Track change is taken as the lateral movement of the wheel base from a fixed point on the ground. Track changes are measured in millimetres and taken as positive if the wheel base moves outwards relative to the vehicle as shown in Figure. The calculation of track change is based on the following system variable:

 DY (WBid, FGid) - the Y-axis of the displacement of the wheel base marker relative to the fixed ground marker referenced to the Ground Reference Frame (GRF).

Figure. Calculation of track change

FGid: Fixed Ground Marker id.

WBid: Wheel Base Marker id.