I think there might be some confusion regarding "vitality," what vitality is on the railroad, and how vitality is "satisfied."
Vitality refers to the primary function of the railroad; the organization of train movement and mutiple train movements so that no two authorities for such movements conflict with, intrude upon, overlap each other.
This is the core to the railroad's existence. It is the vital process of the railroad. It "predates" signal systems, telegraphs, train orders, speed control, train control, centralized traffic control, cab signals with wayside signals, cab signals without wayside signals. It exists independently of any hardware, although not "software" as it is codified in the book of operating rules.
That this is in fact the essence to vitality can best be illustrated by a bit of the old "what if..." For example, what is every signal engineer's nightmare? The signal that displays the "false clear." "What if" the signal displays a false clear? Well, the signal is the rule, and complying with the rule, a falsely displayed clear, laps authorities and will lead to a collision.
What is every train dispatcher's nightmare?
Writing a "lap order." What if a "lap order" is written? Then acting on the order actualizes overlapping authorities and leads to collision; and train orders must be acted upon because train orders must be executed by those to whom the orders are addressed. Because executing the order is the rule, and in complying with the rule, the vitality of the railroad is jeopardized.
From this we derive the necessity to design signals, to design systems that authorize train movements, with the fail-safe feature-- so that a failure, which may very well be "invisible," , cannot lead to violation or lapping of authorities.
Vitality is not derived from the fail-safe functionality; the fail-safe functionality is necessitated by the vital process communicated in the apparatus.
Contrast those expressions of the vital process, the signal, the train order, with a means of enforcement, say automatic speed control. What if...
The cab signal displays "medium," and medium speed is defined in the BOR as not to exceed 30 mph. Train speed is 40 mph. The locomotive engineer acknowledges the cab signal change but takes longer than 8 seconds to take the necessary steps, i.e. applying the brake to reduce the speed of the train to 30 mph. As a matter of fact, after 12 seconds, the engineer realizes he/she has not taken proper action and has not received a penalty, at which point the proper action to bring the speed down to 30 mph is taken by the engineer.
Speed control failure. But not a vital failure, as the locomotive engineer is still required to reduce the speed of the train, and if he or she does that, complies with the rule as expressed by the cab signal, there is no risk of overlapping authorities.
In the case of the false clear, complying with the rule overlaps authorities. Vital failure. In the case of the speed control failure, complying with the rule expressed in the signal indication prevents overlapping authorities. The integrity of the vital process is not compromised.
Ron Lindsey loves to ask signal engineers "What's vital in dark territory?" and watch them struggle for an answer.
His reply is (usually) "the train sheet." He's correct, but that's not solely where vitality resides. It resides in the timetable, "the authority for the movement of regular trains. It contains classified schedules and special instructions."
And vitality resides in the operating rules, defining the operation of non-scheduled trains.
And vitality resides in the clearance cards issued prior to train dispatchment.
And vitality resides in the train registers at terminals.
Vitality resides, strangely enough, not in the centralization of railroad train control, but in the separation of authorities.
Hope that helps.
July 22, 2016
Bet you didn't know that the current FRA administrator "used to worry about 100 car trains" but "now worries about 200 car trains."
You didn't, did you? Shows how little credit the administrator gets for her commitment to safe train operations.
The average mainline long haul freight consist exceeded 100 cars per train (approximately 1 mile in length) back in the 1990s. Administrator Feinberg was born in 1978, which means she's been worringy about this stuff ever since her teens.
And you thought you had problems back in high school with the occasional zit.
All that time working for Daschle and the DNC and Facebook? Just day jobs to support her lifelong passion-- proper train sizing, proper train crew sizing.