Evacuation Planning Problems with Intermediate Storage

An evacuation planning problem gives a plan on existing road network for disaster management that attempts to send all evacuees from the dangerous zone to the safer zone efficiently. The network flow problems provide important tools for modeling the evacuation tasks. The problems based on the model with flow conservation constraint, that permits an evacuee to be taken out of the disastrous zone only if it can be sent into the safe zone, have been extensively studied for various evacuation scenarios. In this paper, we study dynamic flow problems based on weak flow conservation constraints that allow for an intermediate node to serve as a temporary shelter also with three distinct objectives and propose efficient solution procedures. The first is to maximize the number of evacuees into the safe zones in priority order within the specified time horizon. The second is to achieve the first objective at every time point within the time horizon. And, the third is to fulfill the demand (number of evacuees) at each of the safe zones in minimum possible time horizon in priority order.