Rule 21 defines the types of navigation lights:
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
Masthead light covers 225 degrees (ahead to 22.5 abaft beam)
Sidelights cover 112.5 degrees each
Sternlight covers 135 degrees
All-round light covers full 360 degrees
Common Mistakes
Confusing the arcs of visibility for different light types
Forgetting towing light is yellow, same arc as sternlight
Test Your Knowledge
Test your knowledge and prove your mastery.
More rules in this Part
- Power-driven Vessels UnderwayPower-driven vessels underway shall exhibit masthead light(s), sidelights, and sternlight. Vessels 50m+ require two masthead lights.
- Towing and PushingVessels towing or pushing display additional masthead lights and a yellow towing light. Three masthead lights if tow exceeds 200m.
- 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.
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