Young Driver Crash Rates in New Jersey by Driving Experience, Age, and License Phase

Previous studies have demonstrated that both inexperience and developmental factors (often operationalized as age) are important predictors of young driver crash risk. However, few previous studies have concurrently assessed the influence of both age and experience on young driver crashes, and to the authors' knowledge no U.S. study has done so in the post-Graduated Drivers Licensing (GDL) era. Further, while the sharp increase in crash risk that occurs at the point of transition between a learner’s permit and intermediate license has been well-described, little attention has been given to the transition from intermediate to full licensure. Thus, the objective of this study was to use a linked licensing-crash database from New Jersey to examine the independent and joint contributions of age at licensure, driving experience, and GDL license phase on 24-month crash rates among the population of New Jersey (NJ) drivers who were first licensed from 17 through 20 years old. Briefly, it was found that, overall, the crash rate for young NJ intermediate drivers in their first month of licensure was 229 per 10,000 licensed drivers. A more nuanced picture emerged when crash rate trends were stratified by age at licensure. First-month rates were higher among the youngest NJ drivers (licensed at 17y0m) than for older adolescent novice drivers. Further, drivers who delayed licensure experienced a reduced “steepness” in the slope of their crash rates in the critical initial months of independent driving, but there did not appear to be any incremental benefit of delayed licensure once drivers had six months of driving experience. Second, at each age, those with more driving experience—as measured by the length of time they held a license—had lower crash rates; however, the benefit of increased experience was greatest for the substantial proportion of NJ teens licensed immediately after becoming eligible (at 17y0m). Finally, regardless of the age at licensure or the length of driving experience, teen drivers’ crash rate increased substantially at the point of transition to a full license, while drivers of a similar age who remained in the intermediate phase continued to experience a decline in crash rates.