The 35m-long bi-directional vehicles will accommodate up to 238 passengers with 70 seated. They will be assembled at Siemens' plant in Vienna and deliveries will begin in February 2014 with the final vehicle due to arrive in early 2015.
HTM awarded the contract to Siemens after its competitor in the tender, CAF, failed to win an appeal against the decision.
The Avenio is designed to be lighter than the preceding Combino, and Siemens has employed a steel body, a new welding technique, and reduced installed parts. It also features lateral stability elements to reduce forces acting on the wheel and railhead as the vehicle passes through curves.