Integrated Outbound Vehicle Routing and Scheduling Problem at a Multi-Door Cross-Dock Terminal

Abstract

This paper presents a newly formulated model for the integrated vehicle routing and scheduling problem on the outbound side of a multi-door cross-dock terminal (or system or center) operating in post-distribution mode involving multiple product types, and develops a new decomposition-based hybrid optimization method for its solution. The hybrid optimization method solves the problem iteratively. In each iteration, a solution of the outbound vehicle scheduling sub-problem is first obtained and the vehicle routing sub-problem with time windows is then subsequently solved. The hybrid optimization method makes use of an iterated local search (ILS) algorithm for solving the vehicle routing sub-problem with time windows and a greedy search for solving the sub-problem of outbound vehicle scheduling involving the assignment and sequencing of vehicles at each dock-door, and determining the vehicle departure times from the cross-dock. The proposed solution was shown capable of finding the optimal solution identified by the enumeration method for two small datasets and further tested with 20 newly generated moderate-to-large data sets. Based on the results obtained, managerial insights are highlighted.