Although studies of individual jurisdictions have indicated that nighttime restrictions and passenger limitations are effective in reducing novice driver crashes, few national studies have focused on these two components of GDL. This national panel study, using different dependent measures, has augmented the past research. This study showed that night restrictions do reduce nighttime fatal crashes involving 16- and 17-year-old drivers by about 10% relative to the fatal crash involvement of older peers. The night restriction was also associated with a 13% reduction in 16- and 17-year-old drinking drivers in nighttime fatal crashes relative to other young (19- to 20-year-old) drivers not affected by the restriction. States that do not have night restrictions should strongly consider adopting them.
The study also showed that teen passenger restrictions significantly reduce fatal crashes involving 16- and 17-year-old drivers with teen passengers by about 9% relative to older drivers (aged 19 to 25). A recent study by Williams, Ali, and Shults (2010)
found that the percentage of fatal crashes involving 16- and 17-year-old drivers who had teen passengers present has not changed nationally over a recent 5-year period (2004–2008). In our study, however, the passenger restriction was effective in reducing fatal crashes with teen passengers relative to older peers, and the most effective restriction was the one not allowing any teen passengers.
Therefore, states without teen passenger limitations should also strongly consider adding them to their GDL systems. In addition, states that allow one, two, or more teen passengers during the intermediate stage of licensing should consider modifying that restriction to no teen passengers.
It appears that delaying full licensure of young novice drivers via GDL systems is having the desired effect nationally. Most 16- and 17-year-old drivers are either permit holders (where adults aged 21 or older must always be present) or intermediate stage holders (where solo driving is permitted, but with nighttime and teen passenger restrictions). These required stages of driving are, in effect, delaying full licensure for young drivers where no such restrictions are present.
This premise appears to be verified by the Federal Highway Administration's (FHWA, 2008)
data on the distribution of licensed drivers. Only 30.7% of 16-year-olds in 2008 had driver’s licenses, and only 49.2% of 17-year-olds had licenses, many of which may have been learner’s permits or provisional licenses (it is not clear when examining those data). These rates compare to 68% of 18-year-olds and 76.7% of 19-year-olds reported to be licensed by FHWA. However, as pointed out by Ferguson, Teoh, and McCartt (2007)
, caution must be exhibited when interpreting the FHWA data on the licensing of young drivers.
More research is clearly needed on the effects of GDL systems in the United States and other countries around the world. Because of limitations in the FARS data, we still do not have answers to the following questions:
- Is the delay of solo driving the most important aspect of GDL, or are other components more important (e.g., night and passenger restrictions, hours of supervised practice, no violations or crashes in order to graduate to the next phase)?
- Are the lengths of the individual phases of GDL systems important in reducing the crash risk?
- What are the individual GDL effects on 16-year-olds, 17-year-olds, 18-year-olds, and 19-year-olds? Is there any GDL carryover effect on older age groups?
The contains tables of the ages of licensure for the intermediate- and full-license stages by state. Studies are needed to determine which of these age limits are playing a key role in the safety of young novice drivers.
Highlights of GDL Study for JSR
- We studied the effects of nighttime restrictions and teenaged passenger limitations in graduated driver licensing (GDL) systems on novice driver involvements in fatal crashes.
- Nighttime restrictions were found to reduce 16- and 17-year-old driver involvements in nighttime fatal crashes by an estimated 10% and 16- and 17-year-old drinking drivers in nighttime fatal crashes by 13%.
- Passenger restrictions were found to reduce 16- and 17-year-old driver involvements in fatal crashes with teen passengers by an estimated 9%.
- States without the nighttime or passenger restrictions in their GDL law should strongly consider adopting them.