This paper presents path loss model along with framework for probability distribution function for VANETs. Furthermore, we simulate three routing protocols Destination Sequenced Distance Vector (DSDV), Optimized Link State Routing (OLSR) and Dynamic MANET On-demand (DYMO) in NS-2 to evaluate and compare their performance using two Mac-layer Protocols 802.11 and 802.11p. A novel approach of this work is modifications in existing parameters to achieve high efficiency. After extensive simulations, we observe that DSDV out performs with 802.11p while DYMO gives best performance with 802.11.