Dispatch and conflict-free routing of capacitated vehicles with storage stack allocation.

Congested traffic networks impose great difficulties upon scheduling material transportation in industrial settings. Dispatching decisions become complex when, in addition to conflict-free routes, storage location must also be considered. The present paper integrates the dispatch and conflict-free routing of capacitated vehicles with the storage allocation problem and proposes a heuristic approach for minimising the total completion time of box pickup, delivery and relocation requests in a warehouse environment. The developed formulation models a warehouse setting in which boxes are stored in stacks and considers different forward and reverse speeds for the vehicles, real-world movement restrictions and a LIFO loading policy. The proposed approach is evaluated using two different metaheuristics and the results are compared against existing schedules prepared by an industry partner. Experimental results demonstrate the effectiveness of the proposed method for large-scale instances and highlight how improved storage allocation decisions can reduce service times.