Newly licensed adolescent drivers have skill deficits that increase risk for motor vehicle crashes. Development of programs targeted to prelicensed adolescents has been hindered by concerns about encouraging overconfidence and early licensure. The study had 2 primary objectives: (a) determine whether an Internet-based intervention designed to improve parent-supervised practice (TeenDrivingPlan [TDP]) influenced adolescents' time to licensure and parents' perceptions of adolescents' driving skill, expertise, and safety and (b) evaluate the association of these perceptions and practice diversity (number of different environments where practiced occurred) with time to licensure. Method: A randomized controlled trial was used to compare TDP with a control condition. Participants (N ± 295 parent-adolescent dyads) completed periodic surveys over 24 weeks and were subsequently followed for up to a year to determine adolescents' licensure status. Results: TDP did not influence time to licensure and did not affect parents' perceptions of skill, expertise, and safety. Practice diversity was associated with faster licensure. A more favorable perception of adolescents' skill in comparison to peers was associated with faster licensure. Conclusions: Targeting parents' beliefs about adolescents' safety in relation to other road users may not be conducive to altering licensing trajectories, whereas sensitizing parents to their adolescents' emerging skills might be more effective in promoting safe entry into licensure.