Toward optimal sketch-level transit service plans

A model and methodology are presented for preparing optimal sketch-level service plans for passenger systems that operate vehicles, singly or in multiple units, over a fixed network on a fixed schedule. The model uses transshipment equations to develop optimal vehicle flows, by link and time period, in response to passenger flows, service frequency requirements, line segment capacities, system fleet size, and storage node capacities. Frequency variables are used to represent the flows which reduces the need for integer variables and reduces solution times. It also makes possible the use of the model when many service alternatives are to be evaluated in a short period of time. In addition, the model’s explicit treatment of equipment balancing results in an easy-to-understand solution with cost and resource estimates that can be traced clearly to the underlying vehicle movements.