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Traffic signals are instruments that use changing lights to control traffic. The different lights tell drivers what to do.
Light cycles[change | change source]
- Red light on: This tells drivers to stop.
- Red and amber/yellow lights both on: In the United Kingdom, this signals that the light is about to turn green. In some parts of the United States, it signals that pedestrians can cross the road. In other parts of the United States, traffic signals do not use the red and yellow lights together, and traffic lights go straight from red to green.
- Green light on: This means "go."
- Amber/yellow light on: This tells drivers to stop if they can safely, because the light is about to turn red.
History[change | change source]
William Potts, a police officer, invented the first traffic light with three colors.