Test track is just a 60 foot circumference oval that was flopped down one day where SWAMBO allowed. I'd had it elsewhere first, but it got into the way of her bird & fox feeding, so it had to go. As I understand it, real railroads often had problems securing right of way and trackage rights, so that just adds to the "scale effect" of my "Iron" (should read as Aluminum) Road.
Grades run from near flat to almost 6% on curves that are somewhat shy of a six foot radius. When I get my actual trackage laid, it should have a minimum radius more like seven or eight feet, which is really significantly better, and a maximum grade of about 2 1/2%, except on a ramp up to an ore bin and then further on up to a service platform, which will need to be a bit over 4%.
At 60 feet per lap, 88 laps makes an actual mile, or about 20+ scale miles ...... and both engines have done a whole lot of laps by now, and still running strong.