I personally do not think auto-pilot will help with congestion at all unless they are used as carpool vehicles to pick up and drop off people on route. Once you have auto-pilot, you have another group of the population that don't drive now that will start using auto pilots. I'm mostly referring to old people who don't drive but there are many others who don't drive due to limitations.

Or simply people who don't like driving in traffic, its boring and annoying but you still have to pay attention and can't do much else except listen to a podcast or music. If the car drove itself you could work just as you can in a train or as a passenger. This would make a 1h commute much more tolerable. I can see many more people who don't want to drive deciding to use private autonomous vehicles over crowded/dirty public transit.