Uber has quietly begun monitoring the movements of some of its drivers in an experimental Texas-based pilot that is attempting to flag up dangerous driving.Abrupt movements in a smartphone’s accelerometer, a movement sensor built into most smartphones, can show when a driver accelerates and brakes too quickly – consistent with driving too close to the car in front, or “tailgating”. For all its success, one major stress point for the company has been its reliance on human drivers because, unlike computers, they are unpredictable and hard to monitor. The company seeks to get around this problem with its autonomous vehicle lab in Pittsburgh, Pennsylvania, staffed by former roboticists for Carnegie Mellon University. At an industry conference in October, Uber’s chief executive, Travis Kalanick, said it could be “five, 10, even 15 years” before there are autonomous vehicles that are completely safe.