According to Richard Matheson, he was inspired to write the original short story "Duel" after an encounter with a tailgating truck driver on November 22, 1963, the day that John F. Kennedy was assassinated.
Spielberg praised how the truck was handled in an exceptionally safe manner by 50 year old stunt driver Carey Loftin. Although it appears the truck is driving at a recklessly unsafe speed along the winding California roads, it is actually not going more than 30 mph. To get the sense of increased speed, Spielberg borrowed the specially-made camera car from the 1968 Steve McQueen thriller Bullitt (1968), which could lower the camera to only six inches off the ground. Spielberg also filmed the vehicles against a background of cliffs which, when combined with an upward angled perspective from the wheels, created an optical illusion of much faster speed.
When Carey Loftin, playing the truck driver, asked Steven Spielberg what his motivation was for tormenting the car's driver, Spielberg told him, "You're a dirty, rotten, no-good son of a bitch." Loftin replied, "Kid, you hired the right man."
Steven Spielberg said that the multiple license plates on the front bumper of the truck suggested that the truck driver is a serial killer which "ran down other drivers in other states."
Steven Spielberg was shown seven different semi-trucks to choose from; he chose a Peterbilt because the cab resembled a face.