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Why we can’t process driving and texting

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More and more Massachusetts residents are texting while driving, according to recent state data showing that over 6,000 drivers were ticketed last year for the offense, compared to 1,153 in 2011, the first full year a texting ban was in place.

That is very bad news, because new evidence suggests that our brains are able to compensate for many distractions and stresses while driving, but not for texting. People veer out of their lanes because of texting far more often than they do because of other distractions, and their driving gets worse if they are upset or absent-minded, according to the results of a recent driving simulation study.

“The worst thing you can do is text and be emotionally charged or totally absorbed. The second worse thing is just text,” says study senior author Ioannis Pavlidis of the University of Houston.

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At the Texas A&M Transportation Institute, Pavlidis and colleagues observed 59 participants drive a four-lane highway simulation under four conditions: without distractions, while answering emotionally charged questions, while answering mathematical and analytical questions, or while texting. To test the extremes of physical capability, half the participants were age 18 to 27 and half were 60 to 70 years old.

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The researchers registered a drivers’ stress levels by measuring the perspiration above their upper lip. The team also tracked the angle of the steering wheel — that is, how many degrees it turned to the left or right — and any lane departures. In each of the three experimental situations — emotional, cognitive, and texting — all participants showed stress via perspiration and tremors in their arms and hands. Such tremors or “jitters” are often imperceptible yet they can subtly move the steering wheel. “If you leave these tremors uncorrected for a few seconds, that results in a major lane deviation,” says Pavlidis.

During times of emotional or cognitive stress, the driver’s brain counterbalances the tremors as though on autopilot, and keeps the car smoothly in the lane. However, when the driver was texting, the brain appeared to be unable to activate autopilot, and the car drifted outside of the lane. Pavlidis suspects this is because the brain requires hand-eye coordination to correct the tremors, and texting interrupts that ability.

The team found that older drivers performed worse than younger drivers, but the silver lining is that older drivers tend not to text as much as younger drivers, says Pavlidis.

The group recently completed a similar experiment on a real road course and got similar results that have yet to be published, says Pavlidis. Because traffic during the driving simulation was light to moderate, there were no documented crashes, but when the team extrapolated the data to heavy traffic conditions, it was clear that texting leads to accidents.

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If you text, you will veer out of your lane, says Pavlidis. And each time you do so, it increases the probability of a crash. Eventually, there’s no avoiding the outcome, he adds. “If you keep doing this all the time, at some point your luck will run out.”

The research was partially funded by the Toyota Class Action Settlement Safety Research and Education Program.