jfugate, a member of this Forum, makes excellent asphalt roads from styrene. They are HO but the method is applicable to N. The link below is to an article on his web site telling how he modeled a rural highway. http://siskiyou.railfan.net/model_rod.html
Styrene can be used to make curbs and sidewalks too. Evergreen makes scribed sheets with retangular grids (in a number of different spacings) that can be used to make sidewalks.
I tried to sell my two cents worth, but no one would give me a plug nickel for it.
I don't have a leg to stand on.
Don Agne