Three people in a Google self-driving car were hurt when their Lexux SUV was rear-ended near the company's Mountain View, California headquarters. 

The injuries were only minor whiplash, and the self-driving car was not at fault. 

The company says in six years of testing the self-driving vehicles, they have only been struck 14 times and have never caused an accident. 

This is the first accident involving injuries.

AP reports

In a blog posted Thursday, the head of Google's self-driving car program, Chris Urmson, wrote that his SUVs "are being hit surprisingly often" by distracted drivers, perhaps people looking at their phones.

"The clear theme is human error and inattention," Urmson wrote. "We'll take all this as a signal that we're starting to compare favorably with human drivers."

In a telephone interview, Urmson said his team was exploring whether its cars could do something to alert distracted drivers before a collision. Honking would be one possibility, but Urmson said he worried that could start to annoy residents of Mountain View.

The collision happened when the SUV was struck from behind while in slow-moving traffic at a green light.

The car was operating itself at the time, with one Google employee in the driver's seat and two others riding along.

The driverless cars operate with sensors and cameras.