Vehicular communication systems are an emerging form of communication that enables new ways of cooperation among vehicles, traffic operators, and service providers. However, many vehicular applications rely on continuous and detailed location information of the vehicles, which has the potential to infringe the users' location privacy. A multitude of privacy-protection mechanisms have been proposed in recent years. However, few efforts have been made to develop privacy metrics that can provide a quantitative way to assess the privacy risk, evaluate the effectiveness of a given privacy-enhanced design, and explore the full possibilities of protection methods. In this paper, we present a location privacy metric for measuring location privacy in vehicular communication systems. As computers do not forget and most drivers of motor vehicles follow certain daily driving patterns, if a user's location information is gathered and stored over a period of time, e.g., weeks or months, s...