At present, there is no native tool that will define the combined boundary and sharp change in level that a kerb presents in real life.
There are number of ways to model kerbs in Revit, the right one to use is the one that is quickest and provides an adequate representation.
SPLIT AND COMBINE TOPOSURFACES
Start with two topo surfaces at their correct height – here we have a basic road and grass combination.
Next, both surfaces need to be split along the edge they will adjoin using the Split Surface tool in the Site ribbon. The combined width of the two strips will need to represent the notional width of the kerb – i.e. if the kerb is 100mm wide, 50mm strips will need to be cut either side.
Now these two thin strips need to be merged using the merge surfaces tool. Note: the highest surface must be selected first to ensure the correct profile is created in the merge.
The merging creates a very basic splayed kerb profile – albeit showing only the exposed face.
WALL AS KERB
Model low walls as kerbs.
Refer to CREATE WALLS THAT FOLLOW SITE TOPOGRAPHY if you need the kerb to follow the toposurface.
USE AN ADD-IN
Refer to TOPOSURFACE TOOLS.