These two yards resulted from a friend's request for a double-ended 6-track yard that could be fit in six feet of length but only 9-12 inches of width. Before going too far, he wanted to know just what was possible using PECO code 55 track and turnouts. 3DRRC&D is good for this, as it'll show the correct turnouts and allow you to see actual track spacing. Obviously, you could make this be 5 feet wide, or 8 feet...or whatever; but thanks to the accurate scaling, you can measure just how much space you'll have for rolling stock on each track.
As noted on the drawing, the reference grid is 6". The upper drawing uses WYES at the entries and medium-radius turnouts elsewhere; the minimum center-to-center track spacing is 1.5". The lower drawing uses all medium-radius turnouts; minimum spacing is 1.0"; this is tight, but usable. To help double-check your own measurements, the two center track in the upper drawing are 52.25" between the turnouts.
New 2-19-01