Daytime Running Lights (DRL)
Daytime running lights (DRLs) are forward-facing lamps that make a vehicle easier for other road users to notice in daylight. They usually switch on automatically when the vehicle is ready to drive and change state when the main lighting is activated.
What DRLs do
DRLs are designed for conspicuity, not for illuminating the road ahead. They are brighter than position lamps in their daytime mode, but they do not replace low beam in darkness, tunnels, fog, heavy rain, or other conditions with poor visibility. A lamp can share hardware with a position lamp or direction indicator and use a different intensity for each legal function. UK Department for Transport: daytime running lights
Front and rear lighting are separate
A vehicle showing front DRLs does not necessarily have its rear position lamps illuminated. The exact switching logic depends on the vehicle and market. An illuminated instrument panel also does not prove that the complete exterior lighting system is on.
Automatic lighting can respond to ambient darkness, but it may not recognize every daytime visibility problem. The driver still needs to confirm that the appropriate front and rear lights are active for the conditions.
For the distinction between DRLs, position lamps, low beam, high beam, and adaptive systems, see Headlights, daytime running lights and adaptive beams.