But, what it is good at is being a simple to administer test that can differentiate between normal and abnormal colour vision easily.
That’s all the Railway cares about, normal or not. Not (if you’ll excuse the pun) ‘shades of grey.’
But the world isn't like that.
No other test that I can think of works in the way the Ishihara test does.
The driving test, for example, allows you to have certain mistakes but still pass. Hell, even the other railway tests allow you to have mistakes and still pass. Plus, [Ishihara] doesn't test for blue/yellow deficiency. So either the railway doesn't care that much about yellow signals, or it unwittingly allows people who may not be able to see yellow properly drive trains - which is it?
The point is does the applicant have ‘normal’ colour vision. As defined by the Ishihara test.
But why use a test that's wildly out of date?
That's like saying we should use the driving test from 50 years ago and that'll be okay for the current standard.
It does do it efficiently though.
I agree - just too efficient.
If it's okay to use a simple pass/fail as a standard, maybe all tests should be like that. One mistake, you fail.
Yes, don't get me wrong, one mistake and hundreds could die on the railways. It's not about allowing those with colour deficiency drive trains left right and centre. It's about allowing those who
can see colours fine - with no problems - drive trains if they so wish.
Colour deficiency isn't a clear yes/no problem, so the test used shouldn't be either.
I be totally wrong on this but doesn’t Ishasria quickly and easily identify people with a red-green deficiency? These people will not be able to interpret signals, for obvious reasons, so there’d be little point in sending them for further testing once they’re identified.
Yes and no.
Yes it does quickly identify those with a red-green deficiency. But there is a growing amount of people who can interpret signals as clearly as a colour-normal person, but cannot pass the test.
When people accept that colourblind doesn't mean thatyou can't see red or green, then the learning will begin. It's just ignorance. Much like 50 years ago, we as a nation were ignorant to many other disabilities. Even just a few years ago, we were ignorant to mental health issues compared with now.
For someone who it doesn't affect, it's dead easy not to really care. But for those who it
does affect, it's hard to accept, when it's
clearly in need of change, and is on the cusp of changing.