It's not speeding tickets that Google's self-driving cars have to worry about.

The Mountain View police department pulled over one of the company's automated vehicles for moving too slowly, according to Zandr Milewski, who posted a picture of the incident on Facebook:

"We talked to the driver, apparently MVPD doesn't get NEVs [Neighborhood Electric Vehicles] and pulled them over to ask why they were all going so slow," Milewski writes in the comments of the post, which we spotted on Fusion.

Google confirmed the report with its own post on Google+ as did the Mountain View police department on its blog.

"Driving too slowly? Bet humans don’t get pulled over for that too often," Google quipped.

MVPD writes that one of its officers noticed traffic backing up behind a slow-moving car that was going 24 mph in a 35 mph zone.

"As the officer approached the slow moving car he realized it was a Google Autonomous Vehicle," the department says. "The officer stopped the car and made contact with the operators to learn more about how the car was choosing speeds along certain roadways and to educate the operators about impeding traffic per 22400(a) of the California Vehicle Code."

Google's prototype cars can only drive 25 mph for safety reasons and so that they feel "friendly and approachable" while driving on public roads. They also have manual controls so that the human inside the car can take over and drive if they need to — in response to a cop, for example.

Ultimately, the car wasn't breaking any laws.

"Like this officer, people sometimes flag us down when they want to know more about our project," Google continues. "After 1.2 million miles of autonomous driving (that's the human equivalent of 90 years of driving experience), we're proud to say we've never been ticketed!"

The cars are currently cruising around public roads in Austin, Texas, and in the city around Google headquarters.

As for Milewski, it wasn't the first time he'd spotted one of Google's autonomous vehicles, and it probably won't be the last, as he told Business Insider via Facebook Messenger:

"It's Mountain View, these things are everywhere."