Lots [1][2]. These have seen most deployment in closed networks (e.g. subways, or remote mining railways [3]), but experiments on "normal" interconnected networks are ongoing.

[1] https://en.wikipedia.org/wiki/Automatic_train_operation [2] https://en.wikipedia.org/wiki/List_of_automated_train_system... [3] https://www.railwaygazette.com/australasia/rio-tinto-complet...