How trains are driverless?
I can think of the DLR in London and not many more.
They must be a whole lot more to automate and yet they haven't managed to do it yet.
Quite a lot of 'little' people-movers the size of DLR are centrally controlled - usually to be expected for new construction, and some retrofit going on.
But the comparison isn't valid because trains effectively operate in just one dimension (being constrained to the track), and entail a zillion fewer things that should they go wrong unexpectedly might lead to disaster.
The realization that sophisticated "unmanned" aircraft e.g. GlobalHawk operate very successfully makes one forget that they're remotely piloted, not pilot-less.