Daytime Running Lights (DRLs) are headlights that are lit whenever a vehicle is running.
DRLs are standard on all General Motors, Lexus, Mercedes-Benz, Saab, Subaru, Suzuki, Volkswagen and Volvo models.
DRLs are an efficient and low-cost method to reduce traffic crashes. They are especially effective in preventing head-on and front-corner collisions by making it easier to see vehicles, also in daylight.
Laws in Canada and many European countries require vehicles to operate with lights on during the daytime.
No U.S. state, however, mandates DRLs.
At least, not yet.