Drivers are far more distracted by talking on a cellular phone than by conversing with a passenger in an automobile. That's a conclusion of a new study by University of Utah psychologists. The study, which used a sophisticated driving simulator, found that drivers on cell phones drift out of their lanes and miss exits more frequently than drivers talking with someone in the car. The findings were published in the December 15 issue of the Journal of Experimental Psychology: Applied.

"The passenger adds a second set of eyes, and helps the driver navigate and reminds them where to go," said co-author David Strayer. Previous studies by the Utah scientists found that hands-free phones were just as distracting as hand-held models because the conversation is the biggest distraction. They conclude that drivers talking on cell phones are as impaired as those with the 0.08 percent blood-alcohol level that defines drunk driving in most states.