On construction of the A48(M)Port Talbot bypass in the mid-1960s the old road was renumbered A4211.
The road started at the western end of the bypass which is now the roundabout at the end of the spur of M4J41. It headed southeastwards out of Baglan to go under the motorway and reach Port Talbot. After passing through the town centre it continued between the motorway and the railway line before merging in with the other end of the A48(M) at Groes Interchange, with the road ahead being the A48.
When the A48(M) was renumbered M4 in the mid-1970s the A48 got its old route back, thus making the A4211 number redundant.