Google’s fleet of self-driving cars have just clocked up over 2 million miles of testing on public roads.

The technology company has been developing autonomous vehicles since 2009 and logs around 25,000 miles of public testing every week. By comparison, Automotive News reports that Tesla has logged in excess of 100 million miles of semi-autonomous driving in the past 12 months since the introduction of Autopilot.

However, the head of Google’s self-driving division, Dmitri Dolgov was keen to point out in an interview that Google’s vehicles test on busy city streets whereas most Tesla owners use Autopilot on highways.

Google’s system has become so advanced that it is able to automatically calculate the probability of an object, such as a bicycle, will make an unpredictable movement and then reacts in the most appropriate way.

According to Dolgov, it is these social interactions which are the most challenging elements of autonomous driving systems to get right.

“You get to 90 percent autonomy in 10 percent of the time and then spend 90 percent of your time on the last 10 percent.”

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