"I see little issue with imaging a car if there's nobody in it"
If you were to spend some time at a border checkpoint sitting in a chainlink cage(literally) in the accompaniment of other travelers as your vehicles are batch scanned you may change your mind. More so if that checkpoint happens to be located 100+ miles north of the border.
If you were to spend some time at a border checkpoint sitting in a chainlink cage(literally) in the accompaniment of other travelers as your vehicles are batch scanned you may change your mind. More so if that checkpoint happens to be located 100+ miles north of the border.