Ruts and Bumps

The overlay also has the ApplyOffset parameter.

If it is turned on, the road will change a little bit the terrain under the road: the elevations, ruts, and other types of unevenness will be added to it. The particular type of change in the terrain depends on the type of road.

By default, this option is enabled, if you turn it off - the road will become flatter.

When you change the value of this parameter, you need to perform the Rebuild Terrain operation to see the result.