A prototype of the three-car diesel multiple units of class 40 was built in 1957. In 1961 it was followed by a small series of six DMUs, which differed from the prototype in some details, but had the same look overall. The trains were used for internal services and for a connection with Tourcoing and Lille as well. They were taken out of service in 1984.
The engine unit is in fact a locomotive with a large luggage space. This space has never been used efficiently in service. Because of the presence of the engines, using this room for additional passenger accommodation was considered to be too costly, due to the measures that would have been necessary to reduce noise and vibrations. The unit has two diesel engines mounted under the floor.
The intermediate coach is nearly identical to a type M3 coach of type B12, but it has a first class compartment.
The control cab coach (or driving trailer) was constructed by replacing the endmost passenger seating by a cab identical to that of the engine unit. A small difference is the presence of corner windows in the control cab. (The prototype driving trailer did not have corner windows.)

The Trainz model can be driven from either cab. The diesel engines, however, can only be started in the motorized unit:
1. turn "Cab control" switch on the horizontal panel
2. turn switch "engine1 prepare"
3. turn switch "engine2 prepare"
4. push button "engine1 start" on the slanted board with coloured buttons on the right
5. push button "engine2 start" 

Engines can be started from this cab in any order. Each engine has its own exhaust and smoke production!

If you want to run the train from the trailer cab, first start the engines from the engine cab, then turn the cab control switch off. Once in the trailer cab, turn on the cab control switch there.
In the engine cab, the button for stopping the diesel lights up in blue once it has been started up.
Doors can also be opened and closed with switches on the push button panel, in both cabs. A button for the headlight is there too; the taillights follow automatically.
The horizontal panel has a small button on the right, which will RESET the script (and stop the train).
The engines can also be started up and shut down, one by one, through the pantograph icon on the Trainz screen. In driver command mode, the commands HP Start Engine and HP Stop Engine will work.