Traffic light

Traffic lights (or traffic signals) are lights used to control the movement of traffic. They are placed at road intersections and crossings. The different colors of lights tell drivers what to do.

This diagram shows how a traditional traffic light works.
Picture 1: A red light means stop.
Picture 2: A green light means go.
Picture 3: A yellow light means slow down and be ready to stop.

Light cycles

Traffic lights change their colors in the same order every time. In most English-speaking countries, traffic lights usually change in this order:

1. Red light on: This tells drivers to stop.
2. Green light on: This means the driver can start driving or keep driving.
3. Yellow light on: This tells drivers to stop when it is safe to, because the light is about to turn red.

Lester Wire was credited with the invention of the electric traffic light in 1912 in Salt Lake City, Utah. Garrett Morgan, an African-American inventor, also developed a traffic signaling system, and was one of the first people to get a patent for a traffic light.

William Potts, a police officer, invented the first traffic light with three colors.