I think there's a strong recognition that self-driving vehicles, when they can be made to happen generally, will be a significant social good. And that it's tricky to get there unless society is willing to put something out onto the streets.
It's taken fifty or more years of popular human-driven vehicles to get to the stage that most of our cars are pretty safe, and quite a lot of effort in improving road design too.
Eventually, though, I suspect it won't be solved until we redesign the roads. A significant part of rail safety is that the signalling system can sense whether there is a train on a stretch of line. (via the rather simple technique that the axles form an electrical connection between the two rails) Right now, it's as if we're trying to do autonomous traffic by an ant colony model -- independent agents that know nothing about each other except what they can sense. Which is always going to be harder than if the road can help them out too.