The European standard EN 13044 has been in existence since December 2000. Following a thorough revision, a new draft was published in December 2008. The breakthrough came when UIC railway companies and UIRR operators adopted an implementation plan for the application of the standard that had been published in January 2011.

EN 13044 (all parts) regulates the marking of intermodal loading units that are used in European Combined Transport. The marking system can thus be applied for railway-compatible swap bodies, containers with a non-ISO standard design and cranable semi-trailers. The standard follows the format used in EN ISO 6346, the globally accepted standard for the marking and coding of maritime containers.

The EN 13044 essentially describes two things:

• an identification system and related markings for intermodal loading units (ILU). This is the ILU Code (EN 13044 Part 1).
• markings of swap bodies and cranable semitrailers for rail operations. This is the railway specific authorisation of the loading units for Combined Transport, also known as codification (yellow plate) (EN 13044 Parts 2 and 3)
   

EN 13044 (part 1) commissioned UIRR (International Union of combined Road-Rail transport companies, established in Brussels, Belgium) to administer the ILU-Keys for marking intermodal loading units in Europe on behalf of all stakeholders in intermodal transport.