Coordinated actuated traffic signal systems produced a 30 percent reduction in corridor travel times compared to actuated isolated systems, resulting in a benefit/cost ratio of 461.3.
The study obtained data from two treatment sites in Virginia. The first site was in Gloucester County on Route 17, with five non-coordinated actuated signalized intersections, total length of about 2.4 miles, and a distance between intersections from 0.15 mile to 1.5 miles. The second site was in Chesterfield County on US 60, consisting of six signalized intersections and having a length of about 3 miles and a 0.15 to 1.4 mile distance between intersections. Site 1 was used to quantify the benefits of coordination by comparing corridor travel times and approach delays with and without coordination. Site 2 assessed impacts of an adaptive split feature within the coordinated actuated signal system. Average traffic volume on the main arterials was around 750 vehicles per hour per lane. The investigators developed a timing plan for each site to coordinate the traffic signals. Synchro, a macroscopic traffic signal timing evaluation and optimization software, was used to generate the coordinated actuated traffic signal timing plans for comparison purposes. The timing plan was based on the site's traffic volume and geometry. Before data included stopped delay and travel time, gathered from manual traffic counters and video cameras for traffic volume counts at intersections and the stopped delay at key approaches. Researchers used vehicles equipped with GPS devices to obtain corridor travel times.
The coordinated actuated system improved corridor performance over the actuated isolated systems. At the first site in Gloucester County,
- Corridor travel times improved by 30 to 34 percent over the non-coordinated system.
- The traffic signal coordination was well maintained over 1 mile spacing between intersections, a finding which contrasts to the conventional wisdom that coordination is not necessary when spacing is longer than 3/4 mile.
- The benefit/cost ratio of the coordinated actuated traffic signal system was 461.3 relative to the non-coordinated system.
- The analysis found that the coordinated system resulted in a corresponding increase in stopped delay over the non-coordinated approaches by about 14 percent. To mitigate this effect, VDOT implemented an adaptive split feature that resulted in time savings from 18 and 35 percent on the non-coordinated cross streets, without having an impact on the coordinated approaches.
Author: Park, Byungkyu (Brian), and Yin Chen.
Published By: Virginia DOT
Prepared by the Virginia Transportation Research Council for the Virginia DOT
Source Date: September 2010
Other Reference Number: Report No. VTRC 11-CR2URL: http://www.virginiadot.org/vtrc/main/online_reports/pdf/11-cr2.pdf
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