Torino Porta Nuova–Trofarello

The first leg, only 13 kilometres (8.1 mi) long from Torino Porta Nuova (which had not yet been built) to Trofarello, was opened on 24 September 1848^[5] with a simple ceremony. Regular public service began the next day with six pairs of trains traveling between 7 am and 7 pm. Already this section required the building of the first important work with a long bridge over the Po River next to the Moncalieri station.

Trofarello–Asti

The second section of the line to Asti was 42 kilometres (26 mi) long, and was opened on 15 November 1849.^[5] This part of the line overcame major difficulties crossing the hills between San Paolo Solbrito and Villafranca where it had to climb a grade of 2.6 percent, then considered nearly impossible for trains to climb. Initially a temporary line was built between San Paolo and Dusino, with a connection from Dusino to Stenevasso provided by a horse-drawn bus. This system was unsuccessful and it was decided to purchase a locomotive from Robert Stephenson designed for the climb. This was built at his workshop in Newcastle upon Tyne and went into service in August 1851.

Asti–Alessandria–Novi–Arquata

On 1 January 1850 the 22-kilometre (14 mi) section was opened to Alessandria and Novi Ligure^[5] and on 10 February 1852 the 56 kilometres (35 mi) to Arquata was opened; the railway now reached 124 kilometres (77 mi) from Turin. This route provided no major difficulties except for the bridges near Serravalle Scrivia. The rail service proved to be satisfactory to the public, with the train taking only 3 hours and 40 minutes to cover the whole route, leading to improved profits for the company.

Arquata–Busalla–Genoa

This section required large engineering works. The 18-kilometre (11 mi) extension to Busalla was opened on 10 February 1853^[5] and required the building of eight bridges and four tunnels of lengths varying from 508 to 866 metres (1,667 to 2,841 ft).

On 18 December 1853 the line was completed with the opening of the last 23 kilometres (14 mi) between Busalla and Genova Piazza Principe station.^[5] The crossing of the Apennine was particularly difficult, especially the Giovi Tunnel, which was the longest in the world and particularly expensive to build. The route also required traction to cope with the long and steep gradient between Busalla and Pontedecimo. A group of engineers, including Henri Maus and Germain Sommeiller, studied new types of locomotives, also built by the Stephenson workshops, then known as the Mastodons of Giovi which consisted of two locomotives coupled back-to-back under the control of one driver^[4] and capable of hauling trains on the slope of 3.6 percent, which could not be matched by any other locomotive. They were able to haul trains of 150 tonnes (170 short tons) at 12 kilometres per hour (7.5 mph).

To avoid delaying the opening of the line, Piazza Principe station was opened as a temporary station, as had already happened at Torino Porta Nuova station and at other locations on the line.

Since the new railway had a crucial role in moving both freight and passengers to and from the port a connection was built between Piazza Principe station and the port at Piazza Caricamento, almost entirely at grade along the road now called Via Gramsci. The line was opened to traffic on 18 December 1853 and on 20 February 1854 it was officially opened in the presence of King Victor Emmanuel and Prime Minister Cavour, who had both arrived on the royal train. The Archbishop of Genoa basptised three locomotives during the ceremony.^[4]

Genoa Piazza Principe–Genoa Brignole

In 1865 the line was absorbed into the new Upper Italian Railway Company (Italian: Società per le strade ferrate dell'Alta Italia).^[6] The line became part of the Mediterranean Network (Italian: Rete Mediterranea) in 1885^[7] and part of Ferrovie dello Stato in 1905. On 25 July 1872 a tunnel was opened linking the two main stations in Genoa between Piazza Principe and Brignole, connecting with the line to Pisa and Rome, increasing the length of the Turin–Genoa line to its current 169 kilometres (105 mi).

Second Pass

Because of the early industrialisation of Turin and despite the difficulty of operating the line and the confined docks of Genoa, the line immediately became the busiest railway in Italy.^[8] On 15 May 1889 an alternative 24-kilometre-long (15 mi) line through the Giovi pass opened from Quadrivio Torbella (Rivarolo Canavese) to Ronco Scrivia, known as the Second Pass (Italian: secondo valico).^[9] The new line was needed to meet the significant increase in demand for freight transport to and from the port of Genoa. The route of the line is close to the original line, but it is much faster and safer because it presents fewer problems for traction and braking because of its much lower gradients. This was made possible by bridges and especially by the 8,294-metre-long (27,211 ft) Ronco Tunnel. In 1922 it was enhanced further by duplication from Ronco to Arquata, where the line to Milan via Tortona connects.