DB AG class 612

In the 1990s, DB planned to use tilting diesel multiple units for fast regional connections on winding routes. The 50 class 611 sets purchased from Adtranz from 1995 had so many problems that no more were procured. So it was decided to develop the class 612 from scratch.

The similarities between the classes 611 and 612 were, on the one hand, that both consisted of two cars, each with an engine, and on each car both axles were hydraulically driven. The tilting technology is also electric here and allows the car bodies to be tilted by eight degrees. Scharfenberg couplings were again installed to couple several trains. In addition to the new design and Cummins engines, the differences also included magnetic track brakes that allow use on steep stretches.

The DB received a total of 192 sets, which replaced locomotive-hauled trains on many routes. Additional motorized middle cars that had been offered by the manufacturer were not ordered by the DB. At the same time, the lines had to be upgraded for operation with tilting technology in order to be able to withstand the higher centrifugal forces in curves. This often did not progress as quickly as planned and there were often delays in upgrading the signalling.

Although one did not want to repeat the problems of the class 611, problems arose repeatedly in connection with the tilting technology. As early as 2004, cracks in the axles were registered, which led to a drastic reduction in the inspection intervals and ultimately to the tilting technology being temporarily taken out of service. Problems arose again in 2009 and 2015, which ultimately led to DB filing a lawsuit against the manufacturer, which was now known as Bombardier. The later installed automatic doors also developed defects in many cases and in 2003 led to a trapped woman being dragged along.

On some trains, the first class compartment was later reduced or removed. Others had to step in for ICE-TDs and got the IC color scheme and a customized interior in return. These changes were the reason that these were reclassified as class 612⁴. One set is used as a measurement train for tilting technology sections and listed as class 612⁹. Eight more, which DB no longer wanted to take over, were sold to Croatia.