At this scale, you probably won't see much texture on the road, so the lengthwise little 2-3px shadows probably aren't needed, they feel a bit noisy. You can still imply the texture of the road at its edges, and with the edges of colours, the way you're doing with the grass.
Try to keep the grass the same scale around the road as you have it elsewhere. So, don't shade it. If the grass blades aren't very visible, that's fine, because they still do their job of breaking up the silhouette.
You could also vary the road's colour in different areas, to show the different materials, such as near the top where it should probably be bluer. Your palette seems to allow for it.
If you want a more natural look, then consider taking the "perspective" into account, i.e. making the horizontal stretches narrower than the vertical ones. You could also make the road more winding in general, with more obstacles for it to get around, plus more minor width variations where the grass/snow/whatever just happen to creep in a little more.
