This relates to traceability and the information is used to manage IUU monitoring. As transport can be by either container or trailer/lorry, it is necessary to distinguish between them by registering either the container number or the trailer/lorry number.

Container numbers are in a standardised and internationally recognised format and are therefore considered a traceable transport unit, which is necessary for IUU monitoring. The number on a lorry/trailer, on the other hand, does not follow an international standardised format, as it differs between countries. These are often registration numbers or a transport company's trailer numbers and can be reused or changed. And since they are not in a standardised format, they are not considered as secure when it comes to traceability and are therefore registered as additional information to other cargo information, but are nevertheless necessary.