All new cars sold in Europe are now fitted with daytime running lights. These are bright enough to be seen in daylight and can be incorporated into headlights or separate (almost looking like front fog lights on some models). They switch on automatically whenever you turn the engine on, and turn off when the headlights are turned on. The problem is many drivers mistake them for headlights, but they don't activate the rear lights. So people can be driving around, thinking they've got their headlights on (because the road ahead is lit up), but with no lights at the rear.