This European Standard provides a system for the identification and presentation of information about the ILU. The identification system is intended for general application, for example in documentation, control and communication (including automatic data processing systems), as well as for display on the ILU and other non ISO containers (i.e. which dimensions and testing parameters differ from those defined by the applicable ISO standards) used in European transport. The methods of displaying identification and specific other data (including operational data) on the ILU by means of permanent marks are included. This European Standard specifies: a) an ILU identification system with an associated system for verifying the accuracy of its use, having mandatory marks for the presentation of the identification system for visual interpretation; b) a coding system for data on ILU size, with corresponding marks for their display; c) mandatory operational marks; d) physical presentation of the marks on the ILU. This part of the European Standard prescribes the system of operational data for the codification of the semi-trailer. The codification assigns a maximum profile for the cover area available at the rail tracks to the semi-trailer in order to enable the selection of those rail tracks on which these semi-trailers can be transported without any danger. This part of the European Standard prescribes furthermore the additional operational markings, which are necessary for railway operation. This European Standard does not cover temporary operational marks of any kind, permanent marks, data plates, etc. which may be required by intergovernmental agreements, national legislation or non-governmental organisations other than CEN.