Second, when I think of States highways I think of BPs and Shells/Taco Bells and Burger Kings competing for your money at every exit. There are no numbered exits and usually one local "petrol" station, so stop when you're around a quarter tank. In the U.S.A., unless you're driving through rural landscape or Kansas, there's usually developments, plazas, or residences within eyesight of the highway. In Australia, when you leave the towns of Ayr, Sarina, and Proserpine, you are on a lonely highway with nothing unnatural to break up the view.
Last, most Americans are familiar with the cautionary signs in construction zones in cute, childish handwriting stating "Slow down, my daddy works here" or "Leave racin' to the horses" (in Kentucky). Australia cuts right to the point:
NO SEATBELT, NO CHANCE
SLOW DOWN STUPID
and my favorite....
TIRED DRIVERS DIE