European goods transport involves increasing numbers of articulated lorries with semi-trailers of four-metre corner height. These vehicles can carry more freight per journey than the usual, lower trucks. Their proportion in the volume of traffic is therefore growing continuously. Although semi-trailers with a four-metre corner height could already be loaded onto trains before 2020, they could only be transported via the Lötschberg route. On the Gotthard route, the new base tunnels through the Gotthard and Ceneri were able to accommodate four-metre high semi-trailers; however, some tunnels, platform roofs and other facilities on the access routes were not.
In 2013 the Swiss parliament therefore approved the Federal Council’s proposal to build a four-metre corridor on the Gotthard route, and approved a credit of CHF 990 million for this. This significantly boosted the modal shift effect on the two NRLA routes – Lötschberg and Gotthard, as the Federal Council had hoped. In parallel to the NRLA, the four-metre corridor on the Gotthard route was completed at the end of 2020.
The main task was to adapt about 20 low tunnels on the access routes to the Gotthard and Ceneri base tunnels, and to remove obstacles on the open stretches, such as signalling equipment, platform roofs and traction power systems etc. The largest individual measure was the construction of the new Bözberg tunnel. So that the four-metre corridor can achieve its full impact, it must also be possible to transport the semi-trailers by rail beyond the Swiss frontier, as far as the terminals to the east and west of Milan. This also required the extension of lines in Italy by the end of 2020. Because they are very much in the country’s interests, the extensions on the Luino line in Italy were financed by Switzerland. The extensions on the line between Chiasso and Milan were paid for by Italy.