The earliest ATO system on a full underground line...
The earliest ATO system on a full underground line was on the Barcelona Metro line 2 (now integrated on L5), which ran from 1963 until 1970 on its seven trains. Another one of the earliest examples of ATO was on the Victoria line of the London Underground, opened in 1968. The ATO system performs all functions of the driver except for the opening and closing of the doors. The driver only needs to press two buttons to start the train and, if the way is clear, then the train will automatically proceed to the next station.