Realistic strategies for dynamic ambulance relocation

The location of vehicles is a decision of significant importance for Emergency Medical Services. However, the delivery of emergency care is dynamic in nature and the initial locations of ambulances may quickly prove inadequate for maintaining coverage as they are dispatched to attend to patients. Rather than increasing the size of the fleet of vehicles, research has focused on the dynamic relocation of ambulances. This approach allows available vehicles to move to sites beyond their usual bases, maintaining an appropriate level of service. The scientific community has proposed a wide variety of ambulance relocation strategies using different methodological approaches. However, most of the strategies have not been implemented by real life Emergency Medical Services. This study proposes a scenario-based dynamic relocation algorithm that incorporates the following realistic aspects: it allows ambulances to start and end their work shift at their usual base, regardless of the number of relocations performed; a methodology based on Geographic Information Systems is developed to determine the positions of ambulances en route in order to be able to assign these ambulances to emergencies. In addition, the importance of relocating ambulances at different times of the day is studied. The proposed algorithm is validated by applying it to a real life case, in the city of Valencia, Spain, where the importance of considering these realistic aspects is shown.