Hardness of flow time minimization in a crossdock with a single door and asymmetric handover relations

We study the problem of sequencing trucks subject to handover relations. The objective is to minimize the total time pallets spend at the terminal. It has been shown that the problem is strongly NP-hard for two doors or with unrelated (un)loading durations. We show that it is strongly NP-hard even for a single door and (un)loading durations of trucks being proportional to the number of pallets (un)loaded. (c) 2023 Elsevier B.V. All rights reserved.