I'm sure in specific environments the accident rate is lower, but I think we are dealing with selectivity bias. Google isn't going to drive their cars in any circumstances where they aren't extremely confident in the car's performance.

I hope we see autonomous cars that are safer than humans in the next couple of years, but I'm jaded to technical progress. It seems like it is always 10 times slower than what we originally thought was possible.

For crying out loud, how long have we been hearing that solar is going to change the world, and yet, solar power won't be energy neutral (meaning they provide more energy than it takes to make them) until 2020, only 80 years after they were invented.

http://www.popsci.com/science/article/2013-04/solar-panels-now-make-more-electricity-they-use