DPU Question:
What happens if the DPU/mid train helper has a problem (i.e. lose telemetry)? Does it stop the train? Does it switch to some "safe mode", neutral?
Depending on the individual railroad policy/practices, if the DPU loses its communication, it stays in its present state for something like 60 minutes, unless the air brakes are applied, at which time the DPU unloads and drops to idle.