|Length:||47.6 miles (76.6 km)|
|Meets:||A40, A4243, B4301, B4459, B4336, B4337, A482, B4578, B4577, B4575, A487|
|Old route now:||A484, B4301|
|Route outline (key)|
The route begins at a roundabout on the A40 to the east of Carmarthen on its way towards Llandeilo. Almost immediately, we meet the pre-bypass A485 (now A4243) heading north-east from the town. Soon we cross the River Gwili (Afon Gwili) and emerge in open countryside. We climb over the hills before descending to cross the river (which follows a much longer route) once again. Just before this, we meet the B4301, the original route of the A485 which reached here from Carmarthen via Bronwydd; the A485 was soon rerouted this way.
Our route is gradually turning north east, as we move towards the River Teifi, which we reach just before we get to Llanybydder, the biggest place reached so far! (It's not that big.) There, we cross the B4337, before running alongside the bed of a disused railway, and the River Teifi, for the last few miles to a T-junction with the A482 just south of the University town of Lampeter. We follow a short multiplex with the A482 through town past the east end of the A475, then turn right towards Tregaron. We pick a relatively easy course up the valley of a tributary of the Teifi, still shadowing the disused railway.
We pass more small villages – Betws Bledrws and Llangybi – before crossing back into the Teifi Valley at the site of the old Roman Fort of Bremia. A left turn here will take you onto the B4578, a Roman road (Sarn Helen) offering a more direct but steeper route towards Aberystwyth. Instead, we run on towards Tregaron, still following the Teifi and that railway line. Having passed through some hilly country, the land at Tregaron is relatively flat. We turn left in the town centre, onto a direct heading towards the coast and Aberystwyth.
At Tyncelyn we meet the other end of the B4578 Sarn Helen at a crossroads. We turn right here to head due north. Straight on is the B4577 which takes you towards Aberaeron.
Just south of Bronnant, the line of Sarn Helen heads off to the right. We continue northwards as we climb away from the rivers. The land to the west of Lledrod reaches an altitude of over 1,000 feet, but we avoid the worst of the exposure as we weave our way down to Lledrod itself, then up the other side of the valley. At Llanilar, we meet the B4575, where we turn left to shadow the course of the River Ystwyth, a sure sign that our journey is nearly over. We finish on the A487 at Llanfarian, a few miles south of the University town of Aberystwyth.