1. A method for detecting a side window of a vehicle, said method comprising: calculating a spatial probability map that includes data indicative of likely side window locations of a vehicle in an image; running a side window detector with respect to said image of said vehicle to determine a plurality of detection scores; weighting said plurality of detection scores based on said spatial probability map; extracting a detected region from said image as extracted patch of said image; and performing an image classification with respect to said extracted patch to provide a classification that indicates whether or not a passenger is in a rear seat of said vehicle or no-passenger is in said rear seat of said vehicle.