Highly automated, cooperative driving vehicles will allow for a more fluid flow of traffic, resulting in more efficient, eco-friendly and safe traffic situations. The automotive industry however, is safety critical and current safety standards were not designed to deal with cooperative driving. In this paper, we apply a modern safety analysis method, Systems-Theoretic Process Analysis, in the context of cooperative driving as part of the Grand Cooperative Driving Challenge (GCDC) and present our reflections on the method.