A procedure for determining time-of-day break points for coordinated actuated traffic signal systems

Abstract

This paper presents the development and evaluation of a procedure for determining optimal break points for time-of-day based coordinated actuated traffic signal operations. The proposed procedure uses a feature vector of optimal cycle length per time interval instead of traffic volume itself. Initial break points determined by the proposed feature vector are used in the greedy search algorithm to obtain optimal break points. By using the greedy search algorithm the number of evaluations in the search are dramatically reduced when compared to an exhaustive search or other common heuristic search methods such as a genetic algorithm. The proposed procedure was evaluated using a hypothetical network consisting of four signalized intersections and the results indicated that the proposed procedure effectively improved the performance of the coordinated actuated signal control. In addition, sensitivity analyses results on randomly varying demand conditions up to ±20% and randomly increased demand conditions up to 30% indicated that the newly developed break points were robust for such varying demand fluctuations.

A genetic algorithm-based procedure for determining optimal time-of-day break points for coordinated actuated traffic signal systems

“…Therefore, an automated process is required to achieve the optimization of the TOD timing plans for an entire 24 hours or 15 hours excluding night hours between 8 pm and 5 am. To this end, a genetic algorithm is selected as an optimizer tool instead of the greedy search algorithm adopted in the previous study by Park and Lee (2008). While Park et al (2004) used a GA (Holland 1975) optimizer with the HCM (1998) equation as its objective function, cumulative queue time produced by implementing a CORSIM microscopic simulation program, which implements a transition algorithm, was selected as a measure of effectiveness to determine optimal break points in this study.…”

“…The traffic volume data in 15 minute interval over several weekdays in the previous study by Park and Lee (2008) was again used. The optimal signal timing plan by each 15 minute time interval for the subject network was obtained by TRANSYT-7F.…”

“…Several studies reported that significant benefits were obtained by implementing optimal TOD break points (Smith et al, 2001;Park et al, 2004;Wang et al, 2005;Park and Lee, 2008). The majority of these studies can be categorized into two groups: a cluster analysis-based approach and a heuristic search algorithmbased approach.…”

“…As they pointed out, however, the HCM delay formulation-based fitness function used in the inner loop made it challenging to take progression impacts into consideration. Park and Lee (2008) developed a greedy search-based procedure for the identification of optimal TOD break points. To overcome the challenges concerning traffic operation noted in the aforementioned studies, they proposed an integration of the TRANSYT-7F as a traffic signal timing optimizer and the CORSIM (2003) simulation model as a microscopic-level evaluator to create more realistic traffic conditions that included the impacts of transitions.…”

“…A few recent studies (Smith et al, 2001;Park et al, 2004;Wang et al, 2005;Park and Lee, 2008) demonstrated that the selection of Time-of-Day (TOD) break points could significantly enhance day-to-day traffic operations. Although this idea has been adopted in the ACS Lite (Luyanda et al, 2003) algorithm, there is still a lack of standard procedure that can be easily adopted by practical traffic engineers for their day-to-day operations.…”