title: Urban sprawl and miles driven daily by teenagers in the United States.
abstract: BACKGROUND
  Urban sprawl's association with increased automobile reliance and daily mileage is well established among adults. However, sprawl's specific impact on teen driving exposure is unknown. Teen driver fatality rates per mile driven are significantly higher than adults, making the identification of environmental influences on travel behavior particularly important in this age group.
  
  
  METHODS
  Driving and demographic data for 4528 teens (weighted=10.5 million) aged 16-19 years were obtained from the 2001 National Household Transportation Survey (NHTS). County-level sprawl was measured using an index developed by Ewing et al. The association between daily miles driven by teens and sprawl, controlling for demographic characteristics, was modeled using ordinal logistic regression. The predicted probability of driving >20 miles in counties with varying degrees of sprawl also was calculated.
  
  
  RESULTS
  Of the surveyed teens, 48% did not drive, 27% drove <20 miles/day, and 25% drove >20 miles/day. Of the 52% of teens who reported driving, the average distance driven was 15.6 miles/day. More-pronounced sprawl was associated with increased daily mileage (p<0.001). Overall, teens in sprawling counties were more than twice as likely to drive >20 miles/day than teens in compact counties. This trend was most prominent among the youngest drivers. For example, the predicted probability of boys aged 16-17 years driving >20 miles per day varied from 9% to 24% in compact versus sprawling counties.
  
  
  CONCLUSIONS
  Sprawl is associated with increased daily mileage by teen drivers. Given the stark relationship between driving exposure and fatality risk among teens, increased efforts to understand and modify the effects of sprawl on adolescent driving behavior are necessary.
authors.affiliation: Department of Emergency Medicine, School of Medicine and Center for Applied Biomechanics, School of Engineering, University of Virginia, Charlottesville, Virginia 22908, USA. mtrowbridge@virginia.edu
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Trowbridge
authors.forename: Noreen C
authors.initials: NC
authors.lastname: McDonald
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D000328:Adult; D001334:Automobile Driving / Q000706:statistics & numerical data*; D003430:Cross-Sectional Studies; D004779:Environment Design; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D014195:Travel; D014481:United States; D014506:Urban Renewal