Overtaking, head-on and crossing: identify before deciding

Two bows on a sheet can suggest an encounter while leaving legal conditions unresolved. Rules 13–15 belong to Section II: vessels are in sight of one another.

Rule 13 concerns any vessel overtaking another; Rules 14 and 15 address two power-driven vessels with collision risk. Head-on or crossing must not automatically be extended to two sailing vessels or radar-only detection in fog.

The illustration identifies static relationships rather than a manoeuvring sequence. Its simplified hulls describe aspect and heading, not actual velocities, distances or navigable space.

Rule 13(a) requires any overtaking vessel to keep out of the way, notwithstanding Part B Sections I and II. It prevents first choosing a more convenient rule based solely on propulsion type.

Overtaking comes from more than 22.5 degrees abaft the overtaken vessel’s beam, corresponding at night to seeing only its sternlight, not its sidelights. The angle references the overtaken vessel rather than our own bow or a fixed compass heading.

The sector illustration therefore places that vessel at the centre and identifies its beam and stern.

When in doubt about overtaking, Rule 13(c) requires assuming that it is the case. Subsequent bearing change does not turn the overtaker into a crossing vessel or remove the duty until finally past and clear under paragraph (d).

This continuity matters: the encounter is not restarted with every photograph. Special channel passing agreement under Rule 9(e) likewise does not remove the overtaker’s obligation.

Initial classification, development and conclusion must be read together rather than using a later aspect to escape an earlier duty.

The head-on situation involves reciprocal or nearly reciprocal courses and collision risk. Rule 14(a) requires both vessels to alter course to starboard, passing port to port.

Paragraph (b) describes aspect: the other ahead or nearly ahead, masthead lights aligned or nearly aligned and/or both sidelights by night, with corresponding daytime aspect. Paragraph (c) addresses doubt.

It is not a universal rule for any object seen ahead; its specified vessels and conditions remain essential. One visible white light alone may not establish the complete classification.

When two power-driven vessels cross with collision risk, the one with the other on its starboard side must keep out of the way and, if circumstances admit, avoid crossing ahead. Rule 16 develops the give-way vessel’s action and Rule 17 the other vessel’s action.

This does not assign priority to whichever boat lies on the right of a drawing viewed from shore. Starboard belongs to the observing vessel.

Rotating a page does not change its side, although a changing actual situation may change the relevant facts.

These rules preserve lookout, safe speed and effectiveness checks, together with relevant channel, scheme and responsibility duties. A useful figure states references and assumed facts; a misleading one suggests that every approach fits three recipes.

When studying a case, retain the exact rule rather than only an arrow. Lights can help recognise aspects, but limited observation, absent equipment or special arrangements require care in inference.

Its diagrams classify educational examples rather than supply navigational instructions; the relevant conditions remain part of every rule.