The Hyperloop Alpha is a transportation system located inside of a tube; where it is possible to reach speeds over 700 mph, and still keep it safe, and comfortable. It accomplishes this by using air in the same way as an air hockey table.
You can read the detailed paper here (PDF): http://www.spacex.com/sites/spacex/files/hyperloop_alpha-20130812.pdf
Hyperloop is considered an open source transportation concept. The authors encourage all members of the community to contribute to the Hyperloop design process. Iteration of the design by various individuals and groups can help bring Hyperloop from an idea to a reality.
The authors recognize the need for additional work, including but not limited
- More expansion on the control mechanism for Hyperloop capsules, including attitude thruster or control moment gyros.
- Detailed station designs with loading and unloading of both passenger and passenger plus vehicle versions of the Hyperloop capsules.
- Trades comparing the costs and benefits of Hyperloop with more conventional magnetic levitation systems.
- Sub-scale testing based on a further optimized design to demonstrate the physics of Hyperloop.