“…For monocular systems, the estimation of the distance of the vehicles is usually computed with a set of constraints such as flat road assumption, including methods based on the homography [15,16,18,20,22,34,37,52,53,61,66,94,98,99,110] and the use of augmented intrusion lines, patterns or regions [19,20,23,24,26,32,38,47,79,86,87,107,124], or by using prior knowledge about the actual dimensions of some of the objects (e.g., the license plates [41,49,60,66,68,80,125] or the size of the vehicles [42,62,78,103]). These restrictions are alleviated when using stereo vision [42,60,61,74,80,92,100,112].…”