Graduated driver licensing (GDL) programs are being adopted in many
states to address the high rate of motor vehicle fatalities among teens by
requiring teenaged drivers to gain experience and maturity under conditions
of relatively low crash risk before gaining full driving privileges.
To evaluate the early impact of Michigan's GDL program on traffic crashes
among 16-year-old drivers.
Design, Setting, and Subjects
Analysis of Michigan motor vehicle crash data from 1996 (before GDL
program implementation) vs 1998 and 1999 (after GDL program implementation)
for 16-year-olds, adjusting for trends among persons 25 years or older.
Michigan's GDL program, instituted April 1, 1997, for teens younger
than 18 years entering the driver license system, includes 3 licensure levels,
each with driving restrictions and requirements to progress to the next level.
Requirements include extended, supervised practice in the learning level,
2-phase driver education, and night driving restrictions in the intermediate
Main Outcome Measures
Rates in 1996 vs 1998 and 1999 for all police-reported crashes; for
fatal injury, nonfatal injury, and fatal/nonfatal injury combined crashes;
for day, evening, and night crashes; for single-vehicle and multivehicle crashes;
and for alcohol-related crashes.
Overall, the rate of 16-year-old drivers (per 1000 population) involved
in crashes declined from 154 in 1996 to 111 in 1999 (relative risk [RR], 0.72;
95% confidence interval [CI], 0.71-0.73). After adjusting for populationwide
trends, the overall crash risk for 16-year-olds was significantly reduced
in 1999 from 1996 by 25% (adjusted RR, 0.75; 95% CI, 0.74-0.77). There were
also significant reductions for nonfatal injury and combined fatal and nonfatal
crashes; for day, evening, and night crashes; and for single-vehicle and multivehicle
crashes. Fatal crashes declined from 1996 to 1999, but not significantly (RR,
0.74; 95% CI, 0.49-1.14), and alcohol-related crashes continued at a low rate
(RR, 1.01; 95% CI, 0.80-1.29).
Analysis of the first 2 full calendar years following Michigan's GDL
program implementation indicates substantial crash reductions among 16-year-olds.
Future research is necessary to determine if these reductions are maintained
and if other jurisdictions achieve similar results.