From Roader's Digest: The SABRE Wiki
|To:||Junction with A492 east of Llangurig (SN916799)|
|Length:||0.5 miles (0.8 km)|
|Now part of:||A470|
|Route outline (key)|
The A4085 was originally allocated to a short link road between the A44 in Llangurig and the A492 half a mile east of town, with the A492 following the third side of the triangle to join the A44 further north.
In 1935 the A4085 became a spur of the A492, which was renumbered A470 in the 1970s. The parallel route which was the original line of the A492 was declassified and closed to through traffic in the 1980s, so the former A4085 has has become a major through route as the A470 mainline.