The connected car concept is gaining momentum from the point of view, not only of research, but also of standardization and industrial development. Today there are many options for connecting a vehicle, in terms of to whom and how. In addition to making use of any conventional cellular technology, and connecting the vehicle to a base station or infrastructure element, vehicles can connect wirelessly and directly to each other using different technologies, both from the Institute of Electrical and Electronics Engineers (IEEE) and from the 3rd Generation Partnership Project (3GPP). This article offers a rigorous and detailed review of the system architecture aspects involved in the support of vehicular communications by the 3GPP fifth-generation (5G) standard, with special emphasis on its most recent iteration: Release 16.