I happened to be thinking about the problem of displaying "or" this morning, at Ely. The signalling at Ely is such that you can sometimes know a train will be going into either platform 1, or into platforms "2 or 3", before you know for sure which of 2 or 3 it will be using. Platforms 2 and 3 are different sides of the same island platform, across a subway from platform 1. In the event of a change from platform 1 to platform "2 or 3" it would be useful to start people moving to the platform 2/3 island before you know for sure which platform it will be using. Similarly at Cambridge, knowing a train is using platforms "1 or 4", or platforms "7 or 8", is useful even if you don't know for sure exactly which platform it will be.Just because it cannot go into the booked platform, does not mean any particular alternative platform is certain and then CIS can not display an “or”.
One workaround for this problem might be to just pick (for Ely) either platform 2 or 3 at random at display it on the screens as soon as you can. That would get people moving to the correct area. If it turns out you've displayed the wrong platform, an additional last-minute change from, say, platform 2 to 3 is far less disruptive than a late change from 1 to 3. With more modern screens, you could easily add a simple visual indication that means "not 100% certain but you'll be in the right area if you move to that platform now", e.g. different colour, or different background colour, or put an asterisk next to the platform number - none of which require invasive changes to the overall layout of the screens.
A different workaround, involving much more infrastructure work (new signage etc.), might be to have platform areas, e.g. platform 1 is area A, and platforms 2 and.3 are area B. You could display "area B" before you knew for sure which of platforms 2 or 3 was going to be used.
Everything I've just said is, of course, useless where a train can still reach two different island platforms. But there must be many stations where it is useful.
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