Autodesk CIVIL3D - CIVILDESIGNCOMP 2007 SLM CD Tutorials Manual page 607

relationship between the mass haul line and profile in the grade point
balancing method.
Balance Points
Balance points are the stations at which the net cut and fill volumes are equal.
In a mass haul diagram, the balance points are located on the balance line,
where the net volume is zero. In the balance points method of measuring free
haul, the mass haul line is duplicated and shifted horizontally to the right
(where the project transitions from cut to fill) or to the left (where the project
transitions from fill to cut) by the free haul distance.
In the following image, the green areas are free haul volume, and the red areas
are overhaul. The arrows illustrate the free haul distance in cut and fill
conditions.
Tutorial: Working with Mass Haul Diagrams | 595