Comment by astrodust

The idea of a 600mph train running in evacuated tunnels is about as old as the idea of trains itself: http://io9.gizmodo.com/5731620/in-an-alternate-universe-ther...

China is looking at building something like that: http://www.zdnet.com/article/china-developing-600-mph-airles...

Note that it's an above-ground system because the costs of building underground are utterly ridiculous for long distances.