If/When I do this again - Diolma was exactly right - this needs to be BIGGER!

4096 would have been better, and I would have made the road 100 pixels wide, while STILL keeping the yellow lines to 2 pixels. The bumps look pixellated because of the small sixe, etc.

I also would - after applying the picture as my terrain - done some sculpting in and around the moutnain/hillside to make it more "lumpy and natural in a Vue sort of way - and you can also paint Effects as well so you won't accidentally apply a Fluvial Effect to the roads in the terrain.

This could also be done as 2 terrains - copy the initial terrain created with the picture - the first one erase the roads and paint hills and erosion, etc. In the second one, erase the hills and keep the road. If you apply and Ecosystem to the first one you could go further in realism while just using the Color map for the second one (the road).

Good luck and I hope this helps-
-Lew ;-)