COLREGs Rule 8: Action to avoid collision
Last reviewed: October 14, 2026
Rule 8 sets out how a vessel must act to avoid collision. Action must follow the Rules and, if the circumstances of the case admit, be positive, made in ample time and with due regard to good seamanship. The vessel must carefully check the effectiveness of its action until the other vessel is finally past and clear. The International and Inland texts match, except that the Inland text refers to Subpart B (Rules 4-19) where the International text refers to the rules of this part.
What it says
Any action to avoid collision must follow the Rules and, if the circumstances of the case admit, must be positive, made in ample time and made with due regard to good seamanship.
COLREGs Rule 8(a)“shall, if the circumstances of the case admit, be positive, made in ample time and with due regard to the observance of good seamanship.”
If the circumstances of the case admit, a change of course and/or speed to avoid collision must be large enough to be readily apparent to another vessel observing visually or by radar. A succession of small changes should be avoided.
COLREGs Rule 8(b)“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, a change of course alone may be the most effective action. It must be made in good time, be substantial and not result in another close-quarters situation.
COLREGs Rule 8(c)“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.”
A vessel must carefully check the effectiveness of its collision-avoidance action until the other vessel is finally past and clear.
COLREGs Rule 8(d)“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 must slacken her speed or take all way off by stopping or reversing her means of propulsion.
COLREGs Rule 8(e)“a vessel shall slacken her speed or take all way off by stopping or reversing her means of propulsion.”
A vessel required not to impede another vessel's passage or safe passage must, when the circumstances of the case require, take early action to allow sufficient sea room for the other vessel's safe passage.
COLREGs Rule 8(f)(i)“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 another vessel is not relieved of that obligation when approaching the other vessel so as to involve risk of collision.
COLREGs Rule 8(f)(ii)“is not relieved of this obligation if approaching the other vessel so as to involve risk of collision”
Common questions
How big should a course or speed change be to avoid collision?
If the circumstances of the case admit, the change must be large enough to be readily apparent to another vessel observing visually or by radar. A succession of small alterations should be avoided.
“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.”
Can I avoid a collision by changing course alone?
If there is sufficient sea room, a change of course alone may be the most effective action. It must be made in good time, be substantial and not result in another close-quarters situation.
“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.”
How long must I check that my collision-avoidance action worked?
The vessel must carefully check the effectiveness of the action until the other vessel is finally past and clear.
“The effectiveness of the action shall be carefully checked until the other vessel is finally past and clear.”
What must a vessel do if it needs more time to assess a situation?
If necessary to avoid collision or allow more time to assess the situation, a vessel must slacken her speed or take all way off by stopping or reversing her means of propulsion.
“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.”
The text of COLREGs Rule 8
U.S. Coast Guard, Navigation Rules and Regulations Handbook
Rule 8: Action to Avoid Collision
International (COLREGs)
(a) Any action taken to avoid collision shall be taken in accordance with the Rules of this Part 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.
(b) 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.
(c) 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.
(d) 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.
(e) 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.
(ii) 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 this part.
(iii) A vessel, the passage of which is not to be impeded remains fully obliged to comply with the rules of this part when the two vessels are approaching one another so as to involve risk of collision.
Inland Rules
Action to avoid collision
(a) 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.
(b) 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.
(c) 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.
(d) 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.
(e) 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.
(ii) 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).
(iii) 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.
The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of August 12, 2024. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.