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9

Narrow Channels

Narrow channel — keep to the outer limit on starboard side.

Rule 9 governs navigation in narrow channels and fairways.

a
Keep as near as safe and practicable to the outer limit on your starboard side.
b
A vessel under 20 metres or a sailing vessel must not impede a vessel that can safely navigate only within the channel or fairway.
c
A vessel engaged in fishing must not impede any other vessel navigating within the channel or fairway.
d
Do not cross if this would impede a vessel that can safely navigate only within the channel. That vessel may use the Rule 34(d) doubt signal if in doubt about the crossing vessel's intention.
e
Where overtaking is possible only if the overtaken vessel acts to permit safe passing, the overtaker signals her intention under Rule 34(c)
  • 1. If agreeing, the overtaken vessel signals under Rule 34(c)
  • 2and takes steps to permit passing; if in doubt she may give the Rule 34(d) signal. The overtaker remains bound by Rule 13.
f
Near a bend or obstruction hiding other vessels, navigate with particular alertness and caution and sound the Rule 34(e) signal.
g
If the circumstances of the case admit, avoid anchoring in a narrow channel.
Left: vessels under 20 m and sailing vessels shall not impede a vessel that can safely navigate only within the channel. Right: fishing shall not impede any other vessel navigating there. Schematic depths are not navigation data.
Bend signal — one prolonged blast where another vessel may be hidden.

IMO COLREG 1972Official text

Full wording of the rule, reproduced from the official source below.

(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. (b) A vessel of less than 20 meters 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. (c) A vessel engaged in fishing shall not impede the passage of any other vessel navigating within a 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 signal prescribed in Rule 34(d) if in doubt as to the intention of the crossing vessel. (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. (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). (g) Any vessel shall, if the circumstances of the case admit, avoid anchoring in a narrow channel.
Source:

STCW Bridge Watch Lens

Apply the vessel-specific duties in Rules 9(b)–(c) and 10(i)–(j).

Following a traffic lane gives no general right of way; the other collision-avoidance duties remain, including Rule 8(f).

Build the traffic picture with sight, hearing, radar/ARPA and chart context.

Do not let AIS or one isolated bearing replace systematic observation.

After manoeuvring, keep monitoring bearing, range, CPA/TCPA and passing distance until the other vessel is finally past and clear.

Exam Focus

Start every scenario by classifying the encounter: overtaking, head-on, crossing, narrow channel, traffic separation, or restricted visibility.

For vessels in sight, every overtaking vessel keeps clear until finally past and clear.

Rule 13 takes precedence over Part B Sections I and II; it does not override the other Parts of COLREG.

Questions on channels and TSS often test the difference between 'keep out of the way' and 'shall not impede'.

Read that wording carefully.

Key Takeaways

1

Keep near the starboard outer limit as safe and practicable

2

Under-20-metre and sailing vessels must not impede a vessel that needs the channel; fishing vessels must not impede any vessel navigating in it

3

Cooperative overtaking uses the prescribed agreement signals and does not remove the overtaker's duty to keep clear

4

Sound the bend warning where required; avoid anchoring if circumstances admit

Common Mistakes

Treating a narrow channel like open water and drifting toward the middle or the wrong side

Crossing in front of a deep-draught or constrained vessel that has little room to manoeuvre

Test Your Knowledge

Practise this topic and review the explanation for each answer.

More rules in this Part

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Frequently asked questions about COLREG Rule 9

Which side of a narrow channel must a vessel keep to?

A vessel proceeding along the course of a narrow channel or fairway shall keep as near to the outer limit of the channel which lies on her starboard side as is safe and practicable (Rule 9(a)).

Under which circumstances may a vessel anchor in a narrow channel?

Rule 9(g) requires any vessel to avoid anchoring in a narrow channel if the circumstances of the case admit. The rule does not define an emergency-only exception; assess whether avoiding anchoring is possible in the actual circumstances.

Which vessels must not impede a vessel navigating in a narrow channel?

A vessel of less than 20 metres in length or a sailing vessel shall not impede a vessel that can safely navigate only within a narrow channel or fairway (Rule 9(b)), and a vessel engaged in fishing shall not impede any other vessel navigating within the channel or fairway (Rule 9(c)).

How do overtaking and crossing work in a narrow channel?

If safe overtaking requires the vessel ahead to take action, the overtaker signals her intention and the vessel ahead, if agreeing, signals agreement and takes steps to permit safe passing (Rule 9(e)); the overtaker remains bound by Rule 13. A vessel shall not cross the channel if crossing would impede a vessel that can safely navigate only within it (Rule 9(d)).