Vehicular safety communication promises to prevent accidents by enabling new assistance systems. The information exchange is mostly foreseen to be handled via decentralized Dedicated Short Range Communication (DSRC). But, the required information could also be exchanged via cellular networks, potentially providing better coverage. The ability of cellular systems to handle the additional traffic is an open question. The introduced network load heavily depends on the number of communicating vehicles per cell. In this paper, we predict the number of communicating vehicles per cell. First, we analyze the coverage area of existing cells in the City of Munich. Second, we match street layout and traffic flow data with cells. The study shows that over 600 vehicles per cell might be reached. The resulting numbers are primarily discussed with regard to the communication demand of a cross-traffic assistance system. However, the results can also be used to predict load as introduced by other vehicular applications that communicate via cellular networks.