In 2015, Indiana extended its Graduated Driver Licensing system, previously only applicable to new drivers younger than 18, to all new drivers under age 21. This study examines the crash rates of new Indiana drivers first licensed at ages 18-20 before and after that change.
Graduated Driver Licensing (GDL) systems were designed to protect young novice drivers by creating a safe environment in which to learn to drive and limit exposure to known high-risk conditions until the drivers have amassed at least several months of experience driving. A large body of research has found that GDL systems have substantially reduced the rates of crashes, injuries, and deaths of 16- and 17-year-old drivers. However, AAA Foundation research has estimated that as many as one in three drivers do not obtain their first license until the age of 18 or older. Although previous AAA Foundation research has also shown that that new drivers licensed at ages 18-20 have crash rates similar to equally-inexperienced younger beginners and much higher crash rates than same-aged peers with more driving experience, most states do not apply most key provisions of their GDL programs to new drivers aged 18 years or older.
On July 1, 2015, the state of Indiana modified its Graduated Driver Licensing (GDL) system, extending restrictions on driving late at night and on carrying young passengers—previously only applicable to newly-licensed drivers younger than 18—to all newly-licensed drivers under the age of 21. Specifically, the updated GDL program restricted new drivers under age 21, from driving between the hours of 10 p.m. and 5 a.m. and from carrying non-family passengers for their first six months of license driving, unless they had a qualifying supervisor (a licensed driver aged 25+, or 21+ if the supervising driver is the driver’s spouse). This study examines the crash rates of drivers who received their first driver’s license at ages 18-20 in the state of Indiana before versus after Indiana updated its GDL system.
Researchers from the University of North Carolina Highway Safety Research Center obtained data on drivers licensed in the state of Indiana and drivers involved in crashes in the state from January 2012 through April 2018. Rates of crashes were compared between drivers who received their first driver’s license at ages 18-20 before versus after Indiana extended its Graduated Driver Licensing system to apply to new drivers of this age. Statistical models were used to control for other factors that besides the licensing system that might also influence crash rates. Separate analyses also examined the proportion of newly licensed drivers’ crashes that occurred between 10 p.m. and 5 a.m. and crashes in which passengers were present—conditions restricted for the first six months of licensed driving under the updated licensing system.
Drivers licensed under the updated GDL system had higher rates of crashes than did drivers licensed under the previous GDL program during their first year of licensed driving. This finding was likely attributable to an overall increase in driving exposure, and not an effect of the modified GDL system per se. The total number of crashes of drivers of all ages increased substantially over the study period both statewide and nationally, likely due at least in part to increases in driving associated with increased economic activity following the Great Recession.
The rate of crashes that occurred between 10 p.m. and 5 a.m. was slightly higher among drivers licensed under the updated GDL system than among those licensed under the previous system; however, the proportion of all crashes that occurred during these hours did not change at all, suggesting that the increased rate was attributable to an overall increase in driving generally and not an increase in the amount or danger of driving at night.
The rate of crashes in which passengers were present was also slightly higher among drivers licensed under the updated GDL system than among those licensed under the previous system. However, similarly to night-time crashes, the proportion of crashes in which passengers were present did not differ between drivers licensed under the updated versus previous GDL system.