> ...if something goes wrong with the engine, the entire line is shut down, vs pushing a train off the track and other trains continuing. The train is propelle

> ...if something goes wrong with the engine, the entire line is shut down, vs pushing a train off the track and other trains continuing. The train is propelled by being magnetically coupled to a shuttle running underneath it. You could have more than one such shuttle; and the shuttles wouldn't have to run the whole length of the trip (potentially hundreds of kilometers in Germany, for example). There could be a new engine every few kilometers, with a backup. These engine units would be easy to replace; even easier than trying push a train off the track (which is not easy). > ...if you are going to build these atmospheric pipes why not put the carriages inside them? The pipe has to be much bigger to do that, and the pipe has to have an airlock to let people in and out of the train car. The airlock especially is apt to be a source of maintenance problems and safety incidents.