Trailer Scheduling at Multi-Door Cross-Docks

Cross-docks are transshipment facilities used in logistics to consolidate freight by destination.  This research addresses the cross-dock scheduling problem for a multi-door facility where inbound trailer arrival times are variable, products are interchangeable, and the objective is to minimize the makespan and the tardiness of outbound trailers that are impacted by a nonlinear penalty function.  A mixed-integer programming model is developed to include these features and others such as soft departure deadlines.  This problem is well-known to be NP-hard, so heuristics are needed to solve larger problems.  A new solution approach is proposed that uses a construction heuristic to produce good-quality starting solutions for a population-based simulated annealing metaheuristic.  The results of this model have been animated so that practitioners with no background in the technical aspects of the model or algorithm can vary parameters and watch the impact of the optimal solution on truck arrival and departures.