Platooning of arrivals has a significant effect on traffic signal performance and must be considered in estimating delay. The highway capacity manual (hcm) method, which is based on arrival types, is not accurate because the progression adjustment factors vary in large steps. Another estimation method for pretimed signals is based on the step arrival flow approximation, which assumes different averagearrival rates during the red and green periods of the cycle. The model requires only one easily measurable parameter--the proportion ofarrivals during the red period. The delay estimates obtained using this method were in good agreement with cycle-by-cycle delay observations, except for cases in which the arrival rate profile was not symmetrical inside the red period. Compared with the hcm progression adjustment factors, the step arrival rate model generally predicts a stronger effect of platooning on uniform delay. The effect of platooning on overflow delay is not significant, however. Therefore, no adjustment factors should be used for the overflow delay component. This paper appears in transportation research record no. 1287, Trafficflow, capacity, roadway lighting, and urban traffic systems 1990.
Abstract