Car-to-car and car-to-infrastructure communications are considered as a key technology for safe and intelligent mobility in the future. In the German project simTD, car-to-x communication is shifting from a pure research topic toward a first deployment of such a system: the goal of simTD is to test car-to-x applications in a real metropolitan field trial. The simTD scenario includes vehicles, roadside units, and infrastructural facilities for traffic and test management. Besides these domains, several third parties are involved to provide access to additional services. The main communication partners are furthermore distributed over a wide area including highway, suburban, and urban scenarios. As a result, such a system requires a commonly accepted architecture of the individual components and a seamless communication network for reliable and efficient information interchange. In this article we propose the simTD system architecture and the components necessary for successful deployment in the large-scale field trial.