Site Modifiers are used to modify the site model. There are a few tools that…
Vectorworks Tip #248 – Site Modelling – Site Modifiers – NURBS Road
The NURBS road is useful for creating a smooth, curving road. It is also very useful in that you can adjust the elevation of each station point. the other road types allow you to edit the start elevation and slope, but the NURBS road is more flexible when editing the elevations.