The Parisian metro has a L4 line since 1980s...on an isolated track, without significant branching, controlled by a single computer from a command center. Yet emergencies are still escalated to humans, even things as common as "somebody is stuck in the door".
In other words, getting trains to L4 is straightforward, and there's been a rollout for half a century. Making the jump to "doesn't even need the driver to handle emergencies," that's a task comparable in scope to getting cars from L2 to L4.
In other words, getting trains to L4 is straightforward, and there's been a rollout for half a century. Making the jump to "doesn't even need the driver to handle emergencies," that's a task comparable in scope to getting cars from L2 to L4.