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. DRLs might have been first seriously proposed in 1961 in the USA, in response to Texas then-Governor Price Daniels' drive-safely campaign.

 Implementations

Depending on prevailing regulations and vehicle equipment, the daytime running light function may be implemented by functionally-specific lamps, by operating the low-beam headlamps or fog lamps at full or reduced intensity, by operating the high-beam headlamps at reduced intensity, or by steady-burning operation of the front turn signals. Compared to any mode of headlamp operation to create the daytime running light, functionally-dedicated DRLs maximize the potential benefits in safety performance and minimize fuel consumption, glare, motorcycle masking, and other potential drawbacks

Effect of ambient light

The Daytime Running Light was first mandated, and safety benefits first perceived, in Scandinavian countries where it is frequently and persistently dark during daytime hours. As ambient light levels increase, the potential safety benefit decreases while the DRL intensity required for a safety improvement increases. The safety benefit produced by DRLs in relatively dark Nordic countries is roughly triple the benefit observed in relatively bright Israel and America.

Environmental impact

DRL power consumption varies widely depending on the implementation. Current production DRL systems consume from 8 watts (dedicated LEDsystem) to over 200 W (headlamps and all parking, tail, and marker lights on). International regulators, primarily in Europe, are working to balance the potential safety benefit offered by DRL with the increased fuel consumption due to their use. Because the power to run the DRLs must be produced by the engine, which in turn requires burning additional fuel, high-power DRL systems increase CO₂ emissions sufficiently to affect a country's compliance with the Kyoto protocol on greenhouse gas emissions. For that reason, low-power solutions are being encouraged,for use when and if DRLs become mandatory in ECE Regulations. LEDs and low-power, high-efficacy, long-life light bulbs produce appropriate amounts of light for an effective DRL without significantly increasing fuel consumption or emissions. Fuel consumption reductions of up to 0.5 mpg may be found when comparing a 55 W DRL system to a 200 W DRL system.In 2006, the UK's Department of Transport also found significant reductions in emissions and fuel consumption when comparing a 42 W DRL system to a 160 W full headlight DRL systems.DRL fuel consumption can be reduced to insignificant levels by the use of 8 to 20 W DRL systems based on LEDs or high-efficacy filament bulbs.