I disagree with the assertion that people getting around with self driving cars will take up more space in cities. You seem to be imagining that the cars carry one person each, and are privately owned by that person.
The smart way to do it is with car sharing, which only works because the cars are self driving. The cars won’t park on the street (or in parking garages), they’ll simply drive to the next person to pick up. And in many cases there will be several people per car. And the more people use this, the more efficient it can be since the right size car will pick you up, and it will be able to plan routes super efficiently. Even if the car is a van with 8 people in it, it will get you to work quicker than public transportation — less waiting, no changing busses, less stopping along the way, no need to park.