EXECUTIVE SUMMARY

Background In the United States in 2004, 16-year-old drivers were involved in 957 fatal crashes that killed 1,111 people. Graduated Driver Licensing (GDL) is an increasingly popular approach to reducing the excess risk of motor vehicle crashes for novice drivers. This study was undertaken to examine the fatal crash involvement rates of 16-year-old drivers in relation to implementation of GDL programs in the various States.

GDL allows novice drivers to build experience incrementally before they are exposed to more hazardous driving situations. The first phase of GDL is a learner’s period with supervised training. This is followed by an intermediate period where unsupervised driving is limited to less hazardous situations, and a final stage without restrictions.

By the end of 2004, 41 States and the District of Columbia had GDL programs that included all three stages, although these programs vary substantially in the number and strictness of the restrictive provisions. To date, several individual GDL programs have been evaluated, and a national evaluation of GDL effectiveness has been conducted; however, a comparison of GDL programs with differing components has not previously been reported.

Approach An investigation was undertaken to:

  1. assess the overall effectiveness of GDL programs across the United States in reducing fatal crashes involving 16-year-old drivers, and

  2. compare the safety benefits of GDL programs with different components.

Data on fatal crashes was obtained from the Fatality Analysis Reporting System (FARS) of the National Highway Traffic Safety Administration and population data was obtained from the U.S. Census Bureau. The research analyzed the changes in fatal crash involvement rates of 16-year-old drivers in relation to the characteristics of the various GDL programs, which differ among the States. The research focused on 43 of the 48 contiguous States, using data for 1994 through 2004.

Method Incidence Rate Ratios (IRRs) of fatal motor vehicle crashes involving 16-year-old drivers from 1994 through 2004 were calculated for each type of GDL program, adjusted for State and year. Results for 16-year-olds were compared to rates for drivers ages 20 to 24 and 25 to 29 in order to minimize the effects of time trends and changes in the driving environment and policies that were not related to GDL. Analysis was based on the total number of quarters of the year in all States (“State-quarters”) with or without specific GDL programs, excluding the four quarters before and the four quarters after enactment of any program.

Results

  1. When State-quarters where GDL programs were implemented are compared to State-quarters where they were not implemented, those State-quarters with GDL programs had an 11 percent lower fatal crash rate involving 16-year-olds. This lower fatal crash rate reflects the combined results for all States, some of which have relatively weak GDL requirements, and therefore underestimates the impact of stronger programs.

  2. Fatal crash involvement rates of 16-year-old drivers were 18 percent lower in State-quarters with any five of the seven GDL components and 21 percent lower for State-quarters with six or seven components compared to State-quarters without any of the seven components.

  3. Compared to programs without any of the seven components, fatal crash involvement rates were 16 percent to 21 percent lower in programs that included age requirements plus: 3 or more months of waiting before the intermediate stage, nighttime driving restriction, and either supervised driving of at least 30 hours or passenger restriction.

  4. Drivers ages 20 to 24 or 25 to 29 years did not experience similar reductions in fatal crash involvement rates in the State-quarters with GDL programs compared to State-quarters without GDL programs. This absence of an observed effect on drivers not exposed to GDL increases confidence that the reductions observed in 16-year-old fatal crashes are attributable to GDL.

Conclusions

The most comprehensive GDL programs are associated with fatal crash involvement rates for 16-year-old drivers that are about 20 percent lower than programs without any of the seven GDL components. Based on existing programs that were sufficiently common for analysis, the greatest benefit appears to be associated with programs that include age requirements and:

  • a waiting period of at least three months before the intermediate stage,
  • a restriction on nighttime driving, and either
  • 30 or more hours of supervised driving, or
  • a restriction on carrying passengers.