Self-driving cars only work on some roads specifically adapted for self-driving cars, and even then they require a team of specialists constantly monitoring them (so it's not very self-driving, the driver just moved to another place).

If they require a specially designed roads, they don't replace cars, they replace trams. And trams are much more efficient, so they don't really replace even them.

You can't put a self-driving car on a random road and expect it to work.