General self-driving is an incredibly hard problem.

Even humans make a lot of mistakes and kill people at a significant rate, to the extent that if the concept were introduced today, there is no way that the general public would be allowed to drive as they do; at a minimum, driving tests would be WAY more stringent and applied every 5 years or so.

Driving on a well-maintained motorway/highway (so all the road markings are present!) is the easiest problem to solve. Even so, the self driving system has to keep track of all other cars in all sorts of light conditions, and react appropriately to unexpected queues, or just bad driving by other users. But I think that full-autonomous-motorway driving is at least possible with current technology. And that would be useful; drive to the motorway, press the 'self drive' button, snooze for a few hours and get a wake up alarm 10 minutes before your turn off.

Now, once you get off of the highway, onto poorly maintained rural routes, or even worse towns and cities with all of their bad roads, missing markings, visual distractions, cycles, people, and all the rest, that's a whole new level of complexity. As a human, you can easily work out that a child is about to step off of the pavement in front of you, because evolution has hard wired us to judge the intentions of others. For a computer that's an incredibly hard task. Just working out what is road or pavement in an old town centre can be tough. That's a real general-intelligence problem, and it's why full all-roads self-driving is still a way off.