Using even a hands-free phone while driving can be dangerous

Something off topic, but safety first!  -Dr. Tang

Dec 4th 2008
From The Economist print edition

MANY countries have made it illegal to natter into a hand-held mobile phone while driving. But the latest research provides further confirmation that the danger lies less in what a motorist’s hands do when he takes a call than in what the conversation does to his brain. Even using a “hands-free” device can impair a driver’s attention to an alarming extent.

Melina Kunar of the University of Warwick, in England, and Todd Horowitz of the Harvard Medical School ran a series of experiments in which two groups of volunteers had to pay attention and respond to a series of moving tasks on a computer screen that were reckoned equivalent in difficulty to driving. One group was left undistracted while the other had to engage in a conversation about their hobbies and interests using a speakerphone. As Dr Kunar and Dr Horowitz report in Psychonomic Bulletin & Review, those who were making the equivalent of a hands-free call had an average reaction time 212 milliseconds slower than those who were not. That, they calculate, would add 5.7 metres (18 feet) to the braking distance of a car travelling at 100kph (62mph). The researchers also found that the group using the hands-free kit made 83% more errors in their tasks than those who were not talking. 

To try to understand more about why this was, they tried two further tests. In one, members of a group were asked simply to repeat words spoken by the caller. In the other, they had to think of a word that began with the last letter of the word they had just heard. Those only repeating words performed the same as those with no distraction, but those with the more complicated task showed even worse reaction times—an average of 480 milliseconds extra delay. This, the researchers suggest, shows that when people have to consider the information they hear carefully, as they might when making decisions about a business deal, it can impair their driving ability significantly.

But does chatting to passengers have the same detrimental effect on driving? An earlier study found that it does not. That research, led by Frank Drews of the University of Utah, analysed the performance of young drivers using a vehicle simulator. Dr Drews found that when using a hands-free phone, a volunteer “drove” significantly worse than he did when just talking to someone playing the role of a passenger. Passengers, the researchers believed, might even help road safety by commenting on surrounding traffic.

Dr Kunar and Dr Horowitz also explored the effect of simply listening to something—such as a radio programme. For this they played a recording of the first chapter of Bram Stoker’s “Dracula”. Even though the test subjects were told to pay attention because they would be asked questions about the story afterwards, it had little effect on their reaction times. Dr Kunar reckons that having to think about responses during a phone conversation competes for the brain’s resources in a way that listening to a monologue does not.. Dr Drews’s work suggests the same thing is true of the idle chatter of a passenger.

This could mean road-safety advice needs to be revised. America’s National Highway Traffic Safety Administration estimates that the use by motorists of hand-held phones is continuing to increase: to 6% of drivers at any given time in 2007, from 5% the previous year.. The biggest culprits are aged 16 to 24. People texting while driving, or fiddling with an iPod, also worry safety officials. Now it appears that talking on a phone even when both hands are on the steering wheel is dangerous too.

Punishing people for using hand-held gadgets while driving is difficult enough, even though they can be seen from outside the car. Stopping people making hands-free calls would probably be impossible—not least because more and more vehicles are now being fitted with the necessary equipment as standard. Persuading people to switch their phones off altogether when they get behind the wheel might be the only answer. Who knows, they might even come to enjoy not having to take calls. And they’ll be likelier to arrive in one piece.