Abstract: A signal proportional to steering angle is produced by a potentiometer controlled by the steering wheel, except for steering angles below about 0.1.degree. that are frequently used for corrections in driving on a straight course. For steering angles above about 0.5.degree., the signal remains constant in magnitude. The signal controls a range gate of the radar system suppressing the effect of echoes beyond a maximum range limit smaller than the intercept of a radar ray at the beam edge on an arc concentric with the curved path of the vehicle having a radius of curvature exceeding that of the vehicle path by a predetermined amount which is chosen so as to preclude reception of echoes from guard rails situated on the outside of highway curves.