The DC Metro actually (mostly) hasn&#x27;t used their automatic train control system in full automatic mode since a collision in 2009 that killed nine (for which the ATC system was directly responsible; a faulty circuit both forced a train to stop and rendered it invisible to the control system).<p>Safe train control seems like it needs a little more sophistication than &#x27;60s or &#x27;70s tech was able to give.  For one, it&#x27;s common sense that a train that disappears from the system isn&#x27;t really gone--  but the Metro system couldn&#x27;t take that into account.  Stuff like that should be pretty trivial today.