Integrated truck and workforce scheduling to accelerate the unloading of trucks

Truck scheduling coordinates the loading and unloading processes of trucks competing for the timely processing at some terminal, e.g., a cross-docking terminal or distribution center. Existing research almost invariably assumes that the (un-)loading times of trucks are fixed. In the real-world, however, terminal managers have the additional flexibility of adapting the workforce for processing critical trucks. For instance, two instead of one worker can be assigned to jointly unload the parcels of a trailer reaching a terminal of the postal service industry onto a conveyor, or an additional forklift can support the removal of pallets from a truck in a distribution center. Thus, workforce management influences the processing times of trucks and a simultaneous planning of both tasks seems advisable. For two representative truck scheduling settings, mixed-integer models integrating workforce planning and truck scheduling are presented. Furthermore, we re-formulate the problems as interval scheduling problems and develop heuristics based on these formulations. Finally, the holistic planning models are compared with alternative models assuming a fixed workforce. Our findings reveal that integrated planning can considerably increase the performance of truck scheduling in terms of total flow time and punctuality.