That's the scary and also dangerous part: the behavior might be ok at some point, and might fail at another point. Tesla's (and NTSB) investigations will likely find out what went wrong in this particular accident and on this part of the road, and likely will improve the systems. But users are certainly not enough aware of that kind of risk: they might try the Autopilot, see that it works, and trust that if it worked, it will work again and again and again... On a daily commute for example, if it worked many days in a row, and then fails for some reason (technical, external, whatever), the user will likely fail to notice.

> On a daily commute for example, if it worked many days in a row, and then fails for some reason (technical, external, whatever), the user will likely fail to notice

Yup. This is why I won't get into a self-driving car until they're fully driverless.

Drivers become less attentive as the system gets better.

During the day there is a black gap clearly visible. During the night I imagine that black line just disappears.

Since nobody noticed it, it failed with a AP2 car in night time, and succeeded with a AP1 car in daytime