I've been thinking a bit about good places to adopt this early.

Lānaʻi might be a good candidate: absolute isolation from other road systems, a small population (3000 people), and a single owner (Larry Ellison) who's just the sort of filthy rich technophile who might be willing to replace an entire island's cars.

Singapore could be the first major city to make the move, due to its authoritarian government (hey, I don't like it, but it might make this easier), strict rules to keep the stock of vehicles relatively new, and relative isolation from other road systems (only two bridges to Malaysia).