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Passenger info screens - why yellow?
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pdeaves
Established Member
It's more expensive to change something that is not yet life expired than to leave it be. Other colours are used where screens have had to be replaced (or are equipment trials).
Bletchleyite
Veteran Member
Amber LEDs are bright and clear and long-life, at the time these started being deployed white LEDs were expensive and unreliable. This is changing, so most new displays seem to be white.
Colour displays will cost 3 times for the LEDs as much due to 3 times as many LEDs.
mallard
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Multi-colour LED bulbs have existed for quite a while... They're not "full colour", they emit one of two or three colours depending on the exact voltage or polarity. They're used in displays like this one (link to store listing of tri-colour LED matrix display). Obviously such LEDs need slightly more complex control circuitry, but it's nothing extravagant.
The trend for on-train displays at least seems to be to replace LED matrix panels with LCD displays (and set them up with low-contrast while-on-blue text for some reason), I expect this trend will eventually find its way to stations.
Bletchleyite
Veteran Member
LCD was a fad a while ago and died out due to being unreliable (though European operators quite like station displays made of rows of monochrome small-TV-sized panels). I think the new ones on stations might be more likely to be off the shelf OLED TV panels which not only gives more flexibility of display but are cheaper due to the mass manufacture.
Plasma of course rapidly died out due to burn-in issues.
Metroman62
Member
Contrast is important, so bright text on a dark background is very easy to read (especially if you have poor vision). The new screens on trains are sometimes awful, white text on pale blue may look pretty but is harder to read than white text on a dark blue background. The current yellow / orange may look boring, but is often quite easy to read (as white on black is).
agbrs_Jack
Member
Congleton finally got a CIS on each platform just before Christmas (we were the 8th busiest station in the UK without one!).
The text is white.
The text is white.
pdeaves
Established Member
Provided that it hits that 'sweet spot' before there's so much contrast it becomes unreadable. I personally am not a fan of burnt retinas! There must exist a level that is not too much for people with more sensitive eyes, but is not too little for those with poor sight but few set-ups seem to find it. In the same way that simply making an announcement louder does not necessarily help those with impaired hearing (where slowly and clearly may be of more use).
Exactly the maximum contrast sensitivity for humans eye is at the yellow end of orange.
TfL buses used yellow writing on black for ages till BoJo insisted on reverting to the traditional white on black making them harder to read.
Could you post a reference for that (purely for personal interest!)?
Maximum sensitivity is in the green rather than amber, I thought (https://www.olympus-lifescience.com/en/microscope-resource/primer/lightandcolor/humanvisionintro/ agrees with that), and it's interesting if the maximum contrast sensitivity is away from that. There's also the question of focus, and one definitely wants to avoid the bluer end of the spectrum for that reason (some discussion here: https://biology.stackexchange.com/questions/30600/why-cant-the-human-eye-focus-blue-light — we've evolved to “auto-focus” so that orange-green is more in focus, since that turned out to be more useful!
Either way, it seems that monochromatic green/yellow/orange displays are likely to be easier to read/focus than bluer/whiter/multicoloured ones. GWR seemed to be switching to white too in some places (e.g. new platform displays towards east end at Didcot) though perhaps has now decided to stick with amber (e.g. new displays toward north end at Oxford). I hope the latter since to my eye it;s definitely clearer. Three-colour LED displays (red/green/yellow) must be noticeably cheaper than full colour, and would give some of the advantages of multi-colour to highlight information, without the focus/legibility problems of including blue in the mixture. I vaguely recollect that I might have seen such displays in use in the London Underground somewhere.
Bletchleyite
Veteran Member
Avoiding green is also sensible in railway applications so as not to cause confusion with a green signal.
Not forgetting those pesky yellow ones too.
OLED panels aren't cheaper than LED backlit LCDs yet. They also have burn-in issues so still images displayed for long periods cancreate problems. That problem is being solved on TVs by shuffling pixel illumination around in a way that is normally unnoticeable to viewers. Station displays however display the same large areas of pixels at high levle of illumination for hours on end. That likely to create patches of wear that make the displays unusable in time. LED backlit panels have been commodity products for a decade now and are quite reliable. CFL backed LCD panels do have life issues though.
Llanigraham
On Moderation
Tri-colour LEDs are quite common, and coming down in price. All they need are extra wires.
Just one example:
https://uk.rs-online.com/web/p/prod...ae_6QqBiU9pV6W1Cj8QaAnKIEALw_wcB&gclsrc=aw.ds
Bletchleyite
Veteran Member
I suppose the amber of a PIS display is fairly well distinguishable from the colour of a yellow signal, the colour is more like an amber traffic light.
OLED has issues too. Often too faint for bright sunlit locations, so need to be much brighter which can then lead to other problems. For the railway that has little money for many things, faded OLED screens would soon be the norm I suspect.
I think simple dot matrix LED panels are fine for most uses. The new white ones can do shades of grey to highlight certain things and I think a higher resolution would be better, so you could convey things like train carriage loadings with more detail.
I'll dig some stuff out.Could you post a reference for that (purely for personal interest!)?
Maximum sensitivity is in the green rather than amber, I thought (https://www.olympus-lifescience.com/en/microscope-resource/primer/lightandcolor/humanvisionintro/ agrees with that), and it's interesting if the maximum contrast sensitivity is away from that. There's also the question of focus, and one definitely wants to avoid the bluer end of the spectrum for that reason (some discussion here: https://biology.stackexchange.com/questions/30600/why-cant-the-human-eye-focus-blue-light — we've evolved to “auto-focus” so that orange-green is more in focus, since that turned out to be more useful!
Either way, it seems that monochromatic green/yellow/orange displays are likely to be easier to read/focus than bluer/whiter/multicoloured ones. GWR seemed to be switching to white too in some places (e.g. new platform displays towards east end at Didcot) though perhaps has now decided to stick with amber (e.g. new displays toward north end at Oxford). I hope the latter since to my eye it;s definitely clearer. Three-colour LED displays (red/green/yellow) must be noticeably cheaper than full colour, and would give some of the advantages of multi-colour to highlight information, without the focus/legibility problems of including blue in the mixture. I vaguely recollect that I might have seen such displays in use in the London Underground somewhere.
Worth noting the railway uses orange HiVis but it is very difficult to make UV stable paint in those shades so it ended up with yellower fronts for trains.
Didn't we already go through this with Railtrack? I distinctly remember them going nuts for LCD panels on all stations showing information (or often a helpful windows error dialog), which became completely unreadable as soon as the sun came out. The ones at Waterloo were particularly useless. The yellow LED panels were an absolute blessing when they replaced them.
I would have thought the main risk with multicoloured displays is that they start to look cluttered and confusing. If I don't know what a colour is supposed to mean (and how would I ever find out?), then I just get anxious that I'm missing some important information.
I would have thought the main risk with multicoloured displays is that they start to look cluttered and confusing. If I don't know what a colour is supposed to mean (and how would I ever find out?), then I just get anxious that I'm missing some important information.
Bletchleyite
Veteran Member
Those weren't LCD, they were plasma, which is a massively inferior technology with massive burn-in problems.
Metroman62
Member
Marylebone used to have a departure board made of red LED s. When the sun came our, you (I) could not read it. They replaced it with an orange version, much better in bright sunlight.
With the exception being the above cab window screens on a 700. They're near invisible in daylight. Waaaay too dim.
47271
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I was thinking that at Brighton the other day. Somehow via the buildings and canopies winter sun was full on the departure board, a standard orange screen set up, and yet I could still read it very easily.
It's obviously because each LED is brighter than the sun!
Orange on black works perfectly, the only ones I find better is white on blue.
Not a fan of the white on black background, I find it difficult to read even rather close up in perfect weather. I'm glad Southern & SE have opted not to go white on the new CIS. The ones new-ish ones on the TL core I find hard to read too. I do think my eyes are a little more sensitive to light than the average person mind.
Not a fan of the white on black background, I find it difficult to read even rather close up in perfect weather. I'm glad Southern & SE have opted not to go white on the new CIS. The ones new-ish ones on the TL core I find hard to read too. I do think my eyes are a little more sensitive to light than the average person mind.
Metal_gee_man
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I do love the Thameslink CIS they probably cost a bomb, and probably aren't the most waterproof but they are something like the future IMO
47271
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God knows, but I could read it!
Jonfun
Established Member
I find orange on black really hard to read as the screen just becomes a sea of orange dots.
White on black is much easier; alternatively alternating orange *and* white on black breaks it up a bit.
By far the easiest to read in my opinion is the white on blue, like they used to have for the main departure board at Manchester Piccadilly, and as favoured in Europe.
White on black is much easier; alternatively alternating orange *and* white on black breaks it up a bit.
By far the easiest to read in my opinion is the white on blue, like they used to have for the main departure board at Manchester Piccadilly, and as favoured in Europe.
Bletchleyite
Veteran Member
There's also an orange LED version of that knocking around.
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