A Google self-driving car has been pulled over by Californian police for going 18 km/h under the speed limit.
The BBC says the California Department of Motor Vehicles filed a report describing a Google automated car as "over-cautious".
Google say they have capped the speed of these self-driving cars to 40 km/h for safety reasons.
The Mountain View Police Department say it meets regularly with Google "to ensure that their vehicles operate safely in our community".
The police department's website says an officer "noticed traffic backing up behind a slow-moving car in the eastbound lane".
"The officer stopped the car and made contact with the operators to learn more about how it was choosing speeds along certain roadways and to educate the operators about impeding traffic," it added.
In their own blog post, Google said "We want [the cars] to feel friendly and approachable, rather than zooming scarily through neighbourhood streets."
They added that "in 1.2 million miles [1.9 million kilometres] of independent driving tests, we're proud to say we've never been ticketed".
Google says the autonomous cars are programmed to follow the rules of the road "to the letter". That can cause problems when the vehicles share the road with human drivers who do not follow the rules in the same way.
The BBC reports the only recorded accident involving a self-driving Google car occurred when it braked suddenly at a pedestrian crossing and another vehicle drove into the back of it.
There are now 48 self-driving cars operating in California and Texas.