Preventing environmental disasters from grounding accidents: A case study of tugboat positioning along the Norwegian coast

An important task of operators in Norwegian vessel traffic services (VTS) centres is to cleverly position tugboats before potential vessel distress calls. Here, we formulate a non-linear binary-integer program, integrated in a receding horizon control algorithm that minimises the expected cost of grounding accidents by positioning tugboats optimally under uncertainty about vessel incidents and environmental conditions. Linearisations of the model lead to easy-to-compute bounds on the optimal value. Numerical experiments with real-world data demonstrate significant reduction in the expected cost, suggesting that the model can be used as a decision-support tool at VTS centres.