Management of housekeeping operations at an automotive maritime terminal

The yard management of an automotive maritime terminal often requires the consolidation of the parking areas, via reallocation of cars. Even though internal moves should be kept to the minimum, being the cars extremely fragile objects, reallocations may become unavoidable. Actually they are needed either to speed up the export process, grouping the cars on the basis of the stowage plan of outgoing vessels, or to de-fragment some yard area in view of the next import flows [1]. The internal moves are performed by the drivers: they transfer the cars from an origin point to a destination point; then they are taken back to pick-up the next car by shuttle buses, of given capacity. Assuming to be given a set of cars to be reallocated, together with their initial and final positions in the yard, the main interrelated decisions to be taken in the optimal way concern: i) the number of drivers and shuttle vehicles to be allocated; ii) the sequence of cars to be moved by each driver; iii) the route of each shuttle vehicle. The (conflicting) objectives to pursue are to complete the operations as soon as possible, while minimizing the workforce assigned to the process. The main side constraints take into account the labor agreements on the working shifts of the drivers. Of course the problem is not separable. Nevertheless we tackle the problem by a decomposition approach, with the aim of designing a fast and efficient heuristic procedure. Therefore we split the problem in two sub-problems to be solved in sequence: first construct the route of each driver; then construct the route of each shuttle vehicle. The first sub-problem is formulated as a Multiple Travelling Salesman Problem, while the second one reduces to a Dial-a-Ride Problem with time Windows [2]. We discuss on some preliminary numerical results