Self-driving cars can navigate without human input using sensors like radar and computer vision. Experiments with autonomous vehicles began in the 1920s, and the first truly self-driving car appeared in 1980. At CES this month, 10 exhibitors showcased self-driving technologies including Navya's electric shuttle bus and Rinspeed's luxury living room-inspired vehicle. Waymo has been developing self-driving systems since 2009 and has logged over 3 million autonomous miles. Ethical challenges for autonomous vehicles include how to program responses in emergency situations.