NIH-funded studies show limits on night driving, teen passengers, further reduces deaths
Friday, November 4, 2011
Programs that grant privileges to new drivers in phases—known as graduated licensing programs—dramatically reduce the rate of teen driver fatal crashes, according to three studies funded by the National Institutes of Health.
Such graduated licensing laws were adopted by all 50 states and the District of Columbia between 1996 and 2011. The NIH-supported research effort shows that such programs reduced the rate of fatal crashes among 16- 17-year-olds by 8 to 14 percent.
Reductions in fatal crashes were greatest in states that had enacted other restrictions on young drivers. The greatest reductions in young driver crashes were seen in states that had adopted graduated driver licensing laws in combination with mandatory seat belt laws or laws requiring a loss of the driver’s license as a penalty for possession or use of alcohol by youth aged 20 or younger.
In addition, limiting driving at night or with teenaged passengers, in combination with graduated licensing laws, had greater reductions in overall crash rates involving teen drivers than graduated licensing laws alone.
Graduated licensing programs generally require new drivers to complete three phases before they receive their license. The first stage involves issuing a learner’s permit, in which the new driver must practice driving with a licensed driver aged 21 or older. The second stage allows driving, but only under certain conditions— for example, not late at night, and without teen passengers in the car. After completing these phases, the driver receives a full license—in some states, after reaching age 18.
One of the studies, an analysis of 15- to 17-year-old drivers killed in crashes between 1999 and 2008, concluded that the effect of these laws did not appear to be uniform across racial and ethnic groups. The laws did not appear to reduce fatalities among Hispanic teen drivers, although they did have an effect among white, African-American and Asian teenagers.
“Everyone hoped that that graduated driver licensing would help to protect new drivers, but it was necessary to evaluate whether the new laws did indeed have their desired effects.” said Rebecca L. Clark, Ph.D., chief of the Demographic and Behavioral Sciences branch of the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), which funded the studies. “These studies not only confirm the effectiveness of graduated licensing approach, they also identify additional protective factors.”
The studies were conducted by James C. Fell and colleagues at the Pacific Institute for Research and Evaluation (PIRE) in Calverton, Md. Fell was the first author on a study analyzing effect of graduated licensing laws in the United States, which he undertook with PIRE colleagues Kristina Jones, Eduardo Romano, Ph.D., and Robert Voas, Ph.D. Their findings appear in Traffic Injury Prevention. In a study published in the Journal of Safety Research, Fell, Michael Todd, and Dr. Voas looked at the effects of licensing restrictions in the graduated driver licensing laws. Dr. Romano, Fell and Dr. Voas collaborated on the study of race and ethnicity and graduated licensing laws, which appears in the Annals of Advances in Automotive Medicine.
For all three studies, the researchers analyzed data from a national database of information about fatal crashes maintained by the National Highway Traffic Safety Administration.
Using data from 1990 to 2007, the researchers compared the rate of fatal crashes among two groups of drivers: 16- and 17-year-olds and 21- to 25-year-olds. They then tracked how this ratio changed after graduated licensing laws were adopted in each state. Their analysis showed that characteristics of a state’s licensing law influenced the law’s effectiveness. The most effective legislation had at least five of seven key elements:
- A minimum age of 16 for a learner’s permit
- A mandatory waiting period of at least six months before a driver with a learner’s permit can apply for a provisional license
- A requirement for 50 to 100 hours of supervised driving
- A minimum age of 17 for a provisional license
- Restrictions on driving at night
- A limit on the number of teenage passengers allowed in the car
- A minimum age of 18 for a full license
The researchers also looked at the effect of nighttime and passenger restrictions on fatal crash rates. As a result of their analysis, they estimated that laws restricting driving at night reduced fatal crashes at night among 16- and 17-year-old drivers by 10 percent in comparison to states that did not have nighttime driving restrictions. Nighttime restrictions also reduced involvement in nighttime crashes among16-and 17-year-old drinking drivers by an estimated 13 percent. Laws that established a midnight curfew for provisional drivers appeared to be most effective at reducing nighttime crashes, the researchers concluded. In addition, laws restricting the number of teen passengers in a car driven by a 16- or 17-year-old appeared to reduce fatal crashes with teen passengers by 9 percent.
“States have followed a variety of approaches to their legislation about graduated driver licensing laws,” said Fell. “These findings on nighttime and passenger restrictions might be useful to states wishing to make their graduated licensing programs more effective.”
In a separate analysis, the researchers compared data from the years in which individual states had these laws in effect to the total sample, spanning the period from 1999 to 2008. In addition, the researchers evaluated crashes in which speed or alcohol was a contributing factor.
The researchers found that the rate of 15- to 17-year-old drivers killed in single vehicle crashes dropped after states adopted graduated licensing laws. In particular, they concluded that these laws were more effective at reducing alcohol-related fatalities than those in which speed was a factor.
About the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
The NICHD sponsors research on development, before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. For more information, visit the Institute’s Web site at http://www.nichd.nih.gov/.
About the National Institutes of Health (NIH)
NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit http://www.nih.gov.