At present, overtaking accidents on highway frequently occur with serious consequences. Aiming at this problem, a warning model is proposed for preventing overtaking safety. First, the main factors influencing the safety of overtaking are analyzed. Next, overtaking collisions are categorized and overtaking scenario is developed. Then, by describing overtaking trajectories and by using a kinematic model of vehicles, a warning model of preventing overtaking collisions is established, which includes a critical longitudinal safety spacing model and a time-spa-cing model. Finally, the effectiveness of the model is verified by using two instances, namely, constant-velocity overtaking and specific-acceleration overtaking.