So you are digitizing the lines by snapping between known control points? Is that correct? Well, I would recommend the break lines for the crown of the road, edges, and the curb and gutter to create a better surface for contouring. I am not sure if I would just start creating the lines by snapping any control points together. To force the surface to model that as a line, be sure to specify the input as a hard line when creating the TIN or editing it.