I'm saying that a rules based system with "slow down arbitrarily whenever the hell you want" is unlikely to meld well with existing traffic and is likely to cause as well as avoid unsafe situations.
I believe that might mean that autonomous vehicles are not yet ready for road testing if that is commonly required by the current state of the art. (I last worked on autonomous vehicles in 1991; ours was entirely rules-based and we tested on public roads in addition to private tracks. Ours was bad enough that the human driver hovered over the red E-shut button and was always paying attention. It was harder work than just driving the damn thing yourself, but we had to test in order to make progress. I'm sure loads has improved since then.)
I also don't think that zero fatalities is a realistic goal nor is it the standard that should unduly inhibit progress. People have been dying in transit on foot, on horseback, on bikes, and in cars. This is a version of the trolley problem. I don't mind and in fact actively prefer a system improvement that allows 100 deaths while saving 500, even if the 100 is entirely disjoint from the counter factual 500.
In this specific case, I believe the autonomous car allowed 1 death that would have also been allowed by a human driver in the same circumstances, so it's a push.