I use the YARN roads, modified without traffic and then place rails on the terrain. The road is deep enough to bury the tracks right up to the rails and gives the appearance of rails in the streets. This is great for those industrial areas and for street running operations found in various places. The older flat roads from the past tend to float above the surface and look odd, and it's difficult to get the tracks to stick through them easily.
I modified the textures of some non-traffic enabled YARN roads for cobblestones, sand, and gravel so that they can fit the appropriate setting. The cobblestone texture is great for factory yards and docks while the sand and gravel are great for cement plants and other places where a sandy surface is required.