> Cars can park away from you and come back to pick you up. This should alleviate parking problems, and reduce parking-space-search based congestion on the street.
I know this sounds nice for just a moment, but if you consider it longer, it's awful. It won't decrease congestion, it will increase it. Why?
1. Cars will still be searching for parking: many people will prefer to have their car nearby. It's not as if every car will altruistically drive to a far-off area. Since self driving cars have more patience than humans, they'll be on the road much longer searching for their parking. It may be more efficient to keep the car circling the block, which is even worse.
2. Parking availability is a major inhibitor of car trips, especially in cities. This is a good thing. If it becomes easier to "park" (ie leave your car driving on the street or send it away), that will induce more car trips, and more car trips means more congestion, until there's a new equilibrium (maybe a 7-minute parking search is eliminated, but it's replaced with 7+ minutes of traffic).
3. Pick-up and drop-off in cities is already difficult with rideshare services. If all personal vehicles are doing it as well, they'll definitely congest the curb lanes more. This is definitely a more solvable problem than the first two, but still an annoyance.
And for what it's worth, the 4-hour commute may be a bit far fetched, but it's hard to deny that many wouldn't mind an extra 20 minutes of commute time in traffic if they can relax, nap, read, watch a show, etc. People will chose that option more, adding more trips and more congestion, until an equilibrium is reached. Maybe it won't be 4-hour commute times but it will be a major increase and added congestion.
All of these extra miles traveled searching for parking, and adding extra congestion, are disastrous to cities and neighborhoods. Sure, the fossil fuel emissions alone would be awful, but suppose (charitably) that all autonomous vehicles are electric, and assume that their electricity generation is emission free (unrealistic for decades). The weight of EV batteries will dramatically increase road wear and tear, and they'll increase the pollution due to rubber tires, which are already the major source of microplastic pollution. And of course, it's a dramatic waste of energy from the power grid. And all of this is ignoring that dedicating that much road space storing to idling and parked vehicles is a no-good, terrible, awful way to utilize public space in a city or neighborhood, when it could be used by some efficient public transit, parks, and safer infrastructure for personal vehicles when necessary.