Green/amber/red are from bottom to top in a road traffic signal. Order is reversed in a railway system. Why?

Question

I have noticed that in Indian traffic signal system colours are arranged in Green/Amber/Red from bottom to top for the roads, while in a railway signal system green is on top and red is at the bottom. Is there any scientific base for this?

Answer 1

Red on top for the roads is to accommodate those like my son, who is red green color blind and they look the same to him. He, and all others in that condition, know if the top light is lit, stop.

Railroads are a whole different story, and since most of them have rules against hiring a color blind engineer, they can put their lights in any combination they are happy about.

My uncle started as a fireman on steam trains, and eventually became an engineer, so that was where I went seeking a job when I was old enough. Unfortunately I also am red green color blind, although I can tell the difference between them. But they still would not hire me. Oh well.

Answer 2

Red is at bottom is due to historical reasons.
because most of station and rail lines in India have mechanical signals and in case of a mechanical failure the the valve will go down thus activating the red signal.
And in case of a signal failure you want to stop the trains rather than allowing to go on.

Answer 3

Well this is a good Q. My first thought was : So it can be seen from a distance. And need no slow.
But I could not find anything on it. Anyway, you made me read. I do know that the Signal is also the other way.

Read this ; [ read as in past tense] Did not get much.
http://en.wikipedia.org/wiki/Railway_signal#Position_light_signals

Answer 4

I don't know about any scientific point to the order but I am always told that the pattern is universally consistant in order to help people who are colorblind. Also this way people who aren't paying close attention can see and instantly recognize by the glow what color is lit.

Answer 5

Railroads that use purple / yellow / eco-friendly use them in a special way than motor automobile departments do. additionally they can get utilized in combos of two or 3 lights fixtures you do not see on the line. as an party: a unmarried railroad signal would coach "purple over yellow" often times, "yellow over purple" at different situations. (the diverse factors will denote the putting of a swap previous the signal.)

Answer 6

Very good observation & a good question. I'm also eagrly waiting to know the right answer.

Answer 7

good question. it is for those who are color blind but germany also has traffic light just like those of the rail way.

Answer 8

IN INDIA, THEY STAND ON THEIR HEADS WHEN OPERATING TRAINS

Answer 9

probably something that was established years ago..