Classifying Ship Encounters to Monitor Traffic Safety on the North Sea from AIS Data

In studies for the Dutch Ministry of Infrastructure and the Environment, MARIN has developed methods to classify ship encounters on the North Sea from AIS data. The methods use the Distance at Closest Point of Approach (DCPA), Time to Closest Point of Approach (TCPA), and an estimate of ship domains, to determine for each crossing, head-on, and overtaking encounter, whether these follow abnormal patterns. On august 1 2013, the route structure on the North Sea, was rearranged to improve safety and efficiency. The encounter classification methods were applied to two years of AIS data. Heat maps of encounters show how the junctions have shifted. For these junctions, the numbers of encounters were compared. This paper discusses the methods to classify encounters, and the results of the comparison of the route structures. The results show a decrease of the number of exceptional head-on and crossing encounters in the new route structure.