According to a study in the September 14 issue of JAMA, stricter U.S. driving licensing programs for 16 to 19 year old drivers were linked to fewer fatal crashes among 16-year old drivers but to a higher incidence among 18 year olds. The program included restrictions on nighttime driving and permitted carrying passengers.
Background information in the article states that “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.”
At present, the U.S. GDL programs apply only to those beginning drivers who are less than 18 years old. The authors comment:
“The question remains whether the benefits of GDL among drivers to whom provisions directly apply (16- and 17-year-olds) continue, are reduced, or may even be reversed, among older teenagers for whom the effects are only secondary. Previous attempts to quantify the result of GDL for all teenaged drivers across multiple states have experienced methodological difficulties that rendered conclusions unclear.”
In order to estimate the link of how many 16 to 19 year old GDL drivers were involved in fatal crashes, Scott V. Masten, Ph.D., of the California Department of Motor Vehicles in Sacramento, California and his colleagues conducted a study using data analysis of quarterly 1986-2007 incidences of fatal crashes involving 16 to 19 year old drivers for all 50 states and the District of Columbia.
They compared state-quarters with stricter GDL programs, i.e. restrictions on both nighttime driving and allowing passengers with weaker GDL programs, i.e. restrictions on either nighttime driving or allowing passengers with state-quarters without GDL.
The authors discovered over the study period that fatal crash incidence among teen drivers increased with age from 16 to 17-year-old drivers before reaching a high-level at the ages of 18 and 19. After adjusting for various factors, they found that in comparison with no GDL program, stricter GDL programs were statistically linked to a lower fatal crash incidence but only in 16-year old drivers.
The authors state:
“For 18-year-old drivers, the rate of fatal crashes was statistically higher for stricter GDL programs than for programs having none of the key GDL elements. Rate ratios for 17-year-old drivers, 19-year-old drivers, and 16- to 19-year-old drivers combined were not statistically different from the null.”
They also discovered that stricter GDL programs seemed to be linked to a larger reduction in fatal crashes among 16-year-old drivers than weaker GDL programs but with a similar increase in fatal crashes involving 18-year-old drivers. They comment: “This suggests that modifying weaker existing state GDL programs to include nighttime as well as passenger restrictions may result in additional crash savings among 16-year-olds as well as a larger net savings among teen drivers overall.”
According to the researchers estimations, the weaker and stricter GDL programs combined have led to 1,348 fewer fatal crashes involving 16-year-old drivers and 1,086 more fatal crashes involving 18-year-old drivers since enactment of the first program in 1996.
They say: “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,” adding that the reasons are unknown as to why GDL programs appear to be linked to higher incidence of fatal crashes for 18-year-old drivers.
They continue: “The amount learned during the GDL process may not be comparable to what was learned previously, when young drivers learned through experience alone. 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. Under GDL this now occurs at least 6 months later, reducing the time that young drivers have to learn from driving on their own before they turn 18.”
In a concluding statement the authors say:
“Research is needed to determine what accounts for the increase among 18-year-old drivers and whether this increase occurs among nonfatal crashes as well. This may suggest whether, and how, changes to licensing policy might reduce this association.”
Editorial: Strengthening Driver Licensing Systems for Teenaged Drivers
Anne T. McCartt, Ph.D., and Eric R. Teoh, M.S., of the Insurance Institute for Highway Safety, Arlington, Va., write in an accompanying editorial that the combined results of this and other studies significantly support the benefits of graduated driver licensing for the youngest drivers.
They write:
“In the United States, depending on state law, graduated driver licensing programs have been directed primarily at 16-year-olds and, to a lesser extent, 15- and 17-year-olds, and most evaluations have focused on these ages. Moreover, as discussed by Masten et al, there are various ways in which graduated driver licensing may negatively affect 18- and 19-year-olds. There currently is no empirically validated explanation for effects of graduated driver licensing, positive or negative, on older teenagers. To the extent that some of the positive effects at earlier ages may be blunted, this is a serious issue deserving attention by researchers and policy makers. It is likely that further reductions in crashes involving young drivers can be achieved by strengthening individual components of licensing laws.”
Written by Petra Rattue