Abstract: Electric circuit apparatus is disclosed for automatically controlling the tail light of a motor vehicle so as to assist in preventing accidents. An electronic control circuit operates an electrical power switch connected between the tail light and a source of voltage in such a way that the tail light is automatically turned on when the speed of the vehicle falls below a prescribed threshold, such as 15 mph, for a prescribed period of time, such as 10 seconds, and/or a number of other stated conditions occur.