Automotive lighting
Automotive lighting is functional exterior lighting in vehicles. A motor vehicle has lighting and signaling devices mounted to or integrated into its front, rear, sides, and, in some cases, top. Various devices have the dual function of illuminating the road ahead for the driver, and making the vehicle visible to others, with indications to them of turning, slowing or stopping, etc., with lights also indicating the size of some large vehicles.
Many emergency vehicles have distinctive lighting equipment to warn drivers of their presence.
History
Early road vehicles used fuelled lamps before the availability of electric lighting. The first Ford Model T used carbide lamps for headlights and oil lamps for tail lights. It did not have all-electric lighting as a standard feature until several years after its introduction. Dynamos for automobile headlights were first fitted around 1908 and became commonplace in 1920s automobiles.Trafficators—signalling arms that flipped up, which later were lighted—were introduced in the early 1900s, and were actuated either mechanically or pneumatically. Tail lights and brake lights were introduced around 1915, and by 1919, low-beam or dipped beam headlights were available. Sealed beam headlights were introduced in 1936 and standardized as the only acceptable type in the US in 1940. Self-cancelling turn signals were developed in 1940. By 1945, headlights and signal lights were integrated into the body styling. Halogen headlights were developed in Europe in 1960. High-intensity discharge headlights were produced starting in 1991. In 1993, the first LED tail lights were installed on mass-production automobiles, with LED headlights subsequently being introduced in the 2000s as more powerful LEDs became available.
Colour of light emitted
The colour of light emitted by vehicle lights is largely standardized by established conventions, first codified in the 1949 Geneva Convention on Road Traffic and later specified in the 1968 United Nations Vienna Convention on Road Traffic. With some regional exceptions, lights facing rearward must emit red light, side-facing lights and all turn signals must emit amber light, and lights facing forward must emit white or selective yellow light. No other colours are permitted except on emergency vehicles. Vehicle lighting colour specifications can differ somewhat in countries that have not signed the 1949 and/or 1968 Conventions; examples include turn signals and side marker lights in North America, as described in those lights' sections later in this article.Forward illumination
Forward illumination is provided by high- and low- beam headlights, which may be augmented by auxiliary fog lights, driving lights, or cornering lights.Headlights
Low beam (dipped beam, passing beam, meeting beam)
Low beam headlights provide adequate forward and lateral illumination without dazzling other road users with excessive glare. This beam is specified for use whenever other vehicles are present ahead.UN ECE regulations for dipped beam headlights specify a beam with a sharp, asymmetric cut-off; the half of the beam closest to oncoming drivers is flat and low, while the half of the beam closest to the outside of the road slopes up and towards the near side of the roadway. This permits a functional compromise where it is possible to substantially prevent glare for oncoming drivers, while still allowing adequate illumination for drivers to see pedestrians, road signs, hazards, etc. on their side of the road.
The United States and Canada use proprietary FMVSS / CMVSS standards instead of UN ECE regulations. These standards contain regulations for dipped beam headlights that also specify a beam with a sharp, asymmetric cut-off; the half of the beam closest to oncoming drivers is also flat and low, but not as low as prescribed in UN ECE regulations. The half of the beam closest to the outside of the road is also flat, but higher than the half closest to oncoming vehicles. This results in substantially increased glare for oncoming drivers and also poorer illumination of the near side of the roadway in comparison to headlights conforming to UN ECE regulations.
High beam (main beam, driving beam, full beam)
High beam headlights provide an intense, centre-weighted distribution of light with no particular glare control. Therefore, they are only suitable for use when alone on the road, as the glare they produce will dazzle other drivers.UN ECE Regulations permit higher-intensity high-beam headlights than allowed under U.S. and Canadian FMVSS / CMVSS standards.
Auxiliary lights
Driving lights
Auxiliary high beam lights may be fitted to provide high-intensity light to enable the driver to see at longer range than the vehicle's high beam headlights. Such lights are most notably fitted on rally cars, and are occasionally fitted to production vehicles derived from or imitating such cars. They are common in countries with large stretches of unlit roads, or in regions such as the Nordic countries that receive fewer daylight hours during winter."Driving light" is a term hailing from the early days of night time driving, when it was relatively rare to encounter an opposing vehicle. Only on occasions when opposing drivers passed each other would the low beam be used. The high beam was therefore known as the "driving beam", and this terminology is still found in international UN Regulations, which do not distinguish between a vehicle's primary and auxiliary upper/driving beam lights. The "driving light" term has been supplanted in US regulations by the functionally descriptive term "auxiliary high-beam light".
Many countries regulate the installation and use of driving lights. For example, in Russia, each vehicle may have no more than three pairs of driving lights, and in Paraguay, auxiliary driving lights must be off and covered with opaque material when the vehicle is operated in urban areas.
Front fog lights
Front fog lights provide a wide, bar-shaped beam of light with a sharp cutoff at the top, and are generally aimed and mounted low. They may produce white or selective yellow light, and were designed for use at low speed to increase the illumination directed towards the road surface and verges in conditions of poor visibility due to fog, dust or snow.They are sometimes used in place of dipped-beam headlights, reducing glare from fog or falling snow, although the legality of using front fog lights without low-beam headlights varies by jurisdiction.
In most countries, weather conditions rarely necessitate the use of front fog lights and there is no legal requirement for them, so their primary purpose is frequently cosmetic. They are often available as optional extras or only on higher trim levels of many cars. Since as early as the 2020s, several car manufacturers have noticeably omitted the front fog lights from many of their latest models, as more recent high-tech lighting technologies such as daytime running lamps and LEDs connected to automatic high-beam systems negate the use of fog lights. However, some manufacturers who still offer fog lights as standard equipment in certain model trims have diversified its use to function also as an automatic lighting delay for vehicles, to light up surroundings and roadside curbs after being parked.
An SAE study has shown that in the United States, more people inappropriately use their fog lights in dry weather than use them properly in poor weather. Because of this, use of the fog lights when visibility is not seriously reduced is often prohibited in most jurisdictions; for example, in Australia, "The driver of a vehicle must not use any fog light fitted to the vehicle unless the driver is driving in fog, mist or under other atmospheric conditions that restrict visibility."
The respective purposes of front fog lights and driving lights are often confused, due in part to the misconception that fog lights are always selective yellow, while any auxiliary light that makes white light is a driving light. Automakers and aftermarket parts and accessories suppliers frequently refer interchangeably to "fog lights" and "driving lights".
Cornering lights
On some models, cornering lights provide steady-intensity white light for lateral illumination in the direction of an intended turn or lane change. They are generally actuated in conjunction with the turn signals, and they may be wired to also illuminate when the vehicle is shifted into reverse gear. Some modern vehicles activate the cornering light on one or the other side when the steering wheel input reaches a predetermined angle in that direction, regardless of whether a turn signal has been activated.American technical standards contain provisions for front cornering lights as well as rear cornering lights. Cornering lights have traditionally been prohibited under international UN Regulations, though provisions have recently been made to allow them as long as they are only operable when the vehicle is travelling at less than 40 kilometres per hour.
Spotlights
Police cars, emergency vehicles, and vehicles competing in road rallies are sometimes equipped with an auxiliary spotlight, sometimes called an "alley light", in a swivel-mounted housing attached to one or both A-pillars, aimed by a handle protruding through the pillar into the vehicle.Conspicuity, signal and identification lights
devices are lights and reflectors that are intended to make a vehicle more conspicuous and visible with respect to its presence, position, direction of travel, change in direction, or deceleration. Such lights may light steadily, blink, or flash, depending on their intended and regulated function. Most must be fitted in pairs—one left and one right—though some vehicles have multiple pairs and/or redundant light sources.Front
Front position lights
Front position lights provide nighttime standing-vehicle conspicuity. They are designed to use little electricity so they can be left on when parked for prolonged periods of time. Despite the UK term, these are not the same as the side marker lights described below. The front position lights on any vehicle must emit white light, with the exception of motorcycles, which may have amber front position lights. In the US, Canada, Mexico, Iceland, Japan, New Zealand, and Australia, they may emit amber light on any vehicle. The "city light" terminology for front position lights derives from the practice, formerly adhered to in cities like Moscow, London and Paris, of driving at night in urban areas using these low-intensity lights rather than the vehicle's headlights.In Germany, the StVZO calls for a different function provided by these lights: with the vehicle's ignition switched off, the operator may activate a low-intensity white light at the front and red light at the rear on either the left or right side. This function is used when parking in narrow unlit streets to provide parked-vehicle conspicuity to approaching drivers. This function, which is optional under UN and US regulations, is served passively in the United States by mandatory side marker retroreflectors.