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Graduated driver licensing and motor vehicle crashes involving teenage drivers: an exploratory age-stratified meta-analysis
  1. Motao Zhu1,
  2. Peter Cummings2,
  3. Haitao Chu3,
  4. Jeffrey H Coben4,
  5. Guohua Li5
  1. 1Department of Epidemiology and Injury Control Research Center, West Virginia University, Morgantown, West Virginia, USA
  2. 2School of Public Health and Harborview Injury Prevention & Research Center, University of Washington, Seattle, Washington, USA
  3. 3Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, Minnesota, USA
  4. 4Department of Emergency Medicine and Injury Control Research Center, West Virginia University, Morgantown, West Virginia, USA
  5. 5Departments of Anesthesiology and Epidemiology, Columbia University, New York, New York, USA
  1. Correspondence to Dr Motao Zhu, Department of Epidemiology and Injury Control Research Center, West Virginia University, PO Box 9151, Morgantown, WV 26506-9151, USA; mozhu{at}hsc.wvu.edu

Abstract

Objective Graduated Driver Licensing (GDL) has been implemented in Australia, Canada, New Zealand, USA and Israel. We conducted an exploratory summary of available data to estimate whether GDL effects varied with age.

Methods We searched MEDLINE and other sources from 1991–2011. GDL evaluation studies with crashes resulting in injuries or deaths were eligible. They had to provide age-specific incidence rate ratios with CI or information for calculating these quantities. We included studies from individual states or provinces, but excluded national studies. We examined rates based on person-years, not license-years.

Results Of 1397 papers, 144 were screened by abstract and 47 were reviewed. Twelve studies from 11 US states and one Canadian province were selected for meta-analysis for age 16, eight were selected for age 17, and four for age 18. Adjusted rate ratios were pooled using random effects models. The pooled adjusted rate ratios for the association of GDL presence with crash rates was 0.78 (95% CI 0.72 to 0.84) for age 16 years, 0.94 (95% CI 0.93 to 0.96) for 17 and 1.00 (95% CI 0.95 to 1.04) for 18. The difference between these three rate ratios was statistically significant: p<0.001.

Conclusions GDL policies were associated with a 22% reduction in crash rates among 16-year-old drivers, but only a 6% reduction for 17-year-old drivers. GDL showed no association with crashes among 18-year-old drivers. Because we had few studies to summarise, particularly for older adolescents, our findings should be considered exploratory.

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