Cell use impairs drivers, CMU study says

Just listening to a cell phone conversation cuts a person's ability to concentrate on driving by more than a third, a Carnegie Mellon University neuroscientist told state lawmakers Wednesday.

The House Transportation Committee met Downtown to gather information as it considers several legislative proposals on restricting cell phone use by drivers, particularly teenagers.

Marcel Just, who directs Carnegie Mellon's Center for Cognitive Brain Imaging, showed colorful images of brain activity in a person driving in silence compared with one listening to a cell phone conversation. Activity dedicated to driving decreased by 37 percent when listening.

"As you can see, they're fairly dramatic results," said Just, whose results will be published in an upcoming issue of the scientific journal Brain Research. His study is the first of its kind.

Just had 29 licensed drivers use a computer program and a joy stick to navigate a winding road while blood flow to their brain was monitored by functional magnetic resonance imaging, or fMRI. The drivers listened to a person asking them true or false questions through headphones, meant to simulate a hands-free cell phone.

State Rep. Josh Shapiro, D-Montgomery, has proposed a law banning drivers from using handheld cell phones and pressed Just about whether hands-free phones that use headphones or speakers are better.

Because of limited space in the fMRI machine, Just said, he wasn't able to measure the effect of text-messaging or using a handheld phone. He speculated they would add another distraction and brain activity dedicated to driving would likely further decrease.

"I'd rather the person use hands-free rather than handheld," he said.

Just said talking passengers likely aren't as distracting to drivers as a cell phone conversation because passengers can see when traffic is difficult and stop talking.

The committee also heard testimony from groups including the Center for Automotive Safety Research at the Virginia Tech Transportation Institute and AAA.

Committee Chairman Joe Markosek, D-Monroeville, pointed out that no states have completely banned cell phone use while driving. He said compromises -- such as allowing hands-free devices -- would have to be made to get some restrictions in place.

"We're probably going to fall somewhere in the middle," he said. "It's our goal ... to get some legislation passed."

Simply requiring that studies such as his be presented at driver education classes could convince people not to risk using a cell phone while driving, Just said.