Unfortunately this is one of those things that you can't significantly develop/test on closed private streets. They need the scale, and the public traffic, and the idiots in the drunkards and the kids speeding. The only thing that's going to stop them from working on autopilot will be that it's no longer financially reasonable to keep going. Even a couple handfuls of deaths aren't going to stop them.
Should a couple handfuls of deaths if as you said you can't test it any other way? Autopilot systems could already be saving thousands of lives if more widely deployed and a lack of good reliable autopilot systems has the opportunity cost of blood on our hands. Human drivers are well established to be dangerous. Testing and release of autopilot systems should be done as safely as possible, but to think the first decade or so of these systems will be flawless seems unreasonable.
Same happened with airplanes
The fact is that most technology that we take for granted today went through a similar evolutionary phase with public use before they became as safe as they are now, especially cars themselves. For well over a century, the automobile has made countless leaps and bounds in safety improvements due to data gathered from public use studies.
We learn by doing.
This is a most excellent place for technology news and articles.
