They run on 18" radius curves. I had an H10s pulling 2 of them reliably on EZ track, on a flat surface. I wouldn't suggest running them on 18" radius curves for a variety of reasons, but if you have to put a few 18" curves in a corner to get to a staging yard, they won't derail, probably.
If you're limited to 18" curves on your layout though, you're really better off with shorter cars.
If you're limited to 18" curves on your layout though, you're really better off with shorter cars.