The Lyon-Turin railway link, also known as the TELT project, has faced significant cost increases over the years. Originally estimated at 36.3 billion euros, the project's total cost has now reached 66.5 billion euros by the end of 2025. This represents a nearly 85% increase in the overall budget. Construction has made some progress, with 19.2 km of the main tunnels and 26.1 km of auxiliary tunnels completed so far. However, less than one fifth of the base tunnel under Mont-Cenis is done, more than a decade after work began. No passenger trains have yet used this structure. The cost for the transboundary section—connecting France and Italy—has risen by 127% in six years, from 5.2 billion euros to 11.8 billion euros. The French access routes, which are essential for connecting the tunnel to the national rail network, are not expected to be ready until 2045, twenty years after the tunnel is projected to be completed. Around 3,000 workers are currently working around the clock to excavate 37 million tons of rock. Eighteen excavation fronts are active, using tunnel boring machines to dig through the mountain, including a specialized machine drilling a 500-meter-deep ventilation shaft in Avrieux. The project's timeline has been repeatedly delayed. Initially expected to be completed by 2015, the completion date was first pushed to 2030 and is now estimated for 2033, an 18-year delay from the original plan. Three major revisions have been made in the last decade. In less than two years, three fatalities occurred on the site: a 51-year-old worker, a 31-year-old technician, and a 64-year-old engineer. The base tunnel is the main driver of the cost overruns. The revised cost for the transboundary section in November 2025 was 11.828 billion euros, compared to 5.203 billion euros in 2019. The rest of the budget covers the French and Italian access routes, new stations, and related infrastructure. This cost increase is not unique to Lyon-Turin; it is one of two major European railway projects contributing to significant budget overruns in the broader trans-European transport network. The French access routes are significantly behind the progress of the tunnel itself and are not expected to be completed until 2045. This means that while a train will eventually be able to cross the Alps under Mont-Cenis, the French side will lack the necessary infrastructure to support full operations between Lyon and Saint-Jean-de-Maurienne. This gap between the international tunnel and national connections has been a long-standing issue, sparking debates among local communities, environmental groups, and those advocating for shifting freight from roads to rail. Meanwhile, trucks continue to cross the Alps by road, and the timeline for the French access routes is extending beyond the tunnel's projected completion. A key question remains for users and taxpayers: what value will a completed tunnel have if the tracks leading to it on the French side are not ready for another two decades? The Lyon-Turin project, which has been underway for over thirty years, highlights the challenges of coordinating large-scale transboundary projects, where each component depends on the budgetary and political decisions of two countries and the European Union, which funds but does not always control the timeline.