3d Modeling for Mainline AND Side Roads

I'm working on a 3d model for a mainline roadway with numerous side roads to produce a rendering using the 3d modeling tools in geopak V8i. The 3d model tools seem quite limited for this task, does anyone have a decent workflow to able to mesh/merge the 3d graphics from the side roads with the mainline 3d graphics? Or does anyone know of an easier workflow using Geopak Site to perform this task?

AHA,

Steve.

Geopak V08.11.07.615