Think about it, you need to leave for work at a certain time? Just jump on Google Taxi (I use Google as they're the only company that has working driverless cars that I'm aware of at the moment), log-in using your account (that you either pay per ride, weekly, monthly, yearly, yearly+ etc.), calculate your commute, and reserve a car to show up at your house at that time and place. It takes you to your destination then shoots off to an electric or hydrogen-based fleet of these cars standing by at charging facilities in neighborhoods and cities all over the world. If they became ubiquitous enough you could have as little as a five to fifteen minute wait for a car.
However, I think the auto industry would fight like hell to keep this kind of system off the roads as it would severely dent auto sales. I mean hell, I know I wouldn't want a car if I could just have a subscription to a car. Especially if it wasn't just like Sedans. Imagine being able to rent a truck immediately at a moment's notice, then ride back home in a Sedan, all without having to worry about driving anywhere?
That's a world I would like to live in. Then once populations reached the 5,000+ ppl/km2 we could start building mag lev rails and get more into that kind of public transportation.