This description is for a system of traffic lights that are powered by solar energy. The system is designed to be energy efficient and cost effective, while providing a reliable source of traffic control. The lights are designed to be easy to install and maintain, and are capable of operating in all weather conditions
From Wikipedia
Solar traffic lights are signalling devices powered by solar panels positioned at road intersections, pedestrian crossings and other locations to control the flows of traffic. They assign the right of way to road users by the use of lights in standard colors, using a universal color code.