Abstract: Side detection radar utilized on a host vehicle for covering a blind spot in a vehicle mirror view produces alert commands resulting in signals which have gaps due to poor radar reflectivity of portions of a target. To fill these gaps to produce a steady alert signal when a target vehicle is in radar view and to extend the perceived zone of coverage, a variable sustain time is added to each alert signal which exceeds a threshold value. The sustain time varies as an inverse function of the relative vehicle speed and the threshold value varies as an inverse function of vehicle speed. If the alert signal is shorter than the threshold value, then a minimized hold time can be applied.