Young drivers have collision claim frequencies per insured driver approximately double those of drivers ages 35-55. To reduce the high collision rates among young drivers, many states have adopted graduated driver licensing (GDL) programs. GDL is designed to delay full licensing while allowing beginning drivers to gain experience under lower risk conditions. This study evaluates how the strength of state GDL provisions affect collision claim frequencies of young drivers and the effect on collision claim frequencies of individual GDL components. State GDL laws have been rated as good, fair, marginal, or poor by the Insurance Institute for Highway Safety (IIHS) based on the number and strength of provisions in the individual components. From Poisson regression analyses, the estimated collision claim frequency of rated drivers age 16 was 22 percent lower for GDL laws rated good compared with laws rated poor. Claim frequencies were 17 percent lower for laws rated fair and 11 percent lower for laws rated marginal, compared with laws rated poor for drivers age 16. The effect of GDL decreased as rated driver age increased. For rated drivers age 19, claim frequencies were 9 percent lower for laws rated good than for laws rated poor. Collision claim frequencies of rated drivers ages 16-17 were modeled using the GDL components of permit age, required holding period, required practice hours, licensing age, passenger restrictions, and nighttime driving restrictions. Restricting the number of passengers to one or fewer reduced claim frequencies 6 percent, restricting driving after 9 p.m. reduced frequencies 11 percent, and increasing required practice driving by 20 hours reduced frequencies 4 percent. Permit age and licensing age were not significant at the 0.05 level, but the model estimated a 3 percent reduction in claim frequencies for increasing the permit age by 1 year and a 7 percent reduction for increasing the licensing age by 1 year. When combined with the other GDL components, lengthening the permit holding period proved counterproductive, with a slight increase in claim frequencies (2 percent increase for lengthening the permit holding period by 3 months). This report was done in parallel with an IIHS study evaluating the effect of GDL on the fatal crash involvements of young drivers (McCartt et al., 2009). The IIHS study found similar reductions in losses for both the strength of GDL laws and the strength of GDL components. Compared with laws rated poor, the fatal crash rate for drivers ages 15-17 was 30 percent lower for laws rated good and 11 percent lower for laws rated fair. Specific GDL components were estimated to have large reductions in fatal crash rates for drivers ages 15-17. Delaying the licensing age by 1 year had a 13 percent reduction in the fatal crash involvement rate for drivers ages 15-17, restricting driving after 10 p.m. had a 16 percent reduction, not allowing teenage passengers had a 21 percent reduction, and delaying the permit age by 1 year had a 13 percent reduction. Lengthening the permit holding period and increasing required practice driving had little effect on fatal crash involvement rates. (Author/publisher)
Samenvatting