1. A method for providing a forward collision warning or control signal using a camera mountable in a motor vehicle, the method comprising: acquiring a plurality of image frames at known time intervals; selecting a patch in at least one of the image frames; tracking optical flow between the image frames of a plurality of image points of said patch to produce a tracked optical flow; for a plurality of models selected from the group consisting of: (i) a road surface model wherein a portion of the image points is modeled to be imaged from a road surface (ii) vertical surface model wherein a portion of the image points is modeled to be imaged from a substantially vertical object and (iii) a mixed model wherein a first portion of the image points is modeled to be imaged from a road surface and a second portion of the image points is modeled to be imaged from a substantially vertical object, fitting the tracked optical flow of at least a portion of the image points to produce a plurality of fits to the models; using at least a portion of the image points, scoring the fits of the tracked optical flow to the respective models to produce respective scores; and determining if a collision is expected and a time-to-collision by selecting the model with a score which corresponds to a best fit of the image points to the tracked optical flow.