What sound signal should be used when in doubt of another vessels intention while passing through a narrow channel?

Section 1 — Conduct of Vessels in any Condition of Visibility

Rule 9 : Narrow Channels

Two terms are used throughout the Rule that are not defined. They are “narrow channel” (namesake of the Rule) and “(narrow) fairway.” We must assume that the drafters of the Rules either believed their meanings to be obvious or else were not able to formulate suitable concise definitions.

Rule 9 applies only on waters described by the two terms. What is “narrow” depends on the type of vessel and the circumstances. A “channel” is a natural or dredged lane restricted on either side by shallow water; it is often marked by buoys. A “fairway” is generally in open water, and the water on either side is not much shallower than within the fairway. Fairways are used to route vessels away from natural hazards, oil platforms, mines, or smaller vessels. Fairways should be differentiated from the lanes in traffic separation schemes; vessels in the latter should follow Rule 10 rather than Rule 9.

a. A vessel proceeding along the course of a narrow channel or fairway shall keep as near to the outer limit of the channel or fairway which lies on her starboard side as is safe and practicable.

No ambiguity in this part of the Rule, it is a general advice. As safe and practicable leaves it to the watch keeping officer to take the ultimate decision to deviate from this Rule. If due to the draft or width of the ship as well as the contour of the bottom of the channel it is not safe or is not practicable to comply with this Rule then the watch keeper has his common sense to guide him, keeping always safety in mind.

b. A vessel of less than 20meters in length or a sailing vessel shall not impede the passage of a vessel which can safely navigate only within a narrow channel or fairway.

Related Article: Rule 24 - Towing and pushing

This again is a guideline for small vessels as well as for sailing crafts to keep away from ships that can safely navigate only within the narrow channel or fairway, since the small vessels and the sailing craft can always use the shallower part of the channel they should not impede the passage of a large ship.

c. A vessel engaged in fishing shall not impede the passage of any other vessel navigating within a narrow channel or fairway.

Also a guideline, again please note it is not a fishing vessel but a fishing vessel engaged in the actual task of fishing, so no fishing in the narrow channel or fairway.

d. A vessel shall not cross a narrow channel or fairway if such crossing impedes the passage of a vessel which can safely navigate only within such channel or fairway. – The latter vessel may use the sound signals prescribed in rule 34 (d) if in doubt as to the intention of the crossing vessel.

Crossing vessels are warned not to cross the channel or fairway if this crossing should come in the way of a vessel proceeding along the channel who cannot deviate due to the depth or width restriction of the channel.

Sound signals have been mentioned which may be used if in any doubt about the intention of either vessel.

It does say that a vessel will not cross a channel or fairway – she can do so as long as she does not impede the passage of a ship following the channel.

(i) In a narrow channel or fairway when overtaking can take place only if the vessel to be overtaken has to take action to permit safe passage, the vessel intending to overtake shall indicate signal prescribed in rule 34 c (i). The vessel to be overtaken shall, if in agreement, sound the appropriate signal prescribed in rule 34 c (ii) and take steps to permit safe passing. If in doubt she may sound the signals prescribed in rule 34 d.

Related Article: Rule 22 - Visibility of lights

In a narrow channel or fairway overtaking may prove to be difficult, but it may be necessary for some reason, ship behind gets a priority berthing etc. In this case, if the vessel behind wants to overtake then she has to sound the signal – 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”.

This is a request signal and has to be answered by the ship ahead either in the affirmative by sounding –One prolonged, one short, one prolonged and one short blast, and the ship ahead should go to one side of the channel and allow sea room for the other ship to overtake.

Only once the confirmation has been received can the ship behind take action. If the answer was positive and overtaking has been permitted then she should first watch the other ship and when the passage has been widened for her she should overtake.

If the ship ahead is in any doubt about the sound signal that she heard or at a later stage while overtaking is in progress and she feels that a close quarter situation may develop then she may sound the signal:- at least five short and rapid blasts on the whistle.

(ii) This rule does not relieve the overtaking vessel of her obligation under rule 13.

Okay so the ship ahead has agreed to be overtaken, but the responsibility and obligation as per Rule 13 still remains on the ship behind, she cannot find fault with the ship ahead if some mishap occurs. This is the reason that she has to make sure that after answering in the positive the ship ahead has made adequate sea room available for her to overtake. Otherwise, even if the sound signal is positive she should not overtake, if in doubt she may sound the signal again.

Related Article: Rule 10 - Traffic separation schemes

f. The vessel nearing a bend or an area of a narrow channel or fairway where other vessels may be obscured by an intervening obstruction shall navigate with particular alertness and caution and shall sound the appropriate signal prescribed in rule 34 e.

Almost like a car sounds a car horn when nearing a crossing, it alerts traffic on the blind side of the bend that a ship is about to cross. This is especially relevant in channels and rivers and fairways where up and down traffic are numerous.

g. Any vessel shall, if the circumstances of the case admit, avoid anchoring in a narrow channel.

A general advice, circumstances of the case admit means as far as possible she should not anchor, but if due to some extraordinary circumstances she has to anchor then she should have to warn all vessels and take special care.

When your vessel is underway and you can see other vessels, you can use sound signals to let other vessels know your intended movements. For example, if you plan to alter course or are slowing down. These signals can help prevent collisions.

Powerboats and sailing boats must carry a sound signal device – such as an air horn, bell or whistle – as part of their safety equipment.

The signals can be in short or long blasts. A short blast is about 1 second and a long blast is 4 to 6 seconds.

You can accompany these sound signals with light signals.

In busy and restricted waterways, large vessels use sound signals to notify nearby boats of their intentions. Sound signals are used to signal intentions on the waterways like an automobile's turn light indicators on the highways. All boaters should know proper sound signals, especially those boaters operating near commercial vessel traffic. If you are unaware of the signal communications it may become problematic and place your vessel and surrounding craft in jeopardy. The following regulations are for vessels operating in the British Isles and covered by the The Merchant Shipping (Distress Signals and Prevention of Collisions) Regulations 1996 November 2003 - see Rules 34/35 extract . These are the same ones agreed to internationally and used on the high seas. Unfortunately some countries may have different inland water regulations, for example in the United States of America for instance, they reverse the port and starboard signals and have different overtaking signals. These are noted by dashed magenta lines found on many charts and labelled COLREGS DEMARCATION LINES which are the boundaries of restricted-navigation zones. To seaward of these lines, or where the lines do not exist, a skipper must follow the International rules - more formally known as the 1972 International Regulations for Preventing Collisions at Sea (72 COLREGS). Where these lines exist, and inshore of them, a skipper must use the specific Inland Waterway Rules.

REQUIRED SIGNALING EQUIPMENT

Rule 33, equipment for sound signals, specify three devices used for sound signalling.

A compressed air 'Air horn' is vital to the safety of a vessel
Photo: Courtesy of Lauzas

These are a gong, a bell and a whistle that need to comply with the technical details for sound signal appliances set out in Annex III of the COLREGs:

• A vessel of 12 metres or more in length shall be provided with a whistle

• A vessel of 20 metres or more in length shall, in addition, be provided with a bell

• A vessel of 100 metres or more in length shall, in addition, be provided with a gong

The rules do not oblige a vessel of less than 12 metres in length to carry a specially prescribed sound-signalling appliance. It states that it must have the means to produce some type of sound. The prudent mariner should subscribe to the rules and carry an appropriate horn, even if it's only a portable air horn priced under £10.

SIGNAL TYPE

In a little more detail, marine regulations specify that a vessel of twelve metres or more in length must have sound signalling capabilities. A vessel of less than twelve metres is not obliged to carry sound signalling equipment as long as they are enabled with some other means of signalling.Sound signals are of two kinds, a short blast or a prolonged blast:

A short blast = a blast of about one second's duration.

A prolonged blast = a blast of from four to six seconds' duration.

These are used to define the type of manoeuvre summarised in the image below which would be good to have printed and to hand when in busy waterways.

SOUND SIGNALS COMMUNICATING A CHANGE IN DIRECTION

The following sound signals are used when vessels are in sight of one another and meeting or crossing within half a mile of each other:

One short blast = "I intend to leave you on my port side"

Two short blasts = "I intend to leave you on my starboard side"

Three short blasts = "I am operating astern propulsion"

Five short and rapid blasts = "Danger signal, I do not understand your intentions"

Four short blasts, a short interval and one short blast = "I intend to turn about to Starboard (turn vessel through more than 135°)"

Four short blasts, a short interval and two short blasts = "I intend to turn about to Port (turn vessel through more than 135°)".

It is important to observe that the operating astern signal refers to the shaft and propeller, not to the actual motion of the vessel which can be either forward or astern.

POWER DRIVEN VESSELS IN A NARROW CHANNEL

The following sound signals are used when vessels are in sight of one another in a narrow channel or fairway:

Two prolonged blasts followed by one short blast

Two prolonged blasts followed by two short blasts = “I intend to overtake you on your
port side”

If in agreement with these manoeuvres you should acknowledge by the following signal:

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

Conversely, if the vessel being overtaken is in doubt about the safety of the proposed manoeuvre, or you doubt whether sufficient action is being taken to avoid a collision, you should signal the above five short and rapid blasts of the danger signal to indicate that their intentions are unclear.Lights have the same sequence with the duration of each flash at about one second. The light should be an all-round white or yellow that is visible for about two miles synchronized with a sound signal.The other times that a vessel is likely to use a sound signal is when they are nearing a bend or an area of a channel or fairway where other vessels may be obscured from their view. At these times they sound a single prolonged blast. This signal should be answered with a prolonged blast to indicate your presence. When a power-driven vessel is leaving a dock or berth they also sound one prolonged blast.

One prolonged blast = "I am making vessels aware of my presence"

SOUND SIGNALS IN RESTRICTED VISIBILITY

Sounds on the water are many and varied. Bells, gongs, fog horns, boat whistles all combine to produce a confusing cacophony. The above Rule 33 objective, the different types and variety of devices used by the various classes of vessel, is to enable mariners to detect the scale of the vessel by the sound it makes when heard through the dark of a foggy night. A vessel underway must give one prolonged foghorn horn blast every two minutes. If motoring, you may have to turn off the engine at regular intervals to listen to hear the echo. You should also be listening for the sound signal of other vessels or navigation aids. Sound signals are either prolonged, four to six seconds; or short, one second. A bell can be sounded as a single ring or as a rapid ringing for five seconds, and a gong is rung rapidly. The meaning of the signals for boating are as follows:

• Under sail (and some other vessels): One prolonged foghorn horn blast and two short blasts every two minutes

• Making way under power: One prolonged blast every two minutes.

• Under way but stopped: Two long blasts with an interval of about 2 seconds between them at two-minute intervals.

• Aground - under 100m (328ft): Three bells, rapid ringing, three bells, at one-minute intervals.

• Aground - over 100m (328ft): Three bells, rapid ringing, three bells, a gong sounded aft, every minute.

• At anchor - under 100m (328ft): Rapid ringing of bell in the forepart of the boat for 5 seconds, at one-minute intervals.

• At anchor - over 100m (328ft): Rapid ringing of bell in the forepart of the boat for 5 seconds, at one-minute intervals 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.

• Pilot boat on duty: Four short blasts (after underway or making way) every two minutes.

Navigational aids, such as buoys and lighthouses, are also fitted with maritime sound signal apparatus so that they can be identified.

Do not assume a direction for the maritime horn signal as it can be distorted by fog so stop and double-check the direction then proceed with caution.

See also maritime flags and their meaning

Michael Harpur, Yacht Obsession.

Sound signal rules to be followed by vessels in restricted visibility 1

Sound signal rules to be followed by vessels in restricted visibility 2

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Matt Reid wrote this review on Dec 31st 2013:
The signals outlined above are not quiet correct. One short blast means "I am altering course to starboard" Two short blasts means "I am altering course to port" When overtaking these signals are preceded by two long blasts to indicate the intention to overtake as shown in rule 34. Rule 34 (c) When in sight of one another in a narrow channel or fairway: (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.

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Michael Harpur wrote this review on Jan 26th 2018:
Thank you Matt. I have now edited this to the letter of the law and also added links back to 'The Merchant Shipping (Distress Signals and Prevention of Collisions) Regulations 1996'. Any further suggestions please do not hesitate.

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