Question: Why did the truck driver want to kill David Mann?
Answer: According to director Steven Spielberg, the trucker was a serial killer, and each of the license plates were trophies from previous victims.
Answer: David pulled ahead of the truck not once but twice. He got to the gas station first, and got served before the trucker. For any normal person this would not be cause to try to murder someone, however the truck driver is an unhinged psychopath who doesn't need much reason to go into an obsessive rage. Add to that the fact that David is driving a much smaller car, and the fact that they're out in the middle of nowhere with nary a cop around, and the truck driver probably saw David as easy prey.
Answer: "It was very common to see semi trucks with a half dozen or so license plates on them, each from a different state." And that's how the psycho trucker got away with it. He could have those 'trophy' plates on the front of the truck in plain sight, and to anyone who saw it, the truck would look like just another big rig with multiple license plates. Nothing out of the ordinary or suspicious about it.
Question: Where was David Mann actually going? And where from? As in, which states? He seemed to be travelling for hours even before he met the truck and seemed to have a long way to go yet.
Chosen answer: The movie opens with him in downtown Los Angeles, California, so he's probably from there or somewhere in Southern California. He's heading to Bakersfield, California, which is north, about 2 hours away. In the short story, he's heading to a client in San Francisco. However, in the film he gets off the main freeway running from LA to Bakersfield (IH-5) and takes Highway 14 towards Canyon Country.
Question: When the character was at the cafe and the truck was there, but he didn't know who the driver was, why didn't he just go and wait by the truck, smash the windshield, fill the gas tank with sugar or water, slash the tyres?
Answer: At that point in the film, the protagonist David Mann is ready to confront the truck driver. When he sees the old Peterbilt truck outside, David mistakenly assumes the truck driver has already entered the diner, so he confronts a likely suspect that he sees at the counter (but he has misidentified the man). The misidentified man takes offense and punches David out. By the time he recovers his senses, David sees the old Peterbilt truck leaving the parking lot. Which means the actual homicidal truck driver never entered the diner in the first place and was waiting outside the whole time. If David had first gone outside to the Peterbilt, there was a good chance the waiting homicidal truck driver would have killed him right there, and the story would have abruptly ended. So, David's misidentification of the truck driver allowed the film to move ahead into its next act.
Yes, I get why the filmmakers did that, but I still think it is a plot hole. If the Dennis Weaver character was afraid of getting killed by the truck driver, I doubt he would have confronted him in the cafe.
Question: Why didn't David simply turn around and go back home? The truck never turned around to get him, it just waited further ahead up the road. David even stated he'd never make his meeting now due to delays. Huge plot hole.
Answer: As the title indicated this became a "duel." Once challenged, David got pulled into a fight mentality with the crazed truck driver to where his "road rage" pushed aside all logic and sense of safety. David became obsessed with defeating the "Goliath" opponent. Also, if he turned around and went home, that would have ended the movie.
Answer: Not only that but, the truck driver was a psycho who wanted to kill David, so he would have likely turned around and kept following him.
Maybe-but if David had not taken his roughly one hour nap and turned around right then he would have had a huge head start on the truck, and it is doubtful the truck would have caught up with him. Still, a great movie.
Question: At the end, in the wrecks, we see a little tabletop air fan still running. Where was it before? We never saw it in the car. (01:27:10)
Answer: It was in the truck, not the car.
Question: I know it's never answered in the film but is it explained in the book just why the truck driver takes such a dislike to David Mann - he behaves this way after just a couple of overtakes?
Chosen answer: That is never answered for the film, and not knowing adds to the mystery and intrigue. No mentally stable person would target someone just because they overtook their vehicle on the road. It appears that Mann happened to cross paths with a psychopath. Steven Spielberg has commented that the multiple out-of-state license plates attached to the truck's front bumper may be "trophies" that indicate that the trucker is a serial killer who has run down other drivers. This could be a deadly game to the truck driver.
I just wonder why the driver's door on the big rig was open while it took a dive over the mountain.
Perhaps a hint that the truck driver escaped. You notice that the truck doesn't explode on impact, although the studio insisted it must; Spielberg fought the studio over the inclusion of a cliched fiery finale, as he wanted the crash to convey an ambiguous ending, suggesting that the driver might not have died. Spielberg even explained that the red liquid seen in the truck cab was not blood, but was some sort of automotive fluid. This all lent to the mystery of what actually happened to the driver, whose body we never see.
The stuntman driving the truck had to jump out of the truck right before it went over the edge, and due to equipment issues barely made it out, without having time to shut the door.
Question: I'm pretty sure that some of the "Duel" tanker footage was used in a different film, but I can't find any info on it. What other movies used it?
Answer: Some "Duel" footage was used for the TV series "The Incredible Hulk" in an episode titled "Never Give a Trucker an Even Break." Both the TV movie and the series were produced by Universal Studios.
Answer: It's never explained why but, judging from the numerous license plates from other vehicles attached to his truck, the truck driver is a serial killer and was just targeting people at random and decided to make David his next target.
Trucks used to have to be registered in multiple states if they were going to operate in them. It was very common to see semi trucks with a half dozen or so license plates on them, each from a different state.