very few people actually believe those two things. First, reducing congestion is pretty far down on the list of proposed benefits. My number one is not being run down by some idiot fondling their phone when they pretending to be driving. The car sharing idea is an unrelated fantasy. Sure, A.I. cars might make it a little more effective, but if it were such an attractive idea we'd all be using taxis already.
Second, this has nothing to do with "strong" AI. What is making self-driving cars possible is the Google approach of throwing massive computational resources and some clever domain specific algorithms at the problem and observing what works.
Finally, I'd take an AI car that sits there confused at a show-off cyclist (or whatever) over the Natural Idiot who plows on confident that their "above-average" skills will get them out of anything their stupidity can get them into.