SIGNAL TIMING UNDER SATURATED CONDITIONS

1. Report No.

FHWA-HOP-09-008

2. Government Accession No.

3. Recipient's Catalog No.

4. Title and Subtitle

Signal Timing Under Saturated Conditions

5. Report Date

November 2008

6. Performing Organization Code

7. Author(s)

Principal Investigator: Richard W. Denney, Jr., P.E.
Co-Authors: Larry Head, Ph.D., Kevin Spencer

8. Performing Organization Report No.

Project

9. Performing Organization Name and Address

Booz Allen
Sub-consultants: Iteris, Inc.; University of Arizona; Econolite

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

Contract No. DTFH61-06-D-00006

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

Final Report
October 2006 to September 2008

14. Sponsoring Agency Code

HOP

15. Supplementary Notes

Eddie Curtis (Eddie.Curtis@fhwa.dot.gov) was the Technical Representative for the Federal Highway Administration. Agency experts and consultants provided interviews in support of identifying the state of the practice, including:

• Gerard de Camp, independent consultant
• Steven Click, Tennessee Tech University (formerly with North Carolina DOT)
• Woody Hood, Maryland State Highway Administration
• Eric Nelson, Harris County (Texas) Department of Transportation
• Gary Pietrowicz, Road Commission of Oakland County (Michigan)
• Ziad Sabra, Sabra-Wang and Associates
• Bill Shao, Los Angeles Department of Transportation

16. Abstract

This report provides guidance to practitioners on effective strategies to mitigate the effects of congestion at signalized intersections. The scope is limited to single intersections and does not address network-level strategies. The strategies are defined in terms of their underlying objective. Under congested conditions, traditional objectives and performance measures shift from progression and minimizing delay to maximizing throughput and managing queues. Experts were interviewed to identify the strategies and tactics they used to address congested intersections, a discussion of their methods is presented. Select strategies were studied further, particularly the belief that longer cycles are more efficient, and the effects of buses on signal timing in grid networks. The research revealed that long cycle lengths may not be more efficient at intersections where long queues starve turn lanes. In grid networks, the cycle length that is just long enough to reliably serve busses from a near-side stop was found through simulation to prevent the development of residual queues.

17. Key Words

Signalized Intersections, Traffic Signal Timing, Congestion, Cycle Lengths, Throughput, Queue Management

18. Distribution Statement

No Restrictions. This document is available to the public.

19. Security Classification (of this report)

Unclassified

20. Security Classification (of this page)

Unclassified

21. No of Pages

76

22. Price

N/A