Initial effects of graduated driver licensing on 16-year-old driver crashes in North Carolina

Abstract

Context: Since 1997, 32 states have enacted graduated driver licensing (GDL) systems to reduce crash rates among young novice drivers.

Objective: To determine the initial effect of the North Carolina GDL system on crashes among 16-year-old drivers.

Design, setting, and subjects: Comparison of population-based North Carolina motor vehicle crash rates before (1996-1997) and after (1999) 16-year-old drivers were licensed under the GDL system. To control for other factors that might have influenced crashes, changes for 16-year-old drivers were compared with those of drivers 25 to 54 years of age. Crashes per licensed driver were also examined.

Intervention: The North Carolina GDL system, enacted December 1, 1997, requires beginning drivers 15 to 17 years of age to hold level 1 licenses, allowing driving only while supervised by a designated adult for a full year; followed by level 2 licensure, allowing unsupervised driving from 5 AM to 9 PM and supervised driving at any time for at least 6 months; and, finally, level 3-a full, unrestricted license.

Main outcome measures: Rates of motor vehicle crashes among 16-year-old drivers in 1996-1997 vs 1999, overall and by crash severity (fatal, injury, and noninjury), time (night vs day), type (single vs multiple vehicle), driver alcohol use, and driving environment (more vs less rural counties).

Results: Crash rates declined sharply for all levels of severity among 16-year-old drivers after the GDL program was implemented. Following GDL, 16-year-old driver crashes were substantially less likely. Comparing 1996 with 1999, fatal crashes declined 57%, from 5 to 2 per 10 000 population (rate ratio [RR], 0.43; 95% confidence interval [CI], 0.27-0.70); crashes with no or minor injuries decreased 23%, from 1068 to 826 per 10 000 (RR, 0.77; 95% CI, 0.75-0.80). Nighttime crashes were 43% less likely (156 vs 88 per 10 000; RR, 0.57; 95% CI, 0.52-0.61) and daytime crashes decreased by 20% (951 vs 764 per 10 000; RR, 0.80; 95% CI, 0.78-0.83). Single-vehicle crashes (245 vs 175; RR, 0.71; 95% CI, 0.67-0.76) declined somewhat more than multiple-vehicle crashes (866 vs 681; RR, 0.79; 95% CI, 0.76-0.81).

Conclusion: In its initial years, the North Carolina GDL system produced substantial declines in 16-year-old driver crashes.