At Alphabet's annual stockholder meeting, chairman Eric Schmidt answered an audience question about how close self-driving cars are to reality. Schmidt remarked it's very hard to give a precise answer to this question because it depends a lot on factors that are out of the industry's control.
Consensus within the parent company of Google puts it at "some years, not decades". The legal framework is one of the most often cited roadblocks, but surprisingly, Schmidt said it will also greatly depend on where you are:
"It's very hard to know. The consensus I think within the company is that it's some years, not decades, but it is very much dependent on regulation. And it also depends on where you are. It's obviously a great deal easier to do this in areas that, for example, have ample parking."
The comment about parking space is a bit weird as companies like Google often promise self-driving cars will reduce the need for parking space. I think what he means here is that self-driving cars will still require parking spaces at first, as fully-autonomous cars with no human present in the car may be a bigger regulatory hurdle to clear than a self-driving car with a human that can intervene in case something goes wrong.