While 1971 film Duel is a classic film and I love the film .A car can out run a semi truck which will then quickly catch up as semi truck depend on the make or model has between 10 to 18 gears.Also Manuel transmission go faster then automatic.The film used a tag axle 1955 Peterbilt 281, making it looking like a Peterbilt 351, with two rear axles. The truck had a CAT 1674 turbocharged engine with a 13-speed transmission, making it capable of hauling loads over 30 tons and top speeds reaching 75–80 mph.The truck driver knew the roads and is a serial killer while Plymouth 1971 has a top speed of 120 mph the Plymouth Valiant has a 3 speed manual transmission the semi has 13 speed transmission.You are rooting for the car to escape the semi truck.There so many curves in the film that it would be too dangerous to drive at high rate the truck driver is toying with Denis Weaver character throughout the film.