Surrogate Safety Measures From Traffic Simulation Models

Final Report
PDF Version (903 kb)

Publication No: FHWA-RD-03-050

View the Table of Contents

U.S. Department of Transportation
Federal Highway Administration
Research, Development, and Technology

Office of Safety Research and Development
Turner-Fairbank Highway Research Center
6300 Georgetown Pike
McLean, Virginia 22101

   Technical Report Documentation Page

Form DOT F 1700.7              (8-72)      Reproduction of completed page authorized

SI* (Modern Metric) Conversion Factors

FOREWORD

This report summarizes the activities and results of a project to evaluate the assessment of surrogate measures of safety for traffic intersections from existing, commercially available traffic simulation models. The objective of the project was to evaluate the various simulation models’ capabilities for producing measures of intersection safety and specify algorithms for calculating the measures.

Copies of this report can be obtained from the Research and Technology Report Center, 9701 Philadelphia Court, Unit Q, Lanham, Maryland 20706; telephone: (301) 577-0818; fax: (301) 577-1421; or the National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, Virginia 22161; telephone: (703) 487-4650; fax: (703) 321-8547.

NOTICE

This document is disseminated under the sponsorship of the U.S.  Department of Transportation in the interest of information exchange. The United States Government assumes no liability for its contents or use thereof. This report does not constitute a standard, specification, or regulation.  The U.S. government does not endorse products or manufacturers.  Trade and manufacturers’ names appear in this report only because they are considered essential to the object of this document.

TABLE OF CONTENTS

1. Introduction
   
   
2. Literature Review
   
   Conflicts
     Conflict Severity
     Ranking Conflict Measures on Collection Desirability
   Other Surrogate Measures
   Surrogate Measures From Microscopic Simulations
     General-Purpose Microscopic Models
   Literature Summary
   
   
3. Traffic Simulation Model Overview
   
   General
   Behavior Modeling
   Data Extraction
   Calibration and Parameters
   Cost
   
   
4. Discussion of Microscopic Simulation Model Comparisons
   
   CORSIM
   SIMTRAFFIC
   VISSIM
   HUTSIM
   Paramics
   Integration
   AIMSUN
   WATSIM
   Texas
   
   
5. Summary of Simulation Model Features Review
   
   
6. SSAM Functional Requirements
   
   Functional Requirements Development Process
     System Owner, Users, and Stakeholders
     SSAM Objectives
     Concept of Operation of the SSAM
   Use Case Analysis
     System Users
     Use Case Packages
   User Interface Mock-Ups
   Functional Requirements
   
   
7. Algorithms for Surrogate Measures of Safety at Intersections
   
   Conflict Event Descriptions
     Crossing Flows—Conflict Point Events
     Merging Crossing Flows—Conflict Line Events
     Adjacent Flows—Lane-Changing Conflict Line Events
     Following Flows—Rear-End Conflict Line Events
     Collision Types Not Represented in the Surrogate Measures
     Pedestrian Collisions
     U-Turn-Related Collisions
     Summary
     Unrepresented Evasive Maneuvers
     Significant Unrepresented Conflict Event Contributors
   Conflict Point
   Conflict Line
   Rear-End Conflict Line
   Summary of Conflict Points, Lines, and Rear-End Lines
   Surrogate Measures Definitions
     Severity of Conflict and Severity of Resulting Collision
   Surrogate Measures for Conflict Points
   Time To Collision
     Post-Encroachment Time
     MaxS
     DeltaS
     Initial Deceleration Rate
     Location of the Conflict Point
   Computational Algorithms—Conflict Points
   Surrogate Measures for Conflict Lines With Merging Flows
     Time To Collision
     Post-Encroachment Time
     MaxS
     DeltaS
     Initial Deceleration Rate
     Location of the Conflict Line
   Computational Algorithms—Conflict Lines for Merging Flows
   Surrogate Measures for Rear-End Conflict Lines
     Time To Collision
     Post-Encroachment Time
     MaxS
     DeltaS
     Initial Deceleration Rate
     Location of the Conflict Line
   Computational Algorithms—Rear-End Conflict Lines
   Summary
   
   
8. Event File Specification
   
   Elements in the Event File
     Elements in the Header
     Elements in Each Time Step
     Implications of File Size
     File Naming Conventions
   
   
9. Validation of Surrogate Measures
   
   Discrimination Between Intersection Design Alternatives
     Approach
   Correlation With Traffic Conflicts
     Approach
   Prediction of Reductions in Traffic Conflicts
     Approach
     Alternative Approach
   
   
10. Report Summary
    
    
11. References

LIST OF FIGURES

Figure 1. Requirements development process.
Figure 2. Event-file-based information flow diagram.
Figure 3. Use case package diagram.
Figure 4. Main application with network-level display.
Figure 5. Intersection close-up window.
Figure 6. Table display.
Figure 7. Graph display.
Figure 8. Distribution comparison display.
Figure 9. Workspace display.
Figure 10. Conflict point and lines.
Figure 11. Conflict point diagram.
Figure 12. Conflict line example.
Figure 13. Rear-end conflict line example.
Figure 14. Surrogate measures on conflict point diagram.
Figure 15. Surrogate measures on conflict line diagram.
Figure 16. Surrogates identified on rear-end line diagram.

LIST OF TABLES

Table 1. Table of surrogate safety conflict measures.
Table 2. General simulation characteristics comparison.
Table 3. Behavior modeling comparison.
Table 4. Data extraction capabilities comparison.
Table 5. Calibration and parameters comparison.
Table 6. Modification cost comparison.
Table 7. Use case actors.
Table 8. Install and upgrade use cases.
Table 9. Configure use cases.
Table 10. Operate use cases.
Table 11. Analysis use cases.
Table 12. Reporting use cases.
Table 13. Percentage of total intersection crashes made up of angle, rear-end, and pedestrian collisions (other and unknown percentages in parentheses).

Table of Contents | Next

TFHRC Home | FHWA Home | Feedback United States Department of Transportation - Federal Highway Administration