1 : An obstacle detection method, comprising: (a) provisioning a vehicle with a camera having an external field of view; (b) acquiring a set of image frames provided by the camera whilst the vehicle is in motion, the image frames defining an image plane having a vertical aspect and a horizontal aspect; (c) determining one or more objects present in the set of images frames by edge detection; (d) determining the relevancy of an object by (i) selecting first and second feature points from the object contour that are spaced apart vertically in a first image frame, (ii) tracking the positions of the first and second feature points over at least a second image frame, and (iii) deciding the object to be relevant if the first and second feature points move dissimilar distances in physical space, within a tolerance, and deciding the object to be irrelevant otherwise; (e) estimating the motion of relevant objects to determine if any relevant object is likely to become an obstacle to the vehicle.