We present Road Rager, a prototype built in order to explore our hypothesis that proximity and a possibility to identify other players during temporary encounters could spur social interaction and enhance a mobile gaming experience. In this case, it is a multiplayer game designed to enable passengers in different cars to play against each other during a meeting in traffic. Using such meetings as resource opens new interesting possibilities for novel and engaging mobile experiences. In this paper we present the game concept, the implementation and the possibilities to interact - designed to successfully benefit from the dynamic and vivid mobile context created during a traffic encounter. We also present a technical test and some initial user feedback on the gaming experience. Categories and Subject Descriptors H.5.1 [Information Interfaces and Presentation]: Multimedia Information Systems - Artificial, augmented, and virtual realities; H.5.2 [Information Interfaces and Presentation]: U...