Siemens supplied an initial batch of 150 ULFs to Wiener Linien from 1997 onwards, and is currently delivering a second tranche of 150 vehicles, the last of which will roll off the assembly line at the company's Simmering plant in Vienna in 2015.
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. The only city besides Vienna to order the ULF is Oradea in Romania, which operates a fleet of 10 vehicles.
Bombardier has been pushing hard for the new tender and looks likely to be one of Siemens' competitors in the tender process. The company has already promoted an LRV for Vienna based on its Flexity platform.
A Wiener Linien spokesman says that the company has decided to launch a new tender to evaluate the latest technical developments in the LRV market.
The tender documents will be published before the end of the year but it is clear that one of the major challenges facing bidders will be the need to meet the ultra-low floor requirement of a 20cm entry height. The ULF has an entry height of just 19cm, lower than many more recent LRV designs.
The new LRVs are due to be delivered from 2017 onwards.