The road crosses the top of the reservoir's dam before climbing away from the trees and onto exposed moor land to the west of the A470.

Leaving the park after passing through the small village of Penderyn, the road descends into Hirwaun, the first major destination on the southbound A4059.

[2][3] In October 2018, Cabinet Members allocated £1 million to a future scheme that would "extend the Aberdare Bypass and link the A4059 to the A465 Heads of the Valleys Road", which is also due to be improved.

[5] The proposed extension is part of a wider investment programme currently being undertaken by Rhondda Cynon Taf County Borough Council.

This project would connect key parts of Aberdare directly to the A465 at Croesbychan, which would reduce journey times and relieve Penywaun and Hirwaun of excessive traffic flow.