Ship collisions: Types of aberrancy, collision models and calibration challenges

Ship collisions with bridges and other fixed infrastructure can be attributed to various types of ab- errancy, i.e. various causes for a vessel to deviate from its intended route and various resulting col- lision trajectories. Holistic approaches aim to create a simple model of aberrant behaviour, whereas. scenario-based approaches create an array of deviation trajectories. Regardless of the approach, it is both a philosophical and a practical challenge to calibrate the models, as observations of aberrant vessels are too rare and thus often insufficient for calibration. As a consequence, statistics from non- aberrant movements combined with engineering judgment are often used instead. This paper gives an overview of the different methodologies, their strengths and challenges.