You can add another wall on top of that wall by duplicating a wall that follows the contours of the track surface. Then adjust the shape so that the wall does not rest on ground but hovers above the other wall.
Another way is to include extra points on your original wall shape. Then reshape that piece how you want it above the wall, then remove the texture from that part and replace the texture with a fence wire mesh.
you can also make a cross section which is an easier way of doing it click on the link below go to forward it to 3 min 50 sec........when it's intalled on th track edit the materils for it and change them for the materials you want
Thank you guys very much. Is there some folder im suppose to put the textures in because im gettiin a gmotr2 error when i try to open the track in rf. Also how do i add terrain to the terrain already added around the track. It keeps starting from the edge of the track everytime Sorry if these are dumb questions this is my first track