Wiener Linien awarded Siemens a contract for 150 ULFs in 1997, and placed a second order in 2004 for a further 150 vehicles, all of which will be delivered by 2015. These vehicles are being assembled at Siemens' Simmering plant in Vienna.

The ULF has been criticised in a report by the audit department of the City of Vienna, which claims that up to 25% of the ULF fleet is out of service for maintenance at any given time.

Wiener Linien has not made any official announcements on future orders, but Bombardier has already begun to promote a Flexity LRV for Vienna. In an internal paper, Bombardier suggests two versions similar in length to the type A and B ULFs with an entrance floor level of 200mm (the ULF has an entrance height of 190mm).

The paper argues that savings of more than €300m in life-cycle costs could be achieved over a period of 30 years, based on an order for 170 vehicles. Like Siemens, Bombardier has local assembly facilities at Donaustadt, which is already building LRVs and could produce vehicles for Vienna.

Wiener Linien has stated that a decision on whether to launch a new LRV tender will be taken by the end of 2013.