# An Overview of Cooperative Driving in the European Union: Policies and Practices
## 2 The European Framework
Further, typical services developed for urban applications are: _loading zone management_ (LZM), which is conceived for supporting the management of urban parking zones specific to freight vehicles, with benefits for drivers, fleet managers and road operators; _zone access control for urban areas_ (ZAC), which is targeted to provide information about access restrictions to specific urban areas, thus allowing drivers to better plan their trip; and _vuherable road user protection_ (VRU), which is a safety-critical service to the benefit of vulnerable road users, i.e., pedestrians and cyclists. Finally, it is worth citing _connected and cooperative navigation_ (CCN), which represents an advanced C-ITS service for which no definitive descriptions have been released yet. However, it is based on a systemic framework in which tasks like the first and last mile, parking information, route advice, and coordinated traffic lights are fully synchronised and integrated. A more detailed description of the features and applications of the above-mentioned C-ITS services can be found in [9; 10; 11; 12; 13; 14; 15; 16]. Obviously, each of the services described needs to be supported by standardised messages and, as mentioned above, by suitable communication technologies. The European Telecommunications Standards Institute (ETSI) has defined two different kinds of messages, namely _cooperative awareness messages_ (_CAM_s) [17] and _decentralized environmental notification messages_ (_DENM_s) [18], with related packet formats and dissemination guidelines. Specifically, CAMs are a kind of heartbeat message periodically broadcast by each vehicle to its neighbours to provide information on presence, position, speed, temperature, and basic status. By contrast, DENMs are event-triggered messages broadcast to warn road users about a hazardous event. Both CAMs and DENMs are delivered to vehicles in a particular geographic region: in the immediate neighbourhood in the case of CAMs (single hop) and in the area affected by the event for DENMs (multihop) [19]. Two other kinds of standardised messages, generally disseminated by the infrastructure, are _signal phase and timing_ (_SPaT_) and _map data_ (_MAP_) [20; 21; 22]. The former concerns the status of traffic lights, prediction of duration and phases, data elements for prioritisation response, as well as permission linked to manoeuvres or to lanes; the latter provides information about road topology (such as topological definition of lanes for a road segment or within an intersection, links between the segments, and restrictions in lanes). To complete the picture, it is worth citing _in-vehicle information_ (_IVI_) messages [23; 24], which transmit to the vehicle static and dynamic data about infrastructure such as recommendations dictated by road signs and speed limit information. Further, V2X data exchange can occur by means of different kinds of technologies. The most mature communication technology is described by the standard ETSI ITS G5 [25]. It is a European set of protocols and parameters for short-range communication between vehicles and traffic infrastructure, which operates in the 5.9 GHz frequency band; not coincidentally, it is also known as dedicated short-range communication (DSRC). It is based on the IEEE standard 802.11 [26] (used for Wi-Fi) and its amendment 802.11p on wireless access in vehicular environments [27], which introduces several modifications to adapt the physical (PHY) layer and medium access control (MAC) sublayer to the requirements of highly dynamic vehicular environments. More details on this technology can be found in [28]. Up and coming alternative technologies consist of cellular communications; however, this technology cannot ensure a direct link since it needs to rely on the presence of the cloud and, hence, is not suitable for use in the case of safety-critical applications [29]. Nevertheless, in this regard, clarification is due. Strictly speaking, this holds for 3G and 4G networks.