Beginning at Fornost Erain in northern Eriador, it meets with the Great East Road at Bree, and then continues south to Tharbad on the Gwathló, where it crosses the river and becomes known as the Old South Road. From there it leads into Dunland, arching slightly towards the Ered Hithui to the Fords of Isen. After it crosses the Isen it is called the Great West Road, and runs along the Ered Nimrais through Anórien, then goes south past Minas Tirith and Osgiliath as the South Road and ends at Pelargir.
Other roads which meet up with it are the King's Highway from Minas Tirith past Osgiliath to Minas Ithil, and at Pelargir the road which eventually ends at Erech as well as the Harad Road which leads into South Harad.
The Greenway was long the main path of traffic between Gondor and Arnor, but in the later Third Age after the division of Arnor in three realms it became lesser used. Use of the road virtually ended after the Great Plague and Long Winter when Tharbad was abandoned and its bridge ruined, and the road in Dunland was mostly lost.