[piustjbz] More than center platform

For hypothetical extremely high capacity rapid rail transit, you could have 2 tracks going the same direction (and two tracks the other direction), with passengers loading from a center platform between the two tracks, instructed to take whichever train arrives first.

Can one do better than two tracks?  What if one wanted even more capacity?  One seems limited by the fundamental dimensionality of space.

One could make the trains longer, taller (double-decker), or wider (BART).

For efficient loading and unloading, doors on one side could be dedicated exit, while doors one the other (facing the center platform) could be dedicated entrance.