Proposed methodology for designing the signal change interval

Abstract

Determination of change interval (yellow interval) is a crucial step in signal timing design. The main purpose of this study is to design the yellow interval timing which satisfies the driver behavior. The time taken for the last entering vehicle to reach the stopline from the onset of yellow was termed as the yellow interval demand. The yellow interval demand was found to have significant relationship with vehicle supply, stated as the number of vehicles present near the stopline for the first 5sec. From the onset of yellow. A model relating the 85th percentile yellow interval demand to the vehicle supply was built. The model was found to be safe and efficient and can be used to set the yellow interval timing at signalized intersections.

Existing yellow interval timing were evaluated in relation to violations and rear-end conflicts. The existing timing was found to be significantly less than the 85th percentile yellow interval demand and the yellow obtained by the ITE method. A 10 to 30% increase in the existing yellow interval timing will significantly decrease the run-red violations and thereby reduce the risk of right-angled accidents.

The developed 85th percentile yellow demand model was compared with the ITE developed yellow interval timing. The ITE method gives little conservative estimate of yellow timing compared to the developed model, but it was found to give incorrect yellow interval timings for approaches with low approach speeds.