Rule 9: narrow channels
- Keep to starboard: keep as near to the outer limit of the channel on your starboard side as is safe and practicable.
- Don't impede ships: a vessel under 20m or a sailing vessel must not impede the passage of a vessel that can safely navigate only within the channel. A vessel engaged in fishing must not impede any other vessel in the channel.
- Crossing: don't cross a channel if that would impede a vessel that can only navigate within it. If she's unsure what you're doing, she may sound five short blasts.
- Overtaking: if you can only overtake with the other vessel's help, signal your intention (two prolonged blasts, then one short to pass on her starboard side or two short for her port side). She signals agreement with prolonged, short, prolonged, short. You're still the overtaking vessel under Rule 13.
- Bends: approaching a bend where other vessels may be hidden, go with particular caution and sound one prolonged blast.
- Anchoring: avoid anchoring in a narrow channel if you possibly can.
Rule 10: traffic separation schemes
A traffic separation scheme (TSS) splits busy waters into one-way lanes, with a separation zone between them. They're marked on charts in magenta, with arrows showing the direction of traffic.
If you're using the scheme
- Go in the correct lane, in the general direction of traffic flow.
- Keep clear of the separation zone and separation lines as far as practicable.
- Join or leave at the ends of a lane. If you must join or leave from the side, do it at as small an angle to the flow as practicable.
If you're crossing it
- Avoid crossing if you can. If you must, cross on a heading as nearly as practicable at right angles to the traffic flow.
- It's your heading that must be at right angles, not your track over the ground. Don't steer into the tide to hold a square track: you'll look as though you're joining the lane, and spend longer in it.
- Under 20m or under sail, you must not impede the safe passage of a power-driven vessel following a lane. Plan to cross through gaps in the traffic, and motor if you need to keep moving.
Inshore traffic zones and the edges
- The inshore traffic zone between a scheme and the coast may be used by vessels under 20m, sailing vessels and vessels engaged in fishing.
- If you're not using the scheme, keep as wide a berth from it as practicable.
- Take particular care near the ends of a scheme, where traffic converges, and don't anchor in or near one.