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.
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.
Then confirm the answer with the day shape, vessel length and any extra signal such as towing lights, deck illumination or a cylinder.
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
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