Studies were eligible for the review if they evaluated graduated driver licensing and contained post-graduated driver licensing driving outcome or impact data. Participants in included studies were novice drivers aged between 14 and 20. Most studies reported on changes in frequency of crashes (normally including fatal and/or severe crashes) involving this group, using a time series or pre/post design. Some studies used data for older drivers as a control.
All the studies evaluated graduated driver licensing systems in the USA (individual states or the country as a whole) or Canada. Details of graduated driver licensing interventions varied between states. Time periods for pre/post comparisons ranged from one to seven years after introduction of graduated driver licensing. All the studies of the USA as a whole used the FARS (Fatality Analysis Reporting System) database with or without other data sources.
The author did not state how the studies were selected for the review, or how many reviewers performed the selection.