The tradeoff between the connectivity and the coverage area has been a crucial challenge to investigate, in order to design effective vehicular network deployments in urban areas. Generally, in order to increase and scale the connectivity among vehicles, the radio transmission range needs to be extended. In both Vehicle-to-Vehicle (V2V) and Vehicle-to-Road Side Units (V2R) deployments, the increase in the number of Road Side Unit (RSU) and/or On Board Units (OBU) can also extend the network coverage area. However, these solutions can be possible with extra deployment costs. Beside that, due to the generic high mobility characteristics of vehicles, they cannot maintain a robust connection for a long time even though there are enough nodes to relay the transmission, leading a decrease in the network connectivity. To solve this challenge between the coverage area and the connectivity, in this paper, we propose a relay based coverage area model that uses already connected vehicles as a relay between disconnected vehicles and RSUs. Disconnected vehicles run the proposed neighbor discovery algorithm to setup a connection with already connected vehicles around their radio transmission range. Our algorithm builds dynamic neighbor maps and provides an optimal relay node to the disconnected vehicles. Therefore, the connectivity is increased neither changing the transmission range nor increasing the number of RSUs. Moreover, the proposed neighbor maps provide accurate location information, thus V2V and V2R connections can be built and sustained without the need of Global Positioning system (GPS) information, which can be misleading for many urban area scenarios due to the topological disorders. The through evaluations of the proposed algorithm show that our mechanism provides similar extension effect with enhancing of RSU transmission range two times.