Turn signal

The lighting system of a motor vehicle consists of lighting and signalling devices mounted or integrated to the front, rear, sides, and in some cases the top of a motor vehicle. This lights the roadway for the driver and increases the of the vehicle, allowing other drivers and pedestrians to see a vehicle's presence, position, size, direction of travel, and the driver's intentions regarding direction and speed of travel. Emergency vehicles usually carry distinctive lighting equipment to warn drivers and indicate priority of movement in traffic.

Early road vehicles used fueled lamps, before the availability of electric lighting. For example, the first introduced Ford Model T used carbide lamps for headlamps and oil lamps for tail lamps. It did not have all-electric lighting as a standard feature until after several years on the market. Dynamos for automobile headlamps were first fitted around 1908 and became commonplace in 1920s automobiles. Tail lamps and brake lamps were introduced around 1915, and by 1919 "dip" headlamps were available. The sealed beam headlamp was introduced in 1936 and standardised as the only acceptable type in the USA in 1940. Self-cancelling turn signals were developed in 1940. By 1945 headlamps and signal lamps were integrated into the body styling. Halogen headlamp light sources were developed in Europe in 1960. HID headlamps were produced starting in 1991. In 1993, the first LED tail lamps were installed on mass-production automobiles. LED headlamps were introduced in the first decade of the 21st century.

The colour of light emitted by vehicle lights is largely standardised by longstanding convention. It was first codified in the 1949 Vienna Convention on Road Traffic and later specified in the 1968 United Nations Convention on Road Traffic. Generally, but with some regional exceptions, lamps facing rearward must emit red light, lamps facing sideward and all turn signals must emit amber light, while lamps facing frontward must emit white or selective yellow light. No other colours are permitted except on emergency vehicles.

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Wikipedia