New Signals on Jubilee Line Platforms

The white visual illuminates when the train has a limit of movement authority. They're generally provided at locations where platforms may be staffed, to assist staff making announcements and raising the SATS baton.

There is a certain amount of inconsistency with the precise moment the visual illuminates. Some places it comes on before the driver's limit of movement authority advances, whilst at other places is can be a couple of seconds later. Likewise there's also massive inconsistency with the Seltrac system actually issuing a limit of movement authority relative to the driver's countdown. At plenty of locations on the Northern Line it doesn't happen until about 5 seconds countdown, so if you wait until this happens before closing the doors then you're guaranteed to leave late. Which means in reality many drivers tend to close the doors on about 8 seconds, and re-open if the limit of movement authority doesn't advance for any reason. This is sort of bad practice, although there's no risk of moving off as the train won't move without a limit of movement authority, it's confusing for station staff too as they don't have the countdown display so don't know what's going on.