The rules of this section (Section II) apply only to vessels in sight of one another; in restricted visibility, Rule 19 applies instead.
Rule 11 - Application
The rules of this section apply to vessels in sight of one another.
Rule 12 - Sailing vessels
When two sailing vessels are approaching so as to involve risk of collision:
- If each has the wind on a different side, the vessel with the wind on the port side keeps out of the way.
- If both have the wind on the same side, the vessel that is to windward keeps out of the way of the vessel to leeward.
- If a vessel with the wind on the port side sees a vessel to windward and cannot determine with certainty which side the other has the wind on, she keeps out of the way.
(Windward side means the side opposite to that on which the mainsail is carried, or, for a square-rigged vessel, opposite to the largest fore-and-aft sail.)
Rule 13 - Overtaking
Notwithstanding anything in Sections I and II, any vessel overtaking another shall keep out of the way of the vessel being overtaken. A vessel is deemed to be overtaking when coming up from a direction more than 22.5 degrees abaft the other's beam — that is, a position from which at night she would see only the other's sternlight, not her sidelights. When in doubt, a vessel shall assume she is overtaking and act accordingly. A subsequent change in bearing does not make the overtaking vessel a crossing vessel, nor relieve her of the duty to keep clear until finally past and clear.
Rule 14 - Head-on situation
When two power-driven vessels are meeting on reciprocal or nearly reciprocal courses so as to involve risk of collision, each shall alter course to starboard so that each passes on the other's port side. This situation exists when a vessel sees the other ahead or nearly ahead and, by night, sees her masthead lights in line or nearly in line and/or both sidelights, or, by day, observes the corresponding aspect. When in doubt, a vessel shall assume the situation exists and act accordingly.
Rule 13's overtaking duty overrides every other rule in this Part - that is why it opens with "notwithstanding".
