DBAG Class 425

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DBAG Class 425 (and 435) / 426

Class 425 EMU at Unkel
Power type	Electric
Builder	Bombardier, Siemens and DWA (consortium)
Build date	since 1999
Total production	216 / 43
UIC classification	Bo'(Bo')(2')(Bo')Bo' resp. Bo'(A+A)'(2')(A+A)'Bo' (425) Bo'(2')Bo' (426)
Gauge	1,435 mm (4 ft 8½ in)
Driver size	850 mm
Length	67.5 m / 36.49 m
Total weight	114 t / 63.2 t
Electric system	15 kV 16.7 Hz AC
Top speed	140 km/h (160 when LZB-controlled)
Power output	2,350 kW / 1,175 kW
Locale	Germany

The Classes 425 and 426 EMUs are a class of electric multiple units built by a consortium of Siemens, Bombardier and DWA and operated by DB Regio in Germany. They are essentially the same vehicle, but the class 425 EMU consists of four segments, while the class 426 EMUs only have two parts.

It is a high-powered, light-weight vehicle with high acceleration for short- and medium-distance services with frequent stops. The aluminium superstructure was built as flat as possible, both to minimize drag and to ease automated cleaning. The acceleration is achieved by distributing traction motors among eight of the train's ten axles including two of the three jacobs bogies.

The trains have become infamous for their braking problems: On slippery tracks, the original braking software tended to optimize rolling friction towards a local maximum rather than the absolute maximum, resulting in a severe loss of braking power. In some instances trains overran platforms and signals for several hundred meters. A new software and sand sprinklers have solved these problems.