Regarding the above, could someone confirm whether my understanding is correct: that the "radio control" mentioned in the "blogger's analysis" above consists of nonverbal transmissions identifying train location, direction, speed, etc. which in turn provide wayside and in-cab indications of conditions ahead, not "roger, over, out" type verbal communication such as exists in air traffic control; i.e., signal (wayside and in-cab) indications are not superseded by verbal radio communications other than official orders in the event of signal failure authorizing the overriding of signal indications according to the rules. Regarding the last sentence, even under PTC, the [train] operators attach primary significance to block signals, which are driven by the radio transmissions referred to.