A bomb "near" a rail line turns out to be debris dumped in an empty lot to avoid paying a disposal fee, a "test of security" turns out to be investigative journalists with a camera in a water bottle, and of course the never-ending stream of drug mules are trotted out.

None of this is a threat to transportation, but that doesn't curtail the seige mentality. If it's not an American flag, it's probably a bomb.