1. A method of detection of a structural barrier extending along a road, the method performed by a driver assistance system mountable in a host vehicle, wherein the driver assistance system includes a camera operatively connectible to a processor, the method comprising: capturing a plurality of image frames in the forward field of view of the camera; in the image frames, locating an image patch suspected to include an image of part of a structural barrier; and processing image motion of said image patch of the structural barrier to compute a lateral distance between the host vehicle and said image patch using the image motion of said image patch and motion of the host vehicle, the image motion of said image patch comprising mapping coordinates of an image from image frame to image frame or a function of the mapping, thereby detecting the structural barrier while avoiding use of a second sensor other than the camera to sense the structural barrier.