Police pulled over one of Google's self-driving cars on Thursday for driving slowly in Mountain View, California, where the company has its headquarters -- but there was no traffic infraction.

The cartoonishly curvacious vehicle was driving 24 miles per hour in a 35 mph zone, police said, and was pulled over after a traffic officer noticed traffic backing up behind it.

"As the officer approached the slow moving car he realized it was a Google autonomous vehicle," Mountain View Police Department wrote in a blog post. "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."

The auto and computing industries believe self-driving cars are the future. But developing the technology is only one step along the road. Drivers, legislators and engineers also will have to reckon with issues like car-crash ethical choices, insurance coverage and, as here, law enforcement. For traffic violations, Google has said the company itself should be responsible for tickets.