A Navigation light is a coloured source of illumination on an aircraft, spacecraft, or waterborne vessel, used to signal a craft's position, heading, and status. Commonly, their placement is mandated by international conventions or civil authorities.
Navigation lighting systems include:
- Right-of-Way lights - On ships, aircraft and manned spacecraft, a red light will be mounted on the left or port side of the craft and a green on the right or starboard side. These help two craft on a collision course determine who has right-of-way: if a pilot sees a craft on a path crossing his own, he will see either its red running light or green running light. If he sees green, he is to the impinging craft's starboard and has the right of way. If the pilot sees the red light, he knows that the approaching craft has the right-of-way, and he is required to deviate from his course to avoid the collision.
- Strobe lights - On aircraft primarily, strobe lights flash a high-intensity burst of white light, to help other pilots recognize the aircraft's position in low-visibility conditions.
Marine navigation lights
In 1838 the United States
passed an act requiring steamboats running between sunset and sunrise to carry one or more signal lights; colour, visibility and location were not specified.
In 1848 the United Kingdom
passed regulations that required steam vessels to display red and green sidelights as well as a white masthead light. In 1849 the U.S. Congress extended the light requirements to sailing vessels.
In 1889 the United States convened the first International Maritime Conference to consider regulations for preventing collisions. The resulting Washington Conference Rules were adopted by the U.S in 1890 and became effective internationally in 1897. Within these rules was the requirement for steamships to carry a second mast head light.
The international 1948 Safety of Life at Sea Conference recommended a mandatory second masthead light solely for power driven vessels over 150 feet in length and a fixed sternlight for almost all vessels. The regulations have changed little since then.
Marine navigation Part C of the International Regulations for Preventing Collisions at Sea
governs the navigation lights required on a vessel.
To avoid 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 points (22½°) abaft the beam on the starboard
side, a red
light from dead ahead to two points abaft the beam on the port 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 after one must be higher than the forward one.
Lights of special significance
In addition to red, white and green running lights, a combination of red, white and green Mast Lights placed on a mast higher than all the running lights, and viewable from all directions, may be used to indicate the type of craft or the service it is performing. See "Quick Guide" in external links.
- Ships at anchor display one or two white anchor lights (depending on the vessel's length) that can be seen from all directions. If two lights are shown then the forward light is higher than the aft one.
- Boats classed as "small" are not compelled to carry navigation lights and may make use of a handheld torch.
Aviation navigation lights
Aircraft navigation lights are placed in a way similar to that of marine vessels, with a red navigation light located on the left wingtip leading edge and a green light on the right wingtip leading edge. A white navigation light is as far aft as possible on the tail or each wing tip. High-intensity strobe lights are located on the aircraft to aid in collision avoidance.
Navigation lights in civil aviation are required to be operational and to be turned on from sunset to sunrise. High-intensity white strobe lights are part of the anti-collision light system, as well as the aviation red or white rotating beacon. The anti collision light system (either strobe lights or rotating beacon) is required to be operational and to be turned on for all airplanes built after March 11, 1996 on all aircraft operations.