Modelling the Effects of Pedestrians on Intersection Capacity and Delay with Actuated Signal Control

The current procedure in the Highway Capacity Manual 2000 for analyzing actuated signalized intersections treats pedestrian crossing and timing in a fixed manner, which can lead to erroneous results in capacity and delay calculations. This paper introduces a new model that remedies such a shortcoming in the current procedure. The model takes into account the stochastic nature of pedestrian crossings and their effects. The model consists of calculations of the probability of having a pedestrian call in a cycle, and the corresponding capacities and delays for the traffic movements. The model was compared with the SimTraffic simulation model based on a generic intersection with semi-actuated signal control, and was found to produce consistent delay results between the two models. Using the proposed model, the effects of pedestrians on intersection capacity and delay were analyzed. Depending on the pedestrian volume conditions, the current Highway Capacity Manual procedure could produce results of significant errors, with the largest errors possibly occurring under low pedestrian volume conditions. For the vehicle movement that is concurrent with the pedestrian movement, it generally receives more green time with the increase of pedestrian volumes; therefore, higher capacity and lower delay would result. Consequently, the other movements would experience capacity reduction and delay increase. One interesting finding from the study was that the concurrent vehicle movement can achieve a higher capacity with a shorter cycle length with the same pedestrian volumes.