Data dissemination and data collection to/from vehicles traveling on city roads are key features to fully enable the advent of Intelligent Transport Systems and Autonomous vehicles. Both Road Side Units and On Board Units need to disseminate different kind of data to vehicles or to collect data sensed by the vehicles themselves and transfer them to road monitoring and control centers. In this work we propose a protocol, named DISCOVER, that disseminates and collects the data of interest in a quite large city area efficiently and timely by using a single network structure, i.e., a multi-hop backbone made up only of vehicles nodes. DISCOVER is distributed and adaptive to the different traffic conditions, i.e., to the different levels of vehicular traffic density. Several numerical results show that it attains very good performance in different type of city maps (New York, Paris, Madrid and Rome) when compared with baseline approaches as well as when compared with a theoretical bound.