It begins in Port Talbot and heads up the Afan Valley in a north easterly direction.

It then continues over the moors eastwards until it connects with the A4061 road south west of Treorchy in the Rhondda Valley.

The A4107 starts at Port Talbot at traffic lights on the A48 road, the main route from Cardiff to Swansea before the M4 motorway was opened.

The road is climbing more steeply now and passes the Afan Forest Park to the right, before emerging onto grassy hillsides with boulders and rocky outcrops.

However, there were plans to extend it to provide opportunities for employment in a depressed area, and the Bwlch y Clawdd extension road was duly opened in February 1928.