In restricted visibility, a vessel that detects another by radar alone, forward of her beam and not being overtaken, and decides to alter course, should so far as possible avoid an alteration:

To port. Rule 19(d): avoid an alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken.

COLREGs trainerPart B: Steering and Sailing Rules

Rule 19

Conduct in Restricted Visibility

Safe speed in RV; on radar alone, avoid turning to port for a vessel forward of the beam (unless overtaking her) or towards one abeam or abaft.

Paragraph (a): Application

This Rule applies to vessels not in sight of one another when navigating in or near an area of restricted visibility.

1 / 5

Wording follows the International Regulations as printed in the US Coast Guard Navigation Rules handbook (2024), with British spelling, and is shortened in places. Download the rules

Read the whole of Rule 19 on one page

Paragraph (a): Application

This Rule applies to vessels not in sight of one another when navigating in or near an area of restricted visibility.

Paragraph (b): Safe speed

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 manoeuvre.

Paragraph (c): Regard to Section I

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.

Paragraph (d): Detection by radar alone

A vessel detecting by radar alone the presence of another shall determine whether a close-quarters situation is developing and/or risk of collision exists. If so, she shall take avoiding action in ample time; where that action is an alteration of course, so far as possible avoid: (i) an alteration to port for a vessel forward of the beam, other than for a vessel being overtaken; (ii) an alteration towards a vessel abeam or abaft the beam.

Paragraph (e): Hearing a fog signal forward

Except where it has been determined that no risk of collision exists, 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 to the minimum speed at which she can be kept on course. She shall if necessary take all way off, and in any event navigate with extreme caution until danger of collision is over.

Test yourself on Rule 19

In restricted visibility, a vessel that detects another by radar alone, forward of her beam and not being overtaken, and decides to alter course, should so far as possible avoid an alteration:: To port. Rule 19(d): avoid an alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken.

Take the ten-question quiz →

A training aid, not the official text. The COLREGs are an IMO convention, and your national authority publishes the version that applies in its waters. Check the rules themselves before you rely on them at sea. Download the rules.