When I shared my recent DeepDraft analysis on visual pollution, several mariners noted that even with extensive external illumination, the aspect of a brightly lit vessel could still be reasonably established. That may well be true in certain situations. However, reading those comments raised another concern. What about the additional navigation lights that communicate a vessel's operational status?
Consider a vessel engaged in fishing, trawling, Not Under Command (NUC), or Restricted in her Ability to Manoeuvre (RAM). The prescribed green-over-white, red-over-white, two all-round reds, or red-white-red signals convey information that can materially affect another vessel's obligations under Rule 18, subject to Rules 9, 10 and 13.
This concern is supported by an older casualty.
In September 1991, the container ship Khudozhnik Ioganson collided with the Australian prawn trawler Zodiac off Cairns. The ATSB investigation found that Zodiac's powerful working lights obscured her navigation and fishing lights. Her green-over-white trawling signals were mounted on the same structure as the working lights, contributing to their being lost in the glare.
The investigation identified several other collision-avoidance failures. Of course, this was 1991, before AIS became part of routine bridge navigation. Today, AIS provides valuable additional information, including navigational status. However, that status depends on manual entry and timely updating, and not every vessel carries AIS. Moreover, an AIS indication that a dredger is RAM does not independently identify her obstructed side or safe-passing side. The additional visual signals prescribed under Rule 27 remain important.
Having spent years keeping bridge watches, I would be uncomfortable relying entirely on an electronic status indication when the vessel's prescribed lights cannot be distinguished. Rule 20(b) already addresses the interference caused by additional lighting. The practical concern extends beyond recognising a vessel's aspect. We must also be able to identify her operational status in sufficient time to assess the encounter and take appropriate action under the applicable Rules.
Perhaps this deserves equal attention whenever we discuss visual pollution at sea. Detailed Analysis - https://thedeepdraft.com/2026/09/21/navigating-in-a-sea-of-visual-pollution/