Modelling passenger flows at a transport interchange using Petri Nets

Modelling passenger flows within a transport interchange is a compromise between computational speed and accuracy, especially if the model is to be embedded within an optimization procedure for managing the effects of disrupted traffic. Petri nets offer the possibility of the standardized representation of a concurrent dynamic system. Such a representation consists of a network formed by places that are linked together by arcs and transitions, and tokens that move around in this network. Using coloured Petri nets (CPNs) allows information to be associated with each token, such as the number of passengers represented by the token, the destinations of subgroups of those passengers and data related to measures such as accumulated passenger transit times. Practicalities such as the variation of walking speeds between passengers and the restricted capacity of features of the interchange infrastructure, such as escalators, can also be incorporated. Furthermore, the model is capable of being extended to represent the transport services themselves, at least within a reasonable area outside the interchange.