It sounds like perennial teen misbehavior, but car surfing is a new concern for health authorities, who took a look at the thrill-seeking activity in a report published today.

Between 1990 and this year, epidemiologists turned up 99 news reports of car surfing, in which people ride on the roof, hood, trunk or elsewhere on the exterior of an automobile. Some 58 of those cases were fatal.

That count probably doesn't capture every car surf, says John Halpin, a medical epidemiologist at the U.S. Centers for Disease Control's Injury Center. "In absolute terms that is a low number. We've likely missed cases," Halpin says. "But even if it's low in numbers, because it has such devastating consequences even at low speeds, we thought it was such a serious public health issue."

Deaths occurred at speeds as low as five miles per hour (eight kilometers per hour) — when unexpected braking, swerving, or hitting a bump in the road threw the surfer — and at speeds as high as 80 miles per hour (129 kilometers per hour). Boys ages 15 to 19 accounted for the majority of fatalities, three quarters of which were in the Midwest and South.

The study in the Morbidity and Mortality Weekly Report is the first time the CDC has published data on car surfing, Halpin says, but the phenomenon doesn't seem any more or less popular now than in years past. "We can simply say it's been persistent over the last 18 years, with no evidence of increasing or decreasing popularity," he says. "We find that concerning because it's so dangerous, and yet it continues."

(Image by iStockphoto/TommL)