How does a metro work without a driver?

Upon departure, the control centre orders the interlocking system to open a route. The system then checks the possibility of opening the route and positions the switches/points, before sending a movement order to the train’s on-board systems, which will:
– control acceleration and braking;
– determine the location of the train in real time via beacons positioned on the track, passing this information back to the control centre;
– check, in real time, that the train’s speed is compatible with the restrictions imposed on the line;
– position the train correctly with the beacons, in front of the platform doors, upon arrival in the station, before ordering the opening of the doors.

More information - Train operation