Crosses the Line Twice: The radio program at the beginning making fun of the idea of a male homemaker? Unfunny and dated. The caller casually pointing out that he wears a dress because it makes it easier to clean? Extremely funny.
Hilarious in Hindsight: Steven Spielberg directs a movie with a four letter long title, about an ordinary guy terrorized by a monstrous beast. He's said that these similarities are actually what got him interested in directing Jaws.
Moral Event Horizon: The truck is just tormenting Mann... until it tries to run him down in the phone booth and destroys the cages and property at the gas station, which also hurt an innocent old lady. At this point it is okay that the truck is destroyed at the end.
One-Scene Wonder: The oddity of some of the radio callers in the opening sequence, particularly the guy who "plays meat," make them rather more memorable than they by all rights should be.
Paranoia Fuel: You would be forgiven for nervously eyeing trucks, especially out on the highway, after watching this movie.
As the truck is running off the cliff, the drivers side door is clearly open (the driver had leapt from the cab when the truck reached a certain point, but the door failed to latch as he closed it, and obviously they couldn't do the shot over).
When Mann tries to call the police, Spielberg's reflection is visible in the phone booth.
Unintentional Period Piece: The freight trains shown in this movie bear Southern Pacific logos and markings on their locomotives. The Southern Pacific was folded into the Union Pacific Railroad in 1996. Though some locomotives still had Southern Pacific colors and markings, increasingly during the late 1990s and early 2000s newer Union Pacific logos and road numbers were patched onto them. By 2020, almost all such examples had either been fully repainted or sold off / retired.
Values Dissonance: The radio program making fun of the idea of a male homemaker. Not as strong as you might expect, since many people nowadays look down on homemakers in general, but the idea that a man was worthy of ridicule because he married a hard-working career woman seems far more out of place now than when the film was first made.
Examples from the TV game show
Padding: While not as bad as other shows that were on the air back then, Duel holds the dubious distinction of being one of the few shows to end an episode after the players had locked in their answers, thus forcing everyone to wait until the next show to see if they were right.
