Three mirrors placed at mutual right angles, like one corner of a cube, constitute a "corner reflector," A corner reflector has the useful property of reflecting light directly back to its source, regardless of the direction in which it entered the reflector. The "cat's eyes" are reflectors molded with many small corner reflector shapes on their surface. They can be covered with a transparent red or other filter to reflect red light back to the source. In your car, your eyes and the car headlamps are near enough in the same direction from the cat's eyes, that the headlamp light is reflected back to your eyes no matter in which direction you approach the reflectors in the road.