Lane detection and tracking using B-snake?
Following my comment I suggest you a "dumb" heuristic you could try : Consider your images row-wise. Extract a few features from each row, these could be average RGB value, RGB covariance matrix, entropy etc ... Use a simple clustering algorithm to separate your image into 2 parts : the upper one and the lower one. Let's assume the heuristic has been successful and the lower part is mostly composed of road. We'll just consider this part and run a clustering algorithm on the RGB values. We keep the number of cluster low and we want to take the cluster which is the closest from grey as the road cluster. Once you have a not too bad road segmentation, play around a bit with edge detection to extract only the white marking.