There's a reason they're testing in Phoenix. It has almost no Inclement weather. Throw a little snow, mud, or sleet in there and it gets hairy fast. Level 2 is basically the 20% of effort in 80/20. It's exponential effort from then on out.
When autonomous drivers have the same or fewer injuries per billion miles driven as human drivers, then for all practical purposes it doesn't matter if it's level 4 or level 5.
If so why go through all this trouble to creat autonomous vehicles? I, for one, am glad this was not the prevailing attitude when commercial airliner regulatory bodies were set up.
1. They're cheaper. This sounds crude, until you realize that this makes things like buses and shared rides far more viable. Meaning millions of people have a better commute and collectively save many lifetimes worth of time. It can also mean less air pollution, due to less traffic congestion (this only applies if congestion pricing is done), which will also save lives.
2. They can always get better over time. Humans can't.
3. Fewer parking lots are needed, which makes cities far more pleasant to live in.
4. Disabled, elderly people and children have better mobility, and aren't dependent on others to drive them everywhere.
IMO autonomous vehicles are just going to further push public transit into something just for the poor. All the convenience and comfort and privacy of sitting in your own vehicle, but now you don't have to drive yourself! Why would you choose anything else?
buses would be cheaper to run if they didn't need a driver
So, yes savings. Nyah on your "unions defending humans against exploitation are the worst thing ever" narrative.
Also, if you don't have to accommodate a human driver and controls, many safety features, bulky gasoline tank, and trunk space, automobile design could change radically. Self-driving taxicabs that look like small pods, or covered golf carts, could be used for individual travel, increasing space efficiency.
So we can sleep in the car. Or watch netflix. Or drink. Saving 1+ million per year while you know, very nice, is not the main reason for doing this.
I think the future of self driving vehicles will just be inclement weather delays like we have with flying.
One of the lessons of engineering history that self-driving car proponents fail to grasp is that promising technology often fails to get traction because it can't close the final 5%. Supersonic aircraft, for example, have effectively been derailed by people on the ground near airports complaining about sonic booms. VTOL aircraft never replaced aircraft because of control problems. Flying wing aircraft never became popular for similar reasons.
Also, the prospect of being accidentally killed in a horrible car crash is less poignant if the alternative is more time spent in Chandler.