The telematics field is highlighted as one of the fields of application for wireless sensor networks. In this paper, we introduce a collision warning system for the convergence of telematics and wireless sensor networks technologies, and we explain several requirements needed for designing such a convergence service. Then, we propose a service system that can satisfy the requirements of 1) event driven operation, 2) deployment considering road structure, and 3) routing schemes considering data characteristics. We implemented the system and show the field test results of the system. It is expected that this service system can be helpful as a proper reference for converging telematics and wireless sensor network technologies.