The primary goal of this paper is estimate the power, due to other radar transmitters, expected to be incident on the receiving antenna of a given automotive radar, and secondly, simulate the impact this may have on the performance of an example radar system. The approach uses stochastic geometric methods to weigh the spatial, temporal, and spectral overlap, for realistic scenarios with multiple radars operating in proximity. The results show that a given radar receiving antenna may face more interference power (10 to 50 dB) than what is expected from the reference target used to specify system performance. Under these conditions, a radar system, without interference mitigation strategies, will likely suffer significant degradation in performance.