1. A method for on-road vehicle detection comprising the steps of: receiving a video sequence comprised of a plurality of image frames; identifying a potential vehicle appearance in an image frame; using known vehicle appearance information and scene geometry information to formulate initial hypotheses about vehicle appearance; tracking the potential vehicle appearance over multiple successive image frames; identifying potential motion trajectories for the potential vehicle appearance over the multiple image frames; applying knowledge fusion of appearance, scene geometry and motion information models to each image frame containing the trajectories; calculating a confidence score for each trajectory; and determining that a trajectory with a high confidence score represents a vehicle appearance.