COLREGs Rule 19: Conduct of vessels in restricted visibility
Last reviewed: October 14, 2026
Rule 19 covers vessels not in sight of one another in or near an area of restricted visibility. Every vessel must proceed at a safe speed, and power-driven vessels must have engines ready for immediate maneuver. The rule also sets how to take avoiding action after a radar detection and when to slow down.
Applies toVessels not in sight of one another when navigating in or near an area of restricted visibility.
What it says
The rule applies to vessels not in sight of one another when navigating in or near an area of restricted visibility.
COLREGs Rule 19(a)“This Rule applies to vessels not in sight of one another when navigating in or near an area of restricted visibility.”
Every vessel must proceed at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility.
COLREGs Rule 19(b)“Every vessel shall proceed at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility.”
A power-driven vessel must have her engines ready for immediate maneuver.
COLREGs Rule 19(b)“A power-driven vessel shall have her engines ready for immediate maneuver.”
A vessel that detects another vessel by radar alone must determine if a close-quarters situation is developing or risk of collision exists. If so, she must take avoiding action in ample time.
COLREGs Rule 19(d)“A vessel which detects by radar alone the presence of another vessel shall determine if a close-quarters situation is developing and/or risk of collision exists.”
When avoiding action is a course alteration, a vessel must so far as possible avoid altering course to port for a vessel forward of the beam, other than for a vessel being overtaken.
COLREGs Rule 19(d)(i)“an alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken;”
When avoiding action is a course alteration, a vessel must so far as possible avoid altering course towards a vessel abeam or abaft the beam.
COLREGs Rule 19(d)(ii)“an alteration of course towards a vessel abeam or abaft the beam.”
Unless it is determined that no risk of collision exists, a vessel that hears a fog signal apparently forward of her beam, or cannot avoid a close-quarters situation with a vessel forward of her beam, must reduce speed to the minimum at which she can be kept on course.
COLREGs Rule 19(e)“shall reduce her speed to the minimum at which she can be kept on course.”
Common questions
What speed must a vessel use in restricted visibility?
Every vessel must proceed at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility. A power-driven vessel must also have her engines ready for immediate maneuver.
“Every vessel shall proceed at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility.”
What must a vessel do if she hears a fog signal forward of her beam?
Unless it has been determined that no risk of collision exists, she must reduce speed to the minimum at which she can be kept on course. If necessary she must take all her way off and navigate with extreme caution until danger of collision is over.
“She shall if necessary take all her way off and in any event navigate with extreme caution until danger of collision is over.”
What must a vessel do when she detects another vessel by radar alone?
She must determine if a close-quarters situation is developing or risk of collision exists. If so, she must take avoiding action in ample time.
“If so, she shall take avoiding action in ample time, provided that when such action consists of an alteration of course”
The text of COLREGs Rule 19
U.S. Coast Guard, Navigation Rules and Regulations Handbook
Rule 19: Conduct of Vessels in Restricted Visibility
(a) This Rule applies to vessels not in sight of one another when navigating in or near an area of restricted visibility. (b) Every vessel shall proceed at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility. A power-driven vessel shall have her engines ready for immediate maneuver. (c) Every vessel shall have due regard to the prevailing circumstances and conditions of restricted visibility when complying with the Rules of Section I of this part. (d) A vessel which detects by radar alone the presence of another vessel shall determine if a close-quarters situation is developing and/or risk of collision exists. If so, she shall take avoiding action in ample time, provided that when such action consists of an alteration of course, so far as possible the following shall be avoided: (i) an alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken; (ii) an alteration of course towards a vessel abeam or abaft the beam. (e) Except where it has been determined that a risk of collision does not exist, every vessel which hears apparently forward of her beam the fog signal of another vessel, or which cannot avoid a close-quarters situation with another vessel forward of her beam, shall reduce her speed to the minimum at which she can be kept on course. She shall if necessary take all her way off and in any event navigate with extreme caution until danger of collision is over.
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.