Ship stability-related effects on a critical distance of collision evasive action

Numerous solutions have been developed to facilitate collision avoidance process and safety assessment at sea. These are based on proximity indicators, defined as an area around own ship that is to be kept clear from other vessels. One of such indicators is referred to as a ship’s domain. Therein, a domain violation is recognized as an unsafe operation and needs to be avoided. However, the concept of a ship’s domain does not originate from the collision avoidance field, rather it is rooted in the field of waterway’s capacity assessment. Thus, the problem of transferability of the concept from one field to another emerges, resulting in the need for proper evaluation of the domain’s characteristics that are suitable for the field of collision avoidance. Therein such features as ship’s manoeuvrability and stability conditions seem to be indispensable since those affect the
minimum area required for a ship to perform collision evasive manoeuvre.

The aim of the paper is three-fold. First, it sketches the minimum requirement for an area around own ship that needs to be kept free from other objects to ensure the safe passage of the ship. Second, it discusses the significance of stability - related effects on this area. Third, it is to provoke a discussion on the subject.

To this end extensive literature review is performed summarizing available domains, then to determine the safe area around own ship, a 6DoF ship motion model (LaiDyn) is adopted, along with encounter simulator.