From the reports Tesla has put out, the number of accidents of cars in self-driving modes is significantly less than when humans are driving, by an order or magnitudes.
Ideally they would not get in accidents at all, but even as of a few years ago they were already significantly safer than a human, so human driving needs to be reducing as much as possible.
Honestly if we could get full self driving of all cars then a lot of the human reactionary things aren’t as needed, they could drive perfectly and smoothly. ^.^
Also, a fun related video:
