Rule 28 allows a vessel constrained by her draught to additionally exhibit three all-round red lights in a vertical line, or a cylinder as a day shape, in addition to the lights prescribed for power-driven vessels in Rule 23.
IMO COLREG 1972Official text
Full wording of the rule, reproduced from the official source below.
A vessel constrained by her draft may, in addition to the lights prescribed for power-driven vessels in Rule 23, exhibit where they can best be seen three all-round red lights in a vertical line, or a cylinder.An interactive 3D illustration is shown here. The same content is described in the rule text and key takeaways below.
Recognition Sequence
Classify the vessel state first: underway, making way, stopped, at anchor, aground, towing, fishing, pilotage or special condition.
Read special lights vertically from top to bottom before using sidelights and sternlight to confirm aspect.
Use the complete display and any vessel length stated in the scenario.
Optional second masthead lights, two anchor lights or deck illumination do not by themselves prove a minimum vessel length.
Exam Focus
Avoid identifying a vessel from one colour alone.
Many mistakes come from spotting a red light and guessing before checking the full pattern.
If the question mentions 'making way', 'underway but stopped', 'at anchor' or 'aground', that wording usually determines which extra lights or shapes appear.
Key Takeaways
Three red all-round lights in a vertical line
Day shape is a cylinder
These are IN ADDITION to normal power-driven vessel lights
This is optional — the vessel MAY display these signals
Common Mistakes
Confusing constrained-by-draught lights with NUC or RAM lights
Not recognizing the cylinder day shape
Test Your Knowledge
Practise this topic and review the explanation for each answer.
More rules in this Part
- Sailing Vessels Underway and Vessels Under OarsSailing vessels show sidelights and sternlight. May optionally show red over green all-round lights at the masthead.
- Fishing VesselsFishing vessels show green over white when trawling, red over white for other fishing, and sidelights plus sternlight when making way.
- Anchored Vessels and Vessels AgroundAnchored vessels show an all-round white light forward and another aft (lower). Vessels aground additionally show two red all-round lights.
- SeaplanesWhere it is impracticable for a seaplane to exhibit lights of the exact characteristics, it shall exhibit lights as closely similar as possible.
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