Hi VinnyV123,
I have been doing this train thing for about twenty years now. If you are talking about asphalt or concrete roads then Woodland Scenics system of foam tape and plaster works very well. It is easy to put down and can be configutered to any shape. It takes paint very well and give the surface great texture.
I have also use styrene, cardstock, tile grout(two heavy and hard to work), and pre-printed road sheets. In my hands none of these other options gave as realistic a looks as the plaster.