In recent years,traffic accidents caused by vehicle lane changing on highways or fast roads have becomefrequent and have caused serous consequences.Aiming at this problem,a lane changing pre-warning model for high-ways is proposed in this paper.First,the process and motivation of lane changing are described.Next,the simulationscenario of lane changing is designed,and the possible vehicle collision types are analyzed.Then,the position rela-tionship between the lane-changing vehicle and the adjacent vehicles are discussed on the premise of avoiding anycollision,so as to find out the critical position of a vehicle collision.On this basis,a safe distance which can be usedto avoid vehicle collisions is presented.Finally,the proposed model is proved to be correct by an example of lanechanging in uniform motion.