Which weird stories are just legends and which ones are real? That's a difficult question to answer, especially in the case of "The Killer in the Backseat," one of the most popular American urban legends.

Classic versions of the story - which have circulated for some 30 years - describe a woman driving home alone at night who is followed closely by a stranger driving a truck.The trucker pursues her right off the highway and to her home, occasionally flashing his high beams. As soon as she's in her own driveway, the terrified woman leans on the horn to summon her husband.

At that point, the pursuing driver jumps out of his truck and runs up to her car. He jerks the rear door open, and pulls out a man who was lurking in the backseat with a knife.

The trucker then explains to the woman and her husband that he had been blinking his lights whenever the would-be assailant started to raise his knife to attack her.

In some versions, the woman is rescued by a service station attendant who, while he's filling the tank, notices a man hiding in the backseat. He calmly asks the woman driver to come inside the station, and as soon as she does, he locks the door and calls the police.

"The Killer in the Backseat" is told with countless variations, such as why the woman is out driving alone at night - she's going to another town for a wedding, a baby shower, a Tupperware party or the like.

The story is sometimes enhanced with realistic details about local highway numbers, freeway exits and specific gas stations. But the person supposedly involved in the incident is always merely a FOAF - a friend of a friend.

A New Jersey college student who wrote to me recently heard another version from her mother. This time, when the police came, drew their guns and ordered the man to get out, he turned out to be the woman's boyfriend. He had a bouquet of roses and an engagement ring and was waiting to surprise her, but not quite the way things turned out.

Once again, this is only a FOAF story that likely never happened. But there have been, of course, real crimes involving men lurking in women's cars.

Last July, for example, a news story datelined Newark, N.J., told of a man hiding in the back of a woman's Jeep who slashed his victim's cheek with a knife.

In March 1990 a clipping sent by a reader in Bloomington, Ind., told of a man hiding in a woman's van who jumped out when he was spotted at a fast-food drive-through.

Many other readers have sent me similar recent news item, but the oldest one I've received was printed in 1935 in the Palo Alto (Calif.) Times. The headline summarized the crime: "Man Lurking in Back Seat Slugs Girls. Hurls Victims to Ground, Steals Car and Purses."

In this instance the man got only $23. He had used a flashlight as a weapon.

While actual incidents of this kind may have given rise to "The Killer in the Backseat" legend, it's important to note the differences as well: None of these news stories say anything about the mysterious behavior of another driver, nor do they describe the rescue of the woman.

The suspenseful beginning of the story and the happy ending are what separate this legend from real life.

Yet, both the news stories and the legends convey one consistent warning: Check the back seat of your car!- "Curses! Broiled Again," Jan Harold Brunvand's fourth collection of urban legends, is now available in paperback from Norton. Send your questions and urban legends to him in care of the Deseret News.