Background: Graduated driving licensing (GDL) programs phase in driving privileges for teenagers. We aimed to evaluate the effect of the 2007 GDL law on the incidence of total motor vehicle crashes (tMVCs) and fatal motor vehicle crashes (fMVCs) among teenagers in Massachusetts.
Methods: The Fatality Analysis and Reporting System, the Missouri Census Data Center, and the Massachusetts Department of Transportation databases were all used to create and compare the incidence of tMVCs and fMVCs before (2002-2006) and after (2007-2011) the law enactment. The following three driver age groups were studied: 16 years to 17 years (evaluating the law effect), 18 years to 20 years (evaluating the sustainability of the effect), and 25 years to 29 years (control group). As a sensitivity analysis, we compared the incidence rates per population and per licenses issued.
Results: tMVCs decreased following the law for all three age groups (16-17 years, from 7.6 to 4.8 per 1,000 people, p < 0.0001; 18-20 years, from 8.5 to 6.4 per 1,000 people, p < 0.0001; 25-29 years, from 6.2 to 5.2 per 1,000 people, p < 0.0001), but the percentage decrease in tMVC rates was less in the control group (37%, 25%, and 15%, respectively; both p's < 0.0001). The rates of fMVC also decreased in the age groups of 16 years to 17 years (from 14.0 to 8.6 per 100,000 people, p = 0.0006), 18 years to 20 years (from 21.2 to 13.7 per 100,000 people, p < 0.0001), and 25 years to 29 years (from 14.4 to 11.0 per 100,000 people, p < 0.0001). All of these results were confirmed in the sensitivity analyses.
Conclusion: The 2007 Massachusetts GDL was associated with a decreased incidence of teenager tMVCs and fMVCs, and the effect was sustainable. This study provides further support to develop, implement, enforce, and maintain GDL programs aimed at preventing MVCs and their related mortality in the young novice driver population.
Level of evidence: Epidemiologic/prognostic study, level III.