In the real world, the accident ratio of rear impact is high. The injury scheme in those accident scenarios is mainly caused by whiplash. The intrusion of the rear end of the vehicle during impact combined with movement by occupants seated on rear seats plays a significant roll. This paper discusses an airbag which deploys from the roof header along the rear window. By means of numerical simulations and tests, the mitigation of biomechanical injuries of passengers seated on rear seats during rear impact was observed. Significant occupant protection was assessed under high-speed rear-impact conditions.