Managing user mobility is historically one of the most critical issues in cellular radio access networks (RANs). That task will become an even greater challenge due to cellular users on board vehicles and networked cars that autonomously access Internet-based services, whose number is expected to grow dramatically in the next few years. There is thus a need to characterize RAN access from/by vehicles in a similar way to what has been done for traditional pedestrian access. In this paper, we propose a study of the macroscopic and microscopic features of pervasive vehicular access in a case-study large-scale urban environment in the presence of realistic data sets of the road traffic and RAN deployment. We find that pervasive vehicular access is characterized by unique temporal and spatial variability in the urban region, such that it may require a dedicated RAN capacity planning: The presence of stable vehicular access load patterns and mobility flows can help to that end. Moreover, we identify the theoretical distributions that best fit key metrics for RAN planning, i.e., the vehicular users' interarrival and residence times at cells, and discuss how their parameters vary over time and space.