Light Sources Different lamps are used in a vehicle. Bulbs are mainly used for signal lights, internal lights and tail lights. Halogen lamps are used for headlights. LED lamps are mainly used for signal lights ,tail lights, interior lights,and nowadays also in headlights. Gas discharge lamps are used for headlights. Where are LED lamps used? Interior lights. Tail lights. Headlights. Turn indicator lights QQ QQ