The details of the most hyped transportation technology since the Segway have finally been revealed: Elon Musk's Hyperloop Alpha. It is (surprise!) a series of tubes. Specifically, low-pressure tubes suspended by pylons.
Musk's plans outline an initial route between Los Angeles and San Francisco with an estimated travel time of 30 minutes. His analysis suggests it could be built for under $6 billion, paying for itself in 20 years with a ticket price of $20 in today's prices.
Of course, Musk's plans are no more than that. Musk isn't planning to develop any of the technology he describes in his white paper; nor does he have any plans to tackle the difficult political and logistical problems of actually getting the system built. So while it's a nice idea, there's no way to know if it's practical without a lot more work.

