If all the money on self driving cars would have been put into public transport (driverless on rails is a solved issue) and pushing shared car ownership instead, we might actually get somewhere towards congestion-free cities.
We can already have congestion free-cities today, no new technology nor public transport required. We had the technology for quite a while now: congestion charging.
It works really well in Singapore to control congestion, and also worked well in London when they adopted it afterwards.
Public transport also works quite well in many places around the world.
It also used to work really well in North America in the past. A past when the continent was much poorer. (I'm mostly talking about USA plus Canada here.)
Public transport only works when after you step off the bus or train, you can get to your destination on foot. Density is outlawed in much of the USA and Canada.
https://www.youtube.com/watch?v=MnyeRlMsTgI&t=416s starts a good section about Fake London, Ontario. At great expense, they built a new train line. But approximately no one uses it, because you can't get anywhere when leaving the stations. The video shows an example of a station where the closest other building is about 150m away. And that's just a single building. The next ones are even further.
Land use restrictions and minimum parking requirements are a major roadblock. And just throwing money at public transit directly won't solve those.
Shared car ownership is an interesting idea. Uber can be seen as one implementation of this concept. It can be done profitably, but I'm not sure it has much impact on the shape of cities?
In the grand scheme of things, there's not much money being put into self-driving cars so far. A quick Googling gives a Forbes article that suggests about 200 billion USD.
If all the money on self driving cars would have been put into public transport (driverless on rails is a solved issue) and pushing shared car ownership instead, we might actually get somewhere towards congestion-free cities.