A people-carrying pod designed to levitate and travel at extremely high speeds has been unveiled in Boston.
A 30-strong team from the Massachusetts Institute of Technology (MIT) is one of several groups and companies working on making the Hyperloop concept a reality.
The idea, first envisioned by Tesla chief executive Elon Musk, is to create a transport system that propels pods through airtight tubes.
The MIT team said its pod design paved the way for "a mode of transportation that could change how we think about travel".
Critics of Hyperloop say it is unlikely to succeed because of prohibitive costs.
A white paper by Mr Musk published in 2013 proposed a Hyperloop tube connection from San Francisco to Los Angeles. At speeds of around 700mph (1,127km/h), Mr Musk predicted the journey time would be around 30 minutes.
Right now, travellers face either a six-hour drive, or just under an hour of flying.
Critics of the Hyperloop concept say it will prove to be prohibitively expensive to realise, while others say it may be uncomfortable for riders.
Through his SpaceX firm, Mr Musk will be funding a series of tests in tubes, expected to begin around August this year.
MIT's droplet-shaped pod uses magnets to lift itself off the aluminium track, reducing friction.
It is not currently big enough to carry a human being, but the team said once the full testing is complete it would be relatively straightforward to scale up to full size.
There are hurdles, however - the team said making the pod turn, even slightly, was a "huge problem".
Chief engineer Christopher Merian said while the team was confident with the levitation systems, the brakes needed "more testing".
MIT's unveiling took place in the same week another group developing the technology, a firm called Hyperloop One, tested its propulsion system in the Nevada desert.