Reply to "Recommended minimum distance between parallel tracks"

I run scale equipment and 2 rail.    I maintain 4 inches overall.    I do this in the yards to allow fingers to get in rerail cars if needed.    I have found any less, and some larger cars, is just too tight for me to work.

I do not have any articulateds, but I do have  80 ft passener cars.   My minimum radius is 52 inches (104 diamter) and I have not issues with things hitting on curves.    My largest loco is a 2-10-4.   

So I have gone slightly larger than NMRA recommendations on straights, and slightly less on curves for the radius I use.