IEEE 802.11p was released as the standard for wireless access in vehicular communication. In this paper, we introduce an 802.11p performance evaluation method based on realistic transmission simulations in Matlab. The vehicular propagation channel was measured beforehand using the wideband HHI Channel Sounder. We conducted channel sounder measurements of oncoming traffic at two different highway sections. The proposed method allows the execution of sample-based transmission simulations with full access to the receiver signal processing and all insights of wideband channel impulse responses. We compute mean packet delivery rates for different packet sizes and discuss the effect of the time-variance in a vehicular propagation channel on the transmission success.