Re-marshalling in automated container yards with terminal appointment systems

Abstract

As a result of scarce land availability, growing competition and throughput, container terminals are increasing the stacking height of yard blocks to fulfil the demand for storage area. Due to inadequate retrieval information at initial stacking, shuffle moves can occur during retrieval operations as containers may be stacked in a sequence which does not correspond to the actual retrieval sequence. Automated stacking cranes can perform re-marshalling during periods of no crane workload to shift unproductive moves during retrieval operations to phases of idle time. Terminal appointment systems (TAS) enhance landside sequence information when external trucks (XT) announce their arrival beforehand. Under these circumstances, it is beneficial for terminal planers to understand the effects of using re-marshalling in combination with TAS. The purpose of this work is to introduce an online rule-based solution method for the re-marshalling problem with and without TAS. A simulation model of a fully operating yard block is used as environment to compare the proposed method with a benchmark heuristic from the literature. All tests are conducted for single and multiple Rail-Mounted-Gantry-Crane systems with different yard block sizes. It is also shown that solving the re-marshalling problem with the proposed algorithm generates results that reduce shuffle moves by 30% on average and by up to 50% in the best case, while always performing better in the worst case in comparison with not performing re-marshalling. Afterwards, influences on the method of selected TAS parameters are evaluated numerically. Results show that imprecise XT arrival information, not deviating above a certain threshold, significantly contribute to reducing congestion by mitigating XT waiting time and levelling arrival peaks. These benefits can be achieved without imposing restrictions on the arrival schedule preferred by XT companies.