Detect lanes from a filtered image
Finding shapes / lines is a good idea. Threshold tweaking is almost certainly a bad idea.

Hough transform typically expects your lines to be (1) in a binary image and (2) of one pixel width. Try to apply an edge detector (Matlab: edge) on your filtered image in order to get the boundaries of your white regions as one-pixel lines. Then Hough transform should find something.

I would also consider doing edge detection on your original image rather than your feature image. Then you can try to tweak the edge detector, rather than first running your "certain operations" and then detecting edges.

Once you have some lines you will face the problem of finding the good ones. You could look at (i.e. google for) "vanishing point detection", and read about RANSAC.