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COLREGs · Rule 17 · 33 CFR §83.17

Action by Stand-on Vessel

The stand-on vessel keeps her course and speed. If it becomes apparent the give-way vessel is not taking appropriate action, the stand-on may take action; when collision cannot be avoided by the give-way alone, she shall take such action as will best aid to avoid collision.

What does Rule 17 actually say?#

Source

Verbatim 33 CFR §83.17, public domain. The international COLREGs text is published by the IMO and cannot be reproduced here; this U.S. wording tracks it closely.
(a)(i) Where one of two vessels is to keep out of the way, the other shall keep her course and speed.
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.
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.
A power-driven vessel which takes action in a crossing situation in accordance with paragraph (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.
This Rule does not relieve the give-way vessel of her obligation to keep out of the way.
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.
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.
A power-driven vessel which takes action in a crossing situation in accordance with paragraph (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.
This Rule does not relieve the give-way vessel of her obligation to keep out of the way.

Practice this rule#

One real exam question on this rule, cited to source. No sign-up.

Rule 17 — Action by Stand-on Vessel

Under the Inland Navigation Rules, when the stand-on vessel finds herself so close to the give-way vessel that collision cannot be avoided by the action of the give-way vessel alone, what must the stand-on vessel do?

Does Inland Rule 17 change anything?#

Inland Rule 17 is 33 CFR §83.17, reproduced above, and carries no exam-relevant divergence from COLREGs Rule 17. One answer serves both the International and the Inland version of a Rules of the Road question on this rule — which is worth knowing precisely because several neighbouring rules do not work that way.

21 of 38 rules differ somewhere; the five the exam leans on are Rule 9, Rule 10, Rule 24, Rule 28 and Rule 34, side by side on Inland vs International Rules.

Why it shows up on the exam#

The stand-on must NOT alter course to port for a vessel on her own port side — that's the most common Rule 17 trap.

What does the exam actually test here?#

  1. The default

    Keep course and speed

    Where one of two vessels is to keep out of the way, the other keeps her course and speed. Holding on is the stand-on vessel's obligation, not merely her privilege.

  2. The 'may' stage

    Give-way is not acting

    The stand-on vessel may take action to avoid collision by her maneuver alone as soon as it becomes apparent that the give-way vessel is not taking appropriate action in compliance with the Rules.

  3. The 'shall' stage

    Collision cannot be avoided by give-way alone

    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. In a crossing between power-driven vessels, she shall not alter course to port for a vessel on her own port side.

Rule 17 — common exam questions#

What must a stand-on vessel do?

Keep her course and speed (33 CFR §83.17(a)(i)) — until one of the two escape provisions in the rest of Rule 17 applies.

When may the stand-on vessel manoeuvre?

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 the Rules (33 CFR §83.17(a)(ii)). At that point action is permitted, not yet required.

When must the stand-on vessel act?

When, from any cause, she finds herself so close that collision cannot be avoided by the action of the give-way vessel alone — then she shall take such action as will best aid to avoid collision (33 CFR §83.17(b)).

Why should a stand-on vessel not turn to port?

Rule 17(c) says a power-driven vessel taking action in a crossing situation with another power-driven vessel shall, if circumstances admit, not alter course to port for a vessel on her own port side — a turn to port would steer into the give-way vessel's expected escape.

Does the stand-on vessel's action release the give-way vessel?

No. Rule 17(d) states the rule does not relieve the give-way vessel of her obligation to keep out of the way.

Authoritative source#

  • 33 CFR §83.17 — this section with its neighbours. 33 CFR Part 83 is public domain; checked 2026-05-16.
  • COLREGs Rule 17 is published by the IMO and is authoritative internationally.

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