COLREGs · Rule 8 · 33 CFR §83.08

Action to Avoid Collision

Action to avoid collision shall be positive, made in ample time, and large enough to be readily apparent to another vessel observing visually or by radar. A succession of small alterations should be avoided.

What does Rule 8 actually say?#

Source

Verbatim 33 CFR §83.08, public domain. The international COLREGs text is published by the IMO and cannot be reproduced here; this U.S. wording tracks it closely.

Any action taken to avoid collision shall be taken in accordance with the Rules of this subpart (Rules 4-19) (§§ 83.04 through 83.19) and shall, if the circumstances of the case admit, be positive, made in ample time and with due regard to the observance of good seamanship.

Any alteration of course and/or speed to avoid collision shall, if the circumstances of the case admit, be large enough to be readily apparent to another vessel observing visually or by radar; a succession of small alterations of course and/or speed should be avoided.

If there is sufficient sea room, alteration of course alone may be the most effective action to avoid a close-quarters situation provided that it is made in good time, is substantial and does not result in another close-quarters situation.

Action taken to avoid collision with another vessel shall be such as to result in passing at a safe distance. The effectiveness of the action shall be carefully checked until the other vessel is finally past and clear.

If necessary to avoid collision or allow more time to assess the situation, a vessel shall slacken her speed or take all way off by stopping or reversing her means of propulsion. (f)(i) A vessel which, by any of these Rules, is required not to impede the passage or safe passage of another vessel shall, when required by the circumstances of the case, take early action to allow sufficient sea room for the safe passage of the other vessel.

A vessel required not to impede the passage or safe passage of another vessel is not relieved of this obligation if approaching the other vessel so as to involve risk of collision and shall, when taking action, have full regard to the action which may be required by the Rules of Subpart B (Rules 4-19).

A vessel the passage of which is not to be impeded remains fully obliged to comply with the Rules of Subpart B (Rules 4-19) when the two vessels are approaching one another so as to involve risk of collision.

Practice this rule#

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

Rule 8 — Action to Avoid Collision

According to the Inland Navigation Rules, a succession of small alterations of course and/or speed to avoid collision should be:

Does Inland Rule 8 change anything?#

Inland Rule 8 is 33 CFR §83.08, reproduced above, and carries no exam-relevant divergence from COLREGs Rule 8. 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#

Rule 8 is the how-to that Rules 13 through 18 rely on: they say who acts, Rule 8 says what the action has to look like. Expect questions built on its two most testable phrases — 'readily apparent' and 'finally past and clear'.

What does the exam actually test here?#

Character of the action
Positive, ample time, good seamanship
Any action to avoid collision must be taken in accordance with Rules 4–19 and, if circumstances admit, be positive, made in ample time, and with due regard to the observance of good seamanship.
Size of the action
Readily apparent
An alteration of course and/or speed must be large enough to be readily apparent to another vessel observing visually or by radar. A succession of small alterations should be avoided — the classic wrong answer is nudging the helm repeatedly.
Following through
Until finally past and clear
Action must result in passing at a safe distance, and its effectiveness must be carefully checked until the other vessel is finally past and clear. If necessary, slacken speed or take all way off by stopping or reversing.

Rule 8 — common exam questions#

What kind of avoiding action does Rule 8 require?

If the circumstances admit, action must be positive, made in ample time, and with due regard to good seamanship, and any course or speed change must be large enough to be readily apparent to another vessel observing visually or by radar (33 CFR §83.08(a)–(b)).

Why is a series of small course changes wrong?

Rule 8(b) says a succession of small alterations of course and/or speed should be avoided. Small changes are hard for another vessel to detect visually or on radar, so they fail the 'readily apparent' test that makes avoiding action work.

When is a course change alone enough?

Rule 8(c) says that if there is sufficient sea room, alteration of course alone may be the most effective action, provided it is made in good time, is substantial, and does not result in another close-quarters situation.

What does 'not impede the passage' require?

A vessel required not to impede another must take early action to allow sufficient sea room for the other's safe passage. That obligation is not cancelled by risk of collision arising, and the vessel whose passage is not to be impeded still has to comply with Rules 4–19 (33 CFR §83.08(f)).

When should you stop or reverse?

Rule 8(e) requires a vessel to slacken speed or take all way off by stopping or reversing her means of propulsion if that is necessary to avoid collision or to allow more time to assess the situation.

Authoritative source#

33 CFR §83.08 — this section with its neighbours. 33 CFR Part 83 is public domain; checked 2026-05-16.
COLREGs Rule 8 is published by the IMO and is authoritative internationally.

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