Inventory Routing Problem Routing and Scheduling Approach with the Objective of Slack Maximization

This paper extends the study of the inventory routing problem with slack maximization (IRPSM), which addresses the distribution of relief supplies in response to a sudden emergency. Compared with the classical routing problem, the objective of IRPSM is to maximize the slack in inventory, defined as the difference between the arrival time of new deliveries and the estimated time that the inventory will run out, rather than to minimize the total cost of delivery. Previous researchers have proposed a two-stage (scheduling and routing) solution framework, which was proved to be efficient to solve this problem. On the basis of this two-stage framework, this study developed an initial heuristic at the routing stage. With full realization of the limitations of the initial heuristic, an improved heuristic was proposed to prevent trapping of the solution at a local optimal condition. Compared with several existing solution algorithms, the results of a case study showed the effectiveness of the proposed heuristics.