This interchange became increasingly important in the Chessie Era. The actual line splits in the next section at Miller but here you see the line at the bottom diverging from the East End. The WM line is called the West Sub Division and you can see where I labeled it so on the drawing.
Also this is the section of line where the East End splits into a high and low line. Main tracks 1 and 2 are on the top of the picture. These are the original two tracks and the ones that run the whole length of the East End. Track #4 is the Low Line track. It was built to make the transit east easier for the loaded coal trains. Trains headed east pick up the #4 line in Miller and rejoin the #1 and #2 in Cumbo. The low line is about 8 miles long in real life, but here it is just 10 feet. The low line is a longer route, but since the grades aren't so steep it is easier for heavy trains to use the #4.
The diverging of the West Sub and the Conrail
on the line (Cumbo and this section) towards the bottom of the
and not towards the backdrop at the top lead to some
would prefer the tracks to exit through the backdrop. To
I would need to redesign the layout so that these sections of
are viewed from the top and not the bottom of this
would require a helix (see discussions in York Hill).