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17

Action by Stand-on Vessel

Three successive positions of one vessel illustrate the initial stand-on duty to maintain course and speed. Later permission or obligation to intervene under Rule 17 still applies. The image shows no other vessel and grants no absolute right of way.

Rule 17 defines the obligations of the stand-on vessel.

a
  • 1Where one vessel is required to keep out of the way, the other shall keep her course and speed.
  • 2The stand-on 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.
b
When the stand-on vessel 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 sub-paragraph (a)
  • 2of 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
Action by the stand-on vessel does not relieve the give-way vessel of her obligation to keep out of the way.
The stand-on vessel may act as soon as the give-way vessel's failure to take appropriate action becomes apparent. When so close that give-way action alone cannot avoid collision, she must take the action that best helps avoid it. This still image establishes no range or time threshold.
Two power-driven vessels in sight, crossing with risk of collision. A has B on its starboard side and must keep out of the way; the red track illustrates an early starboard alteration. B initially keeps course and speed, subject to Rule 17.

IMO COLREG 1972Official text

Full wording of the rule, reproduced from the official source below.

(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 maneuver 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.
Source:

STCW Bridge Watch Lens

Rules 4–10 apply in any visibility.

Rules 11–18 apply to vessels in sight of one another; Rule 19 applies to vessels not in sight when navigating in or near an area of restricted visibility.

Build the traffic picture with sight, hearing, radar/ARPA and chart context.

Do not let AIS or one isolated bearing replace systematic observation.

After manoeuvring, keep monitoring bearing, range, CPA/TCPA and passing distance until the other vessel is finally past and clear.

Exam Focus

Identify the vessel types first, then the relative bearing, then whether one vessel is overtaking.

Misclassifying the encounter is the usual exam failure.

For vessels in sight, every overtaking vessel keeps clear until finally past and clear.

Rule 13 takes precedence over Part B Sections I and II; it does not override the other Parts of COLREG.

Key Takeaways

1

Initially maintain course and speed when the other vessel is required to keep out of the way

2

MAY act alone when it becomes apparent that the give-way vessel is not taking appropriate action

3

MUST act when collision cannot be avoided by the give-way vessel alone

4

When a power-driven stand-on vessel acts under 17(a)(ii) against another power-driven vessel on her port side, avoid a port alteration if circumstances admit

Common Mistakes

Confusing permission to act under 17(a)(ii) with the mandatory threshold in 17(b)

Maintaining course and speed after the give-way vessel alone can no longer avoid collision

Assuming the give-way vessel's obligations end when the stand-on vessel acts

Test Your Knowledge

Practise this topic and review the explanation for each answer.

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Frequently asked questions about COLREG Rule 17

What must the stand-on vessel do under COLREG Rule 17?

Where one of two vessels is to keep out of the way, the other shall keep her course and speed (Rule 17(a)(i)). The stand-on vessel initially maintains course and speed rather than manoeuvring.

When may the stand-on vessel take avoiding action?

As soon as it becomes apparent that the vessel required to keep out of the way is not taking appropriate action, the stand-on vessel may act to avoid collision by her manoeuvre alone (Rule 17(a)(ii)). If she finds herself so close that collision cannot be avoided by the give-way vessel alone, she shall take such action as will best aid to avoid collision.

May the stand-on vessel alter course to port in a crossing situation?

No, so far as the circumstances admit. A power-driven vessel taking action under Rule 17(a)(ii) to avoid collision with another power-driven vessel shall not alter course to port for a vessel on her own port side.