A vessel is considered overtaking when she can see which light(s) of a vessel ahead?

A vessel is considered to be overtaking another vessel when it can see only the sternlight of that other vessel. This scenario indicates that the overtaking vessel is positioned behind and to the sides of the vessel ahead, thus unable to see its sidelights.

According to the Navigation Rules, a vessel that is overtaking another is defined as being in a position where, when looking forward from the overtaking vessel, the only light visible from the other vessel is the sternlight. If the overtaking vessel could see the sidelights (the red and green lights) of the other vessel, it would not be considered overtaking but rather crossing or meeting, as the overtaken vessel would then be visible to the overtaking vessel’s view in a way that indicates a potential need to yield to the other vessel.

This understanding is critical for maintaining proper navigation practices and ensuring safety at sea. Thus, recognizing the visibility of only the sternlight keeps in line with the rules governing vessel behavior in overtaking scenarios.