Part B-IICritical
Rule 13: Overtaking
Overtaking duty is strict: the overtaking vessel keeps clear until finally past and clear.
Detailed Explanation
Overtaking imposes a strict, continuing duty on the vessel coming up from astern until she is finally past and clear.
A
Any overtaking vessel must keep out of the way of the vessel being overtaken.
B
Overtaking means approaching from more than 22.5° abaft beam (night test: sternlight only).
C
In doubt, assume overtaking.
D
Later bearing changes do not convert it to crossing or remove overtaking duty until finally past and clear.
Key Points
- 22.5° abaft the beam test defines overtaking
- Duty to keep clear applies until finally past and clear
- An overtaking vessel remains give-way regardless of later changes
- Doubt about overtaking → treat as overtaking
Examples
- You approach a bulk carrier from 30° abaft her port beam on a converging course. That is more than 22.5° abaft beam, so you are the overtaking vessel under Rule 13(b) and must keep clear until finally past and clear.
- After overtaking a tanker, the relative bearing changes and you are now technically forward of her beam. Rule 13(d) states this subsequent alteration does not relieve you of the duty to keep clear.
- At night you can see only the sternlight of the vessel ahead — no sidelights. This confirms you are approaching from abaft beam; you treat the situation as overtaking per Rule 13(b).
Common Mistakes
- Believing the overtaking duty ends once you change course to cross the other vessel's bow.
- Not recognizing 22.5 degrees abaft the beam as the critical overtaking sector boundary.
- Assuming a change in relative bearing converts an overtaking situation into a crossing one.