Sound signals and restricted visibility

Hearing what you can’t see

In the last two lessons you learned who gives way to whom, and how to recognise a vessel and what she is doing by her lights and shapes. All of that depends on seeing her. In fog, mist, falling snow or a heavy rainstorm you may not see another vessel until she is dangerously close — but you can usually hear her. The collision regulations (the COLREGs) give every vessel a small language of sound for this, set out in Part D of the rules, Rules 32 to 37. This lesson covers those signals, and Rule 19: how to behave when you can’t see.

The rules call any appliance that can make the right blasts a whistle. On a ship it is a powerful horn; on a yacht it is usually an aerosol foghorn, a hand-held horn or an electric one. Every whistle signal is built from just two lengths of blast (Rule 32):

The timelines and the player in this lesson are drawn to scale: a short blast as 1 second and a prolonged blast as 5, the middle of its range. That lets you see the rhythm as well as count the blasts. Where the rules don’t fix the gap between blasts, about a second is used.

Every vessel of 12 metres or more must carry a whistle; from 20 metres a bell as well, and from 100 metres a gong too (Rule 33). A vessel under 12 metres isn’t obliged to carry these, but must have some other means of making an efficient sound signal — so every yacht needs a foghorn of some kind, kept where you can reach it.

Manoeuvring and warning signals (Rule 34)

When vessels are in sight of one another, a power-driven vessel underway that manoeuvres as the rules allow or require must say so on her whistle:

The signal is made as she manoeuvres, so it tells you what she is doing now, not what she might do later. She may back it up with flashes of an all-round white light — one, two or three flashes, with the same meanings — repeated while the manoeuvre goes on.

Overtaking in a narrow channel

In a narrow channel or fairway, sometimes you can only overtake if the vessel ahead moves over to make room. Then the vessel that wants to overtake must ask first (Rules 9 and 34), and the vessel ahead answers:

If the vessel ahead is in doubt, she may sound the doubt signal (below) instead. Agreement doesn’t change the overtaking rule from Lesson 20: the overtaking vessel must still keep out of the way.

Doubt: at least five short and rapid blasts

When vessels in sight of one another are approaching each other and either of them can’t understand what the other is doing, or doubts that the other is doing enough to avoid a collision, the vessel in doubt must at once sound at least five short and rapid blasts. It may be backed up by at least five short and rapid flashes. It is often called the wake-up signal, and it applies to every vessel, sail or power.

Blind bends

A vessel nearing a bend, or any part of a channel where other vessels may be hidden behind an obstruction, sounds one prolonged blast. Any vessel approaching from the other side that hears it answers with one prolonged blast.

Fog signals (Rule 35)

Restricted visibility means any condition in which visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms or similar causes (Rule 3). In or near an area of restricted visibility — by day or by night — vessels sound fog signals. “Near” matters: in clear air beside a fog bank, vessels inside it need to hear you.

• NUC, RAM and CBD are a vessel not under command, restricted in her ability to manoeuvre and constrained by her draught — the vessels you met by their lights and shapes in Lesson 21.
• A vessel being towed sounds her signal, when practicable, straight after the towing vessel’s.
• At anchor, the bell is rung rapidly for about 5 seconds. A vessel of 100 metres or more rings it forward, then sounds a gong aft for about 5 seconds.
• Aground, a vessel gives three separate and distinct strokes on the bell, the rapid ringing, then three more distinct strokes.

You may also hear these:

• A vessel at anchor may add one short, one prolonged and one short blast (• — •) to warn an approaching vessel of her position and of the possibility of collision.
• A pilot vessel on duty may add an identity signal of four short blasts (• • • •) to her normal signal.
• A vessel fishing at anchor, or a RAM vessel at anchor doing her work, sounds — • • instead of the anchor bell.
• A pushing vessel and the vessel she pushes, rigidly connected as one unit, count as a power-driven vessel.

Conduct in restricted visibility (Rule 19)

Rule 19 applies to vessels not in sight of one another when navigating in or near an area of restricted visibility. It says:

1. Safe speed. Every vessel must proceed at a safe speed adapted to the circumstances and the conditions of restricted visibility. A power-driven vessel must have her engines ready for immediate manoeuvre.
2. The general rules still apply, with due regard to the visibility: keep a proper lookout by sight and hearing and by every available means, judge whether risk of collision exists, and act in good time.
3. Radar alone. A vessel that detects another by radar alone must decide whether a close-quarters situation is developing or risk of collision exists. If so, she must take avoiding action in ample time. If that action is an alteration of course, then so far as possible she must avoid:
   • an alteration to port for a vessel forward of the beam, other than one she is overtaking; and
   • an alteration towards a vessel abeam or abaft the beam.
4. A fog signal forward of the beam. Unless it has been established that there is no risk of collision, a vessel that hears the fog signal of another apparently forward of her beam, or can’t 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 her course. She must take all her way off if necessary, and in any event navigate with extreme caution until the danger of collision is over.

In fog there is no stand-on vessel. Everyone slows down, listens, and acts early.

That follows from how the rules are built. The rules for overtaking, head-on and crossing situations, and for who keeps out of whose way, apply only to vessels in sight of one another. Until you can see each other, neither of you stands on: each must take action to avoid a close-quarters situation. Once you are in sight, the ordinary rules apply again.

Slowing down — or stopping — is avoiding action too, and for a vessel ahead it is often the best choice, because it gives everyone more time. Whatever you do, do it early and make it large enough to show clearly on the other vessel’s radar: a series of small alterations is hard for her to see.

A fog routine for a yacht

Beyond the rules themselves, good seamanship — what Rule 2 calls the ordinary practice of seamen — adds a routine for when visibility closes in. A yacht is small, quiet and a poor radar target, so most of it is about knowing where you are and making sure others know you are there.

1. Fix your position while you still can, write it in the log with the time and log reading, and keep a DR or EP going from it (Module 2).
2. Hoist the radar reflector as high as you can, if it isn’t permanently fitted. Switch on the navigation lights, and the radar and AIS if you have them.
3. Start your fog signal — the right one for what you are doing — and keep it going.
4. Life jackets on for everyone on deck, and keep the horn and the VHF within reach.
5. Post a lookout who listens as well as looks, ideally in the bow, away from the engine noise. Stopping the engine now and then to listen helps.
6. Think about where to be. Keep out of shipping lanes, and consider heading for shallow water where big ships can’t go — and, if it is safe, anchoring there until the fog lifts.

Attracting attention and distress (Rules 36 and 37)

If you need to attract another vessel’s attention, any vessel may make light or sound signals that can’t be mistaken for any signal in the rules, or shine a searchlight in the direction of the danger, as long as it doesn’t hamper other vessels. High-intensity flashing or revolving lights, such as strobes, should be avoided for this.

A vessel in distress uses the distress signals listed in Annex IV of the rules. One of them is a continuous sounding with any fog-signalling apparatus — so a horn held down without stopping means “I need help”, not just “I am here”.

Module 3 in one breath

That completes Module 3: buoyage, lights, and the rules of the road. Signals in sight say what you are doing; fog signals say what you are; and Rule 19 says how to behave when you can’t see.