Study: Self-driving cars have higher accident rate

Chris Woodyard | USA TODAY

Even though they haven't been at fault, self-driving test cars are involved in crashes at five times the rate of conventional cars, a new study finds.

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.

The researchers, Brandon Schoettle and Michael Sivak, note the limitations, acknowledging their confidence levels could invalidate the overall finding of higher accident rates for self-driving cars.

In almost every case, the accidents involving self-driving cars have involved other cars crashing into them. They are often traveling at slow speeds. No accidents have been reported from self-driving cars going haywire and a human is always on board in case something goes wrong.

Eight of the 11 crashes occurred last year as more self-driving hit the road in California, where most of the testing is taking place.

Despite limitations of the study, "A Preliminary Analysis of Real-World Crashes Involving Self-Driving Vehicles," it reached some real conclusions.

The bottom line: Even though self-driving vehicles were not at fault in any crashes they were involved in and that injuries have of lower severity than for conventional cars, it appears they are getting in more accidents given their numbers.