The day started with a celebration and ended with a bruised bumper for the nation's first self-driving shuttle. The autonomous shuttle debuted in downtown Las Vegas on Wednesday morning, but by early afternoon, a delivery truck "grazed" the front of the high-tech vehicle, city officials said. Metro Police determined the driver of the delivery truck was at fault, rendering this question unnecessary: How do you cite an unmanned vehicle? City officials seem confident that question won't arise. "Had the truck had the same sensing equipment that the shuttle has the accident would have been avoided," they wrote in a blog post.