In a blog post, Chris Urmson, the head of Google’s self-driving vehicle program, writes that the self-driving Google Lexus was stopped at an intersection near the company’s Mountain View, Calif., headquarters on July 1.

The three people on board complained of minor whiplash, were checked out at a hospital and cleared to go back to work following the July 1 collision, Google said on Thursday.

“After we’d stopped, a auto slammed into the back of us at 17 mph-and it hadn’t braked at all”. Despite all the facts showing human error as the primary cause, Google kept waiting for 15 days before reporting the accident. (Our cars, with safety drivers aboard, are now self-driving about 10,000 miles per week, which is about what a typical American adult drives in a year.) It’s particularly telling that we’re getting hit more often now that the majority of our driving is on surface streets rather than freeways; this is exactly where you’d expect a lot of minor, usually-unreported collisions to happen. We’ll take all this as a signal that we’re starting to compare favorably with human drivers.

Google and other automotive manufacturers and suppliers have said the technology to build self-driving cars should be ready by 2020. “The driver of the other auto also complained of neck and back pain”.

Since 2009, Google’s cars have been involved in 14 crashes. There were also two passengers.

Earlier this month the company announced with a blog post that it has chosen Austin, Texas, as a new testing location for its self-driving auto project. Within about a second, a fourth vehicle rear-ended the Google auto at about 17mph (27.35km/h). According to official accounts of the accident, the Google auto was stationary at the time when another driver crashed into it at around 17mph. The rear bumper of the auto was slightly damaged and the vehicle which hit the auto lost its front bumper, the police responded to the accident, but didn’t file any accident report for the same. And while the cars are driving themselves, traffic laws require a driver to sit behind the wheel at all times, ready to take control if needed.