Abstract: A radar sensor and a vehicle velocity sensor are mounted on a vehicle, producing three signals representative of, vehicle velocity, a distance and a relative velocity between the vehicle and an obstacle ahead thereof. These three signals are fed to a collision imminence computing circuit which generates two signals representative of collision imminences depending upon whether the obstacle is stationary or moving.

Abstract: A radar-operated collision avoidance system for a roadway vehicle comprises a radar device for sensing the vehicle speed relative to an object and its distance thereto to decide whether the vehicle is approaching the object at a dangerously high speed. A minimum allowable distance represented by a digital code is stored in a memory location within an array of rows and columns and read out in response to a sensed vehicle speed relative to the roadway and to a sensed magnitude of steering movement. The minimum allowable distance is compared with the distance sensed by the radar to determine that the decision is valid only when the latter is smaller than the former.

Abstract: Braking of a vehicle is prolonged by an improved logic circuit for a time or a distance to overcome stop starting braking due to momentary "safe" signals caused by multiple reflection of a radar signal.

Abstract: An automotive radar is provided with a device for sensing the location of the entry and exit ways of a zone as the vehicle passes therethrough to reduce the detectable range of the radar upon the vehicle entering the zone so that false targets within the range-controlled zone are discriminated from valid targets. The device restores the range upon the vehicle leaving the zone to normal range.