My biggest problem with this approach is humans are terrible at paying attention to things that don't demand 100% focus.
A car that drives itself 99% of the time, but fails catastrophically the other 1% is doomed to failure. The human operator won't be engaged enough to take over that 1%. At least not without airline levels of squawks and beeps and wheel shakers and even that might not be enough - airlines don't have to worry about children chasing balls into busy streets, etc. And the pilots are highly trained - drivers are not.
A car that drives itself 99% of the time, but fails catastrophically the other 1% is doomed to failure. The human operator won't be engaged enough to take over that 1%. At least not without airline levels of squawks and beeps and wheel shakers and even that might not be enough - airlines don't have to worry about children chasing balls into busy streets, etc. And the pilots are highly trained - drivers are not.