title: The association of graduated driver licensing with miles driven and fatal crash rates per miles driven among adolescents.
abstract: BACKGROUND
  Graduated driver licensing (GDL) laws are associated with reduced crash rates per person-year among adolescents. It is unknown whether adolescents crash less per miles driven or drive less under GDL policies.
  
  
  METHODS
  We used data from the US National Household Travel Survey and Fatality Analysis Reporting System for 1995-1996, 2001-2002 and 2008-2009. We compared adolescents subject to GDL laws with those not by estimating adjusted IRRs for being a driver in a crash with a death per person-year (aIRRpy) and per miles driven (aIRRm), and adjusted miles driven ratios (aMR) controlling for changes in rates over time.
  
  
  RESULTS
  Comparing persons subject to GDL policies with those not, 16 year olds had fewer fatal crashes per person-year (aIRRpy 0.63, 95% CI 0.47 to 0.91), drove fewer miles (aMR 0.79, 95% CI 0.63 to 0.98) and had lower crash rates per miles driven (aIRRm 0.83, 95% CI 0.65 to 1.06). For age 17, the aIRRpy was 0.83 (95% CI 0.60 to 1.17), the aMR 0.80 (95% CI 0.63 to 1.03) and the aIRRm 1.03 (95% CI 0.80 to 1.35). For age 18, the aIRRpy was 0.93 (95% CI 0.72 to 1.19), the aMR 0.92 (95% CI 0.77 to 1.09) and the aIRRm 1.01 (95% CI 0.84 to 1.23).
  
  
  CONCLUSIONS
  If these associations are causal, GDL laws reduced crashes per person-year by about one-third among 16 year olds; half the reduction was due to fewer crashes per miles driven and half to less driving. For ages 17 and 18, there was no evidence of reduced crash rates per miles driven.
authors: Department of Epidemiology, West Virginia University, Morgantown, West Virginia, USA Injury Control Research Center, West Virginia University, Morgantown, West Virginia, USA.
authors: Motao
authors: M
authors: Zhu
authors: School of Public Health and Harborview injury Prevention & Research Center, University of Washington, Seattle, Washington, USA.
authors: Peter
authors: P
authors: Cummings
authors: Injury Control Research Center, West Virginia University, Morgantown, West Virginia, USA.
authors: Songzhu
authors: S
authors: Zhao
authors: Injury Control Research Center, West Virginia University, Morgantown, West Virginia, USA Department of Emergency Medicine, West Virginia University, Morgantown, West Virginia, USA.
authors: Jeffrey H
authors: JH
authors: Coben
authors: Department of Epidemiology and Public Health, School of Medicine, University of Maryland, Baltimore, Maryland, USA.
authors: Gordon S
authors: GS
authors: Smith
mesh_terms: D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D000293:Adolescent; D001334:Automobile Driving / Q000331:legislation & jurisprudence*; D005260:Female; D006801:Humans; D015994:Incidence; D008004:Licensure / Q000592:standards*; D008297:Male; D014481:United States / Q000453:epidemiology