The Network Addon Mod, or NAM, is a modification for SimCity 4 Deluxe (or SimCity 4 with the Rush Hour Expansion pack), which adds a myriad of new transport network items, ranging from ground light rail, to fractional-angle roads, to roundabouts, and much more. It also includes bugfixes to Maxis items and a highly optimized set of traffic simulator plugins, improving pathfinding accuracy and performance.
Perfect - just a little bit confusing with the road attachments - but all in all 10 out of 10. Kudos very enjoyable & decorative things you can do with this - makes my cities sparkle.