the deployment of tens of thousands of RSUs embedded or attached to roadway infrastructure to enable an effective network along the country roads. This would be a challenge in rural areas considering the vast distances involved. State high- way administrations and other highway authorities would be responsible for deploying, managing, and operating the RSUs and the associated infrastructure network and inter- connections such as fiber or copper backhaul. After considering how to map each V2V ser- vice to different 3GPP technologies, the conclusion is that Rel-14 is only used for basic safety, while NR-based V2X is used for advanced services to avoid duplication or replace- ment of LTE-based Rel-14 functionalities. Therefore, it is expected that in the beginning of the V2X service deployment, there will be LTE-based Rel-14 V2X devices which later evolve into dual-mode UEs that support both LTE and NR V2X services. Several V2X use cases require vehicles to communicate with an infrastructure. The DSRC security relies on a public key infrastructure that distributes and manages digital certificates for vehicles. This means that vehicles need to have access to this infrastructure, which in Chapter 7 the case of DSRC is provided via the RSUs. The RSU may also be used by vehicles to com- municate with the V2X application server. Owing to various factors, the deployment of RSUs might be limited. It is therefore unrealistic to expect the provision of ubiquitous COV- erage of roadways via DSRC equipment in near future. One challenge with the deployment of V2X technologies is that there is uncertain business incentive for network providers. In the United States, where V2V deployments may be mandated, there is still lack of clarity regarding the plan to implement the infrastructure that would utilize the balance of the channels, and which entities should manage the security network functions. Since govern- ment funding has been a driving force for many V2X pilot programs, it is unclear if com- mercial business models can be a