Well, I know there have been more than a few of those living like 50, 60 miles outside of major urban areas who already have identified bridges to drop, trees to block roads with, overturned vehicles, or use a back hoe to dig ditches big enough to swallow a 4×4 truck.
Not sure I agree with it, but if you think a few hundred thousand people might be heading your way and expect you to feed them, well . . .