This paper analyzes how street-level traffic data affects routing in VANETs applications. First, we offer a general review about which protocols and techniques would fit best for VANET applications. We selected five main technical aspects (Transmission, Routing, Quality of Service, Security and Location) that we consider are differential aspects of VANETs from current Ad-Hoc Networks. Second, the paper analyzes how to configure each technical aspect according to the goal of a wide range of VANET applications. Third, we look at the routing aspect in depth, specifically focusing on how vehicle density affects routing, which protocols are the best option when there is a high/low density, etc. Finally, this research implements a sensor technology, based on an acoustics sensor that has been deployed around the city of Xalapa in México, to obtain reliable information on the real-time density of vehicles. The levels of density were discretized and the obtained data samples were used to feed a traffic simulator, which allowed us to obtain a global picture of the density of the central area of the city. According to the specific levels of vehicle density at a specific moment and place, VANET applications may adapt the routing protocol in a real-time way Peer Reviewed