VRR announced the order on February 10 and was awaiting approval from the four tendering authorities, VRR, Rhineland Local Transport (NVR), Westphalia-Lippe Local Transport (NVR), North Rhineland Palatinate Regional Rail Transport (ZSPNV-Nord) and North Hessen Transport (NVV). Delivery of the trains will begin in 2018 and the fleet will enter service in time for the start of the RRX concession in December 2018.

Siemens says this is its largest German regional rail transport order and the company will build a maintenance facility in Dortmund-Erving to service up to four trains simultaneously. Up to 100 specialists will work at the facility, which will encompass a vehicle hall, specialised workshops, an outside washing station, and stabling facilities for 10 trains.

The Desiro HC trains combine single-deck driving cars with double-deck intermediate vehicles. According to Siemens, a 105m-long four-car Desiro HC set with two double-deck cars will seat up to 420 passengers.

The five-line RRX network will introduce a consistently high-quality fast regional rail service to Germany's most densely-populated region, with trains running at 15-minute intervals on the core Dortmund - Cologne line at a maximum speed of 160km/h. According to the tender, 71 trains will be required to operate the full timetable with the remaining sets covering maintenance.

VRR says the transport authorities decided to procure rolling stock directly, rather than through the operating concessionaire, because this will result in lower life-cycle costs and a standardised fleet.

DB Regio opposed this structure and launched a legal challenge against VRR, which was rejected by a court in Münster last October.