[amazing_jose]

People still do not accept driverless trains or tubes yet. I remember talking with an AI expert a few years ago. The London's underground had a fully automated driverless prototype in the 70's. And here we are, in 2015 and only a toy driverless system in London (DLR).

[elros]

I'm not sure how much that's the case. For many years now, Paris' lines 1 and 14 have been fully automated. I've been to Toulouse last year and their whole subway system – albeit small – is automated. I'm also pretty sure that the train one takes from Copenhagen's airport to the main train station is fully automated, but I'm not sure about the other lines.

All in all, I think the public acceptance issue can be mitigated.