If I understand you correctly, the type of operation you envision for your layout is having a train "zig-zag" along the line, with the train being not the same and the individual scenes completely separated vertically and not connected by track. When the train arrives at the physical end of one section, it triggers the train above.
Quite an interesting scenario!
The easiest to get a train out of side is to hide it. This could be accomplished by just anything - a row of buildings, inside a tunnel - depending on the scenery of that particular section. The big issue with this concept is the reverse operation, for which you three options
A fiddle yard requires manual interference, i.e. picking up the loco and placing it back on the track on the other end of the train. You may not like it.
A run-around loop requires visibility of some sort.
A return loop requires a certain width. 2´ would be the absolute minimum for N scale.
If you want to have your layout automated, the third option would be the only way to go.
How wide do you plan your shelves? (Not familiar with your previous posts.) A 2' wide shelf would give you the possibility of return loops at the ends, whether reverse loops or a dogbone type having a two tracks all across the layout. You could hava a yard (staging) at one end to be switched. An answer depends on your desire to let trains just run some times or have a point to point, where you always have to switch things around to go the other direction. You could have a yard inside a hidden loop. If you hid enough of the loop, it could look like you had trains coming from two directions.
Good luck,
Richard
Hey Gang,
I have decided that I will be doing a couple shelf layouts in n scale. The idea is a per my previous posts I plan on modelling various time periods of CNR. Idea is a layout from the 1800's, 1900-1920, 1920-1940, 1940-1960, 1960-1980, 1980-2000, 2000-present. The periods might change as I work thru, but this is the frame work.
The idea is to mount 1 shelf above the other and link them so that when 1 train has completed its run the next one above will start in the opposite direction (separate layouts)
The issue I have is what does the train do when complete, how do I hide it? Do I make the shelf an oval? Issue is the shelf may become a little deeper than I anticapte.
The end of the line could be a destination, like a train station, grain mill, yard, or the train enters a tunnel and just ends.
Any suggestions would be greatly appreciated.