Study results support the effectiveness of restricted driver's licenses for teens that limit nighttime driving and the number of passengers in the car, according to the American Automobile Association Foundation for Traffic Safety.

According to the foundation, death and injury crash rates for 16-year-old drivers are 20 percent lower in states with "graduated" driver's licensing laws.

Washington's graduated driver's licensing law includes both nighttime and passenger restrictions, and since its implementation in July 2001, collisions involving 16-year-old drivers on Washington highways dropped 45 percent.

The study found three components to be differentiating factors between crash-free and crash-involved teen drivers: overall compliance with graduated driver's licensing laws; adherence to traffic laws; and parental involvement.

"Teens who obey traffic rules, follow graduated driver's licensing restrictions, and have actively involved parents are much less likely to crash," said Janet Ray, for AAA Washington. "Washington has a strong graduated driver's licensing law with appropriate restrictions. To further reduce teen crashes in our state, we need teens to follow the rules more closely and increase parental involvement, especially as we head into the summer months."

The study found that compliance with passenger restrictions was especially problematic and teens involved in crashes were more likely than crash-free teens to report more frequent violations. For example, 30 percent of crash-free teens, but only 16 percent of crash-involved teens, reported never violating passenger restrictions during their first six months in the intermediate stage of graduated driver's licensing, and nearly half of crash-involved teens reported violating the passenger restriction "more than a few times."

Thirty-three percent of crash-involved teens reported receiving a ticket, as compared to only 13 percent of crash-free teens. Also, teens who had not been involved in crashes reported higher levels of parental monitoring, relative to their counterparts who had been involved in crashes.