So far, self-driving cars have been involved in 11 reported accidents during 1.2 million miles of travel. A preliminary study by researchers at the University of Michigan crunches the numbers and finds that self-driving cars so far have a crash rate that is about double that of conventional cars. The researchers do note caveats, including that their confidence levels could invalidate that the finding that the self-driving accident rate is higher.
Keep in mind that conventional vehicles in the U.S. travel over 3 trillion miles annually and are involved in more than 10 million reported accidents. The four reported injuries are less severe than the rate of severe injuries reported for conventional vehicles. In addition, the study notes that all of the accidents so far are the result of conventional cars crashing into the self-driving cars.
Since human error is responsible for more than 90 percent of vehicle crashes, one possible conclusion is that roadways will be safer once most cars are self-driving.