COLREG 72 #15
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.
(i) 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)(i) 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.