While filming the shot where the truck drives off the cliff, a piece of machinery designed to keep the truck traveling in a straight line without a driver failed. Instead of calling a halt, the driver, who had an important engagement the next day and didn't want to miss it, stayed in the driving seat and only jumped out at the very last second before the truck went over.
During the chase, a parked sedan resembling a squad car is seen, briefly raising Dennis Weaver's hopes, but it turns out to be a service car for a pest exterminator named Grebleips... "Spielberg" in reverse.
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."
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.
Steven Spielberg can be seen reflected in the telephone booth during the scene where David Mann is calling the police. During his appearance on "Inside the Actors Studio" (1999) (#5.9)_qv Spielberg admitted that this was not an intentional cameo, but instead was a mistake. He went on to state that several similar mistakes were revealed when the movie received a theatrical release in Europe, with 18 different occurrences where Spielberg could be seen because of the change in aspect ratio for theatrical release.
Some of the scenes were later used as stock footage in The Incredible Hulk: Never Give a Trucker an Even Break (1978). Obvious scenes used were the red Valiant slamming into the fence, the use of the same phantom truck in new TV footage, and the use of a similar Valiant in new TV footage. Unhappy by the discovery that footage from the movie was recycled, and unable to sue because the studio owned both the film and Hulk series, Steven Spielberg insisted that all his future contracts have a clause designed to protect his films from being used as stock footage.
When the truck enters the gate during the climax of the film, it actually hits the camera: in the last frame or so, you can see distortion and small pieces of the camera at the bottom right of the screen. Also, the shot is a flipped negative.
There is an elderly couple who drive by in a red car. The woman yells at the man to keep driving. A similar couple in a red car acts out the same ordeal in Back to the Future (1985), of which Steven Spielberg was the Executive Producer.
At the time of filming, the Federal Highways had just introduced the all yellow center line road marking guidelines. Parts of the road that Weaver drives along had just been painted in the new scheme. It is common for films made in the USA during the 'changeover' period (up to around 1975) to show roads with the original white lines and new yellow stripes.
The license plates on the front of the truck are for each state that the truck drives in, kind of a way of paying tax. Most of the plate have an MC on them which means "Motor Carrier" and the New Mexico plate is a HUP "Highway Use Permit"
The Valiant used in the film was actually 3 different cars. For the television release there was a 1970 with a 318 V8 (as witnessed by the 1970-only "V-EIGHT" spear-type emblems on the forward portion of the front fenders), and a 1971 with a 225 slant six. When the added scenes were filmed, a 1972 Valiant with a 225 Slant Six was used. This makes sense, due to the fact that the television showing was in November 1971, 3 months into the 1972 model year. All three Valiants had 1971-only, Plymouth-only wheel covers. The license plates on Weaver's Valiant were actually incorrect: 149 PCE, in the 1970 & later blue/yellow colors, would technically have to be 1976-issue ("P" = 1976). However, this isn't necessarily conversely an incorrect item. Many vehicles used variations of this license number (the van from the "A-TEAM" used number "1PCE149").
Universal provided action stock footage, filmed by the 1st & 2nd units, from the Spielberg production, to an episode of "The Incredible Hulk", starring Bill Bixby. Obvious scenes used were the red Valiant slamming into the fence, the use of the same phantom truck in new tv footage, and the use of a similar Valiant in new tv footage.