The B480 is a long rural B-road in south Oxfordshire.
It starts on the A4130 at Lower Assendon, at the western end of the Fair Mile which leads out of Henley-on-Thames. At this point the road is signposted for local traffic only; anyone wanting to go beyond Stonor is directed via the B481.
The B480 goes north to Stonor and then heads north-westward. It reaches the B481 at a T-junction and turns right. The road descends steeply through Howe Wood before reaching the largest place on the road so far: Watlington. The B4009 comes in from the right and the B480 becomes the dominant partner in a short, 270-metre-long multiplex through the village, at the end of which the B480 TOTSOs right at a fork while the B4009 continues ahead. A small roundabout marks the end of the village and the B480 heads back into open country.
There is a sharp right-hand bend in the next village, Cuxham, before the road reaches Chalgrove. The original line of the road zigzagged through the village but now it runs along a bypass between the village centre and the airfield on its northern side. A mile beyond the end of the bypass the B480 comes to a mini-roundabout junction with the A329 on the green in Stadhampton. Here we turn left and follows a short multiplex through the village. At the far end it is the A329 which TOTSOs left, the B480 bending sharply to the right here and regaining its number.
The River Thame is soon crossed, and we immediately enter the hamlet of Chiselhampton, where there is a junction with the B4015 (number unsigned). The B480 continues northwestward across fairly featureless countryside. After negotiating a roundabout at the eastern edge of Blackbird Leys, a large housing estate, we cross the City of Oxford boundary and soon pass the Cowley motor works before coming to a larger roundabout and grade-separated junction with the Oxford Ring Road (here numbered A4142).
The B480 continues through the suburbs of Oxford for another couple of miles before ending at The Plain roundabout where it meets the A420 and A4158.
Originally the B480 ran only between Lower Assendon and Watlington, where it ended on the B4009. The section to Stadhampton was unclassified and from there to Oxford (where The Plain roundabout was the junction of the A40 and A42) the classified road was numbered B4014. The B480 was extended to Stadhampton in the late 1920s and then took over the entire route of the B4014 in 1935, giving the road its current length.