If you drive a car, almost certainly you've been driven to distraction by other drivers; chances are good, however, that you've also been driving to distraction. For instance, you're behind the wheel and cruising along when something momentarily diverts your attention from the road ahead. Perhaps kids in the back seat are acting up or you need to change the disk in the CD player, retrieve a tissue from the glove compartment, glance at a map, or respond to a cell phone call. Maybe you’re simply tired after a long day at work and finding it difficult to concentrate.

These examples are readily identified as visual distractions because your eyes are momentarily diverted from the road ahead. Many drivers tend to believe that such visual distractions are the cause of most traffic accidents. But a recent study conducted by the Virginia Tech Transportation Institute (VTTI) concludes that mental attention--really thinking about what you're doing, focusing your mind on the task at hand, and anticipating what may occur--is every bit as important as simply keeping your eyes on the road when you're behind the wheel.

Sponsored by the National Highway Traffic Safety Administration (NHTSA), Virginia Department of Transportation, Virginia Transportation Research Council, and Virginia Tech, the "100-Car Naturalistic Driving Study" attracted extensive national media attention when its results were released. The research project involved equipping 100 privately owned cars in the Northern Virginia/Washington, D.C., area with sophisticated monitoring equipment to record the actions of drivers over a period of about one year. Altogether, a total of 241 drivers (primary and secondary drivers) logged some 2 million miles in 42,000 hours of driving.

Virginia Tech Magazine contacted VTTI Director Thomas A. Dingus, the project's manager, to learn more about his perspective on the study results and how they can help drivers be safer on the road.

"ACCIDENTS" OR TIRED, INATTENTIVE DRIVERS?

One of the most important findings of the study is the substantial effect fatigue has on automobile crashes. "Fatigue--which is a different type of inattention than distraction--is the most dangerous type of driver inattention and is a contributing factor in 12.3 percent of crashes nationwide," says Dingus. "Drivers who are moderately to severely fatigued increase their crash risk 4.7 times than when they are engaged in normal, attentive driving. I would definitely have to say that mental fatigue is the most dangerous and prevalent type of driver-related distraction."

The study demonstrates, however, that fatigue is not the sole contributor to auto crashes. "There are, of course, other kinds of distractions that lead to accidents," Dingus explains. "We found that the most common distractions included dialing a cell phone, cell phone talking and listening, reading, eating, applying makeup, reaching for either a moving or a non-moving object, and taking a long glance at some specific external object." In general, the findings support the supposition that the longer the distraction, the more compromised the driver's ability to anticipate a possible event and to react in time to avoid trouble.

For instance, the results indicate that "in 93 percent of all rear-end crashes, the driver looked away from the roadway ahead at least once within five seconds of the onset of the conflict," Dingus notes. "However, in all of these cases, there was at least a two-second headway between the subject vehicle and the vehicle in front of our driver. What this suggests is that many crashes occur because drivers did not anticipate the actions or behavior of traffic and were unable to respond to these unanticipated actions in a timely manner. There are many factors that have to occur for an auto accident to take place, but redirecting the driver’s eyes on the forward roadway may be one way to decrease crash rates."

Conversely, Dingus reports that having a passenger in the adjacent seat but not looking at that passenger, as well as normal driving-related glances, such as checking mirrors, gauges, or blind spots, did not contribute to a significant number of crashes and were actually found to have a protective effect. "These type of short glances reduced crash risk by 50 to 90 percent," he says. "The existing hypothesis to explain this effect is that drivers are actively engaged in scanning, so they are more attentive overall, thus reducing crash risk."

THE CELL PHONE PHENOMENON

Some cell phone devotees assert that hands-free phones provide a viable solution to the problems associated with using a cell phone while driving. According to Dingus, "The results gathered in this particular study did not show enough instances of hands-free call phone use for us to draw any real conclusion about their safety or risk."

A separate study conducted by the NHTSA, however, found that while drivers considered hands-free phones easier to use than hand-held devices, "the hands-free phones were more time-consuming to interact with while driving," says Dingus. "Our study was not designed to study cell phone use, per se--it was a crash causation study," Dingus adds. "We are currently conducting further analyses on the subject of cell phone use, but we believe this study is the most representative study of driving behavior that has ever been conducted, and our results will most closely reflect the true risk associated with call phone use and behavior."

WHAT'S DOWN THE ROAD?

Dingus reports that the "100-Car Naturalistic Driving Study" project resulted in over six terabytes of data that can be used for a wide range of additional studies, such as the analysis of collision avoidance algorithms and a more in-depth examination of driver behaviors.

"With the support of appropriate funding, we can complete a variety of studies with the 42,000 hours of pre-crash, normal driving, and crash information data that we already have available," Dingus says. "The NHTSA sponsored the 100-car study, and there are plans to initiate bidding for a much larger version of this research. If VTTI is awarded the contract, the study may include a significantly larger number of cars, cities, vehicle types, and sensors. We still have much to learn, and what we do learn can benefit every individual who gets behind the wheel of a car."