Vehicle-to-anything (V2X) is a promising communication technology to support operability in large-scale vehicular networks. The future deployment of V2X necessitates interworking between different access technologies, i.e., Dedicated Short-Range Communications (DSRC) and Cellular networks. However to achieve an efficient V2X interworking, we need to resolve the multi-hop issue, mainly originating from the V2X hybrid architecture. To resolve this issue and consequently to analyze the interconnected system, characterizing the output process of IEEE 802.11p-based DSRC protocol is of a fundamental importance. This paper proposes stochastic Regenerative Model to provide a complete description of IEEE 802.11p output process. The accuracy of the model is verified through extensive simulations. As a case study, the proposed model is compared with the Poisson model in the performance evaluation of V2X interworking. Numerical and simulation results verify the ability of the Regenerative Model to capture the deviations of the actual output process of IEEE 802.11p under different traffic intensity as compared to the Poisson model.