I spoke to a ticket guy on a southern train as we pulled in to Victoria today after he announced ‘there will be a 15 second delay before the doors open after we arrive at the station’. I asked why this was.
Get this, the train knows how many doors to open (because it might be a 12 car train at an 8 car-long station platform) based on GPS. It knows it’s at such and such a station and opens the doors accordingly, no need to trust the driver.
So why the delay at Victoria? Becuase IT CANT SEE THE GPS SATELLITES! At Victoria you can’t see the sky. So they have to trust the driver at Victoria after all, and he takes 15 seconds to shut the train off and override the GPS system the guard said.