This International Standard determines general technical details related to the access layer of the ITS station reference architecture specified in ISO 21217 which are applicable to all or several access layer technologies. This includes especially the service access point (SAP) of a communication interface (CI) as provided by the communication adaptation layer (CAL) for communication. The SAP provided by the CI management adaptation entity (MAE) for management of the communication interface is specified by reference to ISO 24102-3.