readout to display whether the rolling-stock is accelerating or decelerating. It can be used for animation or HUD, such as the up and down arrows next to the TGV speed meter.
https://youtu.be/UYEp575J9GY?si=PnYWM6LbO6uVw6gR

another is detect if sway event is triggered, readout will play animation when train sway, it cau use for commuter train handle