33 CFR 83.08: Action to avoid collision
Last reviewed: November 9, 2026
This section covers action a vessel takes to avoid collision. Action must follow the Rules of this subpart (Rules 4-19) and, if the circumstances of the case admit, be positive, made in ample time and show good seamanship. Alterations must, if circumstances admit, be large enough to be readily apparent, and action must result in passing at a safe distance.
What it says
Any action to avoid collision must follow the Rules of this subpart (Rules 4-19) and, if the circumstances of the case admit, be positive, made in ample time and show good seamanship.
33 CFR 83.08(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, an alteration of course and/or speed must be large enough to be readily apparent to another vessel observing visually or by radar, and a succession of small alterations should be avoided.
33 CFR 83.08(b)“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, altering course alone may be the most effective action to avoid a close-quarters situation, provided it is made in good time, is substantial and does not result in another close-quarters situation.
33 CFR 83.08(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.”
The effectiveness of action taken to avoid collision with another vessel must be carefully checked until the other vessel is finally past and clear.
33 CFR 83.08(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.
33 CFR 83.08(e)“a vessel shall slacken her speed or take all way off by stopping or reversing her means of propulsion.”
A vessel required by any of these Rules not to impede the passage or safe passage of another vessel must, when the circumstances of the case require, take early action to allow sufficient sea room for the other vessel's safe passage.
33 CFR 83.08(f)(i)“take early action to allow sufficient sea room for the safe passage of the other vessel.”
A vessel whose passage is not to be impeded remains fully obliged to comply with the Rules of Subpart B (Rules 4-19) when the two vessels approach so as to involve risk of collision.
33 CFR 83.08(f)(iii)“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.”
Common questions
How large must a course or speed change be to avoid collision?
If the circumstances of the case admit, it 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 a vessel slow down or stop to avoid a collision?
Yes. 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.”
How long must a vessel check that its avoiding action is working?
The vessel must carefully check the effectiveness of its 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.”
The text of 33 CFR 83.08
Electronic Code of Federal Regulations (eCFR), current as of April 16, 2026 · Read it on eCFR
Action to avoid collision (Rule 8)
(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.
Sections it refers to
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 April 16, 2026. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.