When building rails along a 45-degree diagonal, two tracks can run adjacent if they remain on flat ground, but not if one of the tracks contains a ramp. This stands in contrast to tracks running parallel to the terrain grid, where a ramp does not cause a collision with adjacent tracks.
Flat, elevated diagonal rails can run adjacent as long as they're at the same height. Any difference in height, or any ramp section (even when the two tracks have ramps of the same height and grade), causes a collision.
