الوصف

Applied to the ships as lamp signal liaison when night navigation. 
collisions, vessels mount navigation lights that permit other vessels to determine the type and relative angle of a vessel, and thus decide if there is a danger of collision. In general sailing vessels are required to carry a green light that shines from dead ahead to 2 starboard side (the right side from the perspective of someone on board facing forward), a red light from dead ahead to two points abaft the beam on the port side (left side) and a white light that shines from astern to two points abaft the beam on both sides. Power driven vessels in addition to these lights, must carry either one or two (depending on length) white masthead lights that shine from ahead to two points abaft the beam on both sides. If two masthead lights are carried then the aft one must be higher than the forward one.

Small power driven vessels (under *2 metres (*9 ft)) may carry a single all-round white light in place of the two or three white lights carried by larger vessels, they must also carry red and green navigation lights. Vessels under 7 metres (*3 ft) with a maximum speed of less than 7 knots are not required to carry navigation lights, but must be capable of showing a white light. Hovercraft at all times and some boats operating in crowded areas may also carry a yellow flashing beacon for added visibility during day or night.