Graduated drivers licensing programs reduce young drivers crash risk by 20 to 40% (Shope, 2007).
Shope (2007) recently conducted a review of evaluations of graduated driver licensing (GDL), which establish limits on newly licensed drivers which are gradually lifted (e.g., driving at night, with passengers). She identified 27 studies, 21 of which assessed the effects of GDL within 14 jurisdictions/states across the U.S. and Canada and 6 that assessed GDL nationwide. Effects were consistent, indicating that GDL laws reduce young drivers crash risk by 20 to 40%. Recent studies by Zhu et al (2009) (finding a 31% reduction in the driver injury rate among 16-year-olds in New York), Kirley et al. (2008) (finding reduction of 18-37% in various indicators of crashes or injuries in Maryland), and Neyens et al. (2008) (finding similar crash reductions among 16- and 17-year-olds in Iowa) are consistent with the previous literature.
Strong GDL laws consistently prohibit or highly restrict nighttime driving by younger teens. And several studies have reported significant reductions in nighttime crashes associated with GDL programs (e.g., Cooper et al., 2004; Masten and Hagge, 2003; Shope, 2007; Shope and Molnar, 2004). Since nighttime is also the highest risk time for alcohol-related crashes (Williams et al., 2002), GDL laws are clearly expected to reduce teen alcohol-related crashes. While the research evidence is strong that GDL laws reduce teen car crashes, their effects specifically on alcohol-related crashes have rarely been studied. One exception is Begg et al. (2001), who confirmed that the GDL law in New Zealand resulted in significant reductions specifically in alcohol-related crashes among young drivers.