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The colour-blindness explanation is a bit of a red herring in places outwith Japan. One can be totally red-green colour blind and still have no problem with tr
by JdeBP 8y ago
The colour-blindness explanation is a bit of a red herring in places outwith Japan.
One can be totally red-green colour blind and still have no problem with traffic lights in the U.K., for example. The stop lights are the ones at the top and the go lights are the ones at the bottom. Colour blindness, after all, does not prevent one from detecting which light is lit.
In countries where there might be both horizontal and vertical arrangements, this would not apply. But the U.K. only permits a single, vertical, layout for traffic lights with stop lights above go ones.
- DanBC 8y agoIf it's dark you can't see which light is at the top or bottom. You see a lit light, but can't see the unlit lights. The black boards with white borders are a relatively recent addition to traffic lights, and they're not fitted to all UK lights, which is why our green has a bit of blue added.
- JdeBP 8y agoNo. The official position (as quoted by someone who actually asked the Highways Agency) is that the ability to actually tell red from green is not necessary for traffic lights. The sequence of lights and the positions of the lights is adequate. * http://andrewhenley.co.uk/2012/02/colour-blindness-and-red-traffic-lights/ http://andrewhenley.co.uk/2012/02/colour-blindness-and-red-t... The statutory instrument that governs traffic lights does not actually state anything more specific than "green", so claims that "our green has a bit of blue added" are not borne out by the regulations that actually apply, which do not mandate any such thing. (The regulations are specific about sizes in mm and timings in s, with allowed margins of variability, so the lack of specifics as to colour is not simply because the regulations are generally vague.) Since it isn't a mandate in the first place, explanations that this is mandated for the benefit of the colour blind are ill-founded. * http://legislation.gov.uk/uksi/2016/362/schedule/14/part/2/made http://legislation.gov.uk/uksi/2016/362/schedule/14/part/2/m... The idea that colour changes are done to help the colour blind ironically comes to newspapers and Internet discussions from outwith the U.K., from research and proposals in countries where there are multiple allowed arrangements and position alone is not an unambiguous determiner.
- WorldMaker 8y agoAn easier explanation for more blue in traffic lights as they switch to LEDs is that blue LEDs are just boringly cheaper.
- brianwawok 8y agoWhat? Blue LEDs used to be the most expensive. Say $1 per in bulk vs 2 cents for red or green. Has that gone full circle?
- WorldMaker 8y agoThat is my understanding. Blue LEDs were last to be developed so they carried their R&D costs until more recently, but between efficiency breakthroughs and mass production improvements have passed through to being the cheapest to buy, especially in terms of lumens per dollar in places where you really need brightness such as traffic lights or overhead LED lighting in homes.
- DanBC 8y agoThere is less blue in trafic lights as they switch to LEDs because green LEDs are i) dirt cheap and ii) don't require the coloured filter that the older halogen heads did.
- DanBC 8y agoExcept SIRA make the filters added to halogen traffic lights, and they made the green filters a green blue specifically to help people with colourblindness see the difference. This is specified in BS EN 12368. All your government link says is "we don't want to admit there's a problem because then we'd have to pay for it". Please note that I didn't claim "traffic light manufacturers are forced by UK law to add blue".