Key research findings
- Research establishing the safety benefits of a 12-month intermediate holding period or the optimal intermediate holding period has not been conducted.
- Senserrick and Williams (2013), in a review of the GDL and teen driver literature, concluded that blood alcohol concentration (BAC) research suggests a three-year provisional period as important, or at least until age 21, albeit the evaluations have mostly been independent of GDL requirements and relate to declines in alcohol-related crashes.5
