@John C. posted:We use 4 inch spacing almost everywhere. In yards...straight sections 3.5" works.
Many people ask this question, and it is next to impossible to answer. The correct answer is it depends on the sharpness of your curves and the length of your longest 2 pieces of equipment.
We use curves ranging from 72 to 96 diameter. In places where there are parallel curves: 96 and 89--pictured below. That leaves a shade under 4 inches between lines. No issues. Our longest 2 pieces of equipment: 21 inches. No sideswipes!
My suggestion is to physically test prior to actual securing the track in place.
I did test before laying the track! There's no way I could live with 4" spacing, I have a bunch of articulated steam that would be taking out anything on the next track with that spacing. On our club layout we had two tracks with 4.5" spacing, the outer track was O90, the inner track was O81. My Vision Line Big Boy on the inside track sideswiped a 21" passenger train and took a bunch of cars off the rails.
I don't know what kind of equipment you run, but any scale articulated steam would seem to be a risk there.
