Performance criteria are presented for head response of an anthropomorphic test device that is to be used for predicting the level of secondary impact force during frontal flexion. The criteria consist of all significant velocity response observed in a group of volunteers, thereby assuring that a dummy head with the proper mass distribution characteristics will possess the proper momentum at all times during unobstructed response to the primary impact imparted to the torso. A dummy with momentum or impact load predicting fidelity is an improvement over one which merely predicts contact.