A row of Google self-driving cars are shown outside the Computer History Museum in Mountain View, Calif. For the first time, California's Department of Motor Vehicles knows how many self-driving cars are travelling on the state's public roads. The agency is issuing permits that let three companies test 29 vehicles on highways and in neighbourhoods. (File photo)Eric Risberg/The Associated Press
Self-driving cars are involved in accidents at a higher rate than conventional vehicles, but the self-driving cars aren't at fault, according to a report by two researchers at the University of Michigan.
Brandon Schoettle and Michael Sivak analyzed records of cars being tested by Google, Audi and Delphi in California, and discovered that self-driving cars are more than four times as likely to be in a crash than those which require a human operator. For every 1.6 million kilometres, self-driving cars were in 9.1 crashes, compared to 1.9 for human-operated cars. That number may be 4.1 because, according to researchers, people don't report all minor incidents to police.
Passengers in self-driving cars were four times as likely to get injured and the self-driving cars were rear-ended 50 per cent more often, but the accidents are less severe and occur at lower rates of speed.
"There may be a confusing message to discuss – it would be that you have this higher crash rate, but end up with safer situations than a conventional vehicle," Schoettle told Autoblog.
One of the benefits of self-driving cars, as touted by the companies making them, is they could eliminate traffic fatalities because the cars would eliminate human error behind the wheel. About 2,000 people in Canada and more than 35,000 in the United States die on the roads each year. According to the U.S. National Highway Traffic Safety Administration, 94 per cent of all traffic accidents are caused by human error.
This study puts that safety claim into question.
However, researchers found the self-driving cars weren't at fault, which is similar to the findings of a report by the California DMV.
"Our self-driving cars are being hit surprisingly often by other drivers, who are distracted and not paying attention to the road," wrote Chris Urmson, director of Google's self-driving cars unit, in a blog post. He mentioned one incident where an autonomous Lexus stopped at a green light because there was a lot of traffic and it didn't want to block the intersection. A car rear-ended the Lexus at 27 km/h.
"We publish the details of all crashes we've been involved in on our website each month, and there's a clear theme of human error and inattention," said a Google spokesperson to CNBC.
The study notes self-driving cars have been on the roads for far fewer kilometres when compared with conventional vehicles in the United States and self-driving vehicles aren't operated in demanding conditions, such as bad weather or snow. The study analyzed crash rates for 50 self-driving vehicles, which were driven a total of 2 million kilometres and compared it to 269 million regular vehicles driven 5 trillion kilometres.
"We currently cannot rule out, with a reasonable level of confidence, the possibility that the actual rates for self-driving vehicles are lower than for conventional vehicles," reads the study.
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