The fast and economical prototype development of (vehicular) antenna systems requires the employment of feasible simulators. This article describes such a simulator for vehicular communications. The channel model used is based on stochastically or deterministically generated 3-D environments that include a realistic traffic model. The wave propagation is calculated with a fully polarimetric ray tracing tool. In addition, an antenna synthesis method for predefined time-variant communication scenarios has been proposed. The major emphasis has been put on MIMO systems, but in general, the algorithm can be employed for multiple-element as well as single-element antenna systems.