Visibility of lights
In plain language
Minimum ranges depend on vessel length: 50 m and over — masthead 6 miles, sidelights 3, stern/towing/all-round 3; 12 m to 50 m — masthead 5 (3 if under 20 m), sidelights 2, others 2; under 12 m — masthead 2, sidelights 1, others 2.
Full text of Rule 22
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:
In vessels of 50 metres 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.
In vessels of 12 metres or more in length but less than 50 metres in length: a masthead light, 5 miles; except that where the length of the vessel is less than 20 metres, 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.
In vessels of less than 12 metres 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.
In inconspicuous, partly submerged vessels or objects being towed: a white all-round light, 3 miles.
Reproduced from the COLREGs 1972 (as amended) for study. Always verify against the official IMO publication.
Key points
- 1
50 m and over: masthead light visible 6 miles.
- 2
12 m to under 50 m: masthead 5 miles, or 3 miles if under 20 m.
- 3
Under 12 m: masthead 2 miles, sidelights 1 mile.