I read in this Bloomberg article
Google cars have been in 17 minor crashes in 2 million miles (3.2 million kilometers) of testing.
Ten days later, a Mountain View motorcycle cop noticed traffic stacking up behind a Google car going 24 miles an hour in a busy 35 mph zone. He zoomed over and became the first officer to stop a robot car.
I'm surprised that no other self-driving car got pulled over before, given that Google cars drove 3.2 million kilometers (and there are other car manufacturers).