A method and apparatus for preparing a moving vehicle for impending impact with another vehicle or object which incorporates the extending of the air bag to fill in the space between an extendible bumper. A detection apparatus senses a dangerous speed of the vehicle or an approaching object in the path of the vehicle and extends the bumper forwardly or rearwardly from the body of the vehicle while at the same time filling the space between the body and bumper with an inflated air bag. Should the impact not take place, or the dangers facing the vehicle have decreased, the apparatus retracts to its initial inoperative condition. One form incorporates a first filled bag which is filled at all times, and then a second bag which is inflated when the bumper is extended. A modified form moves an elongated bag into position with its longer dimension filling the space between the body of the vehicle and the bumper, and correspondingly returns the bag so that its shorter dimension fits in between the retracted bumper and the body of the vehicle.