Vehicular ad hoc networks, an emerging network platform based on vehicle-to-vehicle and vehicle-to-infrastructure communications, promise valuable applications to enhance driving safety, comfort, and efficiency. In this article we propose GPAS, a general-purpose automatic survey system based on VANETs. The key design motivation of GPAS is to explore the characteristics of data relevance in VANETs: location, time, and user interest. As a new mode to disseminate a survey and collect the required data/responses, GPAS can support a wide range of commercial and trafficrelated surveys in a secure, flexible, and cost-effective way. As a preliminary effort, the framework of GPAS is presented in this article together with indepth discussions on relevant research challenges and corresponding preliminary solutions.