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Home > Center Projects > Studying the effects of Graduated Driver Licensing

Studying the effects of Graduated Driver Licensing

Since GDL was enacted in North Carolina CSYD researchers have conducted numerous analyses to track its effects and identify needed enhancements.

Early Effects

The original study of early GDL effects was published in the Journal of the American Medical Association, along with a companion study in Michigan. The dramatic crash reductions reported have helped propel other states to emulate the actions and successes of these two early GDL systems. Currently only four states do not have graduated driver licensing systems.

Reactions to GDL

A large majority of adults and teens believe that graduated driver licensing is a good idea. More than 95 percent of North Carolina parents — regardless of whether they lived in an urban or rural area — either “highly approved” or “somewhat approved” of GDL, according a survey conducted by CSYD researchers. Similarly, 80 percent of North Carolina teens, regardless of where they live, were found to either highly approve or somewhat approve of the system.

CSYD researchers have also examined the extent to which critical restrictions in North Carolina's graduated driver licensing (GDL) system are known, adhered to, and enforced. Telephone interviews with 900 teens and their parents, revealed that awareness of North Carolina's night and passenger restrictions was very high among both groups.

Highlights of the findings include:

• Ten percent of teenagers reported violating the night restriction without their parents' knowledge, and 15 percent had done so with their parents' approval.
• Only 4 percent of parents reported allowing their teenagers to drive with more than one teenage passenger, but 19 percent of teenagers reported that they were allowed to do this.
• Violations of the passenger restriction without parental knowledge were more common than violations of the night restriction (22 percent vs. 10 percent, respectively).
• Among teenagers who violated restrictions without their parents' knowledge, most reported doing so only once or a few times.
• There was very low awareness of the seat belt requirement.

Interviewers asked about teens’ and parents’ perception of the enforcement of GDL restrictions. Teens expressed little concern about detection, although a majority reported driving more carefully to avoid police notice. Neither parents nor teens knew much about police enforcement of GDL restrictions.

Findings of theses studies are reported more fully in:

• Foss RD, Feaganes JR, Rodgman EA (2001) Initial effect of graduated driver licensing on 16 year-old driver crashes in North Carolina. Journal of the American Medical Association; 286:1588-1592.
• Goodwin, A.H., & Foss, R.D. (2004). Graduated driver licensing restrictions: awareness, compliance, and enforcement in North Carolina. Journal of Safety Research, 35, 367-374.
• Goodwin, A.H., Wells, J.K., Foss, R.D., & Williams, A.F. (2006). Encouraging compliance with graduated driver licensing restrictions. Journal of Safety Research, 37, 343-351.

GDL and Health Care Costs

A recently completed study, supported in part by a gift from the North Carolina Public Affairs office of State Farm Insurance, documented the cost-reducing effects of GDL by examining hospital discharge data.

Long Term Effects of GDL

Two studies currently under way to document the long-term effects of graduated licensing on young driver crashes are nearing completion. One of these looks at monthly crash rates for 16 and 17 year-old drivers from 1991 through 2004, to determining whether the initial effects of GDL have continued (they have) and to see how addition of the passenger restriction to the NC GDL program in December 2002 affected crash rates (they have remained largely stable, but multi-passenger crashes have declined).

The second study examines whether GDL actually makes for better, i.e., less crash-prone drivers. Numerous studies have now shown that young teen crashes are reduced by graduated licensing, but most, if not all, of the reduction appears to result from reduced driving and less driving in risky conditions, which is one of the primary goals of GDL. An additional expected benefit of GDL, better prepared teen drivers, has yet to be documented. Results of the current study appear to provide the first clear indication that, at least in North Carolina, teens who have been licensed under the GDL system are less likely to crash even years after they have “graduated” from the protective restrictions of the system.

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