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.

Before traffic lights came into operation, traffic was controlled by police officers using whistles and lights to keep traffic flowing and to let drivers know when to either stop or go.

2

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 which was used 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 though was brought in, in 1935 by the Federal Highway Administration which set up the Manual on Uniform Traffic Control Devices which set standards for all signs and signals.

The manual established that traffic lights had to be red, yellow and green everywhere.

That system was taken from the one used on the railways.

On the original train system, red meant stop, white meant go and green indicated “proceed with caution”.

However, white caused issues for the driver who could mistake the colour for being something else and cause an accident.

As yellow was more distinguishable, it was made the colour for 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.

Which is help when it comes to warning drivers they need to stop for safety reasons.

2