Coordinated approaches for port state control inspection planning

Port state control (PSC) inspections serve to guard maritime safety and the marine environment. Because port inspection resources are limited, inspection efficiency can be improved if the resources are scheduled more efficiently. Currently, ports worldwide apply a greedy inspection strategy. To improve inspection efficiency, this study proposes two coordinated inspection strategies for both liner and tramp ships, i.e., a self-coordinated port strategy and a fully coordinated central agent strategy. Extensive numerical experiments indicate that on average the self-coordinated port strategy performs 2.48% better than the greedy strategy, and the fully coordinated strategy outperforms the greedy and self-coordinated port strategies by 5.02% and 2.48%, respectively. The superiority of the two coordinated strategies is robust to different ratios of liner to tramp ships visiting the ports from 0/100 to 100/0. Therefore, the feasibility and wide applicability of the proposed coordinated strategies are validated. Specifically, when liner ships outnumber tramp ships, the fully coordinated strategy is more suitable; otherwise, both the self-coordinated port strategy and the fully coordinated strategy can be used.