Traffic light

Traffic lights (or traffic signals or stoplights) are lights used to control the movement of traffic. They are placed at road intersections and crossings.^[1] The different colours of lights tell drivers what to do.

In South Africa, they call them robots.^[2][3]

In Japan, the green light is also blue because ao in Japanese means green and blue.^[4]

Traffic lights change their colours 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.^[5] Garrett Morgan, an African-American inventor, also developed a traffic signalling system, and was one of the first people to get a patent for a traffic light.^[6]

William Potts, a Detroit police officer, invented the first traffic light with three colours in 1920 in Detroit, Michigan.^[7]

Wikimedia Commons has media related to:

Traffic signals (category)

• FHWA Arterial Management Website, latest information on traffic signal operations
• Animations of various US signal phasings Archived 17 May 2013 at the Wayback Machine
• SCATS – Sydney Coordinated Adaptive Traffic System
• Safety Evaluation of Converting Traffic Signals from Incandescent to Light-emitting Diodes: Summary Report Federal Highway Administration
• Safety Evaluation of Discontinuing Late-night Flash Operations at Signalized Intersections: Summary Report Federal Highway Administration
• Traffic signals, 1922, digitized NYPD photograph from the Lloyd Sealy Library Digital Collections

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