Macro-Level Analysis of Safety Planning and Crash Prediction Models: A Guide (2023)

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NCHRP Web-Only Document 348 Macro-Level Analysis of Safety Planning and Crash Prediction Models A Guide R.J. Porter Ian Hamilton Vikash Gayah Kara Peach Thanh Le VHB Raleigh, NC Bhagwant Persaud Craig Lyon Persaud & Lyon, Inc. Ottawa, ON Alireza Hadayeghi Soroush Salek CIMA+ Burlington, ON Guide for NCHRP Project 17-81 Submitted November 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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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 WEB-ONLY DOCUMENT 348 Christopher J. Hedges, Director, Cooperative Research Programs Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program Christopher T. McKenney, Senior Program Officer Sheila A. Moore, Program Associate Natalie Barnes, Director of Publications Heather DiAngelis, Associate Director of Publications Jennifer Correro, Assistant Editor NCHRP PROJECT 17-81 PANEL Field of Traffic—Area of Safety Timothy E. Barnett, University of Alabama, Troy, AL (Chair) Jeannie Yarborough Bland, Illinois Department of Transportation, Paris, IL Deo Chimba, Tennessee State University, Nashville, TN Michael J. Dugas, Greenman-Pedersen, Inc. (GPI), Bedford, NH Gordon R. Lovegrove, University of British Columbia, Kelowna, BC Christi McDaniel-Wilson, Oregon Department of Transportation, Salem, OR Luciano Rabito, Howard/Stein-Hudson Associates, Inc., Boston, MA Josh Sender, Adams County, Colorado, Brighton, CO Elizabeth Ann Wemple, HDR, Portland, OR Esther Strawder, FHWA Liaison Kelly K. Hardy, AASHTO Liaison Bernardo B. Kleiner, TRB Liaison

iv Table of Contents 1 Introduction .............................................................................................................................................. 1 Purpose and Background .......................................................................................................................... 1 2 Data Requirements .................................................................................................................................. 2 2.1 Data Inputs .......................................................................................................................................... 2 2.1.1 SAZ Development ....................................................................................................................... 2 2.1.2 Data Requirements ...................................................................................................................... 3 2.2 Data Assignment ................................................................................................................................ 4 Road Final Model.py ............................................................................................................................ 7 Step 1_Boundary Crash Process.py ...................................................................................................... 7 Step 2_Boundary Crash Random Assign.py ........................................................................................ 7 Step 3_NonBoundary Crash Process.py ............................................................................................... 7 Step 4_Final Merge.py ......................................................................................................................... 7 3 Macro-Level Planning Crash Prediction Models .................................................................................. 7 3.1 Macro-Level CPMs for Census Block Groups ................................................................................... 7 3.1.1 MPO CPMs ................................................................................................................................. 8 3.1.2 State CPMs ................................................................................................................................ 10 3.2 Estimates Provided ........................................................................................................................... 11 3.3 CPM Calibration ............................................................................................................................... 11 4 Using the Tool ......................................................................................................................................... 13 4.1 Tool Interface Layout ....................................................................................................................... 13 4.2 Using the Tool .................................................................................................................................. 14 Select CPM Type ............................................................................................................................... 15 Select CPMs and Use of Crash Data .................................................................................................. 17 Provide Calibration Factors or Functions ........................................................................................... 18 Update User Selections ...................................................................................................................... 20 Entering Data ...................................................................................................................................... 21 View Results ...................................................................................................................................... 23 References .................................................................................................................................................. 25 NCHRP Web-Only Document 348 contains the conduct of research report for NCHRP Project 17-81 and accompanies NCHRP Research Report 1044: Development and Application of Quantitative Macro-Level Safety Prediction Models. Readers can read or purchase NCHRP Research Report 1044 on the National Academies Press website (nap.nationalacademies.org).

v List of Figures Figure 1. Single Centerline Road Data Assignment between Zones 1 and 2 in GIS .................................... 5 Figure 2. Dual Carriageway Road Data Assignment between Zones 1 and 2 in GIS................................... 5 Figure 3. Single Centerline Crash Assignment between Zones 1 and 2 in GIS ........................................... 6 Figure 4. Dual Carriageway Crash Assignment between Zones 1 and 2 in GIS .......................................... 6 Figure 5. Instructions Worksheet ................................................................................................................ 14 Figure 6. CPM Settings Interface ................................................................................................................ 16 Figure 7. CPM Selection Method ............................................................................................................... 17 Figure 8. Application of Crash Data for Macro-Level CPMs ..................................................................... 18 Figure 9. CPM Calibration .......................................................................................................................... 18 Figure 10. Application of a Custom Calibration Factor. ............................................................................. 19 Figure 11. Default Calibration and Overdispersion Parameter Values. ...................................................... 20 Figure 12. User Settings Update ................................................................................................................. 20 Figure 13. Data Entry Form (Base-MPO Worksheet) ................................................................................ 21 Figure 14. Macro-Level CPM Results (Base-MPO Worksheet) ................................................................ 24 List of Tables Table 1. Required Data Inputs for Macro-Level CPMs ................................................................................ 3 Table 2. Macro-Level CPM Coefficients for Planning Areas Inside MPO Boundaries ............................. 10 Table 3. Macro-Level CPM Coefficients for Planning Areas in a State ..................................................... 11 Table 5. MPO Variables ............................................................................................................................. 22 Table 6. State Variables .............................................................................................................................. 23