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. The different colours 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 colours in the same order every time. In most English-speaking countries, traffic lights usually change in this order:
 Red light on: This tells traffic to stop.
 Green light on: This tells traffic to start or keep driving.
 Yellow light on: This tells traffic to drive slowly.
Sometimes there is a different light for using the crosswalks.

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 signalling system, and was one of the first people to get a patent for a traffic light.

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

 References 

 Other websites 

 FHWA Arterial Management Website, latest information on traffic signal operations
 Animations of various US signal phasings 
 SCATSSydney 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

Category:Traffic