Triangulation routines for roads and side objects are all written from the ground up. 
For irregular shaped meshes delaunay triangulation is used as a base.
The Internet has a wealth of information related to this including free to use libraries. 
Below are credits for the approach used in EasyRoads3D.

Credit to Paul Bourke (paul.bourke@uwa.edu.au) for the original Fortran 77 Program.
Check out: http://local.wasp.uwa.edu.au/~pbourke/ http://paulbourke.net/papers/triangulate/
You can use this code however you like providing the above credits remain in tact.
First converted to a standalone C# 2.0 library by Morten Nielsen (www.iter.dk)
Performance enhanced C# 2.0 library by Christian Stelzl Sep. 2008