Ever Wondered Why Traffic Lights Are Red, Yellow, and Green? The Surprising Truth Revealed!


Why are the colours red, green and amber (or yellow) chosen for traffic lights?


The deliberate selection of red, green, and amber for traffic lights is rooted in a careful consideration of visibility, psychological impact, and their associations with safety. Each color serves a distinct purpose, contributing to effective communication on the road.

The Red Signal: Stop and Alert

  1. Visibility and Warmth:
    • Longest Wavelength: Red possesses the longest wavelength among the visible colors, ranging from 740 to 620 nm. This characteristic makes red highly visible in daylight and from significant distances, enhancing its effectiveness as a signal.
    • Stimulating Nerves: Red is a warm color that stimulates the nerves. Its association with warmth and energy adds to its attention-grabbing quality.
    • Universal Sign of Danger: The color red is universally recognized as a symbol of danger, and its use in traffic lights communicates a clear and immediate message: “STOP.”

The Green Signal: Go and Serenity

  1. Clear Visibility and Soothing Nature:
    • Medium Wavelength: Green falls in the middle of the visible light spectrum, with a wavelength ranging from 575 to 500 nm. This makes it clearly visible without being overly harsh on the eyes.
    • Cool Color and Peaceful Associations: Green is a cool color, reminiscent of nature, especially the color of grass. Its soothing nature makes it suitable for conveying a sense of peace and safety on the road, signaling “GO.”

The Amber Signal: Caution and Warning

  1. Intermediate Wavelength:
    • Wavelength Placement: Amber, situated between red and green in the visible light spectrum, has a wavelength ranging from 620 to 585 nm. This strategic placement makes it distinctly different from both red and green, creating a clear warning signal.
    • Warning Between Stop and Go: The amber light serves as a cautionary signal, indicating a transitional state between “STOP” and “GO.” Its purpose is to alert drivers to prepare for a change in traffic conditions.


The color choices for traffic lights go beyond mere aesthetics; they are a result of thoughtful considerations related to visibility, psychological impact, and universal recognition of danger and safety. The strategic placement of red, green, and amber creates a standardized and universally understood system that enhances road safety by effectively communicating essential messages to drivers.

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