IALA buoyage system A special marks
Special marks indicate a special area or feature such as traffic
separation marks, spoil, ground marks, cable or pipe lines marks
including outfall pipes.
They can also define a channel within a channel, for example a
channel for deep draught ships in a wide estuary where the limits
of the channel for normal navigation are marked by red and green
lateral buoys.
Special mark features:
- colour — yellow
- topmark — when a topmark is carried, it
takes the form of a single yellow X
- light — it is yellow and the rhythm may
be any other than those used for the white lights of cardinal,
isolated danger and safe water marks.
Blue middle channel mark
Fixed blue lights are identified as lead lights.
They are commonly used to mark the centre of the channel on
overhead bridges.
Last updated: 17 January 2012
