While the commercial viability of the new Turin-Lyon line has attracted much debate, previously in Italy and now also in France, the start of works in 2005 near Susa (Italy), resulted in strong confrontation between population and police.

Key infrastructure projects are on the agenda at this week’s gathering of Europe’s leaders.

One of the most ambitious and controversial is a tunnel beneath the Alps.

Linking Lyon with Turin, it is set to become the longest rail tunnel in the world.

When completed, it will surpass the Japanese Seikan Tunnel. The tunnel will cut the journey time for passenger trains from Zurich to Milan by about an hour and from Zurich to Lugano to 1 hour and 40 minutes.

Besides this, it will increase total transport capacity of freight across the Alps, especially between Germany and Italy, thereby decreasing the freight volumes transported via rail to reduce environmental damage.

The project consists of two single-track tunnels. It bypasses the Gotthardbahn, a winding mountain route opened in 1882 across the Saint-Gotthard Massif.

AlpTransit Gotthard will hand over the tunnel to Swiss Federal Railways (SBB) in December 2016.

Work has begun on the Italian side, and the BBC’s correspondent Christian Fraser has been one of the first to see it.

The Turin-Lyon is a planned 220 km/h line connecting the two cities and linking Italian and French high speed rail networks. The line is part of the TEN-T Trans-European conventional rail network, and is not classed as “high speed railway” by European Commission.

The new line is planned to partially replace the old conventional one offering decreased travel time and reduced gradients, which will allow heavier freight trains to travel between the two countries.

The core of the project is a 57 km long base tunnel crossing the Alps between Susa valley in Italy and Maurienne valley in France. The tunnel will be the longest rail tunnel in the world.

The project is subject to much criticism, on the Italian and French side, due to great costs, strong decrease of traffic (both by motorway and rail), environmental risks linked to the construction of the tunnel and the supposed worthlessness of the new line. Problems about costs and traffic decrease are also supported by French Court of Audit with some documents published in 2012