The study, to be published in the Oct. 3 issue of
The Journal of theAmerican Medical Association
, examined the initial effects of graduateddriver licensing, or GDL, on crashes involving 16-year-old North Carolinadrivers.
Dr. Robert D. Foss and colleagues at the center compared crashrates from 1996-97 - before 16-year-olds were licensed under the GDL system- and crash rates from 1999, when the new system was in place. To controlfor other factors possibly influencing crashes, the authors compared changesamong 16-year-old drivers with those ages 25 to 54. They also studiedcrashes per licensed driver to rule out the possibility that a decrease inthe number of licensed drivers might explain the drop in crashes.
North Carolina instituted the GDL system on Dec. 1, 1997, requiring youngbeginning drivers to pass through two restricted driving periods before theyreceive their unrestricted licenses. In level 1, beginning drivers who areat least 15 years of age (and younger than age 18) may drive only with thesupervision of a designated adult. At the end of level 1, which lasts atleast 12 months, drivers with no traffic violations in the last six monthsand who have passed a road test may move to level 2. At this stage,unsupervised driving is permitted between 5 a.m. and 9 p.m. Driving after 9p.m. may be done only with the adult supervisor in the vehicle. After atleast six continuous months with no traffic violations at level 2, driversgraduate to a full, unrestricted license (level 3).
Foss, lead author of the study, said that the results, though remarkable,were not surprising to him and fellow investigators Dr. John R. Feaganes andEric A. Rodgman.
"Because GDL is based on a firm understanding of human behavior developedthrough decades of social and behavioral science research, it was highlylikely to have the effect it was designed to produce," Foss said. "These study findings strongly affirm that GDL istremendously successful."
Among the study's findings comparing 1996 (pre-GDL) crashes with 1999(post-GDL), as reported in the JAMA article, are the following:
"Crash rates declined sharply for all levels of severity among16-year-old drivers after the GDL program was implemented," the authorswrote.
Motor vehicle crashes are the most common cause of death among teenagers inthe United States, according to the National Center for Injury Preventionand Control. The crash risk is highest among the youngest drivers.
Inexperience and impulse actions contribute to the greater crash propensityamong beginning drivers. Since 1997, 34 states have enacted GDL systemsdesigned to reduce crash rates among novice drivers.
Related UNC Highway Safety Research Center findings were that fataland serious injury crashes were between 18 percent and 21 percent morelikely in the more rural counties than in the most urban North Carolinacounties during 1999, Foss said. The new study found that crashes among16-year-old drivers declined similarly regardless of degree of countyurbanization - good news for those rural counties where crash risks arehigher.
Preliminary findings from another study being conducted at the UNCHighway Safety Research center indicate that parents and teens alike endorseGDL. In telephone interviews with 600 families, more than 95 percent ofNorth Carolina parents either "highly approved" or "somewhat approved" ofGDL, and 80 percent of the state's teens gave the same assessment. In anissue of interest to states still considering a GDL program, the study foundthat parents and teens from the most rural areas support GDL just asstrongly as those from urban and suburban locations.
Study authors said that in consideration of the clear benefits ofGDL demonstrated in North Carolina and elsewhere, doctors in states withoutGDL systems, or where there is a relatively weak GDL program, shouldconsider advising both their teen patients and parents of teens to followthe principles of a model GDL program.
"This should include at least six months during which the teendrives extensively with a responsible adult supervisor, followed byprohibitions on unsupervised nighttime driving and transporting ofpassengers, until the teen has accumulated at least six months of additionaldriving experience without an adult supervisor," the report stated.
The UNC study was supported in part by the National Highway TrafficSafety Administration and the North Carolina Governor's Highway SafetyProgram. Some preliminary study results were announced in mid-2000.
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