Vehicular Ad Hoc Networks (VANETs) are composed of vehicles equipped with advanced wireless communication devices. As a paradigm of decentralized advanced traveler information systems (ATIS), VANETs have obtained interests of researchers in both communication and transportation fields. The research in this chapter investigates several fundamental issues, such as the connectivity, the reachability, the interference, and the capacity, with respect to information propagation in VANETs. The authors’ work is distinguished with previous efforts, since they incorporate the characteristics of traffic into these issues in the communication layer of VANETs; this mainly addresses the issue of the interference. Previous efforts to solve this problem only consider static network topologies. However, high node mobility and dynamic traffic features make the interference problem in VANETs quite different. To investigate this problem, this chapter first demonstrates the interference features in VANETs incorporating realistic traffic flow features based on a validated simulation model. Then, analytical expressions are developed to evaluate the interference under different traffic flow conditions. These analytical expressions are validated within the simulation framework. The results show that the analytical expressions perform very well to capture the interference in VANETs. The results from this work can facilitate the development of better algorithms for maximizing throughput in the VANETs.