In this paper, we present a new speed advisory system (SAS). The system provides indications to drivers which, if followed, guide the network of vehicles towards a common speed. The SAS we present is distributed and one of its key features is that the vehicles are guided towards the common speed by receiving obfuscated information. Essentially, this means that the desired network behaviour is achieved and, at the same time, there is no vehicle in the network that obtains clear knowledge of the state of any other vehicle. This results in a privacy-preserving feature which is particularly useful in smart cities applications, where drivers might not be willing to share their transient state with others.