An anticipatory crash sensor for actuation of deployable passive restraint systems has been developed. The system consists of a 10 GHz continuous wave (CW) doppler radar. In operation, position discrimination is achieved through use of separate receiving and transmitting antennas, located on opposite sides of the front of the vehicle. An object is detected only when within the region of overlap of the two antenna patterns. Velocity discrimination has been achieved very simply in both digital and linear realizations. A threshold circuit permits adjustment of the minimum target size to which the sensor will respond.A variety of circuit and antenna configurations has been examined and constructed to obtain optimal system performance. These include hybrid systems which make use of mechanical confirmation of impact in an intermediate speed range, and more elaborate antenna configurations. Characteristics of typical targets have been determined experimentally. In addition, studies are being carried out to permit preliminary estimates of cost and reliability for production sensors, and-using available accident data-to indicate the probable effectiveness of such systems.