Why Red Color is used in Traffic Light to Stop Vehicle?

Red, in general is considered as sign of danger or warning. And when it comes to traffic lights, it does signal that there exists a potential hazard ahead, hence, it acts as an indicator for the motorists to stop. And, the motorists can turn left at a red signal, only if there is a sign to do so.

As said earlier, Red Means "stop", and during the good old days, traffic signals were designed for trains and not for cars. They were colors, red and green, and it was gas powered and in the event of a leak, it was bit dangerous. The rail road companies to ensure safety of its passengers, they introduced traffic lights; they used Red to stop, white to go and green for caution. But the train conductors faced few problems with the color white, which means to go, they could easily be mistaken for stars, as they looked bright white at night, hence the train conductors thought the way is clear and they can go, when it is really not the case.

Eventually, the Railway companies then started to move to green color, which means go and the color yellow to proceed with caution. They introduced these colors so that they can easily distinguish these colors from other colors, it has been long years, ever since these traffic lights have been put up, it has become standard everywhere, except in Japan, where you would find totally different color that signals for "go".

Red color indicates danger, it has got longest wavelength. It can be noticed from a greater distance when compared to other colors. Earlier the yellow color was used to caution the drivers, but as the yellow color had slightly shorter wavelength when compared to red, at the same time, they were not as short as green.

Whether you believe it or not, Yellow was previously used to mean stop, at least as far as the signage goes. Back in the year, 1900's, few stop signs had yellow color, but it was too hard to view a red sign in a poorly lit area. Eventually, few materials were developed, which were very highly reflective and the red stop signs were born.