Abstract
In the present study, a vessel collision model between two ships based on NDM model was developed by combined approach of fault tree, event tree and matrix description, which illustrates the navigator's situation (observation, cognition, planning and action),in order to determine success or failure of collision avoidance. Applying a frequency index of human error to this collision model resulted in the same order of magnitude as conventional geometric models. This result suggests that the model based on NDM model has an accuracy equivalent to geometric models. Therefore, the failure probability of collision avoidance at vessel's encounter can be derived by only employing the frequency index of human error for the vessel collision model. Subsequently, for the purpose of confirming the feasibility of the evaluation of risk control options by use of the model based on NDM model, we examined the effect of the five risk control options for vessel collision, which are applicable to general vessels. The examination implied that "boarding (embarkation of) a coast pilot" and "on-board VHF radio telephone" are the most effective risk control options. Furthermore, these two options are also effective for vessels which are not required to be equipped with by legislations,since this model does not depend on the size of vessels. This paper shows that the vessel collision avoidance model based on NDM model is useful not only to discern the impact of vessel collision caused by human error but also to assess the effect of risk control options.
