Metro and its Train Problems

As details continue to come out about Metro and its train problems, it's becoming clear to me that Metro is not careful enough with passenger safety.

This article says that Metro believes that the defect in the train circuitry would have been "impossible" to detect.  I beg to differ.  While perhaps someone staring at the screen might not notice something, one of the advantages of having a computer monitoring things is that you can use the computer to stare at the screen (or watch for strange things happening).  What the computer should have been programmed to notice is a train suddenly disappearing.  Even on Metro, trains don't mysteriously disappear.  They move into the next signal block further down the line.  If a train disappears without moving into the next signal block down the line, then that, to me, signifies a Problem.  The computer should have been programmed to notice disappearing trains and report them.

BART (Bay Area Rapid Transit) had the same problem.  Rene posted to Twitter about this.