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.
Front
Front position lamps (parking lamps, standing lamps)
Nighttime standing-vehicle conspicuity to the front is provided by "front position lamps", known as "parking lamps" or "parking lights" in North America, and "front sidelights" in British English. Despite the UK term, these are not the same as the side marker lights described below. The front position lamps may emit white or amber light in North America; elsewhere in the world they must emit only white light. 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. It is now illegal in many countries to drive a vehicle with parking lamps illuminated, unless the headlamps are also illuminated. The UK briefly required Dim-Dip lights, described below, in an attempt to optimise the level of light used at night in built-up areas.
Parking lamps on a Soviet 1974 Volga GAZ-24. In Russia, they are called "podfarniki" ("under-headlights") or "gabarite lights".
Since the late 1960s, front position lamps have been required to remain illuminated even when the headlamps are on, to maintain the visual signature of a dual-track vehicle to oncoming drivers in the event of headlamp burnout. Front position lamps worldwide produce between 4 and 125 candelas.
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 or amber) 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 North America by the mandatory side marker retroreflectors.
Daytime running lamps
A daytime running lamp (DRL, also daylight running lamp or daytime running light) is an automotive lighting device on the front of a roadgoing motor vehicle, installed in pairs, automatically switched on when the vehicle is moving forward, emitting white, yellow, or amber light to increase the conspicuity of the vehicle during daylight conditions.
Installation
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 not 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 & 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 North America, 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.
Dim-dip lamps
U.K. 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 European Commission successfully prosecuted the UK government in the European Court of Justice, arguing that the UK requirement for dim-dip was illegal under EC directives prohibiting member states from enacting vehicle lighting requirements not contained in pan-European EC directives. As a result, the UK requirement for dim-dip was quashed. Nevertheless, dim-dip systems remain permitted, and while such systems are not presently as common as they once were, dim-dip functionality was fitted on many new cars well into the 1990s. The Jaguar XJS used this system, including the final Celebration models produced up until 1995.
