private and foreign railways well into the 1920s. For covered wagons there was the Class A2 wagon with a maximum load and loading area built to a standard template, and the large-volume covered wagon based on template A9, also with a maximum load, but a loading area. In the 1920s, wagons with interchangeable parts, the Austauschbauart wagons, were developed for the Deutsche Reichsbahn (DRG). They had similar overall dimensions, but were clearly built to a different design from their forebears. Once again there was a covered wagon with loading area, classed as the Gr Kassel and a large-volume wagon with loading area, called the Gl Dresden. In addition, the Austauschbau series saw two new wagon classes being developed. The Glt Dresden was largely similar in design to the "standard" Gl Dresden, but had end doors. These vans were bought to provide sheltered transport for motor vehicles. A second, newer type of wagon was the ferry wagon developed during the 1920s for rail ferry services to Great Britain. This wagon had the same length over buffers as the Gl Dresden, but a loading area of only , because of its narrower wagon body constrained by the smaller loading gauge of British railways. This was designated as the Gfh Trier. The next significant change was the introduction in the 1930s of welding into the construction of railway vehicles. The designs of the Austauschbauwagen were reworked to take advantage of welding technology. As a result, a successor to the Gr Kassel emerged: the Ghs Oppeln with a loading area. The designs of the Gl Dresden and Glt Dresden were also reworked whilst retaining the same loading area of ² (Glrhs). The Gfh Trier was also redesigned, but due to low demand this was not ready until 1940, and no more were built owing to the Second World War. The next stage of development was forced as a result of the Second World War. In order to save material and labour, railway vehicle designs were simplified. As covered wagons the Gmhs Bremen appeared as a successor to the Ghs Oppeln, and the Glmhs Leipzig followed the Gl Dresden. These so-called wartime classes (Kriegsbauart) were also welded, and had loading areas of and respectively. More robust variants of these wagon classes were procured after the war by the Deutsche Bundesbahn and the Austrian Federal Railways (ÖBB). Passenger use The covered goods wagon has been used