Researchers know that a driver who looks away from the road to retrieve a spilled cup of coffee, dial a phone or change a CD is less likely to see and react to circumstances that can lead to a crash. What has eluded researchers is a way to measure how and to what extent drivers are distracted.

To answer this question, researchers conducting a four-year, $4-million study with major funding by the U.S. Department of Transportation through the National Highway Traffic Safety Administration evaluated how drivers balance their attention between the road and other activities such as tuning the radio, listening to books on tape, dialing a hand-held cell phone and entering a destination into a navigation system. The results will help researchers and auto industry engineers determine how multi-tasking while driving affects driver attention and performance.

The results also will provide automakers with tools that can help them design vehicle technologies that do not overly distract drivers.

The study was conducted by the Crash Avoidance Metrics Partnership - Driver Workload Metrics Project (CAMP-DWM), which brought together Ford, General Motors, Nissan Technical Center North America and Toyota Technical Center USA with the National Highway Traffic Safety Administration.

Historically, measuring driver distraction and developing ways to address it have been difficult because there are different types of distracting behaviors: from visual and manual activities such as reading a paper map or eating, which take drivers' eyes off the road and hands off the wheel; to behaviors that can take a driver's mind off the road, such as being involved in a cell phone conversation or daydreaming.

The CAMP-DWM research showed that visual and manual tasks cause far more eye glances away from the road than tasks such as listening to a book on tape or voice-guided navigation. Furthermore, CAMP test subjects who took their eyes off the road had a greater chance of missing an event that could lead to a crash, such as the driver ahead suddenly braking.

"Today's drivers face competing demands for their attention," said Dr. Linda S. Angell, one of the CAMP-DWM researchers and a General Motors Corp. Technical Fellow. "We also know that many drivers are increasingly technology- dependent. We want to help ensure that vehicle technologies are not distracting drivers from what should be their first priority: keeping their eyes and their minds on driving. This work is going to provide us with tools to better measure distraction."

The CAMP-DWM research measured driver performance using 22 conventional, experimental and advanced technology in-vehicle tasks. Data were collected in the laboratory, on a test track and on interstate highways. While drivers performed these tasks as they drove, researchers measured such things as eye glances away from the road, lane positioning and the number of lane crosses; speed maintenance; and the percentage of missed events (such as not seeing a car braking ahead) and response times.

"We were able to correlate laboratory workload metrics with the driving performance data collected in the CAMP-DWM project to establish their meaningfulness," said Dr. Louis Tijerina, a member of the CAMP-DWM project team and a Senior Technical Specialist at Ford Motor Co. "Studies often collect laboratory data without further testing in a real driving environment to examine the validity of the lab results."

The study used 234 licensed drivers - a balance of men and women - between the ages of 21 and 79. In each venue, the drivers performed tasks under a variety of experimental conditions. In addition, a two-minute segment of just driving was performed under the same conditions for comparison purposes.

In the on-road and test track studies, participants drove an instrumented car between two other vehicles while performing the tasks. Researchers measured a driver's ability to recognize that the lead vehicle was slowing down, or that its center high-mounted stoplight (CHMSL) had come on, or that the following vehicle was activating a turn signal. Instruments inside the test subject's vehicle recorded vehicle control data such as keeping in the lane, maintaining a given speed, eye glance patterns and responses to event- detection scenarios.

The CAMP-DWM report concludes that no single measurement tool captures the effects of distraction - or workload - on driver performance. The research also highlights the need to correlate laboratory results with on-road, real- world data to truly assess how driving performance is affected by multi- tasking behind the wheel.

The CAMP findings also support the voluntary industry guidelines developed in 2002 and revised in 2003 and 2006 by the Alliance of Automobile Manufacturers to address vehicle technologies and their effects on driver distraction.