title: Examining trajectories of adolescent risk factors as predictors of subsequent high-risk driving behavior.
abstract: OBJECTIVE
  To examine the effects on early high-risk driving behavior of changes over time (trajectories) in adolescent alcohol use, friends' support for drinking, susceptibility to peer pressure, and tolerance of deviance.
  
  
  METHODS
  Statewide driving data were obtained for 4813 subjects who had completed at least two previous school-based questionnaires. The self-administered questionnaire data provided predictor measures from 5th through 10th grades. Trajectory information on predictor measures was summarized using each measure's slope over time and level at the 10th grade data collection (last value). Regression models used serious offenses, alcohol-related offenses, serious crashes, and alcohol-related crashes as outcomes, trajectory measures as predictors, and produced parameter estimates adjusted for demographic measures. Probabilities of having a serious offense or serious crash for five sample trajectories on each measure were obtained from the estimated regression models.
  
  
  RESULTS
  All four predictor measures were important, particularly in predicting serious offenses, alcohol-related offenses, and alcohol-related crashes. The highest probabilities for young adult high-risk driving were found among those with consistently high or increasingly high trajectories of friends' support for drinking, susceptibility to peer pressure, and tolerance of deviance.
  
  
  CONCLUSIONS
  Programs to prevent adolescent risk behavior should take into account environmental and personality influences. Prevention efforts need to emphasize preserving low levels, preventing increases, and promoting decreases over time of adolescent risk factors for unhealthy behaviors, such as high-risk driving.
authors.affiliation: Transportation Research Institute, University of Michigan, Ann Arbor, Michigan 48109-2150, USA. jshope@umich.edu
authors.forename: Jean T
authors.initials: JT
authors.lastname: Shope
authors.forename: Trivellore E
authors.initials: TE
authors.lastname: Raghunathan
authors.forename: Sujata M
authors.initials: SM
authors.lastname: Patil
mesh_terms: D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D000293:Adolescent; D000367:Age Factors; D000428:Alcohol Drinking; D001334:Automobile Driving / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D015233:Models, Statistical; D010379:Peer Group; D016012:Poisson Distribution; D011237:Predictive Value of Tests; D012307:Risk Factors; D012737:Sex Factors; D011795:Surveys and Questionnaires