For using GTire (Generic Tire), it allows the user to create GRoad before creating GTire. For references, the user cannot use GTire if there is no GRoad.
Figure 1 Road Data group in the Geometry tab [Body Edit Mode]
Before creating GRoad, the user must save the model because it is needed to set the local path of the *.rdf file which is saved in the GRoad. Therefore, if the user clicks Import GRoad or Face GRoad without saving the model, the following error message appears.
Figure 1 GRoad error message