For given circumstances (i.e., a collision situation at sea), a decision support system should help the operator to choose a proper maneuver, teach him/her good habits, and enhance his/her general intuition on how to behave in similar situations in the future. By taking into account certain boundaries of the maneuvering region, along with information on navigation obstacles and other moving ships, the problem of avoiding collisions at sea is reduced to a dynamic optimization task with static

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... dynamic constraints. In this paper a modied version of the EP/N (Evolutionary Planner/Navigator) [13] has been used as a major component of a such decision support system. #EP/N++ computes a safe-optimum path of a ship in a given static and dynamic environment; on the basis of this algorithm, a safe trajectory of the ship in a collision situation is determined. The introduction of a time parameter, together with time-varying constraints representing movable ships, are the main features of the new system. Sample results of ship trajectories obtained for typical navigation situations are presented in the paper.