Allocation and reallocation of ambulances to casualty clusters in a disaster relief operation

In this paper, we consider ambulance allocation and reallocation models for a post-disaster relief operation. The initial focus is on allocating the correct number of ambulances to each cluster at the beginning of the rescue process. We formulate a deterministic model which depicts how a cluster grows after a disaster strikes. Based on the model and given a number of ambulances, we develop methods to calculate critical time measures, e.g., the completion time for each cluster. Then we present two iterative procedures to optimize the makespan and the weighted total flow time, respectively. The second problem analyzes the ambulance reallocation problem on the basis of a discrete time policy. The benefits of redistribution include providing service to new clusters and fully utilizing ambulances. We consider the objective of minimizing the makespan. A complication is that the distance between clusters needs to be factored in when making an ambulance reallocation decision. Our model permits consideration of the travel distance between clusters. Results of our allocation method are illustrated via a case study, which is based on an earthquake scenario in Northridge, CA.