Beginning at Fornost Erain in northern Eriador, it met with the Great East Road at Bree, and then continued south to Tharbad on the Gwathló, where it crossed the river and became known as the Old South Road. From there it lead into Dunland, arching slightly towards the Misty Mountains to the Fords of Isen. After it crossed the Isen it was called the Great West Road, and ran along the Ered Nimrais through Anórien, then going south past Minas Tirith and Osgiliath as the South Road and ending at Pelargir.
Other roads which met up with it were the King's Highway from Minas Tirith past Osgiliath to Minas Ithil, and at Pelargir the road which eventually ended at Erech as well as the Harad Road which lead 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.