The estimated benefit-to-cost ratio for optimizing signal timing plans, coordinating traffic signal control, and implementing adaptive signal control in California was 17:1.
The TRANSYT-7F model estimates from 163 of the 334 FETSIM projects (49 percent), representing 55 percent of the total number of signals retimed, demonstrated positive results from signal retiming of coordinated signal systems. The study found an average 7.7 percent reduction in travel time, 13.8 percent reduction in delays, 12.5 percent reduction in stops and 7.8 percent decline in fuel use. This study excluded TRANSYT-7F results for oversaturated approaches, as the simulation overestimates the benefits of retiming under these conditions. Results of "before" and "after" floating car studies reported by some of the jurisdictions support the TRANSYT-7F figures. The average reductions reported by the floating car studies were: 7.4 percent in travel time, 16.5 percent in delay, and 17 percent in stops. The differences between these figures and the TRANSYT-7F values are due to the survey routes selected by the projects, which did not cover each link of the retimed signal network.
There was considerable variation in the improvement achieved by the retiming projects, for a variety of reasons:
- Quality of existing timing plans: When existing timing plans were already performing well, there was often little benefit in signal optimization.
- Network configuration: The largest savings were obtained on arterials, rather than signalized grid networks.
- Traffic Patterns: High volume systems with predominant through movements achieved the greatest improvements. Savings were marginal on systems containing several congested intersections in need of capacity improvements.
- Signal Equipment: Systems with actuated signals and easily modifiable control parameters achieved greater benefits.
ITS Benefits: The Case of Traffic Signal Control Systems
Author: Skabardonis, Alexander
Published By: Paper presented at the 80th Annual Transportation Research Board Meeting. Washington, District of Clolumbia
Source Date: 7-11 January 2001
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traffic signals, adaptive signals, coordinated signals, signal coordination, centralized signal control, signal synchronization, advanced signal control, signal timing optimization, coordinated signal control, advanced signal controller, traffic signal retiming, retiming, Coordinated signal timing, pre-timed, pretimed, time-of-day signal timing, fixed-time