The four bidders are:
• CAF, and
• A consortium of Siemens, Stadler Bussnang, and Stadler Rail Valencia
The order comprises 33 trains to replace B90 and B92 stock introduced in the early 1990s and 10 trains to expand fleet capacity.
The contract is due to be awarded in Autumn 2018 and the first of the 87m-long trains will enter service in 2022.
The new trains will feature air-conditioning, real-time passenger information systems, and mobile device charging points.