|Distance:||3.7 miles (6 km)|
|Met (1961):||A483, B4296, A484|
|Now part of:||B4620|
|Route outline (key)|
The A4070 linked the A483 (former A475) at Fforestfach with the A484 (former A48) to the east of Loughor Bridge. It was reclassified and became the B4620 in the 1990s following the construction of a new approach road to the Loughor Bridge (today's A484) which runs parallel to it.
Prior to the opening of the new A484 the A4070 left the A483 at the Carmarthen Road / Middle Road / Pontarddulais Road crossroads in Fforestfach. In order to deter rat running, there is no longer any motor vehicular access from the A483 to the B4620 at this point (the replacement junction is 700 m further northwest along Pontarddulais Road), although there is a buses-only exit from the former A4070 onto the A483.