The game might be a decade old, but I've recently got back into playing SC4 thanks to 2Gb of various mods and buildings.
Due to a combiation of absence playing the game for some time, and the new mods, I have been experimenting with ways of building settlements, including the implication of more realistic interchanges, tunnel methods (road under road), parks, and more organic street layouts.
The ultimate goal is to create a semi-realistic region with three large urban cores, dozens of periphery commuter settlements and various rural/agriculture-based communities amongst the hills.
For instance in one region tile, three neighbouring settlements are separated by natural formations. As would be the case in reality, these settlements are connected by a lengthy (but cheap) route that loops around the natural barriers. This also lends to the creation of a ferry system connecting the settlements around the bay.
The region is composed of 96 (12x8) large tiles, and I have only just scratched the surface.
(13mb version here:
http://i.minus.com/iHavdlRbrF5tS.png)