I need to recreate more realistic on and off ramps. I create a spline using the line tool and check of  “Enable In Render and Enable In Viewpoint” also use the Rectangular settings. This will give you a dimensional road exit and on ramp.

Cylindrical Control Envelope

After using the the scale tool to select edges and scale and flange the ramp apply a FFD(cyl) 4x6x4 modifier to create an envelop that you can use to make the ramp slop evenly and smooth. A difficult procedure if you try to move the verts independently and get a smooth gradual ramp. This makes it fast and easy.

menu FFD(cyl)4x6x4