This thesaurus is primarily concerned with suggesting preferred terms for use in indexing railway objects and establishing relationships between them. Complexes comprising many objects such as stations, depots or even complete railway systems are included.
The scope is limited to objects specific to railways in Britain or railway equipment manufactured in Britain. As a result some terms have been omitted, including terms of exclusively American usage and general terms for objects used by other industries as well as railways. For example, railway companies were heavily involved in catering and maritime operations but most of the artefacts connected with these enterprises were no different to those used outside the railway industry.