Why traffic lights are red, green and yellow?

Ever wondered when travelling the vehicle will stop when the traffic signal goes RED, start when it goes GREEN and slow down when it goes YELLOW / AMBER. But why only red, green or yellow why not some other color say brown, indigo or pink for that matter? Well, there are perfect reasons for the colors to be actually red, green and yellow. Let's dive in further to understand why this is the case!

Traffic lights came into existence to navigate and manage the traffic or let's say ongoing vehicles at multiple road intersections [3-way, 4-way]. This was done to avoid any collisions that might result in damage to property and even loss to life.

Initially instead of traffic lights, it is said traffic personnel operating through traffic towers installed at the intersections. So, it was more manual rather than automatic like it is today. Also, if we go back a few years before traffic lights came onto road we can see that traffic lights were brought into place to manage the train network.

With the slight change to the current scenario, then GREEN was used to signify caution rather than GO while WHITE light was used to indicate good to go. This was said to create slight problems as drivers would get confused with the white lights emitted from the stars. This led to further discussions which eventually resulted in GREEN being considered for indicating GO while color YELLOW was used to signify CAUTION.

Coming back to the roads, we can attribute the invention of traffic lights indicator i.e. the tri color and in four direction to William Potts who came up with the invention in 1920.Further a decade down around 1935 came the standards stating the use of road signs and the colors red, yellow, green to be used ahead. Now coming to why these colors specifically its more related to the properties of these colors.

Every color has different properties i.e. wavelength and frequency which proved a major influence in the decision making. We all know about the color VIBGYOR [ Violet Indigo Blue Green Yellow Orange Red ]. Here the violet has smaller wavelength and larger frequency while red has bigger wavelength and smaller frequency. This property ensures that RED is visible more from a longer distance than any other color.

This is also why we see a reddish tint in the sky during sunsets. Check below article to know more about it.

Why sunrise is blue and sunsets are red.

Coming back to the topic, we got to know why red is used to indicate stop. Also influencing this reason is from earlier times red was used to mark danger, fatal, harm etc. And because of higher wavelength it can travel much further which is also useful in rains, mist, fog plus addition of reflective lights make it very much useful in the cause to alert the vehicles.

Yellow being the middle of the RED and GREEN travels less further than RED yet more than GREEN and is used tor advising caution. We can see why school buses, warning signs are with color yellow as well since the visibility of the color yellow is high.

For the color green it is also associated to have a more relaxing effect also with comparatively smaller wavelength and lesser amount of distance covered it was a better option than YELLOW for signifying GO.

Do you know in Japan rather than GREEN, color BLUE was used and still the color used for indicating the GO is a bluish tint of green. The reasoning could be attributed to the time where centuries before it is said that Japan had everything integrated into red, black, white, blue color. Even to signify something as green the word for color blue 'ao' was used. For example something called as aoringo  or aodake which would literally translate into blue apple or blue bamboo and would actually mean green apple and green bamboo respectively.

So, to maintain their alignment with international law and also to be binding with their heritage bluish shade of green came into existence to indicate GO in Japan.

Now you know why the colors of traffic lights are the way they are. There is an explanation for everything right? Just about letting the curious mind work its way.

That's about it for now. Until next time let the curious mind talks a bit more. 

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