A case study of optimal ambulance location problems

Aiming at improving the efficiency and reliability of ambulance service, several location models for ambulance stations have been proposed in the operations research literature. Well-known approaches to this problem are coverage model and median model. Coverage model looks for the location to maximize the (deterministic or probabilistic) covered demand of ambulance calls. Hence this model can be thought of reliability oriented model. On the other hand in median model the objective is to minimize the total traveling distance of the ambulances from the station to the scene of call. This model gives more weight to the efficiency of ambulance operation. This paper gives a comparison of those optimization models through actual patient call data from Tokyo metropolitan area to show the characteristics of each model and investigate a possibility of improvement in ambulance service. In the next section we introduce two well-known approaches to ambulance location problem, coverage model and median model. In Sec. 3 we apply these models to patient call data from Tokyo and compare the actual location and optimal solution. The result shows us the optimal solution can achieve improvement in both models, and suggests the possibility of more efficient and reliable location.