In order to replace the passenger transport capacity on branch lines that was lost during the Second World War, the Belgian state railways procured four-axle diesel railcars of the types 602 and 603 from 1954. A diesel engine from Carels with an output of 400 hp was used as the power plant. The vehicles stood on two bogies, only one of which was driven on the inner axle. This limited their field of application to routes in the lowlands. The differences between the two series were limited to the design of the interior. While the Type 602 also had a first-class compartment and a luggage compartment, the Type 603 only had second-class seats.

The order included six Type 602s and 30 Type 603s. The former served as a feeder to Brussels Airport, while the others served on secondary routes. In addition to the motor cars, trailers were also ordered, which were designated as Type 732 and 734 and had two or four axles.

Types 602 and 603 were later renamed MW 42 and MW 43. After the feeder to Brussels Airport was electrified, the MW 42 were converted into MW 43. As vehicles got older, some vehicles were fitted with General Motors two-stroke diesel engines. This resulted in the MW 44 on the one hand, which was given an engine consisting of two combined four-cylinders and still only driving one axle. In addition, the MW 45 was created, which received two individual six-cylinder engines, each with 165 hp, each driving one axle of each bogie. Other vehicles were converted into railway service vehicles in the 1980s. The last remotorized vehicles were in service until 2002 and were then replaced by the MW 41.