Inside the train all may seem normal, but outside there's a splendidly geeky thing to spot. Every S Stock carriage has an external light containing a lower strip which glows orange to show that the doors are open, and above that another strip which has always remained dark. That upper strip now lights up white when a train is ready to go, giving a few seconds warning that the automatic system is cleared to depart. Previously 'movement authority' was indicated by a green signal at the end of the platform, but now it's the trains themselves which display the information. This only happens where the computers are in control, so currently only between Latimer Road and Hammersmith, but eventually everyone'll be able to use the
white lights as a signal that it's time to jump aboard.