What to do in restricted visibility if a fog signal is heard apparently forward of the beam?

In or near an area of restricted visibility, whether by day or night, the signals prescribed in this Rule shall be used as follows:

(a) A power-driven vessel making way through the water shall sound, at intervals of not more than 2 minutes, one prolonged blast.

(b) A power-driven vessel underway but stopped and making no way through the water shall sound, at intervals of not more than 2 minutes, two prolonged blasts in succession, with an interval of about 2 seconds between them.

(c) A vessel not under command; a vessel restricted in her ability to maneuver, whether underway or at anchor; a sailing vessel; a vessel engaged in fishing, whether underway or at anchor; and a vessel engaged in towing or pushing another vessel shall, instead of the signals prescribed in paragraphs (a) or (b) of this Rule, sound, at intervals of not more than 2 minutes, three blasts in succession, namely, one prolonged followed by two short blasts.

(d) [Reserved]

(e) A vessel towed or if more than one vessel is towed the last vessel of the tow, if manned, shall at intervals of not more than 2 minutes sound four blasts in succession, namely, one prolonged followed by three short blasts. When practicable, this signal shall be made immediately after the signal made by the towing vessel.

(f) When a pushing vessel and a vessel being pushed ahead are rigidly connected in a composite unit they shall be regarded as a power-driven vessel and shall give the signals prescribed in paragraphs (a) or (b) of this Rule.

(g) A vessel at anchor shall at intervals of not more than 1 minute ring the bell rapidly for about 5 seconds. In a vessel of 100 meters or more in length the bell shall be sounded in the forepart of the vessel and immediately after the ringing of the bell the gong shall be sounded rapidly for about 5 seconds in the after part of the vessel. A vessel at anchor may in addition sound three blasts in succession, namely, one short, one prolonged and one short blast, to give warning of her position and of the possibility of collision to an approaching vessel.

(h) A vessel aground shall give the bell signal and if required the gong signal prescribed in paragraph (g) of this Rule and shall, in addition, give three separate and distinct strokes on the bell immediately before and after the rapid ringing of the bell. A vessel aground may in addition sound an appropriate whistle signal.

(i) A vessel of 12 meters or more but less than 20 meters in length shall not be obliged to give the bell signals prescribed in paragraphs (g) and (h) of this Rule. However, if she does not, she shall make some other efficient sound signal at intervals of not more than 2 minutes.

(j) A vessel of less than 12 meters in length shall not be obliged to give the above-mentioned signals but, if she does not, shall make some other efficient sound signal at intervals of not more than 2 minutes.

(k) A pilot vessel when engaged on pilotage duty may, in addition to the signals prescribed in paragraphs (a), (b) or (g) of this Rule, sound an identity signal consisting of four short blasts.

(l) The following vessels shall not be required to sound signals as prescribed in paragraph (g) of this Rule when anchored in a special anchorage area designated by the Coast Guard:

(i) A vessel of less than 20 meters in length; and

(ii) A barge, canal boat, scow, or other nondescript craft.

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§ 83.36 Signals to attract attention (Rule 36).

If necessary to attract the attention of another vessel, any vessel may make light or sound signals that cannot be mistaken for any signal authorized elsewhere in these Rules, or may direct the beam of her searchlight in the direction of the danger, in such a way as not to embarrass any vessel.

During periods of restricted visibility (such as rain, mist, heavy fog, or hours of darkness), you should slow to minimum speed to give your vessel an opportunity to maneuver should the risk of a collision arise.

Unless the risk of a collision is present, you should reduce your speed to the minimum you need in order to keep on course when you hear any of the sound signals above.

18/33

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

Meaning that this Rule applies to such vessels that may be close to each other but cannot visually see each other, electronic devices and sound signals may be the only possible means of detection and thus the action that would be taken would not be visible by the other vessel.
The areas are not only in areas of poor visibility but also areas near to that. Meaning that ships should be careful when approaching a fog bank, or an area of poor visibility caused
maybe by any weather or other condition.

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 manoeuvre.

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 in 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;

Related Article:   Rule 21- Definitions

Meaning: In restricted visibility when the vessels cannot see each other as required by the Rules, the above are to be complied with. Of course, alteration of course to Port has been advised against, and it should be followed as far as practicable if the situation deems that an alteration, of course, other than to Port is required then that may be done.- Rule 2, use your head. For overtaking situation after the Risk factor has been assessed the alteration may be done either way.

(ii) An alteration of course toward a vessel abeam or abaft the beam.

Meaning : Here too since the vessels are not in sight of one another and the observations are being carried out by electronic means, the proper assessment of the aspect of the vessel is not obtained, as such the above guidelines.

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 be the minimum at which she can be kept on her course. She shall if necessary take all her way off and in any event navigate with extreme caution until danger of collision is over.

As stated in Rule 3 (l) The term “restricted visibility” means any condition in which visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms or any other similar causes.