The Eje Diagonal involves the design, construction, finance, operation, and maintenance of a 65-km shadow toll road, of which approximately 20 km will be transferred to the Administration after the construction and will not be operated by the concessionaire. The concessionaire is responsible for to build and operate the Axis 3, Diagonal Axis (C-15 and C37) between Vilanova i la Geltrú and Manresa. The concessionaire will also maintain, adapt, and rehabilitate the works to ensure they are in line with the technical and functional characteristics needed to correctly provide the services or perform the economic activities that act as material support.

It also performs the replacement and major repair works needed in relation to the elements that each of the works must meet to ensure they are fit for use, so that the services and activities can be properly carried out in accordance with economic requirements and the demands of society.