Graduated Driver Licensing
Evaluation of graduated driver licensing programs and deaths among young drivers
Scott Masten, Ph.D.
Do graduated driver’s licensing programs save lives? This was the topic addressed by Epidemiology graduate student Scott V. Masten in his dissertation. His research examined graduated driver licensing programs for young novice drivers in the U.S. that included restrictions on nighttime driving and allowed passengers in the car with the teen drivers.
Motor vehicle crashes are the leading cause of death in the United States for teenagers. From 2000-2008, more than 23,000 drivers and 14,000 passengers aged 16 to 19 years were killed. Graduated driver licensing (GDL) systems have now been adopted in all 50 states and the District of Columbia to reduce crashes among teenaged drivers. Graduated driver licensing is structured to ensure that young novices gain extensive experience driving in low-risk conditions before they ‘graduate’ in steps to driving in riskier conditions.
To answer his research question, the doctoral candidate conducted a GEE Poisson regression analysis of data of quarterly 1986-2007 incidence of fatal crashes involving drivers 16 to 19 years of age for all 50 states and the District of Columbia. State-quarters with stronger GDL programs (restrictions on both nighttime driving and allowed passengers) or weaker GDL programs (restrictions on either nighttime driving or allowed passengers) were compared to state-quarters without GDL. A limitation of the study was that it only included fatal crashes.Fatal crash incidence among teen drivers increased with age, from 16 to 17-year-old drivers before reaching a plateau at the ages of 18 and 19. After adjusting for possible confounders, stronger GDL programs (relative to no GDL program) were found to lower the incidence of fatal crashes among 16-year-old drivers by 26 percent. However, strong GDL programs were associated with a 12 percent increase in fatal crashes among 18-year-olds, for whom the program’s restrictions no longer apply.
The net associations found in this study represent several possible crash-reducing influences of GDL, including less driving among younger teens; reduced exposure to high-risk conditions, resulting from more driving while supervised by an adult and less driving late at night or with multiple young passengers; and safer driving, resulting from improved learning. Mandatory periods of supervised driving clearly reduce risk while novices learn how to handle a vehicle, gain insights into the behaviors of other drivers, and develop understanding of the physical driving environment. Supervised driving, however, is co-driving, and some important lessons of experience, such as the need for self-regulation and what it means to be fully responsible for a vehicle, cannot be learned until teens begin driving alone.
See a video about this study.
Other collaborators at UNC:
Masten SV, Foss RD, Marshall SW. Graduated Driver Licensing and Fatal Crashes Involving 16- to 19-Year-Old Drivers. JAMA. 2011;306(10):1098-1103.
Related website: Teen Drivers