Create 3d element from 2d lines

Hi all. I have a bounch of 2 d lines running along a railtrack, that I would like to convert to a 3d element. I need to able to give the line some minimum bend radius, and also a minimum offset from a terrain model so I can ensure having a certain amount of cover, while not bending the element more than the minimum bend radius of 4 meters. I can't get my head around how I would create such rules, and apply them in order to create a 3d element that has a minimum of 0,5 meter cover and stays above the 4 meter radius. All must be created on behalf of the terrain model.