The rising problem of mass car attacks in the US

Seem like more and more in the US, people are intentionally, or unintentionally hitting large amounts of pedestrians. The most recent are of course the Las Vegas strip incident and the affluenza case.

Other recent mass pedestrian attacks:

http://ift.tt/1LujwvZ

http://ift.tt/1RBGaaM

http://ift.tt/1RBGczr

http://ift.tt/1RBGcPG

Serious question, does anyone keep statistics on this sort of thing?