V. CONCLUSION

GDL programs as a whole are associated with substantially lower fatal crash involvement rates for 16-year-old drivers. The most comprehensive programs appeared to be associated with the greatest benefit. That benefit amounted to about a 20-percent-lower fatal crash involvement rate, (comparing State-quarters having comprehensive GDL programs to those without GDL programs), and it suggests that effective GDL programs need to be comprehensive.

Among existing programs that were sufficiently common for analysis, significantly lower fatal crash involvement rates for 16-year old drivers were associated with programs having five or more components, including 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.

Public health agencies, members of the public, and physicians can play a useful role by working to achieve comprehensive GDL programs and encouraging parents of beginning drivers to enforce GDL requirements.