Question from the non-nerd: these computer generated mock ups, are they based on any kind of real physics? Cos that^ thing just doesn't look like it would have enough momentum to complete the layout.
Old comment, but dragging it up. Yes, NL2 has a fairly good physics model (friction and air resistance) that gives a pretty good idea of how the coasters would actually run. I can't say I know exactly how it implements it, but I think the friction is a standard value which is applied according to the force of the train on the track (higher force = higher friction). Air resistance I think is probably similar, with some generic factor that's applied based on the speed of the train. Not perfect, of course, but probably not a long way off.
Does that make me one of the nerds, though...?