Impact scenario models for probabilistic risk-based design for ship-ship collision

A number of authors have proposed probabilistic risk based ship design for ship-ship collision, conditional to the local trading area of a vessel. The probability of collision and consequences are determined based on the traffic conditions in which a vessel is expected to operate. This paper investigates the adequacy of currently available models for impact scenarios, i.e. models linking the traffic conditions to the conditions at the moment of collision. An exploratory statistical model is presented to establish such a link. A probabilistic risk based design case study is performed for a fleet of RoPax vessels trading on a specified route in the Gulf of Finland. The available impact scenario models from the literature are compared with the developed probabilistic evasive maneuvering model. The results show that the impact scenario models have a very significant influence to the calculated hull breach probabilities. No well-justified impact scenario models are presently available and also the presented probabilistic evasive maneuvering model is burdened with uncertainty. Hence, to move toward a probabilistic risk based ship design paradigm for ship-ship collision in a local trading area, more focus and research is needed to establish a credible link.