The works, awarded by Infraestructures Ferroviàries de Catalunya (IFERCAT), include the works of section I, which connects the Josep Tarradellas Barcelona-El Prat airport with Fira de Barcelona, in Hospitalet de Llobregat, along a 14.9 km tunnel route. This section consists of 13 subway stations and 11 ventilation shafts.
For its part, section IV is located in Santa Coloma de Gramanet and includes a route of 4.3 km of track that runs through a tunnel, as well as the construction of six subway stations, a garage and workshops at the end of the line (Can Zam) as well as ventilation shafts. Other works are the intermediate tunnel structure, track and catenary, technologies for the construction of concrete keystones with concrete fivers within a new design of optimized reinforcement and the aquifers bypass system.