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Rural Speed Safety Project RURAL SPEED SAFETY PROJECT April 2020 Submitted by Subasish Das, Srinivas Geedipally, Raul Avelar, Lingtao Wu, Kay Fitzpatrick, Mohamadreza Banihashemi, and Dominique Lord Texas A&M Transportation Institute 400 Harvey Mitchell Parkway South, Suite 300 College Station, TX 77845-4375 Notice This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to the objective of the document. Technical Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. 4. Title and Subtitle 5. Report Date Rural Speed Safety Project for USDOT Safety Data Initiative April 2020 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. Subasish Das, Srinivas Geedipally, Raul Avelar, Lingtao Wu, Kay Fitzpatrick, Mohamadreza Banihashemi, Dominique Lord 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Texas A&M Transportation Institute 11. Contract or Grant No. The Texas A&M University System DTFH6116D00039L College Station, Texas 77843-3135 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Office of the Secretary of Transportation Final Report Office of the Assistance Secretary of Transportation for Policy 14. Sponsoring Agency Code 6300 Georgetown Pike McLean, VA 22101 15. Supplementary Notes Projects were performed with the cooperation and participation of the Federal Highway Administration Project Title: Rural Speed Safety Project, for USDOT Safety Data Initiative 16. Abstract The objective of this project was to examine prevailing operating speeds on a large scale to determine how speed and speed differentials interact with roadway characteristics to influence the likelihood of crashes. The project team conducted three major tasks: (a) developed conflated databases for Ohio and Washington by incorporating the Highway Safety Information System (HSIS) and the National Performance Management Research Data Set; (b) developed static and interactive data visualization tools to show the association between operating speed measures and safety outcomes; and (c) developed best-fit models at annual and daily levels to address the impact of operating speed on safety. The overall finding was that speed-related operational information is an area of opportunity to better understand safety outcomes. This pilot project established the framework of data conflation and an analytical pipeline that will help to address the effect of operation speed measures on safety. The replicability procedure developed in this study can be applied to other HSIS States. The project team developed a weblink that includes descriptive statistics and data visualization tools (both static and interactive). The links provide a more detailed view of the speed measures and descriptive statistics, as well as visualization of the association between speed measures and crashes at a granular level. The team members also developed an interactive decision support tool (https://ruralspeedsafety.shinyapps.io/rss_sdi/) to show annual risk scoring using Washington and Ohio data that contain expected total crashes from the developed models. 17. Key Words 18. Distribution Statement Rural roadways; traffic crashes; operating speed; roadway No restrictions. This document is available to the public through characteristics; safety performance functions. the National Technical Information Service Alexandria, Virginia 22312 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price Unclassified Unclassified 122 Form DOT F 1700.7 (8-72) Reproduction of completed page authorized ii iii TABLE OF CONTENTS EXECUTIVE SUMMARY .......................................................................................................... 1 Research Problem ....................................................................................................................... 1 Overview of Methodology .......................................................................................................... 1 General Findings ......................................................................................................................... 2 Decision Support Tool ................................................................................................................ 5 Opportunities and Lessons Learned ............................................................................................ 6 Limitations .................................................................................................................................. 7 NPMRDS and HSIS ............................................................................................................ 7 Zero inflation in crash counts ............................................................................................. 7 Model development and refinement ................................................................................... 7 CHAPTER 1. INTRODUCTION ................................................................................................ 9 Project Goals and Objectives ...................................................................................................... 9 Dataset Structures ..................................................................................................................... 10 Data Structure 1 ................................................................................................................ 10 Data Structure 2 ................................................................................................................ 11 Data Structure 3 ................................................................................................................ 11 CHAPTER 2. DATA INTEGRATION ..................................................................................... 13 Introduction ............................................................................................................................... 13 Data Description ....................................................................................................................... 13 Data Coverage Using NPMRDS 2015Q4 ......................................................................... 15 Conflated Data .................................................................................................................. 16 CHAPTER 3. STATISTICAL MODELS ................................................................................. 19 Studies on Speed-Crash Relationship ....................................................................................... 19 Annual-Level Crash Analysis ................................................................................................... 21 Exploratory Data Analysis ................................................................................................ 22 Correlation Analysis ......................................................................................................... 30 Safety Performance Functions by Facility Types ............................................................. 31 Model Validation .............................................................................................................. 40 Daily-Level Crash Prediction Analysis .................................................................................... 42 Functional Form of Tweedie Distribution ........................................................................ 43 Exploratory Examination of Time Before and After Crashes .................................................. 49 Functional Form of Mixed-Effects Model ........................................................................ 50 Model Development .......................................................................................................... 52 CHAPTER 4. DECISION SUPPORT TOOL .......................................................................... 57 Interactive Decision Support Tool ............................................................................................ 57 Feasibility of Applying Real-Time NPMRDS Data ......................................................... 60 Interactive Data Visualization Tool .......................................................................................... 60 Example (Interactive GIS Maps) ...................................................................................... 61 Example (Dygraphs) ......................................................................................................... 62 CHAPTER 5. CONCLUSIONS ................................................................................................. 65 Findings from Annual-Level Crash Prediction Modeling ........................................................ 65 Findings from Daily-Level Crash Prediction Modeling ........................................................... 66 iv Findings from Exploratory Examination of Time Before and After Crashes ........................... 66 Decision Support Tool .............................................................................................................. 67 REFERENCES ...........................................................................................................................
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