HTM awarded Siemens a €100m contract for 40 vehicles in November 2011, and subsequently exercised an option for a further 20 units in March 2014. The vehicles are being assembled at Siemens' Simmering plant in Vienna.
Each 35m-long bi-directional LRV will accommodate up to 238 passengers with 70 seated.
In recent months Avenios have been tested extensively on Line 2 and sections of lines 3, 4, and 5. Trial operation has begun on Line 11 and the fleet will ultimately be deployed on lines 1, 2, 9, 11, 15, and 17.
A full technical description of the Avenio can be viewed here.