This is an automatic, driver-less underground railway line that links the city center with the southern outskirts of Rome. Part of it runs within a tunnel and another part runs in the open. The line is 20.4 km long, with a double line, for a total electrified length of 40.8 km. The line is powered at 1500 V with a rigid catenary, in the first application of a rigid catenary outdoors for a length greater than 1 km.
43-km underground line for automatic systems that crosses Rome north to south, with 20 km in the open air and the remainder within a tunnel. It is fitted with a 1500 Vdc rigid catenary.