Vehicle location, voice call or vehicle delay/advance estimates are typical AVMS functions, why are they not described as AVMS services in the ITxPT architecture?
AVMS services are defined within the ITxPT architecture; not the AVMS system itself (this means the functional description).
In order to achieve integration of an AVMS system with other systems such as DPI, some specific services are required. For instance, ITxPT architecture describes how to subscribe to a DPI application in the on-board IP network to receive stop and journey information from the AVMS.
The way the AVMS locates the stops or the end of each journey (the location function itself) is an internal function of the AVMS as a system and not relevant to the ITxPT architecture.