The Ambulance Relocation and Dispatching Problem

Emergency medical services (EMS) generally deal with two real-time decisions: ambulance dispatching and relocation. Dispatching consists in selecting which ambulance to send to an emergency call, while relocation consists in determining how to modify the location of available ambulances throughout the day in response to changes in the state of the system. Although they have been mostly considered separately both in the literature and among practitioners, dispatching and relocation decisions are closely related. Considering them simultaneously could help improve the service level with lower relocation efforts. In this study, we address the Ambulance Relocation and Dispatching Problem (ARDP). The ARDP determines the location of each available ambulance as well as a dispatching policy, aiming at minimizing the expected response time along with relocation efforts. The ARDP is formulated as a linear programming model. To solve reallife instances, a matheuristic decomposition approach is developed exploiting the division of the territory into subregions. Results show the benefits of considering dispatching and relocation decisions simultaneously, and their impact on each other. Moreover, on a set of instances representative of a real application, the proposed approach has proven to be an effective tool to provide good quality solutions.