What happens when a police officer pulls over a robotic car?

A Google autonomous car was pulled over Thursday while driving near the company's headquarters in Mountain View, Calif.

An officer from the Mountain View Police Department (MVPD) observed traffic slowing down on a public road and pulled the car over for driving 11 m.p.h. under the speed limit. The Google self-driving vehicle, which is only allowed on public roads with speed limits of 35 m.p.h. or slower, was operating on a legal road, but was obstructing traffic in violation of section 22400 of the California Vehicle Code.

The officer did not have a driver to ticket, but spoke with the car's operator, issuing a warning about maintaining safe and reasonable speeds. In their statement, the MVPD wrote, “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.”

Google was quick to post on its Google+ page, defending the cop encounter. “Driving too slowly? Bet humans don’t get pulled over for that too often,” a project member wrote. Google also affirmed that the car’s speed was capped at 25 m.p.h. for safety reasons, which means the car wouldn’t have been able to operate at the posted 35 m.p.h. speed limit anyway.

“Like this officer, people sometimes flag us down when they want to know more about our project," the post continued. "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!”

This instance offers an interesting challenge on the horizon: How will autonomous cars change traffic enforcement?

In a blog post on Policemag.com, Lt. Dan Fink of the San Rafael, Calif., Police Department wrote, “an additional unintended consequence of smart cars may be significantly fewer law enforcement personnel assigned to traffic enforcement.”

He noted that autonomous cars could reduce fatalities, particularly those connected to drunk driving, but also pointed out that changes to the law might have to occur.

Autonomous cars will also affect law enforcement budgets. With fewer accidents, and fewer traffic violations, police departments will not be able to collect as much revenue from traffic tickets.

“Self-driving cars are programmed to stop at red lights and stop signs," says an article in Slate addressing several scenarios associated with autonomous vehicles. "Surely they should also be programmed to stop when a police officer flags them down. It is, after all, the law.”

But it may not be that simple. Where should the line be drawn? “If a police officer can command a self-driving car to pull over for his own safety and that of others on the road, can he do the same if he suspects the passenger of a crime?” questions Slate. “And what if the passenger doesn’t want the car to stop—can she override the command, or does the police officer have ultimate control?”