Earlier quoted context omitted.
Usually the train driver is in radio contact with central control and can request changes to the points, signals etc so they can make unscheduled stops. For example if there's a medical emergency on board and a passenger needs to be transferred to an ambulance. Of course doing this can have ripple effects on other services, and if a common factor has severely delayed dozens of different trains, the central control ro…
Best example of this is when they hit someone. Train has to stop, control center has no say in it. (For longer “technical” delays, keep an eye out for emergency vehicles without their sirens on.)
And then you have cascading delays across a whole region.