisburg, PA (Chair) Sean P. Coyle, Peoria, IL Michael D. Fontaine, Virginia Transportation Research Council, Charlottesville, VA Shauna L. Hallmark, Iowa State University, Ames, IA Cheryl Bornheimer Kelley, Burns & McDonnell, Kansas City, MO Kimberly Kolody Silverman, Jacobs, Chicago, IL Grant G. Schultz, Brigham Young University, Provo, UT Hadi H. Shirazi, Louisiana Department of Transportation and Development, Baton Rouge, LA Karen Scurry, FHWA Liaison Kelly K. Hardy, AASHTO Liaison Bernardo B. Kleiner, TRB Liaison 

CONTENTS Appendix A Review of Procedures for Assessing CMF Quality ...................................................... A-1 Appendix A.1 Estimating Safety Effect of Using Results from Multiple Studies .................. A-36 Appendix B CMF User Preferences and Practices ........................................................................... B-1 Appendix C CMF Rating System for the 2nd Edition of the HSM ................................................. C-1 Appendix D CMF Rating Summary for the 2nd Edition of the HSM ............................................ D-1 Appendix E Development of Crash Modification Functions for Improving Curve Delineation .. E-1 Appendix F Development of Crash Modification Functions for Shoulder and Median Width .....F-1 Appendix G Development of Crash Modification Functions for Adding a TWLTL to a Two-Lane Road ................................................................................................................................ G-1 Appendix H Development of Crash Modification Functions for Conversion of Two-Way Stop-Controlled to All-Way Stop-Controlled at Four-Leg Intersections .................................... H-1 Appendix I SPF Adjustment Factors for Segment SPFs from NCHRP Project 17-62 ....................I-1 Appendix J SPF Adjustment Factors for Intersection SPFs from NCHRP Project 17-62 ............ J-1 Appendix K Calibration of Prediction Models of Rural Segments for the 2nd Edition of the HSM ................................................................................................................... K-1 Appendix L Calibration of Prediction Models of Urban Segments for the 2nd Edition of the HSM ................................................................................................................... L-1 Appendix M Calibration of Prediction Models of Rural and Urban Intersections for the 2nd Edition of the HSM .................................................................................................................. M-1 Appendix N Development of a Roadside Design CMF for Rural Two-Lane Two-Way Roads .... N-1 Appendix O HSM Implementation of a Proposed Roadside Design for Rural Two-Lane Two-Way Roads ............................................................................................................................... O-1 Appendix P CMF Gap Analysis...........................................................................................................P-1 NCHRP Web-Only Document 352 contains the appendices for NCHRP Research Report 1029: Crash Modification Factors in the Highway Safety Manual: A Review. Readers can read or purchase NCHRP Research Report 1029 on the National Academies Press website (nap.nationalacademies.org). iv