Vehicle routing–scheduling for waste collection in Hanoi

This paper addresses an application of operations research technique in waste collection activities in Hanoi, Vietnam. A real world vehicle routing–scheduling problem is characterized as a loading and unloading problem complicated by several time windows and inter-arrival time constraints at each customer point. We formulate the problem into a mixed-integer program and propose a heuristic procedure consisting of construction and improvement phases. The route construction routine is a modification of Solomon's I1 heuristic, while the improvement phase combines the power of Or-opt and 2-opt* together. Compared with the current practice, our solution can achieve an improvement in both total cost and the number of vehicles utilized.