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REPORT
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Publication Number:  FHWA-HRT-17-086    Date:  January 2018
Publication Number: FHWA-HRT-17-086
Date: January 2018

 

Safety Evaluation of Multiple Strategies at Stop-Controlled Intersections

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FOREWORD

The research documented in this report was conducted as part of the Federal Highway Administration’s (FHWA) Evaluation of Low-Cost Safety Improvements Pooled Fund Study (ELCSI-PFS). FHWA established this PFS in 2005 to conduct research on the effectiveness of the safety improvements identified by the National Cooperative Highway Research Program Report 500 Guides as part of the implementation of the American Association of State Highway and Transportation Officials Strategic Highway Safety Plan.(1) The ELCSI-PFS studies provide a crash modification factor and benefit–cost economic analysis for each of the targeted safety strategies identified as priorities by the pooled fund member States.

This study evaluated multiple low-cost safety improvements at stop-controlled intersections that included basic signing and pavement markings. This strategy is intended to reduce the frequency and severity of crashes at stop-controlled intersections by alerting drivers approaching a stop-controlled intersection. The results indicate reductions for all crash types (i.e., total, fatal and injury, rear-end, right-angle, and nighttime crashes). The economic analysis results suggest that the multiple low-cost treatments at stop-controlled intersections, even with conservative assumptions on cost, service life, and the value of a statistical life, can be cost effective. This report is intended for safety engineers, highway designers, planners, and practitioners at State and local agencies involved with AASHTO Strategic Highway Safety Plan implementation.

Jonathan Porter, Ph.D.
Acting Director, Office of Safety
Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation (USDOT) 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-17-086
2. Government Accession No. 3. Recipient's Catalog No.
4. Title and Subtitle
Safety Evaluation of Multiple Strategies at Stop-Controlled Intersections
5. Report Date
January 2018
6. Performing Organization Code
7. Author(s)
Thanh Le, Frank Gross, Bhagwant Persaud, Kimberly Eccles, and Jonathan Soika
8. Performing Organization Report No.
9. Performing Organization Name and Address
VHB
8300 Boone Blvd., Ste. 700
Vienna, VA 22182-2626

Persaud and Lyon, Inc
87 Elmcrest Road
Toronto, Ontario M9C 3R7
10. Work Unit No.
11. Contract or Grant No.
DTFH61-13-D-00001
12. Sponsoring Agency Name and Address
U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
13. Type of Report and Period Covered
Safety Evaluation Final Report; October 2010–September 2017
14. Sponsoring Agency Code
HRDS-20
15. Supplementary Notes.
FHWA Office of Safety Research and Development managed this study under the Development of Crash Modification Factors program. The FHWA Office of Safety Research and Development Program and Task Manager was Roya Amjadi (HRDS-20).
16. Abstract
The Development of Crash Modification Factors program studied the safety performance of various stop-controlled intersections for the Evaluation of Low-Cost Safety Improvements Pooled Fund Study. This study evaluated the safety effectiveness of multiple low-cost treatments at stop-controlled intersections. Improvements included basic signing and pavement markings. This strategy is intended to reduce the frequency and severity of crashes at stop-controlled intersections by alerting drivers to the presence and type of approaching intersection. Geometric, traffic, and crash data were obtained at three- and four-legged, two- and four-lane major road, and urban and rural stop-controlled intersections in South Carolina. To account for potential selection bias and regression to the mean, an empirical Bayesian before–after analysis was conducted, using reference groups of untreated intersections with similar characteristics to the treated sites. The analysis also controlled for changes in traffic volumes throughout time and time trends in crash counts unrelated to the treatments. The aggregate results indicate reductions for all crash types analyzed (i.e., total, fatal and injury, rear-end, right-angle, and nighttime). The reductions are statistically significant at the 95-percent confidence level for all crash types. For all crash types combined, the crash modification factors (CMFs) are 0.917 for all severities and 0.899 for fatal and injury crashes. The CMFs for rear-end, right-angle, and nighttime crashes are 0.933, 0.941, and 0.853, respectively. The benefit–cost ratio estimated with conservative cost and service life assumptions is 12.4 to 1 for total crashes at unsignalized intersections. The results suggest that the multiple low-cost treatments, even with conservative assumptions on cost, service life, and the value of a statistical life, can be cost effective.
17. Key Words
Stop-controlled, unsignalized, intersection, low cost, safety improvements, safety evaluations, empirical Bayesian, before–after, multi-strategy, multiple treatments
18. Distribution Statement
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.
http://www.ntis.gov
19. Security Classif. (of this report)
Unclassified
20. Security Classif. (of this page)
Unclassified
21. No. of Pages:
99
22. Price
Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized.

SI* (Modern Metric) Conversion Factors

Table of Contents

List of Figures

List of Tables

List of Abbreviations

AADT annual average daily traffic
B/C benefit–cost
CMF crash modification factor
EB empirical Bayesian
ELCSI-PFS Evaluation of Low-Cost Safety Improvements Pooled Fund Study
FHWA Federal Highway Administration
MUTCD Manual on Uniform Traffic Control Devices
NCHRP National Cooperative Highway Research Program
PDO property damage only
PE preliminary engineering
RTM regression to the mean
SCDOT South Carolina Department of Transportation
SPF safety performance function
USDOT U.S. Department of Transportation

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