MONTREAL (Reuters Health) - Hands-free technologies may still prevent drivers from keeping their eyes and mind safely on the road while talking on cell phones, researchers report. They found that mental distractions equivalent to engrossing conversation reduced drivers' awareness of the environment around them.

"We were able to do an actual on-road study with real drivers in a typically demanding driver environment," explained Dr. Joanne L. Harbluk, of the Canadian federal agency Transport Canada. She said drivers preoccupied by a hands-free cell phone conversation displayed real "changes in visual behavior and braking performance" while weaving their way through busy city streets.

The findings were presented here Tuesday at the 6th World Conference on Injury Prevention and Control.

Recent concerns about the safety of driving while dialing and talking into handheld cell phones have led some states to ban their use in moving vehicles. In response, millions of cellular users have made the switch to hands-free devices that free up the hands for driving.

But what of the distraction potential of cell phone conversations themselves? In their study, Harbluk's team monitored the driving performance 21 adults as they maneuvered a 1999 Toyota Camry--equipped with a hands-free cell phone--through 8 kilometers of a busy four-lane city roadway.

Drivers were either allowed to complete the course without engaging in a phone conversation, engaging in a conversation in which they were asked to answer mentally "undemanding" questions such as "What is 6 plus 9?" or asked more challenging questions such as "What is 37 plus 24?" The researchers hoped that these types of questions might force drivers to concentrate as they would while in a deep conversation with a friend or business colleague.

Using sophisticated eye-tracking technology, Harbluk's team found that "as the drivers went from the easy condition to the relatively demanding position, from the easy task to the more difficult task, they were actually making fewer (eye checks) as they drove, looking around a bit less, consistent with less exploration of the environment."

Specifically, drivers concentrating on tougher cell phone conversations made fewer checks to the right and left, preferring to keep their eyes in a more narrow zone, straight ahead.

When it came to routine checks of mirrors and in-board instruments such as speedometers, "drivers actually spent less time looking at both of those areas when they were doing a demanding task versus an easy task," Harbluk said. In fact, 7 of the 21 drivers ceased looking into the left-hand mirror altogether during the difficult-question task, she said, while 13 of the 21 drivers ignored the right-hand mirror.

Fewer and more restricted checks of the driving environment may raise risks for unexpected and potentially hazardous events, the researchers note. Their examination of on-board data on "hard braking"--sudden, sharp decelerations--show that as the mental demands of cell phone conversations increase, "drivers are making a greater number of hard braking events as they drive," according to Harbluk.

The bottom line, she said, is that hands-free may not mean hazard-free. "The implicit assumption for hands-free technologies is often that there's no appreciable change in driver behavior," Harbluk said. But her team's findings suggest that engrossing cell phone conversations may be "consistent with reduced situation awareness while people are driving, and also reductions in margin of safety."

Reference Source 89

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