Earlier quoted context omitted.
The D.C. Metro system was planed in the '60 and constructed in the '70s, with the first operations starting in 1976. It too is based on electro-mechanical relays, although it's more ambitious, after the operator closes the doors and sees all is fine, he hits a "go" button and the system automatically takes the train to the next station, avoiding collisions as long as the "is there a train in the next segment" sensor…
The DC Metro actually (mostly) hasn'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). Safe train control seems like it needs a little more sophistication than '60s or '70s tech was able to give. For one, it's comm…
The system was replaced a couple of years ago with a new one, to allow an even higher frequency of service.