title: History and current status of state graduated driver licensing (GDL) laws in the United States.
abstract: BACKGROUND
  The objective of this study is to describe changes in teenage driver licensing policies in the United States during the past two decades with the introduction of graduated driver licensing (GDL) programs, assess GDL laws currently in place, and discuss the possibilities and likely consequences of further changes.
  
  
  METHODS
  The history of laws introducing and amending GDL programs was tracked, based on records maintained by the Insurance Institute for Highway Safety (IIHS). Counts of states included the District of Columbia.
  
  
  RESULTS
  A few states had elements of GDL prior to the mid-1990s, and between 1996 and 2006 all other states adopted a learner period of 2 months or more, a minimum supervised practice hours requirement for the learner period, or a night or passenger restriction once initially licensed. All but seven states have upgraded their original laws one or more times. Very few states weakened their laws, usually in minor ways. In 158 instances, minimum learner periods, minimum practice hour requirements, or night or passenger restrictions were added or strengthened. Fifteen states raised the minimum age for a license allowing any unsupervised driving.
  
  
  CONCLUSIONS
  GDL policies have reduced teenage driver crashes. Most states now have at least minimum requirements for basic GDL features, although there is substantial opportunity for strengthening existing policies. Additional upgrades would result in further crash reductions, but very few have been made in recent years.
  
  
  CONCLUSIONS
  Guidelines for maximizing the crash reduction potential of GDL programs are available, based on the experience of U.S. states, other countries with GDL programs, and the evaluation literature in regard to GDL components.
authors.affiliation: Allan F. Williams, LLC, 8200 Beech Tree Road, Bethesda, MD 20817, United States. Electronic address: allan.f.williams@gmail.com.
authors.forename: Allan F
authors.initials: AF
authors.lastname: Williams
authors.affiliation: Insurance Institute for Highway Safety, 1005 North Glebe Road, Suite 800, Arlington, VA 22201, United States.
authors.forename: Anne T
authors.initials: AT
authors.lastname: McCartt
authors.affiliation: Insurance Institute for Highway Safety, 1005 North Glebe Road, Suite 800, Arlington, VA 22201, United States.
authors.forename: Laurel B
authors.initials: LB
authors.lastname: Sims
mesh_terms: D000293:Adolescent; D001334:Automobile Driving / Q000331:legislation & jurisprudence*; D006801:Humans; D007858:Learning; D008004:Licensure / Q000331:legislation & jurisprudence*; D014481:United States
keywords: GDL; Graduated driver licensing; Teenage driver licensing laws; Teenage drivers