The disclosure came after The Associated Press successfully argued to the Department of Motor Vehicles that the agency was improperly withholding the information.
According to the reports, most of the cars were in self-driving mode when the accidents happened, and the other driver caused the accident. None of the crashes were serious enough to injure the person the state requires to sit behind the wheel, and the reports say none of the people in the other cars were treated for injuries either.
The companies that operated the cars — tech titan Google and parts supplier Delphi Automotive — submitted their own accounts of the accidents. Police have only confirmed investigating the Delphi crash.
Led by Google, self-driving cars have been running on public roads since 2009. It was only in September, however, that the DMV officially began permitting the testing — and specifically requiring companies to file accident reports.
Until now, the agency said it could not reveal details about self-driving car accidents, citing state law making collision reports confidential.
The fact that the agency refused to release the reports bothered critics, who said the public should know how the cars of the future were faring today.
After the DMV denied a public records request, AP argued that the agency was incorrectly citing the confidentiality requirement and that the public has an interest in understanding how these experimental vehicles are performing as they drive public streets and highways.
"Unlocking these records and sharing them with the public are in keeping with AP's longstanding efforts nationwide to bring about greater transparency in government agencies," AP spokesman Paul Colford said.
In a letter that accompanied the documents, DMV attorney Roger Sato wrote, "After further review, DMV has determined that it is possible to release the factual information related to the autonomous vehicle reports" as long as the drivers' personal information and other details such as insurance information is blacked out.
While eight companies have permission to test 82 self-driving cars in California, Google has driven the most miles driven (about 1.8 million) and licensed the most prototypes (53).
After several years of revealing little about crashes, Google has in recent weeks become more open about their number and nature.
After AP reported last month that there had been three Google accidents and one Delphi accident, Google self-driving car project leader Chris Urmson revealed in a blog post that its cars had been involved in eight other accidents between 2010 and July 2014.
DMV officials had not been aware of those eight until an April conference call with Google, agency spokeswoman Jessica Gonzalez said.
In California, a driver is required to report to the DMV any accident involving more than $750 of property damage.
A Google spokeswoman could not say whether the company had filed reports on any of the initial eight accidents to the DMV, and said she could not provide damage estimates because repairs were done in-house, without a bill.
The DMV said it could not search its records for earlier reports without date and location information that Google has provided to neither AP nor the agency.
At Google's annual shareholders meeting earlier this month, co-founder Sergey Brin told a longtime critic with the non-profit Consumer Watchdog that releasing accident reports would serve no purpose because Urmson's blog post detailed the accidents. Two days later, Google launched a website which offered short narratives describing each collision.
The documents that the DMV released Thursday offered few new details, other than the date and time of the accidents and the make and model of the other cars.
Five accidents involved Lexus SUVs that Google outfitted with sensors and cameras. The sixth involved an Audi retrofitted by Delphi. All were in the Silicon Valley cities of Mountain View or Palo Alto.
In four of Google's five accidents, the Lexus was in self-driving mode, according to the reports. In the fifth, the SUV began applying its brakes when it sensed a 2015 Audi S6 had run a stop sign and was about to hit it; the person behind the wheel took control of the Lexus just before the Audi hits its right rear.
The crash of the Delphi car occurred when the car was waiting at an intersection.
It is hard to know for sure how typical Google's experience is. With four accidents in the past approximately 100,000 miles, Google's recent accident rate appears to be higher than the federally reported national average. About 0.3 "property-damage-only crashes" happen per 100,000 miles driven, according to the National Highway Traffic Safety Administration.
Google officials have said they are proud of the safety record. Noting that as many as 5 million minor accidents are not reported to authorities each year, they conclude that the cluster of "fender benders" in recent months reflects the true rate at which minor accidents happen.
This summer, Google plans to begin testing the latest version of its self-driving car — a stout, two-seat vehicle it commissioned — on the streets of its headquarters city, Mountain View.
Google's blog post about the accidents: (http://tinyurl.com/mp59fs6)
Google's description of the collisions: (http://tinyurl.com/p4os7dp)
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