Even when the figures are adjusted to take into account that many accidents involving conventional cars go unreported, the study from the University of Michigan’s Transportation Research Institute found that the rate is still twice as high.

Yet it notes that it is making the comparison from a tiny pool of autonomous test cars, about 50 of them in California, versus 269 million conventional cars as of 2013. The self-driving cars have logged about 1.2 million miles in total, while the conventionals cumulatively go trillions of miles a year.

As a result, the total number of self-driving car accidents being used for comparison is the study is minuscule, 11. But that’s five times the rate of the accident rate in conventional cars, and there’s four times the injury rate, the study finds. The injuries, however, have all been minor.