"Passante" is the Italian word for "passing" and is used to describe a railway built through a major city, connecting suburban lines.

The line would also allow the construction of several railway stations in order to create an urban metropolitan service.

The railway consists of three stations outside the city of Naples in Pozzuoli, Giugliano (its station, Giugliano-Qualiano is some distance from the centres of both Giugliano and Qualiano) and Quarto and six in the city at Napoli Garibaldi, Cavour, Montesanto, Amedeo, Chiaia and Fuorigrotta.

In 1935, the line was electrified with standard Italian Railways 3 kV DC Overhead Lines, a new station was opened at Cavalleggeri d'Aosta and the station at Piazza Garibaldi (beneath Napoli Centrale) was rebuilt.

Until 2009, the stations of Piazza Garibaldi, Mergellina and Campi Flegrei were also served by long-distance trains, but this severely interfered with the suburban services.