Teens may begin their driving habits with great caution, but as months behind the wheel pass, they begin to multi-task at higher frequency rates - dialing cell phones, eating, and talking to passengers, etc. - and therefore greatly raise their risk of crashes and/or near-crash incidents.
These findings from a study conducted by the Virginia Tech Transportation Institute and the National Institutes of Child Health and Human Development appear in the Jan. 2 issue of the New England Journal of Medicine.
"Novice drivers are more likely to engage in high-risk secondary tasks more frequently over time as they became more comfortable with driving," said Charlie Klauer, group leader for teen risk and injury prevention at the transportation institute's Center for Vulnerable Road User Safety and first author of the article. "The increasingly high rates of secondary task engagement among newly licensed novice drivers in our study are worrisome as this appears to be an important contributing factor to crashes or near-crashes."
Traffic studies site that drivers from 15 years to 20 years of age represent 6.4 percent of all motorists on the road, but account for 11.4 percent of fatalities and 14 percent of police-reported crashes resulting in injuries.
Interaction with cell phones and other handheld electronic devices have garnered the most public and media interest, but even the simplest distractions can put a young driver at risk.
In the New England Journal of Medicine study, titled "Distracted Driving and Risk of Crashes Among Novice and Experienced Drivers," Klauer and her research team found that likely dangerous distractions for new drivers - versus experienced motorists - include handling of a cell phone to dial or text, reaching away from the steering wheel, looking at something alongside the road, and eating.. All these acts were statistically significant as a distraction for the new drivers.
"Any secondary task that takes the novice driver's eyes off the road increases risk," said Klauer. "A distracted driver is unable to recognize and respond to road hazards, such as the abrupt slowing of a lead vehicle or the sudden entrance of a vehicle, pedestrian, or object onto the forward roadway."
Klauer and her team compared the results of a one-year, 100-car study with drivers between 18 and 72 years of age with an average of 20 years' experience and an 18-month study of 42 teens who had drivers' licenses for less than three weeks when the study began.
Participants from both studies drove vehicles outfitted with the same data acquisition systems developed at the Virginia Tech Transportation Institute, including a minimum of four cameras and a suite of sensors which collected continuous video and driving performance data for the duration of both studies.
Data coders at the institute then watched the video recordings of the drivers and noted any presence of distracting secondary tasks before or during an instance of a crash or near-crash. Many participants from both studies were involved in multiple crash/near-crash events, said Klauer.
A secondary task was considered a contributing factor to any crash or near-crash event if it occurred within five seconds prior to or within one second after the event. A crash was defined as any physical contact between the study participant's vehicle and another object, where the driver was at fault. A near-crash included any maneuver that required the driver to quickly maneuver the vehicle to avoid a crash.
The data revealed that compared to experienced drivers, novice drivers engaged in secondary tasks less frequently during the first six months. However, they matched experienced drivers between months seven and 15, and were engaged in non-driving tasks more often than experienced drivers during months 16 through 18 - a two-fold increase in risky distractions during the last three months of the study.
"Many states have adopted graduated driver licensing provisions that limit cell phone use," said Tom Dingus, director of the Virginia Tech Transportation Institute and a co-author on the New England Journal of Medicine paper. "However, it is not the only risky behavior for novices. Our analyses separated talking and dialing tasks and found that talking on a phone did not increase crash risk among experienced or novice drivers, while dialing increased risk for both groups."
Combining crashes and near-crashes in odds ratio calculations produces conservative point estimates with tighter confidence intervals than when using crashes alone, said Feng Guo, an assistant professor of statistics affiliated with the Virginia Tech Transportation Institute and a co-author of the study.
"The true risk is probably higher than indicated," added Guo.
Added Klauer, "Newly licensed novice drivers are of course at a particularly high crash risk, in part because driving is a complicated task and novices tend to make more mistakes when learning a new task."
"In previous studies we found that crash or near-crash rates among the novice drivers were nearly four times higher than for experienced drivers," she said. "Therefore, it should not be surprising that secondary task engagement contributes to this heightened risk among novice drivers."
Additional authors include Bruce G. Simons-Morton, a senior investigator with the National Institutes of Child Health and Human Development, which sponsored the research; Marie Claude Ouimet, an assistant professor at the University of Sherbrook in Montreal; and Suzie E. Lee, a research scientist at the Virginia Tech Transportation Institute.
Added Simons-Morton of the National Institute of Child Health, "This study is first report of its kind to objectively assess the degree to which engagement in tasks other than driving contributes to novice drivers' crashes and near-crashes, and to compare the results to the impact of such distractions on more veteran drivers."
The publication of a traffic-related study in the New England Journal of Medicine is a natural fit, said Klauer. "We are working on preventing the leading cause of death in people under 35 years old, crashes," she added. "We're working toward the same goals as a medical research institute, but along a different pathway."