Grand Paris Express: Delays, a huge bill, and the anger of elected officials – an investigation into an extraordinary construction project

With 200 kilometers of new track, 68 stations, and four automated lines, the Grand Paris Express is intended to transform suburban travel. But between January and August 12, 2026, technical progress was once again overshadowed by delays, a cost exceeding 35 billion euros, and growing anxiety in the regions still waiting for their metro system.

Presented as the largest urban transport project in Europe, the Grand Paris Express includes the creation of lines 15, 16, 17, and 18, as well as the extension of line 14, which has already been completed. The new network is intended to directly serve the major hubs of the metropolis, from La Défense to Saint-Denis Pleyel, passing through Roissy Airport, the Saclay plateau, and the eastern suburbs of Paris. Ultimately, approximately two million passengers could use it daily. The central objective remains to eliminate some of the journeys that currently require crossing Paris to travel from one suburb to another.

On the ground, work reached several important milestones in 2026. Train and automation testing intensified on the initial sections, while the 20 kilometers of tunnels for Line 18 were fully excavated in July. The Société des grands projets (Major Projects Company) also highlights the simultaneous construction of dozens of stations, service facilities, and maintenance centers. However, this technical progress is no longer enough to mask the project's main problem: almost all major deadlines have slipped compared to the initial promises.

Line 15 South delayed by another six months

On June 25, the Société des grands projets (Major Projects Company) officially announced a further six-month delay for Line 15 South, between Pont de Sèvres and Noisy-Champs. This 33-kilometer-long, 16-station ring line, the first complete in-ground line, was originally scheduled to open before the 2024 Olympic Games. Its commissioning was subsequently postponed to the end of 2025, then to the summer of 2026, before being announced for April 2027. It is now expected in the fall of 2027. The difficulties primarily concern the integration of automatic train control systems, railway testing, and the coordination of thousands of safety devices.

Line 18 presents a more mixed picture. Its first section, between Massy-Palaiseau and Christ de Saclay, is scheduled to open in early December 2026, slightly later than initially planned. The connection to Versailles-Chantiers remains slated for around 2030. Lines 16 and 17 are expected to be brought into service gradually between 2027 and 2030, while the eastern and western sections of Line 15 are not expected to be completed until around 2031. In Seine-Saint-Denis, elected officials have publicly requested that these new dates be adhered to, pointing out that residents have been planning their housing, employment, and transportation projects around constantly revised timelines for years.

A bill that has risen from 19 billion to over 35 billion euros

The cost of the Grand Paris Express is the other major issue. When it was conceived in the early 2010s, the project was estimated at around €19 billion. This estimate subsequently exceeded €35 ​​billion, excluding certain related expenses, particularly those concerning trains, station infrastructure, and the adaptation of existing networks. Rising material costs, the geological complexity of the tunnel boring machines, program changes, safety requirements, and the extended construction period have progressively increased the final bill. The Société des Grands Projets (Major Projects Company) maintains that its tax revenues will allow it to finance the project in the long term, but its debt will have to be repaid over several decades.

This drift fuels accusations of poor planning. Critics don't necessarily dispute the metro's usefulness, but they denounce a project launched with a timeline and budget that have proven overly optimistic. Each delay increases project management costs, prolongs land and equipment leases, delays revenue from new stations, and weakens the companies working on the construction sites. The issue of operating costs also remains sensitive: building the lines falls under the purview of the Société des Grands Projets (Major Projects Company), but their operation will subsequently burden Île-de-France Mobilités (the regional transport authority), which is already grappling with the rising costs of the regional network.

Exhausted residents and suspended territorial promises

For residents living near the construction site, the project has meant noise, vibrations, dust, truck traffic, and traffic disruptions for several years. In Champigny-sur-Marne, residents again complained in the spring of 2026 about the increasingly unbearable nuisances around Line 15 South. Elsewhere, controversies revolve around felled trees, the prolonged occupation of public space, and the compensation arrangements for businesses. Project managers emphasize the existence of monitoring and compensation mechanisms, but those affected frequently consider the procedures lengthy and inadequate.

Despite these criticisms, abandoning or significantly scaling back the Grand Paris Express no longer seems realistic. The tunnels have largely been excavated, the trains ordered, and entire neighborhoods have been redeveloped around the future stations. The network can reduce travel times, open up isolated communities, and limit some car journeys, provided that connections, buses, and housing actually keep pace. The question is therefore no longer whether this metro should be built, but whether the authorities will finally honor their new commitments. After a decade of postponed promises, the project of the century now hinges on one basic requirement: announcing realistic dates and keeping them.