The obvious is that people won't mind driving as much.
1. Longer commutes. Possibly combined with a "work from car" arrangement for some white collar work. This would give people the ability to live farther from employment hubs and might upend (or simply end) suburbs.
2. Less traffic. Traffic density could increase with driverless cars even as speed holds relatively constant because driverless cars could safely tailgate other driverless cars. This would boost cities dramatically since traffic into cities is a major growth deterrent.
3. More economies of scale. A&P was the Walmart of it's day because it was cheaper than the general store. But A&P missed the suburbs and went into decline as more familiar grocery stores became popular. Then the Big Boxes came in. Driverless cars may take this another level. Imagine an Amazon with drones on the road.
What else? I imagine the driverless cars will change the landscape of the country as much as cars did in the early 20th centuries and the freeway system did in the mid 20th century.