It is also possible to install this car instead of the standard “freibox” covered car, after renaming the files freiflat.dff and freiflat.txd to freibox.dff and freibox.txd, respectively. By default, the freibox car does not appear in railway traffic; to display it correctly, it must be registered with the SA Train Limiter utility in one of the trains.
Credits:
TS 2015, Fernando33