Inventory routing and dynamic redistribution of relief goods in post-disaster operations

Abstract

The distribution and redistribution of relief goods among people in need is an essential operation in the post-disaster environment. This paper presents a mathematical model to schedule these operations. The need for redistribution stems from having surplus inventories in some locations and severe shortages in other areas, as new information on the losses becomes available. The proposed model represents a particular inventory routing problem, which includes a vehicle routing problem with pickup and delivery in the first period, and a network flow problem for each of the following periods. As a result, it can produce itineraries and loading plans for the fleet in each period when it is solved in a rolling horizon manner. The objective function is to minimize the sum of deprivation costs, operating costs, and costs of breaching the previous decisions. The fairness in the distribution of relief goods is embedded in the model. The distinction between the characteristics of relief goods further complicates the model. Due to the difficulty of solving the routing problems, a specialized simulated annealing algorithm with a novel solution encoding is developed. In each iteration of the proposed algorithm, the routing decisions are made using the simulated annealing algorithm. Then, the resulting subproblem is solved using CPLEX to evaluate the objective function. Parameter tuning of the algorithm is done in a systematic fashion. Finally, the proposed model and solution algorithm has been tested on a set of randomly generated problems and two instances of a real-world case study. Analysis of the numerical results shows that the proposed algorithm can produce high-quality solutions in a reasonable time. It is shown that redistribution can significantly improve the performance of the relief operation.