Green, yellow and red: the origin of traffic light colors

Red signal to stop, yellow to be careful and green to go. It is very difficult for anyone today to look at a traffic light and not know what the colors represent, but who thought of organizing them that way and who established their meaning?

Red has been used as a danger signal for a long time, with records of the use of color by Roman legions for over 2, 000 years. However, its use as a light signal began in the mid-1830s on the English rail system, but in a slightly different way: while red was already used to indicate that drivers should stop, green was used to signal caution and a white light bulb. was that it signaled that the train was free to go.

This system only had one problem, reinforced around 1914: the red lens of one of the signals dropped, leaving only the light bulb exposed. Unaware of what it was and interpreting that white meant "released, " a train driver caused a tragic accident by colliding with another train. Railroads abolished white once and for all, and that's when the configuration we know today came into use, with green indicating release, and yellow - quite different from the other two - being used to signal caution. .

Even in the 19th century, the traffic of horses and carriages on the streets of London began to pose a danger to pedestrians, and it was there that a railway engineer named John Peake Knight came up with the idea of ​​adapting the rail system to the streets: while By day the traffic lights - handled by a policeman - showed signs to guide the traffic, at night they emitted the light signals.

The only problem with this system was that the lamps were powered by gas, and one day one of them eventually exploded and injured the policeman who operated it. In the absence of a safer alternative, the London government decided to suspend traffic lights until the electricity-powered version became available.

By the 1910s, in the United States, traffic was controlled by police officers who were at the center of the busiest intersections, on platforms that allowed them to have better visibility. Officers waved their arms to direct traffic - some even used green and red lights - while whistling to signal the change of signal.

Human guidance assistance was not set aside until the early 1920s, when the first three-color sequential traffic lights were deployed in Detroit, United States.

But what about the color-blind? Weren't colors thought of for them too? Well, most people with color perception deficiency can actually distinguish light green from light red. For those who can't, the standard adopted by most countries allows these people to identify signals by their positions: red at the top and green at the bottom.