1. A method for detecting a vehicle moving relative to, and in proximity to a moving host vehicle comprising the steps of: providing a first detector on said host vehicle, said first detector for detecting said moving vehicle in a target area which is stationary relative to a road at a first time; providing a second detector on said host vehicle, said second detector for detecting said moving vehicle in said stationary target area at a second time; providing a control system for receiving outputs from said first and second detectors; comparing said outputs at said first and second times to verify the presence of said moving vehicle in said stationary target area; recording said outputs at said first and second times; averaging said outputs; and adjusting said outputs using said averaged outputs to compensate for changes in said outputs not originating from said target vehicle.