A system for dispatching vehicles in a public transportation network may include a passenger monitoring system configured to monitor a number of passengers waiting at a stop in the transportation network, a vehicle dispatching system and a processing device. The processing device may apply a Markov Decision Process (MDP) model to determine a score for each of multiple decision rules, in which each score represents a number of passengers waiting at the stop at the end of a time interval, and use the scores to identify a number of waiting passengers at which a reserve vehicle should be dispatched. The system may use information received from the passenger monitoring system to determine a state at an instant of time, and determine whether a reserve vehicle should be dispatched based on the MDP model and cause the vehicle dispatch system to dispatch a reserve vehicle or retain a nominal vehicle.