NICHD research identifies key factors that make car accidents so deadly for teens and helps inform laws that keep teens safe
Imagine a 17-year-old male getting into the driver's seat of a car. Seat belt buckled? Check. Lights on? Check. Mirrors adjusted? Check.
In addition to those standard safety items, though, he has a few other items on his mental checklist. iPod plugged in? Check. Phone handy? Check. He puts the car into gear and heads out to pick up some friends.
What he doesn't realize is that his risk factors for an accident have instantly multiplied by bringing his iPod and phone along. When his friends get in the car, his risk of having an accident will increase even more.
Because driving is new to teens—and distractions are numerous—these drivers are more vulnerable to accidents and injuries than are drivers at any other age. We know this inexperience can harm them: Every day in the United States, about eight teens will die in a motor-vehicle accident. In fact, car accidents are the leading cause of death and disability for adolescents.
Changes over time
So what causes teens to crash more often? And have there been changes in what causes teens to crash over time? (Short answer: Yes!) In an effort to reduce risky driving behavior, NICHD researchers have looked at young drivers' conduct for more than a decade. Early studies focused on parental involvement, the effectiveness of driver education classes, age, sex, and ability to assess risk. When looking at those earlier studies, we can see that risk factors change over time. For example, in 1996, young females were less likely to be in an alcohol-related crash than today. Knowing that risk factors for teen crashes change over time can help researchers, parents, teachers, and others help teens be safer drivers by adjusting rules and safe driving messages.
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More recently, some of the most notable studies performed by the Prevention Research Branch (PRB) of the Division of Intramural Population Health Research at the NICHD looked at the effects of passengers on teen driving behavior. For example, in one study, investigators watched cars leaving high school parking lots. They looked at the speed and likelihood of tailgating of cars with teen drivers and passengers compared with older drivers. And guess what? The teenage drivers drove faster and closer to the leading vehicle. If a male was riding in the car as a passenger, the driver drove even faster and closer to the vehicle ahead. In contrast, when a female passenger was in the car, the risk for speeding and tailgating was lessened.
In another study, researchers looked at the effect of the age and sex of passengers on fatal accident risk. Data from the Fatal Accident Reporting System and the National Household Travel Survey were used to consider how and if teen driving performance is affected by different types of passengers. For instance, does it matter if a passenger is male or female? Are male drivers more likely to speed when other male passengers come along for a ride? Initial results show that fatal crash risk goes up when other teens ride in a car with a teen driver, especially with male teenage drivers. Thus, insisting that teens drive alone until they gain experience may prevent deaths. As a result of this and other passenger-related studies, many states now forbid teen drivers from having teen friends in the car for a certain period of time after earning a license.
Another study currently in progress looks at whether teen drivers are affected by the personalities of their passengers. Drivers are randomly assigned to carry either a risk-accepting passenger or a risk-averse passenger. The questions are, can driving a cautious passenger make a male teen driver more careful? Can a risk-accepting passenger encourage a driver to drive faster, despite the driver's own natural inclination? Results from this study are still pending.
Research shows that if parents (or maybe even electronic monitoring systems) metaphorically look over a teen driver's shoulder, he or she will drive more safely. Parents are particularly effective in this role. Their presence usually leads to more careful behaviors in the car.
How do we know this? Well, for the first time, researchers looked at teen driving skills in vehicles equipped with special instruments. Forty newly licensed teens drove vehicles equipped with cameras, motion sensors, Global Positioning System (GPS), lane trackers, and other tools so researchers could gauge their driving performance during their first 18 months of driving. The results showed that crashes, near-crashes, and elevated gravitational-force (g-force) events (like fast stops and tight turns) were many times more frequent among teenage drivers than among their parents. The study also revealed that teenagers are more likely to have high g-force events when driving alone or with peers. However, if a parent was riding along in the car, the likelihood of a high g-force event decreased.
High g-force events, which are changes in acceleration due to late braking, fast starts, and sharp turns, are dangerous because they can increase the potential for a driver to lose control of the vehicle. They also reduce the time available for drivers to respond to hazards and for other persons on the road to respond to a driver's actions.
What about teen drivers whose parents actively supervise their driving practice? Do these teen drivers perform better when they drive independently? Researchers are examining this question. Whether or not parent-supervised practice driving improves teen driving skills is not clear. To investigate this matter, the researchers loaded the vehicles of 90 families with GPS, accelerometers, cameras, and other equipment during the learner's permit period and the first six months of independent driving. This study will offer the best data yet available on the value of parent-supervised driving practice. It will also allow researchers to look at the effects of the amount of pre-licensed driving on independent driving performance.
Parents can't always ride with their teen driver, however. It's just not practical. Could electronic monitoring make teens drive safely in the absence of a parent? Another study looks at the willingness of families with newly licensed teen drivers to use cameras to monitor the new driver's behavior. These cameras record video footage within three seconds of certain g-force events. This study will provide information on whether use of these cameras is a practical way to monitor teen driving and offer constructive feedback on driving performance. Results are pending.
Keeping Young Drivers Safe
Because of the research happening today at NICHD, teens can be safer behind the wheel. We now know that distracted driving leads to greater crash risk, so parents can insist that phones and other electronic devices not be used while driving. Of course, teens aren't hearing these messages just at home. Distracted driving laws are taking effect throughout the country. For example, 32 states and the District of Columbia ban all cell phone use by novice drivers. And 39 states, the District of Columbia, Guam, and the Virgin Islands ban text messaging for all drivers.
Also, it's important to note that many of the findings from NICHD studies are reflected in the limits placed on teens through graduated licensing programs. These programs—in which privileges are granted to new drivers in phases—are in effect in all 50 states and the District of Columbia.
Graduated licensing programs generally require new drivers to complete three phases before they receive a license. The first stage is a learner's permit, in which the new driver must practice driving with a licensed driver aged 21 years or older. The second stage allows driving alone, but only under certain conditions—for example, not late at night, and not with teen passengers in the car. After completing these phases, the driver receives a full license. In some states, this comes only after reaching age 18.
According to three studies, these programs dramatically reduce the rate of fatal teen driver crashes. The NIH-supported research effort showed that such programs reduced the rate of fatal crashes among 16- and 17-year-olds by 8% to 14%. In addition, limiting driving at night or with teenaged passengers, in combination with graduated licensing laws, produced greater reductions in overall crash rates involving teen drivers than graduated licensing laws alone.
"Our research has encouraged the strengthening of graduated driver licensing policies, particularly restrictions on teenage passengers and using cell phones while driving," said Dr. Bruce Simons-Morton, Senior Investigator and Chief, Prevention Research Branch at DIPHR. "One of the effects of more strict graduated driver licensing policies has been an increased amount of supervised practice driving required before teens can test for a license."
Driving practice and experience should make teens safer drivers as they age. In the meanwhile, studies like these provide evidence that informs laws to help keep teens safe when they are behind the wheel.