The B4602 heads northeast out of Brecon town centre. Originally its southern end was numbered B4557 and the northern end A438 but the former became the A4062 in the 1960s and the remainder soon became part of an extension of the A470. The current number dates from reclassifications carried out following completion of the A40 Brecon bypass in 1980.
Starting at traffic lights on the B4601 relief road on the edge of Brecon town centre the B4602 heads northeast along Cerrigcochion Road. It climbs past the hospital into open country, levelling out before reaching a roundabout. Not long afterwards we reach a T-junction and TOTSO right; this is where the road number changed before 1980.
We now head east past a campsite, with the road running along the boundary of the Brecon Beacons National Park; the hills can be seen to the right. It's not long before the end of the road is reached at a T-junction on the A470.