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Publication Number: FHWA-HRT-05-048
Date: April 2005

Safety Evaluation of Red-Light Cameras

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FOREWORD

This is a final report on a study to evaluate the effectiveness of red-light-camera (RLC) systems in reducing crashes. The intended audience is professionals who make decisions about safety programs for intersections. The study involved empirical Bayes before-and-after research using data from seven jurisdictions across the United States to estimate the crash and associated economic effects of RLC systems. The study included 132 treatment sites and specially derived rear end and right-angle unit crash costs for various severity levels. Crash effects detected were consistent in direction with those found in many previous studies: decreased right-angle crashes and increased rear end crashes. The economic analysis examined the extent to which the increase in rear end crashes negates the benefits for decreased right-angle crashes. There was indeed a modest aggregate crash cost benefit of RLC systems even when accounting for the negative impact of rear end collisions. The benefit of RLC systems could increase further, if measures were taken to educate or alert drivers that vehicles preceding them could be stopping suddenly for a red light and thus reduce the likelihood of a rear end crash. A disaggregate analysis found that the greatest economic benefits are associated with the highest total entering average annual daily traffic, the largest ratios of right-angle to rear end crashes, and with the presence of protected left-turn phases. There were weak indications of a spillover effect that point to a possible need for a more definitive, perhaps prospective, study of this issue.

Michael F. Trentacoste, Director
Offices of Safety Research and Development

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.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

Technical Report Documentation Page

1. Report No

FHWA-HRT-05-048

2. Government Accession No.

N/A

3. Recipient's Catalog No.

N/A

4. Title and Subtitle

Safety Evaluation of Red-Light Cameras

5. Report Date

April 2005

6. Performing Organization Code

N/A

7. Authors(s)

Forrest M. Council, BMI-SG; Bhagwant Persaud, Ryerson University; Kimberly Eccles, BMI-SG; Craig Lyon, Ryerson University; and Michael S. Griffith, Federal Highway Administration.

8. Performing Organization Report No.

N/A

9. Performing Organization Name and Address

Battelle Memorial Institute
505 King Avenue
Columbus, OH 43201

10. Work Unit No. (TRAIS)

N/A

11. Contract or Grant No.

DTFH61-96-C-00077

13. Type of Report and Period Covered

Final - 11/19/01 - 11/30/04

12. Sponsoring Agency Name and Address

ITS Joint Program Office and Office of Safety Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101

14. Sponsoring Agency Code

15. Supplementary Notes

Contracting Officer's Technical Representative:

Michael Griffith, FHWA Office of Safety Research and Development

16. Abstract

The objective of this final study was to determine the effectiveness of red-light-camera (RLC) systems in reducing crashes. The study used empirical Bayes before-and-after research using data from seven jurisdictions across the United States at 132 treatment sites. The purpose of the study was to estimate the crash and associated economic effects of RLC systems and specially derived rear end and right-angle unit crash costs for various severity levels. Crash effects detected were consistent in direction with those found in many previous studies: decreased right-angle crashes and increased rear end ones. The economic analysis examined the extent to which the increase in rear end crashes negates the benefits for right-angle crashes. The analysis showed an aggregate crash cost benefit of RLC systems. A disaggregate analysis found that the greatest economic benefits are associated with the highest total entering average annual daily traffic, the largest ratios of right-angle to rear end crashes, and with the presence of protected left turn phases. There were weak indications of a spillover effect that points to a need for a more definitive, perhaps prospective, study of this issue.

17. Key Words

Red light camera, Empirical Bayes, Crash evaluation, Economic analysis, Signalized intersection

18. Distribution Statement

No restrictions. This document is available to the Public through the National Technical Information Service; Springfield, VA 22161

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

95

22. Price

N/A

Form DOT F 1700.7 (8-72)

Reproduction of completed page authorized (art. 5/94)


SI* (Modern Metric) Conversion Factors

Table of Contents

Page

I. Executive Summary

II. Introduction

III. Project Overview

Phase I-Evaluation Design
Phase II-Evaluation Implementation

IV. Literature Review of Critical Studies

Summary of Findings
Lessons Learned and Issues Raised by Literature Search

V. Determination of Study Questions to be Answered

VI. Determination of RLC-Related Data Availability

VII. Methodology for National, MultiJurisdiction Study

Study Design Details
Basic Objectives and Main Analytical Requirements
Overview of the General Evaluation Methodology
Empirical Bayes Before-and-After Evaluation Example
Data Collection Plan
Choice of Jurisdictions
Selection of Study Jurisdictions
Data Collection Requirements

VIII. Study Methodology for Economic Analysis

Initial Economic Analysis Study Design
Examination of Alternative Economic Analysis Methods
Final Methodology for Economic Analysis
Types and Levels of Economic Cost Estimates
Choice of Cost Levels
Economic Analysis Statistical Method

IX. Data Collection

Crash Data
Intersection Inventory and Volume Data.

X. Data and SPF Preparation

Crash Data Linkage to Intersections
Defining Red-Light-Running Crashes
Development of Safety Performance Functions

XI. Results

Composite Effects at Camera sites
Spillover Effects
Discussion of Crash Effects
The Economic Analysis of RLC-Related Severity and Frequency Changes
Development of Unit Crash Cost Estimates
Empirical Bayes Estimates of the Economic Effects
Factors Affecting RLC Effectiveness

XII. Discussion and Conclusions

Appendix A. Sources of Data by Jurisdiction

Appendix B. Number of Treated, Reference, and Comparison Sites in Each Jurisdiction

Acknowledgments

References

Other References

List of Figures

Figure 1. Project workflow

List of Tables

Table 1. Summary of findings from past studies

Table 2. Summary of results for right-angle injury crashes at site (i)

Table 3. The composite effect over several sites (for illustration)

Table 4. P-values for various sample sizes and expected changes in safety

Table 5. After period crash rate assumptions

Table 6. Sample analysis for right-angle crash effects

Table 7. Sample analysis for rear end crash effects

Table 8. Best judgment on possibility of detecting safety effects

Table 9. Best judgment on sites to use based on crash and noncrash data available

Table 10. Data items required

Table 11. Definitions of crash types used in the analyses for each jurisdiction

Table 12. Safety performance functions for the signalized intersections reference group

Table 13. Combined results for the seven jurisdictions

Table 14. Results for individual jurisdictions

Table 15. Before-and-after results for total crashes at spillover intersections

Table 16. Original comprehensive crash cost estimates for urban signalized intersections

Table 17. Economic effects including and excluding PDOs

Table 18. Severity-level distributions for right-angle and rear end injury

Table 19. Data sources

Table 20: Sites by jurisdiction

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