A vehicle routing and scheduling problem with time windows and stochastic demand constraints

This paper presents a framework to model a real world vehicle routing and scheduling problem in which a set of customers is to be served by a number of vehicles with known capacity. The demand at each customer is stochastic and needs to be served at some regular time intervals. The problem is to select a subset of customers to be served each day to minimize the total travelling cost and estimated losses that could be incurred, subject to the vehicle capacity constraint and the time window constraint imposed by the selected customers. A selection criterion is suggested and a sequential heuristic is proposed to find a solution to the problem. Simulation results are presented to demonstrate the effectiveness of the proposed heuristic.