California Details Driverless Car Crashes in New Report

— -- No driver, no problem? Not so fast.

The biggest threat to self-driving cars may actually be human drivers, a new report says.

California officials have released a report detailing car accidents involving six self-driving vehicles. Most of the cars were in autonomous mode when the accidents occurred, however the reports obtained by the Associated Press reveal other drivers were at fault in the accidents.

None of the crashes were serious and no injuries were reported, according to the AP. Seven companies with a fleet of 48 self-driving cars among them are licensed to test autonomous driving technology in California.

Google has been leading the charge with its self-driving cars. The search giant revealed last month its 20 test vehicles had traveled more than 1.7 million miles -- and had racked up a few dings along the way.

Google said the cars have been involved in 11 minor accidents resulting in light damage and no injuries.

"Not once was the self-driving car the cause of the accident," Chris Urmson, lead of Google's driverless car project, wrote in a Medium post last month.

The self-driving cars are driven a total of 10,000 miles per week, mostly on city streets, with a human sitting in the driver's seat.

While software and sensors can help the cars take action faster than a human driver, Urmson wrote that "sometimes we won’t be able to overcome the realities of speed and distance; sometimes we’ll get hit just waiting for a light to change."