"Generally the computer will slow to suit conditions and then stop if anything approaching a bad situation occurs."
I tend to agree. There are _very_ few "unforseeable accidents" on the road. It usually takes at least 3 bad decisions on the part of multiple people to cause a crash, even when one of the decisions may be bad roadway engineering.
Humans have a tendency to "press on regardless" and vastly underestimate both their reaction time and stopping distances whilst vastly overestimating situational awareness and driving ability.
As one example, kids never "just appear from nowhere" despite many claims to the contrary. A properly trained driver will not only spot the movement of feet under a parked car ahead but be slowing down long before the child steps out into the traffic lane. Computers don't suffer from psychological tunnel vision and will be in a better position to see hazards coming from all angles.