title: Teen driver risk in relation to age and number of passengers, United States, 2007-2010.
abstract: OBJECTIVE
  To provide updated estimates of the relationship between the number and ages of passengers present in a vehicle and the crash risk per mile driven of 16- and 17-year-old drivers.
  
  
  METHODS
  Data on crashes that occurred in years 2007-2010 and data on the number of miles driven in years 2008-2009 were examined. Rates of crash involvement and driver death per mile driven were estimated for 16- and 17-year-old drivers with no passengers; with 1, 2, and 3 or more passengers younger than age 21 (and no older passengers); and with at least 1 passenger aged 35 or older.
  
  
  RESULTS
  For 16- and 17-year-old drivers, having 1 passenger younger than age 21 (and no older passengers) was associated with 44 percent greater risk per mile driven of being killed in a crash, compared to having no passengers (relative risk [RR]: 1.44, 95% confidence interval [CI]: 1.01-2.04). Having 2 passengers younger than age 21 was associated with double the risk of being killed in a crash, compared to having no passengers (RR: 2.02, 95% CI: 1.36-2.99). Having 3 or more passengers younger than age 21 was associated with roughly quadruple the risk of being killed in a crash, compared to having no passengers (RR: 4.39, 95% CI: 1.45-13.31). The relative risk of being involved in any police-reported crash in the presence of young passengers followed a similar pattern; however, the differences in risks of being involved in any police-reported crash were smaller and were not statistically significant. Having at least 1 passenger aged 35 or older in the vehicle was associated with a 62 percent lower risk per mile driven of being killed in a crash (RR: 0.38, 95% CI: 0.24-0.60) and a 46 percent lower risk of being involved in any police-reported crash (RR: 0.54, 95% CI: 0.31-0.93) for 16- and 17-year-old drivers, compared to having no passengers.
  
  
  CONCLUSIONS
  These results show that although the overall number of teen driver fatalities has decreased substantially over the past several years, carrying young passengers is still a significant risk factor for young drivers. In contrast, carrying adult passengers is associated with significantly lower risk of crash involvement.
authors: AAA Foundation for Traffic Safety, Washington , DC 20005, USA. btefft@aaafoundation.org
authors: Brian C
authors: BC
authors: Tefft
authors: Allan F
authors: AF
authors: Williams
authors: Jurek G
authors: JG
authors: Grabowski
mesh_terms: D000063:Accidents, Traffic / Q000401:mortality / Q000706:statistics & numerical data*; D000293:Adolescent; D000328:Adult; D001334:Automobile Driving / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D018570:Risk Assessment; D012307:Risk Factors; D014481:United States / Q000453:epidemiology