In the 1930s, both the German State Railroad and industry were working on improving aerodynamics; these efforts were not devoted solely to locomotives. Express train passenger cars were also given streamlined forms. The driving motivation was primarily an increase in travel speeds. Decreased coal and water consumption was also on the railroad's wish-list. Innovations on the ends of the cars were particularly noticeable. Here the side walls were extended up to 150 mm / 5-7/8" to the buffers. In addition, the doors were no longer recessed; they were now flush with the sidewall. Sidewall skirting that covered the upper area of the trucks gave this group of cars name: "Schürzenwagen" or "skirted passenger car". The additional equipment increased the weight of the first design by approximately a ton over the weight of the standard car, which was technically identical. As with other designs, various versions were produced. The first deliveries to the German State Railroad were 3rd class skirted passenger cars. They had nine compartments, offering seats for 72 passengers. After doing away with the 3rd class, they were in service for the DB as 2nd class cars, before they had to make way for the modern 26.4 meter / 86 foot 7-3/8 inch cars.