NCHRP Web-Only Document 408

Design Options to Reduce Conflicts Between Turning Motor Vehicles and Bicycles

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COOPERATIVE RESEARCH PROGRAMS

CRP STAFF FOR NCHRP WEB-ONLY DOCUMENT 408

Monique R. Evans, Director, Cooperative Research Programs

Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program

Richard A. Retting, Senior Program Officer

Dajaih Bias-Johnson, Senior Program Assistant

Natalie Barnes, Director of Publications

Heather DiAngelis, Associate Director of Publications

Jennifer Correro, Assistant Editor

NCHRP PROJECT 15-73 PANEL
Field of Design—Area of General Design

Roy Gothie, Pennsylvania Department of Transportation, Harrisburg, PA (Chair)

Rachel Carpenter, California Department of Transportation, Sacramento, CA

Mohammad Jalayer, Rowan University, Glassboro, NJ

Donna C. Lewandowski, Stanley Consultants, Phoenix, AZ

Michelle Mayer, Port Authority of New York and New Jersey, Jersey City, NJ

Carissa Dale McQuiston, Michigan Department of Transportation, Lansing, MI

Cara B. Seiderman, City of Cambridge (MA), Cambridge, MA

Brian Wood, Washington State Department of Transportation, Olympia, WA

Brooke Struve, FHWA Liaison

AUTHOR ACKNOWLEDGMENTS

The research reported herein was performed under NCHRP Project 15-73 by Toole Design Group, with Portland State University, Safe Streets Research & Consulting, and Oregon State University serving as research partners.

Contents

SUMMARY

INTRODUCTION

Research Objective and Project Process

Report Organization

LITERATURE REVIEW

Measures of Safety

Findings

Summary of Findings and Gaps

SUMMARY OF DESIGN GUIDELINES

State and National Resources Overview

Additional Details for Key Resources

Guidance Related to Bicyclist Comfort

PRACTITIONER INTERVIEWS

Methodology

Interview Results

Summary of Findings

OVERVIEW OF RESEARCH METHODS AND SITE SELECTION

Overview of Research Methods

Site Selection

CRASH ANALYSIS

Macro Crash Analysis

Micro Crash Analysis

Descriptive Results (All Cities)

Statistical Model Results (Austin, Minneapolis and Seattle Only)

Micro Crash Analysis Summary

VIDEO-BASED CONFLICT ANALYSIS

Site Selection

Video Data Collection

Conflict Identification

Conflict Analysis Methods

Conflict Analysis Results

Conflict Analysis Summary

HUMAN FACTORS STUDY FOR SELECTED SITES

Research Design and Methods

Human Factors Study Data Analysis & Results

Human Factors Study Summary

SYNTHESIS AND SUMMARY OF RESEARCH RESULTS

Safety Performance

Risk Factors

Conclusions

Limitations and Future Research

DECISION TOOL AND GUIDELINES SUMMARY, IMPLEMENTATION AND TRAINING

Decision Tool and Design Guidelines Content Overview

Implementation and Training

REFERENCES

APPENDICES

Appendix A: Overview of Studies

Appendix B: Interview Protocol

Appendix C: Desktop Data Collection Fields

Appendix D: Macro Crash Analysis

Appendix E: Conflict Analysis Site by Site Graphics

Appendix F: Speed Profiles Plots

List of Figures

Figure 1. NCHRP 15-73 Project Process

Figure 2. Hydén’s safety pyramid (Laureshyn and Várhelyi 2018)

Figure 3. Dedicated intersection design (NACTO 2019)

Figure 4. Schematic of Intersection Treatment Type Studied

Figure 5. Average crashes per year per 1,000 bicyclists – Austin, Minneapolis, and Seattle

Figure 6. Average crashes per year per 1,000 bicyclists – New York

Figure 7. Video Screen Capture of Conventional Bike Lane Sites

Figure 8. Video Screen Capture of Pocket or Keyhole Bike Lane Sites

Figure 9. Video Screen Capture of Separated Bike Lane Sites

Figure 10. Video Screen Capture of Mixing Zone Sites

Figure 11. Video Screen Capture of Offset/Protected Intersection Sites

Figure 12. Conflict Areas for Each Treatment Type

Figure 13. Sample Trajectory Tracing at 12th Ave NE and NE 65th St (Separated Bike Lane / Seattle)

Figure 14. Data Cleaning Process and Results

Figure 15. Mean Post Encroachment Time for Treatment Type (PET <= 5 sec)

Figure 16. Mean Speed (mi/h) at the Conflict Point by Location and Treatment Type (CBL – Conventional Bike Lane, KEY – Pocket or Keyhole Bicycle Lane, SBL – Separated Bike Lane, PRO – Offset or Protected Intersection)

Figure 17. Mean and 85th Percentile Speed (mi/h) at the Conflict Point by Treatment Type

Figure 18. Vehicle Speed at the Conflict Point and PET by Treatment Type

Figure 19. Observed Proportions of Conflicts by Severity and Treatment Type

Figure 20. CURE Plots for Treatment Type Conflict Frequency Models

Figure 21. IRR for Exposure in Severe Conflict Frequency Models

Figure 22. Predicted Number of Severe Conflicts for 50 bicycles per hour and Hourly Turning Volumes

Figure 23. Predicted Frequency of Severe Conflicts for Volume Ranges

Figure 24 Change in Probability for High Severity Conflict Due to Vehicle Speed

Figure 25 Change in Probability for High Severity Conflict Due to Truck, Box Truck or Bus

Figure 26. Change in Probability for High Severity Conflict Due to Vehicle Arriving First

Figure 27. Change in Probability for High Severity Conflict Due to Same Direction Conflict

Figure 28. Comparison of Total and Turning Crashes at Approach per Year vs. Conflicts per hour

Figure 29. Development of Protected Bike Lane (6’ Offset, no parallel parking) Intersection in Blender

Figure 30. Desktop Driving Simulator: (A) Triple Monitor Display, (B) Steering and Pedal System

Figure 31. Full-Scale Passenger Car Simulator

Figure 32. Tobii Pro Glasses 3 Eye Tracker: (A) Full System, (B) Outfitted on Participant

Figure 33. Shimmer3 iMotions GSR

Figure 34. Screenshot of Intersection Approaches by Configuration: (A) Conventional Bike Lane, (B) Pocket/Keyhole Bike Lane, (C) Mixing Zone Intersection (with parallel parking) and (D) Protected Intersection (18’ offset, with parallel parking)

Figure 35. Schematic of Cyclist Location Levels

Figure 36. Driver and Cyclist Locations by Cyclist Proximity: (A) Cyclist located closer to the intersection, (B) Cyclist located further from the intersection

Figure 37. Mixing Zone and Offset / Protected Intersection Approaches by Parallel Parking Level

Figure 38. Protected Intersection Approaches by Offset: (A) Offset = 6 feet, (B) Offset = 18 feet

Figure 39. Experimental Grid: Tile Organization and Subsequent Experimental Drive Route (Grid 2 depicted)

Figure 40. Data Collection Zones: (A) Pocket/Keyhole Bike Lane, (B) Mixing Zone Intersection

Figure 41. Data Collection Zones: (A) Conventional Bike Lane, (B) Protected Bike Lane, Offset = 6 feet, (C) Protected Intersection, Offset = 18 feet

Figure 42. Distribution of Total Fixation Duration on Cyclist by Scenario

Figure 43 - Distribution of Total Fixation Duration on Pavement Markings by Scenario

Figure 44. Distribution of Total Fixation Duration on Parallel Parking by Scenario

Figure 45. Distribution of Total Fixation Duration on Rear-View and Right Side-view Mirrors by Scenario

Figure 46. Distribution of Average Speeds per Zone by Scenario (Cyclist = Near)

Figure 47. Distribution of Average Speeds per Zone by Scenario (Cyclist = Far)

Figure 48. Distribution of Minimum Speeds in Transition and Turn Zones by Scenario (Cyclist = Near)

Figure 49. Distribution of Minimum Speeds in Transition and Turn Zones by Scenario (Cyclist = Far)

Figure 50. Distribution of Maximum Peaks per Minute Across All Zones by Scenario

Figure 51. Speed Profile versus Visual Attention on Cyclist (cyclist located closer to the intersection) by Intersection: (A) Conventional Bike Lane, (B) Pocket/Keyhole Bike Lane, (C) Mixing Zone (no parallel parking), (D) Mixing Zone (with parallel parking), (E) Protected Intersection (6’ offset, no parallel parking), (F) Protected Intersection (6’ offset, with parallel parking), (G) Protected Intersection (18’ offset, no parallel parking) and (H) Protected Intersection (18’ offset, with parallel parking)

Figure 52. Speed Profiles with and Without Parking

Figure 53. Schematic of Intersection Treatment Type Studied

Figure 54. NCHRP 15-73 Project Process

List of Tables

Table 1. Summary of methods to evaluate safety performance

Table 2. Summary of key research using surrogate measures for vulnerable road users

Table 3. National resources, design guidance, context, and intersection design process

Table 4. Design principles for key resources

Table 5. Sustainable safety considerations for bikeway intersection types (FHWA 2021)

Table 6. List of jurisdictions interviewed

Table 7. Agency Use of Design Guidance and Overarching Frameworks

Table 8. Factors agencies consider to select design treatments

Table 9. Design issues and constraints

Table 10. Used or preferred bikeway intersection design treatments

Table 11. Agency-identified design treatments with knowledge gaps

Table 12. Agency-identified knowledge gaps and research questions

Table 13 Research Methods Deployed: Strengths and Disadvantages

Table 14. Count of Sites by Treatment Type and City Identified, Excluded and Retained

Table 15. Summary of Available Data and Analyses for Each City

Table 16. Sample size and exclusions

Table 17. Number of fatal and injury (KABC) crashes by city

Table 18. Number of severe (KA) crashes by city

Table 19. Number of approaches with exposure data (average daily bicyclists) by city

Table 20. Summary statistics of average daily bicyclist volumes by city

Table 21. Number of approaches with at least two years of crash data by intersection treatment type

Table 22. Crash counts and volume estimates by treatment type – Austin, Minneapolis and Seattle combined. Approaches with non-missing volume data only

Table 23. Crash counts and volume estimates by treatment type – New York Only. Approaches with non-missing volume data only

Table 24. Crash counts by treatment type and bikeway type – Austin, Minneapolis, and Seattle combined

Table 25. Crash counts by treatment type and bikeway type – New York Only

Table 26. Crash counts by treatment type and curb-tight bikeway status – Austin, Minneapolis and Seattle Combined

Table 27. Crash counts by treatment type and curb-tight bikeway status – New York

Table 28. Crash counts by treatment type and bikeway type side of street – Austin, Minneapolis and Seattle Combined

Table 29. Crash counts by treatment type and bikeway side of street – New York

Table 30. Crash counts by skew angle – Austin, Minneapolis and Seattle combined

Table 31. Crash counts by skew angle – New York

Table 32. Crash counts by left turn lanes and assumed signal phasing – Austin, Minneapolis and Seattle combined.

Table 33. Crash counts by left turn lanes and assumed signal phasing – New York

Table 34. Crash counts by number of lanes on cross-street – Austin, Minneapolis and Seattle combined

Table 35. Crash counts by number of lanes on cross-street – New York

Table 36. Crash counts by speed limit – Austin, Minneapolis and Seattle combined

Table 37. Crash counts by speed limit – New York

Table 38. Negative binomial regression on number of bicyclist—motorist crashes on approach

Table 39. Bikeway design type count by city

Table 40. Conflict analysis sites and key characteristics

Table 41. Video data collection hours

Table 42. Summary of Conflict Severity Used in Modeling Analysis

Table 43. Number of Conflicts (PET ≤ 5 sec) and Treatment Type

Table 44. Number of High Severity Conflicts (PET ≤ 1.5 sec) and Treatment Type

Table 45. Total Frequency of Conflicts and Exposure Measures by treatment type and location

Table 46. Conflicts by treatment type and city

Table 47. Frequency and Percentage of Conflicts by Treatment Type and PET Thresholds

Table 48. Number of Conflicts by Location, City, Treatment Type and PET

Table 49. Vehicle Speed at Conflict Point by Treatment Type and Location (mi/h)

Table 50. Frequency and proportion of conflicts by treatment type, PET and vehicle speed

Table 51. Transferability Test for Conflict Frequency Models

Table 52. Transferability Test for Conflict Severity Models

Table 53. Poisson Model Specifications for Conflict Frequency in Conventional Bike Lanes

Table 54. Poisson Model Specifications for Conflict Frequency in Separated Bike Lanes

Table 55. Poisson Model Specifications for Conflict Frequency in Protected Intersections

Table 56. Poisson Model Specifications for Conflict Frequency in Mixing Zones

Table 57. Ordered Probit Model Specifications of Conflict Severity in Conventional Bike Lanes

Table 58. Marginal Effects on Conflict Severity in Conventional Bike Lanes

Table 59. Ordered Probit Model Specifications of Conflict Severity in Pocket / Keyhole Bike Lanes

Table 60. Marginal Effects on Conflict Severity in Pocket / Keyhole Bike Lanes

Table 61. Ordered Probit Model Specifications of Conflict Severity in Separated Bike Lanes

Table 62. Marginal Effects on Conflict Severity in Separated Bike Lanes

Table 63. Ordered Probit Model Specifications of Conflict Severity in Mixing Zones

Table 64. Marginal Effects on Conflict Severity in Mixing Zones

Table 65. Ordered Probit Model Specifications of Conflict Severity in Protected Intersections

Table 66. Marginal Effects on Conflict Severity in Protected Intersections

Table 67. Binary Logit Model Specifications for High Severity Conflicts in Conventional Bike Lanes

Table 68. Binary Logit Model Specifications for High Severity Conflicts in Pocket / Keyhole Bike Lanes

Table 69. Binary Logit Model Specifications for High Severity Conflicts in Separated Bike Lanes

Table 70. Binary Logit Model Specifications for High Severity Conflicts in Mixing Zones

Table 71. Binary Logit Model Specifications for High Severity Conflicts in Protected Intersections

Table 72. Summary of Marginal Effects

Table 73. Independent Variables and Levels

Table 74. Factorial Design Matrix

Table 75. Scenario Order by Grid

Table 76. Zone Lengths by Scenario

Table 77. Gender and Age Distribution

Table 78. Participant Sample Size

Table 79. Data Usability

Table 80. Sample Demographics

Table 81. Sample Cycling Experience (Self-reported)

Table 82. Descriptive Statistics of the Distribution of Total Fixation Duration on Cyclists by Scenario

Table 83. Descriptive Statistics of the Distribution of Total Fixation Duration on Pavement Markings by Scenario

Table 84. Descriptive Statistics of the Distribution of Total Fixation Duration on Parallel Parking by Scenario

Table 85. Descriptive Statistics of the Distribution of Total Fixation Duration on Mirrors by Scenario

Table 86. Descriptive Statistics of Average Speeds per Zone by Scenario (Cyclist = Near)

Table 87. Difference in Average Speed from No Parallel Parking Scenario to Parallel Parking Present Scenario …

Table 88. Descriptive Statistics of Average Speeds per Zone by Scenario (Cyclist = Far)

Table 89. Difference in Average Speed from No Parallel Parking Scenario to Parallel Parking Present Scenario

Table 90. Descriptive Statistics of Minimum Speeds in Transition and Turn Zones by Scenario (Cyclist = Near)

Table 91. Descriptive Statistics of Minimum Speeds in Transition and Turn Zones by Scenario (Cyclist = Far)

Table 92. Descriptive Statistics of Distribution of Maximum Peaks per Minute Across All Zones by Scenario

Table 93. Reported Level of Familiarity with Intersections

Table 94. Level of Comfort by Presence of Cyclist per Intersection

Table 95. Reported Effect of Parallel Parking on Visibility of Cyclist

Table 96. Summary findings by intersection treatment type