The A4231 runs along the modern Barry Docks Link Road in south Wales.
The road starts at a roundabout on the A4050 in Pencoedtre, to the north of Barry, where that road bears right to take traffic towards either the town centre or Cardiff Airport. The A4231 follows a straight path through the wood before reaching a roundabout providing access to northern suburbs. The road now skirts the eastern edge of town although it never becomes built-up itself.
We descend through a cutting to reach a staggered crossroads, serving the town and a golf course. Continuing on, we go over the railway line before bearing round to the right to reach a roundabout on the A4055, which now takes on traffic heading for the docks. The A4231 ends here, with the road ahead the B4267.