Combined strip and discharge delivery of containers in heterogeneous fleets with time windows

Inland transportation of containers contributes significantly to the total cost of container intermodal transportation. For this reason, it has received a lot of attention in the last few decades. While there are many reports of attempts to solve the problem out there, the variants considered are all simpler than the form addressed in this paper. Here, we consider the container transportation problem where pick-up and delivery orders, empty and loaded containers, Discharge and Strip of heterogeneous container types with time windows, are handled with heterogeneous truck fleets that carry one or two 20ft or one 40ft chassis. Moreover, to manage the movement and reuse of empty containers, two strategies for empties, i.e. Depot-turn and Street-turn, are simultaneously allowed in the problem setting. A novel MILP model for this rich transportation problem is developed, which applies to various scenarios, even when some functions/delivery modes/types of container, are disabled. Given the complexity of this problem, exact solution of large instances is not realistic. We, therefore, suggest a novel implementation of the Genetic Algorithm (GA) tailored to this particular problem in its rich form. It differs from existing ones for VRP problems due to the nature of the problem we are considering. Numerical experiments on examples with real geographical data show that combining Discharge and Strip containers in transportation saves on cost and increases fleet utilisation.