Traffic signals at expressway on-ramps use red and green lights.
The signals work based on real-time traffic conditions and alternate between red and green lights to control the rate at which vehicles enter the highway.
What are the 3 traffic lights?
A three-color signal head should have three non-flashing lights which are red, amber and green, either arranged horizontally (on the side opposite to the direction of traffic) or vertically (with red on top).
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