Google's self-driving car project has raised a lot of questions around safety and its ability to avoid accidents and hitting pedestrians, but now one police officer in California has pulled over one of the autonomous vehicles for driving too slowly.

The incident happened on an eastbound lane on El Camino Real in Mountain View where Google is currently testing a fleet of autonomous vehicles. The officer noticed the car, which has a top speed of just 25 miles per hour (mph), traveling at 24mph in a 35mph zone. According to the Mountain View Police Department, "as the officer approached the slow moving car he realized it was a Google Autonomous Vehicle. 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."

The Mountain View Police Department says it meets regularly with Google to ensure the vehicles operate safely. Google is among a number of companies which has been granted a license to test cars on public roads and as well as testing them near its headquarters in Silicon Valley, it is also carrying out tests in Austin, Texas.

Google says that like the officer, the operators of these vehicles get flagged down by a lot of people who are interested in the vehicles, but so far it hasn't infringed any laws: "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," Google said in a blog post.

Google has begun publishing monthly reports related to its driverless car project which has been on-going for almost six years now and in that time, it has been involved in 16 "minor accidents," with the company claiming that not a single one was the fault of the Google car.