[1][2][3] In later years, the system was greatly expanded at the expense of conventional buses, which were regarded at the time as slow and uncomfortable.

Following the suspension of trolleybus services due to World War II, the system was restored and expanded during the post-war era, reaching its maximum length of 137 km in 1957.

The administration decided to improve the tram network (but in fact it was reduced), and by reintroducing trolleybuses on the most popular bus routes.

An order for 30 Solaris trolleybuses was placed in 2000,[4] to be low-floor, articulated, bi-mode vehicles capable of operating on batteries away from the overhead wiring for a portion of each trip.

[6] Construction of the infrastructure along the first route (90) began in September 2003,[7] while work to reequip ATAC's Montesacro depot for trolleybuses had begun in late 2002.

[10] Route 90 connected Roma Termini railway station with Largo Labia, in the city's northeast suburbs.

[10] Of the route's overall length of 11.5 km, the 1.5-km section between Stazione Termini and Porta Pia is not equipped with wiring, and is covered in battery mode.

It is 5.5 km long and has short sections at both ends that are not equipped with overhead wires, and which the trolleybuses cover in diesel mode.

[25] The trolleybuses used for the operation of the present system are Solaris Trollino 18 articulated vehicles, with electrical equipment supplied by Škoda Transportation subsidiary Ganz Transelektro, with ATAC fleet numbers 8501–8530.

They are fitted with a battery system to enable operation over the non-electrified section from Termini station to Porta Pia.