Abstract
When the difficulties of collision avoidance in a restricted water is discussed, it must be taken into account that the collision avoidance actions are limited due to the existence of marine obstacles in the vicinity of own ship and target ships. If a mariner can choose any action from a two dimensional action space of collision avoidance which is composed of an orthogonal axis of course-change and speed-reduction, it is thought that the encountering situation gives a minimum difficulty. On the contrary, if only limited action can be taken, the mariner must feel much more difficulty for the encountering situation. Such difficult situations can be found in the cases of encountering in restricted water such as inside a harbour, near a marine construction site and in a narrow waterway. On the basis of the above consideration, in the present paper, a model is proposed to estimate the difficulties of collision avoidance in a restricted water by taking the remainder of the action space excluding obliged or limited action space into account.
