Replace “Rand’s novels” in your remarks with “the Holy Scripture,” and notice how disturbingly religious you sound. Ponder that.
In any case, Rand doesn’t understand railroading, and neither I’m afraid do you.
First, knowing whether one signal is faulty tells you nothing about whether another is faulty, any more than having my car inspected will tell whether yours is sound.
Second, redundant railway signals are somewhere between rare and nonexistent. You’re supposing that they can proceed from a “stop” signal to another “stop” signal, and if that signal is green, they can proceed. But that isn’t true: the next thing after an absolute signal is the switch, bridge or other track segment protected by the signal. If the Canonball were to pass another signal before encountering the danger point, then the signal in question would have been a permissive signal (i.e., “prepare to stop”), not an absolute signal (i.e., “stop”).
–Len.