Duel is the first full length movie Steven Spielberg did a very long time ago, and it proved his genius by making something out of nothing, mainly a car, a truck, and the open road.
It's a low budget flick, with little happening, yet the suspense is complete. The first time you'll watch it, if you don't mind the early 70s, you'll be surprised.
The main character's reactions and inner monologs have a few flaws, but the rest is excellent. The soundtrack, which consist of little music is very low key and it fits the movie just right who is the same overall. The local is a little used road in a semi-arid back country and perfect for the mood.
It's a movie to discover, but don't expect any bells or whistles.