# Review of V2X-IoT Standards and Frameworks for ITS Applications
## 1 Introduction  
The transport sector is one of the most important economic sectors and sources of income, both in Europe and globally. The European Union (EU) transport sector alone (services, manufacturing, maintenance, construction, etc.) generates more than 9% of EU gross value added (GVA), with transport services alone representing 5% which is equal to EUR 662 billion. More than 20 million people work in this sector, making up more than 9% of the EU workforce [1]. However, a rapid development of this sector faces significant challenges and problems: ways of reducing the number of crashes of road and air transport, greenhouse effect caused by gas emissions, the dependency from fossil fuel, ways of maximizing and effectively exploiting vehicles as well as increasing the skills of the drivers, and many other important and relevant issues. One way to address the latter problems of the transport sector is to create and introduce an intelligent transport system (ITS). It is hard to clearly define what ITS is, however, these systems are often understood as the use of information and communication technologies in transport to solve various problems in the transport sector. For these reasons, the term ITS may cover a very wide rangeof transport sectors. As a term, it has been approved and has been officially used in the USA and Japan since 1991, and in Europe, since the year 1994 in the First ITS World Congress held in Paris, France [2]. By far one of the most essential problems from those listed above, which is present in all countries worldwide, is the aim to reduce the number of fatalities and casualties in road accidents. For example, only during 2018, 25,100 people died on the EU's roads, which is 200 less than in 2017 (-1%) and 6400 less than in 2010 (-21%) [3]. While this trend is encouraging, it may be too small to achieve the EU goal of halving the number of road deaths by the period of 2010-2020, and having zero road deaths by 2050 (\"Vision Zero\") [4; 5]. In addition, it is estimated that there were over 135,000 seriously injured people, among whom, a large proportion was of vulnerable road participants in 2018: pedestrians, cyclists and motorcyclists [3]. Deaths and road injuries affect not only the victims but also society as a whole and its economic development. It is estimated that the EU socio-economic costs, which are devoted to the rehabilitation and healthcare of injured persons, compensation for victims and other areas, reach EUR 120 billion per year [6]. Additionally, there are other occurrences of losses due to time spent in traffic jams, the amount of fuel consumed and increased air pollution. For example, traffic jam-related problem costs in Europe are estimated to amount to more than EUR 130 billion every year [7]. Trends and statistics show that the number of vehicles in Europe is annually growing (the increase in passenger vehicles: 1-2%, goods transportation vehicles: 4-7%). The potential for urban infrastructure development is limited and, as the number of vehicles grows, the problem of traffic jams in cities will become more and more relevant. For the latter reasons, these challenges will only continue to increase unless drastic new political and technological measures are taken. In order to address the above-mentioned problems, both automotive and communications companies, as well as science and government institutions worldwide, are working to develop a variety of vehicle communication networks. There can be different vehicle communication Network types depending on the participants that exchange data. Networks, consisting of mobile nodes which are strictly moving vehicles communicating directly with each other, are called vehicle-to-vehicle (V2V). Vehicle-to-infrastructure (V2I) or pedestrians (V2P) networks are formed when moving vehicles communicate with either roadside infrastructure or pedestrians. If the vehicle communicates with IT networks and/or data centers, the network type becomes vehicle-to-network (V2N).