@knievel said:
a whole feature film of tension made out of, what is essentially, a cast of just two.
Not strictly true, as we never seen the truck driver, so kind of a solo performance !
They spent weeks scouring southern California looking for just the right truck. Speilberg wanted a truck that not only looked intimidating and ominous but had a personality all it's own, or his own. Aside from a beefy arm protruding out of the cab every once in a while you never see the driver. In other words the truck was a character. In a way, Kneivel is correct the truck was casted as a character.