Abstract-Vessel traffic is changing due to changing transport demands, larger ships and new use of sea space, such as windmill parks. This may have an effect on the risks at sea. This study uses ship state information provided by AIS-messages to analyse the traffic on the North Sea. From the ship-state information conflict situations are selected, i.e., situations where the ships need to manoeuvre to avoid collision. In addition, situations of near-miss collisions are calculated. It was found that complex conflicts lead to more near-misses. It was also found that near-misses are not spread evenly over the sea but are concentrated in a number of specific locations. These findings may be important for the design of route structures for ships, as well as for investigations into methods to resolve complex conflict situations.
In shipping, collision risk is a serious safety threat. Risk probability estimations used for policymaking are derived from traffic density statistics, largely ignoring the decision-making process on board. Conflict detection and resolution on board is done using rather rudimentary but effective mental-model-based techniques. In this article, the authors analyse traffic using the concept of complexity. The actual geometry of the ships involved in the conflict defines how well the crews on board can resolve the conflict. This geometry is transformed into a complexity value. A reliable detection and resolution of conflicts by human operators decreases in certain situations. A previous study has shown that when complexity reaches a threshold, the risk of a near miss increases significantly. In this study, three actual collisions at open sea are analysed. It will be shown that situations of high complexity, which decreases human reliability, can be predicted well in advance, allowing for a safe resolution. The technique also allows for alerting and a decision support for the crew.
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