A summer of travel disruption awaits passengers in the Paris region... The RER C will be completely closed between Austerlitz station and western Paris for a major program of works from July 15 to August 22, 2026. This 39-day interruption is intended to secure the line and modernize infrastructure that is essential to the network's operation. The summer period is likely to be disrupted for users, with severely limited traffic in this strategic sector, as explained by our colleagues at Le Parisien.
This closure will affect journeys to Issy, Versailles and Saint-Quentin-en-Yvelines. Passengers will therefore need to plan their journeys in advance and use alternative routes. The aim of this operation is to enable major works to be carried out, which are necessary to maintain the performance and resilience of the Île-de-France network.
One of the main aspects of this summer interruption concerns the protection of the central tunnel of the RER C line against the risk of flooding from the Seine. Located below the level of the river, this section is a sensitive point in the event of rising water levels. Cofferdams, devices designed to limit infiltration and prevent flooding, will be installed to reinforce the safety of the infrastructure.
At the same time, SNCF Réseau will completely renew the catenary in the same tunnel. This work aims to replace aging equipment with a more robust system capable of reducing electrical incidents and service interruptions. These works are part of a comprehensive regeneration program across the entire network, designed to improve operational reliability.
This closure period will also allow progress to be made on the development of Issy station, with a view to its interconnection with the future Grand Paris Express line 15 south. The integration of this new automated line will transform connections and traffic across the metropolitan area, offering a more fluid link between the various transport networks.
These developments are preparing for the arrival of major infrastructure, the gradual commissioning of which should help to rebalance and structure mobility in the south-west ofthe Île-de-France region. The summer of 2026 is therefore an important milestone in coordinating the modernization projects currently underway.
During the 39 days of disruption, a replacement service will be put in place to limit disruption. Replacement buses will be provided, while alternative routes will be recommended on other lines in the rail network. Detailed information and support for passengers will be communicated at a later date by Île-de-France Mobilités, RATP, and SNCF.
This operation is part of a vast €3.8 billion investment program planned for 2026, which also includes interruptions on several metro and RER lines. Lines 4, 8, 12, 13, and RER lines A and B will also undergo major works during the summer, marking a busy period for the renovation of the Île-de-France network.
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