Abstract: Power consumption by traffic lights is reduced during the nighttime hours by allowing only part of each cycle of the alternating current to the lights to pass through. A photo conductive cell which is responsive to ambient light intensities controls a timing device which in turn controls the device for allowing current to flow to the lights. Detection devices monitor the proper operation of the devices which allow current to flow through the lights. In the event that an improper operation is detected, an override relay switches full power to the lights.