Intrusion Detection Warning System not Fail-safe
In the photo below, the gray box on the chain link fence and the black cables connected to it are part of the Intrusion Detection Warning System, or IDW.
The alarm panel in the Train Control Rooms (TCRs) is basically a fire alarm panel. It is:
a) Very expensive – thousands of dollars per panel.
b) Much more complex than necessary.
c)Not fail safe.
So not only did Metro spend much more than it needed to ($Thousands x # of stations w/IDW) they ended up with a critical safety related system that is not fail safe.
By not fail safe I mean that the entire alarm panel could be ripped off the wall and no one would know. Central Control and/or Maintenance Control (OCC and/or MOC) would not get an alarm.
Any number of failures could result in MOC/OCC not receiving an alarm.
It is the opposite of fail-safe – the relay must be energized (have voltage applied to it) in order to create an alarm. In a fail-safe circuit, any failure – broken wire, loose connection, power failure, etc – will cause the relay to be de-energized (or “drop”) and create an alarm and/or a safer state.
What this means is, it is possible that if a freight train or its cargo (or a car or truck) crashed through the fence and onto the Metro tracks no one would know – at least not until the first train plowed into it.
As with everything else mentioned on this blog, this has been brought to management’s attention but no action has ever been taken.