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December 1, 2008

Cell Phones Distract Drivers More Than Passengers

U.S. researchers have found that drivers are far more distracted by talking on their cell phones than having a conversation with passengers, and hands-free devices don't seem to offer any added benefits.

Using a series of driving simulations, Dave Strayer of the University of Utah and colleagues found that chatting on a mobile phone can slow the reaction times of young adult drivers to levels seen among senior citizens, and shown that drivers using mobile telephones are as impaired as drivers who are legally drunk.

Researchers studied a total of 96 adults aged 18 to 49.

Researchers used three experimental conditions - conversation with hands-free cell phone, conversation in the car, or no conversation.

Participants drove under an irregular-flow condition that mimics real highway conditions -- with other vehicles, in compliance with traffic laws, changing lanes and speeds.

When drivers were talking to someone on a cell phone, their partners were at another location, while partners sat next to the drivers during the in-car conversation.

Drivers who were talking on their cell phones tended to miss their exits, while in-car conversation partners were actually helpful in directing drivers.

"The passenger adds a second set of eyes, and helps the driver navigate and reminds them where to go," said Strayer.

"When you take a look at the data, it turns out that a driver conversing with a passenger is not as impaired a driver talking on a cell phone."

Findings are being released in December issue of the Journal of Experimental Psychology: Applied.

Conversation analyses revealed some interesting patterns, according to the researchers. When driving tasks got more complicated, drivers appeared to modulate the complexity of their speech, as measured by syllables-per-word.

"The difference between a cell phone conversation and passenger conversation is due to the fact that the passenger is in the vehicle and knows what the traffic conditions are like, and they help the driver by reminding them of where to take an exit and pointing out hazards," Strayer said.

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Image 2: University of Utah psychology graduate students Russ Costa and Janelle Seegmiller demonstrate the driver and passenger roles used by participants in a study of how drivers are affected by conversations with passengers versus conversations over a cell phone. The study, which used the sophisticated driving simulator shown in the photo, found that when drivers talk on cell phones, they are more likely to drift out of their lane and miss exits. Credit: Nate Medeiros-Ward

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