Rule 9 Narrow Channels: What Every Skipper Must Know

Narrow channels have a way of concentrating risk. Deep-draught ships are confined to a corridor a few cables wide, small craft cross at odd angles, and everyone arrives at the same pinch point at the same time. Rule 9 of the COLREGS exists to bring order to that situation, and it does so through a short list of clear obligations that every skipper, whatever the size of the vessel, needs to understand cold.

Rule 9 interacts with several other rules in ways that surprise candidates. It does not suspend the stand-on and give-way framework of Rules 15 to 17, but it imposes earlier, independent obligations that shape how that framework operates inside a channel. This article is educational support: it does not replace formal training, your examiner's guidance, or the authoritative COLREGS text, which remains the definitive reference for any certification.

Keep to the Starboard Side

The foundation of Rule 9 is 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. The phrase "as is safe and practicable" is doing real work. The rule does not demand that you hug the edge regardless of shoal water or pot buoys. It demands a genuine effort to stay on the starboard side of the channel, as close to its outer limit as conditions allow.

In practice a yacht threading a buoyed estuary should be favouring the starboard-hand edge of the marked channel, not cruising down the middle because it feels more comfortable. Consistent starboard-keeping creates the predictable separation that makes narrow channels manageable, and every other vessel in the channel is relying on it.

The 'Shall Not Impede' Obligations

Rule 9 places two specific "shall not impede" duties on particular vessels, and understanding them precisely matters both for exams and for real decisions.

First, under Rule 9(b), a vessel of less than 20 metres 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. The phrase "can safely navigate only within" is the key. It refers to a vessel whose draught confines her to the dredged channel. A bulk carrier drawing 14 metres in a channel dredged to 16 metres has nowhere else to go. Your 10-metre sloop has choices she does not have.

Second, under Rule 9(c), a vessel engaged in fishing shall not impede the passage of any other vessel navigating within a narrow channel or fairway. Note the difference in scope: the fishing vessel's duty is owed to any other vessel in the channel, not only to those confined to it. Working pots in a buoyed fairway does not exempt anyone from traffic obligations.

What "shall not impede" means is spelled out in Rule 8(f). Rule 8(f)(i) requires a vessel that must not impede another to take early action, when the circumstances require it, to allow sufficient sea room for the other vessel's safe passage. Rule 8(f)(ii) says the duty is not lifted if the two vessels do approach so as to involve risk of collision; the impeding vessel remains bound by it, with full regard to what the other steering and sailing rules require. Rule 8(f)(iii) says the vessel whose passage is not to be impeded remains fully obliged to comply with the steering and sailing rules once risk of collision exists. Both vessels keep their obligations once close quarters develops, but the vessel with the "shall not impede" duty should never have let things reach that point.

In plain terms, your duty is to stay out of the way early, not to crowd the ship and then invoke Rule 17. If you find yourself in close quarters with a deep-draught vessel inside a narrow channel, you have almost certainly left your action too late.

For sailing skippers this is a significant mental shift. In open water a sailing vessel is often the stand-on vessel: Rule 18(a) requires a power-driven vessel to keep out of her way. Inside a narrow channel a sailing vessel shall not impede a vessel confined to the channel. The rules have not been suspended; they have been supplemented by an earlier obligation that takes precedence. Rule 18 itself opens with the words "except where Rules 9, 10 and 13 otherwise require". You can explore how these obligations interact with crossing, head-on and overtaking situations in the IRPCS rule library.

Crossing a Narrow Channel

Rule 9(d) deals with vessels that need to cross a channel rather than proceed along it. 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 that channel or fairway. The rule then gives the confined vessel a tool: she may use the sound signal prescribed in Rule 34(d), at least five short and rapid blasts, if in doubt as to the intention of the crossing vessel.

Two points follow. The prohibition protects vessels confined to the channel, not every vessel using it. And the doubt signal belongs to the ship, not the crossing vessel: five short blasts from the vessel in the channel mean she cannot tell what you intend. The remedy is to make your intention obvious early, by timing, a bold alteration or a VHF call, and to cross as nearly as practicable at right angles.

Overtaking and Sound Signals

Rule 9(e) covers overtaking, and the first thing to notice is when it applies. Rule 9(e)(i) is engaged when overtaking can take place only if the vessel to be overtaken has to take action to permit safe passing. If there is room to pass without her help, Rule 13 governs and no exchange of signals is required. When her help is needed, the vessel intending to overtake shall indicate her intention by sounding the appropriate signal prescribed in Rule 34(c)(i).

Rule 34(c)(i) prescribes two intention signals. Two prolonged blasts followed by one short blast means "I intend to overtake you on your starboard side". Two prolonged blasts followed by two short blasts means "I intend to overtake you on your port side". Both live in the same sub-paragraph.

The vessel to be overtaken shall, if in agreement, sound the signal prescribed in Rule 34(c)(ii), which is one prolonged, one short, one prolonged and one short blast, in that order, and take steps to permit safe passing. The agreement is conditional: she sounds it if she agrees. If she is in doubt, Rule 9(e)(i) says she may sound the signals prescribed in Rule 34(d), the five or more short and rapid blasts. The doubt signal does not refuse the overtake for ever; it says the manoeuvre cannot happen safely now.

Rule 9(e)(ii) adds the sting in the tail: this rule does not relieve the overtaking vessel of her obligation under Rule 13. An agreed overtake in a narrow channel is still an overtake, and the overtaking vessel remains the give-way vessel throughout.

Rule 34(c) itself opens with the words "when in sight of one another in a narrow channel or fairway", so these are whistle signals for vessels that can see each other. In practice many ports supplement them with VHF, but for exam purposes you must know the whistle sequences. The IRPCS practice quiz includes the Rule 34 signals and will tell you quickly whether they have stuck.

Bends and Blind Corners

Rule 9(f) is easily forgotten. A 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). That signal is one prolonged blast, and any approaching vessel within hearing around the bend answers with one prolonged blast of her own.

Anchoring in a Narrow Channel

Rule 9(g) is short: any vessel shall, if the circumstances of the case admit, avoid anchoring in a narrow channel. This is not a soft recommendation. If there is a practicable alternative, such as moving outside the channel or proceeding to a designated anchorage, the alternative must be taken. Vessels that anchor in fairways for convenience create exactly the obstruction Rule 9 was drafted to prevent.

Putting It All Together

Everyone keeps to starboard. Vessels under 20 metres and sailing vessels do not impede vessels confined to the channel; fishing vessels do not impede any vessel navigating in it; Rule 8(f) demands early action in each case. Nobody crosses in a way that impedes a confined vessel, and she may sound five short blasts if in doubt. Where an overtake needs the other vessel's cooperation, intention is signalled under Rule 34(c)(i), agreement under Rule 34(c)(ii), doubt under Rule 34(d), and Rule 13 still applies. Approaching a blind bend, sound one prolonged blast. Nobody anchors in the channel if it can be avoided. None of this replaces a proper lookout under Rule 5, a safe speed under Rule 6, or the Rule 8 duty to take early and substantial action: Rule 9 is a layer of order over the broader framework, not a replacement for it.

FAQ

Does Rule 9 apply to rivers and estuaries, or only to formally designated channels?

Rule 9 applies to any narrow channel or fairway, not only to those marked on a chart as official thoroughfares. Whether a stretch of water qualifies is a question of fact: does it physically constrain vessels to a defined corridor? Many tidal rivers and buoyed estuaries clearly qualify, and mariners should treat them accordingly whether or not a harbour authority has issued specific directions.

If I am in a sailing vessel and the wind dies, does my 'shall not impede' duty change?

No. The duty in Rule 9(b) attaches to a sailing vessel as such, and a loss of wind does not alter it. A becalmed yacht lying across a fairway while a ship approaches should start her engine or take whatever action is available to clear the channel promptly. Once the engine is driving her she is a power-driven vessel, and her Rule 9(b) duty continues if she is under 20 metres.

Can the overtaking signals be replaced by a VHF agreement?

In many port environments VHF agreement between vessels, or with port control, has become the practical norm, and harbour regulations often support it. For exam purposes, though, you must know the whistle signals, because Rule 9(e)(i) directs vessels to them and Rule 34(c) prescribes them. Relying solely on VHF without knowing the whistle protocol is not sufficient preparation for any certification, and the authoritative COLREGS text should always be consulted for the precise wording.

What happens if a vessel confined to the channel and a crossing vessel both believe they have priority?

Rule 9(d) resolves it: the crossing vessel shall not cross if doing so impedes the confined vessel, and that is an early-action duty. If close quarters does develop, Rule 8(f) keeps both vessels fully bound by the steering and sailing rules, and Rule 17 permits, and ultimately requires, the stand-on vessel to act. The better answer is to resolve the uncertainty long before that point.