The Tesla’s driver told authorities that the vehicle’s “full self-driving” software braked unexpectedly and triggered the pileup on Thanksgiving day.The pileup took place hours after Tesla CEO Elon Musk announced that its “full self-driving” driver-assist system was available to anyone in North America who requested it and had paid for the option.“Full self-driving” is designed to keep up with traffic, steer in the lane and abide by traffic signals, but despite Tesla’s name for it, it requires an attentive human driver prepared to take full control of the car at any moment.Tesla’s driver-assist technologies, Autopilot and “full self-driving” are already being investigated by the National Highway Traffic Safety Administration following reports of unexpected braking that occurs “without warning, at random, and often repeatedly in a single drive,” the agency has said in a statement.Musk has said before the company would be “worth basically zero” if it doesn’t provide “full self-driving.”"