When you hear a fog signal apparently forward of your beam, you must reduce speed to the minimum at which you can be kept on course, take all your way off if necessary, and navigate with extreme caution until danger of collision is over. Rule 19 reads word-for-word the same International and Inland, so any question on it is a "Both" question.
What the rule requires
Two conditions must hold together before Rule 19 governs. The vessels are not in sight of one another, and they are navigating in or near an area of restricted visibility 33 CFR §83.19. Break either condition and Rule 19 is not the rule you are being asked about.
Both terms are defined, and the definitions are the whole game. Vessels are deemed to be in sight of one another only when one can be observed visually from the other 33 CFR §83.03. Restricted visibility means any condition in which visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms, or any other similar cause — fog is the usual exam dressing, but snow and heavy rain switch the rule on identically.
The structural consequence sits one section earlier: Rules 11 through 18 apply to vessels in sight of one another 33 CFR §83.11. In restricted visibility with no visual contact there is no stand-on vessel and no give-way vessel, because the rules that create those roles are not in force. Every vessel carries the obligation to act.
Safe speed and engines
Every vessel shall proceed at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility, and a power-driven vessel shall have her engines ready for immediate maneuver . That second sentence is a distractor magnet: engines ready for immediate maneuver is a standing requirement the moment you are in or near restricted visibility, not something you do after you detect a target.
The action on hearing a fog signal — Rule 19(e)
This is the paragraph the exam tests most. 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.
Read the sequence in that order, because the answer options are built out of its pieces:
- Reduce to minimum steerageway — the least speed at which she can be kept on course.
- Take all way off if necessary — conditional, not automatic.
- Navigate with extreme caution until danger of collision is over.
Two triggers, either of which is enough: the fog signal heard apparently forward of the beam, or a close-quarters situation forward of the beam that you cannot avoid. A signal heard abaft the beam does not fire 19(e).
Radar alone — Rule 19(d)
A vessel which detects by radar alone the presence of another vessel 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, and where that action is an alteration of course, two alterations are to be avoided so far as possible:
- To port for a vessel forward of the beam, other than for a vessel being overtaken.
- Toward a vessel abeam or abaft the beam.
The working shorthand instructors use is: nothing to port for anything ahead, nothing toward anything behind. It is sound as far as it goes, and it leaves out the one exception the exam likes — you may alter to port for a vessel you are overtaking.
You are on radar watch in fog. A target is 30° on your port bow, closing, CPA 0.2 mile. Which way do you come, and what else does Rule 19 require of you before you touch the wheel?
Come to starboard. Rule 19(d)(i) tells you to avoid altering to port for a vessel forward of the beam unless she is being overtaken, and this vessel is fine on the port bow. The alteration must be made in ample time rather than at close quarters. Independently of the alteration, you must already be at a safe speed adapted to the conditions with engines ready for immediate maneuver under 19(b), and if you hear her fog signal forward of the beam, 19(e) requires you to come down to minimum steerageway regardless of what your radar plot shows.
The rest of the steering and sailing rules do not switch off
Every vessel shall have due regard to the prevailing circumstances and conditions of restricted visibility when complying with Rules 4 through 10 . Under the International Rules the same paragraph refers to the Rules of Section I, which apply in any condition of visibility COLREGs Rule 4. Rule 19 replaces Rules 11 through 18 in fog; it does not replace what comes before them.
Lights and the signal you are listening for
Lights prescribed by the Rules shall, if carried, also be exhibited from sunrise to sunset in restricted visibility COLREGs Rule 20. Inland Rule 20 is word-for-word identical, so navigation lights by day in fog is a "Both" answer.
The signals that put 19(e) in motion are prescribed under the International Rules at intervals of not more than 2 minutes: one prolonged blast for a power-driven vessel making way; two prolonged blasts, about 2 seconds apart, for a power-driven vessel underway but stopped and making no way; one prolonged followed by two short for a vessel not under command, restricted in her ability to maneuver, constrained by her draft, a sailing vessel, a vessel engaged in fishing, or a vessel towing or pushing; one prolonged followed by three short from the manned last vessel of a tow COLREGs Rule 35. Inland Rule 35 is flagged as differing from the International rule, so do not carry these across to an "Inland Only" question without checking 33 CFR §83.35. The constrained-by-draught class in that list is International only — Inland Rule 28 is reserved and the Inland Rules do not recognise her as a distinct class COLREGs Rule 28.
Telling it apart
The single criterion is whether one vessel can be observed visually from the other. Everything else follows from that one test.
- In sight of one another — visual contact exists, so Rules 11 through 18 are in force and there is a stand-on and a give-way vessel 33 CFR §83.11. Most often misfiled: two vessels a half mile apart in thin haze who can still see each other's hulls. They are in sight. Rule 19 does not apply, whatever the visibility is elsewhere in the area.
- Not in sight, in or near restricted visibility — Rule 19 governs and neither vessel is stand-on. Most often misfiled: the candidate who has a solid radar picture, a clean plot and a steady bearing, and concludes she is the crossing stand-on vessel. Radar contact is not visual observation 33 CFR §83.03.
- Clear air, but near a fog bank — Rule 19 applies to vessels navigating in or near an area of restricted visibility 33 CFR §83.19. Most often misfiled: sunlight on your own bridge wing treated as proof the rule is off.
A second pair separates cleanly and is worth fixing now. Minimum steerageway is the speed at which she can still be kept on course, and it is what 19(e) demands the moment you hear that signal. All way off is a stop, and 19(e) requires it only if necessary. An option that makes stopping the immediate required action is over-reading the rule; an option that leaves you at moderate speed is under-reading it.
Working a question
Take the NMC-style stem verbatim in structure: you are underway in heavy fog, you hear the fog signal of a vessel somewhere ahead. What are you required to do?
- Establish which rule is in force. Heavy fog is restricted visibility, and you have heard her rather than seen her, so you are not in sight of one another 33 CFR §83.03. Both conditions of Rule 19(a) are met. Rules 11 through 18 are out, so no option that assigns you a stand-on role or a right of way can be correct.
- Locate the contact relative to your beam. "Somewhere ahead" is forward of the beam. That is the bearing 19(e) keys on — a signal abaft the beam does not fire the paragraph.
- Check the exception. 19(e) opens with "except where it has been determined that a risk of collision does not exist." Nothing in the stem lets you make that determination. The exception does not release you.
- Apply the required action in the order the rule states it. Reduce speed to the minimum at which you can be kept on course; take all way off if necessary; navigate with extreme caution until danger of collision is over 33 CFR §83.19.
- Read the options against step 4. "Slow to moderate speed" is not minimum steerageway. "Stop engines" makes conditional action mandatory and skips the required first step. "Maintain speed and sound five short and rapid blasts" fails on both halves — speed must come off, and the doubt signal belongs to vessels in sight of one another under Rules 11 through 18. The answer is the one that pairs minimum speed to maintain course with navigating with caution.
Where a stem instead reads "risk of collision may exist" and offers stopping engines, taking all way off if necessary, and beginning a radar plot as separate options, work the same order: the conditional "if necessary" language in the option is what matches the rule's own wording, and the rule nowhere makes stopping the outright requirement.
Where candidates lose the point
Answering as the stand-on vessel because the geometry looks like a crossing. A steady bearing and decreasing range on the plot feels exactly like Rule 15. Rules 11 through 18 apply to vessels in sight of one another, full stop 33 CFR §83.11, and a target seen only on radar is not in sight 33 CFR §83.03.
Choosing "stop your engines" for 19(e). It sounds like the most prudent answer and prudence is usually rewarded. The rule specifies minimum steerageway first and all way off only if necessary 33 CFR §83.19. A vessel with no way on cannot steer.
Turning to port for a target fine on the port bow. The instinct is to open the range by turning away from her. 19(d)(i) rules it out for any vessel forward of the beam except one being overtaken.
Treating restricted visibility as fog only. Falling snow, mist, heavy rainstorms and sandstorms are named in the definition, along with any other similar cause. A question set in a snow squall is a Rule 19 question.
Guessing "International Only" or "Inland Only" on a Rule 19 stem. Inland Rule 19 is word-for-word identical to the International rule COLREGs Rule 19, so a stem confined to Rule 19 conduct is a "Both" question. Save the hedging for Rule 35, where the two do diverge.
Reading 19(c) as an exemption. Some candidates take "due regard to the prevailing circumstances" as licence to relax Rules 4 through 10 in fog. It is the opposite instruction: comply with them, with the conditions of restricted visibility in mind.
Check yourself
You are underway in dense fog on a heading of 090°. A vessel's fog signal is heard broad on your starboard quarter. Are you required to reduce to minimum steerageway?
No. Rule 19(e) fires on a fog signal heard apparently forward of the beam, or on a close-quarters situation forward of the beam you cannot avoid. Broad on the starboard quarter is abaft the beam. You remain bound by 19(b) — safe speed adapted to the conditions, engines ready for immediate maneuver — and by 19(d) if you have her on radar.
Visibility is one mile in mist. You see another power-driven vessel visually, fine on your port bow, crossing. Which rule governs your conduct?
Not Rule 19. You can observe her visually, so you are in sight of one another and Rules 11 through 18 apply. Rule 19 governs only vessels not in sight of one another. Reduced visibility on its own does not switch it on.
You detect a vessel by radar alone, bearing 160° relative, range 4 miles, closing. You wish to open the CPA by altering course. Which alteration does Rule 19(d) tell you to avoid?
An alteration toward her. She is abaft your beam, and 19(d)(ii) says to avoid, so far as possible, an alteration of course toward a vessel abeam or abaft the beam. The port-turn prohibition in 19(d)(i) is about vessels forward of the beam and does not decide this one.
It is 1400 on a clear afternoon, but a bank of dense fog lies a half mile ahead on your track. Does Rule 19 apply to you, and what should be showing on your masts?
Yes. Rule 19 applies to vessels navigating in or near an area of restricted visibility. Under Rule 20(c) the lights prescribed by the Rules shall, if carried, also be exhibited from sunrise to sunset in restricted visibility, and Inland Rule 20 is identical.
Overtaking in restricted visibility on radar, you have a vessel two points on your starboard bow at 3 miles and intend to pass down her port side, which requires an alteration to port. Permitted?
Yes. 19(d)(i) directs you to avoid an alteration of course to port for a vessel forward of the beam other than for a vessel being overtaken. She is being overtaken, so the exception applies. The alteration must still be made in ample time.
In fog you hear one prolonged blast followed by two short blasts forward of your beam. Under the International Rules, name three classes of vessel that could be making it — and what does the signal require of you?
Under COLREGs Rule 35(c), that group is sounded at intervals of not more than 2 minutes by a vessel not under command, a vessel restricted in her ability to maneuver, a vessel constrained by her draft, a sailing vessel, a vessel engaged in fishing, or a vessel towing or pushing. Any three of those. Because it was heard apparently forward of your beam, Rule 19(e) requires you to reduce to the minimum speed at which you can be kept on course, take all way off if necessary, and navigate with extreme caution until danger of collision is over. On an "Inland Only" stem, check 33 CFR §83.35 rather than assuming the same signals — and remember the constrained-by-draught class has no Inland counterpart at all.
Check your understanding
One real exam question on Rule 19 — Conduct of Vessels in Restricted Visibility, cited to source. No account.
Rule 19 — Conduct of Vessels in Restricted Visibility
Under both the International and Inland Rules, Rule 19 applies to vessels ______.
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