Section II: Conduct of vessels in sight of one another
The stand-on vessel: Rule 17
In practice
- You are the vessel that keeps her course and speed. Your predictability is what lets the give-way vessel plan a proper manoeuvre.
- When it becomes apparent the other vessel is not taking appropriate action, you may manoeuvre alone (paragraph a.ii). When the ships are so close that the give-way vessel’s action alone cannot avoid collision, you must take the action that best helps to avoid it (paragraph b).
- In a crossing, do not turn to port for a vessel on your own port side (paragraph c): you would turn into each other’s way.
Text of Rule 17: Action by Stand-on Vessel
(a)
- (i) Where one of two vessels is to keep out of the way the other shall keep her course and speed.
- (ii) The latter vessel may however take action to avoid collision by her manoeuvre alone, as soon as it becomes apparent to her that the vessel required to keep out of the way is not taking appropriate action in compliance with these Rules.
(b) When, from any cause, the vessel required to keep her course and speed finds herself so close that collision cannot be avoided by the action of the give-way vessel alone, she shall take such action as will best aid to avoid collision.
(c) A power-driven vessel which takes action in a crossing situation in accordance with subparagraph (a)(ii) of this Rule to avoid collision with another power-driven vessel shall, if the circumstances of the case admit, not alter course to port for a vessel on her own port side.
(d) This Rule does not relieve the give-way vessel of her obligation to keep out of the way.
Text of the International Regulations as amended, quoted from the consolidated U.S. Coast Guard Navigation Rules (public domain); spelling follows the IMO original. When in doubt, the Convention decides.
The common mistake
Holding course and speed to the very end "because I stand on". Rule 17b puts a duty on the stand-on vessel to act when collision can no longer be avoided by the give-way vessel alone.