Proactive vehicle safety systems based on vehicle-to-vehicle and infrastructure-to-vehicle communication are promising new approaches to reducing the number of accidents on our roads. In-vehicle applications are envisaged to provide a variety of services to the driver including warning about potential collisions and other hazardous situations. For the safe operation of these applications it is important not only to efficiently model the environment but also to reason about, and predict, how reliable such a model is under various circumstances. In this paper we propose an approach to estimating the reliability and availability of the wireless medium at hazardous locations by cooperatively detecting communication disturbances in order to allow for more accurate decisions by in-vehicle applications.