Disruption Management: The Vessel Schedule Recovery Problem (VSRP)

The Vessel Schedule Recovery Problem (VSRP) is the problem where the proforma schedule of vessels needs to be modified because of a delay. This problem is still scarcely researched and therefore a lot of improvements can be made. As liner shipping companies need to make decisions fast, results must be generated such that they can be used in real-life decision making. A MIP formulation with an underlying time-space network as stated by Brouer et al. (2013) is used to test how the formulation reacts when varying the duration of a shift, the number of vessels and port calls. As the original formulation is only able to handle disruptions by means of changing the speed of a vessel, omitting port calls and swapping port calls, the model is extended such that it can capture the cut-and-run policy as well. This policy enables vessels to leave their port call earlier, before finishing it. The computation times of our implementation react strongly when increasing the number of port calls, however it is more robust when increasing the number of vessels. As there is a trade-off between between cost reduction and time when the duration of the shift is decreased, we advise to not take this duration too small. In general our extension gives on average a relative large cost reduction in case the number of vessels is large.