Rule 22 establishes the minimum ranges of visibility for navigation lights based on vessel length. The lights prescribed in these Rules shall have an intensity as specified in Section 8 of Annex I so as to be visible at the following minimum ranges:
In vessels of 50 metres or more in length:
- Masthead light — 6 nm
- Sidelight — 3 nm
- Sternlight — 3 nm
- Towing light — 3 nm
- White, red, green or yellow all-round light — 3 nm
In vessels of 12 metres or more but less than 50 metres in length:
- Masthead light — 5 nm (except that where the length of the vessel is less than 20 metres — 3 nm)
- Sidelight — 2 nm
- Sternlight — 2 nm
- Towing light — 2 nm
- White, red, green or yellow all-round light — 2 nm
In vessels of less than 12 metres in length:
- Masthead light — 2 nm
- Sidelight — 1 nm
- Sternlight — 2 nm
- Towing light — 2 nm
- White, red, green or yellow all-round light — 2 nm
In inconspicuous, partly submerged vessels or objects being towed: - White all-round light — 3 nm
| Vessel length | Masthead light | Sidelights | Sternlight | Towing light | All-round light |
|---|---|---|---|---|---|
| ≥ 50 m | 6 | 3 | 3 | 3 | 3 |
| 20 m ≤ L < 50 m | 5 | 2 | 2 | 2 | 2 |
| 12 m ≤ L < 20 m | 3 | 2 | 2 | 2 | 2 |
| < 12 m | 2 | 1 | 2 | 2 | 2 |
IMO COLREG 1972Official text
Full wording of the rule, reproduced from the official source below.
The lights prescribed in these Rules shall have an intensity as specified in Section 8 of Annex I to these Regulations so as to be visible at the following minimum ranges:
(a) In vessels of 50 meters or more in length:
− a masthead light, 6 miles;
− a sidelight, 3 miles;
− a sternlight, 3 miles;
− a towing light, 3 miles;
− a white, red, green or yellow all-round light, 3 miles.
(b) In vessels of 12 meters or more in length but less than 50 meters in length:
− a masthead light, 5 miles; except that where the length of the vessel is less than 20 meters, 3 miles;
− a sidelight, 2 miles;
− a sternlight, 2 miles;
− a towing light, 2 miles;
− a white, red, green or yellow all-round light, 2 miles.
(c) In vessels of less than 12 meters in length:
− a masthead light, 2 miles;
− a sidelight, 1 mile;
− a sternlight, 2 miles;
− a towing light, 2 miles;
− a white, red, green or yellow all-round light, 2 miles.
(d) In inconspicuous, partly submerged vessels or objects being towed:
− a white all-round light, 3 miles.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
≥50m vessels: masthead 6 nm, all other lights 3 nm
12–<50m vessels: masthead 5 nm (3 nm if <20m), sidelights/sternlight/all-round 2 nm
<12m vessels: masthead 2 nm, sidelights 1 nm, sternlight/all-round 2 nm
Inconspicuous towed objects: white all-round 3 nm
Common Mistakes
Using under-powered lights that don't meet minimum range requirements
Forgetting the masthead-light step-down to 3 nm for 12–<20m vessels
Forgetting that on <12m vessels the sidelight range (1 nm) drops below the sternlight range (2 nm)
Test Your Knowledge
Practise this topic and review the explanation for each answer.
More rules in this Part
- Application (Lights)Rules concerning lights shall be complied with from sunset to sunrise and during restricted visibility.
- 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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