Guide for Scalable Risk Assessment Methods for Pedestrians and Bicyclists

Publication No. FHWA-SA-18-032
July 2018

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Technical Report Documentation Page

1. Report No. FHWA-SA-18-032		2. Government Accession No.	3. Recipient's Catalog No.
4. Title and Subtitle GUIDE FOR SCALABLE RISK ASSESSMENT METHODS FOR PEDESTRIANS AND BICYCLISTS			5. Report Date July 2018
			6. Performing Organization Code
7. Author(s) Shawn Turner, Ipek Sener, Michael Martin, L.D. White, Subasish Das, Robert Hampshire, Mike Colety, Kay Fitzpatrick, and Ravi Wijesundera			8. Performing Organization Report No.
9. Performing Organization Name and Address Texas A&M Transportation Institute, College Station, TX 77843-3135 University of Michigan Transportation Research Institute Kimley-Horn and Associates, Inc.			10. Work Unit No. (TRAIS)
			11. Contract or Grant No. DFTH6116D00004, TTI Task Order #2
12. Sponsoring Agency Name and Address U.S. Department of Transportation Federal Highway Administration Office of Safety 1200 New Jersey Ave SE Washington, DC 20590			13. Type of Report and Period Covered Task 4 Guide: March 2017 - July 2018
			14. Sponsoring Agency Code HOP
15. Supplementary Notes Government Task Manager: Tamara Redmon
16. Abstract This guide describes scalable risk assessment methods for pedestrians and bicyclists, wherein risk is a measure of the probability of a crash to occur given exposure to potential crash events. This guide outlines eight sequential steps to develop risk values at various desired geographic scales, and describes the scope and nature of each step, including any guiding principles. Exposure to risk is an integral element of risk, and as such, an integral element of the pedestrian and bicyclist risk assessment methods in this guide. Exposure is a measure of the number of potential opportunities for a crash to occur, and is often directly related to the number of people who walk and bike. This guide provides information on analytic methods to estimate pedestrian and bicyclist exposure, and identifies other relevant guides and resources that provide supplemental information for exposure estimation. Depending upon the desired geographic scale, one or more of these three analytic methods can be used to estimate pedestrian and bicyclist exposure: 1) site counts; 2) travel demand estimation models (several different types); and, 3) travel surveys.
17. Key Words Pedestrian and bicyclist risk assessment, exposure, geographic scale, risk factors, pedestrian and bicyclist counts, demand estimation, national travel surveys		18. Distribution Statement
19. Security Classif. (of this report) Unclassified	20. Security Classif. (of this page) Unclassified	21. No. of Pages 122	22. Price

TABLE OF CONTENTS

• LIST OF FIGURES
• LIST OF TABLES
• LIST OF ABBREVIATIONS
• GLOSSARY
• ACKNOWLEDGMENTS
• SUMMARY
• INTRODUCTION
  • Motivation for the Guide
  • Intended Audience
  • Organization of the Guide
• STEP 1. DETERMINE USE(S) OF RISK VALUES
  • Identifying Objectives of Risk Assessment
  • Typical Uses of Risk Values for Pedestrians and Bicyclists
  • Selecting Analysis Parameters in Remaining Steps of Risk Assessment
  • Assessing Available Data Resources and Analytic Capabilities
• STEP 2. SELECT GEOGRAPHIC SCALE
  • Considerations When Selecting Geographic Scale
  • Multiple Analysis Scales and Aggregation Considerations
• STEP 3. SELECT RISK DEFINITION
  • Definition 1: Observed Crash Rate
  • Definition 2: Expected Crashes
  • Definition 3: Additional Risk Indicators
• STEP 4. SELECT EXPOSURE MEASURE
• STEP 5. SELECT ANALYTIC METHOD TO ESTIMATE EXPOSURE
  • Site Counts
  • Demand Estimation Models
  • Travel Surveys
• STEP 6. USE ANALYTIC METHOD TO ESTIMATE SELECTED EXPOSURE MEASURE
  • Site Counts
  • Demand Estimation Models
  • Travel Surveys
• STEP 7. COMPILE OTHER REQUIRED DATA
  • Observed Crash Rate
  • Expected Crashes
  • Additional Risk Indicators
• STEP 8. CALCULATE RISK VALUES
  • Case Study: Pedestrian Risk Assessment in Michigan
  • Case Study Example for Arizona DOT Bicycle Safety Action Plan
• BIBLIOGRAPHY

LIST OF FIGURES

• Figure S-1. Eight Steps for Scalable Risk Assessment for Pedestrians and Bicyclists
• Figure 1. Eight Steps for Scalable Risk Assessment for Pedestrians and Bicyclists
• Figure 2. Example of Pedestrian Fatality Risk in 50 Cities
• Figure 3. Example of Pedestrian Risk Analysis in California Using Household Travel Surveys
• Figure 4. Example of Site Evaluation: Exclusive Pedestrian Phase at Single Intersection
• Figure 5. Illustration of Geographic Scales for Exposure Estimation
• Figure 6. Illustration of Combining Individual Crosswalks for Intersection Exposure
• Figure 7. Illustration of Estimating Intersection Exposure from Segment Counts
• Figure 8. Illustration of Multiple Parallel Facilities in a Corridor
• Figure 9. Illustration Showing Count Segments on Multiple Parallel Facilities in a Corridor
• Figure 10. Illustration of Multiple Segments Being Combined into Single Longer Segment
• Figure 11. Illustration of Multiple Census Tracts Being Combined into Single Region
• Figure 12. Historical Trends for Observed Bicycle Crash Rates in Wisconsin
• Figure 13. Locations in Seattle with High Risk of Pedestrian Crashes based on Expected Crashes
• Figure 14. Calculating Distance Traveled Exposure Measure from Segment Counts
• Figure 15. Calculating Time Traveled by Expanding Household Travel Surveys
• Figure 16. Estimating Count-Based Exposure at Intersections
• Figure 17. Direct Demand Model Development Process
• Figure 18. Direct Demand Model Development Detailed Flow Chart
• Figure 19. Household Survey Data Relationships
• Figure 20. Expanding Household Samples to Represent All Households in a Region
• Figure 21. Annual Non-Motorized Exposure Estimates, Non-Motorized Fatalities, and Risk
• Figure 22. Interface of the Statewide Exposure Estimates Tool Component
• Figure 23. Interface of the MPO Area Exposure Estimates Tool Component
• Figure 24. Geography Comparison
• Figure 25. ACS Data for Texas
• Figure 26. Joining of ACS Commuting Data with ACS Shapefile Data
• Figure 27. Map for Bicycle Commuting in Texas Census Tracts
• Figure 28. State-Level Annual Person Trips in NHTS Online Analysis Tool
• Figure 29. Table Designer Custom Query Tool for the 2009 NHTS
• Figure 30. Table Designer Custom Query Tool for the 2017 NHTS
• Figure 31. Step 5 Demand Estimation Using Pedestrian Trip Generation and Flow Models.
• Figure 32. Pedestrian Trip Generation Model Results for home-based other trips
• Figure 33. Daily pedestrian trips made per PAZ for Wayne county Michigan
• Figure 34. Step 7: Compile other required data
• Figure 35. Risk measured as the expected number of crashes per PAZ
• Figure 36. Level-of-Service-of-Safety (LOSS) map derived from the risk values
• Figure 37. Higher-Risk Locations for Bicyclists on the Arizona State Highway System

LIST OF TABLES

• Table S-1. Four Scale Categories in the Scalable Risk Assessment Process
• Table S-2. Three Possible Definitions of Pedestrian and Bicyclist Risk
• Table S-3. Selection Matrix for Exposure Measures
• Table S-4. Selection Matrix for Analytic Methods to Estimate Exposure
• Table 1. Example of Pedestrian Fatality Risk by Age and Gender
• Table 2. Example of Systemic Safety Analysis that Includes Exposure Variables
• Table 3. Example of Multi-Criteria Project Prioritization
• Table 4. Example of Exposure Measures Included in Countermeasure Evaluation
• Table 5. Selecting Key Parameters Based on Use(s) of Risk Values
• Table 6. Four Scale Categories in the Scalable Risk Assessment Process
• Table 7. Illustration of Combining BMT for Multiple Parallel Facilities in a Corridor
• Table 8. Three Possible Definitions of Pedestrian and Bicyclist Risk
• Table 9. Historical Trends for Observed Bicycle Crashes in Wisconsin
• Table 10. Example of Ranking Signalized Intersections based on Multiple Risk Indicators
• Table 11. Selection Matrix for Exposure Measures
• Table 12. Strengths and Limitations for Exposure Measure Categories
• Table 13. Extracting Population-Based Exposure from ACS Data Tables
• Table 14. Selection Matrix for Analytic Methods to Estimate Exposure
• Table 15. Key Guidance Documents for Site Counts
• Table 16. Advantages and Disadvantages of Direct Demand Models
• Table 17. Sampling Techniques
• Table 18. Key Explanatory Variables of Pedestrian and Bicyclist Direct Demand Models
• Table 19. Examples of Recent Direct-Demand Models to Estimate Pedestrian and Bicycle Volumes
• Table 20. Strengths and Limitations of the ACS in Estimating Pedestrian and Bicyclist Travel
• Table 21. 2017 NHTS State DOT & MPO Add-on Household Sample Sizes
• Table 22. Bike - CBSA Peer Groupings
• Table 23. Walk - CBSA Peer Groupings
• Table 24. ACS Data Attributes for Pedestrian and Bicycle Commute Estimates from Table B08301
• Table 25. Structure of 2009 and 2007 NHTS Data Files
• Table 26. 2017 NHTS Annual Person Miles of Travel (millions) by Mode and State
• Table 27. Eight Steps for the Scale Risk Assessment Methodology as Applied to this Case
• Table 28. Summarizes the Factors and Scoring for the Risk Assessment Process
• Table 29. Bicyclist/Motor-Vehicle Risk Assessment Levels

LIST OF ABBREVIATIONS

• AADT Annual average daily traffic
• ACS American Community Survey
• BMT Bicycle-miles of travel
• CBSA Core based statistical areas
• CHTS California Household Travel Survey
• DOT Department of Transportation
• FARS Fatality Analysis Reporting System
• FHWA Federal Highway Administration
• GIS Geographic information system
• HAWK High intensity Activated crossWalK
• HCM Highway Capacity Manual
• HSM Highway Safety Manual
• MEP Million entering pedestrians
• MEV&P Million entering vehicles and pedestrians
• MnDOT Minnesota Department of Transportation
• MoPeD Model of Pedestrian Demand
• MPO Metropolitan planning organization
• NCHRP National Cooperative Highway Research Program
• NHTSA National Highway Traffic Safety Administration
• NHTS National Household Travel Survey
• PBCAT Pedestrian and Bicycle Crash Analysis Tool
• PMT Pedestrian-miles of travel
• SCAG Southern California Association of Governments
• TAZ Traffic analysis zone
• TIGER/Line Topologically integrated geographic encoding and referencing
• TDM Travel demand model
• T-MAP Trail Modeling and Assessment Platform
• VMT Vehicle-miles of travel

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