Seat availability indicators on UK GWR trains

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On the UK GWR trains (or at least the high speed), they have seat availability indicators

When a seat is reserved a light will go red for the section of the route it is reserved then turns back to green if I reserved

We had reserved seats but didn't like it as it was facing backwards so managed to find 2 green light seats facing the direction of travel.




At Reading station, the red light became green as the seat is unreserved from that station onward

 

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These are nice when there are strikes which reduce service to a handful of trains a day and services run with 2x the amount of pax as seats.