Tailgating, swerving, constantly changing speed—these seem like signs of drunk driving. But they're actually behaviors of someone on a phone behind the wheel, according to a study at the University of Utah. Researchers used a driving simulator to compare people who were drunk with those on cell phones and found that while people with a blood alcohol content of .08 percent tended to drive more aggressively than cell users, both groups crashed at about the same rate.
A cell phone conversation impairs the brain—similar to the way downing an 80-proof vodka-orange juice cocktail does. But in this case it's an overload of stimuli, not alcohol. "The frontal and parietal cortexes are responsible for spatial processing, decision-making, coordination, and focus—all critical for driving," says study author and psychology professor David Strayer, PhD. A phone conversation introduces other thoughts into that careful calibration. "Overstimulation is actually worse for teens than for adults because their brains aren't fully developed," says Strayer. A teen might look directly at a hazard and still not grasp it; this is called inattention blindness. "The brain may not produce thoughts like, 'That light is red and I should stop,'" Strayer says. The look-but-don't-see phenomenon slows cell users' reaction time and makes them 10 times more likely to run a stop sign. "You'd think drivers would be more likely to notice something important, but they don't," Strayer says. "They're just as blind to a pedestrian as to a billboard." Even people using hands-free phones are four to five times more likely to be in a serious crash than drivers who aren't on a phone. And while drinking-related crashes kill fewer teens today than 20 years ago, non-alcohol driving fatalities are steadily climbing, Strayer says. "We've traded one threat for another."