Thumb-typing while driving cripples your control of the steering wheel by 91 percent, and your reaction time by 35 percent, reports England's Transport Research Laboratory. That's far worse than booze or pot, which degrade response times by 12 and 21 percent, respectively. Still, the best reason to pull over is efficiency: The study's subjects fumbled with their phones for an average 63 seconds to send one message from behind the wheel, roughly three times as long as when they sat still and paid attention. (Illustration by Mike Kline)
