The issue of "sprawl" is a worthwhile topic...
...while the degree that self-driving cars will have upon promoting it is just silly.
As for stopping sprawl, I suggest two solutions:
A) Make cities more desirable to those who now choose to live outside cities.
B) Slow population expansion, which in the US is exclusively caused by immigration, and globally due to subsidized birth rates.
Both these topics seem to be too uncomfortable for progressives to address.