An autonomous vehicle company has been testing its cars in Las Vegas without a human backup driver ready to take control in an emergency. The company Motional, a joint venture between between Hyundai and Aptiv, an auto tech company, announced Monday it has been testing its driverless cars in Las Vegas in February. The company received permission in November from the Nevada Department of Motor Vehicles to begin the tests without a back-up driver. Nevada in 2011 passed the nation’s first law to permit testing of driverless cars but backup drivers were required until 2017. Two other companies have started testing fully driverless cars in San Francisco and Phoenix.