I have to create a game level from a top down view of an area. I used a plane converted to an editable poly to do the job. I used edges to create the top view of roads, walkways and parks so that i can extrude/edit them later.

My problem is the curves in the road look blocky I tried appying mesh smooth modifier on the final model but that interfered with material mapping. Again i tried it on the plane without the extrusions and still the modifier does not work(The roads loose their shape). I know one way to solve the problem is to add more vertices on the curve and transform their location to create a more natural curve but i have a lot of curves so before doing it manually i need to know if there is a tool that refines the curves. Also i need to know if there is a better or proper way of doing the task.