Junctions: which side is the preferred channel on?

At a junction, a modified lateral mark can indicate the preferred channel. “Preferred to starboard” names the branch on that side relative to conventional direction; the mark then occupies the port side of that channel.

The apparent contradiction disappears when the junction is drawn and the branch name is separated from the mark’s lateral role.

Imagine conventional direction pointing up with a junction ahead. The preferred channel branches right of the mark.

Relative to the reference, right is starboard; for the preferred channel the mark lies on its port side. If the preferred branch goes left, the mark has the starboard-side role.

Classification remains tied to the conventional arrow even if a boat faces down in the figure.

The modified mark retains its predominant lateral identity and adds a broad horizontal band of the other colour. Where fitted, its light follows the predominant colour and shows Fl(2+1).

Region, preferred branch, predominant colour, band, shape or topmark and light therefore need to be read together. The band neither changes light colour nor turns a port mark into a starboard mark.

Both notations can involve three flashes in total but organise them differently. Fl(2+1) combines an associated pair with a separated single within the cycle; Fl(3) is a three-flash group.

The figure’s strip shows component separation without fixing seconds between flashes. This category assigns no single period to every junction: consult the actual published characteristic.

Counting events and understanding grouping are different tasks.

The system’s preference does not select your destination: the secondary branch may be the intended one, while the preferred channel may have important limits for the individual boat. Current charts, conditions and local restrictions complete that decision.

To recall identity, draw the branch first, determine which side the mark occupies, then apply the regional combination of colour, band, shape and light. Opposite headings helps keep the reference stable.

In the equivalent B example, red and green change, including the light. Preferred to starboard and the can’s port role remain: region changes the visual combination rather than branch geometry.