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.
