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 visibility 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.
1 History 2 Colour of light emitted 3 Forward illumination
3.1.1 Dipped beam (low beam, passing beam, meeting beam) 3.1.2 Main beam (high beam, driving beam, full beam)
3.2 Auxiliary lamps
3.2.1 Driving lamps 3.2.2 Front fog lamps 3.2.3 Cornering lamps 3.2.4 Spot lights
4 Conspicuity, signal and identification lights
4.1.1 Front position lamps 4.1.2 Daytime running lamps
18.104.22.168 Installation 22.214.171.124 Intensity and colour
4.1.3 Dim-dip lamps
4.2.1 Side marker lights and reflectors 4.2.2 Turn signals
126.96.36.199 Side turn signals 188.8.131.52 Electrical connection and switching 184.108.40.206 Sequential turn signals 220.127.116.11 Turn signal colour 18.104.22.168 Colour durability
4.3.1 Rear position lamps (tail lamps) 4.3.2 Stop lamps (brake lights)
22.214.171.124 Centre high mount stop lamp (CHMSL) 126.96.36.199 Emergency stop signal (ESS)
4.3.3 Rear fog lamps 4.3.4 Reversing (backup) lamps 4.3.5 Rear registration plate lamp
4.4 On large vehicles
4.4.1 Identification lamps 4.4.2 End-outline marker lamps 4.4.3 Intermediate side marker lamps and reflectors 4.4.4 Rear overtake lights
4.5 Emergency warning devices
4.5.1 Hazard flashers
4.6 Retroreflectors 4.7 Variable-intensity signal lamps 4.8 Experimental systems
4.8.1 Multicolour auxiliary signals
4.9 Research and development
5 Interior and convenience lights 6 On service vehicles
7.1 Incandescent lamps 7.2 Light-emitting diodes (LED) 7.3 High intensity discharge (HID) 7.4 Neon tubes
8 Distributive lighting 9 See also 10 References 11 External links
Early road vehicles used fuelled lamps, before the availability of
electric lighting. The
Ford Model T
ISO symbol for low beam
Dipped-beam (also called low, passing, or meeting beam) headlamps
provide a light distribution to give adequate forward and lateral
illumination without dazzling other road users with excessive glare.
This beam is specified for use whenever other vehicles are present
ISO symbol for high beam
Main-beam (also called high, driving, or full beam) headlamps provide an intense, centre-weighted distribution of light with no particular control of glare. Therefore, they are only suitable for use when alone on the road, as the glare they produce will dazzle other drivers. ECE and Japanese Regulations permit higher-intensity, high-beam headlamps than allowed under US regulations.
Auxiliary lamps Driving lamps
ISO symbol for long-range lamps
Auxiliary high beam lamps may be fitted to provide high intensity light to enable the driver to see at longer range than the vehicle's high beam headlamps may be fitted. Such lamps are most notably fitted on rallying 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 where the period of daylight is short during winter. "Driving lamp" is a term deriving from the early days of nighttime driving, when it was relatively rare to encounter an opposing vehicle. Only on those occasions when opposing drivers passed each other would the low (dipped or "passing") 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 (mandatory) and auxiliary (optional) upper/driving beam lamps. The "driving lamp" term has been supplanted in US regulations by the functionally descriptive term "auxiliary high-beam lamp". Many countries regulate the installation and use of driving lamps. For example, in Russia each vehicle may have no more than three pairs of lights including the original-equipment items, and in Paraguay auxiliary driving lamps must be off and covered with opaque material when the vehicle is circulating in urban areas. Front fog lamps
ISO symbol for front fog lamps
Front fog lamps 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 rain, fog, dust or snow. They are sometimes used in place of dipped-beam headlamps, reducing the glare-back from fog or falling snow, although the legality varies by jurisdiction of using front fog lamps without low beam headlamps.
In most countries, weather conditions rarely necessitate the use of fog lamps, 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. An SAE study has shown that in the United States more people inappropriately use their fog lamps in dry weather than use them properly in poor weather. Because of this, use of the fog lamps when visibility is not seriously reduced is often prohibited in most jurisdictions; for example, in New South Wales, 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 lamps and driving lamps are often confused, due in part to the misconception that fog lamps are necessarily selective yellow, while any auxiliary lamp that makes white light is a driving lamp. Automakers and aftermarket parts and accessories suppliers frequently refer interchangeably to "fog lamps" and "driving lamps" (or "fog/driving lamps"). Cornering lamps
A cornering lamp on a 1983 Oldsmobile 98
On some models, cornering lamps provide white steady-intensity 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 lamp 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. In other modern vehicles, viz., the 2016 and later (ND) Mazda MX-5 "Miata" sports car, in its highest trim level ("Grand Touring"), the regular headlamps act as a cornering lamp by turning to track movements of the steering wheel and thus illuminate the direction of a winding road or a turn; there is no separate cornering lamp. Mazda describes this system as "adaptive lighting". American technical standards contain provisions for front cornering lamps as well as for rear cornering lamps. Cornering lamps 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 (about 25 mph). Spot lights Police cars, emergency vehicles, and those competing in road rallies are sometimes equipped with an auxiliary lamp, sometimes called an alley light, in a swivel-mounted housing attached to one or both a-pillars, directable by a handle protruding through the pillar into the vehicle. Until the mid-1940s, these spot lamps could be found as standard equipment on expensive cars.[which?] Until the mid-1960s, they were commonly offered by automakers as model-specific accessory items. Spot lamps are used to illuminate signs, house numbers, and people. Spot lights can also be had in versions designed to mount through the vehicle's roof. In some countries, for example in Russia, spot lights are allowed only on emergency vehicles or for off-road driving. Conspicuity, signal and identification lights Conspicuity devices are the lamps and reflectors that make a vehicle conspicuous and visible with respect to its presence, position, direction of travel, change in direction or deceleration. Such lamps may burn 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 (such as two left and two right stop lamps) and/or redundant light sources (such as one left and one right stop lamp, each containing two bulbs). Front Front position lamps
ISO symbol for position lamps
"Front position lamps", known as "parking lamps" or "parking lights" in the US, Canada and Australia and "front sidelights" in the UK provide nighttime standing-vehicle conspicuity. They were designed to use little electricity, so they could be left on for periods of time while parked. Despite the UK term, these are not the same as the side marker lights described below. The front position lamps on any vehicle may emit white or amber light in the US, Canada, Mexico, Iceland, Japan, New Zealand and much of the Middle East; elsewhere in the world only motorcycles may have amber front position lamps; all other vehicles must have white ones. Colloquial city light terminology for front position lamps derives from the practice, formerly adhered to in cities like Moscow, London and Paris, of driving at night in built-up areas using these low-intensity lights rather than headlamps. In Germany, the StVZO (Road Traffic Licensing Regulations) calls for a different function also known as parking lamps: With the vehicle's ignition switched off, the operator may activate a low-intensity light at the front (white) and rear (red) on either the left or the right side of the car. 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 and without power consumption in the United States by the mandatory side marker retroreflectors. Daytime running lamps Main article: Daytime running lamp
ISO symbol for daytime running lamps
Some countries permit or require vehicles to be equipped with daytime
running lamps (DRL). Depending on the regulations of the country for
which the vehicle is built, these may be functionally dedicated lamps,
or the function may be provided by the low beam or high beam
headlamps, the front turn signals, or the front fog lamps.
Passenger cars and small delivery vans first type approved to UN
Regulation 48 on or after 7 February 2011 must be equipped with DRLs;
large vehicles (trucks and buses) type approved since August 2012 must
be so equipped. Functional piggybacking, such as
operating the headlamps or front turn signals or fog lamps as DRLs, is
not permitted; the EU Directive requires functionally specific
daytime running lamps compliant with UN Regulation 87 and mounted to
the vehicle in accord with UN Regulation 48.
Prior to the DRL mandate, countries requiring daytime lights permitted
low beam headlamps to provide that function. National regulations in
Canada, Sweden, Norway, Slovenia, Finland, Iceland, and Denmark
require hardwired automatic DRL systems of varying specification. DRLs
are permitted in many countries where they are required, but
prohibited in other countries not requiring them.
Front, side, and rear position lamps are permitted, required or
forbidden to illuminate in combination with daytime running lamps,
depending on the jurisdiction and the DRL implementation. Likewise,
according to jurisdictional regulations, DRLs mounted within a certain
distance of turn signals are permitted or required to extinguish or
dim down to parking lamp intensity individually when the adjacent turn
signal is operating.
Intensity and colour
UN Regulation 87 stipulates that DRLs must emit white light with an
intensity of at least 400 candela on axis and no more than 1200
candela in any direction.
In the US, daytime running lamps may emit amber or white light, and
may produce up to 7,000 candela. This has provoked a large number of
complaints about glare.
UK regulations briefly required vehicles first used on or after 1
April 1987 to be equipped with a dim-dip device or special running
lamps, except such vehicles as comply fully with UN Regulation 48
regarding installation of lighting equipment. A dim-dip device
operates the low beam headlamps (called "dipped beam" in the UK) at
between 10% and 20% of normal low-beam intensity. The running lamps
permitted as an alternative to dim-dip were required to emit at least
200 candela straight ahead, and no more than 800 candela in any
direction. In practice, most vehicles were equipped with the dim-dip
option rather than the running lamps.
The dim-dip systems were not intended for daytime use as DRLs. Rather,
they operated if the engine was running and the driver switched on the
parking lamps (called "sidelights" in the UK). Dim-dip was intended to
provide a nighttime "town beam" with intensity between that of the
parking lamps commonly used at the time by British drivers in city
traffic after dark, and dipped (low) beams; the former were considered
insufficiently intense to provide improved conspicuity in conditions
requiring it, while the latter were considered too glaring for safe
use in built-up areas. The UK was the only country to require such
dim-dip systems, though vehicles so equipped were sold in other
Commonwealth countries with left-hand traffic.
In 1988, the
In the US, amber front and red rear side marker lamps and retroreflectors are required. The law initially required lights or retroreflectors on vehicles made after 1 January 1968. This was amended to require lights and retroreflectors on vehicles made after 1 January 1970. These side-facing devices make the vehicle's presence, position and direction of travel clearly visible from oblique angles. The lights are wired so as to illuminate whenever the vehicles' parking and taillamps are on, including when the headlamps are being used. Front amber side markers in the United States may be wired so as to flash in synchronous phase or opposite-phase with the turn signals, but are not required to flash at all. Side markers are permitted but not required on cars and light passenger vehicles outside the US and Canada. If installed, they are required to be brighter and visible through a larger horizontal angle than US side markers, may flash only in synchronous phase with the turn signals (but are not required to flash), and they must be amber at the front and rear, except rear side markers may be red if they are grouped, combined, or reciprocally incorporated with another rear lighting function that is required to be red. Japan's accession to international standards has caused automakers to change the rear side marker colour from red to amber on their models so equipped in the Japanese market. Turn signals
ISO symbol for turn signals
Wilcot Robot Indicators fitted to 1933 Morris Ten.
Turn signals—formally called "direction indicators" or "directional signals", and informally known as "directionals", "blinkers", "indicators" or "flashers"—are blinking lamps mounted near the left and right front and rear corners of a vehicle, and sometimes on the sides or on the side mirrors of a vehicle, activated by the driver on one side of the vehicle at a time to advertise intent to turn or change lanes towards that side.
Front and side turn signals illuminated.
Electric turn-signal lights date from as early as 1907. The modern flashing turn signal was patented in 1938 and later most major automobile manufacturers offered this feature. As of 2013[update] most countries require turn signals on all new vehicles that are driven on public roadways. Alternative systems of hand signals were used earlier, and remain common for bicycles. Hand signals are also sometimes used when regular vehicle lights are malfunctioning or for older vehicles that are not so equipped.
The Japanese Trafficator deploys to extend from the vehicle's side to indicate a turn in that direction.
Some cars from the 1920s to early 1960s used retractable semaphores called trafficators rather than flashing lights. They were commonly mounted high up behind the front doors and swung out horizontally. However, they were fragile and could be easily broken off and also had a tendency to stick in the closed position. These can be fitted with flashing lights as an upgrade. As with all vehicle lighting and signalling devices, turn-signal lights must comply with technical standards that stipulate minimum and maximum permissible intensity levels, minimum horizontal and vertical angles of visibility, and minimum illuminated surface area to ensure that they are visible at all relevant angles, do not dazzle those who view them, and are suitably conspicuous in conditions ranging from full darkness to full direct sunlight. Side turn signals
Mirror-mounted turn signal
In most countries, cars must be equipped with side-mounted turn signal
repeaters to make the turn indication visible laterally (i.e. to the
sides of the vehicle) rather than just to the front and rear of the
vehicle. These are permitted, but not required in the United States.
As an alternative in both the United States and Canada, the front
amber side marker lights may be wired to flash with the turn signals,
but this is not mandatory.
These two types of dashboard turn signal tell-tale indicators show drivers the signal they're sending to others
Turn signals are required to blink on and off, or "flash", at a steady
rate of between 60 and 120 blinks per minute (1–2 Hz).
Sequential turn signals with OLEDs
Sequential turn signals are a feature on some cars wherein the
turn-signal function is provided by multiple lit elements that
illuminate sequentially rather than simultaneously: the innermost lamp
lights and remains illuminated, the next outermost lamp lights and
remains illuminated, followed by the next outermost lamp and so on
until the outermost lamp lights briefly, at which point all lamps
extinguish together and, after a short pause, the cycle begins again.
The visual effect is one of outward motion in the direction of the
intended turn or lane change. Sequential turn signals have been
factory-installed only on cars with red combination stop/turn
lamps. They were factory fitted to 1965– through
1971-model Ford Thunderbirds, to 1967–1973 Mercury Cougars, to
Shelby Mustangs between 1967 and 1970, to 1969 Imperials, to the
Japanese-market 1971–1972 Nissan Cedric, and to Ford Mustangs since
Two different systems were employed. The earlier, fitted to the 1965
through 1968 Ford-built cars and the 1971–1972 Nissan Cedric,
employed an electric motor driving, through reduction gearing, a set
of three slow-turning cams. These cams would actuate switches to turn
on the lights in sequence. Later Ford cars and the 1969 Imperial used
a transistorised control module with no moving parts to wear, break,
or go out of adjustment.
FMVSS 108 has been officially interpreted as requiring all
light-sources in an active turn signal to illuminate
simultaneously. However, the 2010 and newer Ford Mustangs are
equipped with sequential turn signals.
Turn signal colour
Until the early 1960s, most front turn signals worldwide emitted white
light and most rear turn signals emitted red. The auto industry in the
USA voluntarily adopted amber front-turn signals for most vehicles
beginning in the 1963 model year, though the advent of amber
signals was accompanied by legal stumbles in some states and front
turn signals were still legally permitted to emit white light until
FMVSS 108 took effect for the 1968 model year, whereupon amber became
the only permissible front turn signal colour. Presently, most
countries outside of the United States and
The colour coating has started to flake off this PY27/7W bulb, a relatively new problem.
The amber bulbs commonly used in turn signals with colourless lenses are no longer made with cadmium glass, since various regulations worldwide, including the European RoHS directive, banned cadmium because of its toxicity. Amber glass made without cadmium is relatively costly, so most amber bulbs are now made with clear glass dipped in an amber coating. Some of these coatings are not as durable as the bulb envelopes; with prolonged heat-cool cycles, the coating may flake off the bulb glass, or its colour may fade. This causes the turn signal to emit white light, rather than the required amber light. The international regulation on motor vehicle bulbs requires manufacturers to test bulbs for colour endurance. However, no test protocol or colour durability requirement is specified. Discussion is ongoing within the Groupe des Rapporteurs d'Éclairage, the UNECE working group on vehicular lighting regulation, to develop and implement a colour durability standard. Rather than using an amber bulb, some signal lamps contain an inner amber plastic enclosure between a colourless bulb and the colourless outer lens. Rear
Double taillights mounted on a road-rail vehicle.
Rear position lamps (tail lamps)
Conspicuity for the rear of a vehicle is provided by rear position
lamps (also called tail lamps or tail lights). These are required to
produce only red light and to be wired such that they are lit whenever
the front position lamps are lit, including when the headlamps are on.
Rear position lamps may be combined with the vehicle's stop lamps or
separate from them. In combined-function installations, the lamps
produce brighter red light for the stop lamp function and dimmer red
light for the rear position lamp function. Regulations worldwide
stipulate minimum intensity ratios between the bright (stop) and dim
(rear position) modes, so that a vehicle displaying rear position
lamps will not be mistakenly interpreted as showing stop lamps, and
Stop lamps (brake lights)
Red steady-burning rear lights, brighter than the rear position lamps,
are activated when the driver applies the vehicle's brakes. These are
formally called stop lamps in technical standards and regulations
 and in the Vienna Convention on Road Traffic,
though informally they are sometimes called "brake lights". They are
required to be fitted in multiples of two, symmetrically at the left
and right edges of the rear of every vehicle. International UN
regulations specify a range of acceptable intensity for a stop lamp of
60 to 185 candela. In North America where the UN regulations are
not recognised, the acceptable range for a single-compartment stop
lamp is 80 to 300 candela.
Centre high mount stop lamp (CHMSL)
In the United States and
The rear end of a Renault Master. The offset third brake light above the door handle is visible.
On passenger cars, the
ISO symbol for rear fog lamps
In Europe and other countries adhering to UN Regulation 48, vehicles
must be equipped with one or two bright red "rear fog lamps", which
serve as high-intensity rear position lamps to be turned on by the
driver in conditions of poor visibility to make the vehicle more
visible from the rear. The allowable range of intensity for a rear fog
lamp is 150 to 300 candela, which is within the range of a U.S.
stop lamp (brake light). Rear fog lamps are not required equipment
in the U.S., but they are permitted, and are found almost exclusively
on European-brand vehicles in North America. Audi, Jaguar, Mercedes,
MINI, Land Rover, Porsche, Saab and
Single rear fog lamp on a Mercedes M Class
Most jurisdictions permit rear fog lamps to be installed either singly or in pairs. If a single rear fog is fitted, most jurisdictions require it to be located at or to the driver's side of the vehicle's centreline—whichever side is the prevailing driver's side in the country in which the vehicle is registered. This is to maximize the sight line of following drivers to the rear fog lamp. In many cases, a single reversing lamp is mounted on the passenger side of the vehicle, positionally symmetrical with the rear fog. If two rear fog lamps are fitted, they must be symmetrical with respect to the vehicle's centreline. Proponents of twin rear fog lamps say two lamps provide vehicle distance information not available from a single lamp. Proponents of the single rear fog lamp say dual rear fog lamps closely mimic the appearance of illuminated stop lamps (which are mandatorily installed in pairs), reducing the conspicuity of the stop lamps' message when the rear fogs are activated. To provide some safeguard against rear fog lamps being confused with stop lamps, UN Regulation 48 requires a separation of at least 10 cm between the closest illuminated edges of any stop lamp and any rear fog lamp. Reversing (backup) lamps
Reversing lamps lit on a
To warn adjacent vehicle operators and pedestrians of a vehicle's rearward motion, and to provide illumination to the rear when backing up, each vehicle must be equipped with one or two rear-mounted, rear-facing reversing (or "backup") lamps. These are required to produce white light by U.S. and international UN Regulations. However, some countries have at various times permitted amber reversing lights. In Australia and New Zealand, for example, vehicle manufacturers were faced with the task of localising American cars originally equipped with combination red brake/turn signal lamps and white reversing lights. Those countries' regulations permitted the amber rear turn signals to burn steadily as reversing lights, so automakers and importers were able to combine the (mandatorily amber) rear turn signal and (optionally amber) reversing light function, and so comply with the regulations without the need for additional lighting devices. Both countries presently require white reversing lights, so the combination amber turn/reverse light is no longer permitted on new vehicles. The U.S. state of Washington presently permits reversing lamps to emit white or amber light. Rear registration plate lamp The rear registration plate is illuminated by a white lamp designed to light the surface of the plate without creating white light directly visible to the rear of the vehicle; it must be illuminated whenever the position lamps are lit. On large vehicles Large vehicles such as trucks and buses are in many cases required to carry additional lighting devices beyond those required on passenger vehicles. The specific requirements vary according to the regulations in force where the vehicle is registered. Identification lamps In the US, vehicles over 2,032 mm (80 inches) wide must be equipped with three amber front and three red rear identification lamps spaced between 6 and 12 inches apart at the centre of the front and rear of the vehicle, as high as practicable. The front identification lamps are typically mounted atop the cab of vehicles. The purpose of these lamps is to alert other drivers to the presence of a wide (and usually, tall) vehicle. This type of identification lamp can also be found on road trains in Australia. End-outline marker lamps
End outline marker lamp
UN Regulation 48 requires large[vague] vehicles to be equipped with
left and right white front and red rear end-outline marker lamps,
which serve a purpose comparable to that of the American clearance
lamp, i.e. to indicate clearly the vehicle's overall width and height.
Intermediate side marker lamps and reflectors
US regulations require large
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Until about the 1970s in France, Spain, Morocco, and possibly other countries, many commercial vehicles and some Soviet road trains from "Sovtransavto" had a green light mounted on the rear offside. This could be operated by the driver to indicate that it was safe for the following vehicle to overtake. Emergency warning devices Hazard flashers
ISO symbol for hazard lamps
Also called "hazards", "hazard warning flashers", "hazard warning lights", "emergency lights", "4-way flashers", or simply "flashers". International regulations require vehicles to be equipped with a control which, when activated, flashes the left and right directional signals, front and rear, all at the same time and in phase. Operation of the hazard flashers must be from a control independent of the turn signal control, and an audiovisual tell-tale must be provided to the driver. This function is meant to indicate a hazard such as a vehicle stopped in or near moving traffic, a disabled vehicle, a vehicle moving substantially slower than the flow of traffic such as a truck climbing a steep grade, or the presence of stopped or slow traffic ahead on a high speed road. In vehicles with a separate left and right green turn signal tell-tale on the dashboard, both left and right indicators may flash to provide visual indication of the hazard flashers' operation. In vehicles with a single green turn signal tell-tale on the dashboard, a separate red tell-tale must be provided for hazard flasher indication. Because the hazard flasher function operates the vehicle's left and right turn signals, a left or a right turn signal function may not be provided while the hazard flashers are operating, although the vehicle may activate the indicator and return to the hazard flashing phase once the indicator is deactivated. Retroreflectors
Red rear side marker retroreflectors on
"Retroreflectors" (also "reflex reflectors") produce no light of their
own, but rather reflect incident light back towards its source, for
example, another driver's headlight. They are regulated as automotive
lighting devices, and specified to account for the separation between
a vehicle's headlamps and its driver's eyes. Thus, vehicles are
conspicuous even when their lights are off. Regulations worldwide
require each vehicle to be equipped with rear-facing red
retroreflectors. Since 1968 US regulations also require
side-facing retroreflectors, amber in front and red in the rear.
Sweden, South Africa and other countries have at various times
required white front-facing retroreflectors.
Variable-intensity signal lamps
International UN Regulations[which?] explicitly permit vehicle signal
lamps with intensity automatically increased during bright daylight
hours when sunlight reduces the effectiveness of the stop lamps, and
automatically decreased during hours of darkness when glare could be a
concern. Both US and UN regulations contain provisions for determining
the minimum and maximum acceptable intensity for lamps that contain
more than a single light source.
Multicolour auxiliary signals
Some jurisdictions, such as the US states of Washington,
Emergency vehicles such as fire engines, ambulances, police cars, snow-removal vehicles and tow trucks are usually equipped with intense warning lights of particular colours. These may be motorised rotating beacons, xenon strobes, or arrays of LEDs. The prescribed colours differ by jurisdiction; in most countries, blue and red special warning lamps are used on police, fire, and medical-emergency vehicles. In the United States and some other jurisdictions, amber lights are for tow trucks, private security personnel, construction vehicles, and other nonofficial special-service vehicles, while volunteer firefighters use red, blue, or green, depending on jurisdiction. In the U.S. it is a violation of the D.O.T. (Department of Transportation) Uniform Vehicle Code for any non-emergency vehicle (Police/Fire/Ambulance) to operate forward-facing red lights of any kind. Cars in the U.S. only have red tail-lights, and no blue lights; a vehicle displaying a red (forward-facing) light (flashing or not) coming towards a driver, or from behind the driver (in rear view mirror) indicates that an official emergency vehicle is coming, requiring the driver to yield, pull off to the side of the road, or otherwise get out of its way. Some U.S. States allow emergency vehicles to have blue lights that can be turned on to warn drivers of an emergency vehicle in action; blue and red lights can be combined, forward- and/or rear-facing, also. In the UK, doctors may use green warning lamps although these do not allow the user to claim any exemption from road traffic regulations compared to the blue lights used by statutory emergency services when responding to calls. Special warning lights, usually amber, are also sometimes mounted on slow and/or wide vehicles such as mobile cranes, excavators, tractors, and even mobility scooters in certain conditions. Taxi displays
An illuminated taxi sign
Taxicabs are distinguished by special lights according to local
regulations. They may have an illuminated "Taxi" sign, a light to
signal that they are ready to take passengers or off duty, or an
emergency panic light the driver can activate in the event of a
robbery to alert a passersby to call the police.
The incandescent light bulb was long the light source used in all
automotive lighting devices. Many types of bulbs have been used.
Standardized type numbers are used by manufacturers to identify bulbs
with the same specifications. Bases may be bayonet-type with one or
two contacts, plastic or glass wedge, or dual wire loops or ferrules
used on tubular "festoon" lamps. Screw-base lamps are never used in
automobile applications due to their loosening under vibration. Signal
lamps with internal or external coloured lenses use colourless bulbs;
conversely, lamps with colourless lenses may use red or amber bulbs to
provide light of the required colours for the various functions.
Typically, bulbs of 21 to 27 watts, producing 280 to 570 lumens
(22 to 45 mean spherical candlepower) are used for stop, turn,
reversing and rear fog lamps, while bulbs of 4 to 10 W, producing
40 to 130 lm (3 to 10 mscp) are used for tail lamps, parking
lamps, side marker lamps and side turn signal repeaters.[citation
Tungsten-halogen lamps are a very common light source for headlamps
and other forward illumination functions. Some recent-model vehicles
use small halogen bulbs for exterior signalling and marking functions,
as well. The first halogen lamp approved for
automotive use was the H1, which was introduced in Europe in 1962, 55
W producing 1500 lm.
Light-emitting diodes (LED)
Light-emitting diodes (LEDs) are being used with increasing frequency
in automotive lamps. They offer very long service life, extreme
vibration resistance, and can permit considerably shallower packaging
compared to most bulb-type assemblies. LEDs also offer a potential
safety benefit when employed in stop lights, because when power is
applied they rise to full intensity approximately 250 milliseconds (¼
second) faster than incandescent bulbs. This fast rise time not
only improves the intentional conspicuity of the stop lamp,[citation
needed] but could also provide following drivers with increased time
to react to the appearance of the stop lamps. However, this faster
rise time has not been shown to make cars with
Cars portal Transport portal
Automotive lamp types
^ Gross, Jessica (12 July 2013). "Who Made That Turn Signal?". The New
York Times Magazine. Retrieved 2017-10-25.
^ Paul, John (23 March 2016). "Florence Lawrence: Automotive Inventor
and the "World's First Movie Star"". Historic Vehicle Association.
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Turn signal patent, issued 1909
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