Completion of the CBT, which officially opened on 4 September 2020, marks also the completion of the Alpine rail link project after 28 years of construction. The CBT is the shortest of a trio of tunnels which form the extensive US$25bn New Rail Link through the Alps (NEAT) – the largest infrastructure project in recent Swiss history. The other two tunnels are the Lötschberg (34.6km) and the Gotthard (56km), both of which opened for service previously. The trio have been hailed as forming the most important rail corridor between the North Sea and the Mediterranean.

As well as reducing journey times within Switzerland, the tunnel will also benefit European rail freight. It is now possible to save up to two hours in freight transport between Rotterdam and Milan.

The US$3.95bn CBT stretches from Camorino in the north of the country to Vezia in the south and forms the final section of the Zürich – Milan New Alpine Rail Link corridor project.

The tunnel comprises two single-track tubes around 40m apart linked every 325m by cross passages. Excavation was entirely by drill and blast performed simultaneously in both directions from the intermediate heading at Sigirino. Final breakthrough occurred in the west tube with great accuracy: vertical deviation was less than 20mm, horizontally it was less than 10mm.