The abbreviation DD-IRM stands for “DubbelDeks-InterRegioMaterieel”, what means “Double-Deck InterRegio Material”. These are electric multiple units with three or for cars and a total of two powered bogies each. They have three-phase AC traction motors which were originally controlled by GTO thyristors. Later trains were built with IGBT and also the early ones were later upgraded.

The first sets were delivered in 1994 by Talbot of Aachen, which became part of Bombardier in the following year. To increase production capacity, De Dietrich in Alsace produced part of the cars. 34 three-car DD-IRM III were built with one trailer and 47 four-car DD-IRM IV were built with two trailers.

From 2002, all were rebuilt to the VIRM (“Verlengd InterRegioMaterieel” - “Extended InterRegio Material”) by adding further trailers. Former three-car sets received an additional trailer and became VIRM-IV. Four-car sets received an unpowered and a powered trailer and became VIRM-VI. More of these four- and six-car sets were built new. Today they are used as InterCity trains since the InterRegio does not exist anymore as a separate train type.