Rule 22 - Visibility of lights

Please note: The following information has been reproduced from Part C (Lights and Shapes) of the Prevention of Collision at Sea Regulations 1983 (external link). The purpose of the reproduction is to explain "graphically'' the requirements of navigation lights on a variety of vessels.

(a) In a vessel of 50 metres or more in length:

• a masthead light, 6 miles (11.1 km);
• a sidelight, 3 miles (5.56 km);
• a sternlight, 3 miles ( 5.56 km);
• a towing light, 3 miles (5.56 km); and 
• a white, red, green or yellow all-round - light, 3 miles (5.56 km).

(b) In a vessel of 12 metres or more but less than 50 metres in length:

• a masthead light, 5 miles (9.3 km); except that where the length of the vessel is less than 20 metres, 3 miles;
• a sidelight, 2 miles ( 3.7 km);
• a sternlight, 2 miles (3.7 km);
• a towing light, 2 miles (3.7 km); and 
• a white, red, green, or yellow all-round light, 2 miles (3.7 km).

(c) In vessels of less than 12 metres in length:

• a masthead light, 2 miles (3.7 km);
• a sidelight, 1 mile (1.85 km);
• a sternlight, 2 miles (3.7 km);
• a towing light, 2 miles (3.7 km); and 
• a white, red, green, or yellow all-round light, 2 miles (3.7 km).

(d) In inconspicuous, partly submerged vessels or objects being towed;

• a white all-round light, 3 miles (5.56 km).

Kilometre to mile conversion factor 1 Nautical mile = 1852 metres