You missed the root cause. It is impossible to get close to L4 using public shadow/safety driving. And the deaths it has caused, with thousands more to come when these folks run accident scenarios are needless.
It is impossible to drive the one trillion miles or spend over $300B to stumble and restumble on all the scenarios necessary to complete the effort. In addition the process harms people for no reason. This occurs two ways. The first is through handover or fall back. A process that cannot be made safe for most complex scenarios, by any monitoring and notification system, because they cannot provide the time to regain proper situational awareness and do the right thing the right way, especially in time critical scenarios. The other dangerous area is training the systems to handle accident scenarios. In order do that AV makers will have to run thousands of accident scenarios thousands of times. that will cause thousands of injuries and deaths.
The solution is to switch 99/9% of the public shadow/safety driving to simulation using aerospace/DoD technology.
Another fatality — Tesla’s Autopilot is not the problem — Public Shadow and Safety Driving is