I can't see fully autonomous vehicles in my lifetime. Everyone will chime in to tell me about advances in robotics, ML, sensor technology and fusion, how many miles Google cars have driven, so on and so forth. I have approximately 30 more years before departing this mortal coil.

Roads are tough. Sometimes they're covered in snow, ice, rain with poor visibility. Sometimes they're well constructed, other times they're in disrepair. That's just the technical side of the issue.

The social side (at least in the US) is much more difficult. In the foreseeable future, any AV will have to share the road with "classic" cars, driven by humans of modest computing power. Trying to anticipate how they will interact should be interesting to say the least. And in our hyper-litigious and hyper-protective society, the clash between AVs and traditional cars will be difficult to resolve.