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What will the future RER B look like? The brand new images revealed!

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The Editor

@ IDF Mobilités

After years of waiting and delays, the future RER B train is finally showing its face. This Thursday, January 29, Île-de-France Mobilités unveiled the very first images of the head car of the MI20, a symbolic moment for a project that is as strategic as it is closely watched by users in the greater Paris area.

It's an image that RER B travelers have been waiting for a long time. This Thursday morning, Île-de-France Mobilités (IDFM) shared a video on X showing the very first front car of the MI20, the future train set to replace all the rolling stock on line B. Filmed outside the CAF factory in Alsace, the train already sports the light blue, white, and black colors of the transport organizing authority for the Île-de-France region.

Loaded overnight onto a truck, the front car then headed to the Alstom site in Crespin, in the North, where the final assembly will take place. “Were you waiting for it? So were we!” IDFM excitedly shares, referring to “a symbolic and concrete milestone” ahead of the testing phase. A strong signal, as the project has so far mainly been known for.

his delays.

An industrial project worth 2.5 billion euros

The MI20 represents a colossal investment: 146 trains ordered for a total amount of 2.5 billion euros, fully funded by IDFM. The aim is to completely modernize the RER B, which is the second most frequented line in Île-de-France with nearly a million daily passengers. The contract has been awarded to a consortium bringing together Alstom and the Spanish manufacturer CAF.

However, the schedule has slipped. The first trains, initially expected by the end of 2025, have had their launch pushed back multiple times: to mid-2027, then to the end of 2027. Last September, Valérie Pécresse, president of IDFM, and the CEO of Alstom confirmed a new delay.

In a year. Result: the complete delivery of the 146 train sets won't be finished until after 2030.

To try to make up for lost time, an emergency action plan has been launched. Ten test trains are currently being manufactured, and the first tests are scheduled for April 2026, ahead of a gradual commercial rollout starting at the end of 2028.

Major works on the line to accommodate new trains

Behind the scenes, SNCF is already prepping the ground. From January 5 to May 28, the RER B will be interrupted every night from 10:45 PM between Châtelet-Les Halles and Roissy airport. These works aim to enhance the electrical supply and to adapt the platforms for the arrival of the new two-level trains, which are heavier and more advanced.

This summer, from July 25 to August 16, the central section will be completely closed for 23 days to replace the switch gears and modernize the signaling. It's a challenging but necessary project to finally bring the RER B into a new era.