Abstract: Regarding to the requirements for effectively traffic incident management on freeway with the knowledge of previous emergency cases,an ontology based model of freeway traffic emergency cases is constructed.This model provides a unified semantic representation of the development stages of freeway traffic incident as well as the handling processes,among heterogeneous systems deployed in different areas or departments of freeway;and better facilitate the sharing and application of the knowledge of previous emergency cases.To illustrate the usage of this ontology based model,a freeway traffic emergency cases sharing system is sketched,and a typical traffic emergency case is formally described as an ontology instance for joint emergency rescue on freeway.