There is no widely-accepted definition of a narrow channel. Generally they are natural or dredged passages with shallow water on both sides. A narrow channel for one ship might not be a narrow channel for another though, depending on the draughts of each vessel, so there is a degree of subjectivity. These channels are often buoyed (and in our examples we will show these as being buoyed). Even a harbour mouth can be considered a narrow channel. From the Supreme Court judgement on Evergreen Marine Ltd. v Nautical Challenge Ltd:
Bearing in mind that a narrow channel may include an appropriately narrow harbour entrance
A fairway is like a narrow channel but without the requirement for shallow water on each side. These are in open water, generally in areas of high traffic. They can be designated by local authorities and marked on the chart using broken purple lines (see Chart 5011), may be maintained by a local authority, may feature lateral marks, and may feature a fairway buoy at either end or mid-channel. They route traffic away from hazards.
Relevant documents and M-notices: MGN 1781
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.
This is the ‘keep to the right’ rule. It exists to keep the maximum separation between vessels going in different ways along the channel/fairway and to allow the possibility of passing (more on this later). Keeping as much distance as possible between vessels in a narrow channel is especially important to avoid interaction. It is up to the OOW to decide how far to the starboard side of the channel they are able to keep, based on their own ships manoeuvrability and draught.
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.
Back to impeding. We started to explore this relationship in ‘COLREGS 7: Impeding explained’, but, as a quick reminder:
Impeding is an additional relationship to the relationship that exists in a risk-of-collision situation
Impeding happens long before there is a risk of collision
Impeding is about giving cause for concern
Impeding doesn’t change who is the give-way and who is the stand-on vessel should a risk of collision exist
So the vessel <20m in length/sailing vessel has to decide:
Is that other vessel navigating in a narrow channel or fairway?
Can they only navigate safely within that narrow channel or fairway?
Am I at risk of impeding them (making them think that a risk of collision might develop)?
If the answer is yes to all of the above, they need to take early action to allow sufficient sea-room for the passage of the other vessel.
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 phrasing here compared to Rule 9 (b); any vessel instead of a vessel which can safely navigate only within a narrow channel or fairway.
So the vessel engaged in fishing only has to ask itself:
Is that other vessel navigating in a narrow channel or fairway?
Am I at risk of impeding them?
If yes to both, they need to take early action to allow sufficient sea-room for the passage of the other vessel.
Rule 9 (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 signal prescribed in Rule 34(d) if in doubt as to the intention of the crossing vessel.
If you’re thinking of crossing a narrow channel or fairway, would you, by doing so, impede the passage of a vessel which can safely navigate only within that channel or fairway? If so, don’t. Take early action to allow sufficient sea-room for the passage of the other vessel.
If we are a vessel which can safely navigate only within a narrow channel or fairway and we think that another vessel may be about to cross in a way that would impede us, we may (note the use of may here, rather than shall) sound the sound signal prescribed in Rule 34 (d) to express doubt.
The sound signal in question is at least five short and rapid blasts on the ships whistle. This is sometimes referred to as the ‘wake up!’ signal or the ‘what are you doing?’ signal, as it alerts another vessel to the fact that a vessel is in doubt as to their intentions, or that a vessel doubts they are taking sufficient action to avoid a collision.
Rule 9 (e)
(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 passing, the vessel intending to overtake shall indicate her intention by sounding the appropriate 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).
(ii) This Rule does not relieve the overtaking vessel of her obligation under Rule 13.
when overtaking can take place only
If it is possible to overtake safely without any action on the part of the vessel to be overtake, this rule doesn’t apply and you can overtake as normal. So if you are overtaking in a fairway and have plenty of room to safely do so, no need to sound a signal.
The sound signal that the vessel intending to overtake should sound is two prolonged blasts followed by one short blast if she intends to overtake on the starboard side, or two prolonged blasts followed by two short blasts if she intends to overtake on the port side.
The vessel to be overtaken shall, if in agreement, sound the appropriate signal prescribed in Rule 34 (c)(ii)
This consists of one long, one short, one long and one short blast on the ships whistle (Morse ‘C’; meaning ‘I agree’.


Rule 9 (f)
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).
This is akin to tapping your car horn when going over a blind summit. The sound signal here consists of one prolonged blast (Rule 34 (e)). If there’s another vessel coming the other way, on hearing your signal they must answer with one prolonged blast.
We’ll deal with sound signals in a separate article, however let’s talk about Rule 34(c), (d) and (e) as applied with Rule 9. With the exception of Rule 34 (e), they are only to be sounded by vessels in sight of one another. So, while Rule 9 applies in all conditions of visibility, note that if visibility were such that you couldn’t see the other vessel you wouldn’t you wouldn’t sound these manoeuvring signals. This is why the signals are given as parts of a separate rule rather than being incorporated into Rule 9. Note that the signal for a vessel approaching a bend or an intervening obstruction as per Rule 9 (f) and Rule 34 (e) is the same as that required by a power-driven vessel making way in restricted visibility (Rule 35 (a)); one prolonged blast.
Rule 9 (g)
Any vessel shall, if the circumstances of the case admit, avoid anchoring in a narrow channel.
Any vessel means that this applies to everyone.
If the circumstances of the case admit means that, if necessary for the safety of a vessel, you can anchor in a narrow channel. But if you have a choice, try not to.
Rule 9 is a long one, so let’s do a quick recap:
If you’re following a narrow channel or fairway, stick to the starboard side as best you can
A vessel less than 20m in length or a sailing vessel needs to avoid impeding the safe passage of a vessel which can only safely navigate in a narrow channel or fairway
A vessel engaged in fishing needs to avoid impeding the passage of any vessel navigating in a narrow channel or fairway, regardless of whether that vessel could safely leave the narrow passage or fairway
A crossing vessel shouldn’t cross a narrow channel or fairway if that would impede the passage of a vessel which can safely navigate only within such a channel or fairway.
5+ short and rapid blasts if you doubt the intentions of a crossing vessel
If you want to overtake and need the vessel in front to take some action to let you do so safely, sound _ _ . if you want to overtake to starboard or _ _ . . if you want to overtake to port. If they are in agreement they will sound Morse C _ . _ . and take action to permit you to pass safely.
If you’re overtaking as per the last bullet point, you still have your obligations as per Rule 13 as an overtaking vessel.
Nobody should go to anchor in a narrow channel if they can avoid doing so.
MCAQs
What conditions of visibility does Rule 9 apply in?
Does Rule 9 apply on inland waterways?
Can a river be a narrow channel?
Can a narrow channel be out of sight of land?
Describe a fairway.
Who should a vessel less than 20m in length or a sailing vessel not impede?
Who should a fishing vessel not impede?
Explain the difference between the vessels that <20m vessels and sailing vessels shouldn’t impede and those that fishing vessels shouldn’t impede.
You are about to cross a narrow channel. By doing so you will impede the passage of a small power-driven vessel that is navigating in the channel, but which could navigate outside of it. May you cross?
You are navigating in a narrow channel and the vessel behind you sounds _ _ . If you are happy for them to pass, what signal should you make and what action would you take?
Does the above make you the give-way vessel?
You are overtaking a tanker in a fairway in poor visibility. You can see her stern in front of you and you intend to overtake on her port side. What sound signal would you make? What sound signal would you expect her to make if she were in agreement? What sound signal would she make if she were in doubt as to whether that was a good idea?
You are approaching an obscured bend in a narrow channel and hear a single prolonged blast. What should you do, and under what rule?
In what circumstances would you anchor in a narrow channel?