The M4 series was ordered, along with the Series 03 electric multiple units AM-MS 80 / 82 / 83, to meet the needs of the future IC-IR plan of 1984 and the major electrification of the network. These cars were mostly used on IC or IR routes and later on certain P routes.

In the early 1980s, it was not uncommon to see M4 trains using baggage cars such as RIC or M2 B8D while awaiting the arrival of all the baggage cars from the series. Some M4 B11 cars were also fitted with a lock on the end compartment to temporarily convert them into baggage cars, as the A6D and A7D baggage cars were only delivered between 1981 and 1983, and the B7D in 1984.

The B7Dk luggage cars (k for keuken / kitchen) were equipped with onboard kitchens, but the kitchen service was discontinued between 1991 and 1994.  

Starting in 1995, SNCB-NMBS reconfigured the distribution of ‘smoking’ and ‘non-smoking’ compartments, significantly reducing the number of smoking areas. A blue line was added to more easily distinguish the smoking compartments.

From January 1, 2004, SNCB-NMBS removed smoking compartments from its passenger cars, which also led to the removal of blue lines and ashtrays. However, the M4m B11 cars still retained the blue lines above the windows, even though they no longer hold any significance.  

Between 1996 and 2009, the M4 series was aesthetically modernized and became the M4m with the gray ‘New Look’ livery*.

The M4m coaches were also equipped with MUX, allowing them to operate in push-pull mode with Siemens Class 18 and Class 19 locomotives.

Starting with the delivery of the Bombardier Transportation (Alstom) double-decker M7 coaches, the M4m series will be gradually replaced and is expected to completely disappear from the Belgian railway landscape by 2023.


*On October 8, 1995, the first two modernized cars were presented to the public and the press at Brussels-Midi: the A9 ‘50 88 19-78 049’ (51049) and the B11 ‘50 88 20-78 417’ (52417).  

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