As such, having a firm command of symbolism is necessary for directors, screenwriters, editors, production designers, and many more positions on a film set.
When the characters are attracted to cars and car crashes, the audience can interpret this as commentary on modern society's increasing obsession with violence.
Although there's comparatively little sex and violence in the film, it's one of the most sexual and violent films ever made because of the explicit assumption set out in every frame that sex and violence are inherent in the experience of driving a car.
Typically, symbolism is intricately connected to ideas already present in a movie, allowing both the symbols and the themes to become more evident to an audience.
If the symbol is integral to the narrative, it typically is more easily identifiable, since the audience may need to understand it to understand the film.