Visibility of Lights
Specifies minimum visibility ranges for lights based on vessel length.
Rule 22 establishes the minimum ranges of visibility for navigation lights based on vessel length. For vessels 50 metres or more: masthead light 6 miles, sidelight 3 miles, sternlight 3 miles, towing light 3 miles, all-round white/red/green/yellow 3 miles.
For vessels 12 metres to under 50 metres: masthead light 5 miles (3 miles if under 20m), sidelight 2 miles, sternlight 2 miles. For vessels under 12 metres, reduced ranges apply.
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
Larger vessels require greater light visibility ranges
Masthead light of large vessels must be visible at 6 miles
Sidelights must be visible at 3 miles for vessels 50m+
Smaller vessels have proportionally reduced requirements
Common Mistakes
Using under-powered lights that don't meet minimum range requirements
Test Your Knowledge
Test your knowledge and prove your mastery.