Integrating the ambulance dispatching and relocation problems to maximize system's preparedness

In the Emergency Medical Service (EMS) context, the decision-making process plays a very important role since some decisions highly impact patients' health. This work focuses on the operational level by solving the dispatching and relocation ambulance problems. Dispatching decisions assign ambulances to emergencies and the relocation problem decides on the base to which available ambulances should be (re)assigned. To improve effectiveness and efficiency in the EMS response, integrated optimization approaches are proposed: a mathematical model and a pilot method heuristic. The aim is to maximize system's coverage using a time-preparedness measure allowing relocations to any base. Experiments are performed using EMS data from Lisbon, Portugal, where solving these problems is still a handmade task. The optimization approaches are adapted to compare the proposed strategy with the current Portuguese EMS strategy which dispatches the closest available ambulance for each emergency and relocates ambulances to their home bases. Results highlight the potential of the mathematical model and of the proposed strategy to be applied in real-time contexts since key performance indicators (KPIs) are, in general, better than the ones obtained through the heuristic and the current Portuguese EMS strategy. The heuristic should be used when more emergencies occur in the same time period since a solution can be obtained almost immediately in contrast to the MIP usage. (C) 2019 Elsevier B.V. All rights reserved.