https://www.vox.com/technology/2015/10/30/9640230/self-drivi... "Most of the accidents happened because another vehicle rear-ended the self-driving car. Self-driving cars have not been involved in any head-on collisions, and crashes involving self-driving cars were less likely to cause injuries than crashes involving conventional vehicles — just two out of 11 crashes led to injuries, compared with 28 percent of conventional vehicles."

It's hard to say "you've crashed" when you've been rear-ended.