Ground has a base texture, and then decal overlays to create the paint stripes on asphalt roads and dusty tire tracks on dirt roads. I use the color texture to create fake specular maps, because it provides more variation to the shine. But, intially I didn't include the ground decals. After shuffling some code around, the decals are added to the color texture mix before I make fake specs from it, so now the paint stripe running down the road pops as it has more shine coming off it. The fake spec is simply a grayscale of the color (an average of the RGB values). So, white creates a brighter grayscale than the gray asphalt road, thus making the white paint stripe reflect more light.