1. The driver is supposed to be able to take over if something goes wrong.
2. Every single time a Tesla has an accident, they can patch all cars and every single Tesla in the world will learn from this and not repeat it. When a human drives into a cop car (and this happens a lot), only that one human learns from it. This is why sled driving automobiles are so powerful and are already less accident prone than humans.
As the cars learn from mistakes, you can be sure that the accident rates go down.
https://futurism.com/the-byte/tesla-safety-autopilot-safer-human