Abstract: Rear warning lights on a vehicle are actuated in response to vehicular speed. When energized below a predetermined vehicular speed threshold, the warning lights will begin to flash alternately. The rate of flashing may be fixed so that each warning light flashes on briefly and at a fixed rate or it may be set to flash at a rate related to vehicular speed so that each warning light stays on longer as the vehicle speed decreases. At some very low vehicular speed, corresponding substantially to a full stop, the flashing may be set to cease so that one of the warning lights will glow steadily.