RTB goes to great lengths in order to blend road edges with the terrain. Materials are blended to form great looking transitions, angles are calculated for outside edge to consider the slope of the terrain and cross-section points are adjusted to account for the underlying terrain.
By default the edges of the tracks are calculated, shaped and lit to blend well with the surrounding terrain. This occurs in three ways, by using the terrain as the material for the edge and then blending it with the track's material, by adjusting the physical shape of the track to "meld" with the terrain and by adjusting the lighting so that abrupt angles are less visible.
The points of the road can be weighted to snap to the underlying terrain. This is used for regular roads to help blend the edges of the road with the surrounding ground, however this can also be applied to all points of the track which produces a beautiful effect. The road can be made to entirely flow with the terrain so any raising or lowering of the terrain that would normally sit underneath the road, will alter its appearance.
The image below shows a road that was moved slightly using just two clicks of the mouse. The rolling hills shape both the terrain and the track.