I don’t know what you mean by critically. But everything from calling law enforcement for pedestrian and vehicle strikes to handling special operations (i.e. si

I don’t know what you mean by critically. But everything from calling law enforcement for pedestrian and vehicle strikes to handling special operations (i.e. single tracking in a work zone) uses wireless communication. There are also defect detection systems that rely on radio transmissions to indicate if a train is for example dragging equipment.