Ambulance location and relocation models in a crisis

This article deals with the relocation of ambulance vehicles from their origin location (i.e., position before a crisis occurs) to a crisis area and to undercovered areas (i.e., no ambulance vehicle is available for a potential emergency in a given region). Support for a crisis area can lead to insufficient coverage of other emergency patients in other regions, so decision makers need assistance with useful relocation information, including the relocation of vehicles to the crisis area and to undercovered areas. As optimization criteria, this study considers two objectives: undercoverage (i.e., unsupported demand) and the total time needed to get to the crisis area with all vehicles. A proposed model aims to minimize the time required for the vehicle relocation process and avoid relocation mistakes (e.g., sending a vehicle to support the crisis area when it would be better to leave it at its current location). Devising the relocation plan consists of three phases. First, a location model allocates all available vehicles to potential vehicle locations (positioning vehicles before the crisis occurs). Second, the same location model allocates the remaining vehicles in the case of a crisis (all vehicles not needed to manage the crisis). Third, the relocation model (phase three) moves vehicles from their position before the crisis occurs (phase one) to their position during the crisis (phase two).