In times of increasing mobility and climate change, there is a need for new services to cope with the special challenges of electric vehicles, like e.g. recuperation and charging management. Established systems of so called smart traffic applications are usually server-based and bear the risk of uncontrollable gathering of private data by service providers. In this paper we propose a decentralized overlay protocol for smart traffic applications that meets the requirements of several scenarios of future traffic. Our system offers a scalable GeoCast service, where participants (e.g. vehicles) are able to gain information from specific geographic regions. In the following, we briefly describe three scenarios that would benefit from such a GeoCast service. After that, the main part of this paper discusses maintenance and privacy issues regarding the GeoCast overlay.