Prototypically as example the Pennsylvania Railroad spaced main line tracks on a 13-foot center line for straight sections. On our 1:48 this is 3-1/4-inches. And this would work just fine with any of our 1:48 stuff as long as we went straight for infinite.
But our problems arise because our curves are no ware close as broad as prototypical. I have check all my large scale engines and rolling stock for "overhang" and "inhang." The worst case found was the MTH scale Big Boy with a front end overhang of 3 1/16-inches(from center line) and the cab overhang of something less on GarGraves O72 curves.
Also to note that Ross double crossover spacing is about 4-9/16-inch. This will work if using 089 curves or larger transition off of the straight section.
