How are the traffic lights colours chosen?


Question:

Why are the colours red, green and amber chosen for traffic lights?

Answer:

In the daylight, you can see the colour red more clearly than any other colour. It has the longest wavelength: 740 – 620 nm. That means red is visible from the farthest distance. It stimulates the nerves, being a warm colour. It is also the colour of blood and spells danger, hence “STOP”.

Green is also clearly visible, having a medium wavelength of 575 – 500 nm. It is a cool colour, the colour of grass, soothing to the nerves. It signifies peace and safety and hence “GO”.

Amber is another colour clearly visible, having a wavelength of 620 – 585 nm, between red and green in the visible light section of the electromagnetic spectrum. Hence, an amber light is used as a warning between “STOP” and “GO”.

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