This article proposes a model of car-to-car networks based on an adaptive self-organization overlay network. Car-to-car network is one of the promising ways to deliver the information and services among cars in order to increase the safety and reduce the traffic congestion. However, conventional works focus on the low-level communication protocols. Little works are done on the model and its nature of networks by connecting local networks without central control under changing communication environments. This article discusses modeling of car-to-car overlay networks based on the concept of self-organization and self-adaptation, and proposes a method and XML-based connection definition language V2VCL (Vehicle-to-Vehicle Connection Language) for generating the overlay network from the local connectivity. We discuss the effectiveness of proposed model with a scenario of car moving.