Give the manoeuvring and warning signals of Rule 34.

Rule 34 (power-driven, in sight, manoeuvring as authorised/required): one short — 'I am altering to starboard'; two short — 'altering to port'; three short — 'operating astern propulsion'. Overtaking in a narrow channel (34(c)): two prolonged + one short — 'intend to overtake on your starboard'; two prolonged + two short — 'on your port'; vessel to be overtaken agrees with prolonged–short–prolonged–short (Morse 'C'). Doubt (34(d)): at least five short and rapid blasts — may be supplemented by five short flashes. Bend (34(e)): one prolonged on approaching a blind bend, answered by one prolonged. Lead: 1/2/3 short for helm; five short for doubt; one prolonged at a blind bend.

In fog you alter course to starboard for a radar contact. Do you sound one short blast?

No — Rule 34 manoeuvring signals apply only to vessels IN SIGHT of one another. In restricted visibility you are under Rule 35 (fog signals), not Rule 34. Sounding 'one short' for a contact you cannot see would be meaningless and wrong. Trap: manoeuvring signals need visual contact; fog signals do not.

You are unsure the other vessel understands your intentions. Which signal, and does altering course excuse you from it?

Rule 34(d): at least five short and rapid blasts — the doubt signal — used whenever you doubt the other's intentions or that she is taking sufficient action. Taking your own avoiding action does not replace it; if in doubt, sound it (and you may add five short flashes). Lead: when in doubt, five short — say so, don't just manoeuvre silently.

Part D · Sound and light signals

COLREGS Rule 34 — Manoeuvring and Warning Signals

Q: What does the five-short-blast signal mean and when is it used?

Rule 34(d): the 'doubt' or 'wake-up' signal — at least five short and rapid blasts, used when either vessel fails to understand the intentions or actions of the other, or is in doubt whether sufficient action is being taken to avoid collision. It may be supplemented by at least five short and rapid flashes of light. Lead: 'I don't understand what you're doing / I doubt you're doing enough.'

(a) When vessels are in sight of one another, a power-driven vessel underway, when manoeuvring as authorized or required by these Rules, shall indicate that manoeuvre by the following signals on her whistle:

- one short blast to mean 'I am altering my course to starboard ';

- two short blasts to mean 'I am altering my course to port ';

- three short blasts to mean 'I am operating astern propulsion'.

(b) Any vessel may supplement the whistle signals prescribed in paragraph (a) of this Rule by light signals, repeated as appropriate, whistle the manoeuvre is being carried out:

(i) these light signals shall have the following significance:

- one flash to mean 'I am altering my course to starboard ' ;

- two flashes to mean 'I am altering my course to port ' ;

- three flashes to mean 'I am operating astern propulsion' ;

(ii) the duration of each flash shall be about one second, the interval between flashes shall be about one second, and the interval between successive signals shall be not less than ten seconds;

(iii) the light used for this signals shall, if fitted, be an all-round white light, visible at a minimum range of 5 miles and shall comply with the provisions of Annex I to these Regulations.

(i) a vessel intending to overtake another shall in compliance with Rule 9(e)(i) indicate her intention by the following signals on her whistle :

- two prolonged blasts followed by one short blast to mean 'I intend to overtake you on your starboard side' ;

- two prolonged blasts followed by two short blasts to mean 'I intend to overtake you on your port side' ;

(ii) the vessel about to be overtaken when acting in accordance with Rule 9(e)(i) shall indicate her agreement by the following signal on her whistle:

- one prolonged, one short, one prolonged and one short blast, in that order.

(d) When vessels in sight of one another are approaching each other and from any cause either vessel fails to understand the intentions or actions of the other, or is in doubt whether sufficient action is being taken by the other to avoid collision, the vessel in doubt shall immediately indicate such doubt by giving at least five short and rapid blasts on the whistle. Such signal may be supplemented by a light signal of at least five short and rapid flashes.

(e) A vessel nearing a bend or an area of a channel or fairway where other vessels may be obscured by an intervening obstruction shall sound one prolonged blast. Such signal shall be answered with a prolonged blast by any approaching vessel that may be within hearing around the bend or behind the intervening obstruction.

(f) If whistles are fitted on a vessel at a distance apart of more than 100 metres, one whistle only shall be used for giving manoeuvring and warning signals.

COLREGS Rule 34 — Manoeuvring and Warning Signals

All COLREGS Rules and Annexes

Part A · General

Part B · Steering and sailing rules

Part C · Lights and shapes

Part D · Sound and light signals

Part E · Exemptions

Part F · Verification of compliance

Annex I · Positioning and technical details of lights and shapes

Annex II · Additional signals for fishing vessels fishing in close proximity

Annex III · Technical details of sound signal appliances

Annex IV

Also free for seafarers

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