I believe from what I read is that some of these driverless car companies in the US are releasing their fleet, flooding the street 24/7. Some of them will take up parking places, cause traffic jam, or just stall in the middle of the road.
Maybe it's different in the Europe, where there's stricter regulation, since from the comments here, many who are okay with driverless car are mostly from European countries. Unless if you own stock in those companies, then there's incentive caused bias.
Just like how drugs need to go on multiple clinical trials before going on the mass market, I believe that if you want driverless vehicles, a lot of testing is needed.
The main rationale of these companies is not to bring a safer environment with driverless cars, the main rationale is how to get rid of gig workers that causes problems to Uber or Lyft, problems such as demanding living wage, proper employment status, unions, etc.
Empty cars on roads or anywhere they don't need to be, should be treated like empty residential properties should. Tax them for wasting resources that others could use.