New Jersey (NJ) implemented the first Graduated Driver Licensing (GDL) decal provision in the U.S. in May 2010. An initial study reported a 1-year post-decal decrease in the crash rate among NJ intermediate drivers aged <21 years. Longer-term analysis is critical for policymakers in other states considering whether to implement a decal provision. This study, published in the American Journal of Public Health, evaluates the longer-term (2-year) effect of NJ’s decal provision on overall and age-specific crash rates of young drivers with intermediate licenses.
The study finds the adjusted crash rate for intermediate drivers was 9.5% lower in the 2-year post-decal period than the 4-year pre-decal period (95% CI=0.88, 0.93). Crash rates decreased 1.8% per year before the provision and 7.9% per year in the post-decal period (p<0.001 for difference in slopes). For several crash types, effects appeared to be particularly strong for 18- and 19-year-olds. An estimated 3,197 intermediate drivers had crashes prevented. NJ’s decal provision was associated with a sustained decline in intermediate driver crashes. Future research should aim to better understand the causal mechanism by which NJ’s decal provision may have exerted an effect.