How a vigilance pedal turns silence into a stop
A train’s vigilance pedal is a simple way to check that the driver is still able to act. While operating the train, the driver holds the pedal down. If they become incapacitated and their foot comes off it, the system detects that the expected input has stopped.
The system does not treat the first missed input as proof of a medical emergency. It sounds an alarm, giving an alert driver a chance to respond. If the driver remains unresponsive, the train applies its brakes automatically. The alarm is therefore both a warning and a brief opportunity to prevent an unnecessary stop.
Why the train needs an automatic fallback
A person who loses consciousness may no longer be able to control speed or respond to changing conditions. The pedal cannot diagnose why the driver has stopped responding; it only detects the missing action. Its purpose is to make that absence trigger a predictable response rather than leave the train moving under no active control.
Stopping a train is not instantaneous: its mass and speed mean braking takes time and distance. Even so, beginning the stop without waiting for someone else to notice can limit how long the train continues unchecked. The safety principle is simple: when the operator can no longer confirm control, the train moves toward stopping.
