How Do You Go At Traffic Lights?

According to Wikipedia, this image shows a number 44 or 49, but someone who is deuteranopic may not be able to see it.
According to Wikipedia, this image shows a number 44 or 49, but someone who is deuteranopic may not be able to see it.
“How do you go at traffic lights?” is one of the questions that really shits me when I mention to someone that I’m colour-blind. “Oh no, it’s fine”, I say politely, when what I really mean to say is “do you think I’m a total idiot who can’t pick the difference between top, middle and bottom?”

I never actually knew I was colour-blind until about twenty years ago when I had to go and have a “physical” for superannuation (or something like that). After a series of tests, the doctor said I was fine “aside from being colour-blind”.

“What?”, I thought to myself. “How can you possibly diagnose me as being colour-blind at the age of twenty-five?” I remember asking the doctor.

Over the years I’ve never thought much about it until earlier this week when, at work, we were discussing web-site design. There was one colour-combination that everyone else seemed to think was okay, but which I found really distressing. I could barely make out the text against the background.

And then I went online and discovered it was a particular combination of colours that people with a particular form of color-blindness have the most common problem with. Some, apparently, can’t see the combination at all.

And so tonight I went online with an interest in finding out more about my own particular form of color-blindness.

After doing a couple of online tests, I’ve discovered my form of colour-blindness is called, Deuteranopic

According to Wikipedia…

Deuteranopia (1% of males): Lacking the medium-wavelength cones, those affected are again unable to distinguish between colors in the green-yellow-red section of the spectrum. Their neutral point is at a slightly longer wavelength, 498 nm. The deuteranope suffers the same hue discrimination problems as the protanope, but without the abnormal dimming. The names red, orange, yellow, and green really mean very little to him aside from being different names that every one else around him seems to be able to agree on. Similarly, violet, lavender, purple, and blue, seem to be too many names to use logically for hues that all look alike to him. This is one of the rarer forms of colorblindness making up about 1% of the male population, also known as Daltonism after John Dalton. (Dalton’s diagnosis was confirmed as deuteranopia in 1995, some 150 years after his death, by DNA analysis of his preserved eyeball.) Deuteranopic unilateral dichromats report that with only their deuteranopic eye open, they see wavelengths below the neutral point as blue and those above it as yellow.

In the above photograph, I can’t see a single thing. No number is clearly visible at all.

So there you go… an explanation for the reason why I sometimes dress appallingly.

6 Replies to “How Do You Go At Traffic Lights?”

  1. I have the same condition which was diagnosed in my teens or thereabouts and I cannot see any number(s) in the photograph.

    I was refused a drivers license in China because of the condition following their mandatory testing procedures which amusingly did not include any check of whether I could, in fact, drive.

    One thing that annoys me when others learn I have the condition is when they pull out a bunch of coloured pencils or something similar and ask me to name the colours as though I am a circus act.

  2. Me neither, I’m not colour blind but it’s not a pretty picture – it’s not just a colour issue, the characters are not very well defined at all.

  3. I tried to imagine what it must be like to have Deuteranopia, and concluded that it was impossible. Then I googled it and found a couple of simulators. Apparently fire engines are khaki in your world. Is it true that you can’t tell the fire brigade apart from the army?

  4. Dear James

    I have been nominated for an overseas posting to Sweden. I am also a color deficient person but I dont find it difficult to follow the traffic lights . In fact I am considered a pretty safe driver by my family and friends.

    Would like to know from you , if a color blindness test is manadatory for obtaining a driving license in Sweden ?


    Seema Bhatia

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