This document is to establish a common framework to achieve unambiguous identification in ITS/RTTT: AVI/AEI applications. This scheme and Reference Architecture Model is designed to be an 'enabling' structure to allow interoperability between different commercial systems, and not prescriptive in determining any one system. It is not frequency nor air interface protocol specific, provides maximum interoperability, has a high population capability, and provides the possibility of upwards migration to more capable systems. This document provides a reference structure that enables an unambiguous identification and also identifies the data construct as an ITS/RTTT message. This is particularly important within an EDI environment. The construct also identifies which ITS/RTTT data structure is contained in the message. A wide variety of applications can be supported by the structure determined in this document, such as simple AVI/AEI, complex unambiguous ITS/RTTT messages (in either user identified or anonymous formats), or new and as yet undefined, message structures.