"Rod Speed" wrote in message
...

I dont. Thats why the traffic lights have the
red light at the top, green at the bottom;

Not clear what those color blind people do about the subsidiary
arrow lights that change color tho, presumably compare the color
they see with the main 3 light stack and see which grey matches
if they can't work it out from what the other cars are doing or
when they are at the head of the queue, when they get beeped
on a color change that they cannot see.

Ah, lights which have a single arrow that changes colour (as opposed to
separate arrows for each colour, of which only one is lit at any time) must
be an Australian thing. I've never seen any here in the UK.