Wireless Mobile Ad Hoc Networks are particularly vulnerable due to their fundamental characteristics such as an open medium, dynamic topology, distributed cooperation, Vehicle - to - vehicle / vehicle - to - infrastructure (V2X) communication systems are envisioned to greatly improve road safety, traffic efficiency, and driver convenience. However, many V2X applications rely on continuous and detailed location information, which raises location privacy concerns. A multitude of privacy protection mechanisms have been proposed in recent years. However, few efforts have been made to develop privacy metrics, which can provide a rigorous way to assess the privacy risk, evaluate the effectiveness of a given mechanism, and exploit the full possibilities of protection methods in V2X systems. Therefore, in this paper we present a trip-based location privacy metric for measuring user location privacy in V2X systems. The most distinguishable aspect of the metric is to take into account the accumulated information, which is the privacyrelated information acquired by an adversary for an extended period of time, e.g., days or weeks.