Maneuvering and Warning Signals: Intent Inland, Action International

What the rule requires

Every signal in this rule is gated on the vessels being in sight of one another. That phrase is the switch. If you cannot see her — she is a radar contact, or a fog signal somewhere ahead — nothing in Rule 34 has been triggered yet, and an exam option that has you sounding a Rule 34 signal at a vessel you cannot see is wrong on that ground alone. Contrast the steering and sailing rules of Section I, which COLREGs Rule 4 applies in any condition of visibility.

Inland adds three more conditions on top of "in sight." Under 33 CFR §83.34 the maneuvering signals of paragraph (a) apply when power-driven vessels are in sight, meeting or crossing, and within half a mile of each other, each vessel underway and maneuvering as authorized or required by the Rules. All four conditions must hold. The half-mile figure is arbitrary and carries no derivation; commit it to memory as the Inland trigger distance.

International has no distance figure. Under COLREGs Rule 34 the signals apply when vessels are in sight of one another and a power-driven vessel underway is maneuvering as authorized or required by the Rules. Nothing about meeting, crossing, or how far off she is.

What the blasts mean

The counts are the same under both regimes. The meanings are not.

Inland :

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"

International :

One short blast — "I am altering my course to starboard"
Two short blasts — "I am altering my course to port"
Three short blasts — "I am operating astern propulsion"

The standard framing is the one to carry into the exam room: Inland signals are signals of intent, International signals are signals of action. Inland you are proposing a passing arrangement and the other vessel answers it. International you are reporting what your rudder is already doing, and the text of paragraph (a) attaches no answering signal at all.

Three short blasts is the one line that reads identically in both. Its meaning is astern propulsion — the engine, not the vessel's motion over the ground.

Inland waters, you are meeting a tug fine on your port bow and sound two short blasts. What have you told her?

That you intend to leave her on your starboard side, which is a starboard-to-starboard passing. Under Inland Rules the blasts describe which side of you she will end up on, not which way your wheel is going over. The same two blasts offshore would mean "I am altering my course to port."

The Inland exchange, and the danger signal

Inland, a signal of intent has to be answered. On hearing the one or two blast signal of the other vessel, a vessel in agreement sounds the same whistle signal and takes the steps necessary to effect a safe passing. If from any cause she doubts the safety of the proposed maneuver, she sounds the doubt signal of paragraph (d), and each vessel shall take appropriate precautionary action until a safe passing agreement is made .

There is no third option in the text. Agreement, or doubt. A vessel answering one short blast with two short blasts has not made a counter-proposal recognized by the rule.

The doubt signal — the danger signal — is at least five short and rapid blasts on the whistle, sounded immediately by the vessel in doubt when vessels in sight of one another are approaching and 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. It may be supplemented by a light signal of at least five short and rapid flashes. Note "at least": five is the floor, not the number.

Overtaking, Inland

The overtaking signals reuse the one and two short blast counts with a third set of meanings, and this is where a rushed candidate loses a mark. Under a power-driven vessel intending to overtake another power-driven vessel signals:

One short blast — "I intend to overtake you on your starboard side"
Two short blasts — "I intend to overtake you on your port side"

The meaning is stated from the overtaken vessel's perspective. One blast puts you up her starboard side. The vessel about to be overtaken, if in agreement, sounds a similar signal; if in doubt, she sounds the danger signal.

The prolonged blasts

Two situations in the Inland rule call for one prolonged blast, and neither is a maneuvering signal:

Nearing a bend, or an area of a channel or fairway where other vessels may be obscured by an intervening obstruction — one prolonged blast, answered with a prolonged blast by any approaching vessel that may be within hearing around the bend or behind the obstruction.
Leaving a dock or berth under power — one prolonged blast.

The bend signal is not gated on seeing anybody. That is its whole purpose: you sound it because the vessel you would need to signal is behind the point.

Light signals

Both regimes permit whistle signals to be supplemented by light signals with the same one, two and three flash meanings as the whistle, each flash of about one second. The equipment specification is where they part, and the exam tests the numbers.

Inland — one all-round white or yellow light, minimum range 2 miles, synchronized with the whistle .
International — an all-round white light, minimum range 5 miles, with the interval between flashes about one second and the interval between successive signals not less than 10 seconds .

Yellow is lawful for this purpose Inland only. Both are permissive: a vessel may supplement, and both refer the fitting back to Annex I.

Radiotelephone agreement, and multiple whistles

A vessel that reaches agreement with another vessel in a head-on, crossing or overtaking situation — for example by radiotelephone under the Vessel Bridge-to-Bridge Radiotelephone Act — is not obliged to sound the whistle signals prescribed by the rule, but may do so. If agreement is not reached, whistle signals shall be exchanged in a timely manner and shall prevail .

Where whistles are fitted more than 100 meters apart on one vessel, only one whistle is used for maneuvering and warning signals.

Telling it apart

The criterion that separates these signals is the trigger — the condition that switches each one on. Sort them by trigger and the exam options separate themselves.

Maneuvering signals, one or two short blasts — trigger is a maneuver by a power-driven vessel in sight of another; Inland adds meeting or crossing within half a mile. Most often misfiled: sounded Inland at a vessel three quarters of a mile off, or treated as required for a vessel being overtaken.
Three short blasts — trigger is operating astern propulsion, both regimes. Misfiled as "I am making sternway."
Danger signal, at least five short and rapid blasts — trigger is vessels in sight and approaching, plus failure to understand or doubt that sufficient action is being taken. Misfiled as a restricted-visibility signal.
One prolonged blast — trigger is nearing a bend or obscured area of a channel or fairway, or, Inland, leaving a dock or berth. No in-sight requirement. Misfiled as an answer to a maneuvering signal.
Attention signals — trigger is the need to attract another vessel's attention. Under COLREGs Rule 36 the signal must be one that cannot be mistaken for any signal authorized elsewhere in the Rules, the searchlight beam may be directed toward the danger in a way that does not embarrass any vessel, any light used must not be mistakable for an aid to navigation, and high intensity intermittent or revolving lights such as strobes are to be avoided. That prohibition on ambiguity is what keeps Rule 36 from being an alternative danger signal.
Distress signals — trigger is a vessel in distress requiring assistance, using or exhibiting the signals in Annex IV COLREGs Rule 37.

Working a question

You are on a 78-foot passenger vessel, power-driven, on inland waters. A tug and tow is fine on your port bow at four tenths of a mile, closing on a near-reciprocal heading. You want the ordinary port-to-port passing.

Fix the regime. Inland waters, so 33 CFR §83.34 governs and the signals are signals of intent.
Test the trigger. Both vessels power-driven, in sight of one another, meeting, and inside half a mile. Paragraph (a) is switched on. At one and a half miles it would not have been.
Choose the signal by the outcome you want, not by your rudder. Port to port means she finishes on your port side, so the signal is one short blast.
Read her answer. One short blast back is agreement, and both of you then take the steps necessary to effect a safe passing. Two short blasts back is not a lawful answer to your proposal. Five or more short and rapid blasts is her doubt signal, and at that point neither of you may stand on: you both take appropriate precautionary action until a safe passing agreement is made.
If you had already agreed by VHF, the whistle signals were not obliged, though you could sound them anyway. Had the radio exchange broken down without agreement, whistle signals must then be exchanged in a timely manner and they prevail over anything said on the radio.

Shift the same geometry offshore and the answer changes at step 3. Under COLREGs Rule 34 you sound one short blast because you are altering your course to starboard, and you sound it as you put the wheel over rather than as a proposal awaiting a reply.

Where candidates lose the point

Carrying the International meaning into an Inland question. "One short blast means I am altering to starboard" is drilled into most candidates first, and it is the wrong answer to any question labelled Inland Only, where the same blast means "I intend to leave you on my port side" 33 CFR §83.34. Check the label before reading the options.

Applying the half-mile threshold everywhere. It belongs to Inland paragraph (a) and to nothing else. The Inland danger signal, the overtaking signals and the bend signal carry no distance figure, and International has no distance figure at all COLREGs Rule 34.

Answering a whistle signal with the opposite signal. A candidate who dislikes the proposed passing reaches for two blasts in reply to one. The rule offers the same signal if in agreement, or the danger signal if in doubt .

Sounding five blasts at a fog signal. The vessel ahead in fog is not in sight of you, and paragraph (d) requires vessels in sight of one another and approaching. An option reading "maintain speed and sound five short and rapid blasts" fails twice over, and the correct conduct comes from the restricted-visibility rule rather than from this one.

Reading the Inland overtaking signal from your own side. One short blast when overtaking means you will pass up her starboard side, not yours.

Treating a radio agreement as a bar on whistle signals. Paragraph (h) removes the obligation, not the permission.

Answering 5 miles for the Inland flashing light. Inland is 2 miles and may be white or yellow; 5 miles and white is International.

Check yourself

(Inland Only) You are meeting another power-driven vessel head-on at one mile. Are you required to sound a whistle signal?

No. Inland paragraph (a) applies to power-driven vessels in sight and meeting or crossing within half a mile of each other. At one mile the trigger has not been met 33 CFR §83.34.

(International Only) You put your wheel over to port to open the CPA on a vessel in sight two miles off. What whistle signal, if any?

Two short blasts, meaning "I am altering my course to port." The rule requires the signal of a power-driven vessel underway maneuvering as authorized or required by the Rules when vessels are in sight of one another, with no distance qualification and no answering signal called for COLREGs Rule 34.

(Inland Only) You sound one short blast to a vessel you are meeting. She answers with five short and rapid blasts. What must you do?

She has signalled doubt as to the safety of your proposed maneuver. Each vessel takes appropriate precautionary action until a safe passing agreement is made. You do not proceed with the passing on the strength of your own signal .

You are approaching a bend in a river where an outbound vessel would be hidden behind the point. What is the signal, and who answers it?

One prolonged blast, answered with a prolonged blast by any approaching vessel within hearing around the bend or behind the intervening obstruction. Nothing here depends on the other vessel being in sight .

(Inland Only) You intend to overtake a fishing vessel under power and pass up her port side. First signal?

Two short blasts, meaning "I intend to overtake you on your port side." If she agrees she sounds a similar signal; if in doubt she sounds at least five short and rapid blasts .

You wish to attract the attention of a vessel standing into danger. May you use a strobe light?

No. High intensity intermittent or revolving lights such as strobes are to be avoided, and any attention signal must be one that cannot be mistaken for a signal authorized elsewhere in the Rules or for an aid to navigation. Directing a searchlight beam toward the danger is permitted, provided it does not embarrass any vessel COLREGs Rule 36.

Your vessel is fitted with a supplementary maneuvering light. What colour and what range satisfies the Inland rule, and how does the International specification differ?

Inland: one all-round white or yellow light, minimum range 2 miles, synchronized with the whistle . International: an all-round white light, minimum range 5 miles, with not less than 10 seconds between successive signals . Flash duration is about one second under both.