New studies define cell-phone hazards. (Safety Alert).

Cell phones have developed a reputation as a distraction for drivers even though they aren't the only, or even, some say, the principal cause of inattention. Two new studies add perspective to the issue. One, by a leading researcher in the field, helps explain why cell phones might be a problem. Another helps define how often cell-phone use can be singled out as a cause of traffic accidents.

INATTENTION BLINDNESS

Researchers at the University of Utah have shown in several studies that conversations on hands-free phones are just as distracting as those on handheld ones. Their latest study explains why. It involved 110 college students using driving simulators and was published in March in the Journal of Experimental Psychology: Applied.

Cell-phone use leads to what the researchers call "inattention blindness." Talking on a hands-free cell phone while driving made the students "blind" to 50 percent of roadside billboards; that is, they had more trouble remembering which ones they had seen when they had been talking on the phone than when they hadn't. Drivers did see and respond to stop signs and navigation arrows.

The University of Utah study also found that hands-free phone use impaired drivers when simulated highway traffic was heavy, causing rear-end collisions in 3 of 1,280 simulated braking incidents. There were no accidents in simulated light highway traffic.

"Under some situations, driving can become so easy, you may be able to talk on a cell phone and not show any ...