The RailMainTrackAndSiding subassembly is used to insert the rails, ties, ballast, subballast, subbase, and soil fill for a single- or two-track railway with turnouts.

The subassembly allows each track to have its own structural dimensions and can read alignment properties directly from the corresponding alignment—such as rail cant and alignment bearing at the cross-section location—to dynamically respond to cant changes and maintain minimum ballast depth requirements. It also accounts for cross-section rotation according to the bearings of two tracks when the siding track is not parallel to the main track.

The subballast top crown is positioned between the two tracks for double-track configurations, or centered under the middle of the rail tie for the single track. The subassembly is designed to work seamlessly with Daylight subassemblies on both sides to fit into the existing ground in cut and fill conditions.