I've gotten in the habbit of calling them 'mushroom heads' because when you're stuck behind them, all you can see is a silhouette of a poof of hair, which vaguely resembles a mushroom.

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>>Here in Phoenix, we have a lot of cars that from behind, you can only see >knuckles on the steering wheels. Need I say more? ;)

>Beware the Blue-Haired Highway Sloth...