Compliance with ENs could be one or more of:

  • voluntary – where industry chooses to use the EN when it is useful to do so
  • harmonised – where the EN is harmonised with a European Directive or a Technical Specification for Interoperability (TSI), compliance with the EN gives a presumption of conformity with the Directive or the TSI
  • mandatory – where the EN is referenced in the text of a document which must be complied with in specified circumstances, such as a TSI or a Railway Group Standard (RGS), compliance with the EN becomes mandatory.

ENs are produced by these European standards organisations:

  • The European Committee for Standardisation (CEN)
  • The European Committee for Electrotechnical Standardisation (CENELEC)
  • The European Telecommunications Standards Institute (ETSI)

In the UK, ENs are published by the British Standards Institute (BSI) as BS ENs.

Harmonised European standards

The European Commission publishes in the EU Official Journal lists of ENs that are harmonised against particular Directives or TSIs.

Harmonised ENs relating to railway applications have one or more 'Z Annexes'. These identify the legislation and essential requirements that are supported by the EN. If a harmonised EN supports more than one European Directive or TSI, there will be an 'Annex Z…' (ZA, ZB, ZC, etc.) for each Directive or TSI.

How does the GB rail industry influence the content of a European standard?

European standards in the field of railway engineering are drafted in two European Standards Organisations; CEN/TC 256 and CLC/TC9X.

The BSI establishes Mirror Committees that follow the development of a particular EN. RAE/1 is the BSI GB mirror committee for CEN/TC 256 and GEL/9 is the BSI GB mirror committee for CLC/TC9X. 

These committees provide a mechanism for GB input into the development of the EN. They also establish a GB position when the EN is circulated for consultation and voted on for approval. GB representatives are nominated as members of a series of working groups to draft the standards. The different working groups, the GB representatives, the BSI GB mirror committees, and the standards in each subject area are outlined in the CEN/TC 256 and CLC/TC9X structures and GB Involvement in the links below.



RSSB, on behalf of the BSI, provides the secretariat for those committees that mirror ENs relating to railway applications in both CEN and CENELEC.

You can access the catalogues produced by the European standards organisations from their websites:

You can also access and purchase ENs from the BSI website and the BSI Shop.

How do I deviate from a European standard?

Due to the nature of an EN, there is no need to formally deviate from it. If you cannot comply with an EN that is 'mandatory' because it is referenced in a mandatory document, you need to follow the procedure for deviating from the particular document that references the EN.

For example, you would apply to RSSB for a deviation from an RGS or the Department for Transport for a deviation from a TSI.

Where can I find British Standards and ISO Standards?

A number of railway-related British Standards will not be produced as ENs.  You can find these on the BSI website and the BSI Shop.

You can also find International Standards, produced by the International Organization for Standardization (ISO), on the BSI website and the BSI Shop.