MI20 completes first full run at Alstom-CAF plant
FRANCE: The first complete MI20 trainset has run under its own power at the Alstom-CAF facility in Crespin, marking a production milestone for the EUR 2.5bn fleet ordered to replace ageing stock on Paris’s RER B.
Île-de-France Mobilités, Alstom and CAF presented the trainset on 7 May, the first time a fully assembled MI20 unit has moved under its own power.
The presentation confirmed that no complete MI20 set had existed before this run. Delivery of the 146-train fleet to RER B — Europe’s second-busiest commuter line — is now targeted for late 2028.
First complete set clears factory gate
Running under its own power distinguishes the 7 May presentation from earlier programme milestones. Previous showings involved individual car sections or static displays; the Crespin run confirmed that a fully integrated trainset can move as a functional unit.
The 146-train order covers full replacement of RER B’s MI79 and MI84 fleets, both dating from the 1980s and 1990s. The line carries approximately 1 million passengers daily, connecting Charles de Gaulle airport and Mitry-Claye in the north with Robinson and Saint-Rémy-lès-Chevreuse in the south — a volume that leaves no room for service disruption during fleet changeover.
Built for NExTEO
The MI20 is designed from the outset to operate under NExTEO, the automated train control system scheduled for the RER B network. The central tunnel between Gare du Nord and Châtelet–Les Halles is planned to go live with NExTEO in 2031, with full peripheral rollout by 2033.
The connection means MI20’s full operational potential depends on two programmes reaching readiness in sequence — fleet delivery and signalling infrastructure.
Testing and homologation ahead
Before revenue service, the trainsets must complete a testing and homologation programme on live RER B infrastructure. IdFM has set late 2028 as the service entry target.
The Crespin run opens that process. What follows is a validation sequence — dynamic testing, safety certification, and integration with existing RER B operations — before the first MI20 carries passengers.