A465 Dowlais Top to Hirwaun Dualling

Scheme outline

Upgrade of the existing single three-lane A465 Heads of the Valleys Road between Dowlais Top and Hirwaun to provide a grade-separated dual two-lane expressway.

This scheme will be the final upgrade of the complete route from Abergavenny to Neath and will complete the continuous dual carriageway route between the A40 and M4 that has been progressively constructed since the mid-1970s.

The nine-mile section of single carriageway road to be upgraded is the final remaining section of route built in the early 1960s, and comprises the bypass around the north of Merthyr Tydful and an exposed section on high ground to the west of the town before the descent towards Hirwaun. It includes a significant number of major bridges and other structures, and passes through several built-up areas, so the widening works will be particularly complex.

Summer 2019 - 2022
In preparation
Other upgrade
for use by all traffic
Highway authority
Welsh Government


More information


With thanks to Matt Tovey for information on this page.