The metro in Copenhagen is driverless. http://en.wikipedia.org/wiki/Copenhagen_Metro

It's a union thing. In NYC, the L service is completely automated, but the union won't let trains run without two crew members. It was apparently hard enough to get the union to allow the G line (the least popular line that only runs half-size trains every 20 minutes) to run one-person operation on the weekends!

(Though if you don't need drivers, why do you care about the union? I guess the problem is that it will take maybe 50 years to convert the other lines to automatic operation. And you still need someone on the train to answer rider questions and handle medical/police issues.)

BART was meant to be fully automated. The "Fremont Flyer", which ended up in the parking lot, put an end to those plans.

List of driverless trains http://en.wikipedia.org/wiki/List_of_driverless_trains#Compl...

Although these are short-range, urban trains.

(http://en.wikipedia.org/wiki/List_of_driverless_trains)

Docklands light railway, in London, is driverless.

Unlike cars, trains can't stop on a dime if there's an obstruction on tracks. Nor can they swerve to avoid it.

The SkyTrain in Vancouver has been driverless since it was built in 1986. I don't think any such LTR systems have had drivers since then.