It's one of the first movies to explore modern American alienation from the point of view of a woman.
It draws on the Phantom Hitchhiker myth, but, like Lucille Fletcher/Orson Welles in the Suspense radio show's episode, "The Hitch Hiker," and also the Twilight Zone episode, based upon that earlier show's rendition, of the same title, it does so from the POV of the hitchhiker "who died after plunging off the old railway bridge that day" drag racing or whatever.
The point all three works make is that sometimes, people with their own cars who drive as fast as they can and never stop in the same place twice are so scattered and alienated and rootless that they could very well die twice, and only a specter from beyond -- a kind of Jungian archetypal dark magus (who even impersonates an actual medical professional attempting to counsel the disembodied psyche on its Jungian journey at one point in Carnival of Souls) -- can lead them from a kind of extended simultaneous denial stage and bargaining stage regarding their own death.
No time to die. Gotta move. Gotta drive. Gotta get to work. Either there's no family to leave (CoS), or the family thinks that the dead person is a prank calling to be cruel, because "MY SON DIED TWO WEEKS AGO ON THE BRIDGE OUT OF TOWN" (The radio protagonist was a man, while the TV and CoS ones were women, and, in fact, both were bottle blondes with fine features and wide doe eyes).
If I believed in literary theory or pat sociological film analysis anymore, I'd say that the gender switch between 1942's radio play -- during WWII, when men were uprooted from their jobs and sent to the first fully-industrialized and non-line-marching war in which the USA took part -- and 1960 (Twilight zone episode)/1962 (CoS), when women were expected to have undergone a full "Return to Normalcy" type re-domesticization and de-intellectualization, with concomitant job loss, was about the right to have a full psyche.
I DO think that Herk Harvey was the first filmmaker to address the psychic toll of the Feminine Mystique. It's not really surprising. Lawrence, Kansas (Centron's home) has had a history of progressive thought and activism (like the militant abolitionism that brought upon the town the Lawrence Massacre (or "Quantrill's Raid," if you respect officers that even those who "pacified" the Indians thought were taking things too far)). That and the somber reflection (the man who made that cheating short is a man who is thoughtful, if not depressive) Harvey constantly forced upon himself through his educational shorts on the ethical issues of kids' formative years would have unavoidably alienated Harvey, himself, from traditional (or, in fact, probably any but his own special) thought on society, its role in the life of the individual, and exactly why women have to be neater and cleaner and are responsible for the morals of their children, and all the other lessons that public schools' curricula used to dictate the content and views expressed in his shorts.
I like that he picks probably the only place in Utah where there's a picture of a woman showing that much skin, holding a colorful beach ball, and having, according to her smile and the billboard's text, "fun." I like that that is the place where death happens, where people who are moving too fast can come to dance into the joy and rest of going to salt water after the hectic dance is over. I like that the heroine clings to the disgusting lech who sullies everything fun in the world because she would rather keep her speed constant, but that she can't bring herself to actually "be a fast girl" to pay the price necessary to stay in the physical world.
And what separates her from Oil Grease Lube? Not her socioeconomic background. She's an orphan who has to work to make her way. No, it's her education. She has more mind than he does and she won't let it slide and just trash her education and marry the first single guy with a job that she finds once she's thoroughly creeped out the last three single guys in her own town by walking out of the water where she ought, by all rights, to have been partly crushed/coup-contrecouped and partly drowned to death, with no memory of what happened to the other two girls in the accident.
I'm probably going to edit this in a few hours (Think of this as not a wordburger, but as word-dough. it has to leaven and be kneaded in a while. And it isn't even half-baked. [BREAD JOKE GOES HERE]: I had a lot more idea than I thought I did and so it's kind of cramped in the current paragraph-pans). But I really do love this movie. If it starred a guy, it would be the Twilight Zone pilot episode, "Where Is Everybody?," and critics would have said pithy, emotional, knowing things about the alienation of modern man, what with the Russians and the isolation of both personal and outer space, and they'd probably even try to tie shell shock in. But it's a woman. So it's just a big mass of shopping (taking factory seconds and being out of the mainstream of fashion (and thus looked on as an outsider by other women) are important social actions in female society), purse-chivalry, and a girl who brought Oil Grease Lube upon herself by not taking the advice of the Greek chorus of Doughy Guys who haunt her from the minute she goes into the drink: The cop dragging the river; the organ factory workers; the priest; the service station attendant; the bizarrely boundary-less and infantilizing doctor (who is not board certified in psychiatry, much less trained in that area of study, but who sees an unattached woman reacting emotionally and literally manhandles her back to his office to spout Reader's Digest-level interpretations of her apparent psychotic break at her, just as the priest basically shouted moralistic sermon titles at her, etc. More later)