Wikipedia: " Except for the automatic coupling, ICE 2 powerheads are very similar to those of the ICE 1 and can actually be used in ICE 1 trains if strictly necessary.
Usually two ICE 2 half-trains are coupled to form a block train of similar dimensions to the original ICE 1 for serving the main routes, and separated again to operate on routes with less traffic or to provide the passengers two different destinations.
Until the class 808 cab cars have been tested and cleared for passenger service, two ICE 2 half-trains had been solidly coupled to form a permanent block train.
The passenger cars are very different from the ICE 1 cars, despite their similar exterior: The weight has been significantly reduced and the passenger compartments have been removed in favor of a seating arrangement similar to an airliner (due to reduced seat pitch). Also, the train has been equipped with air suspension to circumvent the wheel noise problems of the ICE 1, which led to the installation of rubber-buffered wheel rims on the ICE 1 units and therefore the Eschede train disaster.
ICE 2 trains have no service car as the class 803 on ICE 1 trains, on the other hand the class 808 cab car is unique to the ICE 2."