Never.
The funny thing is your link is to an article where a self driving car was rear ended by an inattentive human...
The self driving cars don't need to be perfect, they need to be better than humans. I'm sure they're better than a lot of humans already...
As I said, A.I. and driverless cars simply cannot account for all the (stupid) human variables that occur while driving.
People blowing red lights and stop signs are probably the best example. I had someone just a few weeks ago blow through a left turn signal that was red in their direction and almost hit me head-on while I was doing 45mph obeying my traffic signal.
The jerk first made like he was going to stop, then accelerated and turned right in front of me. It was a good thing I had my foot off the accelerator and ready to hit the brake as I went through the intersection. If I hadn't, I'd have surely t-boned the idiot.
As it was, it was a good lesson for my youngest son who I'm teaching to drive. We were on our way to our church's parking lot for a driving lesson when it happened.
"That's why you have your foot ready to hit the brake going through an intersection, son. Because of idiots just like that moron!"