This International Standard provides a definition of the primary services and application areas that can be provided to Intelligent Transport Systems (ITS) Users. Those with a common purpose can be collected together in ITS service domains, and within these there can be a number of ITS service groups for particular parts of the domain. This International Standard identifies 11 service domains, within which numerous groups are then defined. Within this framework, there are varying levels of detail related to definition of different services. These details differ from nation to nation, depending on whether the specific national architecture building blocks are based directly upon services or on groups of functions. Thus, the intent is to address groups of services and the respective domains within which they fit. As these domains and service groups evolve over time, it is intended that this International Standard be revised to include them. This International Standard is applicable to the working groups of ISO TC 204 and other TCs which are developing International Standards for the ITS sector and associated sectors whose boundaries cross into the ITS sector (such as some aspects of urban light railways, intermodal freight and fleet). This International Standard is designed to provide information and explanation to those developing ITS International Standards and to those developing specifications, implementations and deployments for ITS. This International Standard is advisory and informative. It is designed to assist the integration of services into a cohesive reference architecture, assist interoperability and common data definition. Specifically, services defined within the service groups will be the basis for definition of use cases and the resultant reference architecture functionality, along with definition of applicable data within data dictionaries, as well as applicable communications and data exchange standards.