Navigation light

[1] Some navigation lights are colour-coded red and green to aid traffic control by identifying the craft's orientation.

A common misconception is that marine or aircraft navigation lights indicate which of two approaching vessels has the "right of way" as in ground traffic; this is never true.

However, the red and green colours are chosen to indicate which vessel has the duty to "give way" or "stand on" (obligation to hold course and speed).

Consistent with the ground traffic convention, the rightmost of the two vehicles is usually given stand-on status and the leftmost must give way.

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.

c. 100) enabling the Lord High Admiral to publish regulations requiring all sea-going steam vessels to carry lights.

[5] 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.

Their purpose is to alert others when something is happening that ground crew and other aircraft need to be aware of, such as running engines or entering active runways.

In civil aviation, pilots must keep navigation lights on from sunset to sunrise, even after engine shutdown when at the gate.

The anti-collision system is recommended in good visibility, where only strobes and beacon are required can use white (clear) lights to increase conspicuity during the daytime.

These lights are optional to turn on, though most pilots switch them on at night to increase visibility from other aircraft.