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Spring 2005

Safety implications of ATIS use with cell phones

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Inappropriate cell phone use by drivers can be as dangerous as intoxication, new research suggests.

Study shows cell phones may impair drivers more than being drunk

Using a cell phone may impair drivers more than alcohol intoxication, according to a new study by University researchers.

Nic Ward, director of the University's HumanFIRST Program and principal investigator for the project, described his findings in February during a CTS Transportation Safety and Traffic Flow Council meeting. The presentation, titled "Design and Safety Implications for ATIS Use with Cell Phones," was part of the CTS Research Seminar Series for students, faculty, and practitioners (see CTS Seminars) about transportation research at the University of Minnesota.

"The drunk driver doing nothing was less impaired than the same person on a cell phone or playing with the radio," Ward said, describing details of the study. Researchers gathered data from test subjects outfitted with a device to measure brain activity and using the Virtual Environment for Surface Transportation Research (VESTR) driving simulator in the HumanFIRST lab. Half of the test subjects drank vodka with cranberry juice to near intoxicating levels (just under .08 blood-alcohol content) as measured with a Breathalyzer.

Because evidence suggests that cell-phone use while driving may be a significant risk factor in traffic crashes, some states have responded by imposing restrictions on the use of hand-held phones. But Ward's research team, citing research that shows hands-free use is no safer than hand-held, has focused instead on the cognitive aspect of talking on a cell phone while driving. "It's actually the conversational component of operating a cell phone while driving that is the culprit," Ward said, "not just the physical manipulation of the phone."

In particular, the two-part study is probing the risks of using cell phones to access new advanced traveler-information systems (ATIS) recently introduced in many states (e.g., 511 Traveler Information Services). Phase I of the study examined how the performance impairment from cell-phone use compares to other types of impairment risks, such as driving while intoxicated (.08 blood-alcohol content) and while operating common in-vehicle controls like a radio, fan, or air conditioning. For the first time, researchers also examined the combined effects of being distracted and being intoxicated, given that many crashes result from a combination of risk factors. Phase II will look at how impairment from 511 interactions compares to other types of cell-phone use, such as conversation.

Ward explained that use of a cell phone and other typical in-vehicle tasks are considered secondary to the primary tasks of driving and driving safely. Previous studies have shown that the increased mental demand of cell-phone use causes impairment—and an increased crash risk. By Ward's definition, impairment means exceeding the limit of one's ability to apply the necessary resources toward a particular task. When that task is driving, impairment may, for example, cause speed inconsistency and slower reaction toward unexpected events. "The brain is dulled because of the secondary task," Ward said.

In measuring driver distraction, Ward drew a distinction between episodic and continuous driving tasks and their effects—when combined with secondary tasks—on a driver's "workload" and ability to drive safely. Continuous driving tasks, he said, make it easier to see impairments in driving due to secondary tasks. Specifically, hands-free cell-phone conversations demonstrated significant impairment. But in-vehicle tasks consistently showed the most impairment because they combine both cognitive and physical distraction.

"Banning cell phones isn't the solution," he concluded. "It's the appropriate use of cell phones."

The cell-phone use study also included the work of HumanFIRST research scientist Mick Rakauskas, along with Ed Bernat, Meredith Cadwallader, and Professor Chris Patrick of the psychology department. The research was sponsored by Minnesota Guidestar and the ITS Institute.

More information about this research may be found online at www.cts.umn.edu/Research/ProjectDetail.html?id=2003040.

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