Linda has this in one. 
My old TRS2004 tracks used the old 'MRT' (Mesh Reducing Track) system, which gave you 2 'LOD' levels (high and low). It allows better, more efficient, tracks that were still high detailed close up. It's since been replaced by the new TS2009+ 'stitched' track system.
Since the track in question is mine, I'm going to make a recommendation on it straight off... Avoid the old MRT tracks, and use the newer 'VR BG Wood'/'VR SG Wood' series of tracks. They're based around similar textures (some better shadows 

 ), but have a better LOD system, and IMO a better ballast shape.
Most MRT tracks came in multiple lengths, as this allows long straight sections to be more efficient (e.g. some tracks had 16 or 20m long versions, which were really only suited to large yards). A well built track using the new TS2009 system is more efficient, and includes a few different length meshes. And I'll admit, my TS2009+ tracks on the DLS aren't overly efficient, but they were built in the very early days of the creation community nutting out the track-lod-tree system. I'm slowly working on a new set in my spare time to replace them, one day... 
Regards