Attached Link: http://www.cornucopia3d.com/classroom.php

I have a tutorial at Cornucopia3D that might help you (see link, it's the one "Making of Sic Transit"). I talk about several different techniques.

Anyway, having a road on the ground plane as you plan is the most difficult way of doing it... The ground plane is too big and difficult to control. You're much better off with a small plane or a terrain.

There's also a recent similar thread in this forum (check it out) with a similar question.

Hope that helps.