Blue railway signals?

Since they put on clothes to keep the ice and snow out?

So we're born indecent? That doesn't make sense whether you believe in god or evolution.

That's very specific. I didn't know it could be so. Did you cause it harm in some way?

You may not know *of* many but I bet you know quite a lot. It's about 8% of men, although many of them do not realise that, or discover it until tested later in life.

I think you'd notice when you saw all the traffic light bulbs looking identical. You're not safe to drive if you can't tell red from green.

I suspect they don't look *identical*, just not as distinct as to someone with normal colour vision. They would use the position to confirm which is which.

Correct. Which is why colour-blindness is not even notifiable to the DVLA. Driving a train is of course totally different as braking needs to be commenced way earlier and the position of the light cannot be determined at that point.

SteveW

I'm not colour blind, and I don't look directly at the traffic lights. I see red or green out of the corner of my eye and act accordingly. If they suddenly became the same or very similar colours, I'd make mistakes regularly. Are you saying a colour blind person already knows to look carefully at things? I can't think of where else colour and position are that important.

The only colour blind person I know says red and green look IDENTICAL (presumably in his eyes the red and green receptors are shorted together somehow). They're only different if one is lighter than the other, but then light green and light red are the same, and dark red and dark green are the same, so that might depend on the traffic light design and the position of the sun.

The only person I know be colour-blind has a bit of a problem with green/greeny-blue/bluey-green/blue

You don't get red receptors, you get green ones and yellowy-green ones that largely overlap plus blue ones that are horribly ineffective compared to the other two types.

====snip====

You can't detect colour 'out of the corner of your eye' (nor very much detail for that matter). However, what peripheral vision is good for, is detecting changes in luminance levels which can alert you to potential danger or reward (depending on whether you're the 'prey' or the 'predator').

Traffic lights don't rely solely upon colour for their function since the position of the 'stop', 'prepare to stop' and 'proceed with caution' lamps has been standardised, not only with colour blindness in mind but also to speed up response/interpretation times in general.

Distant railway signals can't benefit from the layout of the signalling lamps, leaving colour as the only useful marker which makes good colour vision a vital requirement in the qualification of any train driver.

Wrong. I can immediately spot brake lights or red traffic lights 45 degrees from where I'm looking. I in fact once did an eyesight test to see how far I could see in periphery. So as the tester knew I could really see the object, I had to say what colour it was. Colour can be seen in your full field of vision.

And you need to know it's red so you know it's danger, and not just a white headlight, or a green traffic light.

Only if you look straight at them, which I never do. If you're colour blind and have to do so, you're impeding your driving abilities, as you're no longer concentrating on the area you need to look at.

colour is not needed in driving , take the traffic light for example , the top is red the bottom green , you don't need to see the colour

You do if you want to see more than one thing at a time, which is a basic requirement of driving.

Let's say you're driving along, watching the car in front of you, or a pedestrian ahead. A properly sighted driver will know if the lights ahead are red or green without moving their eyes. A colour blind driver will have to look at the lights, and take their concentration and central vision off the important things in front of them. Colour blind drivers are unsafe and should be banned from driving.

well they aren't and they won't be so you don't get your way

It would go a long way to explaining why I frequently see drivers doing absolutely stupid things.

Mind you, being colourblind won't matter soon, as cars are now using any f****ng colour they like for lights. I see BMWs with orange sidelights! Orange means indicator, end of story.

Perhaps more importantly, road signals are two-aspect. Anything that's not green means stop - if you're close enough to worry about whether it's amber or red, you're close enough to see if it's the middle or top light. Also the "green" is actually a blue-green, there's enough blue in it to make a very clear contrast with red, even for people with red-green colour-blindness (like me). Other signals also have non-colour cues - for example the motorway warning signs flash amber up and down for a warning, but red side-to-side for a lane or road closure.

On the railways, you need to distinguish yellow (stop at the next signal) from red (stop here) in the dark, rain, snow or fog, while travelling at 100mph or more. Perfect colour vision is mandatory to work on the railway.

Mike