Considering in 2014 there were 32,675 motor vehicle deaths, 2,300,000 motor vehicle related injuries and 6,100,000 reported accidents in general (which means a likely higher number of accidents though not sure by how much) [1] it would not surprise me that even buggy software could do a better job than humans who tend to become distracted with almost anything. Though I'm not sure about extreme conditions like snow, heavy fog and rain, etc.
As much as I love driving (and I really do) I can't wait for autonomous vehicles. Considering it's a, if I remember correctly, a 1.7% chance in your lifetime that you'll be killed in an auto accident in the United States (and higher of a chance that you'll known someone killed) that's just way to high of a number for me (especially being a Dad).