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. (C) 2019 Elsevier B.V. All rights reserved.