While poking around on RailBricks I came across a treasure trove of LDraw files for LEGO roads. LDraw is an open format for LEGO Computer Aided Design (CAD) software useful for designing and rendering models. This work is a superb example of on the Studs Not On Top (SNOT) building technique. It includes files all kinds of roads; straight, curved, rail crossings, turn lanes, cul-de-sacs, etc; in addition to intersections with traffic lights and roundabouts. These files allow you to literally inspect the designs brick-by-brick providing an insight into the engineering and design. Building them is made easier because parts lists can be exported and bricks gathered or procured.
I can’t imagine the amount of work that went into these models. If you use them make sure you credit GallagharsArt.com where you can find the LDraw files and download them yourself. Links to the LDraw files can be found in the forum links listed below.