Decide
What does a preferred channel mark show?
The lesson in plain words
- Where they are used
- Where a channel divides in the direction of buoyage, the authority may mark the preferred channel, the main or recommended route, with a modified lateral mark at the point of the split.
- Both branches may be navigable, but the preferred one is usually the deeper channel or the main shipping route.
- How it looks
- A preferred channel mark keeps the main colour, shape and topmark of a lateral mark, with one broad horizontal band of the other colour.
- If fitted, its light matches the main colour and shows Fl(2+1): two flashes, a pause, one flash, then a longer pause before repeating.
- This is called composite group flashing.
- The period, the time for one complete cycle, is no more than 16 seconds.
- Red or green Fl(2+1) is reserved for these marks.
- How to read it
- Going in the direction of buoyage, use its main colour and shape for the preferred channel.
- In Region A, keep a red can with a green band to port: the preferred channel is to starboard.
- Keep a green cone with a red band to starboard: the preferred channel is to port.
- Reverse these passing sides when travelling against the direction of buoyage.
- In Region B
- Going in the direction of buoyage, the colours swap; the logic does not.
- Keep a green can with a red band to port: the preferred channel is to starboard.
- Keep a red cone with a green band to starboard: the preferred channel is to port.
- With this direction, can to port and cone to starboard still lead you into the preferred channel.
- Taking the other channel
- Going in the direction of buoyage, use the opposite side of the mark for the secondary channel.
- Interpret the band colour using the local region.
- In Region A, a red can with a green band then serves as a green starboard-hand mark.
- Check the chart first: the secondary channel may be shallower, narrower or less well marked.
Key data
- Body
- Main lateral colour with one broad band of the other colour
- Light
- Fl(2+1) in the main colour; period no more than 16 s
- Region A, preferred to starboard
- Red can, green band, red Fl(2+1)
- Region A, preferred to port
- Green cone, red band, green Fl(2+1)
- Region B, preferred to starboard
- Green can, red band, green Fl(2+1)
- Region B, preferred to port
- Red cone, green band, red Fl(2+1)
Key points
- A preferred channel mark is a lateral mark with one broad band of the other colour.
- Its light is Fl(2+1) in the main colour, a rhythm kept for these marks.
- In the direction of buoyage, keep a can to port or a cone to starboard for the preferred channel.
- The band colour gives the mark’s meaning for the secondary channel.
Check what you have read
What light rhythm does a preferred channel mark show, if fitted?
True or false?
Decide each statement before you see the answer.
A red or green Fl(2+1) light can be any lateral mark.
The band colour gives the mark’s meaning for the secondary channel.
In the direction of buoyage, keep a can to port or a cone to starboard for the preferred channel.
The band colour shows the side to pass for the main channel.
Its light is Fl(2+1) in the main colour, a rhythm kept for these marks.
Preferred channel marks work the opposite way in Region B.
Practice case & exam keys
Situation
Entering a Region A estuary from seaward, you meet a red can with a broad green band and red Fl(2+1). Your berth is up the secondary branch. A crew member says the band means that branch is closed. How do you decide which side of your boat to leave the mark?
Show the answer
The band identifies a secondary channel; it does not close it. Check the chart and whether that branch’s depths suit your boat. If suitable, take the secondary channel and leave this mark to starboard: its green band gives its secondary-channel meaning. For the preferred channel, leave the red can to port. These sides apply in the direction of buoyage.
Exam keys
- Preferred channel mark: lateral colours with one broad band of the other colour.
- Light Fl(2+1) in the main colour; period no more than 16 s.
- Region A: red can with green band = preferred channel to starboard.
- In the direction of buoyage, keep a can to port or a cone to starboard for the preferred channel.