The dynamic redeployment coverage location model

Demand for ambulances is known to fluctuate spatially and temporally by day of the week and time of day. Faced with fluctuating demand during the day, emergency medical systems (EMS) managers utilize redeployment strategies to meet demand. Such shifting of personnel, although better able to cover a region with fluctuating demand, can cause fatigue amongst ambulance crew members. Considering these phenomena, we extend the dynamic available coverage location model to be driven by two objectives: (1) Minimize the number of ambulances, and (2) Minimize the number of redeployments for a given fleet during a given shift. We develop a heuristic search algorithm and present the comparative statistics using real data from an urban EMS agency. Our findings suggest that EMS managers can effectively balance a need for additional ambulances with those redeployments required to meet variable demand patterns.