Automobile accidents are the leading cause of death among US teenagers, accounting for 36% of all deaths for 15- to 19-year-olds, according to Dr. Li-Hui Chen of the Center for Injury Research and Policy at Johns Hopkins University in Baltimore, Maryland, and colleagues.

      In a new study, the researchers found that carrying passengers increased car accident-related death rates for teenagers, but not for adults. For example, about 2 deaths occur in every 10 million trips driven by 16 year olds. When there is one passenger in the car, the death rate rises to 2.76 per 10 million. Add two passengers, the death rate rises to 3.69 and with three, is 5.61 per 10 million.

      The findings were similar for 17-year-old drivers (2.18, 3.79, and 4.52, respectively), according to the report in the March 22/29 issue of The Journal of the American Medical Association.

      In contrast, death rates fell with each additional passenger in cars piloted by older drivers. Among those aged 30 to 59, about 0.68 deaths occur per every 10 million trips, and that number drops with added passengers, the authors report.

      When it came to teen drivers, the age of the passenger also appeared to contribute to fatality risk. Death rates were higher when teen drivers had teenage passengers or passengers between 20 and 29 years, but carrying passengers aged 30 or older did not increase driver death rates.

      The time of day also was a factor. Fatal crashes with passengers were more common after 10 p.m. and the riskiest time was between midnight and 6 a.m. Teen drivers who were carrying male passengers were also more likely to be in a fatal crash than those carrying female passengers.

      The findings suggest that graduated driver licensing (GDL) can help prevent fatal crashes, the authors conclude. In this system, teens earn licenses in a step-by-step fashion with restrictions on nighttime driving or having passengers.

      "Even without specific information on alcohol use, (this report) provides sufficient evidence for policy makers to improve the traffic safety of teenaged drivers, their passengers, and other motorists," according to an editorial by Dr. Robert Foss from the University of North Carolina Highway Safety Research Center in Chapel Hill.

      "This can be achieved," Foss continues, "by prohibiting teenagers in the second stage of GDL systems from driving after 10 p.m. and from driving with teenaged passengers.... In states without GDL systems, or those with systems that do not prohibit driving after 10 p.m. and driving with teenaged passengers, parents of 16- and 17-year-old drivers would be well advised to impose these restrictions themselves."

     SOURCE: The Journal of the American Medical Association 2000;283:1578-1582, 1617-1618.