A comprehensive implementation of the envisioned traffic safety and efficiency applications of the IEEE 802.11p and Wireless Access for Vehicular Environments (WAVE) standards assume the premise of the use of Dedicated Short-Range Communications (DSRC) technology both as on-board units and as roadside units (RSUs). The high cost associated with RSUs, however, has so far prevented massive deployment of RSUs. Finding alternative solutions to this longstanding problem is therefore very important. In this paper, we propose a self-organizing network approach to using parked cars in urban areas as RSUs. This self-organizing network approach enables parked cars to create coverage maps based on received signal strength and make important decisions, such as if and when a parked car should serve as an RSU. Our results show the feasibility and cost-effectiveness of the proposed approach, which is able to provide excellent coverage using only a small fraction of the cars parked in a city.