For roads, lots, and pavement, sandpaper is your friend. You can easily trim it to any size and shape you want, from narrow road to large lot. You can cut it to fit between the rails for street running or grade crossings.
Start by selecting a grade of sandpaper suitable to what you're modeling. Fine is good for sidewalks and parking lots, while coarse is better for streets and roads. The extra thickness and height of the coarse paper also looks good at grade crossings.
If you're simulating a dirt road, the sandpaper is probably already the proper color. Otherwise, you'll want to paint the sandpaper with two coats of cheap craft store acrylic paint. For pavement or asphalt try shades of gray to dark gray. For concrete, use your eyes when selecting the paint. I use a shade called Bamboo.
After your painted sandpaper has been installed (cut and glued down), get creative with weathering. A technique I like is drydabbing. Like drybrushing, your paint brush has been wiped almost totally dry, with just a tiny amount of paint left, but instead of stroking use quick stabs and dabs. Drydab with colors just a shade or two removed from your pavement/concrete color.
I also like to use Bragdon weathering powders to simulate the soft streaks left on roads by tires and spills.
Finally, use a fine-tipped permanent marker to add cracks and tar patches.