Intermodal transit system coordination with dynamic vehicle dispatching

In most urban areas where transit demand is spread widely, passengers may be served by an intermodal transit system, consisting of a rail transit line (or a bus rapid transit route) and a numbers of feeder routes connecting at different transfer stations. In such a system, passengers may need one or more transfers to complete their journey. Therefore, scheduling vehicles operating in the system with special attention to reduce transfer time can contribute significantly service quality improvements. In this study two models, one for coordination of a general intermodal. transit system and another for dynamic dispatching of vehicles on coordinated routes, are presented. Schedule synchronization may significantly reduce transfer delays at transfer stations where various routes interconnect. Since vehicle arrivals are stochastic, slack time allowances in vehicle schedules may be desirable to reduce the probability of missed connections. An objective total cost function, including supplier and user costs, are formulated for optimizing the coordination of a general intermodal. transit network. A four-stage procedure is developed for determining the optimal coordination status among routes at every transfer station. Considering stochastic feeder vehicle arrivals at transfer stations, the slack times of coordinated routes are optimized, by balancing the savings from transfer delays and additional cost from slack delays and operating costs. The model is used to optimize the coordination of an intermodal transit network under different demand situations, while the impact of various factors (e.g., demand, standard deviation of vehicle arrival times, etc) on coordination is examined. For dynamic vehicle dispatching control, the decision whether a coordinated vehicle should be held to wait for late vehicles, can be made by minimizing the dynamic total cost objective function formulated in this study. The time-varied objective total cost function, including supplier and user costs, is developed for determining the optimal dynamic dispatching times of all coordinated vehicles at transfer stations. A numerical example is provided to demonstrate the application of the dynamic dispatching model, while vehicle holding times are optimized and dispatching costs are analyzed under different delay variations of coordinated vehicles arrival times