Traffic light

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.

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.

In South Africa, they call them robots.

In Japan, the green light is also blue because ao in Japanese means green and blue.

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.

Traffic Light Media

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  An LED 50-watt traffic light in Portsmouth, United Kingdom

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  Traffic lights can have several additional lights for filter turns or bus lanes.

• Road crossing of A970 with Sumburgh Airport's runway in Shetland. The movable barrier closes when aircraft land or take off.

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  Horizontally-mounted signals in Japan

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  Count down traffic light for pedestrians.

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  "Circular Green" traffic light signal, redrawn from MUTCD Fig. 4D-2. Drawn as an individual signal on a square black background to facilitate modular use (e.g., as a table)

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  "Green Arrow Left" traffic light signal, redrawn from MUTCD Fig. 4D-2. Drawn as an individual signal on a square black background to facilitate modular use (e.g., as a table)

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  "Circular Yellow" traffic light signal, redrawn from MUTCD Fig. 4D-2. Drawn as an individual signal on a square black background to facilitate modular use (e.g., as a table)

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  "Yellow Arrow Left" traffic light signal, redrawn from MUTCD Fig. 4D-2. Drawn as an individual signal on a square black background to facilitate modular use (e.g., as a table)

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  "Circular Red" traffic light signal, redrawn from MUTCD Fig. 4D-2. Drawn as an individual signal on a square black background to facilitate modular use (e.g., as a table)