The film is loosely based on an experience from the Director's past. In the early eighties, while he and a few friends were driving home, they were chased by a car, for several hours, through backwoods roads.
Spoiler: In several scenes, a black '57 Series 62 Sedan is substituted for the Series 75 limousine. Since the roof and rear window is completely different on the two cars, a fake roof extension had to be created for the Series 62 model. It was this car and not the limousine that drove off the cliff into the frozen lake at the end of the film.
On at least one occasion, the Saab is shown being rammed from behind and the lights getting smashed. A little later they are all intact and shining again. Similarly, the Cadillac has duff lights which swap sides or rectify themselves without provocation
The movie alternates between two black 1957 Cadillacs, a four-door Eldorado and a Fleetwood 75 limousine. "Eldorado" lettering is visible on the trunk lid and the curved rear door window frame differs from a square rear limo door. A similar replacement car may have been obtained for additional filming under different weather conditions following the destruction of the original car.