In this paper, a User-Based model is proposed to analyze and evaluate the performance of IEEE 802.11p MAC protocol for vehicular safety applications that can save lives and improve traffic flow. The proposed model provides a complete stability analysis compared to the Markovian models. Moreover, it provides a means for conducting further analysis on the design parameters of the protocol, leading to an optimization methodology which indicates how IEEE 802.11p should be configured for improved performance. The model is cross validated against simulations; the IEEE 802.11p can meet the needed latency and reliability requirements for the delivery of safety messages under the Finite user model, however, it fails to satisfy such requirements under the Infinite user model.