Valley can start the process by promote the self driving cars only in the silicon valley + SF, similar to how AirBnB and Uber started within a small region.
Valley has better environment, friendly government/regulation support.
The next version Tesla (in 5 years) might allow the car owner to get to work and auto "uber out" the car to "earn $$$" for the own - start with just Bay Area.
Or Google can
Step 1: Build a few thousand self driving "beta" cars to shuttle only their employees to/from work in year N.
Step 2: Uber out (Guber out) those self driving cars to pickup/drop off anyone in Bay Area, in year N+1.
If the model works for Bay Area, I can see other congested cities will clone it immediately to solve their own traffic problem.