COLREGS Rule 9 — Narrow Channels

Rule Text

What it means on the water

• →Keep to the starboard side of the channel — as near to the outer limit as safe and practicable.
• →Vessels under 20m and sailing vessels shall NOT impede channel vessels (i.e., vessels that can only navigate within the channel).
• →Fishing vessels shall not impede ANY vessel navigating within a narrow channel.
• →A vessel crossing the channel shall not impede a vessel confined to the channel.
• →No anchoring in a narrow channel except emergency.
• →Overtaking: signal required; the vessel being overtaken must agree before the pass occurs (Rule 9(e)).

Common exam mistakes

• ✗Thinking sailing vessels have priority in a narrow channel — they do not; they must not impede confined vessels.
• ✗Forgetting that fishing vessels must not impede ANY vessel (not just confined ones).
• ✗Missing that anchoring is prohibited in narrow channels except in emergency.

USCG exam questions — Rule 9

These questions are drawn from the same pool used in real USCG licensing exams. Correct answers and explanations are shown.

1. 1. Under Rule 9, a vessel proceeding along a narrow channel or fairway shall:

   • A.Keep to the center of the channel at all times
   • B.Keep as near to the outer limit of the channel on her starboard side as is safe and practicable✓
   • C.Give way to all vessels overtaking from astern
   • D.Sound one short blast to signal her intention to maintain course

   Why: Rule 9(a) requires vessels in a narrow channel to keep to the starboard side of the channel — not the center. This mirrors the road rule and ensures predictable traffic flow, reducing the risk of head-on encounters in confined waterways.

2. 2. When overtaking is possible only if the vessel to be overtaken takes action to permit safe passing in a narrow channel, Rule 9(e) requires:

   • A.The overtaking vessel to wait until the channel widens before overtaking
   • B.The vessel to be overtaken to automatically give way if the overtaking vessel sounds two prolonged blasts
   • C.The overtaking vessel to indicate intent with the appropriate signal and obtain agreement before proceeding✓
   • D.The overtaking vessel to use VHF channel 16 to obtain permission from port control

   Why: Rule 9(e) establishes a two-step process: the overtaking vessel signals intent (two prolonged plus one short for starboard, or two prolonged plus two short for port), and the overtaken vessel signals agreement with one prolonged, one short, one prolonged, one short. If agreement is not obtained, the overtake shall not proceed.

3. 3. When joining or leaving a traffic lane in a TSS, Rule 10 requires a vessel to do so:

   • A.At the designated inbound or outbound waypoints shown on the chart
   • B.At as small an angle to the general direction of traffic flow as practicable✓
   • C.After broadcasting her intentions on VHF channel 16
   • D.Only at the terminal ends of the scheme

   Why: Rule 10(c) requires vessels to join or leave a traffic lane at as small an angle as practicable. A shallow joining angle minimizes the time the vessel spends cutting across traffic flow and reduces collision risk. There is no requirement to use specific waypoints or to broadcast on VHF.

4. 4. Under Rule 9(f), a vessel approaching a bend or an area of a channel where other vessels may be obscured shall:

   • A.Stop engines and navigate with extreme caution
   • B.Sound five short blasts to alert approaching traffic
   • C.Navigate with particular alertness and caution and sound the appropriate signal prescribed in Rule 34(e)✓
   • D.Reduce to bare steerageway and post a bow lookout

   Why: Rule 9(f) requires particular alertness and caution when approaching a channel bend with obscured visibility, and requires sounding the signal prescribed in Rule 34(e) — one prolonged blast. Rule 34(e) prescribes the signal and Rule 9(f) mandates its use at bends. Five short blasts is the danger/doubt signal, not the bend signal.

5. 5. Under Rule 9, a vessel shall not cross a narrow channel or fairway if such crossing:

   • A.Impedes the passage of a vessel which can safely navigate only within such channel✓
   • B.Requires crossing during hours of darkness
   • C.Takes place without prior notification to the harbor master
   • D.Results in a crossing angle of less than 45 degrees

   Why: Under Rule 9(d), a vessel shall not cross a narrow channel or fairway if the crossing impedes the passage of a vessel which can safely navigate only within such channel (option 0). If that confined ("latter") vessel is in doubt as to the crossing vessel's intentions, it may — at its discretion — sound the doubt signal prescribed in Rule 34(d) (at least five short, rapid blasts).

6. 6. Under Rule 9, a fishing vessel operating in a narrow channel shall:

   • A.Not impede the passage of any vessel which can only safely navigate within the channel✓
   • B.Have priority over all other vessel traffic due to her operational status
   • C.Anchor outside the channel boundaries before setting gear
   • D.Proceed only during slack water to minimize navigational conflicts

   Why: Under COLREGS Rule 9(c) (and identically US Inland Rule 9(c), 33 CFR 83.09(c)), a vessel engaged in fishing shall not impede the passage of any other vessel navigating within a narrow channel or fairway. Fishing vessels receive no special priority in narrow channels, so option A is correct; Rule 9(b), by contrast, applies the not-impede duty to vessels under 20 m and sailing vessels.

7. 7. Under Rule 9(d), a vessel shall not cross a narrow channel or fairway if such crossing impedes the passage of another vessel navigating within that channel. However, the vessel navigating within the channel may sound which signal if the crossing vessel's intentions are unclear?

   • A.One prolonged blast
   • B.Five or more short and rapid blasts✓
   • C.Two prolonged blasts
   • D.One prolonged and two short blasts

   Why: Rule 34(d) states that a vessel may indicate doubt about whether sufficient action is being taken by the other vessel by sounding five or more short and rapid blasts on the whistle. This danger signal applies when there is uncertainty about another vessel's intentions, including in crossing situations near narrow channels.

8. 8. Under Rule 9, anchoring in a narrow channel is addressed by which provision?

   • A.Anchoring is permitted provided the vessel sounds proper fog signals
   • B.A vessel shall not anchor in a narrow channel if it can be avoided✓
   • C.Vessels may anchor in narrow channels only if they display day shapes
   • D.There is no prohibition on anchoring in narrow channels under Rule 9

   Why: Rule 9(g) states that a vessel shall not anchor in a narrow channel if it can be avoided, recognizing that anchoring in a narrow channel creates hazards for other vessels navigating the channel.

Frequently asked questions

Which vessels must not impede traffic in a narrow channel?

Vessels under 20 meters and sailing vessels must not impede a vessel that can only safely navigate within the channel. Fishing vessels must not impede any vessel navigating within a narrow channel. A vessel crossing the channel must also not impede a vessel confined to it.

Can you overtake in a narrow channel?

Yes, but Rule 9 requires a specific signal procedure. The overtaking vessel signals its intent (two prolonged + one short for overtaking to starboard; two prolonged + two short for overtaking to port under Inland Rules). The vessel being overtaken must signal agreement before the pass can proceed safely.

All COLREGS rules