the sidewalks are Strathmore board available at art supply stores. The generic name is artist illustration board. it cuts with a razor - even on a 45 degree angle. so i make the roads with it too. I raise the road center with strips of balsa wood so the road has a 'crown' to the center.
i seal with spray can clear lacquer then add texture gray to the road folloed by darker chalk powders.
sidewalks are scored every 4 feet or so with section lines and colored with concrete color then add character with various chalk powders. sidewalks are layered over the road and the excess gives a slab floor for under the buildings.
i hope all that makes sense. go to
www.cspmovies.com and find the tab on the left called "model Railroad" and go to the slideshow there. you can see some of the photos there of streets in better light.