Seems like this would be particularly vulnerable to terrorist attacks. There is a huge surface area that needs to be protected (tubes/pylons). If there are pods leaving every thirty seconds and traveling at supersonic speeds then taking out one pylon could kill several hundred people and leave the entire train inoperable. In a future where this design was used extensively to connect cities on the coasts it would quickly become a critical piece of transportation infrastructure. Attacking several arcs of the city graph simultaneously would be utterly debilitating. Especially if the system's relative efficiency leads to the displacement of other forms of transportation.
Nope. Read the document. Subsonic speeds with capsules 2 minutes apart. In the event of a catastrophic depressurization (i.e. bomb on a capsule or a pylon), all capsules stop. Worst case, 28 people in one capsule die. The rest are stuck for awhile until they can be evacuated. Not very spectacular.
