SNCF Class Z 22500

SNCF Class Z 22500 (MI 2N "Éole")

Company type	Electric multiple unit
Industry	Rail transport
Predecessor	SNCF Class Z 20500
Founded	1997
Headquarters	Valenciennes and Crespin , France
Products	Double-decker electric multiple units
Parent	SNCF

SNCF Class Z 22500 (MI 2N "Éole")

The SNCF Class Z 22500, also known as MI 2N "Éole" (Matériel d'Interconnexion à 2 Niveaux), is a dual-voltage, double-decker electric multiple unit (EMU) deployed on the RER E line of the Réseau Express Régional (RER), a hybrid rapid transit and commuter rail network serving Paris and the Île-de-France region.

Belonging to the MI 2N family managed by SNCF, the Z 22500 shares a strong resemblance to the MI 2N "Altéo" variant operated by the RATP Group, but differs in terms of its propulsion system and internal design.

A total of 43 trainsets, each comprising five cars, were manufactured through a partnership between Alstom (formerly GEC Alsthom) and Bombardier Transportation. Assembly was completed at Alstom's Valenciennes facility and Bombardier's Crespin plant from 1997 until 2000. The inaugural trainset was introduced into service in 1997.

History

By the close of the 1980s, the RER A line had become the system's most heavily trafficked route and ranked as the busiest single rail corridor outside East Asia. The severe overcrowding on RER A presented a significant transportation challenge across greater Paris. To mitigate this, SNCF initiated construction of the Est Ouest Liaison Express (EOLE), which was later designated as RER E, while RATP simultaneously developed Paris Métro Line 14. Both projects provided alternative corridors paralleling RER A through central Paris.

At the same time, RATP investigated double-deck trains for use on RER A. Existing double-deck models like those in the Z 2N series (SNCF Class Z 5600 and SNCF Class Z 8800) accommodated up to 2,600 passengers, surpassing the capacity of single-level MS 61 trains that had been in operation since RER A’s inception, which held around 1,887 passengers.

With both RATP and SNCF pursuing new rolling stock—RATP for RER A and SNCF for the forthcoming RER E—they joined forces in 1989 to issue a shared procurement tender. In November 1992, they placed an order for 17 MI 2N trainsets from a consortium combining French manufacturer Alstom (then GEC Alsthom) and Canadian firm Bombardier Transportation. The MI 2N design was derived from SNCF's SNCF Class Z 20500 units running on RER C and D lines but incorporated enhancements tailored to meet RER A’s high-capacity demands, including three wide doors per side rather than two.

The version produced for RER A by RATP was called MI 2N "Altéo," whereas SNCF’s adaptation for RER E carried the designation Class Z 22500 or MI 2N "Éole." Although their appearances are nearly identical, Altéo units feature three motors per set to enable quicker acceleration, while Z 22500 units are equipped with two motors and omit stairs leading to upper deck vestibules to gain an additional 22 seats per train.

A prototype unit arrived on March 10, 1996, for joint testing by both operators. Initially, Z 22500 trains operated as four-car sets on the Transilien Paris-Saint-Lazare network from September 1998 through June 1999 due to platform length limitations. Following this period, they were redeployed to the newly launched RER E line in July 1999, where they continue to serve.

Technical description

Each trainset spans approximately , offering capacity for up to 2,600 passengers with seating available for roughly 1,100 individuals. The formation consists of two non-powered driving cars equipped with pantographs, two powered intermediate cars, and a central trailer car. In contrast with the MI 2N Altéo used on RER A—which includes three powered cars—the Z 22500 contains two powered cars with fewer traction motors (8 compared to Altéo’s 12), resulting in slightly reduced acceleration rates (1.0 m/s² versus 1.1 m/s²), although braking capabilities remain comparable (1.15 m/s²).

The Z 22500 is compatible with both the RER E’s standard electrification at 25 kV AC and RATP’s older system at 1.5 kV DC. It accommodates platforms of varying heights and features three wide doors on each side to facilitate rapid passenger flow.

Unlike the Altéo variant, the Z 22500 does not include refrigerated ventilation systems or the SACEM automatic control technology but incorporates advanced safety mechanisms such as continuous speed supervision, automatic emergency braking, dual-mode communication via RST/GSM-R radios, onboard CCTV monitoring, and crash energy absorption systems inspired by high-speed train designs.

Its braking system integrates electropneumatic control managed by a Train Control and Management System (TCMS), regenerative and electrodynamic braking that contribute to energy recuperation and reduce wear on components, as well as electromagnetic track brakes for emergency stops—enabling deceleration rates up to .

Replacement

The Z 22500 trainsets are being succeeded by the RER NG units, which commenced operations on RER E in 2023. Initial intentions to redeploy the Z 22500 trains to different routes were discontinued because of the substantial costs involved in modifications. Nevertheless, since their launch, the RER NG trains have experienced frequent malfunctions, prompting Alstom to suspend further deliveries until approximately autumn 2025 while resolving these technical challenges. This postponement affects both passenger services and the upkeep of the remaining MI2N Z 22500 fleet operating on RER E.

Formations

As of 1 March 2022, a total of 53 Z22500 trainsets (numbered 01E through 53E) were stationed at the SNCF depots in Chelles and Noisy-le-Sec.

The train cars are classified as ZRBxe (driving car equipped with pantograph), ZBxe and ZRBe (powered motor cars), and ZABe (central trailer). The suffix "e" signifies a double-decker configuration, though it may occasionally be omitted in certain designations.

Each trainset is composed of three motorized cars paired with three unpowered trailers, forming a 2M3T arrangement.

	← Haussmann–Saint-Lazare (Paris) Chelles–Gournay/Tournan →
Car No.	1 >	2	3	4	< 5
Type	T	M	T	M	T
Numbering	ZRBx 2215xx (odd number)	ZBx 225xx (odd number)	ZRBx 2225xx (trainset number)	ZABx 225xx (even number)	ZRBx 2215xx (even number)

• The symbols < and > denote cars fitted with pantographs; specifically, the first and fifth cars each have one pantograph.