To address the high fatality rate among teenage drivers, most states have adopted one or more elements of a GDL system, which allows teenagers to gradually receive full driving privileges. Almost every state has some form of restriction on young drivers.

The three phases of GDLs are:

• a supervised learners period
• an intermediate license, which allows unsupervised driving depending on various situations
• a full privileges license

According to the Insurance Institute for Highway Safety, all but five states (Arizona, Arkansas, Kansas, Minnesota and North Dakota) have an intermediate stage, but the systems vary. A teenager with a learners permit is required to remain in that stage for a minimum period, usually six months. A learners permit also requires that when driving, a teenager must be supervised by an adult, pass vision and knowledge tests and pass a test before receiving an intermediate license. In addition, the driver must wear a seat belt and be traffic- and alcohol-offense free, and restricted from driving at night. An intermediate or restricted license requires a minimum of six months and restricts passengers and night-time driving. In all stages, there is zero-tolerance for drunk driving, and a requirement to be traffic-offense free.

Florida was the first state to adopt a GDL program in 1996. In South Carolina, where the GDL law went into effect in 1998, the percentage of teenagers involved in crashes fell from 14.5 percent in 1998 to 13.0 percent in 1999. Alabama's GDL law was enacted in October, 2002. By 2003, state troopers reported accidents caused by 16-year-old drivers fell from 5,905 to 5,263; for 17-year-olds, crashes fell from 6,174 to 5,980.

Click here to see how California's teen crash rates have dropped because of new GDL provisions.

GDLs have also reduced deaths among teenage drivers in New Zealand, Australia and Canada, where versions of the system exist. A 2002 study conducted in Nova Scotia concludes that accident reductions among young beginning drivers occur in both the learner and intermediate stages. This is the first long-term study to investigate the benefits of each licensing stage. The findings of the study, Specific and Long-term Effects of Nova Scotia's Graduated Licensing Program, mark the first six months of the learner stage as the most significant period of crash reductions. For beginning drivers who got their learners permit at 16 or 17 years old, crashes declined 51 percent. During the intermediate stage, when drivers are allowed to drive unsupervised except late at night, crashes were reduced by 9 percent in the first year and 11 percent in the second year. Crash rates increased by 4 percent, however, during the first year after the drivers graduated to full license status. Nova Scotia's GDL program was adopted in 1994, before many U.S. states began adopting the system.

• Some people question whether 16-year olds should be allowed to get a drivers license. This issue has gained some attention from a 2005 National Institute of Mental Health report that shows the part of the brain that weighs risks, makes judgments and controls impulsive behavior develops throughout the teen years and does not mature until around age 25.
• Graduated Drivers License (GDL) programs are helping to reduce teen driving deaths. States began enacting GDL laws in the 1990s. The graduated license program is a three-stage license phase-in process that allows young drivers to gain experience before receiving a full-privilege license. The latest data from NHTSA shows the fatality rate for 16 to 20 year old vehicle occupants in motor vehicle crashes per 100,000 population was 27.07 in 2004, down from 27.67 in 2003 and 30.46 in 1994. The 2004 rate was the lowest since record keeping began in 1975.
• Benefits of Graduated Drivers License Programs: A study sponsored by State Farm Insurance Company and the federal Centers for Disease Control and Prevention found that North Carolina's GDL program reduced hospitalizations and hospital costs by more than one-third for the youngest drivers in the state. The study, conducted by researchers at the University of North Carolina at Chapel Hill, shows that in the 46 months after the state's GDL law went into effect in 1997, hospitalizations of 16-year-old drivers fell by 37 percent and hospital costs for these drivers fell 31 percent, or $650,000, per year.
  
  The lead author of the study says that the findings suggest that the reductions result from 16-year olds driving less, rather than from improvements in their driving skills. In addition, a reduction in the number of hospitalizations among 17-year old drivers was noted, but it was not statistically significant. A 2001 study, based on crash data, found that there had been a 57-percent drop in fatal accidents involving 16-year olds since the law went into effect.
• According to the Insurance Institute for Highway Safety (IIHS), the youngest drivers have far more crashes than older people especially in their first months of getting their licenses. Based on a study of crashes involving 16-year olds, researchers found that not paying enough attention or taking enough notice of surroundings are the major reasons for crashes. Researchers interviewed 16-year olds who had been in nonfatal crashes in Connecticut, and found that most of them involved a single vehicle. Major reasons for at-fault collisions were failing to see another vehicle or a traffic signal, mostly because they did not look thoroughly, were daydreaming or distracted by things inside and outside their vehicles. The study was published by the IIHS in January 2007.
• A study released in July 2006 found that GDL programs can reduce the incidence of fatal crashes for 16-year old drivers by an average of 11 percent. Researchers from the Johns Hopkins Bloomberg School of Public Health found that when states had comprehensive GDL programs, those with a least five of the most important elements in effect, there was a 20-percent reduction in fatal crashes involving 16-year old drivers. These elements were:
  1. A minimum age of 15 1/2 for obtaining a learners permit
  2. A waiting period after obtaining a learners permit of at least three months before applying for an intermediate license
  3. A minimum of 30 hours of supervised driving
  4. Minimum age of at least 16 years for obtaining an intermediate license
  5. Minimum age of at least 17 years for full licensing
  6. A restriction on carrying passengers.
• The study was supported by NHTSA and the Centers for Disease Control and Prevention. Researchers used data from 1994-2004 from NHTSA's Fatality Analysis Reporting System and examined fatal crash data in 36 states that had GDL programs and in seven states that did not. They found that in states that had six or seven components, the fatal crash reduction was 21 percent.
• Fatality and injury crash rates for 16-year-old drivers were 20 percent lower in a state with nighttime and passenger restrictions than in a comparison jurisdiction that lacked these provisions, according to a study released in June 2006 by the AAA Foundation for Traffic Safety.
  
  For the study, the Traffic Injury Research Foundation (TIRF) compared crash rates and crash patterns of teenage drivers in one jurisdiction with nighttime and passenger restrictions during the intermediate stage of GDL with those in another jurisdiction whose GDL program did not include such restrictions. TIRF also surveyed a random sample of 500 crash-free and 500 crash-involved, newly-licensed teens and their parents in each of two jurisdictions. The study found that twice as many crash-free teens reported never having violated their state's passenger restriction provision, compared with teens that had crashed.
• One key feature of GDL programs is the passenger restriction which limits the number of passengers a teen driver may have in the vehicle to eliminate distractions. Thirty-eight states and the District of Columbia have enacted these laws with various provisions regarding the ages of passengers and the number of passengers a teen driver may transport. According to a 2005 study, when teens drive other teens, they tend to drive faster than other motorists and leave less distance between their vehicles and the vehicles in front of them. They speed more frequently when there are other teens in vehicles, especially males. These findings by researchers at the National Institutes of Health and Westat were compiled from data collected at 13 sites on roads in the Washington, D.C. area, where over 3,000 passenger vehicles were observed, including 471 driven by teenagers.
• Children's Hospital of Philadelphia and State Farm released a study in June 2007 that found children are safer when riding in a vehicle with a teen driver who is their sibling rather than a teen driver who is not related to them. Earlier research found that children driven by teens are twice as likely to sustain crash injuries, a finding that prompted legislators in many states to enact passenger restriction laws. The new study showed children's risk of crash injury where the teen driver is a sibling is 40 percent lower. This new finding supports the exceptions in some state laws that allow teens to drive family members only.
  
  Information provided by Insurance Information Institute (III).