If it was not "cut in" or failed en route, the system could still be manipulated to apply the brakes pneumatically such as on the older AM (P) schedule braking.
If it was not "cut in" or failed en route, the system could still be manipulated to apply the brakes pneumatically. This would still allow the train to stop, but deceleration would take longer such as on the older AM (P) schedule braking.