Developing real-time safety and non-safety applications for vehicular ad hoc networks (VANETs) requires understanding the dynamics of the network topology characteristics since these dynamics determine both the performance of routing protocols and the feasibility of an application over VANET. Using various key metrics of interest including node degree, neighbor distribution, number of clusters and link duration, we provide a realistic analysis of the VANET topology characteristics over time and space for highway scenario. In this analysis, we integrate realworld road topology and real-time data extracted from the Freeway Performance Measurement System (PeMS) database into a microscopic mobility model to generate realistic traffic flows along the highway. Moreover, we use a more realistic, recently proposed, obstacle-based channel model and compare the performance of this sophisticated model to the most commonly used more simplistic channel models including the unit disc and log-normal shadowing models. Our investigation on the key metrics reveal that both log normal and unit disc models fail to provide realistic VANET topology characteristics. We therefore propose a matching mechanism to tune the parameters of the lognormal model according to the vehicle density and a correlation model to take into account the evolution of the link characteristics over time. The proposed method has been demonstrated to provide a good match with more sophisticated but computationally expensive and difficult to implement obstacle based model and validated over the real data of two different highways in California.