EDIT: Assuming you’re talking about FasTrack, if you only want center rail isolation, the 1 3/8” straight sections can be used in the same way for center if the jumper underneath is removed. The ones available for separate sale look a little different than this one, having roadbed on both sides, but the jumper is the same.
Here you can see the center rail gap that's not visible in Lionel's promotional materials.
Most track can also be converted by cutting through the appropriate rail(s). Easiest method is with a small abrasive wheel on a Dremel.