Editing 1559

'''Explanation'''

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A self driving car is a car that requires no human interaction to navigate streets to a destination. Thus, when Black Hat places the rock that weighs "as much as a small adult" into the car's seat, he begins the process of fooling the car into thinking it has an occupant when it does not. His purpose in doing so appears to be to send the car to Anchorage, Alaska, which is presumably far from where Back Hat and Cueball are standing, thus taking the car far away from its owner with relatively little effort on the part of Black Hat. 

The title text references the fact that driving to Alaska from the continental or continuous 48 states requires two border crossings, once into Canada from the mainland, and once from Canada into Alaska.