LION built three decks. Best seen here:

Top level is about 60" up, 12" wide and flush against the rear wall
Middle level is about 50" up, 16" wide and set out 5" from the wall.
Lower level is about 42" up, 16" wide and set out 5" from the wall.
Loops and the helix are on the “blobs” in the middle of the room.
When designed the grades were great, but so were my locomotives, and so I paid them no heed.
When subway operations began, the trains could no longer make the grade and the loops and helix were added:

First Helix:

I just cut the track, added a full loop and spliced it in.
Now that has been remove and a new helix was installed:

This was done because I eliminated the two track main line and lower staging areas in favor of a four track main line.
The other blob table was also reworked, but that “helix” is rather a “long loop”, actually two of them, one up and one down.
In the operations department a train leaving 242nd street on the upper level would run all walls on the upper level, enter the upper level on the “West Blob” which after two turns end up on the middle level and running along the south and east walls. From there it enters the “East Blob” and runs down to the lower level where there is a loop at South Ferry, from whence it runs the railroad back to the top in the same way that it came down.
There are two express loops. They run the middle level the same as the local, but from the lower level it diverts at Chambers street and follows two separate long loops to return it to the middle lev