The Hyperloop is a conceptual high-speed transportation system put forward by entrepreneur Elon Musk, incorporating reduced-pressure tubes in which pressurized capsules ride on an air cushion driven by linear induction motors and air compressors.A preliminary design document was made public in August 2013, which included a preliminary cost estimate for a passenger-only version at US$6 billion, while a version transporting passengers and vehicles was estimated at US$7.5 billion.