You can model any combination of features on the surface of a mesh by using the Solid Element Operators; see tutorial of basic process here:
http://www.archicadwiki.com/TerrainRoadObjects
I had posted a similar technique a while ago (see thread here:
http://archicad-talk.graphisoft.com/viewtopic.php?t=30630&view=previous&sid=c2fd2f78881418c1ccb5a2fece080b9b
which is essentially the same but without the need to create object parts.