People are only just realising why traffic lights are red, amber and green
PEOPLE are only now realising why traffic lights are red, amber and green – and it’s not down to what you might think.
The colours, which appear on traffic lights across the world, were chosen for a very specific set of reasons.
Before cars were commonly in use train drivers needed a way to navigate the growing railway.
On the original train system, red meant stop, white meant go and green indicated “proceed with caution”.
The colour red was used because it is the colour with the longest wavelength, meaning it can be seen from further away.
This allowed train drivers to react quickly enough to stop before reaching the light.
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As cars first became popular in the 1920s police officers used whistles to direct traffic.
But soon another solution was needed and the modern day traffic light was invented.
It followed the same system used by the railway.
However, white caused issues for the driver who often mistook the colour for something else.
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Any mistakes could cause serious accident so a new colour had to be chosen.
As yellow was more distinguishable, it was made the colour for proceed with caution.
The very first traffic light came into operation in December 1868 in Parliament Square, London.
The system was composed of two mobile signs attached to pivoting arms that were manipulated by a lever.
The post was topped with a gas-lit semaphore to ensure visibility.
At night a red light would command "Stop" and a green light would mean use "Caution".
In 1912, the first electric traffic light was developed by Salt Lake City policeman Lester Wire, which had two colours, red and green, as well as a buzzer to alert drivers to an imminent change.
The first three-colour lights were created by Detroit cop William Potts in 1920, which used amber, the same colour as used on the railways.
Initially though, there were no rules about the kind of lights or the pattern that had to be used.
So they would look different wherever you want.
A universal system was created in 1935 by the Federal Highway Administration.
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It published the Manual on Uniform Traffic Control Devices, which set standards for all signs and signals.
This manual decided all traffic lights had to be red, yellow and green.
