Who decided traffic lights should be red amber and green why those colours?

I think it has to do with the fact that, for centuries, boats and ships have displayed a RED light on the left or port side of the boat and a GREEN light on the Starboard side of the boat. Red, obviously meaning that a boat showing a light of that color has the right of way over a boat showing a green light.

When traffic lights first were constructed, they just floowed the maritime tradition of Red for the cross traffic having the right of way and Green for the other traffic flow to have the right of way.

Probably evolved from railway practice.

The railways adopted red for stop at an early stage. red disc signals and red lamps on the Great western around 1840, white was shown to show all clear.

As signals evolved and trains became more numerous a signal to warn that the next one was red evolved, red being stop do not pass, and at night this "Distant" signal, showed a green light , however around 1900 the spread of electric lights and street lights made the clear "all right " indication impossible to distingusih so Green became "all right" and the Distant signals showed red, so some red signals meant "Stop" and some "be prepared to stop" so when the Railways reverted to private control as four groups in 1923, the signals changed so a horizontal red arm meant stop, horizontal yellow arm be prepared to stop and an inclined arm all clear, and the lamp indications changed to Red for Stop, Yellow be prepared to stop and Green Go, this was by a yellow light from an oil lamp and a lens, red for red, yellow for yellow, and Blue for Green!

Electric Coloured light signals followed, evolving into the modern signals with red at the bottom, yellow green and sometimes an extra yellow, 2 yellows means be prepared to stop at the next signal but one.

Road Traffic lights folowed this lead but the sequencing of Go, be prepared to stop, Stop, Go was inconvenient so a be prepared to start Red/yellow phase was added.

So there we are but whereas railway drivers have to prove they are not colour blind, road drivers may be colour blind so road traffic lights always have red at the top. Railways have red at normal eye level , and the other colours above or below.

Red indicated danger before traffic lights came along. Green is the opposite (port and starboard on a ship). Amber is somewhere in between.

They're colours that are suitably different from each other, whilst progress naturally in the spectrum - so they're aestetically pleasing.

But mainly it's because they're colours that can usually be seen by the colour blind.

Why not? Its the standard now a days. I guess because its easier to see from a distance and at night than lets say-

White

Grey

Black.

utilized in transportation for years. Boating in a channel, too. pink=trouble-free "wake-up call" and green=is the perfect shade for defusing solar glare (over blue, it is a night time shade i.e. planes).

because it rhymes of course

red = i could end up dead

green = keep driving keen

yellow = do i stop or go?

simple when you think about it ;)

i don't know, it might be becase they are such bright colors and they needed some sort of contrast, i'm not sure...

Your answer is here: http://www.inspirationline.com/Brainteaser/traffic...

they have to decide something