[1] Thus, they serve the internal purposes of the railway company and are not used for general passenger or goods traffic.
Only by exception, and under special measures, do they form part of standard goods trains.
Commonly used as departmental vehicles are those wagons or coaches that, on account of their age and design, are no longer suited to or permitted to be used in normal service.
Certain departmental vehicles are built for a specific purpose e.g. the transport of ballast or as construction machines.
For example, in Germany, whilst they are considered secondary vehicles by the railways, they are considered regular vehicles by the tramways and trolleybuses and have to be operated under the normal regulations that govern the construction and operation of tramways.