Construction work on the Saint-Martin-la-Porte tunnel in France that is meant to provide access to the future Turin-Lyon railway link | Philippe Desmazes/AFP via Getty Images Italy’s high-speed railway dilemma Italy’s 5Star Movement is in trouble no matter what the decision on the TAV rail project.

SUSA VALLEY, Italy — A project to link France and Italy with a high-speed rail line under the Alps is turning into a lose-lose proposition for Italy's 5Star Movement.

The populist party, which now rules Italy in coalition with the right-wing League, vociferously opposed the project ahead of last March's election. That helped consolidate support in the Susa Valley, where opposition to the Treno Alta Velocità (TAV) between Lyon and Turin has festered since it was proposed in 1991.

"I can only feel anger and disgust at how the money of Italian citizens has been wasted," Italian Transport Minister Danilo Toninelli, a member of the 5Stars, wrote on his Facebook page.

But now that the 5Stars are in government, this puts it at odds with the League, who back the project.

"It is necessary to go ahead with the TAV, not go back," said Interior Minister and Deputy Premier Matteo Salvini, leader of the League. Although the party has indicated in recent days that the project could be scaled back. "The most reasonable thing is to downsize," said Giancarlo Giorgetti, undersecretary to the prime minister and a key League figure, on Sunday.

“This is Europe’s most dangerous border" — Alberto Poggio

The issue became even more fraught for the 5Stars after the Genoa bridge collapse that killed 43 people. Part of the movement's early appeal was its opposition to infrastructure projects, including a new highway in Genoa — and it is now paying the political price. Its earlier dismissal of warnings that the bridge was fragile as a "children's tale" has now been scrubbed from the party website (screenshot here).

Other parties are getting involved. European Parliament President Antonio Tajani, the de facto leader of Silvio Berlusconi’s Forza Italia — which is now in opposition — paid a visit to the valley this month, saying scrapping it would be “a wicked choice.” That drew the ire of Toninelli, who tweeted back: “Antonio Tajani and all the others blabbering on #Tav, should put their souls at rest. The fat times are over!"

The TAV is scrambling traditional political divisions. The center-left governor of the region of Piedmont, Sergio Chiamparino, backs the project: His offer of a referendum on it got support from the center right.

The 5Stars are now hedging their earlier opposition. Toninelli has commissioned a cost-benefit analysis before he makes a decision. Deputy Prime Minister (and 5Stars leader) Luigi Di Maio promised to “rethink” the project and to renegotiate the terms with Paris.

France, which in the past expressed reservations about the costly project — which it estimated at €26.1 billion — is now awaiting Rome's decision, while Brussels is asking Italy to stick with the plan.

“The project is now ongoing and it is important that all parties maintain their efforts to complete it on time,” said a European Commission spokesperson.

But if Rome follows Brussels’ advice, the 5Stars risk losing face with their electorate, which could boost the League’s dominant position in the coalition government.

A hole in the mountain

The depth of anti-TAV feeling is evident in the lush Susa valley, where graffiti opposing the rail line covers electricity poles and road signs. The tunnel construction site is ringed with barbed wire and under military and police protection.

“This is Europe’s most dangerous border,” joked Alberto Poggio, an engineer with the polytechnic university of Turin — although he says his comments reflect his personal views and not those of the institution. He is part of a group of experts backing the No-TAV camp.

So far the scheme has cost €1.46 billion for plans and 24 kilometers of preparatory tunnels — half financed by the EU, with the rest split between France and Italy.

“They are building a monstrous infrastructure with huge operating costs, especially if you don’t have the goods to fill it with" — Alberto Poggio

The 270-km rail line is supposed to be completed by 2030. It includes an €8.6 billion, 57-kilometer tunnel running under the Alps, and is part of the EU's Mediterranean transport corridor. The goal is to shift some of the truck traffic running between France and Italy onto rail, which would help reduce EU reliance on oil imports and cut emissions from transport.

“Today, over 4 million trucks travel east-west south of the Alps and there is no realistic rail link allowing to shift major part of road freight transport to rail. Lyon-Turin will offer such a possibility, and thereby reduce traffic congestion and CO2 emissions,” a Commission spokesperson said.

But the usefulness of the new line is in dispute.

Earlier Italian government estimates said that with the new line in service, there would be 40 million tons of rail freight moving between Italy and France by 2035. That's an enormous jump from the 3.7 million tons carried by rail in 2015 — accounting for only a small fraction of the 41 million tons of goods going between the two countries.

TAV opponents argue those numbers are grossly overestimated, something now accepted by the Italian government.

“They are building a monstrous infrastructure with huge operating costs, especially if you don’t have the goods to fill it with,” said Poggio.

Poggio feels the tunnel should be filled in and turned into a museum on how to squander public money.

But TAV supporters think it is “absolutely necessary,” according to Paolo Foietta, a special commissioner on the project, a post created by Rome in 2005 to mediate between the various stakeholders after riots in the valley. There is a conventional rail line linking the two cities, but TAV backers argue that it is steep and slow, while a new line is supposed to allow for much greater transport volumes at faster speeds.

Stéphane Guggino, CEO of the Transalpine Committee — a Franco-Italian association lobbying in favor of the project — warned there will be consequences if Italy walks out. “France will ask for money back, Europe will ask for money back. And if Italy does not give it, who will make agreements with Italy in the future?” he said.

The French transport ministry did not respond to a request for comment.

Sunken costs

The problem for the 5Stars is that the cost of exiting the project is high because work has already started — something that weighs in favor of continuing construction.

“If I do a stupid project, but I build three quarters, I probably should build it because all the benefits will go on that last quarter,” said Marco Guido Ponti, a retired economics professor with the Polytechnic University of Milan in charge of the cost analysis of the project to be concluded in the coming months.

But that's not exactly a ringing endorsement.

“Even if the numbers are positive, this analysis will show the previous madness — a project that has been launched with a highly distorted analysis on the calculation of benefits,” said Ponti.

CORRECTION: An earlier version misstated the length of tunnel. It will be 57 kilometers.