The ongoing development of European standards (ENs) makes it necessary for the content of the UIC leaflets (in this case UIC Leaflet 540, 6th edition) to be brought up to date vis-à-vis the ENs on the same subject (in this case EN 15355 and EN 15611) in order to remove duplication and discrepancies. Legitimate discrepancies and additions vis-à-vis the relevant ENs are mentioned in the present UIC Leaflet 540, 7th edition.