Hands-free phones not safe on road, study shows

In half a dozen states, including California, it is illegal to use a handheld cell phone while driving but legal to talk on a hands-free device.

The theory is that it's distracting to hold a phone and drive with one hand. But a large body of research shows that a hands-free phone poses no less danger than a handheld one – that the problem is not your hands but your brain.

“It's not that your hands aren't on the wheel,” said David Strayer, director of the Applied Cognition Laboratory at the University of Utah and a leading researcher on cell phone safety. “It's that your mind is not on the road.”

Now Strayer's research has gained a potent ally. Yesterday, the National Safety Council, the nonprofit advocacy group that has pushed for seat belt laws and drunken-driving awareness, called for an all-out ban on using cell phones while driving.

“There is a huge misperception with the public that it's OK if they are using a hands-free phone,” said Janet Froetscher, the council's president and chief executive. “It's the same challenge we had with seat belts and drunk driving – we've got to get people thinking the same way about cell phones.”

Lab experiments using simulators, real-world road studies and accident statistics tell the same story: Drivers talking on a cell phone are four times as likely to have an accident as drivers who are not. That's the same level of risk posed by a driver who is drunk.

Why cell phone use behind the wheel is so risky isn't entirely clear, but studies suggest several factors. No matter what the device, phone conversations appear to take a significant toll on attention and visual-processing skills.

It may be that talking on the phone generates mental images that conflict with the spatial processing needed for safe driving. Eye-tracking studies show that while drivers look side to side, cell phone users tend to stare straight ahead.

They may also be distracted to the point that their engaged brains no longer process much of the information that falls on their retinas, which leads to slower reaction times and other driving problems.

At the University of Utah, Strayer and his colleagues use driving simulators to study the effects of cell phone conversations. A simulator's interior looks similar to a Ford Crown Victoria, and a computer allows researchers to control driving conditions. Study participants are asked to drive under a variety of conditions: while talking on a handheld phone or a hands-free one, while chatting with a friend in the next seat, and even after consuming enough alcohol to put them over the legal limit.

While in the simulator, drivers are asked to complete simple tasks, such as driving for several miles and finding a particular exit or navigating streets where they must brake for traffic lights, change lanes and watch for pedestrians. How fast they drive, how well they stay in their lane, driving speed and eye movement are closely monitored.

The researchers have also placed electrodes on participants' scalps to gauge how they process information. Similar studies, using brain imaging, have been done at Carnegie Mellon University.


