On first thoughts, the 2-6-2 wheel arrangement does not seem ideal for a passenger tank engine. In either direction, weight on starting is temporarily transferred from the coupled wheels towards the pony truck at the rear, which, of course, becomes the front when the loco is travelling backwards, and adhesion is momentarily reduced. More significant is the ability of the loco to effect quick turn rounds at journey’s end without having to use a turntable and, in theory, to perform equally well in either direction.
Why the name ‘Prairies’? Apparently, it stems from the erstwhile Chicago, Burlington & Quincy Railroad which served the western North American Prairie region, and favoured the 2-6-2 wheel arrangement, although most of its locos would have been of the tender type.