My experience as a human driver is that most accidents can be avoided by either (A) slowing down in ambiguous situations, or (B) aborting that lane change (usually because two cars are attempting to go into the same space).

Those behaviors are easily improved upon by software. Dealing with lane changes is something software is likely to be vastly better at, because they can point sensors in all directions -- I only have one set of eyes.

Furthermore, a lot of horrific accidents are because of bizarre unexpected things that the human does not react to in a timely fashion precisely they are so far out of the normal scope of traffic flow.

For example, what if a car coming the other direction drifts in front of you on a rainy night? This is an unfortunately common and very lethal kind of accident in rural areas. It will take you 1 to 3 seconds to interpret the scenarios and react appropriately. (You only get 3-4 seconds before your are killed.) A computer can instantly recognize that car 100 yards away is maneuvering in a potentially lethal manner and begin slowing down right now. That buys more time for everyone.