Line 15 West is one of the key components of the modernization of public transportation in the Paris metropolitan area, designed to significantly improve connections between the suburbs. It is part of the extensive Grand Paris Express program, the largest urban transportation infrastructure project in Europe, aimed at transforming mobility in the Île-de-France region.

The European Investment Bank is currently examining the possibility of providing financial support for the construction of Line 15 West in Paris through a loan of up to EUR 3 billion, based on an estimated eligible cost of over EUR 6.6 billion.

This section constitutes the western segment of the future circular metro line that will encircle the French capital. Its route will be 22.4 kilometers long and will serve 14 localities in the Hauts-de-Seine and Seine-Saint-Denis departments.

Work is already at an advanced stage, with extensive underground excavation operations, including tunnel boring and station construction. Some of the underground tunnels have already been completed, while other sections are currently under construction.

This past spring, the Société des grands projets—the entity responsible for implementing transportation investments in the Paris region—announced the launch of the second tunnel boring machine for this section at the Île-de-Monsieur construction site. It starts from the Sèvres area, a strategic point where the South and West sections of Line 15 intersect. In fact, the same location was previously used in 2020 for the launch of the “Laurence” TBM, which completed a section toward Clamart.

The new TBM, named “Tiphaine,” is set to travel approximately 5.1 kilometers to the future Rueil – Suresnes Mont-Valérien station, with the estimated completion date for this section being 2028. The machine, manufactured in Germany by Herrenknecht, weighs over 1,600 tons and is approximately 110 meters long. Its assembly began at the end of 2025, and the actual start of excavation work is imminent. This is the 34th TBM used in the Grand Paris Express project.

To carry out a significant portion of the work, the IntenCités15 consortium, led by Vinci Construction Grands Projets, is managing the construction and outfitting of 13.3 kilometers of tunnel between Pont de Sèvres and the Boulevard de la Paix area in Courbevoie. The contract also includes the development of several intermediate sections, such as those between Rueil–Suresnes Mont-Valérien, Nanterre La Folie, and Courbevoie, as well as the construction of five stations and 16 technical structures.

Line 15 West, together with the South and East sections, will form a circular line of approximately 75 kilometers, connecting 45 towns around Paris. It will become the longest metro line in France and will be structured into three main segments:

Line 15 West will connect 11 stations between Pont de Sèvres and Saint-Denis – Pleyel, reducing travel time to approximately 26 minutes, down from 51 minutes currently, upon its scheduled opening in 2031.

Overall, Line 15 will incorporate 36 new stations, most of which will be connected to existing transportation networks—including Transilien commuter trains, the RER system, the metro, trams, and buses. The new infrastructure is expected to serve over 1.5 million passengers daily.

Beyond the mobility benefits, the project also has a major economic dimension, as it is considered a strategic factor for the development of the Île-de-France region, which contributes approximately 30% to France’s gross domestic product.

As part of the Grand Paris Express project, Line 15 South has entered a crucial preparatory phase prior to commissioning, alongside the other sections of the new metropolitan network around Paris. Underground, trains are already being tested under real operating conditions to validate the safety and performance of the systems.

During the tests, the rolling stock reached speeds of up to 120 km/h, recorded in March 2026 on the eastern section of the line. The tests include a variety of scenarios—from acceleration and braking to emergency stops—to verify the operation of the automated systems and the reliability of the entire technical infrastructure.

At the same time, trains have begun running progressively on increasingly longer sections of the route as work is completed at stations and in tunnels.

Each piece of equipment in the stations is tested individually and integrated into a centralized control system, which coordinates the entire line in real time.

This testing phase is essential for the opening of Line 15 South, scheduled for 2027, and is a prerequisite for its integration into the fully automated Grand Paris Express network.

In this broader context, the development of Line 15 West must be viewed as an integral part of the profound transformation driven by the Grand Paris Express project, which radically expands the Paris region’s transportation network.

The program includes the construction of four new main lines—Lines 15, 16, 17, and 18—as well as the extension of Line 14, creating a system of approximately 200 km and 68 new stations.

Unlike the traditional network, which focuses on radial connections to the city center, this new infrastructure is designed to facilitate travel between suburbs, reducing dependence on central hubs and distributing passenger flows more efficiently. As a result, for 3 million residents, daily travel time is expected to decrease significantly, with an estimated average of about 30 minutes.

The new lines will operate with fully automated trains and high frequencies, contributing to increased capacity and reliability of public transportation. More than just a mobility project, the Grand Paris Express serves as a catalyst for urban development, with each station designed to be a hub for investment, housing, and economic activity, thereby strengthening the territorial balance of the Île-de-France region.