When you're driving on the highway and some driver gets up your ass, then passes you. Because even though you're speeding already, you're just not fast enough for him. So this is you're prime opportunity to have a Highway Grudge where you just NEED to pass him. This tends to go on back and forth until someone takes an off-ramp.
Guy 1: Get out of my ass!
Guy 2: Haha I'm gonna pass this guy cause he is SOOO slow...
Guy 1: What an asshole. I need to pass him now to show him what's what!
Guy 2: Jesus this guy has a Highway Grudge!