Conduct of Vessels in Restricted Visibility

Rule text#

(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 Rules 4 through 10 (§§ 83.04 through 83.10).

(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 toward 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. [USCG-2012-0102, 79 FR 37912, July 2, 2014, as amended by USCG-2015-0433, 80 FR 44280, July 27, 2015]

Why it shows up on the exam#

Two things are tested almost every time. First: Rule 19 has NO stand-on vessel — candidates who answer 'the other vessel must hold course' get it wrong. Second, Rule 19(d)'s two prohibited alterations: do not turn to port for a vessel forward of the beam (unless you are overtaking it), and do not turn toward a vessel abeam or abaft the beam.

Exam checkpoints#

1. 1.

   No stand-on vessel

   Both vessels act

   Rule 19 applies only to vessels not in sight of one another, and the give-way / stand-on relationship of Rules 15–17 depends on being in sight. In restricted visibility neither vessel has the right to hold her course and speed on that basis; each is independently responsible for avoiding collision. This is the single most-missed point on the Rules module.

2. 2.

   Safe speed

   Engines ready for immediate manoeuvre

   Rule 19(b) requires every vessel to proceed at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility, and a power-driven vessel to have her engines ready for immediate manoeuvre. Rule 19(c) adds that Rules 4 through 10 still apply, read with due regard to the conditions.

3. 3.

   Radar alone

   Assess, then act in ample time

   Under Rule 19(d), a vessel that detects the presence of another vessel by radar alone must determine whether a close-quarters situation is developing or a risk of collision exists, and if so take avoiding action in ample time — a duty that begins before anything is seen or heard.

4. 4.

   Rule 19(d) prohibitions

   No port turn forward of the beam

   When taking avoiding action on radar information alone, two alterations are to be avoided so far as possible: an alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken, and an alteration of course toward a vessel abeam or abaft the beam.

5. 5.

   Rule 19(e)

   Bare steerage, then all way off

   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 that 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, and if necessary take all her way off. In every case she must navigate with extreme caution until danger of collision is over.

Where Inland differs#

Inland Rule 19 (33 CFR §83.19) carries the same text as COLREGs Rule 19 — this is one of the rules where International and Inland do not diverge, so an answer that is right in one rulebook is right in the other. What differs is the surrounding Part D signals: the Inland one- and two-short-blast signals of Rule 34 are signals of intent rather than action, but those apply only to vessels IN SIGHT of one another, which is precisely the case Rule 19 excludes.

Rule 19 — common exam questions#

Is there a stand-on vessel in restricted visibility?

No. Rule 19 applies to vessels not in sight of one another, and the give-way and stand-on roles in Rules 15 through 17 apply only to vessels in sight of one another. In fog neither vessel may rely on the other holding course and speed — both are obliged to take action to avoid collision. Exam questions that offer 'the other vessel is the stand-on vessel' as an option in restricted visibility are testing exactly this.

Why can't you turn to port in fog?

Rule 19(d) tells a vessel acting on radar information alone to avoid, so far as possible, altering course to port for a vessel forward of the beam unless that vessel is being overtaken. The reason is practical: in a meeting or crossing situation a port turn steers into the water the other vessel is most likely to occupy if she makes the conventional starboard alteration, converting a passing situation into a collision. The same paragraph also warns against altering course toward a vessel abeam or abaft the beam.

What sound signal do you make in fog?

Rule 19 sets the conduct; the signals themselves are in Rule 35 (33 CFR 83.35). A power-driven vessel making way sounds one prolonged blast at intervals of not more than 2 minutes. Underway but stopped and making no way through the water, she sounds two prolonged blasts about 2 seconds apart, at the same interval. A vessel not under command, restricted in her ability to manoeuvre, constrained by draft, sailing, fishing, or towing sounds one prolonged followed by two short blasts, and a towed vessel one prolonged followed by three short. A vessel at anchor rings her bell rapidly for about 5 seconds every minute, and a vessel aground adds three separate strokes on the bell before and after that ringing.

What does 'bare steerage' mean under Rule 19?

It is the minimum speed at which the vessel can still be kept on course — enough water flow over the rudder to steer, and no more. Rule 19(e) requires that speed on hearing a fog signal apparently forward of the beam or when a close-quarters situation forward of the beam cannot be avoided, and requires taking all way off if necessary. The rule then requires navigating with extreme caution until the danger of collision is over.

Does Rule 19 apply if you can see the other vessel on radar?

Yes. Seeing a target on radar is not being 'in sight of one another' — Rule 3 defines that as being visually observed. A vessel tracked on radar in fog is still a Rule 19 case, which is why 19(d) is written specifically for action taken on radar information alone.

Is Inland Rule 19 different from COLREGs Rule 19?

No. 33 CFR 83.19 carries the same requirements as COLREGs Rule 19, so this is one of the rules where the two rulebooks agree and an answer correct under one is correct under the other. Candidates sometimes expect a difference because so much of Part D diverges between the rulebooks; here it does not.

Authoritative source#

Source links checked against the current public rule corpus on 2026-07-26.

• 33 CFR §83.19 — the section this text comes from, with its neighbours.
• International COLREGs Rule 19 verbatim text is published by the IMO and is authoritative for international waters.

Practice this rule#

One real exam question on this rule, cited to source. No sign-up.