Italo Frigoli was trying out the Full Self-Driving software of his Tesla one evening in June when he came upon a railroad crossing. The arms were descending and lights were flashing as a train barreled toward the intersection. For most human drivers, the gate arms and lights are clear signals to stop, but for Frigoli’s Tesla, which was driving in a semiautonomous mode, the potentially deadly situation didn’t seem to register. “It felt like it was going to run through the arms,” he said. “So