Re-arrangement of traffic signal timings by cyclic vehicle queue profile

Abstract

Traffic signal timing is one of the interesting subjects that have been considered by transportation engineers and researchers. In spite of many technological and innovative solutions, fixed time controlling approach is still applying widely in the world. Signal timings are pre-defined in fixed time control and many programs can be applied for time of day. But in some cases, these programs can be insufficient for the demands occurred by variations in traffic flows. Assigned signal timings can be more or less than that of the timings required. Thus, vehicle delays can increase because of these irregular assignments. In this study, cyclic vehicle queue profile is considered for re-arrangement of signal timings at isolated intersections. Observations were made at sample intersections in Denizli, Turkey. 5 isolated intersections were considered and cyclic based observations were made for peak and off-peak periods. Traffic compositions were taken into account in the observations, cyclic traffic flow profile and remaining number of vehicles for each cycle was determined. Based on these observations, average remaining queue, average discharging time of queue, remaining phase time were measured. Present cycle times were modified depending on remaining phase times and new cycle times were calculated. The average delay times of the traffic flows for new cycle times were calculated with Akcelik delay formula. In addition, they were compared to that of existing cycle time. The results showed that at least 30% improvements can be obtained by re-arrangement of signal timings considering cyclic vehicle queue profile.