# An Overview of Cooperative Driving in the European Union: Policies and Practices
## 1 Introduction  
Cooperative-Intelligent Transportation Systems (C-ITSs) represent the set of technological and functional elements that allow specific communication tasks identified as V2X (i.e., vehicle to everything) communication services. The 'X' in V2X can identify another vehicle (i.e., V2V communication) or the infrastructure (i.e., V2I communication). In some approaches, 'X' is also used to identify the cloud. The primary goal of such technologies is to improve road safety by helping the driver make the right decision and adapt to traffic conditions, thereby avoiding potential harm. This clearly means abating road fatalities and injury severity. Under the perspective of a progressively growing level of driving automation, these technologies could be directly exploited by the vehicle without the intervention of the driver. Other potential benefits of the use of C-ITS include enhanced traffic efficiency and improved driving experience. Indeed, the use of V2X technologies is assumed to reduce congestion and make driving tasks less reliant on human action. Finally, they can ensure environment-friendly driving through in-vehicle technologies (e.g., eco-driving), and smarter transportation management at the network level. As stated above, communication and cooperation among vehicles and between vehicles and infrastructure are crucial for the safe integration and operation of automated vehicles in transport systems of the future.  
Within this framework, both the vehicles and the infrastructures have to be smart agents, and a reliable communication channel between them needs to be built. Therefore, C-ITS development has two main levers: enrichment of in-vehicle technologies and infrastructural development. Other crucial elements concern regulations, service standardisation, and cyber security issues.  
Community legislation is paying great attention to the matter. In March 2019, a delegated act supplementing Directive 2010/40/EU was released [1]. Specifically, this new regulation concerning Cooperative-Intelligent Transport Systems is planned to enter into force and be directly applicable in all Member States from 31 December 2019. In light of the above, this paper aims to provide a concise (but comprehensive) overview of the current state of C-ITS testing and development activities across the European Union (EU). The challenge is to collect, examine, and summarise the countless sources available in their most diverse forms. Indeed, not only have official documents describing standards and project reports been consulted, but press releases, online articles, and datasheets have also been examined, amounting to more than 2000 pages. The goal consists in identifying C-ITS definitions, implemented technologies, level of readiness of different kinds of services (i.e., some of them are ready to be deployed while others require additional research and experimental phases), operating consortia, infrastructural development and other relevant factors, and presenting them in a synoptic and straightforward way. Clearly, although our review pays particular attention to the European case, it is worth noting that similar phenomena are occurring in the USA, Australia, and in the Far East.  
The remainder of the paper is organised as follows: Section 2 describes the key features of the C-ITS European framework; Section 3 illustrates the basic principles of cooperative services and technologies; Section 4 outlines the best practices across the EU; finally, Section 5 provides the concluding remarks, including lessons learned and future perspectives.