This is done by constructing a metal tube of less than 2m diameter in which small 'cars' able to easily carry six passengers ride. The tubes are completely sealed and have all air removed. Effectively, the passengers are travelling through space. Most implementation plans include two tubes (either beside or above each other) to facilitate travel in opposite directions.
There are other proposals which consider even larger tubes in which a 'bus' might fit, or even large shipping containers.
The big, nay huge, advantage is that without air resistance the cars may be accelerated to very high speed (over 6,400 km/h) and once moving will need very little (if any) further energy to keep moving.
Even better, decelerating the cars will actually regain most of the energy for re-use.
At 6,400 km/h no two places on the Earth are more that 3 hours 10 minutes apart and in fact the journey from Sydney to Melbourne would probably take no more than 15 minutes.
Clearly, this is a relatively simple system for land-based transport, but what of trans-ocean? Proponents are suggesting a sub-sea tube mounting that will keep the ETT 45m to 90m below sea level; well below any shipping or storm influence.
The system was developed by Daryl Oster in the early 1990s, with a patent application in 1997.
So, what of the practicalities?