This problem gets raised a lot.
I have two measured or provided lines for a road pavement. I want to extend the pavement out XX’ to edge of new pavement at the slope between the two lines. The slope between the two lines varies along their length. In this case the user requested a second extension of 16.4’ at the same slope for the shoulder area and then also requested to drop the shoulder by 9" to get a subgrade model for the shoulder. Then they want the volumes for earthworks and subgrade quantities by station ranges etc. …
Video shows you how