MI20 trains for RER B move toward dynamic testing

MI20 trains for RER B have reached their first test stage at Alstom’s Crespin site in northern France. This is reported by the railway transport news portal Railway Supply.

The first multiple unit has completed its initial run and is now moving toward dynamic testing. Île-de-France Mobilités is financing the EUR 2.5 billion order for 146 new trains, which are intended to replace the MI79 and MI84 units currently operating on one of Europe’s busiest urban rail corridors.

As reported by Railway Pro, the 146-train order is being delivered by the Alstom/CAF consortium in cooperation with RATP and SNCF Voyageurs, the two operators of the line. The new fleet will be introduced gradually as the existing MI79 and MI84 multiple units are withdrawn from service.

Around 1 million passengers use RER B each day. It is Europe’s second-busiest line after RER A. The route connects Paris-Charles-de-Gaulle Airport and Mitry-Claye in the north with Robinson and Saint-Rémy-lès-Chevreuse in the south. It also passes through central Paris.

146 new trains for the Paris RER B line

The MI20 fleet is part of a wider renewal program for public transport in the Île-de-France region. According to the regional transport authority, 1,550 new or modernized trains, RER units, metro cars, and trams have entered the network since 2016.

The EUR 2.5 billion investment allocated for the MI20 fleet is fully covered by Île-de-France Mobilités. It sits within a broader RER B program worth nearly EUR5 billion through 2030. That wider program also includes a single control center for RER B and RER D. In addition, it includes the deployment of the NExTEO automated driving system.

Île-de-France Mobilités says the delivery timetable was compressed after earlier delays. The project has also been made a priority for the Alstom/CAF consortium. Under the current target, the first trains are expected to enter service on the Île-de-France network by the end of 2028.

MI20 trains for RER B will increase capacity

The new RER B trains are being designed to provide more space and improve passenger comfort. The source text identifies crowding as one of the line’s main issues. Each unit will accommodate 1,063 passengers, up to 35% more than the current trains.

Seating capacity will rise to 342 seats. That is an increase of up to 22%. The new units will be 104 meters long, similar to the existing rolling stock. Still, their layout will change: each train will have seven shorter cars instead of four longer ones.

The bodies will be 3 meters wide. That makes them up to 20 cm wider than the trains now in service. The extra width is intended to create broader aisles and support smoother passenger movement inside the train.

Mixed train layout and passenger features

The MI20 will use a mixed layout. It will alternate between single-level and double-level sections. This architecture is intended to serve different passenger needs and journey types.

Areas level with the platform will be used by passengers travelling with luggage, strollers, or reduced mobility. Meanwhile, the double-deck parts of the train will provide more seats and greater comfort for longer trips. Between the cars, the gangway areas will use a metro-style arrangement, with wider circulation space, handrails, and longitudinal seating for shorter station-to-station journeys.

The open inter-carriage passages and continuous ceiling are designed to improve visibility through the train. They should also help passengers spread more evenly through the interior, without rigid separations between carriages.

The new rolling stock will be fully accessible. The design includes level boarding and a reduced gap between the platform and the train. This feature is described as especially important at stations located on curves.

The trains will include air conditioning, heated floors, and USB-C charging points. Also, they will have video surveillance with real-time image transmission and multiple passenger information displays.

Each unit will be fitted with 92 dual USB-C ports and 44 video cameras. That is 50% more than the current level. Different screen types will show route maps and travel information.

The layout also provides 90 priority seats. They equal 26% of the total seating capacity. In addition, each train will include four wheelchair spaces.

Dynamic testing follows the Crespin run

Each MI20 unit will have 14 doors on each side. The design is intended to shorten the time trains spend at stations. Access zones will make up 22% of the train’s total length, allowing passengers to board and leave more quickly.

This is particularly relevant on a high-frequency line with heavy traffic. Every second spent at stations affects punctuality, according to the source text.

Île-de-France Mobilités also states that recycled materials account for 25% of the materials used in the new trains. This is in line with objectives to reduce environmental impact.

The presentation at Crespin included the first test run of the MI20 test train. The unit already had its interior equipment installed. Its next stage will be the launch of dynamic testing.

At present, 10 trains are in production. The first multiple unit was assembled in spring 2026. This confirms that the project has entered an industrial phase after earlier delays.

If the current timetable is met, the first MI20 trains should begin running on the RER B network by the end of 2028. Their introduction will mark the start of a new fleet cycle for one of the Paris region’s most important transit lines.

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