Researcher Remarks

Distractions in Everyday Driving
AAA Foundation for Traffic Safety Press Conference
Washington, D.C. August 6, 2003

Jane Stutts, Ph.D.
Principal Investigator

The National Highway Traffic Safety Administration estimates that 25% or more of the crashes occurring on our highways are caused by distracted or inattentive drivers.

In the late summer of 1999, the AAA FTS funded a study to learn more about the role of driver distraction in traffic crashes. The study was conducted in two phases.

In Phase I of the study we analyzed 5 years of national crash data to identify the major sources of distraction contributing to crashes, and the specific circumstances of these crashes – what type of roadway they occurred on, whether they occurred more or less often at nighttime, what age drivers were most involved. We also examined the narrative descriptions of the crashes provided by the police officers who investigated them, for further insight to the problem.

In Phase II of the study, the results of which are being released today, the goal was to measure the frequency of occurrence of these various distractions in people’s everyday driving. We also sought to measure the consequences of the distractions on driving performance.

One of the biggest challenges to the project was developing the equipment and methodology for capturing this information. The system we developed consisted of a small camera unit about the size of a VHS tape that contained three miniature video cameras along with a microphone. The unit was attached to the inside front windshield of our volunteer subject’s car, just below the rear view mirror. Cables connected the camera unit to a larger box that we placed in the trunk of the car. Here we had a VCR recorder and a custom battery pack that was able to power the cameras for up to 10 hours. A separate trigger cable was connected to an accessory fuse, and turned the unit on when the vehicle was started.

The equipment was installed in the vehicles of 70 volunteer subjects, half recruited from the Chapel Hill, NC area where I work, and half from the Philadelphia area where our collaborator on the project was located. There were equal numbers of males and females spanning the ages of 18-80. The equipment took about half an hour to install, and then remained in the subjects’ vehicle for one week while they went about their everyday driving. Subjects were not told that we were studying driver distraction, but only that we were studying how drivers respond to various traffic and roadway conditions.

The resulting videotapes containing three separate, side by side pictures – a closeup view of the driver’s face, a wider view of the interior of the vehicle, and also a view out the front of the vehicle, so that we could see what the driver was seeing at the time.

We then coded this data, very meticulously, for computer analysis. We coded each potential distraction – talking on cell phones, eating or drinking, reaching for something inside the vehicle, adjusting the radio, even talking with passengers. We also coded a number of variables to describe the driving context – whether the vehicle was stopped or moving, the type of roadway, the level of traffic on the roadway, and such. Finally, we identified three potential consequences that might affect driving safety – whether the driver had both hands, one hand, or no hands on the steering wheel; whether the driver’s eyes were directed inside or outside the vehicle; and whether the vehicle was wandering in the travel lane, crossing over a lane line, or having to brake suddenly.

A total of 207 hours of videotaped data were coded, or about 3 hours for each of our 70 subjects.

So what did we learn?

First, we learned that distractions are a very common component of everyday driving. Our 70 drivers were engaged in some form of potentially distracting activity up to 16% of the time they were driving, not including any conversations they may have had with passengers. And while the oldest drivers in our sample were generally less likely to engage in activities that might interfere with their driving, no age group was immune to the problem.

Also, we learned that there are many things that distract drivers. Although cell phones are frequently in the news, our study showed that drivers spend as much time manipulating their radio controls, eating or drinking, reaching for things inside their vehicle, or attending to events outside their vehicle, sometimes referred to as “rubbernecking.”

While not all of our drivers carried passengers in their vehicle, passengers certainly could be a source of distraction, especially babies and young children. On an hourly basis, adult passengers distracted the driver on 1.1 occasions. For children, this number increased to 4.5, and for babies, it was 8.4 distractions per hour of driving.

We also collected some interesting descriptive data on these various distractions. For example, it took our 28 cell phone users an average of 13 seconds to dial a cell phone, 8 seconds to answer a ringing phone, and each conversation averaged about 1 ½ minutes. It also took 4 seconds, on average, to light a cigarette, and 5-6 seconds to change the radio station or insert a CD or tape. Drivers manipulated their audio systems about 8 times per hour of driving. We hope that this real-world driving data will provide a useful baseline for future studies in this important area.

Finally, we were able to look at how these distractions might interfere with safe driving. Here, we focused on our three outcome measures: where the driver’s eyes were focused, whether their hands were on the steering wheel, and whether their vehicle was swerving in the travel lane. All of these analyses were carried out only when the driver’s car was moving.

When drivers were reading or writing, their eyes were focused inside 92% of the time; when they were dialing or answering a cell phone, they were looking inside 68% of the time. When engaged in some sort of grooming activity, such as hair combing or applying makeup, their eyes were directed inside, rather than outside, the vehicle 35% of the time, and when they were manipulating music controls about 23% of the time.

Activities that were especially likely to be associated with high rates of driving with no hands on the steering wheel included reading and writing, grooming, manipulating vehicle controls, and dialing a cell phone.

Those associated with the highest rates of swerving or crossing into another lane included reaching for objects inside the vehicle, eating or drinking, dialing or answering cell phones, and distractions by babies.

This was not a perfect study. We would have liked to have had more subjects, driving for longer periods of time. We also experienced challenges in objectively defining some of the distractions and other variables we wanted to measure. In addition, there were important variables that we could not measure at all, such as the cognitive demand associated with each of the distractions. Thus, although we could see from the videotapes where the drivers’ eyes were focused, we could not “get inside that driver’s head,” so to speak, and measure whether they were really paying attention to what was going on out there on the roadway ahead of them. As a result, we cannot draw firm conclusions about which of these potentially distracting activities carries the greatest risk for drivers.

However, given the large numbers of crashes occurring every day due to distracted drivers, I think it is safe to say that we all need to pay more attention to the important task of driving. This study was the first to collect data on real-world driving behavior. We hope it will provide a useful basis for continued research in this important area.