|To:||Canaston Bridge (E) (SN070151)|
|Via:||Red Roses, Narberth, Robeston Wathen|
|Distance:||14.2 miles (22.9 km)|
|Meets:||A4066, B4328, B4315, A478, A40, A4075|
|Former Number(s):||A40, A4073|
|Old route now:||A40|
|Route outline (key)|
Beginning where the A4066 ends on the coast in Pendine, the road runs via Red Roses (where it goes over the A477 with no junction), Tavernspite, Princes Gate, and Narberth. On the approach to Narberth, a spur to the right passes near the railway station and continues north to meet the A478; the mainline, meanwhile, continues into Narberth itself, multiplexing with the A478 around the town's central one-way loop.
Setting off again northwestward, the B4313 meets the A40 at the eastern end of the Robeston Wathen bypass (constructed between 2009 and 2011), crossing over via a roundabout, and then continues along the pre-bypass of the A40 for a further couple of kilometres before rejoining the A40 just east of Canaston Bridge.
The B4314 originally ran from St Clears to Robeston Wathen along the present route of the A40. This state of affairs did not last long, however, since by 1932 the B4314 west of St Clears and the A40 northwest of Red Roses had swapped numbers – and the road from Pendine to Red Roses was added to the B4314's itinerary in 1935.
The spur at Narberth was originally numbered A4073, but was reclassified when the A40 and B4314 swapped numbers at the beginning of the 1930s.