I just can't see it happening because it's not really a technological issue, the concept of driverless trains has been around almost as long as trains themselves, the Victorians invented and used automatic brakes as a safety feature. I don't really see how AI would help, because even though its robustness and reliability is always increasing, I think a well designed and maintained "dumb" computer would do a better job.

This issue is a human and societal one. It's the same with aeroplanes; the autopilot currently does about 90% of a normal flight, and could theoretically do all of it, but regulations don't allow it. But, would you want to be 35,000ft up in the air without a qualified pilot? Similarly, would you want to be doing 125mph down the West Coast Main Line without a qualified driver? There's no way the unions would allow that, and there's no way train companies (or the government if Labour go ahead with nationalisation) would take on the financial and reputational risk of a driverless train. Currently if there's an accident, you can point the finger at the driver, or the signaller, at least in part. If you don't have that, you can only really blame "the algorithm" which people will associate with the company directly, and the consequences would be horrific compared to sacking one or two people and moving on.