In order to speed up freight trains, the series Р (R) was developed with a 2-8-0 wheel arrangement to replace the existing 0-8-0 locomotives. The special feature was the tandem compound engine, in which the high and low pressure cylinders were located one behind the other on both sides. This saved the need for a cranked axle, but the special arrangement of the cylinders meant that there was a lot of maintenance work. Since the speed was soon no longer sufficient on flat land lines and more powerful locomotives were available on mountain lines, the locomotives were only used on industrial railways from around 1940. 