In a method and apparatus for determining a classification boundary between an object, such as a vehicle, and a background, using an object classifier, a trained classifier is configured to classify and recognize each of a plurality of object images and a plurality of background images. Next, a confidence probability density distribution function is calculated for the vehicle and the background using the determined confidence values for the vehicle images and background images. Once the probability density distribution functions for the vehicle and the background are calculated, the classification boundary between the vehicle and the background is determined using the probability density distribution functions for the vehicle or the background, or both, and a predefined model that is appropriate.