In the spring of 1950, the triumph began for the rail busses on the DB's rails. The builder Waggonfabrik Uerdingen created a vehicle, which became so popular in the following years like hardly any other. The single-motor class VT 95 soon proved too weak for operation on lines with many grades, especially with the trailer car. Therefore, in the future these units were to be equipped with a second motor plant. The specification profile for the regular production of the dual-motor rail busses also foresaw the installation of standard couplers (prototype coupler) and equipment similar to buffers, standard design brakes as well as multiple unit control. Starting in 1955, 329 class VT 98 (starting in 1968: 798) motor cars, 310 class VS 98 (starting in 1968: 998.6) control cars, and 320 class VB 98 (starting in 1968: 998.0) trailer cars were built in several production runs. Starting in 1980, the star for the dual-motor rail busses began to sink. Line abandonments and the use of locomotive-hauled trains caused a large part of the class 798 to disappear on storage tracks by 1987/88. Then the situation stabilized again on a low level. The last high point was the updating of units 798 652, 653, and 998 896, in which the passenger areas were also freshened up. As the "Chiemgau Railroad" for use between Prien and Aschau, they were even given the new turquoise / gravel gray paint scheme for regional service. The last two powered rail cars were not put into storage until May of 2000.
In the middle of 1996, the BSW Leisure Time Group VT 798 was founded in Ulm, from which emerged the Ulm Rail Bus Friends Association in 2002. This group tried with a lot of commitment to preserve "Chiemgau Rail Busses" as museum pieces. After 1½ years of negotiations with the German Railroad, units 798 652, 653, and 998 896 then came from the maintenance facility in Mühldorf to Ulm. Due to their bad condition after around ten years of use in commuter service, these cars had to be thoroughly overhauled with new seating upholstery, new curtains, new external and internal paintwork, overhauling of the public address system, and many other small repairs. In 1998, the units were also given their characteristic lettering "Ulmer Spatz" ("Ulm Sparrow") on the sides. The trailer cars 996 069, 225, 257, and 300 rounded out the roster between 1997 and 1999. They were then overhauled as bar, dance, and bicycle cars. On May 23, 1998, the rail bus set was officially christened with the name "Ulmer Spatz" ("Ulm Sparrow") by the mayor of Ulm at that time Ivo Gönner. Starting in 1999, it was used by the DB subsidiary Regional Service Alb-Bodensee, Inc. (RAB) mainly in excursion service from Ulm to the Münsinger Alb area and now and then, it was used further as the "Spätzle Express" to Trochtelfingen to the company station platform for the noodle firm "Alb-Gold". Due to the main maintenance deadline, these uses ended after the 2013 season and since then the units have been in storage.