what is traffic light

A traffic light, also known as a traffic signal or stoplight, is a signaling device positioned at road intersections, pedestrian crossings, and other locations to control the flow of traffic. It consists of three signals—red, yellow (also known as amber), and green—arranged vertically or horizontally in that order. The red light signals drivers to stop, the green light signals them to start or keep driving, and the yellow light signals them to stop when it is safe to do so because the light is about to turn red. Traffic lights were first introduced in December 1868 in London to reduce the need for police officers to control traffic. Since then, electricity and computerized control have advanced traffic light technology and increased intersection capacity