On the probabilistic assessment of ship collisions in the open sea

The article presents an analytical model for assessing the probability of collision of vessels in the open sea. The model is based on the approaches of classical probability theory, when a collision is a result of a sequential occurrence of a number of random events occurring during the development of the “approach – encounter – collision” scheme. Each of these events is characterized by a set of continuous random variables, the distribution laws and parameters of which can be selected depending on specific navigation conditions. The critical element of the model is the possible transition from the situation of meeting of ships to their collision, determined by the casual probability. With this approach, the scheme “approach – meeting – collision” is one of the variants of the scheme “danger – real danger – realized danger”, applied in the procedures of risk assessment and management. In this case, the situation of meeting of two ships is a real danger and is considered as a potentially dangerous situation according to the terminology of formal safety assessment adopted in navigation during risk analysis and assessment. The model allows obtaining both single and interval estimates of the collision probability. The model can be used to assess the level of navigation safety for specific navigation conditions and shipping characteristics by changing the input data: the type and parameters of the functions of the density of distribution of courses and speeds of vessels, the size of the analyzed water area, the parameters of the safety criteria used in the model. The presented model can be useful in assessing the risks of oil spills arising from possible collisions of vessels, which is an obligatory element in the formation of a system for preventing and responding emergency spills of oil and oil products at sea.