Time to licensure for driving among U.S. teens: Survival analysis of interval-censored survey data

Abstract

Objective Novice drivers who delay in driving licensure may miss safety benefits of Graduate Driver Licensing (GDL) programs, potentially putting themselves at higher crash-risk. Time to licensure relates their access to independent transportation to potential future economic- and educational-related opportunities. The objective of this study was to explore time to licensure associations with teens’ race/ethnicity and GDL restrictions. Methods Secondary analysis using all seven annual assessments of the NEXT Generation Health Study, a nationally representative longitudinal study starting with 10th grade (N = 2785; 2009–2010 school year). Data were collected in U.S. public/private schools, colleges, workplaces, and other settings. The outcome variable was interval-censored time to licensure (event = obtained driving licensure). Independent variables included race/ethnicity and state-specific GDL restrictions. Covariates included family affluence, parent education, nativity, sex, and urbanicity. Proportional hazards (PH) models were conducted for interval-censored survival analysis based on stepwise backward elimination for fitting multivariate models with consideration of complex survey features. In the PH models, a hazard ratio (HR) estimates a greater (>1) or lesser (<1) likelihood of licensure at all timepoints. Results Median time to licensure after reaching legal driving age for Latinos, African Americans, and Non-Latino Whites was 3.47, 2.90, and 0.41 years, respectively. Multivariate PH models showed that Latinos were 46% less likely (HR = 0.54, 95%CI: 0.35–0.72) and African Americans were 56% less likely (HR = 0.44, 95%CI: 0.32–0.56) to have obtained licensure at any time compared to Non-Latino Whites. Only learner minimum age GDL restriction was associated with time to licensure. Living in a state with a required learner driving minimum age of ≥16 years (HR = 0.57, 95%CI: 0.16–0.98) also corresponded with 43% lower likelihood of licensure at legal eligibility compared to living in other states with a required learner driving minimum age of <16 years. Conclusion Latinos and African American teens obtained their license approximately three years after eligibility on average, and much later than Non-Latino Whites. Time to licensure likelihood was associated with race/ethnicity and required minimum age of learner permit, indicating important implications for teens of different racial/ethnic groups in relation to licensure, access to independent transportation, and exposure to GDL programs.