There are two situations in which I make extremely sure I’m going precisely at or below the speed limit:
I see a cop
Some asshole is tailgating me
This is both spiteful AND practical, because you can’t control whether or not they give you a safe following distance for the speed you’re travelling, but you CAN reduce the speed you both have to travel, having the triple benefit of A) increasing the likelihood that they’ll have enough time to stop without rear-ending you. B) lowering the speed of any possible collision and thus the severity and C) Pissing the fucker the fuck off.
