A multi-ship following model for icebreaker convoy operations in ice-covered waters

Abstract

Most vessels cannot safely sail in areas with sea ice. In the Northern Baltic Sea area, the presence of sea ice often requires icebreaking ships to open up ice-covered areas so merchant vessels can proceed to their destinations. In this environment there is an increasing number of ships. With growing transport volumes in sea ice environments, icebreaker operations such as convoys have become increasingly important to ensure navigation safety. This paper proposes a model of multi-ship following for icebreaker convoy operations in continuous icebreaking conditions, using modelling principles from earlier proposed car following models combined with considerations of safe distance and safe speed in ship convoy operations in ice conditions. The model parameters are calibrated with empirical data from actual icebreaker convoy operations, using data from the Automatic Identification System (AIS) and sea ice model data. The model determines ice resistance according to ice thickness, type, and bending strength, and the main dimensions of the icebreaker leading the convoy. The maximum safe navigable speed is used to assess the following ships’ ability to sail in sea ice. The multi-ship following simulation results were found to be in good agreement with empirical data. The new proposed model can provide a theoretical reference for icebreaker convoy operations, can have practical use in ship simulators to improve training, and could be useful for traffic modelling and planning purposes.