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Key research findings
- Tefft et al. (2013), in a national U.S. study of fatal crashes and crashes of all severity, found that the fatal crash risk per mile traveled quadrupled for 16 to 17-year old drivers when there were three or more passengers younger than age 21 and no older passengers in the vehicle, compared with the time when driving alone.
- The Tefft study also showed that with one young passenger there was a 44% greater risk of driver death in a crash per mile traveled compared with having no passengers.
- For all crashes in the Tefft study, risks of involvement followed this same pattern but were smaller and not statistically significant.
- Both state and national studies have reported positive effects of passenger restrictions, and crash reductions have been reported for both fatal and nonfatal crashes.6
Where to set the passenger limit to yield the most positive effect has not been settled – no passenger limits versus one passenger.
- McCartt et al. (2010) indicated a 21% reduction in fatal crash rates for zero passengers and 7% for one passenger.
- Masten et al. (2013) found a 9% reduction in fatal crash involvements for zero passengers at age 16 and 20% for one passenger.
- Masten et al. (2014) also indicated positive effects on traffic crashes outcomes for one-passenger limits.
Thus, while both passenger restrictions allowing zero or one person appear to have positive effects, it is not clear which is most beneficial from a safety standpoint. Thus the question as to how strictly to set passenger limits is presently unresolved.