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COLREG Rule 19: restricted visibility explained

When you can't see the other vessel, the usual "who gives way" picture no longer works. Rule 19 is the rule that governs conduct when vessels are not in sight of one another in or near an area of restricted visibility.

It covers safe speed, engine readiness, action after detecting another vessel by radar alone, and what to do on hearing a fog signal apparently forward of the beam.

Restricted visibility means any condition in which visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms or similar causes (Rule 3(l)).

Rule 19 in five steps

An introductory teaching sequence. The detailed paragraphs follow below.

  1. 1.You are not in sight of the other vessel, and you are in or near an area of restricted visibility.
  2. 2.Proceed at a safe speed adapted to the conditions and, if power-driven, have engines ready for immediate manoeuvre.
  3. 3.Use all available information to assess the situation, including radar where fitted and available.
  4. 4.If a close-quarters situation is developing and/or risk of collision exists, take avoiding action in ample time.
  5. 5.If you hear a fog signal apparently forward of the beam, or cannot avoid close quarters with a vessel forward of the beam, reduce speed as required by Rule 19(e), take all way off if necessary, and navigate with extreme caution until the danger is over. (This does not apply where it has been determined that risk of collision does not exist.)

What Rule 19 requires, paragraph by paragraph

A plain-English summary of each paragraph. Read the rule itself for the exact wording.

When it applies — Rule 19(a)

Vessels not in sight of one another when navigating in or near an area of restricted visibility.

Safe speed and engines — Rule 19(b)

Every vessel proceeds at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility. A power-driven vessel has her engines ready for immediate manoeuvre.

Due regard — Rule 19(c)

When complying with the Rules of Section I of Part B (Rules 4–10), every vessel has due regard to the prevailing circumstances and conditions of restricted visibility.

Detected by radar alone — Rule 19(d)

Learner cue

Contact ahead: as a general Rule 19 principle, avoid altering to port, except when overtaking.

Contact abeam or abaft the beam: avoid altering towards it.

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

Fog signal forward of the beam — Rule 19(e)

Except where it has been determined that a risk of collision does not exist, a vessel that hears, apparently forward of her beam, the fog signal of another vessel, or cannot avoid a close-quarters situation with another vessel forward of her beam, reduces her speed to the minimum at which she can be kept on her course. If necessary she takes all her way off, and in any event navigates with extreme caution until danger of collision is over.

What Rule 19 is not

Remember

In restricted visibility, don't think "I'm stand-on and they're give-way". Neither vessel should assume stand-on status. Both vessels must comply with Rule 19 and take action when the Rule requires it.

  • It is not the stand-on/give-way rules moved into fog. The Section II rules (Rules 11–18) apply to vessels in sight of one another.
  • Some obligations not to impede another vessel, including those arising under Rules 9 and 10 together with Rule 8(f), can still apply in restricted visibility.
  • It is not permission to rely on radar alone. Rules 5 (lookout), 6 (safe speed) and 7 (risk of collision) still apply.
  • It is not the sound-signal table. Those signals are in Rule 35.

How Rule 19 relates to Rule 35

Rule 35

What sound signal you hear or give.

Rule 19

How you conduct the vessel in restricted visibility.

Rule 19(e) refers to hearing another vessel's fog signal, but it does not list or define those signals. The patterns come from Rule 35. Learn the two together.

Related: COLREG sound signals and Day Skipper revision.

A revision reference, not a substitute for training

This page explains the structure of Rule 19. It is not navigation advice and does not replace recognised training, official sources, professional instruction or time on the water.

StandOn is an independent sailing revision platform and is not affiliated with or endorsed by the Royal Yachting Association.