Many countries, including Great Britain, New Zealand, Australia, Canada, and France, have required those under the jurisdiction of Graduated Driver Licensing (GDL) laws to identify their licensing status through the use of placards or decals (also known as L-plates and P-plates).

These GDL identifiers and decals are required to be highly visible on any vehicle novice teen drivers operate. While some of these provisions have been in place for decades, they are a relatively new concept for GDL in the United States. To date, only New Jersey requires the use of GDL decals by its learner and intermediate drivers.

While numerous US studies of GDL and specific GDL provisions have demonstrated GDL's effectiveness in reducing novice teen driver crashes, the effectiveness of GDL provisions overall has been limited by the inability of police to enforce them. Without a GDL identifier or decal, it is difficult for law enforcement officers to easily determine who is a learner or intermediate driver without a traffic stop and visual inspection of the license. Experts believe decals may increase the ability of police to enforce GDL and teens’ willingness to comply with GDL restrictions and other important traffic safety laws, as well as to alert others to drive safely around a novice.

CHOP Principal Investigator Allison E. Curry, PhD, MPH led an evaluation of NJ's decal provision, implemented in May 2010. The study showed that NJ youth and other road users are safer as a result of its implementation:

• The decal provision is associated with a two-year decline in crash rates among teens with an intermediate license.
•  After accounting for age, gender, calendar month, unleaded gas prices, and crash trends among older licensed drivers, the crash rate for these drivers declined 9.5% in the first two years after the new decal requirement took effect compared with the four years before the requirement.
•  Crash involvement of an estimated 3,197 young intermediate drivers was prevented in the first two years post-decal.

Dr. Curry and her colleagues also found a 14% increase in the rate of GDL-related citations issued to intermediate drivers over the decal’s first year of implementation, although the increase seemed to be concentrated in the few months after implementation. Further research is needed to determine causal pathways to crash reduction. Click here to view an infographic on how GDL decals may work to reduce teen driver crashes.